title: Tests for alertness

text:
# Question
Title: Tests for alertness
Have there been any researched paper or digital tests developed that test a persons alertness at a given point in time? By alert I mean having the reactions of a person who is not over-tired, intoxicated, with a disability that inhibits reaction time, etc.

Edit:

I didn't see my answer in http://www.optalert.com/news/dr-johns-drowsiness-detection-technology-pharmaceutical-industry .

I am interested in a digital or paper test.

# Answer
TLDR version: PVT or the Mackworth clock test seems to have been most successful in the category of computer-based testing that doesn't require specialized (e.g. pupillometry) equipment. Mackworth's seems to lack standardization though.

The two tests also belong to different sub-categories, which highlights a need to refine the notion of alertness. PVT only "discriminates" against single class stimuli, only their timing is uncertain, so it's a detection task; the corresponding notion it supposedly measures been dubbed “intrinsic alertness” or “psychomotor vigilance”. Mackworth's discriminates between two classes of stimuli (i.e. it belongs to a wider go/no-go class of tasks); this is the typical/classical paradigm for “vigilance” testing. Since 2004, the term "vigilant attention" has been proposed to encompass both detection and discrimination tasks; it has gained some traction in the literature. The proponents/adopters of this new term argue that "vigilance", "alertness", "sustained attention", and "arousal" are/were not terribly well defined.

Subjective alertness (easily measured on a paper-based \[self\]-test) doesn't seem a good predictor of PVT (Phillips et al., 2016).

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The Mackworth clock test appears to be most sensitive based on Williamson and Feyer (2000):

> This study shows that commonly experienced levels of sleep deprivation depressed performance to a level equivalent to that produced by alcohol intoxication of at least a BAC of 0.05%. At the end of periods of waking of 17–19 hours, performance levels were low enough to be accepted in many countries as incompatible with safe driving. The earliest effects were seen for the Mackworth clock test and the latest for the dual task, although there was relatively little variation across tests. Longer periods of sleep deprivation were equivalent to higher alcohol doses for all tests except the grammatical reasoning and memory and search tasks. \[...\]
>
> As expected, increasing concentrations of alcohol produced significant reductions in performance for most tests and measures. \[...\] The results show that the extent of loss of function varies between tests although there were consistent effects within different types of measures. At a BAC of 0.05% for example, response speed decreased by around 8%–15% for reaction time, dual task, Mackworth vigilance, and symbol digit tests corresponding to a slowing of around 45, 66, 136, and 182 ms respectively. Hand-eye coordination measures showed a similar overall decrement of around 10% at this BAC. Measures of overall test accuracy also showed significant decrements due to alcohol, especially the number of missed signals in the reaction time test, which increased by 200%, and the number of false alarm responses in the Mackworth test, which were more than 50% higher at a BAC of 0.05%. The number of correct responses in the Mackworth test and length of the recalled series in the spatial memory task also both decreased by about 13% at a BAC of 0.05%. Subjective ratings of tiredness also showed a significant linear decrement of 77% by a BAC of 0.05%. Two tests, grammatical reasoning and memory and search tests showed very little decrease in performance at a BAC of 0.05%.
>
> \[Snip para about effect BAC of 0.1%\].
>
> These results show that alcohol does not exert universal effects on all functions and the pattern of effects also differs between them.
>
> Sleep deprivation also produced decrements in both performance and self rated alertness. As shown in table 5, sleep deprivation showed effects on a similar range of tests as did alcohol. \[...\] performance decrements occurred with increasing sleep deprivation for both speed and accuracy measures of the reaction time, dual task, tracking, and Mackworth tests and for the length of the recalled series for the spatial memory test. For example, between around 1900 and 0500 (corresponding to about 13–23 h sleep deprivation), reaction speed decreased by 57% for the Mackworth test, 9% for reaction time, 27% for dual task and 15% for symbol digit tests. Hand-eye coordination decreased by between 31% for the tracking component of the dual task and 26% for the tracking task alone. Accuracy also decreased markedly with sleep deprivation. The number of missed signals increased by more than 40% for the Mackworth test, by 187% for the reaction time test, and the number of false alarms increased by 200% for the Mackworth test. The symbol digit test only showed decrements for the speed measures but not the accuracy measure. The grammatical reasoning and memory and search tasks showed only relatively small decreases of around 5%–10% with increasing sleep loss for any measures.

Wikipedia shows a screenshot of a computerized version of the Mackworth clock, with this description:

> The Mackworth Clock is an experimental device used in the field of experimental psychology to study the effects of long term vigilance on the detection of signals. It was originally created by Norman Mackworth as an experimental simulation of long term monitoring by radar operators in the British Air Force during World War II. The device has a large black pointer in a large circular background like a clock. The pointer moves in short jumps like the second hand of an analog clock, approximately every second. At infrequent and irregular intervals, the hand makes a double jump, e.g. 12 times every 30 seconds. The task is to detect when the double jumps occur by pressing a button. Typically, Mackworth's participants would do this task for two hours.\[2\] The Mackworth Clock was used to establish one of the fundamental findings in the vigilance and sustained attention literature: the vigilance decrement, that is, signal detection accuracy decreases notably after 30 minutes on task. The test continues to be used today in vigilance research in various forms, including computer-displayed versions.\[3\]

What's missing from Williamson and Feyer is a more detailed description of their tests, including the length of Mackworth clock; since they measured it repeatedly, I suspect they took a lot less than two hours for each round.

In the press release you found, Optalert links to an earlier one claiming to be setting a (new) "gold standard" with their tech. But their tech requires eye-tracking goggles, so not quite fitting your simpler requirements. And it's far from being the only such product on the market, A 2014 review by Dawson et al. lists and evaluates (just based on publications, it's not head-to-head test) more than two dozen competitors for continuous monitoring and about half-dozen for spot fitness testing. For the latter category, which is closer to what you ask for, they give this summary:

I'll only quote you the part about PVT from the review because the next best candidate in that table (FIT) requires pupillometry:

> The psychomotor vigilance test assesses sustained attention and is currently the gold standard in fatigue detection. Individuals give a button-press response to visual stimuli on a computer screen over a 5- or 10-min period. Reaction time and ‘lapses’ (response time \>=500 ms) are measured. Several commercial versions of the PVT are available (e.g., PalmPVT, http://www.corware.com/Default.aspx; PVT-192: Ambulatory Monitoring, http://www.ambulatory-monitoring.com/pvt192.html). The PVT has consistently and reliably detected performance decrements resulting from sleep restriction, extended wakefulness or time-of-day effects across numerous industries, including rail, aviation, mining, and defence. Validation evidence is available for both the 5-min and 10-min versions. However, PVT performance may not equate to poor driving performance, perhaps due to large individual differences in driving performance. Thus the PVT may be better used to predict fatigue-related driving incidents as part of a broader test battery. This possibility may be explored further through research comparing the PVT with driving performance. Cut-off scores that predict impaired driving performance have also not been established. Despite its promise, until ‘fail’ or ‘warning’ levels are established, this device is unlikely to be useful for commercial drivers.

And if you're curios of conceptual comparison between PVT and Mackworth's, Douwel (2016) master thesis offers:

> To examine how attention is influenced during monotonous tasks, several vigilance tasks have been designed like the Psychomotor Vigilance Task (PVT; Lim & Dinges, 2008), the Continous Performance Task (CPT; Rosvold, Mirsky, Sarason, Bransome, & Beck, 1956) and the Mackworth Clock Test (Mackworth, 1948). Each task and its measures have their shortcomings and limitations. The PVT involves the detection of an unwarned stimulus to which participants have to respond as fast as possible. A limitation is that the response to the same signal is used, so no distinction is made between critical and non-critical stimuli. Therefore it measures only the readiness for speeded responding to unwarned stimulation (Langner & Eickhoff, 2013). The CPT and Mackworth Clock test involve discrimination between target stimuli and non-target stimuli. Both stimuli appear intermixed in a constant sequential stream consisting of regular intervals at a fixed rate. Participants need to respond to targets and withhold a response to non-targets over prolonged periods of time. In general, the stream consists of more non-targets than targets and only the targets occur infrequently and unpredictable. What it measures is a person's sustained and selective attention. Like the PVT, this can be derived from the speed of responses, but also from the number of detected and missed targets and the number of discrimination errors made. A shortcoming is that most visual discrimination tasks contain stimuli-events at a regular and high rate. This does not quite resemble real working environments in which the event-rate is at a slower pace and stimuli occur irregular. Another shortcoming is that performance on the task is retrospective which does not serve the purpose of preventing accidents from happening.

Lichstein (2010) notes a lack of standardization for Mackworth's (virtually every paper till then used a different variant).

CPT (mentioned by Douwel) seems to have given rise mostly to ADHD tests, thus not necessarily tests of temporary fatigue but more of a long-term impairment. (There might be some variant for fatigue that I don't know about.) For a factor structure of one variant CPT (which seems to include both a long-term impairment factors and short-term vigilance) see Egeland and Kovalik-Gran (2008).

Finally, for a more detailed discussion of the received terminology in the field see Oken et al., 2006, e.g.

> Alertness is another term that overlaps with arousal but more specifically includes some cognitive processing. Some researchers use the terms phasic and tonic alertness (Nebes and Brady, 1993; Posner and Petersen, 1990). Phasic alertness relates to the orienting response (Sokolov, 1963) and tonic alertness will be used synonymously to vigilance and sustained attention.
> 1 votes

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Tags: test, attention
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# Question
Title: Popular science books introducing therapeutic use of psychedelic drugs
I'm not a psychologist nor a psychiatrist, but I have the impression that research of therapeutic use of psychedelic drugs (MDMA, LSD, DMT, etc) is undergoing a revival and is very slowly being accepted by the medical establishment.

Are there introductory books covering this topic which are scientifically credible?

# Answer
> 7 votes
Yes, the psychedelic Renaissance/ third wave (as I've heard it being called) is steadily gaining momentum. I almost feel like mentioning How to Change Your Mind by Michael Pollan here is too obvious, but just to be safe, here's a few links and a cultural review. There is also an exhaustive summary on Trippingly.net!

# Answer
> 0 votes
Although there may be books written, your best bet for reading up on a changing field is to read some recent review articles.

Google Scholar is a good place to find such articles, for example you can search for "review psychedelic therapy" or substitute in a particular drug of interest. You can also select a recent year range if you want the newest sources.

https://scholar.google.com/scholar?as\_ylo=2014&q=review+psychedelic+therapy

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Tags: psychiatry, psychology, drugs, psychedelics
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# Question
Title: What determines whether sensitization or desensitization occurs?
I am familiar with desensitization. For example, if you are afraid of driving, driving every day will eventually reduce your fear, desensitizing you.

But today I came across another concept, that of sensitization. I looked up the wiki article on Sensitization, which says at the end,

> Sensitization may also contribute to psychological disorders such as post-traumatic stress disorder, panic anxiety and mood disorders.

So which is it then? What determines whether repeated exposure to something sensitizes someone or desensitizes them? With the example of PTSD, for instance, should not repeated exposure to war actually desensitize people?

I searched google scholar but could not find a paper that discusses both sensitization and desensitization. Mostly discuss the latter, in terms of reducing fears.

Appreciate any references or books that might help me understand this.

Thanks you.

# Answer
The terminology in this area can be a source of confusion because sensitization is not usually meant as the opposite of desensitization but of habituation. E.g., Blumstein (2016)

> People have written about habituation, a process that leads to decreased responsiveness to a stimulus, as well as its counterpart, sensitization, or an increased responsiveness to a stimulus, for over 2000 years.

So what's desensitization then? Well...

Systematic desensitization is basically an extinction procedure for (assumed) previously conditioned stimuli:

> Behavior therapy employs interventions based on classical and operant conditioning. An early example is Wolpe’s (1954) systematic desensitization in which patients are taught progressive relaxation techniques and then are systematically exposed to stimuli that elicit fear while in a relaxed state. Because the relaxation response is incompatible with anxiety, it weakens the learned association between a stimulus and an anxiety response.

And desensitization is often taken to mean the roughly the same as the systematic one, e.g. Clay (2007):

> Desensitization is generally described as a process by which the active pairing of a positive reinforcer with a negative event causes the negative event to slowly lose its ability to adversely influence behavior (Chance, P., 2003). This active process is also called counter-conditioning. Systematic desensitization has been used successfully to treat human phobias, such as fear of flying, fear of public speaking, and fear of spiders, and has also been used to reduce the intensity of Post-Traumatic Stress Disorder in veterans of the Vietnam War (Chance, P., 2003). For animals, a similarly competing response could be eating. Using competing responses to interfere with a fearful response is an integral part of the systematic desensitization process as defined by Wolpe (1958, as cited by Callen, E.J., & Boyd, T.L., 1990).

To add to this confusion, some mean by sensitization only the conditioned version, e.g.

> Sensitization occurs when a reaction to a stimulus causes an increased reaction to a second stimulus. It is essentially an exaggerated startle response and is often seen in trauma survivors.

But this is actually not that wrong, because unlike for habituation, it's hard to come up with many examples of *unconditioned* sensitization, e.g. what does Blumstein give (for both)?

> Habituation is a process that leads to decreased responsiveness to a stimulus with repeated presentation and is often adaptive in that it makes it less likely that individuals will respond to harmless stimuli. Found throughout the animal kingdom, some plants have also been shown to habituate (Jensen, Dill, & Cahill, 2011). However, habituation may also have consequences. Aesop recognized the consequences of habitation 2500 years ago when he noted that the boy who cried wolf would ultimately be ignored when he needed help to fend off a real wolf.
>
> Habituation's counterpart is sensitization--the increased responsiveness to a stimulus with repeated presentation. Sensitization may be adaptive if it helps animals avoid potentially risky or costly situations. Being sensitized to the sound of bees may help elephants avoid getting their sensitive trunks stung (sensu King, Douglas-Hamilton, & Vollrath, 2007), and may help allergic humans avoid an anaphylactic reaction. But it too may be costly. For instance, while drug addiction is usually thought to involve some degree of tolerance to drugs, indeed, it also involves sensitized responses that can be used diagnostically because greater salience is attached to the drugs and drug-associated cues (Steketee & Kalivas, 2011). Living without risk is impossible (Sagarin et al., 2010), and the public may become sensitized to real or manufactured threats repeated by the press (e.g. consider the U.S. government assertions that Iraq had weapons of mass destruction, or the American response to Ebola cases being treated in the United States in September--November 2014). Over-reacting to risk can lead to costly foreign policy mis-steps and costly public health responses.

Somewhat more interesting examples are given by Çevik (2014)

> The signal value of a stimulus is correlated with its potential to support responsiveness, which for a given set of physical parameters depends largely on the history of non-associative learning, i.e., habituation and sensitization for the stimulus. Habituation refers to the reduction in the probability or amplitude of responding that is observed upon inconsequential stimulus repetition. For example, repeated delivery of an odor at constant inter-stimulus-intervals (ISI) would eventually lead to the habituation of the response that is initially triggered by the odor. I say eventually, because depending on the parameters of the stimulation protocol (e.g., odor concentration, frequency of odor presentation), a temporary increment in responsiveness might initially be observed. If, however, an appetitive gustatory stimulus (e.g., sugar) is repeated with the same ISI, depending again on the concentration of sugar, frequency of stimulation, and the physiological state of the organism, this protocol is likely to result in an increment in the probability of responding, i.e., sensitization. Finally if odor and sugar are paired instead of being presented separately, the standard paradigm for Pavlovian conditioning would ensue, where the two stimuli would now be termed conditioned (CS) and unconditioned stimuli (US), respectively. Hence, associative learning can be suggested to entail an evasion from habituation for the CS as it signals the arrival of a sensitizing event, the US, and a conditioned response (CR) would then be triggered during the CS in anticipation of the US.

And he actually proposes some general rules:

> habituation might be the default fate for most stimuli in the absence of top-down modulation (although see Horn and Hinde, 1970 for examples of non-habituating reflexes). \[...\]
>
> the likelihood of habituation, i.e., the inability of a perceivable stimulus to control behavior is higher for distal stimuli, whereas the likelihood of sensitization is higher for stimuli that come into direct contact with the body to activate gustatory and/or mechanoreceptors.

Although his rules are derived from research on flies.

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The wiki sensitization page you mention doesn't talk of PTSD as far as I can tell.

From what I know of PTSD research in this area, it involves conditioned stimuli, e.g. a fairly cited paper in this line, Orr et al.:

> Differential conditioning was assessed in 15 medication-free individuals meeting Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) criteria for chronic posttraumatic stress disorder (PTSD) and 18 trauma-exposed individuals who never developed PTSD (non-PTSD). Conditioned stimuli (CSs) were colored circles, and the unconditioned stimulus was a "highly annoying" electrical stimulus. Individuals with PTSD had higher resting heart rate (HR) and skin conductance (SC) levels and produced larger SC orienting responses. During conditioning, the PTSD group showed larger differential SC, HR, and electromyogram responses to the reinforced vs. nonreinforced stimuli (CS+ vs. CS-) compared with the non-PTSD group. Only PTSD participants continued to show differential SC responses to CS+ vs. CS- during extinction trials. Results suggest that individuals with PTSD have higher sympathetic nervous system arousal at the time of conditioning and are more conditionable than trauma-exposed individuals without PTSD.

In that paper, PTSD patients were harder to de-condition or "desensitize" to use your terminology (see the sentence about extinction in the abstract I quoted above); PTSD patients also showed increased responses (compared to controls) to conditioned stimuli after conditioning took place, although as far as I can tell they were not easier to "sensitize"/condition, at least in that experiment.

The interaction between conditioned and unconditioned exposures to a stressful stimulus is fairly complex (even in animal \[models\]) and assumed to be of importance in PTSD. It's been known for a long time (Rescorla, 1974) that giving stronger unconditioned footshocks to rats increases their conditioned response to moderate footshock. So this is a kind of sensitization when conditional and unconditional effects interact. A more recent line of work on this interaction:

> Rats presented with a single session of repeated painful footshocks normally express a robust and persistent associative fear of the training context (Gale et al., 2004; Poulos et al., 2009), whereas subsequent new fear learning to a single footshock of the same intensity becomes sensitized to a newly trained context or a tone (Rau et al., 2005). We call this phenomenon stress-enhanced fear learning (SEFL). Pharmacologically induced (NMDA antagonism) and naturally occurring (preweaned pups) amnesia of the repeated footshock context fail to disrupt this sensitized fear learning (Rau et al., 2005; Long & Fanselow, 2012; Poulos et al., 2013). These results suggest that prior exposure to a repeated footshock stress, independent of a contextual fear memory, enhances subsequent fear learning when footshock intensity is held constant. Further evidence that stress influences future learning and does not produce its effect by generalization between the stress and conditioning contexts is that SEFL only occurs when the stress occurs prior to the one-trial fear conditioning (Rau et al., 2005). \[...\]
>
> SEFL would be a particularly problematic component of posttrauma behavior if intense stress results in substantial fear conditioning under conditions that would not normally support conditioning. Therefore, we determined if SEFL occurred when the conditioning shock was substantially milder than the SEFL-inducing shock. The results indicate that exposure to a sensitizing regimen of shock can convert a mild footshock that normally does not support measurable levels of fear conditioning into one that causes substantial learned fear. Moreover, as the intensity of single footshock increases, so does the capacity of the prior stressor to contribute to the sensitization of fear responses.
> 4 votes

# Answer
# Introduction to my answer

The subject of PTSD and its triggers is huge, and this answer is not an alternative, but **an addition** to @Fizz's good answer to this question.

The causes of PTSD @Fizz talked about are through prolonged timeframes of trauma (sensitisation through fear conditioning coming into play over a long period of time). This can involve soldiers who have been in combat situations whereby they have constantly witnessed attrocities, but not necessarily.

PTSD can also occur with hypersensitisation caused by a single instance of an initial sensitising event (ISE), again such as a particular event in combat, or through other physical violence with perceived or actual threat to life or physical wellbeing.

Desensitisation will be the process involved to resolve the hypersensitisation effects caused by the ISE and subsequent neurological and biological reactions to the ISE.

## So to your question in summary

> What determines whether repeated exposure to something sensitizes someone or desensitizes them?

Sensitisation doesn't just involve trauma leading to fear, but it can involve an ISE, or prolonged exposure to situations which leads to **any irrational emotion**. Disgust is one other example.

Desensitisation is the complete opposite. Desensitisation is where an event, or series of events, lowers inhibition towards something which would normally raise feelings of fear, disgust etc.

# More detail on what I am talking about

## Examples of single instances of ISE

Take a soldier in combat who is under constant heavy gunfire and "hell is raining down on everyone around them". Fellow soldiers in their troops are killed in the process, and **maybe** they have come close themselves. **Maybe** they have lost a limb from a mortar bomb explosion. This can be one ISE which on its own causes PTSD.

Take a man/woman who is threatened with their life and raped at knife/gunpoint. Again, this ISE alone can cause PTSD.

## Initial Sensitising Events (ISEs)

The science behind ISEs is as follows

> As a therapist I consider not only the how the memory (or gestalt) was encoded during a Initial Sensitizing Event (ISE), but what effect that the event had and has on the person both physiologically and mentally. If the event is traumatic enough to cause stress, the fight and flight defense mechanism will lead to increased cortisol flow, IL-6 fluctuations, and eventual adrenal fatigue. Mentally/Neurologically, dominant "brain maps" may be created, which perpetuate an overactive anterior cingulate (ACG), result in a continual looping (such as in PSTD) and create further mental dysfunction as the ACG will compete for energy resources (hemoglobin and oxygen, specifically).

Let's have a breakdown of what was said in the quote

### The fight and flight mechanism

A more in depth rundown on this (what I call the 5F response — fright/flight/fight/freeze/fawn) can be found in my answer to Understanding fear as a response in classical conditioning, but in short, the 5F response is an unconscious reflex to **perceived** threats, initiated from **Threat → Brain Receiving Signals → Brain Reacts (Fright) → Cortisol and Adrenaline is released → Physical Reactions occur from the release of hormones → Bodily response (Fight, Flight, Freeze or Fawn)**

(Source: Wikipedia)

### Adrenaline and Cortisol Release

As you can see within the infographic above, the brain initially processes the threat signal in the amygdala and then the hypothalamus and the pituitary gland secretes adrenocortictropic hormone (ACTH) which leads to cortisol and adrenaline release to enable a speedy escape if chosen.

### IL-6 (Interleukin 6) fluctuations

Based on the Wikipedia link I provided, the epigenetic effects of IL-6 have been implicated in the pathology of depression. The effects of IL-6 on depression are mediated through the repression of brain-derived neurotrophic factor (BDNF) expression in the brain; DNMT1 (DNA (cytosine-5)-methyltransferase 1) hypermethylates the BDNF promoter and reduces BDNF levels (Sharma, et al. 2008). Altered BDNF function has been implicated in depression (Hwang, et al. 2006), which is likely due to epigenetic modification following IL-6 upregulation (Sharma, et al. 2008).

### The Anterior Cingulate Cortex (ACG)

The ACG is responsible for detecting incongruences between expectation and perceived experience (Somerville, et al. 2006). Altered connectivity of the anterior cingulate cortex in depression, therefore, may cause altered emotions following certain experiences, leading to depressive reactions (Somerville, et al. 2006). This altered connectivity is mediated by IL-6 and its effect on epigenetic regulation of BDNF (Sharma, et al. 2008).

## Desensitisation

This will be a slow process. As @Fizz quoted,

> Desensitization is generally described as a process by which the active pairing of a positive reinforcer with a negative event causes the negative event to slowly lose its ability to adversely influence behavior (Chance, P., 2003).

also called counter-conditioning.

Desensitisation for PTSD whether caused through trauma over prolonged timeframes or one single instance of ISE, can be obtained through therapy of many different types. Therapy may also be supported through medication to alleviate symptoms such as anxiety and depression.

CBT has been the go-to form of therapy within services linked to the program called Improving Access to Psychological Therapies (IAPT), but it does have its limitations. Whatever method of therapy is employed (CBT, REBT, Person Centred Therapy...), the therapy at some point will have to enable the person who is suffering from PTSD to re-evaluate their perceptions of what constitutes a threat to their personal safety.

Initially, they will have to look at what startles them (what are their triggers), evaluate where those triggers came from and look at how they can form rational thought patterns when they arise again.

Take for example, a veteran of war. When carying out routine patrols of hostile areas, they will have had to have a constant awareness of their surroundings, assessing who or what could consitute a threat. Once they are suffering the severe effects of war, they could have a hightened sense of alertness which carries forward into civilian life at home outside of war. If there is a sound of a car backfiring, in extreme cases, this can lead to a sudden reaction which can leave that person feeling very vulnerable.

This war veteran will need to be able to immediately determine that they are not in a hostile situation and in fact the loud bang was just a car backfiring (desensitising against loud bangs to a safe and rational level). It is likely that these situations (loud bangs) will not be the only trigger, and the others will need identifying and resolving.

## References

Chance, P. (2003). *Learning and behavior*, Fifth Edition. CA:Wadsworth Publishing.

Hwang, J. P., Tsai, S. J., Hong, C. J., Yang, C. H., Lirng, J. F., & Yang, Y. M. (2006). The Val66Met polymorphism of the brain-derived neurotrophic-factor gene is associated with geriatric depression. *Neurobiology of aging*, 27(12), 1834-1837. doi: 10.1016/j.neurobiolaging.2005.10.013

Sharma, R. P., Tun, N., & Grayson, D. R. (2008). Depolarization induces downregulation of DNMT1 and DNMT3 in primary cortical cultures. *Epigenetics*, 3(2), 74-80. doi: 10.4161/epi.3.2.6103

Somerville, L. H., Heatherton, T. F., & Kelley, W. M. (2006). Anterior cingulate cortex responds differentially to expectancy violation and social rejection. *Nature neuroscience*, 9(8), 1007. doi: 10.1038/nn1728
> 0 votes

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Tags: learning, anxiety, fear
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# Question
Title: Why do people bid on online auctions sooner than a few seconds before it ends?
This is something that has always puzzled me about human behavior on online auction platforms. I am talking about a specific platform where you can sell almost any item you want with a starting bid and a fixed time until the auction ends. People then can place a bid at any time, thus increasing the current price. The current price is always last bid + 0.5 currency. When the auction ends the highest bidder gets the item for the current price, with a percentage going to the platform. E.g. if the starting bid is 1 currency and someone bids 50 currency, the price is at 1.5 currency, until someone else places another bid, e.g. 20 currency, which would push the price to 20.50 currency, with the first bidder still being in the lead.

And that's exactly the crux. No one except the highest bidder knows what the highest bid is. People tend to place a bid, see it's not high enough and then increase their own bid in small currency steps, often going beyond what they originally were willing to pay. Also anyone who bids early risks that someone else tries to bid more than them, while when they bid late that chance is reduced, especially because there isn't any time for anyone to bid again.

For the platform this is good. For sellers this is good. For buyers, not so much. It's super irrational. They just drive the price up by bidding.

If buyers would just wait till a few seconds before the auction ends, and then place exactly the highest amount they are willing to pay, the item would sell for less, and they wouldn't be drawn into a bidding war that escalates the amount they are willing to pay. Even if it slightly decreases their chance of getting the item, unless it's a super rare thing there are so many items from different sellers, it would still be rational to behave this way until they succeed on one of the items. If unsuccessful too often, they could then conciously decide to increase the amount they are willing to pay - to adjust to the market price, not escalate in a bidding war.

Of course the platform wouldn't profit as much then, but I doubt buyers behave this way out of charity for them. So the question is: **Why are people behaving this way?** Are they really not aware of this? Do they not care? Is bidding to them just *fun*? Is this in some way related to gambling?

(I have asked this same question a few years ago on a Q&A in my native language, and the unanimous answer was: *"Bidding is how that platform works, you obviously don't understand it,"* which leads me to believe that the answer is *people really are not aware,* but I don't get *why not*.)

I have been selling items on a particular platform for over a decade and absolutely profited from this irrational behavior, but at the same time I am so confused by my fellow humans.

# Answer
One advantage of auctions, to the seller, is that buyers can get caught up in bidding wars and spend more than they intended to. Any auction platform that gets paid by what the auction takes in is going to want or hope for that.

I assume you're referring to eBay-style auctions. eBay encourages bidding frenzies. If you bid on an item and are outbid, they will notify you and encourage you to bid more. As the auction draws to a close, they will notify bidders who aren't currently in the lead. They're hoping at least some bidders will think bidding is fun, and will think of winning the auction as succeeding. The thrill may be that of gambling or similar.

I don't see any advantage in waiting for the last few seconds. I decide how much I'm willing to pay for something, and enter that amount whenever. The only way someone will find out how much I bid is to outbid me, and then I don't want to win the auction. Trying to time my bid for the end of the auction would sometimes be very inconvenient. If there's going to be a bidding frenzy at the end, the price will either go over mine or not, and I think it very unlikely that when I bid makes much difference in that. It should be clear that I don't think bidding by itself is fun, and that I don't want to win the auction by paying more for an item than I value it, which as you've seen isn't the universal approach.
> 1 votes

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Tags: bias, decision-making, behavior
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title: Differentiations of Imposter Syndrome

text:
# Question
Title: Differentiations of Imposter Syndrome
How can Imposter Syndrome be differentiated from actually possessing its symptoms? For example, one of the symptoms is the feeling that the person does not possesses extra intelligence, but that they have tricked their peers into such false perceptions.

Perhaps either one is true, either they posses special skills in scamming the public, so to say. Or they have imposter syndrome, but how can one truly know? Especially after coming across the fact that descriptions of such states exist.

In short, how do we differentiate *imposter syndrome* from \[one who feels like\] an actual *imposter*?

Please comment for clarifications

# Answer
It sounds like two measurements are needed:

1) *Perception of competence*. This could be measured using self-report for large studies, or semi-structured interviews for individuals or small samples. For example, individuals could use semantic differential scales to rate global or specific aspects of quality at characteristics or tasks that are key to that activity.

2) *Objective measurement of competence*. This will be specific to the domain. I work in science, and there are increasing (although flawed) metrics to measure quality such as the H-index for publishing impact. One could also use a basket of other measures, and they could include subjective input like peer ratings. Similar studies have been run in personality psychology.

In an individual, it would be difficult to know whether an observed difference between 1) and 2) is meaningful (e.g., not due to chance). This would be easier in populations, where two distributions could be compared using a method like correlation.

On a less methodological note, many beliefs about the self are not strictly accurate. A general summary is that most beliefs about the self are MORE positive than they should be: https://en.wikipedia.org/wiki/Illusory\_superiority However, people seem to underrate their abilities for rare tasks: https://en.wikipedia.org/wiki/Worse-than-average\_effect

The original post mentioned scamming others into a belief. Keep in mind that some qualities don't have precise scientific content, or are defined in a huge amount of conflicting ways (e.g., "leadership"), and so it would be difficult to objectively verify. That is, the imposter syndrome will be easier to verify for specific, concrete tasks and well-studied abilities (including intelligence).
> 3 votes

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Tags: philosophy-of-mind
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# Question
Title: Is eye movement important with eyes-closed EMDR therapy?
Original EMDR therapy involved a subject with open eyes tracking a target that moves side to side.

It is now common for EMDR to use devices like electronic "tappers" to alternately stimulate the left and right sides of the subject's body, leaving the subject free to close his eyes and engage in visualizations related to the trauma being treated.

In general, during wakeful visualizations with my eyes closed I often move my eyes in a manner similar to REM sleep. I have tried a few sessions of EMDR and found it to be uncannily effective. During closed-eye EMDR I sometimes find myself engaging in REM based on my visualizations, and other times find my eyes moving side to side in synchrony with the "tappers."

My question: Are there any studies or theories that suggest eye movement in closed-eye EMDR is relevant to the efficacy of the therapy? E.g., does it matter whether the closed eyes move side to side if there is some other bilateral stimulation?

# Answer
> 1 votes
The state of the art in EMDR research (if not yet in practice) supports a "working memory" (WM) explanation of the therapy that does not support earlier "bilateral stimulation" hypotheses of the method. A particularly salient summary from M.A. van den Hout et al. in *Behaviour Research and Therapy* 49 (2011) p.93:

> Traditionally, during EMDR, eyes are moved horizontally. In line with the WM account, but in contrast to original explanations, moving eyes vertically is equally effective (Gunter & Bodner, 2008). Crucially, the same effects occur if WM is taxed during recall with non-eye-movement secondary tasks, like listening to a series of non-words (auditory shadowing; Gunter & Bodner, 2008), drawing a complex figure (Gunter & Bodner, 2008), or counting (Engelhard, van den Hout, & Smeets, 2011; van den Hout et al., 2010; Kemps & Tiggemann, 2007). Tasks that are presumably hardly taxing, like simple finger tapping, do not have beneficial effects (van den Hout et al., 2001), while more complex tapping does (Andrade et al., 1997). Likewise, activating memories about a previously seen trauma film while playing taxing computer game reduced flashbacks in the week afterwards (Holmes, James, Coode-Bate, & Deeprose, 2009).

This was backed up by correspondence with one of the authors who confirmed that in all their research protocols going back to at least 2000 research subjects *must* keep their eyes open so the researchers can confirm compliance. They have no evidence this reduces the effectiveness. In fact, the WM model suggests this should *improve* the effectiveness of the therapy vs. allowing subjects to close their eyes.

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Tags: therapy
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title: Why can't we learn what we don't like?

text:
# Question
Title: Why can't we learn what we don't like?
The school system as we know it, is & has been shaping students to fit the system which they live in and throughout this process, the students are forced to learn(mostly memorize) subjects which they do not have any interest in whatsoever and because of this they can't score high in school. It is as if our brains are trying to avoid information, which is out of interest, as much as possible. But when there's something in interest it is damn easy to collect and comprehend that information.

Let's assume that you are a programmer and you are greatly amazed by that, you love solving problems and develop software, you read lots of documentations and contribute on other peoples projects without even having to worry about "remembering" what you're reading, everything is easily understood and there's no issue with that. But when you have to learn about politics and how the system works, it appears as cancer to your eyes because you have no interest in it, there's no will to collect that information and therefore you score low in that subject.

now my question is: **Why can't we learn what we don't like? (what we're not interested in?)**

# Answer
> 3 votes
# 1

There is some relation between what we are interested in and what we are good at. If people are bad at something, they usually lose interest in it and turn to other things. If you are good at something, you enjoy doing it and are *interested* in it.

Interest, therefore, is a preditor of ability, and you are better at learning things that you can do, than you are at learning things that you cannot learn to do.

# 2

Learning requires time, attention, and effort. If you are interested in something, you will (want to) spend more time, attention, and effort on it. If you aren't interested in something, you'll find every minute of it unpleasant, so you will limit the time you spend with it, not be as attentive, and not labour as hard.

You will also not think about it while you are not learning, you won't connect it to other interests and activities, and so on. In short, you won't *elaborate*.

There is a psychological theory, the elaboration likelihood model, that says that the processing of information will be more superficial when the motivation to process the information is low.

# 3

Doing something interesting is pleasurable, and everything in your mind and body works better if you are in a good mood. Hormones such as oxytocin, whose levels are higher when you are "happy" (and free of negative stress), have a positive effect on memory formation and retention.

# Answer
> 1 votes
Its all in the experience. Lets say we are studying 6 subjects in school, there is a high chance that we are going to dislike some of them. No one excels in everything they come across. Its a blessing in disguise if you think about it. Its a way for our minds to filter what comes natural to us and what doesn't. I for one can totally relate with your example. Our mind is just not that good at working hard. When we are doing something that we love, we are not actually "working" or "trying". We just do it hours after hours and keep indulging in that activity days after days, just because it feels natural and our mind doesn't have to work that hard on it. Past experience makes a huge difference too.

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Tags: learning, brain
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# Question
Title: What is the most robust method for peer grading?
I intend to provide a group task for 30 people, split into 5 or 6 groups.

Ultimately, I want them to assess which group delivered the best result (after presenting results in front of other groups) as well as grade themselves within groups based on their contribution to the team effort.

Now, both game theory and my simple experience of observing people being unobjective would suggest there are plenty of ways this can go wrong if I don’t introduce some robust system that would deal, at least, with problems like:

* group likely to be second will give lowest grade to group they see as objectively the best so that they boost their chances of winning
* group likely to be the last will give lowest grades to second to last group so that they boost their chances to replace them and not finish last
* group members will tell me each person contributed to the same extent, but it will be untrue in most scenarios. Especially the best group has no reason to lower the grade of their colleague no matter how marginal his contribution had been. On the other hand, system where they score each other with percentage contribution is also wrong as sometimes indeed all group members collaborated on the same, high level and there is no need to point best or worst performing members and lower their grades, thus even if they all worked hard they would get the same, median mark for their performance.

Does such a voting/grading system exist?

# Answer
In order to incentivize the desired behavior for your first point, you can do the following.

* If the group that comes out second, gave the lowest (possible) grade to the group that came out first, the punishment is at follows `<specify punishment here>`. An alternative condition would be: If the first group received the lowest grading from the second group. This is more stricter, but also fairer. Maybe add some tolerance (e.g. 1 grade divergence is okay).

You could try the same strategy for the second point, but that won't work. If the groups can't vote for themselves (as a group) and if we assume that the end result is a somewhat objective representation of the performance, the last group would give the second to last group the lowest grade. You could try the alternative of the first approach, though:

* If the last group received, the worst grade from the second to last group and if that grade diverges by more than 1, then `<specify punishment here>`.

In fact, you could introduce this rule for all the ranks. First and second place, second and third, etc. But the groups would need more time then, also this assumes the performances of the groups vary to such extent that it is indeed possible to subjectively rank them.

In order to have the groups assess them themselves, you could introduce a finite number of grades or classifications (e.g. top performer, medium performer). If the grades/classification can only be awarded a fixed amount of times, each participant will have a unique rank (relative to that group). The grade will probably not compare to group members of other groups (maybe if you weigh it with the group grade). It is possible to limit the number of possible grades to number of group members, or limit it to 2 or 3 (top, medium, bottom) and have multiple grading rounds.
> 1 votes

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Tags: social-psychology, methodology, game-theory
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# Question
Title: Psychology Research, Questionnaire Help Needed
I am Computer Science student and studying Psychology as an elective. Now I was required to conduct a research on any topic. I chose: Negative Effects of Permissive Parenting Style on Youth of Pakistan. I am having difficulty in making Questionnaire (since I have very little experience about it). I want your expertise to know which approach is better. I have following two approaches of making questionnaire.

First Approach:

Topic: Negative Effects of Permissive Parenting Style on Youth of Pakistan

1-Do you think that permissive parenting style has negative effects on Pakistani youth?

2-Would you like to adopt permissive parenting style if you happen to become a parent?

3-Do you think that permissive parenting is one of the reasons that Pakistani youth lacks self-discipline?

4-Do you think that the element of not listening to anyone, in Pakistani youth is because of their brought up by permissive parents?

5-Do you think that students of universities in Pakistan do not perform well in academics because they are not afraid of their parents' reaction on getting failed?

6-Do you think that parents should be friendly enough, so that their children do not hesitate to share any problem?

7-Do you think that in Pakistan, permissive parenting should be encouraged?

8-Do you think that blurred line between parents and children leads to domestic conflicts?

9-Do you think that children become creative in a restriction free environment?

10-Do you think that permissive parenting makes relationship with children conflict-free?

11-Do you think that youth of Pakistan do not abide by rules because they are not enforced by any rule under the permissive environment?

12-Do you think that, in Pakistan, drugs is more often among the youngesters having permissive parents?

13-Do you think that the parents being soft spoken, builds strong emotional understanding in children?

14-Do you think that under permissive environment, children will lack decision-making skills?

15-Do you think that friendly environment in home teaches children social skills?

Second Approach: What do you think about the following statements?

⦁ Your parent really expect you to follow family rules.

⦁ Your parent try to know where you go at night.

⦁ Your parent know exactly where you are most afternoons after school.

⦁ When your parent tell you to do something, they expect you to do it immediately without any question.

⦁ Your parent get very upset if you try to disagree with them.

⦁ It is a bad idea to question authority.

⦁ A person must have clear long term goals.

⦁ You would rather do something beside studying during extra time.

⦁ If you like something, you want to have it no matter what.

⦁ You have a healthy diet.

In the first approach, direct questions with binary options are given.

In the second approach, first 5 questions are used to depict whether the subject is permissive or not. Next five questions are used to know what are the effects on permissive parenting.

# Answer
> 2 votes
You said in your comments

> my goal of research is to figure out actual possible effects. In second approach, effects are being tried to figure out from the audience. While in first approach, direct questions mentioning effects with binary options are asked. I think in that case, second approach is better. What would you have chosen?

Opinion-based questions are off-topic here as we require questions which can be answered based on science rather than what individuals *think* is correct.

In order to answer your question without opinion being involved, I am going to have to reflect it back to you in order for you to be able to determine the best approach **for your needs**.

First of all, you need to ask yourself

> How can I work out the possible effects of permissive parenting via a questionnaire?

Once you have your answer to that question you are almost there on deciding how your are going to approach the questions within the questionnaire.

If you look at the questions in the first approach, with the exception of question 2, they all start with

> Do you think....?

These questions are looking for your audiences opinion on permissive parenting. You need to ask yourself if you can gain knowledge of the **actual** effects of permissive parenting from these questions. If you can, then great. Go down that route and devise a list of questions which can give you the results. If not, then look at another approach.

Your second approach looks at what kind of parenting your audience may have had and then looks at their opinion on a range of things. Will their opinion-based answers in the second half give you what you need to determine the possible effects of the parenting style they were brought up on? If so, then that is the approach you need with your questionnaire.

# Answer
> 2 votes
Questionnaries are usually created in the following way:

1. Experts come up with a series of questions based on their expert familiarity with the area they want to study (e.g. a group of therapists with long years of treating depressed persons sit together and consider which questions best reflect the symptoms their patients have shown), based on theories of the area (e.g. theories of what depressions is and how it affects those that suffer from it), and based on existing instruments (e.g. other questionnaires or measurements of depression.
2. The questions are then presented to a test group (e.g. patients with depression and healthy persons) and the results are compared to the results from existing measurements, to see how they compare.
3. A principal component analysis and other statistical analyses are conducted to find out whether some of the questions measure exactly the same aspect and can be deleted, whether it is a unified construct or consists of several subscales, and so on.
4. The questionnaire is revised according to the results of the test runs and a representative sample of the population is tested to create norms.
5. The test is published and applied by other experts and reviews are published. Criticism is incorporated in revised editions.

# tl;dr

It is impossible for anyone to say which of your two approaches is better without testing your questionnaire and verifying whether it measures what it is supposed to measure, e.g. by comparing results to those from existing instruments.

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Tags: behavior
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# Question
Title: How does the brain create original thoughts?
Since the generation of thoughts requires the coordination of various parts of the brain, how does the brain know which parts to activate to develop unique ideas? Does the brain randomly activate its various regions until it happens upon a unique thought?

Is the creation of unique, original, and creative ideas a function of the brain alone, or does the brain require an outside stimulus to engender creative or unique thinking?

There are many instances of great thinkers arriving at groundbreaking ideas from mere observation of nature and society. For example, Einstein developed his equivalence principle by thinking about elevators (mundane, everyday machines).

So, in summary, does the brain need outside stimulation to think imaginatively, and how does the brain coordinate its different parts to generate unique ideas?

# Answer
To understand how the brain "knows" what to do, we can look at how children learn language.

At first, children randomly create all kinds of sounds, including those that aren't part of the language(s) spoken in their environment. Parents and other people react to these sounds, repeating them, speaking their language, smiling, etc., and the children in turn react to these reactions to their sounds, learning which sound elicit which reactions (e.g. which sounds lead to a smile, which sounds are ignored, etc.), until they slowly begin to build a repertoire of sound and "pre-words" which give the most pleasurable results.

With time, children learn to recognize parts of the language spoken in their environment and begin to emulate these sounds, learning their first words, and eventually to speak.

So what we have here is a brain creating random behavior (in this case with the speaking apparatus), and learning from the effects this behavior elicits in the environment which behavior leads to the desired results. Whatever happens in the brain when a desired result is achieved, is stored as the "internal behavior of the brain" to do to achive that result, e.g. what to say to get that ball.
> 0 votes

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Tags: brain, creativity
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# Question
Title: What's the difference between flaws of character and a personality disorder?
Okay, I have read this question and 2 answers and I don't believe these are the same questions. It's not about legal status or the moral appropriateness of punishment by society. And it's not about the neural basis of volition (and how that can get messed up, physically), I don't think.

It's more like why isn't some personality disorder (like narcissistic or borderline) simply considered a character flaw? Like: that narcissist is arrogant and conceited and brags because he wants to be and likes it. Or: that borderline is demanding and manipulative and hateful because she wants to be and it serves her. So that is the first question.

The second question is how to relate with these troubled persons? When does one hold the other personally accountable for their decisions and actions and when does one go into treatment mode as a caregiver would a patient or a dependent loved one? Caregiver is flawed human being with their own issues and not professional in any field related to psychology or mental health.

But, outside the domain of the law and criminal responsibility, how should a regular "civilian" or "layperson" relate to persons (immediate family, extended family, coworker, friend or acquaintance) with NPD or BPD? When should a person treat the NPD or BPD as a selfish asshole (with moral judgement and sometimes disdain) and when as a sick or weak person that is perhaps just very needy (and/or difficult)?

# Answer
A personality flaw can be a trait or behaviour that is conscious and the person usually has control over it, whereas a personality disorder is a long enduring pattern of defensive behavior that lies outside of the persons control, because they are not are not aware of it. A person with Borderline Personality Disorder will use splitting and projection to discharge bad feelings within themselves by seeing others as bad, uncaring or mean. While other times they will cling to relationships when the project the are good and loving. A personality disorder consists of a long enduring pattern of behaviour, whereby the person has a distorted image of themselves and others, causing interpersonal difficutlites, which they have no conscious awareness about. A flaw means you can do something about it and it is less self-debilitating.

https://www.counsellingservicemelbourne.com.au/personality-disorder-treatment/

www.counsellinginperth.com.au/personality-disorders/

https://www.counsellingservicemelbourne.com.au/
> 5 votes

# Answer
There is a clear definition of what a personality disorder is. The Wikipedia article on Personality Disorders lists the criteria given in the DSM-5 and ICD-10. Take a look: https://en.wikipedia.org/wiki/Personality\_disorder

If you don't understand those definitions, please edit your question accordingly.
> 5 votes

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Tags: personality-disorder, moral-psychology
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# Question
Title: Reading material for graduate neuroscience program
I have just finished reading 'Neuroscience: Exploring the Brain' 3rd Edition, Bear et al. I am also planning on pursuing a neuroscience degree beginning fall 2019 and was wondering what other reading material I could use in preparation for such a degree. More specifically, I'm interested in computational neuroscience. What series of books is recommended to read for someone in my situation?

# Answer
> 1 votes
It's a rapidly developing field, so that some areas are incredibly well represented in the books to the point of being standard - like the neuronal dynamics (e.g. by Paninski, Naud, Kistner, Gerstner or e.g. by Izhikevich), some less, like neural coding (e.g. by Doia, Ishii, Pouget, Rao) and vision (e.g. by Rolls, Deco), some almost aren't, like motor control(?) or neuroanatomy(?), and some has yet to generate sufficient volume of theoretical work explaining experimental data (before it can start condensating in textbooks), like. Maybe try

Trappenberg - Fundamentals of Computational Neuroscience 2ed

It's pedagogically sound, yet not exhaustive nor particularly long to get through. This will help to have an initial overview of some topics, and build some taste for further reading interest (as the book really tries hard to give you a primer on a variety of topics and methods, and gives references). It has some code examples that you may rewrite in you favorite language. In addition, you may benefit from free browsing of Scholarpedia for reviews written by active researchers, and form your own idea of what "Computational Neuroscience" is.

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Tags: neuroscience, reference-request
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# Question
Title: How to differentiate attentiveness, arousal and memory via gamma oscillations
I am planning an experiment using mice with in vivo extracellular recordings (and maybe also optogenetic stimulation). In these kinds of experiments, the mouse is getting a reward after executing a (short term) memory involved task.

I noticed that in the papers I read, it is not really possible to know if the observed $\gamma$-oscillations (for instance), derive from memory activation, or arousal (from thinking of the reward), or from attentiveness (from trying to execute the task correctly).

Are there any ideas or a good reference for this problem of distinguishing between these related cognitive activities?

Examples of experiments with humans will also help. Maybe not directly but will give some ideas about how these notions can be separated.

# Answer
You'd need to "shut down arousal" to give a causal dissociation of arousal and memory reactivation, right?

*E.g.* https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3174240/

Then you'd need to define what do you mean by "memory activation", physiologically, and record there simultaneously with the above. This will introduce additional difficulty in a mouse due to its small size, -- depending on where do you want to record when looking for "memory activation".

However, you may try using a simpler to implement EEG screw to get the oscillations https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5802558/

But the above link is for a rat, and you'd have to confirm in the literature that you can get the gamma through an EEG screw in a mouse. Also consider that in conjunction with your search for the area where you want to record the gamma. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5333145/

which itself is tied to the experimental design (task) that captures "memory activation".

During training, and for validation you may employ a proxy for arousal in a form of pupil dilation. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3612940/ There you again need to confirm if someone has successfully used this measure in a mouse (the link is for humans, and it's possible in rats too).
> 3 votes

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Tags: cognitive-psychology, neuroscience, cognitive-neuroscience, neurophysiology, animal-cognition
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title: How does neuron stimulation work?

text:
# Question
Title: How does neuron stimulation work?
Neurons are excited via an external electrode by passing current through it. A neuron at rest is at -70 mV, it needs additional charge amounting to around 15 mV to initiate an action potential. But the external electrode only gives electrons, which are negatively charged, how can they increase the potential inside the neuron? Does the electrode provide charge to the outside of the membrane of the neuron?

# Answer
> 1 votes
The electric field of an external electrode provokes the opening of sodium channels, which in turn has the effect that the positive charged sodium ions travel into the cell body and invoke the wanted change to the Membran potential…

reference: Simulation Neuronaler Netze \[("Simulation of Neural Networks")\] / Andreas Zell. - Bonn; Paris; Reading, Mass \[u.a.\]: Addison-Wesley, 1994, first edition

# Answer
> -1 votes
The current in the cells is ionic, and the electron motion is negligible. Yes, the increase of membrane potential to the specific threshold causes changes in the channels, which causes a spike. Let's look in more detail how to get to that threshold, before which the channels are closed.

In depolarization, the membrane potential is increased, where membrane potential is a difference between voltage inside the cell and the voltage outside the cell (let's follow this convention). In the simplest case of extracellular DC microstimulation with a monopolar cathode, this would be a result of a decrease of extracellular voltage, and an increase of intracellular voltage.

The passing current on the electrode is negative, this decreases the (extracellular) voltage, but with having less decrease further away from the electrode tip. Thus, it depends on a distance to the cell - if the cell is too far, then the current may identically affect both extracellular and intracellular voltages, without sufficiently affecting their difference.

With the closer distance, however, we should also consider the resistance of the membrane. If it's so large that intracellular voltage is not directly affected by the current, we would still get different extracellular voltages at different sides around the cell (because voltage change is distance dependant as mentioned above, and the cell might be also sufficiently big). At different parts of membrane, the extracellular voltage would be different, but intracellular stay the same. The membrane will attempt to equilibrate, and increase it's intracellular voltage to average out the membrane potential that was made different at different sides by current application.

On the other hand, with little membrane resistance, both the extracellular and intracellular voltages will change almost identically without needed affect on their difference.

Thus for a given current and a given distance(and a given cell size), we need "the right" membrane resistance so that the change provided by the current application is different extracellularly vs intracellularly. There should be a spatial gradient in extracellular voltage, but also a smaller spatial gradient in intracellular voltage. Then one part of membrane would be be depolarized, and another - hyperpolarized.

If there is little gradient in intracellular voltage, even if with significant gradient in extracellular voltage, the resulting membrane potential will not be sufficiently different across membrane. Since in practice we can control the current, and not the membrane size, resistance and distance to it - we want control for not having too much current (otherwise we'll have too little intracellular gradient because of current flow through the cell plasma), and not too little current (because of lack of current flow due to high resistance).

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Tags: neuroscience, neurophysiology
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# Question
Title: Recording motor-evoked potentials (MEPs) in response to transcranial direct current stimulation (tDCS)?
The amplitudes of motor-evoked potentials (MEPs) are often recorded as a measure of (change in) cortical excitability, after administering some form of non-invasive brain stimulation (NIBS). In a typical scenario, magnetic stimulation (TMS) is used to deliver pulses to the motor cortex, and MEPs are recorded from e.g. the index finger.

It has never been clear to me why MEPs can not also be recorded in response to other forms of NIBS that also modulate cortical excitability, most notably electrical stimulation (tDCS). This paper seems to state this axiomatically, without really giving a reason:

> Compared with tDCS, TMS provides a better spatial resolution; when used over the motor cortex, it also allows the quantiﬁcation of motor-evoked potentials (MEPs), a measure of the excitability of the motor system, which tDCS does not.

Any thoughts as to why it is that MEPs are not also prompted by tDCS?

# Answer
Compared to TMS which is usually brief and high-intensity, tDCS stimulation protocols are fairly weak and long-duration. This protocol doesn't elicit MEPs by itself, because you need a stronger stimulus.

In some studies (see references below), tDCS has been shown to modulate MEPs, but it is probed by using TMS to elicit the MEP, and comparing the evoked MEPs with and without tDCS.

The mechanistic idea is that tDCS is modulating neuronal thresholds, but you still need some sort of a "kick" to actually evoke a MEP.

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Nitsche, M. A., & Paulus, W. (2000). Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. The Journal of physiology, 527(3), 633-639.

Nitsche, M. A., & Paulus, W. (2001). Sustained excitability elevations induced by transcranial DC motor cortex stimulation in humans. Neurology, 57(10), 1899-1901.

Nitsche, M. A., Fricke, K., Henschke, U., Schlitterlau, A., Liebetanz, D., Lang, N., ... & Paulus, W. (2003). Pharmacological modulation of cortical excitability shifts induced by transcranial direct current stimulation in humans. The Journal of physiology, 553(1), 293-301.
> 2 votes

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Tags: motor, tdcs, tms
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# Question
Title: How is the term "physiological measurement" defined?
Does the measurement have to be subconscious?

Can measurement such as eye-tracking be counted as physiological measurement? (I thought it is because of its relatively subconscious nature until I saw this.)

# Answer
Physiology is a very broad term that includes neuroscience:

> Physiology is the scientific study of the functions and mechanisms which work within a living system.

Within the cognitive sciences, physiology typically refers to non-behavioral inputs and outputs of the nervous system (including parts of the brain), but physiological measures may include behavior:

> Physiological responses also can be measured via instruments that read bodily events such as heart rate change, electrodermal activity (EDA), muscle tension, and cardiac output. Many indices are part of modern psychophysiology, including brain waves (electroencephalography, EEG), fMRI (functional magnetic resonance imaging), electrodermal activity (a standardized term encompassing skin conductance response, SCR, and galvanic skin response, GSR), cardiovascular measures (heart rate, HR; beats per minute, BPM; heart rate variability, HRV; vasomotor activity), muscle activity (electromyography, EMG), electrogastrogram (EGG) changes in pupil diameter with thought and emotion (pupillometry), **eye movements, recorded via the electro-oculogram (EOG) and direction-of-gaze methods**, and cardiodynamics, recorded via impedance cardiography.
> 3 votes

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Tags: physiology, experiment-design
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# Question
Title: If reality is just hallucination, how come different people see same objects
I wanted to ask this question for a long time but couldnt find any thing to support my argument. Today i found this https://www.ted.com/talk/anil\_seth\_how\_your\_brain\_hallucinates\_your\_conscious\_reality#t-694887, where the speaker Anil seth theoretize that our reality is just a hallucination. Exchange of information happens both ways inside and outside, i.e, we not only perceive the world around us but also actively generates it.

Perception is an active constructive process. To summarise,

Hallucination is uncontrolled perception, then Perception is controlled hallucination.

My question is, If thats the case then how two people would agree on the same state of world?

# Answer
According to `Anil Seth`, in this talk, consciousness is an active construction process. In that view, for the subject to have an experience about world, physical signals from mind independent objects are processed by brain and a highly probabilistic mental content of the physical is experienced. Even though I mentioned objects, it could be material things and features.

But our sensory abilities are not inherently cable of perceiving everything. The range of vision is `360-400 to 760-830nm`. Similarly, for audition its `20Hz to 20,000Hz`. There are other phenomena like aftereffects and adaptations, which too work along with perception. The information thus processed by sensory faculty is further compared with prior data that is stored in the brain and brain tries to come up with a decent construction of mind-independent objects. This experience can be called a controlled hallucination as there are other possibilities for such construction.

The general organization and working pattern of typically developing humans brains are very similar, especially in the early processing of sensory signals. Similarly, the physical signals that it processes of mind-independent objects are also very similar. Given these two, it is highly likely that two people have similar experience, even though we cannot confirm it and can only say that we share a human like experience.

Reference:
> 4 votes

# Answer
Additionally, active construction of reality doesn't mean there are basic objective reality. Usually our mind uses similar mechanisms to understand this basic reality. our byological makeup, psychological processes and broad social context provides us basic assumptions, and other tools to understand what is going on in the world. usually what we perceive is outcome of our interpertation of that basic reality by byological psychological, social tools. We might see world differently Because of our byological, psychological social differences. However, those differences are not so big that we can not understand each other.
Referenses: Burr, V. (2006). An introduction to social constructionism. Routledge. Raskin, J. D. (2002). Constructivism in psychology: Personal construct psychology, radical constructivism, and social constructionism. American communication journal, 5(3), 1-25.
> 2 votes

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Tags: cognitive-neuroscience, consciousness
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title: Unknown unit/mL

text:
# Question
Title: Unknown unit/mL
In the book Kaplan and Sadock's synopsis of psychiatry:

> Clozapine. Clozapine (Clozaril) levels are trough levels determined in the morning before administration of the morning dose of medication. A therapeutic range for clozapine has not been established; however, a level of 100 mg/mL is widely considered to be the minimum therapeutic threshold. At least 350 mg/mL of clozapine is considered to be necessary to achieve therapeutic response in patients with refractory schizophrenia. The likelihood of seizures and other side effects increases with clozapine levels greater than 1,200 mg/mL or doses greater than 600 mg per day or both. Clozapine is a common cause of a leukopenia in psychiatry. When moderate to severe leucopenia develops, clozapine treatment must be interrupted, but patients may be retreated with clozapine in the future.

What is "mL" here?

<sub> Sadock, B. J., & Sadock, V. A. (2011). Kaplan and Sadock's synopsis of psychiatry: Behavioral sciences/clinical psychiatry. Lippincott Williams & Wilkins. </sub>

# Answer
(edit, actually found the book text on Google books and paid a bit more attention to the context; the book is Kaplan & Sadock's Concise Textbook of Clinical Psychiatry by Sadock, Sadock, and Ruiz, and you can find the specific passage by searching for the quoted text)

This book is talking about plasma concentrations of drugs. Based on the actual plasma concentrations for clozapine with typical doses, this looks like just an error or typo: mL means milliliters, but these numbers would be more appropriate if they were in *nanograms* rather than milligrams, milligrams is several orders of magnitude too high and well beyond the solubility of clozapine in water.
> 2 votes

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Tags: psychiatry, psychopharmacology, schizophrenia, pharmacopsychiatry
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# Question
Title: What are “Stimulus locked” and “Response locked” in Philiastides & Sajda (2006)
While going through the below-mentioned paper, I came across some plots which were said to be "locked" with reference to either *response* or *stimulus*. Does the locking refer to the initiation of the measurement with starting cue being the presentation of the stimulus or the response of the subject?

**References**

* Philiastides, M. G., & Sajda, P. (2006). Neural Representation of Task Difficulty and Decision Making during Perceptual Categorization: A Timing Diagram

# Answer
> 11 votes
> Does the locking refer to the initiation of the measurement with starting cue being being the presentation of stimulus or the response of the subject?

More or less, yes.

When measuring brain activity, you usually make a long, continuous recording during which you expose your study participants to a task over and over again. There's a lot of noise in the recordings, so you need to average over many instances of a stimulus/task event to get an idea of what it does to the brain. To average, you need to cut the recording into trials (also called epochs).

You need to decide what to base these epochs on, i.e. what to cut around. Stimulus-locked measurements happen when you cut an epoch relative to the stimulus onset. The average over all trials will then give you a good impression of the sensory response to the stimulus.

However, there are some higher order cognitive processes going on as well, and they will happen at different speeds over trials and over different subjects, so they will smear out in the average. If you want to look at these, it's wiser to do response-locked measurements, i.e. to cut the epochs around the moment that the study participant responded to the task. This way, just prior to the button press (in the plot), you might get to see some evidence-accumulation or similar cognitive process going on. You can also see the motor response very well.

# Answer
> 2 votes
I wanted to comment on @Ana answer but I don't have the reputation. I wanted to add to her answer by adding that if you are doing a literature review on this topic the terms target-locked, stimulus-locked and cue-locked are often used interchangeably. Example of components that are extracted from this form of locking is the N2 and P3. Whereas the two most common response-locked ERP components are the ERN (Gehring et al 1993) and Pe.

I also wanted to add that the majority of EEG systems (such as the dense array electroencephalographs from EGI) will take very precise measurements on when the stimulus is presented. Ergo, depending on the component you are trying to evaluate you will lock to either the stimulus or the response. When these programs get out of sync it can be an absolute nightmare to find the source of the minute error.

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Tags: measurement, terminology, methodology, decision-making
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# Question
Title: Will Our Brain Speed Reduce As Our Memory "Mail Boxes" Fill Up?
I recently stumbled accross the article "When the Brain's Mailbox Is Full", which can be found here: http://www.nytimes.com/1999/07/27/health/when-the-brain-s-mailbox-is-full.html.

The article claims that:

> ''As we get older, we run out of places to store new information,'' said Dr. H. Lee Swanson, a psychologist at the University of California at Riverside and the author of the study. ''We have a limited amount of space in our memory system.''

Do we really have a such a limited capacity for knowledge that we risk slowing down our brain functions if we study too much?

> Swanson, H. L. (1999). What develops in working memory? A life span perspective. Developmental psychology, 35(4), 986. LINK

# Answer
> 10 votes
As Chuck pointed out in the comments, it's important not to take a metaphor too literally. Comparing our memory to a mailbox may have some validity, it is not true that our memory can "fill up"-- i.e., that we have a limited capacity for knowledge in general. No matter how old or how many facts you have learned, you will always be capable of learning new ones.

In the NYT article, prominent aging research Timothy Salthouse points out this research is controversial:

> "It seems unlikely that any single study, regardless of its quality, will be able to resolve the issue. We don't know how to measure storage capacity."

Additionally, your question asks whether we risk "slowing down our brain functions" if we *study too much*. This study is about *age-related deficits*, and there is no evidence that simply learning more information will reduce our memory capacity.

The study also is referring only to *working memory*, and not *long-term memory*. While some researchers believe working memory is simply a subset of attended items in long-term memory (e.g. Cowan, 1999; Anderson J.R. et al., 2004), others believe they are unique constructs (e.g. Baddeley, 2000). It is important not to conflate the two.

While learning new facts cannot reduce our overall memory capacity, it may affect our ability to retrieve specific items. This is known as memory inhibition. For instance, recalling semantically related words can inhibit retrieval of a target word (Anderson, M.C. et al., 1994).

In sum, learning new information *may* prevent us from retrieving older information through inhibition, but it is not related to overall memory capacity, or to the age-related deficits mentioned in the NYT article. We don't risk "slowing down our brain functions" by studying too much.

> Anderson, M. C., Bjork, R. A., & Bjork, E. L. (1994). Remembering can cause forgetting: retrieval dynamics in long-term memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20(5), 1063. PDF
>
> Anderson, J. R., Bothell, D., Byrne, M. D., Douglass, S., Lebiere, C., & Qin, Y. (2004). An integrated theory of the mind. Psychological review, 111(4), 1036. PDF
>
> Cowan, N. (1999). An embedded-processes model of working memory.Models of working memory: Mechanisms of active maintenance and executive control, 62-101. PDF

# Answer
> 4 votes
There is strong evidence that suggests there are changes in neural pathways, synapses, and even birth of new neurons due to changes in behavior, environment and neural processes. That is known as Neuroplasticity, which suggests that our brain's capacity can be "recycled" and even augmented in many cases.

If I had to choose a metaphor to make an analogy of our brain compared to something else, I would say it is more like a muscle or a bone. They have limitations regarding their capabilities, but they can change to fit demand.

# Answer
> 3 votes
There is research showing that Black Cab taxi drivers while training with 'the knowledge' (2 months on a moped with an A-Z, learning every road/route in London) grew larger areas of brain grey matter concerned with memory. Therefore it cannot be fixed and fillable, neuroplasticity will grow more where required. Although this is not the reference I was referring to above, it is on the same lines. https://onlinelibrary.wiley.com/doi/abs/10.1002/hipo.20233

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Tags: memory, long-term-memory, working-memory
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# Question
Title: When did the old term experimental reagent become experimental subject?
I've read a paper on an experiment called "The Feeling of Being Stared at", which investigates a concept which on Wikipedia is called the psychic staring effect. It was first investigated by psychologist Edward B. Titchener in 1898.

The paper consistently refers to the experimental subjects as "reagents".

> "In some of the experiments, the distance between the experimenter and reagent was varied for the purpose of..."
> Page 3 of 6

I'm unfamiliar with this term to refer to subjects, and I assume it's because this is an old paper from 1913. My guess would be that the word means something or something that reacts, and subjects are subjected to stimuli. Is anyone familiar with this term being used generally in experiments around this time period or even today? And if so, when it fell out of fashion and replaced with what we use now: "subject".

# Answer
> 3 votes
Psychological theory has often metaphorically used terminology from the technology or science of its time.

Freud explains certain aspects of the psyche in terms of the steam engine, and psychologists of the late 20th century think of the brain in terms of computer science.

In your case Titchener and other psychologists of his time tried to grasp psychology in terms of chemistry: "a reagent is a substance which, because it has a capacity for certain reactions, is used to detect, examine, or measure other substances" (Schultz, 2013, p. 88). Historians of psychology assess this term as evidence for the mechanistic view inherent in the structuralist approach to psychology. For Titchener, the human proband is a *recording instrument* (Schultz, 2013, p. 88).

As psychology as a science has shifted to a new paradigm in the early 20th century, the term *reagent* slowly fell out of use. The latest use in a psychological context that I'm aware of is in the late 1920s.

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Sources:

* Schultz, D. (2013). *A History of Modern Psychology* (2nd ed). New York: Academic Press.

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Tags: experimental-psychology
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# Question
Title: Is it fair to categorize the neurons in the output layer of artificial neural networks as grandmother cells?
I'm interested in how memory is distributed in the brain. That inevitably leads one to think about grandmother cells.

Under my interpretation, a neuron (or a small ensemble) would classify as a grandmother cell, if it activates, without fail, whenever a specific stimulus is presented to a subject, over an extended period of time.

To my knowledge, there is no evidence for the existence of such neurons, except some experiments that show the activation of specific neurons for a short period of time between trial sessions. The last part is important, because to my understanding grandmother cells are explicitly about long term memory.

If I look at most artificial neural networks however, the cells in the output layer usually exactly fit this definition. You can easily train a network to recognize pictures of your grandmother and consistently find the exact same cells active during evaluation whenever such a picture is presented. That's important for a computer of course, because it needs to have a consistent way of telling something is learned.

This would be an important difference to the brain though, because one could argue that any system, involving grandmother cells and that has only a limited number of cells, eventually suffers from overfitting or at least very limited generality.

Is this assessment fair? Is my definition wrong, somehow? Did I miss some evidence?

# Answer
> 4 votes
I would say it depends on what your goals are and what parts of the grandmother cell "story" you want to highlight.

**Sure, the output layer is grandmother-like because it can represent single concepts**

If you are writing a classifier to identify objects, then in some ways, yes, the outputs of an ANN reflect "grandmother" cells in that they represent a single output concept/object. The way that a hypothetical grandmother cell in a real nervous system would be activated (as sort of a final step after perceiving all the sensory information seeing/hearing another person presents) would be analogous to how the output of an ANN is chosen.

However, the outputs of a real nervous system are probably better identified as the motor plans: the goal in object recognition is to decide whether to fight or flee or do nothing at all. Similarly, if your ANN is trying to classify radiological images as "cancer" or "no cancer" these outputs don't really fit with the idea of a grandmother cell.

**But no, the grandmother cell is about more than that and the output layer of an ANN doesn't really fit**

A key element in the grandmother cell concept is that this cell is somehow connected to all the other subconcepts that make up the grandmother concept: the sound of her voice, the color of her hair, where she lives, etc. In real nervous systems these elements probably involve large ensembles of neurons organized into attractor networks, but even so, because the output layer of an ANN is just that, an output layer, it's really missing the major feature that makes a grandmother cell so key in the first place.

The studies you refer to that showed some evidence of grandmother-like cells are really just demonstrating a certain level of sparseness such that within a limited subset of experimental stimuli, those units were only activated by one or two of the inputs. In an ANN, these types of nodes would be better represented as units in some hidden layer. If I were to look for "grandmother cell-like behavior" to make comparisons between a real brain and an ANN, I would look for sparseness in the hidden layers rather than pointing to the output.

**Summary**

In summary, I would say that you could refer to grandmother cells in discussing ANN behavior, but I would be careful about taking the analogy too far or to assume that something true for a grandmother cell must therefore be true for a certain element of an ANN. However, I don't see a lot of value in doing so, and if I were teaching a course on the topic, I think I would avoid the comparison to avoid misinterpretation or confusion among the students.

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Connor, C. E. (2005). Neuroscience: Friends and grandmothers. Nature, 435(7045), 1036.

Gross, C. G. (2002). Genealogy of the “grandmother cell”. The Neuroscientist, 8(5), 512-518.

Kreiman, G., Koch, C., & Fried, I. (2000). Category-specific visual responses of single neurons in the human medial temporal lobe. Nature neuroscience, 3(9), 946.

Quiroga, R. Q., Reddy, L., Kreiman, G., Koch, C., & Fried, I. (2005). Invariant visual representation by single neurons in the human brain. Nature, 435(7045), 1102.

Quian Quiroga, R., & Kreiman, G. (2010). Postscript: About grandmother cells and Jennifer Aniston neurons.

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Tags: memory, long-term-memory, artificial-intelligence
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# Question
Title: Is "not going to doctor because of fear of illness" a psychological disorder?
Some people don't like to go to the doctor because they are afraid of being diagnosed sick in medical examinations or being diagnosed exacerbated when they have an illness even they know if they don't treat the illness it will get worse.

A really large population of these kind of people exists, especially in Asia.

Is it a subtype of hypochondria? Or it is another psychological abnormality or even is normal?

# Answer
What you are describing is most likely **avoidance**, which in itself isn't a disorder.

People are most likely afraid of the illness in itself, and so not going to the doctor means that they don't have to confront the possibility of having that illness. This avoidance is a *mechanism* that maintains hypochondria or health anxiety (however you wish to call it) by *negative reinforcement*: 'I don't go to the doctor, I'm not told if I'm sick or not, so I'm less anxious'.

The reduction in fear or anxiety is usually short lived and only makes it worst over time. This coping mechanism is not adaptive, and may aggravate health anxiety, but in itself, is not a disorder.

<sub>**Sources**
**-** David Veale's website
**-** Centre for Clinical Interventions
**-** Psychology Today</sub>
> 8 votes

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Tags: abnormal-psychology, fear
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# Question
Title: Early foreign language experience and ease of learning foreign languages
I've been wondering recently about the factors that affect the process of learning foreign languages. Specifically, whether early contact and experiences with a foreign language can have any impact on the ease of learning a foreign language later in life.

I know that I am cable of learning foreign languages faster than others (not everyone, of course) and, on the other hand, I find it quite difficult to learning programming or math. What I am wondering about is whether this is because I started learning English when I was 8 years old and whether, at that young age, I was able to work out certain mechanisms or ways of copying and handling this kind of knowledge.

Psychologists would probably say that some people have certain capabilities and others don't, which makes us so unique. What I would like to know is if there is any scientific way to prove/refute a relationship between early language experience with the ease of learning a language.

# Answer
> 7 votes
This is an interesting question. Language development is a fascinating topic!

There are two types of language learning:
1. Learning a natural language (a language that is learned without any conscious effort) https://en.wikipedia.org/wiki/Natural\_language
2. Learning a second-language

Nearly all babies learn a natural language and some may learn more than one (they are what we call, bilingual babies).

There are some critical periods for learning any languages and these vary depending on the aspects of language one looks at (syntax, semantics, etc...). (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3451048/)

Recent research shows that the approximate critical period for learning a second language appears to be at around 17 years old. (https://www.sciencedirect.com/science/article/pii/S0010027718300994) This does NOT mean that you will not be able to learn a second language after this, simply that it will be harder. Hence why it might have been easier for you to learn English at 8 years-old.

Now, depending on what languages you speak, it might be easier to learn some languages rather than others. For example, French and Spanish have very similar rhythms, phonemes, and are both romance languages, which would make it easier to learn one or the other, as long as you were fluent in one of them. However, it would be much harder for an English or French speaking person to learn Mandarin, because this tonal language is so different on many different aspects (for one, there are phonemes to which speakers of non-tonal languages are not sensitive, meaning that they cannot tell the difference between them). So yes, sometimes a language can be easy to learn, but at other times, it becomes much more complicated than having to learn a computer language.

As for being better at learning languages because you are bilingual, that is a possibility, but again, within the limits mentioned above of the language you decide to learn. Someone who knows French and Spanish may find it very easy to learn Italian, but still extremely hard to learn Cantonese. (https://www.psychologytoday.com/us/blog/life-bilingual/201506/can-second-language-help-you-learn-third)

Finally, psychologists do not agree on whether or not we have 'certain capabilities'. Many argue that anybody can become anything with the proper training and experience. Sure, as we grow, we become better in certain things, but you may find that by overcoming your preconceived ideas about yourself (ex: you are not good at learning computer languages), you can learn new things! I recommend reading *Peak* by Anders Ericsson. In his book, he really highlights how all the 'experts' were not born with special talents, but learned everything thanks to deliberate practice.

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Tags: cognitive-psychology, language-processing
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# Question
Title: Why does cathodal tDCS (negative) produce sensation, while anodal tDCS (positive) does not?
If neurons fire due to an intracellular influx of positive ions, why are the negative electrodes in tDCS felt more strongly than the others? For example, see "Reducing Procedural Pain and Discomfort Associated with Transcranial Direct Current Stimulation" by McFadden et al.

# Answer
**Short answer**
The underlying mechanism(s) causing the differences between the effectiveness of anodic and cathodic neural stimulation are largely unknown.

**Background**
As far as I know, the exact difference between the effectiveness of cathodic versus anodic stimulation are largely unknown. For instance, in animals and humans, both anodic and cathodic pulses can evoke neural responses. In human cochlear implant users, the anodic phase is more effective than the cathodic phase. In contrast, in animals (guinea pigs, cats and ferrets) exactly the opposite is observed. The reason for this discrepancy is unclear (Machery & Cazals, 2016).

The authors in your linked article state (McFadden, 2011):

> We hypothesize that the mechanism behind this may be associated with a concentrated exiting of current from the scalp at the cathode.

This, honestly, makes little sense as that same current was injected at the anode, barred the electrode sizes were not different.

<sub>**Reference**
**-** Machery & Cazals, *Adv Exp Med Biol* (2016); **894**:133-42
**-** McFadden *et al*., *Brain Stimul* (2011); **4**(1): 38–42</sub>
> 2 votes

# Answer
My best answer: Although the cathode contains negative charge, ions that it influences initially only live in the extracellular space.

Neurons are largely regulated by the voltage *difference* between inside and outside the cell.

If the cathodal electrode makes the extracellular space more and more negative, it follows that the intracellular space *relative* to the outside becomes more positive. This leads to increased firing and sensation at the cathodal electrode.

After about 60 seconds of tDCS, the sensation fades. The neurons have grown accustomed to a new default level of positive ions relative to surrounding electrons. The internal space has adopted more electrons.

Now, a follow-up question would be why anodal stimulation is often associated with activation. Of that, I am not sure. Additionally, wouldnt there be firing associated with removal of the anodal electrode if this theory were true?
> 0 votes

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Tags: cognitive-neuroscience, pain, tdcs
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