text:
News from WTOP
News from the AP
Mike Causey
Shows & Panels
Shows & Panels
- The 2014 Big Picture on Cyber Security
- AFCEA Answers
- American Readiness: Renewable Power and Efficiency Technologies
- Ask the CIO
- Building the Hybrid Cloud
- CDWG/NetApp
- Connected Government: How to Build and Procure Network Services for the Future
- Continuing Diagnostics and Mitigation: Discussion of Progress and Next Steps
- Federal Executive Forum
- Federal News Radio's National Cyber Security Awareness Month Special Panel Discussion
- Federal Tech Talk
- The Future of Government Data Centers
- The Future of IT: How CIOs Can Enable the Service-Oriented Enterprise
- Government Perspectives on Mobility and the Cloud
- The Intersection: Where Technology Meets Transformation
- Maximizing ROI Through Data Center Consolidation
- Mitigating Insider Threats in Virtual & Cloud Environments
- Modern Mission Critical Series
- The New Generation of Database
- Reimagining the Next Generation of Government
- Targeting Advanced Threats: Proven Methods from Detection through Remediation
- Transformative Technology: Desktop Virtualization in Government
- The Truth About IT Opex and Software Defined Networking
- Air Traffic Management Transformation Report
- Cloud First Report
- General Dynamics IT Enterprise Center
- Gov Cloud Minute
- Government in Technology Series
- Homeland Security Cybersecurity Market Report
- National Cybersecurity Awareness Month
- Technology Insights
- The Cyber Security Report
- The Next Generation Cyber Security Experts
Shows & Panels
Search Result
Search Tags: Charlie Bolden
The sky is the limit with NASA
What are NASA's key strategic goals? How is NASA expanding the boundaries of science, technology, and imagination? What is NASA doing to cultivate a risk tolerant environment? Join host Michael Keegan as he explores these questions and more with Charlie Bolden, NASA Administrator.
Tags: IBM Center for the Business of Government , Michael Keegan , Business of Government Hour , NASA ,
Monday - 08/18/2014, 05:14pm EDT


text:
Experience Michiana: August 21st, 2014
Having trouble with this video? Let us know.
About This Episode
Episode #734
On tonight's show, we'll get details on an event this Saturday in Baroda, Michigan called "Party on the Pavers." Then a new entertainment season in starting this fall at the DeBartolo Performing Arts Center at Notre Dame, Executive Director Anna Thompson gives us preview of some of the shows coming this year. Finally we'll go down to the Century center to check out the Sky Garden.
- Original Airdate:
- August 21, 2014

subset: commoncrawl


text:
P.O. Box 12335
Reno, NV 89510
Get Directions
Alan Kingsley
Visit Website
Welcome Rodeo Fans to the "Wildest, Richest Rodeo in the West!"
June 18-27,2009
2009 marks the 90th year of the Reno Rodeo - a PRCA Gold Rodeo. From Broncs to Bulls to Barrel Racers, the Reno Rodeo is one event you don't want to miss. While attending the Reno Rodeo, plan extra time to shop, enjoy the carnival, and attend the dozens of events that take place throughout the day. All performances of the Reno Rodeo start at 7:00 pm and tickets range in price from $10 - $23. The finals are on Saturday, June 27 and this performance is always a sell out. Tickets are available at www.RenoRodeo.com.
The Reno Rodeo is a not-for-profit event produced by 350+ dedicated volunteers. A portion of the proceeds from the Reno Rodeo benefit the Reno Rodeo Foundation which provides direct support to children and families with extraordinary needs in northern Nevada. The Reno Rodeo Foundation also provides significant scholarships to the University of Nevada, Reno. For more information on the Reno Rodeo Foundation, please visit www.RenoRodeoFoundation.org.
October 31
Erotic Ball
The biggest and most WILD Halloween party! The 14th annual Wild Erotic Ball! Friday October...
November 15
Blue Jeans Ball
Join Nevada Humane Society for the 2nd annual Blue Jeans Ball, a fun-filled extravaganza at...
November 21
�The Biggest Little City in the World� has a big new attraction, as Wizard World announced the...


text:
Our appliance + cloud powered solutions enable novel learning models for any learning enterprise
Place a YuJa Capture+Broadcast appliance in your classroom to integrate peripherals and devices to create a real-time presentation stream for simultaneous course replay and live broadcast.
With rich mobile applications, students can watch course replays, engage in group collaboration, share ideas, and immerse themselves in rich multimedia course content.
Your YuJa Capture+Broadcast appliance streams and records video presentaions right to your social learning platform. Additional tools to host online lectures, office hours and tutorials.
Combining the engagement of social media with learning is our Social Learning platform equipped with multimedia conversations, chat rooms, video podcasting, and more.
With a single integrated cloud-based platform, conversations and ideas flow naturally.
Create a rich learning community within blended, online, and in-classroom communities.
Both inside and outside of class, capture content with our affordable device+cloud platform.
Host large online lectures with nothing to install or download using our cloud-powered platform.


text:
Paintings in national parks spark anger, investigation
Posted: 10/23/2014 - The blogger, Casey Schreiner of modernhiker.com, says the New York state woman documented her work on Instagram and Tumblr.
Posted: 10/23/2014 - The blogger, Casey Schreiner of modernhiker.com, says the New York state woman documented her work on Instagram and Tumblr.
Updated: 5:15 AM - Dr. Craig Spencer was helping to treat Ebola patients in Guinea as part of Doctors Without Borders.
Updated: 10/23/2014 - 220 Marines, 18 Sailors and 8 Soldiers were killed in a brutal bombing in Beirut, Lebanon on October 23, 1983.
Updated: 10/23/2014 - The donated fire truck will be used for training purposes at New Bern High School's Fire Academy.
Posted: 10/23/2014 - Cindy Manning, Rene Gurganus, Vickie Lilley and Gaye Branch of Williamston in Martin County were part of the Ambush Makeover on TODAY.
Posted: 10/23/2014 - A fire department official says three people were killed and two others were injured when an airplane and a helicopter collided in midair at Frederick Municipal Airport in Maryland.
Updated: 10/23/2014 - David Sutton says the suspension is unprecedented, and he will appeal the suspension to the North Carolina Court of Appeals in Raleigh.
Updated: 10/23/2014 - Lee Bettis, a New Bern attorney and the city's former mayor, will report Friday to start serving his 90 day sentence.
Updated: 3:25 AM - A cool start will quickly warm to around 70 degrees by mid afternoon.
Posted: 10/23/2014 - The owner of a western Pennsylvania Army-Navy surplus store and his nephew have been charged with selling items that were stolen from the Marine Corps base at Camp Lejeune last year.
Posted: 10/23/2014 - Tillis' campaign says the 2012 GOP presidential nominee will be in Raleigh next Wednesday with Tillis, who is in a close contest with Democratic incumbent Kay Hagan.
Updated: 10/23/2014 - Wendy Smith won a 2014 Corvette Stingray from the Dale Earnhardt, Jr. Foundation. She met Earnhardt on Wednesday and picked up the car.
Posted: 10/23/2014 - Goldsboro police say they're looking a man wanted for shooting at two people standing in a driveway.
Updated: 10/23/2014 - A school bus driver has been cited after a morning accident that injured three students.
Updated: 10/23/2014 - The power of fame and celebrity is enough to get a lot of people to take a second look when they are busy online.
Updated: 10/23/2014 - Some people camped out all night to meet Dale Earnhardt Jr. in Washington today. Number 88 was at the Walmart Thursday afternoon.
Updated: 10/23/2014 - In Pitt County, Election Director Dave Davis says 2,219 cast their ballots on Thursday.
Updated: 10/24/2014 - The eclipse was tough to see for most in eastern Carolina, but a select few not only saw the eclipse, they also snapped a few picture.
Updated: 10/22/2014 - Plans for Vidant Health to open a new $4-million dollar health clinic in Belhaven have stalled but the health care provider was hoping to get them rolling again.
Updated: 10/22/2014 - One person is in custody after jumping the fence at the White House Wednesday.
Posted: 10/22/2014 - Camel cigarette maker Reynolds American Inc. is snuffing out smoking in its offices and buildings.
Posted: 10/22/2014 - Governor McCrory says the finding of academic fraud at UNC is a disturbing reminder of what can happen with misplaced priorities and lack of oversight.
Posted: 10/22/2014 - The family of a Texas nurse who flew to Ohio and was diagnosed with Ebola says doctors no longer detect the virus in her body.
Updated: 10/23/2014 - Skies will stay sunny with highs in the upper 60s across eastern Carolina on Thursday.
Updated: 10/23/2014 - The latest investigation found that faculty members and staff missed or overlooked red flags that could've stopped the problem years earlier.


text:
Despite receiving death threats, Pakistan's minister for minorities, a Christian, said he will not give up his battle to guarantee religious freedom for all the country's people.
Read the rest of entry »
Young members of Christ the King Parish dance during an outdoor Mass in Malakal, Southern Sudan.
The discovery of the first known microorganism on Earth to thrive on the toxic chemical arsenic will help expand scientists' understanding of the definition of life, said the head of the Vatican Observatory.
Spurred by the exodus of Iraqi Christians, the Toronto Archdiocese doubled the number of Iraqi refugee families it sponsored in 2010 to 190.
The Vatican is embarking on a project to restore and digitize its archive of more than eight million photographic images.
The Vatican and the Palestine Liberation Organization have agreed to establish a working group to draft an agreement between the two parties.
The Dutch bishops' conference has pledged action after nearly 2,000 people complained of sexual abuse by Catholic priests during an inquiry by an independent commission.
Bishop David Ricken of Green Bay has approved the Marian apparitions seen by Adele Brise in 1859, making the apparitions of Mary that occurred some 30 km northeast of Green Bay the first in the U.S. to receive approval of a diocesan bishop.
As the Nazi executioner beheaded three Catholic priests and a Lutheran pastor, one after another in a matter of minutes, their blood flowed together, creating a powerful symbol for ecumenism in northern Germany.
Changing the world for the better does not come from leaders making grandiose promises or calling for a violent revolution, Pope Benedict said: It comes from humble individuals who silently carry God's light and love to everyone around them.


text:
Andrew Maclean Volkswagen has extended its...
David McCowen Priceless roadster the world's...
More News
All News
Get Car Alerts
More Reviews
Nat Won't be selling for a while.
We visit Romania to search for the Transfagarasan...
Play video
Play video
Play video
Stephen Ottley and Sam Hall discuss the future of...
Cameron McGavin
Janet is after a small, practical and affordable small car with an automated manual transmission.
Drive Team Vince has been told that the lock/actuator assembly on his 2004 Ford Falcon will cost $500.
Rating:3.5 out of 5 stars
More popular new cars
View all
Place an ad
Find out how much your car is worth
Protect yourself when purchasing a car
It's a wiki for everything you auto know
Find local mechanics, panel beaters and more
Find how much your car is worth
Fixed price car servicing made easy
Everything you auto know about tyres
Find the best deal on insurance
Looking to buy a used NISSAN X-TRAIL? Right now there are 957 used NISSAN X-TRAIL cars for sale on drive.com.au.
View all Used NISSAN X-TRAIL for Sale
It's a radical departure from the old model, but that's no bad thing.
Read More
I thought of trading this car a few times but could not bring myself to do so, I like it so much.
really hadny car, does everything really well rather than one or two things superbly, the engine is great, for a larger car its nimble and easy to drive, fantastic fuel economy given the size, huge...
good versitile car, we can go up the beach. we have enough room in the boot to load my sons mini bike and go to the country for a weekend. good big little car. ticks a lot of boxes for us.
later models are much more efficient, cheaper to run and secure. will replace my car by the end of the year
Overall -Excellent - Weaknesses - poor headlights on earlier (my) model. Can be rectified by fitting Phillips plus 100% bulbs.
Great family friendly car. Highly rceommended.
I have had Nissan/Datsun cars in the past and have one now because they are good, reliable and value for money vehicles. I would buy Nissan again as has my daughter.
Love it, never going back to a sedan again. Love going off road
They promise adventure but live in the city and suburbs. Drive compares the best of the compact soft-roader bunch.


text:
Call us at 1-877-214-4288
Use filters below to refine your search
Sort by
Welcome to Vardaan Resorts! This Patnitop hotel offers laundry facilities. There is also a safety deposit box at reception for all your valuables.... hotel details
Prices from
Vardaan Resort Patnitop Patnitop Entry from Kassal Morh Near Nag Temple 182142
We have the accommodation you need, all over the world


text:
|Gift for
| ■ the Item information
Cute pastel onigiri Bento! Ease can fit the triangular onigiri for convenience stores in the tap and put in the bag! Also during the partition because デス top rice balls lower oshinko also available!
It will also served as the rice ball maker boobs!
|■ Spec
-Material / (body) polypropylene (lid) PET ABS ( dividers ) polyethylene
-Size /W90 D89 H65mm
-Color and beige green blue red pink yellow
-Brand, Boulder
-Country of origin, Japan
-* Body only microwave-safe dish washing machine cannot be
Because the features and easy-to-pack ideal for kyaraben-angle is not so easy to wash and care easy, side dish with Bento boxes (lunch boxes)
Picnic / lunch / featured / classic /
|■ ショッピングガイナンス
|Review of the shop ← confidence in Kore! testimonials
|■ search keywords
Bento box lunch box kindergarten lunch box
This product cannot be shipped to United States from the store.
Please contact the store for further information.


text:
Skip to main content
Jul 10, 2014
"The Distortion of Sound" is a documentary about the decline of sound and how technology has changed the way we listen to music, as told through the eyes of artists, experts, and those who know music and sound best.
Jul 09, 2014
Digitally-compressed music
is missing something real. Clari-Fi music restoration technology brings music
back to life.
Apr 01, 2013
With over 4,600 patents and patents pending, plus two prestigious technical GRAMMY™ Awards, HARMAN is the undisputed industry leader in technical know-how.
Please login if you're already registered or register
Oct 30, 2014
STAMFORD, CT -- Harman International Industries, Incorporated (NYSE:HAR) declared a cash dividend on October 30, 2014 of $0.33 cents per share for the quarter ended September 30, 2014.
Read more ...
STAMFORD, CT - Harman International Industries, Incorporated (NYSE: HAR), today announced that its Board of Directors has authorized the repurchase of up to $500 million of the Company's common stock over the next three years.
- Net sales increase 22% to $1.4 billion - Operational EPS increases 38% to $1.31; operational EBITDA up 33% to $164 million - Secures over $2 billion of new automotive awards during the quarter- Board authorizes $500 million share repurchase program - Confirms full year guidance for fiscal year 2015
STAMFORD, CT – HARMAN International Industries, Incorporated (NYSE:HAR), the premier audio, visual, infotainment and enterprise automation group, today named Sandra E. Rowland, currently HARMAN's Vice President, Corporate Development and Investor Relations, as Executive Vice President and Chief Financial Officer, effective January 1, 2015. She will join the HARMAN Executive Committee and continue to report to Dinesh C. Paliwal, Chairman, President and Chief Executive Officer of HARMAN.
JBL Synchros S700
Newsroom provided by NASDAQ OMX


text:
What A Project! So Glad It's Done
I really thought I was not going to finish this, but whew! It's done and I'm so fricking excited! This is only the second afghan I have ever crocheted and I think I did a pretty good job on it.
There are a few things I will do differently the next one I do (not for a few months) but before it gets sold, I wanted you all to see it. : )
The colors I chose are for our Celebrate, Remember, and Fight Back saying. I folded it in half because it's about 6 feet long. LOL


text: Neuron Article Widespread Inhibition Proportional to Excitation Controls the Gain of a Leech Behavioral Circuit Serapio M. Baca,1,2 Antonia Marin-Burgin,1,2 Daniel A. Wagenaar,1,2 and William B. Kristan Jr.1,* 1Sectionof Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0357, USA 2These authors contributed equally to this work. *Correspondence: email@example.com DOI 10.1016/j.neuron.2007.11.028 SUMMARY excitation and inhibition onto a neuron affects the gain of its re- sponse to a given input, because the conductance of the neuron Changing gain in a neuronal system has important can vary dramatically without changing the membrane potential functional consequences, but the underlying mecha- (Chance et al., 2002). The issue of gain control has attracted re- nisms have been elusive. Models have suggested cent attention (Salinas and Thier, 2000) for its importance in sen- a variety of neuronal and systems properties to ac- sory (Dunn and Rieke, 2006) and motor (Berg et al., 2007; Heck- complish gain control. Here, we show that the gain man et al., 2005) processing as well as its likely role in such higher functions as attention (McAdams and Maunsell, 1999), of the neuronal network underlying local bending be- for the coordinate transformations required for visually guided havior in leeches depends on widespread inhibition. reaching movements (Buneo and Andersen, 2006), and for ob- Using behavioral analysis, intracellular recordings, ject recognition in different areas of the visual field (Connor and voltage-sensitive dye imaging, we compared et al., 1997; Salinas and Abbott, 1997). the effects of blocking just the known lateral inhibi- We wanted to know whether interactions between excitation tion with blocking all GABAergic inhibition. This re- and inhibition triggered by sensory stimulation in a feedforward vealed an additional source of inhibition, which was network can adjust the gain of a behavioral circuit. To approach widespread and increased in proportion to increas- this question, we studied how inhibition affects the amplitude of ing stimulus intensity. In a model of the input/output a simple reflexive response—local bending—in the medicinal functions of the three-layered local bending network, leech, a response that is elicited by a localized touch and is we showed that inhibiting all interneurons in propor- produced by longitudinal muscle contraction on the side of the touch and relaxation of the corresponding muscles on the oppo- tion to the stimulus strength produces the experi- site side (Garcia-Perez et al., 2004; Kristan, 1982). The response mentally observed change in gain. This relatively varies with both touch location and touch intensity (Baca et al., simple mechanism for controlling behavioral gain 2005). The circuit that generates local bending involves a small could be prevalent in vertebrate as well as inverte- number of identified sensory neurons (Lewis and Kristan, 1998a), brate nervous systems. interneurons (Lockery and Kristan, 1990b), and motor neurons (Kristan, 1982; Lockery and Kristan, 1990a). The only identified INTRODUCTION central inhibition in this circuit is provided by the connections from the inhibitory motor neurons onto the excitatory motor Behaviors result from an interplay between excitation and inhibi- neurons (Figure 4A) (Granzow and Kristan, 1986; Lockery and tion within the nervous system. Classically, two functions for in- Kristan, 1990a). These inhibitors release GABA in a graded, hibition were recognized: reciprocal inhibition, with one behavior spike-independent manner centrally onto the contralateral exci- being inhibited while another is expressed (Eccles, 1969); and tors (Cline, 1986; Cline et al., 1985; Granzow et al., 1985) and pe- lateral inhibition, the shutting down of sensory pathways just ripherally onto longitudinal muscle fibers (Stuart, 1969, 1970). The outside the area being stimulated, which serves to sharpen the connections were thought to produce an effective lateral inhibi- perception of the stimulus (Kuffler, 1953). In recent years, a new tion that focused the excitation at the site of the touch and relaxed form of interaction has been described, namely simultaneous ex- the opposite side to produce the bend (Kristan et al., 1995). citation and inhibition (Abbott and Chance, 2005), which has This circuit is an appropriate one to study gain control for sev- been found in many parts of the vertebrate nervous system eral reasons. First, at a behavioral level, mechanical stimuli of in- (Berg et al., 2007; Haider et al., 2006; Higley and Contreras, creasing magnitude produce increasingly large responses (Baca 2006; Priebe and Ferster, 2005; Wehr and Zador, 2003), includ- et al., 2005; Thomson and Kristan, 2006). Second, the underlying ing the spinal cord (Eccles, 1969). Several functions have been circuit is a three-layered, feedforward network composed of suggested for this balanced excitation and inhibition, including a small number of identified neurons (Kristan, 1982; Lewis and the production of response variability (Shadlen and Newsome, Kristan, 1998a; Lockery and Kristan, 1990a; Lockery and Kristan, 1994; Stevens and Zador, 1998) and the control of spike trans- 1990b). Third, perturbing the activity of any of the individual neu- mission through the thalamus to the cortex (Wolfart et al., rons affects the expression of the behavior, thereby showing the 2005). A recent intriguing possibility is that the balance between behavioral significance of each neuron (Briggman et al., 2005; 276 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition Figure 1. Generating and Recording Local Bending Responses (A) Schematic diagram of a leech, indicating the lo- cation of its central nervous system: head and tail brains (depicted as large dots at anterior and pos- terior ends) with 21 segmental ganglia (smaller dots) in the ventral nerve cord. To record local bending, we cut open the body wall of segments 8–12 along the dorsal midline and pinned it down, outside up, on a Sylgard substrate. This creates a flat piece of body wall with the cut dorsal midline at the lateral edges. We removed ganglia 8, 9, 11, and 12, leaving only ganglion 10 con- nected to the body wall. We recorded movements from above using a CCD camera mounted on a dissecting microscope, digitized the images, and stored them on a computer. We delivered me- chanical stimuli using an electronically controlled poker with a surface area of about 1 mm2. The du- ration of each stimulus was either 3 s (Figure 2) or 0.5 s (all other experiments); stimuli were spaced 3 min apart to prevent response adaptation. (B) Loosely pinned preparation used to generate local bending. We manually chose points along the edges of the five annuli corresponding to the innervated segment in the first frame in each of the movies (the most anterior and posterior points are indicated by arrows) and used an optical flow- detection algorithm (Ye and Haralick, 2000) to track the motion of these markers. The distance between the anterior and posterior markers 0.5 s after withdrawal of the stimulator was compared to the distance just before stimulation. The trace below the body wall image is a smoothed version of the change of distance between the anterior and posterior markers at each of four locations at 0.5 s after withdrawing the stimulus. Von is the on-target ventral location of the stimulus; Voff, Loff, and Doff are off-target locations in ventral, lateral, and dorsal locations whose movements we plotted. The distance moved was initially measured in units of pixels, which were then normalized to annuli by measuring the number of pixels per annulus. (C) Tightly pinned preparation used to record local bending and neural activity. We measured movements in a selected region of interest (ROI) away from the stimulus site (arrow), to avoid optical and mechanical artifacts caused by movements of the poker. The ROI is indicated as a dark swath across the middle of the image. We represented movements of 80 to 240 locations in a grid within the ROI as vectors. We averaged the lengths of the vector components parallel to the long axis of the body wall at 20 to 80 locations and smoothed this result to obtain a bend profile (graph below the body wall image). Again, the magnitudes of the movements were normalized to the number of annuli. Heinzel et al., 1993; Kristan et al., 1982; Stent et al., 1978; Zoc- RESULTS colan and Torre, 2002). Fourth, local bending depends on a population of distributed interconnections that include inhibitory Role of GABAergic Inhibition on Local Bending connections (Kristan et al., 1995). To establish the input-output function for local bending at a given We performed behavioral experiments while recording from stimulus site, we used a loosely pinned, flattened body wall prep- neurons with intracellular microelectrodes and voltage-sensitive aration that was innervated by a single ganglion (Figure 1B). To dyes (Cacciatore et al., 1999). We monitored the activity of many induce local bends, we applied tactile pulses of constant force neurons at once while knocking out inhibition both pharmacolog- to the skin for 3 s and used an optic flow algorithm to measure ically and electrophysiologically. We found that GABAergic inhibi- the resulting body movements (Ye and Haralick, 2000; Zoccolan tion among the motor neurons produced both lateral inhibition, and Torre, 2002) along four lines of longitudinal markers at 0.5 s as previously shown (Granzow and Kristan, 1986; Lockery and after releasing the stimulus. We applied stimuli to the middle of Kristan, 1990a), as well as a generalized inhibition of most neurons either the right or left ventral surface (i.e., half-way between the in the CNS. This generalized inhibition was responsible for setting ventral midline and the lateral edge) because previous studies the gain of the response, which provided the broad dynamic range (Baca et al., 2005; Thomson and Kristan, 2006) have shown of the response to different levels of sensory stimulation. These re- that these sites produced easily distinguishable bend profiles sults show that very localized sensory stimulation of the leech's in body wall preparations. For each of ten leeches, we applied skin produces a balanced excitation and inhibition that sets the two or three stimuli at each of ten force levels between 0.75 gain of the response. The experiments and modeling suggest and 400 mN. We then washed in a solution of 0.1 mM bicuculline that this inhibition is strong and uniform across all interneurons, methiodide (BMI). Access of BMI to the ganglion was ensured by and possibly all motor neurons, in the ganglion. applying it from below the pinned-out body wall through an inlet Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 277 Neuron Gain Control by Inhibition Figure 2. The Effects of GABAergic Inhibition on the Magnitude of Local Bend Responses (A) Responses of the on-target contractions in the ventral body wall to mechanical stimulation at a single midventral site in normal saline (filled circles) and in saline with 0.1 mM BMI (open circles). The black solid line is a sigmoid fit of the responses in saline, the dashed line is the sigmoid fit to the responses in BMI, and the gray line is the black line multiplied by 2.1. The remaining three graphs are similar plots from responses recorded at three different contralateral off-target sites: ventral (B), lateral (C), and dorsal (D). The gray lines are the black lines multiplied by À1.0 (B), 0.2 (C), and 0.5 (D). In all graphs, the magnitudes of the movements were normalized to the number of annuli. All experiments were repeated in ten preparations. The values shown in all panels are mean ± SEM. built into the Sylgard substrate. In pilot experiments, the effect of at every stimulus intensity at all four locations indicates that BMI was robust within 10 min, so we waited 10 min after applica- BMI increases the amplitude of the response uniformly over tion of BMI before repeating the stimulation protocol. the whole range of stimulus intensities. In other words, the inhi- In control conditions, each touch produced a longitudinal con- bition blocked by BMI changes the gain of the whole system. traction of the on-target ventral body wall at all intensities used, To determine whether the BMI was having its major effects on accompanied by relaxation of the off-target ventral, lateral, and the central nervous system or at the inhibitory connections onto dorsal body wall locations (Figures 2A–2D, filled circles). The re- the muscles (Stuart, 1970), we used a split body wall preparation sponses in all four locations were well fit by sigmoid curves (solid (Figure 3A) with a Vaseline well built around the ganglion. We ap- lines). The on-target responses were contractions that increased plied BMI either to the ganglion inside the Vaseline chamber or in amplitude with increasing stimulus intensity, plateauing at to the body wall outside the chamber. The results to BMI appli- about 0.8 annuli of shortening. The off-target responses were, cation at the two locations were very distinct (Figure 3): applying on average, relaxations whose amplitudes saturated at À0.4 BMI to the body wall alone did not affect either the on-target or (Figure 2B), À0.7 (Figure 2C), and À0.8 (Figure 2D) annuli in ven- the off-target responses (even with 1.0 mM BMI), but applying tral, lateral, and dorsal locations. 0.1 mM BMI to the ganglion produced a larger contraction at Bath application of BMI greatly increased the magnitude of the both sites, both in individual (Figure 3A) and averaged responses on-target contractions, even at low force levels (Figure 2A, open (Figure 3B). In fact, the on-target and off-target responses were circles), and decreased the relaxations at the three off-target not significantly different in the presence of BMI. This experi- sites (Figures 2B–2D, open circles). In fact, the relaxations ob- ment leads to two conclusions: (1) the increased magnitudes served at the off-target ventral site in control conditions became of the local bending responses produced by BMI on the body contractions in the presence of BMI (Figure 2B). To measure the wall (Figure 2) were due entirely to blocking inhibition within size of the change induced by BMI, we multiplied the sigmoid the ganglion; and (2) the contributions of peripheral inhibition curve obtained for the control responses by a value that made to local bending responses were unaffected by bath application its plateau value equal to the sigmoid obtained in BMI. The mul- of BMI. tiplier values required were 2.1 (Figure 2A), À1.0 (Figure 2B), 0.2 Why BMI did not affect inhibition within the body wall might (Figure 2C), and 0.5 (Figure 2D). These scaled values are shown have three causes: (1) the BMI might not gain access to the neu- as solid gray lines in Figures 2A–2D. The fact that the scaled romuscular junctions, (2) the GABA receptors on the muscles curves were within one standard error of the observed data might be insensitive to BMI, or (3) the inhibitory terminals on 278 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition Figure 3. Bath-Applied BMI Blocks GABAergic Inhibition Centrally, Not Peripherally (A) Using a split body wall preparation (icon) with a Vaseline wall around the ganglion, we delivered mechanical stimuli at a single location (left lateral edge) and a single intensity (200 mN). We measured the bend profiles before adding BMI (Control), after adding BMI to the saline bathing the body wall (BMI Periphery), after adding BMI to the saline bathing the ganglion (BMI Central), and after replacing the BMI with saline (Wash) after each BMI addition. This example shows a strong contraction on the side stimulated and a weak contraction on the opposite side. When BMI was applied, the on-target response nearly doubled in size and the off-target response became nearly as large as the on-target response. The fact that there is no contraction in the middle of the graph is an artifact of the prep- aration: the body wall was split up the ventral midline to provide access to the ganglion; the optic flow algorithm detected no movement in this region. We measured on-target and off-target amplitudes at the peaks, which were in sites minimally affected by the midventral incision. (B) Quantification of the BMI effects on the ganglion and on the body wall (n = 10). The values shown are mean ± SEM. Adding BMI to the saline bathing only the body wall (BMI Peripheral) did not change either the on-target or the off-target response, whereas adding BMI to the saline bathing the ganglion (BMI Central) produced a significant increase in both the on-target and off-target responses compared either to pre-BMI application conditions (Saline) or after washing out the BMI (Wash) (ANOVA, p < 0.001; post hoc t tests for individual comparisons, p < 0.01). muscles might be non-GABAergic. Whatever the cause, how- touched; in other words, the inhibitory connections among motor ever, the nonblocked peripheral inhibition is the most likely ex- neurons produce lateral inhibition but do not contribute to the planation for the residual relaxation seen at lateral and dorsal generalized inhibition. body wall sites (Figures 2C and 2D). Hyperpolarizing the Inhibitors Broadens Role of GABAergic Inhibition on Neuronal Responses the Local Bending Response Effects on Motor Neurons From previous studies (Kristan, 1982; Lewis and Kristan, 1998a; To determine how generalized inhibition affects the central ner- Lockery and Kristan, 1990b), the known local bend circuitry in vous system, we recorded intracellularly from motor neurons each segment is a three-layered, feedforward circuit consisting while stimulating one of the four mechanosensory neurons that of just four sensory neurons (pressure-sensitive P cells), about triggers local bending. Previous studies (Kristan, 1982; Lockery two dozen local bend interneurons (LBIs), and about the same and Kristan, 1990b) have shown that stimulating a single P cell number of longitudinal motor neurons (Figure 4A). All the con- excites the excitatory longitudinal motor neurons with their mo- nections indicated are excitatory chemical connections except tor fields in the same area as the touch (i.e., the on-target exci- for the connections from the inhibitory motor neurons (DI and tors), inhibits the excitatory longitudinal motor neurons on the VI) onto the corresponding excitatory motor neurons (DE and opposite side (the off-target excitors), and elicits a mixed VE); these are GABAergic inhibitory connections (Cline, 1986). response in excitors with intermediate movement fields (the To evaluate whether BMI exerted its effects by blocking these intermediate excitors). We replicated these findings using both known inhibitory connections, we removed this inhibition from electrophysiological and imaging techniques (Figure 5). We stimu- the circuit reversibly by strongly hyperpolarizing one of them. lated a single P cell at 10 Hz for 500 ms (comparable to delivering This is an effective procedure because all the inhibitory motor moderate mechanical stimuli to the body wall [Lewis and Kristan, neurons are strongly electrically coupled to one another (Fig- 1998b]) and repeated this stimulus train once per second for ten ure 4B) (Granzow et al., 1985; Lockery and Kristan, 1990b; Ort cycles, to produce a signal detectable by the voltage-sensitive et al., 1974). We stimulated the skin while hyperpolarizing the in- dyes (VSDs). When, for example, we stimulated a PV neuron— hibitor DI-1 throughout the local bend response, using a hole-in- one of the two P cells that innervates ventral leech skin—the the-wall preparation (Figure 4C). In this example, the off-target on-target VE-4 motor neuron was excited (Figure 5D), the off- response increased while the inhibitors were hyperpolarized, target DE-3 motor neuron was inhibited (Figure 5A), and the but the amplitude of the on-target response did not change. Sta- two intermediate excitatory motor neurons (Figures 5B and 5C) tistical comparisons of responses from ten preparations received smaller excitation than the on-target motor neuron. (Figure 4D) showed that the off-target increase was significant These same features were seen in all seven cases tested, in and that the on-target responses were not different. This result both the electrophysiological and the VSD recordings. (Note shows that the central connections of the inhibitors onto the ex- that the cyclic membrane potential changes are captured in citors functioned only to restrict the contraction to the side the VSD recordings, but the faster membrane potential shifts Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 279 Neuron Gain Control by Inhibition Figure 4. Removing Inhibition Among Motor Neurons by Hyperpolarizing the Inhibitors Increased the Off-Target Response but Did Not Affect the On-Target Peak Amplitude (A) Simplified version of the local bend circuitry (Kristan, 1982; Lewis and Kristan, 1998a; Lockery and Kristan, 1990b). Just four pressure-sensitive mechanore- ceptive neurons (a PD and a PV on each side) innervate overlapping regions of the skin, with the centers of their receptive fields in the middle of the two dorsal (D) or ventral (V) regions. All four P cells excite a collection of local bend interneurons (LBIs), which in turn excite the motor neurons to the longitudinal muscles. There are two functional types of motor neurons, excitatory (E) and inhibitory (I), that innervate either the dorsal (D) or ventral (V) longitudinal muscles. All identified connec- tions are feedforward and excitatory, except for those made by the inhibitory motor neurons, which make GABAergic inhibitory synapses onto both the appro- priate longitudinal muscles and the corresponding excitatory motor neurons. Hence, there are four types of motor neurons (DE, DI, VE, and VI) on each side. (The somata of all neurons are in a ganglion on the ventral surface of the segment; they are shown in the middle of the body in this diagram for clarity.) Motor neurons causing muscle contractions in the quadrant whose P cell was stimulated are ''on-target,'' and the ones on the side opposite to the stimulation are ''off-target.'' (B) Schematic version of the electrical connections among the inhibitory motor neurons. Because they make nonrectifying electrical connections to one another, hyperpolarizing one inhibitor hyperpolarizes all of them. (Not shown: DE cells make nonrectifying electrical connections to other DEs, and VEs make nonrectifying electrical connections to other VEs; these connections are not represented in either diagram.) (C) We used the hole-in-the-wall preparation (icon) to impale inhibitory motor neurons while eliciting local bending. We stimulated a single site (black dot on the x axis) and a single intensity (200 mN) while strongly hyperpolarizing a single inhibitor, thereby inactivating all the inhibitory motor neurons via widespread elec- trical connections. Mean bend profiles are shown for one preparation before (solid black line) and while (grey solid line) passing À2 to À7 nA of hyperpolarizing current into an inhibitory motor neuron. (D) The peak amplitudes of the on-target responses were not affected by hyperpolarizing the inhibitory motor neurons (p > 0.40), whereas the off-target responses were significantly increased by these hyperpolarizations (p < 0.04). were lost because of the slow time constant of the dyes [Caccia- We were concerned that BMI application might produce an tore et al., 1999].) excitatory effect on neurons in the circuit, as has been seen in We then stimulated the same neuron after changing the bath- mammalian neurons (Seutin and Johnson, 1999). To control for ing solution to saline containing 0.1 mM BMI to block GABAergic such a direct effect of BMI on leech neurons, we applied inhibition. As in the behavioral experiments (Figure 2), blocking 100 mM BMI to isolated ganglia while monitoring the membrane GABAergic inhibition increased the excitation made by PV potential and the input resistance of sensory neurons, interneu- onto all excitatory motor neurons (right-hand panels in Figures rons, and motor neurons—both excitatory and inhibitory—in 5A–5D, with a light gray background): neurons that had received the local bend circuit. BMI application did not affect the mem- excitation in control conditions (Figures 5B and 5D) received sig- brane potential of mechanosensory P cells (they depolarized nificantly larger excitation in the BMI saline, and those that had by 0.5 ± 1.7 mV, n = 5). BMI application slightly hyperpolarized been inhibited were now excited. These effects of BMI were ob- interneurons and motorneurons: interneuron 212 hyperpolarized served in all seven preparations tested. These results show that 4.5 ± 1.2 mV (n = 3); excitatory motor neurons DE-3 and VE-4 increases in the behavioral responses induced by BMI (Figure 2) hyperpolarized 5.7 ± 1.6 mV (n = 4) and 4.5 ± 2.0 mV (n = 4), are apparent in the responses of the excitatory motor neurons. respectively; and the inhibitory motor neurons DI-1 and VI-2 280 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition Figure 5. Effects of Bicuculline Methiodide on the Responses of Longitudinal Excitatory Motor Neurons (DEs and VEs) to P Cell Stimulation In panels (A)–(D), the top traces show the times when spikes were generated in the right PV neuron, the middle traces are intracellular recordings from either a DE or a VE, and the bottom traces are voltage-sensitive dye recordings obtained from the motor neuron simultaneous with the intracellular recording just above it. The VSD units are percent change in amplitude of the fluorescent signal (DF/F 3 100%). In every panel, the traces on the left were obtained while the ganglion was bathed in standard saline, and the traces on the right (against a gray background) were obtained from the same neuron after replacing the saline with one con- taining 0.1 mM BMI. (A) Intracellular and VSD recordings from the contralateral cell DE-3, an off-target excitor of left dorsal longitudinal muscles. (B) Intracellular and VSD recordings from the ipsilateral cell DE-3, an intermediate excitor of right dorsal longitudinal muscles. (C) Intracellular and VSD recordings from the contralateral cell VE-4, an intermediate excitor of left ventral longitudinal muscles. (D) Intracellular and VSD recordings from the ipsilateral cell VE-4, an on-target excitor of the right ventral longitudinal muscles. hyperpolarized 5.4 ± 1.5 mV (n = 4) and 5.3 ± 0.9 mV (n = 3), re- (Figure 6A) and in the individual trajectories (Figure 6C). Brighter spectively. BMI did not produce any significant change (p > 0.05, colors represent higher coherence values, and different hues t test) in the input resistance of any of these recorded neurons. represent the phases of the responses relative to the stimulus. Hence, the only direct effect of BMI onto the neurons in this cir- The neurons that were phase locked to the stimulated PV cell cuit was inhibitory, an effect opposite to the generalized excita- in normal saline clustered in two distinct phases (Figure 6E), cor- tion seen in local bending after applying BMI. These results responding to excitation (clustered between 45 and 90 ) and showed that the increased excitation in the network seen after inhibition (scattered points around 180 ). BMI application, therefore, were not caused by direct excitatory We then repeated the same PV stimulation regime after replac- effects of BMI on the neurons in the circuit. ing the bathing solution with saline containing 0.1 mM BMI (Fig- Effects on Other Neurons ure 6, middle panels). With all GABAergic inhibition blocked, ev- Because we were imaging all the neurons visible on the dorsal ery neuron had large-amplitude, phase-locked oscillations in the surface of the ganglion with the VSDs while recording from the VSD trajectories (Figures 6C2 and 6D2) that clustered around 90 excitatory motor neurons electrophysiologically, we could also (Figure 6E2), indicating that the PV spike bursts now excited all determine the activity of another 40 to 50 neurons (Figure 6). In the neurons. (The peak of the excitatory responses were, on av- standard saline (left panels of Figure 6), the intracellular record- erage, more delayed in BMI than in control because the inhibition ings (Figure 6B) and the trajectories of the optical signals from caused by each stimulus train occurred later than the excitation; the imaged neurons (Figures 6C and 6D) show that many of therefore, blocking the inhibition selectively enhanced the later them respond to each P cell spike burst, seen as oscillations at part of the excitatory response, which produced the observed the same frequency as the stimulus bursts. Those that were delay in the peak excitation.) One example of a switch in the na- phase locked to the stimulus were active in different phases of ture of the response is provided by the off-target cell DE-3 (arrow the stimulus cycle. This phase locking was quantified using polar in Figure 6E2), which switched its phase from 220 to 90 . This plots (Figure 6E) that show both the phases (distance around the switch is also apparent in the intracellular recordings (Figures circumference) and the coherence magnitudes (distance from 6B1 and 6B2). Comparing the left and middle panels of Figure 6 the center) for all visible neurons (Cacciatore et al., 1999). shows that approximately half the neurons were significantly Neurons with significant coherence values (outside the dashed coherent with the spike bursts in normal saline, with most of lines in Figure 6E) have been colored in the ganglionic images these being excited and the rest inhibited. After removing the Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 281 Neuron Gain Control by Inhibition 282 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition GABAergic inhibition with BMI, the PV stimuli strongly excited ures 6D1 and 6D3: many neurons were excited (i.e., their activity every neuron. We did not see consistent or large changes in phases were between 0 and 90 ), and a few were inhibited the membrane potential or in the spontaneous activity of the neu- (phases were around 270 ). During cell DI-1 hyperpolarization, rons recorded intracellularly when BMI was added, indicating however, PV stimulation no longer inhibited any imaged neurons, that the major changes in response patterns in BMI saline re- and the excited neurons were more tightly clustered around 45 quired sensory stimulation. The effects of BMI reversed within (Figure 7C2). As indicated by the arrows in Figures 6C1–6C3, 10 min after washing the ganglion with normal saline (right panels hyperpolarizing the inhibitors inverted the response of the off- of Figure 6). target excitors: normally inhibited by PV stimulation, they were To be sure that the BMI did indeed block inhibition, we stimu- excited during hyperpolarization of the inhibitors in 6 of 6 exper- lated inhibitors through intracellular electrodes and found that iments. However, hyperpolarizing the inhibitors did not produce BMI was very effective in blocking their central inhibitory effects an effect as widespread as that produced by BMI (compare on excitors (data not shown). Interestingly, many neurons that Figure 7B2 to Figure 6D2), strengthening the conclusion that were clearly inhibited by the inhibitors in saline were found to the central effects of the inhibitory motor neurons do not contrib- be excited by them in the presence of BMI, possibly by their elec- ute to the generalized inhibition documented in Figures 2 and 6. trical connections. Such dual electrical and chemical connec- The differences between application of BMI and hyperpolariz- tions between neurons have been observed in the leech CNS ing the inhibitors are quantified in Figure 7D. Application of BMI (Nicholls and Purves, 1970; Ort et al., 1974), as well as in other significantly increased the number of cells excited by PV stimula- nervous systems (Hatton, 1998; Mamiya et al., 2003; Moss tion, measured as the number of neurons significantly coherent et al., 2005). with the stimulus (one-way ANOVA, F3, 33 = 12.11, a posteriori It should be noted that included in the many neurons that were Tukey test p < 0.001; n = 7). Hyperpolarizing the inhibitor cell excited by Pv stimulation with BMI present were the inhibitory DI-1 did cause an increase in the number of neurons excited motor neurons. In fact, the inhibitors would be more strongly ac- by PV stimulation compared to control (p < 0.05; n = 6, 7, respec- tivated by Pv stimulation in the presence of BMI—because the tively), but this number was less than the number excited by PV central inhibition onto them would be blocked (Figure 6) but their stimulation during BMI application (p < 0.05). The values for peripheral inhibition would not be affected (Figure 3)—so that both conditions after ending the treatment (BMI application or they would generate more relaxation of the muscles. Hence, hyperpolarization) were not different from control. the difference between the BMI and control curves in Figure 2 is likely to be an underestimate of the effect of central inhibition. A Model with Generalized Feedforward Inhibition Reproduced the Major Behavioral Results Contribution of Inhibitory Motor Neurons To test whether the observed generalized inhibition could in the CNS Expression of Local Bending change the gain of the output by acting on the interneurons, We determined whether the known inhibitory connections from we modeled the input-output functions of the local bending inhibitors onto excitors contributed to the generalized inhibition circuit with and without the generalized inhibition, to mimic the by strongly hyperpolarizing one of them, in the same way that effects of blocking inhibition with BMI (Figure 8A). In particular, we had previously tested for the effects of this inhibition on local we wanted to capture the two major features of the behavioral bending behavior (Figure 4). For these experiments, we imaged experiments (Figure 2): (1) blocking the GABAergic inhibition the dorsal surface of each ganglion with VSDs while stimulating caused a 2-fold increase in the whole stimulus-response curve, a PV cell before, during, and after hyperpolarization of the inhib- whereas (2) the minimal touch intensity needed to cause a re- itors (Figure 7). In control recordings before and after hyperpola- sponse did not change detectably. We used a simplified network rizing cell DI-1, the responses of the neurons to PV stimulation model (Figure 8A1), consisting of a mechanosensory P cell (P), (Figures 7B1 and 7B3) were comparable to the responses in Fig- which excites a local bend interneuron (LBI), which in turn excites Figure 6. Effects of Bicuculline Methiodide on the Responses of All Neurons on the Dorsal Surface of a Midbody Ganglion (A) Images of the dorsal surface of a midbody ganglion used to record neuronal activity with voltage-sensitive dyes. Hand-drawn ellipses indicate the boundaries of neuronal somata. The numbers were assigned according to the positions of the somata on a standard ganglionic map (Muller et al., 1981). The colors indicate the phase of the VSD trajectories of each neuron relative to the stimulus burst cycles, as determined by the phase plots in (E1)–(E3) below. The arrows here and in panels (C)–(E) identify the cell DE-3 that was recorded intracellularly. Scale bars, 50 mm. (B) The top traces are intracellular recordings from a PV cell (outside the field of view in panel [A]) showing when trains of five action potentials were evoked by depolarizing current pulses (5 nA, 7 ms, 10 Hz) generated for 500 ms at 1 Hz. Simultaneous intracellular recordings (middle traces) and optical trajectories (bottom traces) show the responses of the indicated cell DE-3. The colors of the optical traces correspond to the phases of the response (from panel [E]): blue indicates inhibition, and gold indicates excitation. The B2 recordings are responses of DE-3 to the same PV stimulation with 0.1 mM BMI in the bathing solution. (C) Recordings of the driven spike burst in the PV cell (top trace) along with fluorescence signals from the 43 cells visible in the ganglion (A1–A3). Colors of the fluorescence traces correspond to phasing of the responses (from [E1]–[E3]); gray traces indicate noncoherent neurons. Calibration bars are displayed below and to the right of the recordings. Signals are lined up in decreasing order of their coherence values, with the maximum value (with the largest oscillation amplitude) at the top. (D) Optical recordings from the same 43 neurons, with response valence indicated by color: red indicates depolarization to each burst, and blue indicates hyperpolarization to each burst (color bar to the right of [D3]). (E) Polar plots indicate the coherence phase (circumferential distance from 0 ) and magnitude (linear distance from the center of the plot) for all neurons observed in the image. Each point indicates the average phase and maximal amplitude of a single neuron; the lines from each point indicate the standard errors in both amplitude and phase about the mean. Neurons with amplitude values greater than the dashed line are coherent with the stimulus at the 95% confidence limit. Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 283 Neuron Gain Control by Inhibition Figure 7. Effects of Removing Inhibition, by Hyperpolarizing the Inhibitor Responses, on All Neurons on the Dorsal Surface of a Midbody Ganglion (A) Images of the dorsal surface of a midbody ganglion used to record neuronal activity with voltage-sensitive dyes. As in Figure 2, we impaled a mechanosensory PV neuron (outside the field) and elicited a train of spikes at 10 Hz for 500 ms, repeated every second for 10 s. The color of each neuron indicates the phase of its response relative to the stimulated neuron (C1–C3). Experiments were performed without passing current into the DI-1 neuron (Control), during the time that cell DI-1 was hyperpolarized with À5 nA, then again not passing current into DI-1. Scale bars, 50mm. Arrows point to cell VE-4, an excitatory motor neuron to the ventral muscles, which is inhibited by VI-1 in standard saline. The arrows in succeeding panels indicate data from this motor neuron. (B) Raster plots showing the optical signals from all circled cells in (A), with changes in fluorescence amplitude indicated by colors (calibration bar to the right of the raster plots). (C) Polar plots showing the coherence phase (the angle from 0 ) and magnitude (distance from the center) of the responses of all observed neurons. Values greater than the dashed line are coherent, at 95% confidence, with the stimulus. (D) Number of neurons that showed significantly coherent responses to stimulation of a PV cell relative to the total number of cells imaged in each experiment (mean ± SEM for control): premanipulation control (n = 13), after adding BMI (n = 7), while hyperpolarizing the inhibitors (n = 6), and after each manipulation (n = 13). (*p < 0.05, ***p < 0.001 [one-way ANOVA, F3,33 = 12.11, a posteriori Tukey test]). 284 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition Figure 8. Modeling the Influence of Central GABAergic Inhibition on the Local Bend Response (A) Model with feed-forward inhibition. (A1) Schematic of the modeled circuit. The model consists of one so- matosensory P cell (P), one interneuron (LBI), one mo- tor neuron (MN), and one GABAergic inhibitor (G). The T bars indicate excitatory connections, and black cir- cles represent inhibitory connections. (A2) Activity of the modeled cells as a function of skin touch: with in- hibition intact (solid black), with inhibition blocked (dashed black), with decreased inhibition (down- pointing triangles), and with increased inhibition (up- pointing triangles). For the black curves, the model parameters (slopes, locations of half-maximum re- sponse, and synaptic strengths) were chosen to make the output resemble the experimental results (gray lines in bottom panel: control, solid; with BMI, dashed). (B) Model with saturating inhibition. (B1) Schematic. The thick T bar represents a stronger synapse between P and G. All other connections were the same as in (A). (B2) Activity of the modeled cells: with a medium amount of saturating inhibition (solid), increased inhibi- tion (up-pointing triangles), reduced inhibition (down- pointing triangles), and no inhibition (dashed; identical to results in [A2] by construction). In this version of the model, increasing the activity of the G cell shifted the MN output left to right (solid lines in LBI and MN), unlike the experimental data (gray lines as in [A2]). a motor neuron (MN). The responses of the sensory neuron ure 8B), the resulting G cell activity was effectively constant (curve P) provided the input to the circuit, and the motor neuron over most of the P cell activity range, producing a left-right shift responses (curves MN) were the output of the system. In the of the MN output along the ''touch intensity'' axis (i.e., it had leech, there are approximately two dozen interneurons and mo- a subtractive effect) rather than a scaling (i.e., a multiplicative tor neurons involved in the local bend reflex, so MN and LBI rep- effect). resent classes of neurons rather than single cells. To represent the generalized inhibition, we used a GABAergic cell (G), which DISCUSSION is excited by the P cell and inhibits the interneuron with a synaptic strength g. The firing rate of each cell is a simple sigmoidal func- We found that the circuit producing local bending behavior in the tion of its inputs, defined by only two parameters, a slope and leech recruits two types of inhibition to produce a precise local- a threshold. We examined the effect of the generalized GABA- ized response: a lateral inhibition through inhibitory motor neu- ergic inhibition by varying the strength of the inhibitory synapses rons that restricts the contraction to the side that was stimulated, (g) onto the interneuron. In particular, setting g = 0 corresponds and a generalized inhibition, independent of the inhibitory motor to complete blocking of GABAergic inhibition, corresponding to neurons, that restricts the amplitude of the response in propor- the application of BMI. tion to the intensity of stimulation. We chose connection strengths that produced an input/output The generalized increase in the amplitude of local bending function in the motor neuron that matched the behavioral data for during BMI application (Figure 2) was unexpected. The local the on-target region of the body wall (Figure 2A); the responses bend circuit had been thought to be a broadly dispersed, feed- of the P, G, LBI, and MN neurons in this condition are shown forward excitatory network from P cells to local bend interneu- as black lines in the graphs in Figure 8A2. With g = 0 (i.e., no in- rons, to motor neurons, with lateral inhibition only at the motor hibition), the responses of LBI and MN increased in amplitude neuronal level to sharpen up the edges of the contraction and but did not shift along the ''touch intensity'' axis (dashed black produce relaxation on the opposite side (Kristan et al., 1995; lines). The model data closely matched the experimental data Lockery and Kristan, 1990b). Instead, the finding of a strong, in control conditions (solid gray line) and after BMI application generalized inhibition implies that the excitatory connections (dashed gray line). The gain of the model output could be con- by themselves would produce a segment-wide contraction of trolled by altering the activation threshold of the GABAergic all the longitudinal muscles, even at low stimulus intensity (Fig- cell (thin black lines with triangle markers). ures 3 and 4). This is indeed what was observed in embryonic For GABAergic inhibition to result in a change of gain of the leeches, before GABAergic inhibition is detectable (Marin-Burgin output, it was critical that the GABAergic cell (G) was activated et al., 2005). The presence of this generalized inhibition means over the same range of touch intensities as the P cell, and in that all the motor neurons—even those that produce the contrac- the same manner. If, instead, the P-to-G synapse was so strong tion that is the active component of the bending response—nor- that the G cell activity saturated at low touch intensities (Fig- mally receive a significant level of inhibition that strongly reduces Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 285 Neuron Gain Control by Inhibition the excitation triggered by the stimulus. When we monitored the Ferster, 2005; Wehr and Zador, 2003). Our results show that feed- responses of individual motor neurons with intracellular record- forward inhibition can also be used to adjust the gain of the circuit ings (Figures 5 and 6), we found exactly this: all excitors became that triggers it. We found that a generalized feedforward inhibition significantly more active in the presence of BMI. onto the circuit produces a multiplication of the local bend Producing scalable neuronal activity appears to be a property response over the whole range of stimulus amplitudes, from of many nervous systems, some much more complicated than threshold to saturation (Figure 2). Our simple model of parallel ex- that of the leech. For instance, a recent study on the rodent so- citation and inhibition (Figure 8A) shows that a feedforward inhib- matosensory cortex suggests that cortical circuits regulate their itory circuit, activated in a graded manner by the sensory cells, relative levels of excitation and inhibition across varying magni- can change the gain of the local bending circuit and therefore tudes of input (Higley and Contreras, 2006). Combined excitation could explain the results of physiological experiments with and inhibition appears to be required for sensory processing not GABA blockers (Figure 2), whereas a saturating inhibitory circuit only in the somatosensory cortex (Gabernet et al., 2005; Wilent (Figure 8B) failed to reproduce the experimental results. It is pos- and Contreras, 2005) but in visual (Priebe and Ferster, 2005), au- sible that modulation of this feedforward inhibitory circuit, repre- ditory (Wehr and Zador, 2003), and olfactory systems (Murphy sented by G in the circuits of Figure 8, could be partially respon- et al., 2005; Yokoi et al., 1995). The level of inhibitory activity sible for the suppression of the local bend response during other has long been recognized as a determinant of triggering seizure behaviors such as feeding (Misell et al., 1998). activity (Magloczky and Freund, 2005; Ribak et al., 1979), sug- gesting that a delicate balance of ongoing excitation and inhibi- EXPERIMENTAL PROCEDURES tion is important for normal functioning of the vertebrate brain. Modeling studies have found, for instance, that for activity to Leech Care be able to propagate through a structure like the cortex without Adult medicinal leeches (Hirudo sp.) from Carolina Biological Supply Co. explosive activation requires a very narrow balance between (Burlington, NC) and Leeches USA (Westbury, NY) were maintained in a cool excitation and inhibition (Vogels and Abbott, 2005). Our results room (15 C; 12 hr light/dark cycle) in 5 gallon aquaria containing Instant Ocean indicate that even only moderately complex neuronal networks Sea Salt (Aquarium Systems, Mentor, OH; diluted 1:1000 with deionized water). They weighed 2.0–5.0 g and had not eaten for at least 4 weeks. (Garcia-Perez et al., 2004) employ a balance between excitation and inhibition to produce useful behaviors. The issue of gain control has become recognized as one of the Body Wall Preparations most universal neural computational principles (Salinas and To dissect the leeches, we used ice-cold leech saline (Muller et al., 1981) to anesthetize them. To perform experiments, we used saline at room tempera- Thier, 2000). Previous studies had concluded that inhibition pro- ture (20 C–22 C). Body wall preparations produced reliable local bends for duced a linear shift in the input-output function of a neuron (a longer than 4 hr. To reduce variability, we always used segment 10 of the 21 subtractive process) rather than a change in its slope (a divisive midbody segments. We waited at least 3 min between stimuli to avoid sensi- process). It has proven difficult to find cellular mechanisms that tizing or habituating motor responses (Lockery and Kristan, 1991). We used can change the gain of a system in a controlled way. For in- body wall preparations similar to those used previously (Baca et al., 2005; Kri- stance, pure inhibition produces a subtraction (i.e., a shift in stan, 1982; Nicholls and Baylor, 1968), consisting of three segments removed the input/output function to a less sensitive part of the response from the leech midbody region (Figure 1A) and cut along the dorsal midline. We removed the anterior and posterior ganglia, leaving only the central segment range) rather than division (i.e., a decrease in the slope of the innervated by a single ganglion, then flattened the body wall and pinned it input/output function [Chance et al., 2002; Doiron et al., 2001]). skin-side up on a plastic Petri dish coated with Sylgard (Dow Corning, Midland, In general, addition and subtraction are linear processes, MI; Figures 1B and 1C). We used these preparations to record behavioral whereas multiplication and division are nonlinear ones. Because movements (Figure 2). To apply drugs to either the ganglion or the body wall it produces a nonlinear change in excitatory synaptic inputs, selectively, we used a split body wall preparation, in which we additionally shunting inhibition has been proposed as a mechanism for divi- cut along the ventral body wall, leaving the ganglion attached to the left and right halves (Figure 3A); we then formed a water-tight Vaseline well around sion (Carandini and Heeger, 1994), but the effect of having the ganglion through which the lateral nerve roots passed. To record from neu- a threshold for spiking acts to offset this nonlinearity and make rons and stimulate them individually, we used a hole-in-the-wall preparation, in the input/output function for spiking activity very nearly linear which the opening in the ventral body wall was limited to a small hole just over (Holt and Koch, 1997). Another mechanism proposed for the ganglion (Figure 4C). For the experiments using voltage-sensitive dyes, we multiplication is modulation of voltage-sensitive channels in the used a single isolated ganglion dissected free of the body wall entirely and dendrites of cortical neurons by serotonin and norepinephrine pinned to the Sylgard in a Petri dish. In some electrophysiological and all im- aging experiments, we removed the connective tissue capsule and the glial (Heckman et al., 2003) because the active dendrites produce packets that encase the neuronal somata to ease cell impalements and to de- a nonlinearity that approximates multiplication (Heckman et al., liver both drugs and voltage-sensitive dyes. 2005). Another, more systems-level mechanism for producing We recorded intracellularly from neuronal somata with sharp glass micro- multiplication is to balance the overall level of excitation and in- electrodes (20–30 MU filled with 3 M potassium acetate). We identified motor hibition so that the membrane potential of the neuron remains neurons by their location, size, and electrophysiological properties (Stuart, constant but the neuron becomes less responsive to a given in- 1970) and delivered current-clamp pulses using an Axoclamp 2-A amplifier put as the balanced excitation and inhibition increases (Chance controlled with Axograph 4.9 (Axon Instruments, now Molecular Devices, Sun- nyvale, CA) on a PowerPC G3 computer (Apple, Cupertino, CA). We removed et al., 2002). all the inhibitory effects produced by the inhibitory motor neurons by passing Feedforward inhibition has been found, in several systems, to strong hyperpolarization (À2 to À7 nA) into one inhibitory motor neuron (Gran- adjust the timing at which spikes occur (Blitz and Regehr, 2005; zow et al., 1985; Lockery and Kristan, 1990b); this works because all the inhib- Mittmann et al., 2005; Pouille and Scanziani, 2001; Priebe and itory motor neurons are electrically coupled to one another (Figure 4B). 286 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition Delivery of GABA Blockers and dorsal [Doff]). (The lateral and dorsal movements ipsilateral to the stimulus Preliminary experiments using bicuculline methiodide (BMI), SR 95531 were distorted by the movements of the stimulator arm and could not be mea- (''GABAzine''), and picrotoxin showed that only BMI blocked the inhibition sured reliably.) We manually marked points along the edges of the five annuli from inhibitory motor neurons onto excitatory motor neurons, a synapse corresponding to the innervated segment in the first frame of each of the result- known to be GABAergic (Cline, 1986); we therefore used only BMI to block in- ing movies, then used the optic flow detection algorithm (Ye and Haralick, hibitory transmission. BMI is known to block calcium-activated potassium 2000) to track the motion of these markers. We delivered mechanical stimuli channels responsible for afterhyperpolarization in a variety of mammalian of 3 s duration spaced 3 min apart to prevent response adaptation. The actual preparations, thereby increasing the excitability of the neurons (Seutin and force applied was verified using a lab balance placed under the Petri dish. Johnson, 1999). We saw no evidence for such effects on leech neurons; in In this manner, forces as low as 1 mN could be applied with less than 10% fact, a previous study (Cline, 1986) as well as our own control experiments variability. (in the section on GABAergic Inhibition) found that BMI slightly hyperpolarized To record electrophysiologically, we needed to pin the preparation tightly leech motor neurons, thereby decreasing their excitability. We delivered BMI along all four of its margins (Figure 1C). The contractions at the site of stimu- (Sigma-Aldrich) to the ganglion by a gravity-fed drip system at a concentration lation were readily visible; they were smaller than those recorded in less con- of 0.1 mM. Initial experiments showed that this concentration produced com- strained preparations but were qualitatively similar. The relaxations contralat- plete block of the central inhibition among the motor neurons, but did not block eral to the site of stimulation, however, were often not visible. To measure local the inhibitory neuromuscular junctions in the body wall. bending in these preparations, we selected a rectangular region of interest (ROI) that showed robust movement and was free from edge or pinning arti- Stimulus: Force Controller facts (Figure 1C). The ROI spanned one to two annuli along the long axis of As described previously (Baca et al., 2005), we used a Dual-Mode Lever Arm the leech and included its entire circular axis. For a given preparation, we System (''poker''; Aurora Scientific, Ontario, Canada, Model 300B) to deliver used the same ROI for all trials. Because we were most interested in the con- tactile stimuli at a chosen force (0.75–400 mN) to the leech body wall using tribution to local bending produced by the longitudinal muscles, we calculated a 1 mm diameter bead of epoxy on the tip of a 27 ga needle (Figure 1A). We only that component of the movement that ran parallel to the leech's long axis. mounted the head stage of the force controller on a micromanipulator (Narish- ige International, East Meadow, NY). The stimuli produced a range of local Quantification of Behavior bend responses similar to the bends produced in earlier studies using smaller In the loosely pinned preparations (Figure 1B), we compared the distance be- forces with smaller-tipped filaments (Garcia-Perez et al., 2004; Lewis and tween anterior and posterior markers 0.5 s after withdrawal of the stimulator to Kristan, 1998a, 1998b; Zoccolan and Torre, 2002). the distance just before stimulation. The recording below the trace is one smoothed response to a stimulus at Von in the middle of the intensity range Terminology used, with the length measurement normalized to the average length of an an- We have chosen to use the terms ''ipsilateral'' and ''contralateral'' to indicate nulus (annuli are elevations in the skin of the body wall that run circumferentially the locations of the peripheral fields of sensory and motor neurons rather around the body; five annuli constitute one segment). In the tightly stretched than to indicate the locations of their somata within the ganglion. This pre- preparations (Figure 1C), the stimulus lasted 0.5 s, and the response peaked serves their functional connectivity: each mechanosensory P (pressure-sensi- at about 1.0 s after stimulus offset; we therefore used the cumulative motion tive) cell excites its ipsilateral excitatory motor neuron, even though the somata profile at the peak of the response, in units of annulus widths. We smoothed are on opposite sides of the ganglion. In addition, we use the term ''on-target'' these motion profiles with a Gaussian filter. We measured the magnitude of to refer to the motor neurons that contract the body wall in the same area of the responses as their peak amplitudes because, although it is only a single body wall innervated by the stimulated P cell, and ''off-target'' to refer to the measure of each response, it is the closest behavioral counterpart to the motor neurons that contract muscles on the body wall directly opposite (Fig- peak firing rate of the motor neurons responsible for longitudinal muscle con- ures 4A and 5). The areas between these two are called ''intermediate'' in lo- tractions (Mason and Kristan, 1982). cation. Each longitudinal muscle motor neuron is identified by three features: (1) the location of the longitudinal muscle it innervates (D, dorsal; V, ventral), (2) whether it excites the muscle or inhibits it (E or I), and (3) the number assigned Monitoring the Electrical Activity of Multiple Neurons to its soma on the standard ganglionic map (Muller et al., 1981). Hence, cell Using Voltage-Sensitive FRET Dyes DI-1 inhibits dorsal longitudinal muscles, and its soma is in map location 1. We stained dissected, isolated ganglia from adult leeches with a pair of FRET For brevity, we sometimes use the terms ''excitor'' and ''inhibitor'' in place of dyes: 10 mM solution of the donor, coumarin [N-(6-chloro-7-hydroxycoumarin- ''excitatory longitudinal muscle motor neuron'' and ''inhibitory longitudinal 3-carbonyl)-imyristoylphosphatidylethanolamine] and 12.5 mM of the accep- muscle motor neuron.'' tor, oxonol [bis (1,3-diethyl-thiobarbiturate)-trimethine oxonol], both from Ver- tex Pharmaceuticals Inc., San Diego, CA. For details of their preparation and Behavioral Video Recordings application, see Cacciatore et al. (1999) and Taylor et al. (2003). We acquired We recorded the image of the body wall preparation (Figures 1B and 1C) fluorescence images using an upright microscope (Axioskop 2FS; Zeiss, through a Wild dissection microscope using a C-Mounted Hitachi KP-M1 Thornwood, NY) equipped with a 403, 0.8 NA water-immersion objective monochrome CCD camera (Image Labs International, Bozeman, MT). We cap- (Achroplan; Zeiss). For epi-illumination we used a tungsten halogen lamp tured the images (640 3 480 pixel resolution) at 10 Hz and digitized using (64625 HLX; Osram Sylvania, Danvers, MA) in standard housing (HAL 100; a Data Translation frame grabber card (DT3155) controlled with the MATLAB Zeiss), powered by a low-ripple power supply (JQE 15-12M; Kepco, Flushing, (The Mathworks, Natick, MA) Image Acquisition Toolbox on a PC computer NY). For all voltage-sensitive dye imaging, we acquired images only at the (Figure 1A). On a different computer, pulses from Axograph 4.9 software coumarin emission wavelength. The filter set consisted of a 405 ± 15 nm (Axon Instruments, Union City, CA) synchronized video acquisition with the band-pass excitation filter, a 430 nm dichroic mirror, and a 460 ± 25 nm stimulus controller and the electrical recordings. As previously described band-pass emission filter (Chroma Technology Corporation, Brattleboro, (Baca et al., 2005), we tracked the body wall motion by making optic flow VT). We acquired the optical data using a water-cooled CCD camera (Micro- estimates between successive image frames (Lucas and Kanade, 1981; Ye Max 512 BFT; Roper Scientific, Tucson, AZ) operated in frame-transfer and Haralick, 2000). We captured 20 to 40 images that include the onset of mode at a frame rate of 20 Hz. The CCD chip in this camera has 512 3 512 the bend, then calculated optic flow fields between successive frames. pixels, but we binned at 4 3 4 pixels to yield a 128 3 128 pixel image. The To minimize the effects of restraining the preparation in behavioral studies, CCD chip was maintained at À25 C during imaging. Images were stored using we pinned the body wall only in the denervated anterior and posterior ends the software package Win-View/32 (Roper Scientific, Trenton, NJ). The com- (Figure 1B). In these preparations, we measured local bending responses bination of coumarin and oxonol yielded sensitivities of 5%–20% change in along anterior-posterior lines in the five innervated annuli at four locations: fluorescence/100 mV for 1 Hz square-wave voltage signals with a 10 mV am- on-target ventral (Von) and three off-target sites (ventral [Voff], lateral [Loff], plitude, centered around a resting potential of À50 mV. Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 287 Neuron Gain Control by Inhibition Image Analysis Briggman, K.L., Abarbanel, H.D.I., and Kristan, W.B., Jr. (2005). Optical imag- We analyzed the images using a custom-made graphic user interface in Mat- ing of neuronal populations during decision-making. Science 307, 896–901. lab. We averaged all pixels within each cellular outline in each frame (Taylor Buneo, C.A., and Andersen, R.A. (2006). The posterior parietal cortex: Senso- et al., 2003). To find neurons responding to a stimulated mechanosensory neu- rimotor interface for the planning and online control of visually guided move- ron, we impaled the sensory neuron's soma with a microelectrode and passed ments. Neuropsychologia 44, 2594–2606. a train of current pulses (4 nA, 7 ms, 15 Hz) for 500 ms each second while Cacciatore, T.W., Brodfuehrer, P.D., Gonzalez, J.E., Jiang, T., Adams, S.R., simultaneously collecting images at 20 Hz for 10 s. We always impaled a Tsien, R.Y., Kristan, W.B., and Kleinfeld, D. (1999). Identification of neural cir- postsynaptic cell to compare optical data with intracellular recordings. Using cuits by imaging coherent electrical activity with FRET-based dyes. Neuron 23, coherence analysis (coherence is essentially a correlation of two trajectories 449–459. at the dominant shared frequency, in this case 1 Hz), we identified neurons whose optical signals were correlated with the stimulated one (Cacciatore Carandini, M., and Heeger, D.J. (1994). Summation and division by neurons in et al., 1999). In some experiments, a 100 mM BMI solution was applied to the primate visual cortex. Science 264, 1333–1336. ganglion; images were taken before and during BMI application. We then Chance, F.S., Abbott, L.F., and Reyes, A.D. (2002). Gain modulation from washed out the BMI solution for 10 min and obtained a post-wash recording. background synaptic input. Neuron 35, 773–782. Cline, H. (1986). Evidence for GABA as a neurotransmitter in the leech. J. Neu- Statistics rosci. 6, 2848–2856. We applied standard statistical tests to our data (one-way ANOVA, a posteriori Cline, H.T., Nusbaum, M.P., and Kristan, W.B., Jr. (1985). Identified GABAergic Tukey test; MANOVA for multivariate data, and corrected one-tailed and inhibitory motor neurons in the leech central nervous system take up GABA. two-tailed t tests where appropriate) using the Statistics Toolbox in MatLab. Brain Res. 348, 359–362. All values listed are mean ± SEM. Connor, C.E., Preddie, D.C., Gallant, J.L., and Van Essen, D.C. (1997). Spatial attention effects in macaque area V4. J. Neurosci. 17, 3201–3214. Modeling Input-Output Functions of the Neurons Doiron, B., Longtin, A., Berman, N., and Maler, L. (2001). Subtractive and divi- in the Local Bend Circuitry sive inhibition: effect of voltage-dependent inhibitory conductances and noise. The P cell in the model was activated by skin touch using a sigmoidal of the Neural Comput. 13, 227–248. form Dunn, F.A., and Rieke, F. (2006). The impact of photoreceptor noise on retinal PðFÞ = 1=2 + 1=2 tanhðaP logðF=qP ÞÞ; gain controls. Curr. Opin. Neurobiol. 16, 363–370. Eccles, J.C. (1969). The Inhibitory Pathways of the Central Nervous System (Springfield, IL: Thomas). where F is the touch force (in milliNewtons), qP = 25 mN, and aP = 0.3. Gabernet, L., Jadhav, S.P., Feldman, D.E., Carandini, M., and Scanziani, M. The activation of the other cells was modeled using sigmoidal functions of (2005). Somatosensory integration controlled by dynamic thalamocortical their synaptic inputs: feed-forward inhibition. Neuron 48, 315–327. GðPÞ = 1=ð1 + ðqG =PÞaG Þ; Garcia-Perez, E., Zoccolan, D., Pinato, G., and Torre, V. (2004). Dynamics and reproducibility of a moderately complex sensory-motor response in the medic- a IðP; GÞ = 1=ð1 + ðqI =ðP + gGÞÞ I Þ + I0 ; inal leech. J. Neurophysiol. 92, 1783–1795. and Granzow, B., and Kristan, W.B., Jr. (1986). Inhibitory connections between motor neurons modify a centrally generated motor pattern in the leech hir- a MðIÞ = 1=ð1 + ðqM =IÞ M Þ: udo-medicinalis nervous system. Brain Res. 369, 321–325. Granzow, B., Friesen, W., and Kristan, W., Jr. (1985). Physiological and mor- To match the experimental results (black curves in Figure 8A), we used phological analysis of synaptic transmission between leech motor neurons. qG = 1.4, aG = 1.7, qI = 0.4, aI = 1.1, I0 = 0.02, qM = 1.4, aM = 1.9, and g = 1.65. J. Neurosci. 5, 2035–2050. Haider, B., Duque, A., Hasenstaub, A.R., and McCormick, D.A. (2006). Neo- ACKNOWLEDGMENTS cortical network activity in vivo is generated through a dynamic balance of ex- citation and inhibition. J. Neurosci. 26, 4535–4545. We thank our colleague, Massimo Scanziani, for helpful suggestions in prepar- Hatton, G.I. (1998). Synaptic modulation of neuronal coupling. Cell Biol. Int. 22, ing the manuscript. The research was supported by an NIH research grants 765–780. MH43396 and NS35336 (W.B.K.) and by gifts from the Microsoft Research Laboratory and Richard Geckler and by an NRSA award (MH13037) to S.M.B. Heckman, C.J., Lee, R.H., and Brownstone, R.M. (2003). Hyperexcitable den- drites in motoneurons and their neuromodulatory control during motor behav- Received: March 20, 2006 ior. Trends Neurosci. 26, 688–695. Revised: August 22, 2007 Heckman, C.J., Gorassini, M.A., and Bennett, D.J. (2005). Persistent inward Accepted: November 28, 2007 currents in motoneuron dendrites: Implications for motor output. Muscle Nerve Published: January 23, 2008 31, 135–156. Heinzel, H., Weimann, J., and Marder, E. (1993). The behavioral repertoire of REFERENCES the gastric mill in the crab, Cancer pagurus: an in situ endoscopic and electro- physiological examination. J. Neurosci. 13, 1793–1803. Abbott, L.F., and Chance, F.S. (2005). Drivers and modulators from push-pull Higley, M.J., and Contreras, D. (2006). Balanced excitation and inhibition de- and balanced synaptic input. Prog. Brain Res. 149, 147–155. termine spike timing during frequency adaptation. J. Neurosci. 26, 448–457. Baca, S.M., Thomson, E.E., and Kristan, W.B. (2005). Location and intensity Holt, G.R., and Koch, C. (1997). Shunting inhibition does not have a divisive ef- discrimination in the leech local bending response quantified using optic fect on firing rates. Neural Comput. 9, 1001–1013. flow and principal components analysis. J. Neurophysiol. 93, 3560–3572. Kristan, W.B., Jr. (1982). Sensory and motor neurons responsible for the local Berg, R.W., Alaburda, A., and Hounsgaard, J. (2007). Balanced inhibition and bending response in leeches. J. Exp. Biol. 96, 161–180. excitation drive spike activity in spinal half-centers. Science 315, 390–393. Kristan, W.B., Jr., McGirr, S.J., and Simpson, G.V. (1982). Behavioral and Blitz, D.M., and Regehr, W.G. (2005). Timing and specificity of feed-forward in- mechanosensory neurone responses to skin stimulation in leeches. J. Exp. hibition within the LGN. Neuron 45, 917–928. Biol. 96, 143–160. 288 Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. Neuron Gain Control by Inhibition Kristan, W.B., Jr., Lockery, S.R., and Lewis, J.E. (1995). Using reflexive behav- Ort, C.A., Kristan, W.B., Jr., and Stent, G.S. (1974). Neuronal control of swim- iors of the medicinal leech to study information processing. J. Neurobiol. 27, ming in the medicinal leech part 2 identification and connections of motor neu- 380–389. rons. J. Comp. Physiol. 94, 121–154. Kuffler, S.W. (1953). Discharge patterns and functional organization of mam- Pouille, F., and Scanziani, M. (2001). Enforcement of temporal fidelity in pyra- malian retina. J. Neurophysiol. 16, 37–68. midal cells by somatic feed-forward inhibition. Science 293, 1159–1163. Lewis, J.E., and Kristan, W.B., Jr. (1998a). A neuronal network for computing Priebe, N.J., and Ferster, D. (2005). Direction selectivity of excitation and inhi- population vectors in the leech. Nature 391, 76–79. bition in simple cells of the cat primary visual cortex. Neuron 45, 133–145. Lewis, J.E., and Kristan, W.B., Jr. (1998b). Quantitative analysis of a directed Ribak, C.E., Harris, A.B., Vaughn, J.E., and Roberts, E. (1979). Inhibitory, behavior in the medicinal leech: implications for organizing motor output. J. GABAergic nerve terminals decrease at sites of focal epilepsy. Science 205, Neurosci. 18, 1571–1582. 211–214. Lockery, S., and Kristan, W., Jr. (1990a). Distributed processing of sensory in- Salinas, E., and Abbott, L.F. (1997). Invariant visual responses from attentional formation in the leech. I. Input- output relations of the local bending reflex. gain fields. J. Neurophysiol. 77, 3267–3272. J. Neurosci. 10, 1811–1815. Salinas, E., and Thier, P. (2000). Gain modulation: a major computational prin- Lockery, S.R., and Kristan, W.B., Jr. (1990b). Distributed processing of sen- ciple of the central nervous system. Neuron 27, 15–21. sory information in the leech II.Identification of interneurons contributing to Seutin, V., and Johnson, S.W. (1999). Recent advances in the pharmacology of the local bending reflex. J. Neurosci. 10, 1816–1829. quaternary salts of bicuculline. Trends Pharmacol. Sci. 20, 268–270. Lockery, S.R., and Kristan, W.B., Jr. (1991). Two forms of sensitization of the Shadlen, M.N., and Newsome, W.T. (1994). Noise, neural codes and cortical local bending reflex of the medicinal leech. J. Comp. Physiol. [A] 168, 165–177. organization. Curr. Opin. Neurobiol. 4, 569–579. Lucas, B.D., and Kanade, T. (1981). An iterative image registration technique Stent, G.S., Kristan, W.B., Jr., Friesen, W.O., Ort, C.A., Poon, M., and with an application to stereo vision (DARPA). Paper presented at: Proceedings Calabrese, R.L. (1978). Neuronal generation of the leech swimming movement of the 1981 Image Understanding Workshop. an oscillatory network of neurons driving a loco motory rhythm has been identified. Science 200, 1348–1357. Magloczky, Z., and Freund, T.F. (2005). Impaired and repaired inhibitory cir- cuits in the epileptic human hippocampus. Trends Neurosci. 28, 334–340. Stevens, C.F., and Zador, A.M. (1998). Input synchrony and the irregular firing of cortical neurons. Nat. Neurosci. 1, 210–217. Mamiya, A., Manor, Y., and Nadim, F. (2003). Short-term dynamics of a mixed chemical and electrical synapse in a rhythmic network. J. Neurosci. 23, 9557– Stuart, A.E. (1969). Excitatory and inhibitory motoneurons in the central ner- 9564. vous system of the leech. Science 165, 817–819. Stuart, A.E. (1970). Physiological and morphological properties of motoneur- Marin-Burgin, A., Eisenhart, F.J., Baca, M.S., Kristan, W.B., Jr., and French, ones in the central nervous system of the leech. J. Physiol. 209, 627–646. K.A. (2005). Sequential development of electrical and chemical synaptic con- nections generates a specific behavioral circuit in the leech. J. Neurosci. 25, Taylor, A.L., Cottrell, G.W., Kleinfeld, D., and Kristan, W.B., Jr. (2003). Imaging 2478–2489. reveals synaptic targets of a swim-terminating neuron in the leech CNS. J. Neu- rosci. 23, 11402–11410. Mason, A., and Kristan, W.B., Jr. (1982). Neuronal excitation, inhibition, and modulation of leech longitudinal muscle. J. Comp. Physiol. [A] 146, 527–536. Thomson, E.E., and Kristan, W.B. (2006). Encoding and decoding touch loca- tion in the leech CNS. J. Neurosci. 26, 8009–8016. McAdams, C.J., and Maunsell, J.H.R. (1999). Effects of attention on the reli- ability of individual neurons in monkey visual cortex. Neuron 23, 765–773. Vogels, T.P., and Abbott, L.F. (2005). Signal propagation and logic gating in networks of integrate-and-fire neurons. J. Neurosci. 25, 10786–10795. Misell, L.M., Shaw, B.K., and Kristan, W.B., Jr. (1998). Behavioral hierarchy in Wehr, M., and Zador, A.M. (2003). Balanced inhibition underlies tuning and the medicinal leech, Hirudo medicinalis: Feeding as a dominant behavior. Be- sharpens spike timing in auditory cortex. Nature 426, 442–446. hav. Brain Res. 90, 13–21. Wilent, W.B., and Contreras, D. (2005). Dynamics of excitation and inhibition Mittmann, W., Koch, U., and Hausser, M. (2005). Feed-forward inhibition underlying stimulus selectivity in rat somatosensory cortex. Nat. Neurosci. 8, shapes the spike output of cerebellar Purkinje cells. J. Physiol. 563, 369–378. 1364–1370. Moss, B.L., Fuller, A.D., Sahley, C.L., and Burrell, B.D. (2005). Serotonin mod- Wolfart, J., Debay, D., Le Masson, G., Destexhe, A., and Bal, T. (2005). Synap- ulates axo-axonal coupling between neurons critical for learning in the leech. tic background activity controls spike transfer from thalamus to cortex. Nat. J. Neurophysiol. 94, 2575–2589. Neurosci. 8, 1760–1767. Muller, K.J., Nicholls, J.G., and Stent, G.S. (1981). Neurobiology of the Leech Ye, M., and Haralick, R.M. (2000). Image flow estimation using facet model and (Cold Spring Harbor, NY: Cold Spring Harbor Laboratory). covariance propagation. In Vision Interface: Real World Applications of Com- Murphy, G.J., Darcy, D.P., and Isaacson, J.S. (2005). Intraglomerular inhibi- puter Vision, Y.H. Yang and M. Cheriet, eds. (Hackensack, NJ: World Scientific tion: signaling mechanisms of an olfactory microcircuit. Nat. Neurosci. 8, Pub Co), pp. 209–241. 354–364. Yokoi, M., Mori, K., and Nakanishi, S. (1995). Refinement of odor molecule tun- Nicholls, J.G., and Baylor, D.A. (1968). Specific modalities and receptive fields ing by dendrodendritic synaptic inhibition in the olfactory bulb. Proc. Natl. of sensory neurons in CNS of the leech. J. Neurophysiol. 31, 740–756. Acad. Sci. USA 92, 3371–3375. Nicholls, J.G., and Purves, D. (1970). Monosynaptic chemical and electrical Zoccolan, D., and Torre, V. (2002). Using optical flow to characterize sensory- connections between sensory and motor cells in the central nervous system motor interactions in a segment of the medicinal leech. J. Neurosci. 22, 2283– of the leech. J. Physiol. 209, 647–667. 2298. Neuron 57, 276–289, January 24, 2008 ª2008 Elsevier Inc. 289


text:
Dr. Hector M. De Leon, MD
Child & Adolescent Psychiatry, Advanced Behavioral Health Center
- 1799 Salk Ave
Tavares, FL 32778
- 1 Office Location
- Email a Friend
- (352) 742-8300
Dr. Hector M. De Leon has been practicing medicine for 20 years. Dr. De Leon graduated from the Universidad Central del Caribe School of Medicine in 1994. He practices medicine in Tavares, FL and specializes in Child & Adolescent Psychiatry and Psychiatry. Dr. De Leon speaks English and Spanish.
Gender: Male
Years in Practice: 20 Years
Languages Spoken: English, Spanish
Medical School: Universidad Central del Caribe School of Medicine
Graduation Date: 1994
Hospital Affiliations: Not Available
Specialties: Child & Adolescent Psychiatry, Psychiatry
©2005-2014 WebMD, LLC. All rights reserved.
WebMD does not provide medical advice, diagnosis or treatment. See additional information.


text:
Search results for kelly rowland
Mommy To Be Bangers: Kelly Rowland Puts Her Bare Bump On Blast For ELLE Magazine
Kelly's got that good ole gut full glow!
On The Come Up? Kelly Rowland Campaigning To Play Donna Summer In New Spike Lee Flick
Could Kelly pull off this role?
Fetal Fitness: Baby Bumpin' Kelly Rowland Hits The Gym
Kelly is making sure that body stays right after the baby!
Hollyweird Sightings At Jay-Z & Beyonce's Tour In Cali: Pregnant Kelly Rowland, Miguel & His Girl, EJ Johnson, Sanaa Lathan, And More [Video]
Everybody and their mom came out to see Beyonce and Jay-Z in Pasadena California.
On The Run: Kelly Rowland, E.J. Johnson, Amber Rose, Miguel, Vanessa Bryant And More Hit Up Beyoncé And Jay Z's Rose Bowl Show [Photos]
Pasadena's Rose Bowl was the place to be Sunday night.
Sweet Black Love: Kelly Rowland Gushes About Her Gut Full Of Doting Husband Tim Witherspoon
Sounds like she's doing better than Beyonce…for once
Bumpin' Around: Mommy-To-Be Kelly Rowland Flosses Her Big Ol' Baby Belly In Cut Up Tee
We are loving Kelly Rowland's pregnant glow and great energy…
Gut Full Glow: Kelly Rowland Shares Makeup Free Pregnancy Selfie
Kelly wears pregnancy well…
The Bump: 12 Kelly Rowland Pregnancy Moments
Look at beautiful bump…


text:
I can't speak to your tastes, but smooth vocals that are used to paint vivid pictures over a simple yet effective guitar-reliant beat is Perfect For Me. Good thing Mike Stud has all that and more on his brand new single. The Rhode Island native tracks the progression of his relationship with a hipster chick, who judging from the song's video, is definitely wifey material. With Julkeyz's summery production behind him, Stud showcases how his muse inspires him with some dope wordplay like "We be going Mia Hamm in bed/word to Nomar" or the A$AP/Chainz-like line "too f**king young for all that/were just young and f**king". The latter one-liner, used to describe their non-committal relationship, is something Stud seems to forget, as he gets in deeper and deeper, which as many of you are aware can only lead to bad things. To find out exactly what happens, though, you'll have to watch the video. Afterward, feel free to check out Stud's last Booth feature, July's You Don't Know Me.
Mike Stud Music VideosDownloadsR&B/PopIndie
Written by Lucas G. on 02/19/13
Submit your Rating
First DJ Booth Appearance:
"Is It Worth It" (2012)
Total DJ Booth Features:
8 Songs
You Might Like...
Commentsblog comments powered by Disqus
- Heat Check: How Do You Feel About Drake's "How About Now"
- 10 Must Have Hip-Hop Downloads of the Week (10/17)
- Freddie Gibbs x Madlib ft. Action Bronson, Joey BadA$$ & Ransom - Knicks (Remix)
- All 79 Things Chance the Rapper Hates on "No Better Blues"
- Lupe Fiasco ft. Sirah - Lilies
- ShayGray - No Sense of Accomplishment
- F*ck Norms: Why the Critics Are Wrong About Yung Lean
- Lorenzo Asher, The Director #TopProspects
- All 72 of Drakes Billboard Top 100 Songs
- DJBooth Announces Our New Top Prospects…
- The Best Hip-Hop & R&B Songs of 2014 (Ongoing)
DJBooth TV
Discover the best new songs, videos, and albums added to the Booth.