text:
Serviços Personalizados
Links relacionados
- Citado por Google
- Similares em Google
South African Journal of Science
versão On-line ISSN 1996-7489
versão impressa ISSN 0038-2353
S. Afr. j. sci. vol.104 no.7-8 Pretoria Set./Ago. 2008
Predicting action potential characteristics of human auditory nerve fibres through modification of the HodgkinHuxley equations
J.E. Smit; T. Hanekom‡; J.J. Hanekom
Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria 0002, South Africa
In 1952, Hodgkin and Huxley published an empirical set of equations describing changes in the neural membrane potential of the squid giant axon during the application of depolarizing or hyperpolarizing stimuli. As these equations were derived for an unmyelinated nerve fibre, there are reservations about their applicability to describe action potential propagation adequately in myelinated mammalian nerve fibres. This study proposes possible modifications of the HodgkinHuxley equations to describe action potentials generated in the Ranvier node of a human sensory nerve fibre, as applied specifically to the prediction of temporal characteristics of the human auditory system. Simulations of the effects of these modifications were performed in Matlab. Results suggest that the temporal characteristics of the human auditory system may be predicted better by using the modified set of equations. This finding is of value in creating more realistic neural models of the electrically stimulated human auditory system. Refractory periods were similar to those of general sensory nerve fibres of the same calibre. Relative refractory periods decreased with progressive retrograde nerve fibre degeneration. Chronaxie times decreased and rheobase current values increased when retrograde nerve fibre degeneration was simulated. Rheobase currents were also greater for straight array compared with contour array stimulation. Mean latencies decreased with progressive retrograde nerve fibre degeneration and agreed well with neural response telemetry. They also decreased with an increase in stimulus intensity.
Cochlear implants have been devised to help rehabilitate profoundly deaf persons by providing them with a measure of sound perception through electrical stimulation of auditory nerve fibres (ANFs). The cochlear implant injects electrical currents directly into the cochlea by means of an electrode array to stimulate the ANFs. The challenge facing researchers is how to convey meaningful speech information to the brain via electrical stimulation. In particular, a better understanding of the way the implanted auditory system decodes the temporal information carried in speech needs to be gained before improved implants can be developed. The primary means of modelling the implanted human ear is using mammalian research animals, especially cats and guinea-pigs (see, for example, Abbas and Miller1 and Javel et al.2). Since these animals' cochleae have larger dimensions than those of smaller rodents, multi-electrode arrays similar to those implanted in humans can be used. Computational models are employed in combination with animal studies to enhance understanding of the underlying physiology of electrical hearing.1 Several ANF models have been developed,38 which are frequently used in combination with volumeconduction models of the cochlea to predict neural excitation profiles.4,9,10 An advantage of the computer models is that it is possible to isolate and manipulate critical model parameters, as well as modelling the differences in cochlear anatomy and ANF physiology between species, which is not always feasible with animal studies.11 Most of these models are at least partially based on animal data. However, the differences in cochlear structures between animals and humans, differences in the number and percentage myelination of auditory nerve fibres, and innervation patterns of both inner and outer hair cells across species, may be physiologically significant and care must be taken when extrapolating the animal results to predict performance in human implantees.12,13 Computer models can only approximate a real neural system, owing to the complexity of the latter. The modeller therefore has to make certain simplifying assumptions when abstracting the real system and this places limitations on the model as to the realistic correctness and completeness of the physiology and anatomy represented.11 A more comprehensive computer model based on human cochlear dimensions and peripheral auditory nerve fibre characteristics is therefore needed.
Frijns et al.4,14,15 developed a model based on the Schwarz-Eikhof nerve fibre model for the rat,16 but adapted with guinea-pig morphometry. Recently, this Generalized Schwarz-Eikhof-Frijns (GSEF) model was adapted for human ANF simulations by employing human morphometric data only.5,17 The ionic current dynamics of this model, however, are still those of the rat. Even though there are similarities between the properties of ionic currents at the rat and human Ranvier node,18,19 differences such as those in the activation and deactivation characteristics of voltage-gated potassium ion (K+) channels can result in discrepancies in the predictive behaviour of nerve fibre conduction.20
A comparison of the applicability of models of squid,21 toad,22 rabbit23 and rat16 to predict excitability of human auditory nerve fibres favours the HodgkinHuxley (HH) model for squid, provided the nodal ion channel kinetics are accelerated tenfold.24,25 This modified HH model improves the prediction of human auditory nerve fibre responses, as well as a superior prediction of chronaxie time of 340 µs versus 1545 µs of the Frijns model,26 by changing the cable morphometric properties to those of the human.6 Huxley27 also suggested that the HH model can be modified to represent firing behaviour at a Ranvier node by accelerating the activation and inactivation of membrane sodium ion permeability fourfold.
The study reported here proposes modifications to the HodgkinHuxley equations to describe action potentials generated at the Ranvier node of a human sensory nerve fibre, with the objective of enhancing the prediction of temporal characteristics of the human peripheral auditory system. The nerve fibre model consists of two partsa cable model based on a combination of the models by Rattay et al.6 and Blight,28 together with the newly modified HH model which describes the propagating action potential dynamics at the Ranvier nodes.29 The architecture of the new model was derived in two phases. First, the HH model was modified using human physiological data from the literature; and second, the combined cable model was constructed using published human sensory nerve fibre morphometric data. The model was validated against experimental results from the literature. Lastly, the morphometric parameters of the nerve fibre model were changed to a Type I peripheral auditory nerve fibre (ANF) and coupled to a volume-conduction model of the cochlea.
The human Ranvier node model
The human nodal model was based on the original HH model21 for unmyelinated nerve fibre dynamics. The HH model's ionic membrane current (Iion) is described in terms of the Na+, K+ and leakage (L) ionic conductances,
The dynamics of the opening probabilities (m, h and n, respectively) of the ion channels are described by
with αx(V) and βx(V) the voltage-dependent opening and closing rates of the ion channels, which give an indication of the membrane's permeability to the specific ion species [refer to Equation (A8) in the appendix]. Although these equations describe the time dependence of the action potential, the temperature dependence of the equation parameters is ignored in the original HH model.
The above equations were modified by changing the parameter values describing the ionic and leakage conductances, corresponding equilibrium potentials, the membrane rest potential and capacitance, and axoplasmic resistance to reflect those of the human, as well as to include the temperature dependence of the parameters. Conductance and equilibrium potential values were deduced from experimental studies by Scholz et al.,30 Reid et al.31 and Schwarz et al.32 As these studies were performed at different temperatures and using different Na+ and K+ ion concentrations in intra- and extracellular replacement Ringer's solutions, all values had to be corrected for temperature and concentration differences. Temperature dependence of the resting membrane potential (Vres) was expressed through the use of a Q10 factor, with a value of 1.036 for all T < 20°C and 1.035 for all T > 20°C. Membrane permeability of the different ion species was increased or decreased by multiplying the rate equations αx(V) and βx(V) by selected factors. The temperature dependence of the permeability, as expressed through Q10 factors, also differed from the HH model. Electrical parameters were recalculated as values per unit area by assuming a fibre diameter of 15 µm and nodal area of 50 µm2.33 A nodal membrane capacitance (Cm) of 1.4 pF, i.e. 2.8 µF cm2, was used.32 Palti and Adelman34 found a positive temperature coefficient of about 1.36% per °C, in the temperature range 321°C for Cm of squid, no significant change in Cm in the range 2142°C, and a sharp increase of at least 23% per °C for temperatures above 42°C. No similar studies have apparently been conducted on mammals, and thus the assumption was made that Cm would be constant in the temperature range 2037°C. The shape and amplitude of the action potential were not dependent on the axoplasmic resistivity (ρax) and a value of 0.25 Ω.m at 37°C was used.35 Schwarz et al.32 measured the ionic membrane currents and action potentials at the Ranvier node in partially demyelinated human peripheral nerve fibres. However, no morphometric nerve fibre data were given. By assuming a fibre diameter of 15 µm and a nodal area of 50 µm2, the rise and fall times and amplitudes at 20 and 25°C could be estimated from the action potential plots and used for model validation.33
The nerve fibre cable model
The human nerve fibre model was based on the cable model of Rattay,6 which assumed a propagating action potential driven by HodgkinHuxley dynamics,21 but was modified to a simple double cable structure. Two nerve fibre types were modelled: 1) a general sensory nerve fibre consisting only of an axon, and 2) a Type I auditory nerve fibre, which consisted of a dendrite, soma and axon. The dendrite and axon were divided into k cylindrical compartments, with the axon diameter about twice that of the dendritic diameter.
General sensory nerve fibre model. The change in the membrane potential (Vk) at the centre of the k-th compartment was described by the cable equation
The membrane potential is given by Vk = Vi,k Ve,k Vres, with Vi,k the intracellular potential, Ve,k the extracellular potential and Vres the resting membrane potential. Cm,k gives the membrane capacitance and Rk the axoplasmic resistance to the neighbours at the k-th compartment. Externally applied stimulation is incorporated through the external potential field (Ve). For the general sensory nerve fibre, Ve was calculated by stimulation with a monopolar external electrode positioned sufficiently far away from the nerve fibre that the external potential field did not distort the propagating action potential.
The Ranvier nodes were considered unmyelinated active axolemmae using the new human Ranvier node model dynamics. Both Rk and Cm,k were temperature dependent. Rk is a function of ρax and the action potential's conduction velocity (vc) depends significantly on the latter.36 Schalow et al.37 classified human peripheral sensory nerve fibre groups by conduction velocity and fibre diameter and determined vc values of about 64.0 m/s for fibres having a diameter of 15.0 µm and about 10.0 m/s for 3.04.0-µm-diameter fibres at body temperature. A value of 0.25 Ω.m at 37°C for ρax and (1.35)1 for its corresponding Q10 factor were selected to give a vc value of 56.5 m/s at 37°C for a 15.0-µm-diameter axonal fibre stimulated with a monopolar external electrode positioned 10.0 mm from the fibre.
The myelinated internodes were simple double cable structures as modelled by Blight,28 who considered the leaky myelin sheath and axolemma to be combined together in series, having a high resistance and low capacitance. Just as in the Rattay et al.6 model, the ionic membrane currents under the myelin sheath were ignored, leading to the assumption of constant internodal membrane conductance. The full set of equations and parameter values for the auditory nerve fibre cable model are listed in the appendix.
The auditory nerve fibre model. The Type I human ANF model was based on the cable model of Rattay et al.,6 but with the axon replaced with the generalized human sensory nerve fibre model. The dendrite and axon are divided into cylindrical compartments, whereas the soma is assumed to be spherical.6 The nerve fibre morphology is shown in Fig. 1. An additional modification to the ANF model was a shortening of the dendrite to fit the somal position of its counterpart in the volume-conduction cochlear model. Two types of Type I spiral ganglion cells exist with somal diameters varying between 24.6 µm and 29.9 µm.38,39 A value of 27.0 µm was thus assumed in the model.
Ranvier nodes were unmyelinated active axolemmae with only the axon based on the general sensory nerve fibre model. SEM photographs and measured human auditory myelinated large Type I nerve fibres indicate an average fibre diameter of about 3.35 µm across the range from basal to upper middle cochlear turns, and an axonal diameter of 2.34 µm.38,40 This gives a fibre-to-axon diameter ratio of 0.7, in agreement with values ranging from 0.630.8, depending on the fibre thickness.41 The relationship between fibre diameter and internodal length that was used in the model, however, was only valid for fibre diameters greater than 3.4 µm.33 As the largest diameter in the basal turn described in the Rosbe et al.38 study was 4.3 µm and the smallest in the upper middle turn 3.2 µm, the average, being 3.75 µm, was assumed in the ANF model.
Modelling the degenerate nerve fibre. Retrograde neural degeneration, in which the dendrites are lost but the somas and axons survive, occurs in persons with profound sensory hearing loss.39,42 The degree of retrograde neural degeneration depends on the severity of tissue alterations in the Organ of Corti during the original insult and concerns only Type I ANFs.39
Since not all ANFs are affected by this phenomenon, both an unaffected (non-degenerate) ANF and an affected (degenerate) ANF were considered in this study. A degenerate version of the ANF model, similar to Frijns et al.43 and Briaire and Frijns,17 was used to simulate the effect of neural degeneration, that is, to simulate a nerve fibre with almost no peripheral (dendritic) process. This was effected by removing the first four nodal and internodal sections of the modelled ANF (refer to Fig. 1). The first node in the degenerate version of the ANF model thus corresponded to node n5 in Fig. 2. An axon-only version was also modelled to simulate retrograde degeneration observed in long-term profoundly deaf persons39 by removing all dendritic nodes and internodes up to and including the soma in the ANF model.
The volume-conduction cochlear model
The ANF model was coupled to a 3D spiralling finite element volume-conduction model of the first one-and-a-half turns of the electrically stimulated human cochlea (Fig. 2). For more details of the volume-conduction model, refer to Hanekom.9 Each of the nerve fibres present in the model was described by the ANF model equations, where node n1 in Fig. 2 was the first node of the nerve fibre. The external potential (Ve) used to stimulate the ANFs was calculated from the output from the volume-conduction cochlear model.
The cochlear model is designed to allow two possible electrode array positions, one medial and one lateral, relative to the modiolus. The Nucleus 24 straight array, which, after implantation, is positioned close to the outer wall of the cochlea,44 is modelled with the lateral array, whereas the contour array, which lies close to the modiolus,44,45 is modelled with the medial array. The straight array was modelled with full-band electrodes and the contour array with half-band electrodes.44,46 The modelled cochlea was stimulated with a monopolar electrode configuration of the straight and contour arrays, respectively, with the electrode located in the basal cochlear turn.
Model output calculations
All calculations were performed in Matlab 7. Differential equations were numerically solved using the ode15s numerical solver. This means was selected because the modified equations proved to be too stiff to solve using the ode45 and ode23t solvers.
The action potential (AP) was characterized by its amplitude and rise and fall times. Frijns et al.14 approximated the action potential as a triangle, with the apex at the maximum amplitude and the rising and falling edges cutting the action potential curve at 10% of the maximum amplitude.
Stimulation pulses were square monophasic. The human Ranvier node model was developed to be stimulated internally and externally. During the development and optimization procedures, the modelled Ranvier node was stimulated internally. An anodic pulse was used to depolarize the membrane to create an AP having the same characteristics as the AP measured by Schwarz et al.32 To aid comparison of AP characteristics between the Ranvier node and nerve fibre models, the same pulse was used to optimize the nerve fibre models. Anodic pulse stimulation of all models was therefore performed.
The external environments of the human Ranvier node and nerve fibre cable models were considered infinite, isotropic and homogeneous with an external resistivity (ρe) of 0.3 kΩ.cm at 37°C.26 External stimulation was thus considered purely resistive and given by
with rdist the distance between the node and the electrode. The external environment of the ANF model consisted of the cochlear model, with all cochlear tissues considered purely resistive.
Strengthduration behaviour was characterized by the rheobase current and chronaxie time. Thresholds were calculated using either the monopolar external electrode or the output from the volume-conduction model as external stimulation, depending on the nerve fibre under consideration. Stimulation pulses were square monophasic and ranged from 0.22.0 ms in duration. The strengthduration curve was fitted with the linear relationship
with Ith the threshold current (µA), t the pulse duration (µs), Irb the rheobase current (µA) and τch the chronaxie time (µs).33,47,48
The absolute (ARP) and relative (RRP) refractory periods characterized the way the nerve fibre will behave in a refractory manner. The nerve fibre was initially stimulated with a 0.1 ms monophasic pulse with amplitude 20% above Ith. Stimulation with a second 0.1 ms monophasic square pulse resulted in a second propagating action potential. The absolute refractory period was defined as the maximum interval between the two pulses in which no second pulse, with amplitude of up to 400% Ith, could be elicited. The relative refractory period was the minimum interval between the two pulses in which an impulse of at most 101% Ith was required to elicit the second pulse.33
Simulations based on the human Ranvier node model, as well as the nerve fibre cable models, were performed in Matlab. External stimulation of the Node of Ranvier and the general sensory nerve fibre models was provided by a monopolar external electrode, whereas for the ANF model the external potential distribution inside the cochlea was calculated with a volume-conduction cochlear model stimulated with Nucleus 24 straight and contour electrode arrays, respectively.
The human Ranvier node model
The modelled rise and fall times of the AP were calculated at 20 and 25°C and compared with experimentally estimated results (Table 1). An example of sub-threshold and supra-threshold action potentials simulated at 25°C is shown in Fig. 3. Rise times were 0.4% and 0.5% longer at 20 and 25°C, respectively, than the experimental values, whereas the fall times were 2.2% longer and 1.1% shorter, respectively. No experimental values were measured at 37°C, but values of 120 µs rise time and 470 µs fall time were previously predicted (Table 2). Comparison with these values indicated a 2.5% longer rise time and a 67% longer fall time for the human nodal model. The rise time decreased by 24% from 20 to 25°C, corresponding to a Q10 factor of (1.73)1, while the fall time decreased by 23% [Q10 factor of (1.67)1]. This decrease in the fall time is steeper than the estimated 20% decrease [Q10 factor of (1.56)1] of the experimental results.
Simulated action potential amplitudes were just below 117 mV at 20 and 25°C and also just below 115 mV at 37°C, following the accepted trend of an amplitude decrease with rise in temperature.26,33
The nerve fibre cable model
Rise and fall times of the general sensory nerve fibre cable model simulated at 37°C were 4.2% shorter and 60.0% longer than the previously published results predicted (Table 2). AP amplitudes were around 2 mV lower than those of the Ranvier node model at the respective temperatures.
The conduction velocity (vc) for the 15.0 µm nerve fibre was 12.4% lower (56.5 m/s) than the 64.5 m/s predicted by the Wesselink model and experimental results.37 Conduction velocities showed a fibre diameter dependency, decreasing with a reduction in fibre diameter (Fig. 4). Values compared well with those measured by Schalow et al.37 for fibre diameters thicker than 12.5 µm, but vc values were underestimated for thinner fibres. To aid comparison of vc values of fibres of different diameter, it is customary to list these values in terms of vc per fibre diameter,33 as listed in Table 2.
Chronaxie times (τch) were calculated for fibre diameters from 5.0 to 15.0 µm (Fig. 5). Stimulation was performed with a single external monopolar electrode positioned 10.0 mm from the fibre. Pulses were monophasic and ranged from 0.22.0 ms in duration. τch values were in the same range, but 3.526.2% shorter than the Wesselink model33 results. Unlike the latter,33 however, τch values did not decrease monotonically with increase in fibre diameter, but rose again for diameters larger than 10.0 µm (Fig. 4). Reasons for this are unclear and require further investigation.
Refractory periods were calculated for a 15.0-µm-diameter fibre and were similar to refractory periods previously calculated for a 10.0-µm fibre (Table 2).
A 3.75-µm-diameter degenerate ANF fibre located in the basal cochlear turn was stimulated with a monopolar electrode configuration from either the contour or straight electrode arrays. Stimulation pulses were square and monophasic. All simulations were performed at 37°C.
For an axon-only nerve fibre stimulated with the contour array, a rise time of 144 µs and a fall time of 749 µs at 37°C were calculated. The rise time was 17% shorter and the fall time was 14.7% longer than for a similar general sensory nerve fibre. Results for the straight array were similar to those for the contour array.
Chronaxie times were calculated for stimulation with the contour and straight arrays, respectively, by fitting the strength duration curves with the linear Weiss relationship.
Strengthduration curves were also fitted with the exponential relationship of Lapicque,49 but the Weiss relationship provided a better match. Figure 6 shows the curves for non-degenerate and axon-only ANFs plotted as threshold charges for contour array stimulation. The curve for a degenerate ANF is similar to the non-degenerate curve and is omitted for clarity. In general, τch values decreased with a modelled increase in fibre degeneracy as shown in Table 3. Calculated τch values for contour and straight arrays predicted about 10% higher values in the former case compared with the latter for non-degenerate and degenerate fibres, whereas values for the axon-only fibres were similar. A τch value of about 86.1 µs was calculated for an axon-only fibre, irrespective of the electrode array used. As τch values increase with a decrease in fibre diameter, this time is shorter than the chronaxie time would be for the same fibre when stimulated with an external electrode. τch values also decrease when the electrode to fibre distance decreases.1,33 In contrast, stimulation with the contour array resulted in longer τch values than with the straight array (Table 3).
Simulations predicted a rheobase current of 0.77 mA for a non-degenerate, 0.79 mA for a degenerate, and 0.81 mA for an axon-only fibre when stimulated with the contour array. Rheobase current values for straight array stimulation were about two-and-a-half times higher than for contour array stimulation.
Simulated ARP values compared well and were similar to those of general sensory nerve fibres, being 800900 µs irrespective of the electrode array used for stimulation (compare Tables 2 and 3).
Simulated RRP values differed, depending on the stimulation array used. Values for axon-only, degenerate and non-degenerate fibres are listed in Table 3. For a non-degenerate fibre the RRP value was 6% longer than for a degenerate fibre when stimulated with the straight array, and 5% longer when stimulated with the contour array, whereas they were about 3% longer for stimulation with the latter array.
Conduction velocities and latencies were determined for monopolar stimulation with a monophasic pulse of 0.5 ms. Calculated vc values for an axon-only fibre were 12.8 m/s (contour array) and 10.4 m/s (straight array) compared to 9.0 m/s for a similar general sensory nerve fibre externally stimulated. vc values per fibre diameter are listed in Table 3. For a degenerate fibre, vc values were about 43% slower than for stimulation of an axon-only fibre for contour array stimulation and about 30% slower for straight array stimulation. Non-degenerate fibre vc values were 3% faster than for degenerate fibres for contour array stimulation and about 11% faster for straight array stimulation.
ANF performance is not measured in terms of vc values and hence these results were translated into propagation times and latencies. AP propagation time is defined as the time taken by the AP to travel the length of the modelled ANF. These propagation times for full, degenerate and axon-only fibres, respectively, were 0.49 ms, 0.30 ms and 0.13 ms for contour array stimulation, and 0.45 ms, 0.30 ms and 0.163 ms for straight array stimulation. Latencies for degenerate ANF fibres were about 22% longer with contour versus straight array stimulation. Comparison between latencies of non-degenerate and degenerate ANF fibres predicted an approximate 52% reduction irrespective of electrode array used.
Discussion and conclusion
This study presents a new model to simulate the human Type I auditory nerve fibre. The Ranvier node membrane dynamics were based on the HodgkinHuxley model, modified with human physiological and morphometric data from experimental studies by Scholz et al.,30 Reid et al.31 and Schwarz et al.32 The new model was a simple double cable structure based on models by Rattay6 and Blight,28 together with additional morphometric data from the literature. Two versions of the cable model are presented, namely a general myelinated sensory and a Type I ANF model.
There are no experimental results regarding the fall and rise times, nor of the conduction velocity of the propagating AP in auditory nerve fibres. Instead, these fibres are classified in terms of temporal characteristics, including ARP and RRP properties, strengthduration behaviour and conduction latencies (see, for example, a review by Abbas and Miller1). All these characteristics depend, in part, on the type and strength of the stimulation pulse, the electrode configuration and electrodefibre distance.1 In this study stimulation of the modelled cochlea was performed with two different Nucleus 24 electrode arrays in monopolar configuration, with the contour array positioned closer to the axonal part of the nerve fibres than the straight array. Stimulation pulses were square monophasic.
Stimulation in cochlear implants typically takes the form of pulse trains or continuous stimulation. The refractory properties of the neural membrane play an important role in the choice of stimulation used.1 First, it places a lower limit on the inter-phase/ inter-pulse interval, raising the threshold stimulus intensity needed to elicit further responses during the RRP, and second, it places an upper limit on the stimulus rate used.1 Mean ARP values between 0.33 ms50 and 0.7 ms51 and a mean recovery time constant of about 0.41 ms were estimated for cat auditory fibres50 and an RRP of up to 5 ms.1,51 Electrically evoked compound action potential (ECAP) studies on humans suggest an ARP value greater than 0.5 ms and an RRP value around 5 ms.52 These values are 41% shorter for the ARP and 72% longer for the RRP than the new model for a degenerate fibre predicts. Compared to ARP and RRP values for human sensory nerve fibres, however, the new model may predict refractory properties better than the cat models.
Although the somas and axons of the Type I ANF fibre degenerate at a slower rate than the dendrites, SEM studies of long-term profoundly deaf persons show a sharp decrease in the number of surviving fibres, compared with people who have been deaf for less time.39 Model predictions suggested that retrograde degeneration may not influence the ARP of ANFs, but this prediction has not been studied experimentally. The simulated RRP results for a non-degenerate fibre were longer than for degenerate and axon-only fibres, possibly suggesting that long-deaf persons may benefit from implants employing faster stimulation rates than for recently deaf people.
Latency measurements on cats with normal hearing and those in which the dendrites and somas were removed during a cochlear laminectomy, showed a double peak response in the normal-hearing cats, whereas in the laminectomated cats only the first response peak appeared.53 Van den Honert and Stypulkowsky53 proposed that the former reflected peripheral dendritic excitation and that the change in latency indicated a shift in excitation to a more centrally located site along the fibre. More recent ECAP studies on cats also suggested this proposition.50,5456 Neural telemetry response (NRT) measurements in human subjects implanted with the Nucleus 24 arrays indicated the existence of similar response waveforms having either single positive or double positive peaks.57 The NRT waveform is characterized by a negative (N1) peak, followed by the positive peak(s) (P1 and P2). For a single positive peak waveform, the N1 peak occurred around 0.30.4 ms and the P1 peak around 0.60.7 ms. In the double positive peak responses, the N1 peak occurred at times too short to measure with the NRT system (<0.11 ms), whereas the P1 and P2 peaks occurred around 0.40.5 ms and 0.60.7 ms, respectively. Calculated latencies for the single-peak case are hence ~0.3 ms. For the double-peak case, it is ~0.4 ms and ~0.7 ms, whereas the resulting propagation times range between 0.2 and 0.3 ms. Lai and Dillier57 concluded that the double-peak response indicated the existence of almost intact ANF fibres, whereas the single-peak response might be due to retrograde degeneration. Latencies calculated for single fibres with the present human ANF model for degenerate fibres were in agreement with the suggestion that longer latencies indicate dendritic presence and stimulation of more intact ANFs, owing to the additional time it takes the AP to propagate along the fibre.
The strengthduration function gives the relationship between the threshold stimulus current necessary to excite a fibre and the stimulus duration. Strengthduration behaviour is characterized by the rheobase current and chronaxie time. Strengthduration curves measured for normal and damaged cat auditory nerve fibres show that for the damaged fibres, where only the axons are left intact, thresholds at short pulse durations appear lower than for the normal fibres (refer to Fig. 5 of van den Honert and Stypulkowsky53). However, the recording electrodes used for the damaged fibres were placed closer to the axons than in the case of recordings from normal fibres. If the recording sites were kept the same for both cases, thresholds measured for damaged fibres would be higher than for normal fibres. This is most probably because the damaged fibres are only excited in the axonal (central) part of the fibre, while for normal fibres excitation could occur either peripherally or centrally and the peripheral process is closer to the electrodes.53 Simulations with the present model predicted higher rheobase values for axon-only fibres compared to degenerate and non-degenerate fibres. Values were also higher for straight array stimulation compared to contour array stimulation. However, the rheobase value calculated for a non-degenerate ANF fibre stimulated with the contour array was lower than for straight array stimulation. Because both types of stimulation activated the fibre in the dendritic process, however, this was contrary to the expected trend of similar values for dendritic excitation, which can be attributed to the model itself. In the Methods section, mention was made of the fact that the relationship between fibre diameter and internodal length that was used in the axonal part of the modelled fibre was only valid for fibre diameters greater than 3.4 µm. The dendritic diameter is only 1.0 µm, hence the dendritic section of the fibre could not be replaced with the general sensory nerve fibre dynamics. Because of the difference in dynamics between the original Rattay6 model and the general sensory nerve fibre model, we expect that the present ANF model's excitation behaviour will differ from a model where the squid dynamics of the dendritic as well as the somal sections are also replaced with human dynamics.
Van den Honert and Stypulkowsky53 reported significantly shorter (118 µs versus 276 µs) chronaxie times for fibres from which the dendrites and somas were removed (leaving only the axons intact) compared to normal functioning fibres, indicating axonal excitation in the former. In both cases the fibres were electrically stimulated. Although the chronaxie time of 86.1 µs for an axon-only simulated fibre is much shorter than for a similar general sensory human fibre, chronaxie times decreased as the modelled fibre became progressively more degenerated.
According to Abbas and Miller,1 chronaxies depend on the electrodeaxon distance. A closer separation may lead to a decrease of the strengthduration time constant and thus shorter chronaxies. The trend predicted by the present model was in contrast to the experimental observation that the chronaxie times for non-degenerate and degenerate fibres increased when the electrodefibre distance was reduced, confirming the shortcoming in the model regarding dendritic modelling discussed previously.
In myelinated nerve fibres the total nodal sodium current (INa) is subdivided into two functionally distinct currents. The largest proportion (~98%) has fast activating and inactivating kinetics and is referred to as a transient (INat) current. The smaller portion (~2%) activates equally fast, but at membrane potentials 1020 mV more negative than the transient, and inactivates slowly or not at all, thus forming a persistent (INap) current.58 Bostock and Rothwell59 developed a model similar to the one by Schwarz et al.32 having only INat. They estimated a chronaxie time of 176 µs at 37°C. The model was then changed to include a 2.5% INap activated at 1020 mV more negative than INat. The chronaxie time then increased to 535 µs. The new ANF model is in part based on parameters from Schwarz et al.32 and hence simulates INat. Although the model results are in fair agreement with experimental results, addition of INap should give even more realistic predictions.
In conclusion, it seems possible to modify the Hodgkin Huxley equations to describe action potentials generated in the Ranvier node of a human sensory nerve fibre and apply these modifications to create more realistic neural models of the electrically stimulated human auditory system. However, the squid-based dynamics of the dendritic and somal sections of the fibre model need to be replaced with human dynamics to account more fully for experimentally observed ANF excitation behaviour.
1. Abbas P.J. and Miller C.A. (2004). Biophysics and physiology. In Cochlear Implants: Auditory prostheses and electric hearing, eds F-G. Zeng, A.N. Popper and R.R. Fay, pp. 149212. Springer-Verlag, New York. [ Links ]
2. Javel E., Tong Y.C., Shepherd R.K. and Clark G.M. (1987). Responses of cat auditory nerve fibers to biphasic electrical current pulses. Ann. Otol. Rhinol. Laryngol. 96, 2630. [ Links ]
3. Bruce I.C. et al. (1999). A stochastic model of the electrically stimulated auditory nerve: single-pulse response. IEEE Trans. Biomed. Eng. 46, 617629. [ Links ]
4. Frijns J.H.M., Briaire J.J. and Schoonhoven R. (2000). Integrated use of volume conduction and neural models to simulate the response to cochlear implants. Simpra 8, 7597. [ Links ]
5. Briaire J.J. and Frijns J.H.M. (2005). Unraveling the electrically evoked compound action potential. Hear. Res. 205, 143156. [ Links ]
6. Rattay F., Lutter P. and Felix H. (2001). A model of the electrically excited human cochlear neuron I. Contribution of neural substructures to the generation and propagation of spikes. Hear. Res. 153, 4363. [ Links ]
7. Matsuoka A.J., Rubinstein J.T., Abbas P.J. and Miller C.A. (2001). The effects of interpulse interval on stochastic properties of electrical stimulation: models and measurements. IEEE Trans. Biomed. Eng. 48, 416424. [ Links ]
8. Macherey O., Carlyon R.P., van Wieringen A. and Wouters J. (2007). A dual-process integrator-resonator model of the electrically stimulated human auditory nerve. J. Assoc. Res. Otolaryngol. 8, 84104. [ Links ]
9. Hanekom T. (2001). Three-dimensional spiraling finite element model of the electrically stimulated cochlea. Ear Hear. 22, 300315. [ Links ]
10. Rattay F., Leao R.N. and Felix H. (2001). A model of the electrically excited human cochlear neuron. II. Influence of the three-dimensional cochlear structure on neural excitability. Hear. Res. 153, 6479. [ Links ]
11. Morse R.P. and Evans E.F. (2003). The sciatic nerve of the toad Xenopus laevis as a physiological model of the human cochlear nerve. Hear. Res. 182, 97118. [ Links ]
12. Frijns J.H.M., Briaire J.J. and Grote J.J. (2001). The importance of human cochlear anatomy for the results of mod iolus-hugging multichannel cochlear implants. Otol. Neurotol. 22, 340349. [ Links ]
13. Nadol Jr J.B. (1988). Comparative anatomy of the cochlea and auditory nerve in mammals. Hear. Res. 34, 253266. [ Links ]
14. Frijns J.H.M. and ten Kate J.H. (1994). A model of myelinated nerve fibres for electrical prosthesis design. Med. Biol. Eng. Comput. 32, 391398. [ Links ]
15. Frijns J.H.M., de Snoo S.L. and Schoonhoven R. (1995). Potential distributions and neural excitation patterns in a rotationally symmetric model of the electrically stimulated cochlea. Hear. Res. 87, 170186. [ Links ]
16. Schwarz J.R. and Eikhof G. (1987). Na currents and action potentials in rat myelinated nerve fibres at 20 and 37°C. Pflügers Arch. 409, 569577. [ Links ]
17. Briaire J.J. and Frijns J.H.M. (2006). The consequences of neural degeneration regarding optimal cochlear implant position in scala tympani: a model approach. Hear. Res. 214, 1727. [ Links ]
18. Safronov B.V., Kampe K. and Vogel W. (1993). Single voltage-dependent potassium channels in rat peripheral nerve membrane. J. Physiol. (Lond.) 460, 675691. [ Links ]
19. Röper J. and Schwarz J.R. (1989). Heterogeneous distribution of fast and slow potassium channels in myelinated rat nerve fibres. J. Physiol. (Lond.) 416, 93110. [ Links ]
20. Reid G., Scholz A., Bostock H. and Vogel W. (1999). Human axons contain at least five types of voltage-dependent potassium channel. J. Physiol. (Lond.) 518, 681696. [ Links ]
21. Hodgkin A.L. and Huxley A.F. (1952). A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. (Lond.) 117, 500544. [ Links ]
22. Frankenhaeuser B. and Huxley A.F. (1964). The action potential in the myelinated nerve fibre of Xenopus laevis as computed on the basis of voltage clamp data. J. Physiol. (Lond.) 171, 302315. [ Links ]
23. Chiu S.Y., Ritchie J.M., Rogart R.B. and Stagg D. (1979). A quantitative description of membrane currents in rabbit myelinated nerve. J. Physiol. (Lond.) 292, 149166. [ Links ]
24. Motz H. and Rattay F. (1986). A study of the application of the HodgkinHuxley and the FrankenhaeuserHuxley model for electrostimulation of the acoustic nerve. Neuroscience 18, 699712. [ Links ]
25. Rattay F. and Aberham M. (1993). Modeling axon membranes for functional electrical stimulation. IEEE Trans. Biomed. Eng. 40, 12011209. [ Links ]
26. Frijns J.H.M., Mooij J. and ten Kate J.H. (1994). A quantitative approach to modeling mammalian myelinated nerve fibers for electrical prosthesis design. IEEE Trans. Biomed. Eng. 41, 556566. [ Links ]
27. Huxley A.F. (1959). Ion movements during nerve activity. Ann. N. Y. Acad. Sci. 81, 221246. [ Links ]
28. Blight A.R. (1985). Computer simulation of action potentials and afterpotentials in mammalian myelinated axons: the case for a lower resistance myelin sheath. Neuroscience 15, 1331. [ Links ]
29. Smit J.E. (2008). Modelled response of the electrically stimulated human auditory nerve fibre. Ph.D. thesis, University of Pretoria, South Africa. [ Links ]
30. Scholz A., Reid G., Vogel W. and Bostock H. (1993). Ion channels in human axons. J. Neurophysiol. 70, 12741279. [ Links ]
31. Reid G., Bostock H. and Schwarz J.R. (1993). Quantitative description of action potentials and membrane currents in human node of Ranvier. J. Physiol. (Lond.) 467, 247P. [ Links ]
32. Schwarz J.R., Reid G. and Bostock H. (1995). Action potentials and membrane currents in the human node of Ranvier. Pflügers Arch. Eur. J. Physiol. 430, 283292. [ Links ]
33. Wesselink W.A., Holsheimer J. and Boom H.B.K. (1999). A model of the electrical behaviour of myelinated sensory nerve fibres based on human data. Med. Biol. Eng. Comput. 37, 228235. [ Links ]
34. Palti Y. and Adelman Jr. W.J. (1969). Measurement of axonal membrane conductances and capacity by means of a varying potential control voltage clamp. J. Membr. Biol. 1, 431458. [ Links ]
35. Wesselink W.A., Holsheimer J., Sonmez Z. and Boom H.B.K. (1997). Simulation model of the electrical characteristics of human myelinated sensory nerve fibers. In Proceedings of the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology, pp. 20292031. [ Links ]
36. Moore J.W., Joyner R.W., Brill M.H., Waxman S.D. and Najar-Joa M. (1978). Simulations of conduction in uniform myelinated fibers. Relative sensitivity to changes in nodal and internodal parameters. Biophys. J. 21, 147160. [ Links ]
37. Schalow G., Zach G.A. and Warzok R. (1995). Classification of human peripheral nerve fibre groups by conduction velocity and nerve fibre diameter is preserved following spinal cord lesion. J. Auton. Nerv. Syst. 52, 125150. [ Links ]
38. Rosbe K.W., Burgess B.J., Glynn R.J. and Nadol Jr J.B. (1996). Morphologic evidence for three cell types in the human spiral ganglion. Hear. Res. 93, 120127. [ Links ]
39. Schuknecht H.F. (1993). Pathology of the Ear, 2nd edn. Lea and Febiger, Philadelphia. [ Links ]
40. Glueckert R., Pfaller K., Kinnefors A., Rask-Andersen H. and Schrott-Fischer A. (2005). The human spiral ganglion: new insights into ultrastructure, survival rate and implications for cochlear implants. Audiol. Neurotol. 10, 258273. [ Links ]
41. Behse F. (1990). Morphometric studies on the human sural nerve. Acta Neurol. Scand. Suppl. 82, 138. [ Links ]
42. Nadol Jr J.B. (1990). Degeneration of cochlear neurons as seen in the spiral ganglion of man. Hear. Res. 49, 141154. [ Links ]
43. Frijns J.H.M., de Snoo S.L. and ten Kate J.H. (1996). Spatial selectivity in a rotationally symmetric model of the electrically stimulated cochlea. Hear. Res. 95, 3348. [ Links ]
44. Miller C.A. et al. (2004). Intracochlear and extracochlear ECAP's suggest antidromic action potentials. Hear. Res. 198, 7586. [ Links ]
45. Cohen L.T., Richardson L.M., Saunders E. and Cowan R.S.C. (2003). Spatial spread of neural excitation in cochlear implant recipients: comparison of improved ECAP method and psychophysical forward masking. Hear. Res. 179, 7287. [ Links ]
46. Abbas P.J., Hughes M.L., Brown C.J., Miller C.A. and South H. (2004). Channel interaction in cochlear implant users evaluated using the electrically evoked compound action potential. Audiol. Neurootol. 9, 203213. [ Links ]
47. Weiss G. (1901). Sur la possibilité de rendre comparables entre eux les appareils servant a l'excitation électrique. Arch. Ital. Biol. 35, 413446. [ Links ]
48. Bostock H. (1983). The strength-duration relationship for excitation of myelinated nerve: computed dependence on membrane parameters. J. Physiol. (Lond.) 341, 5974. [ Links ]
49. Lapicque L. (1907). Recherches quantitatifs sur l'excitation electrique des nerfs traitee comme un polarisation. J. Physiol. (Lond.) 9, 622635. [ Links ]
50. Miller C.A., Abbas P.J. and Robinson B.K. (2001). Response properties of the refractory auditory nerve fibre. J. Assoc. Res. Otolaryngol. 2, 216232. [ Links ]
51. Cartee L.A., van den Honert C., Finley C.C. and Miller R.L. (2000). Evaluation of a model of the cochlear neural membrane. I. Physiological measurement of membrane characteristics in response to intrameatal electrical stimulation. Hear. Res. 146, 143152. [ Links ]
52. Brown C.J., Abbas P.J. and Gantz B. (1990). Electrically evoked whole-nerve action potentials: data from human cochlear implant users. J. Acoust. Soc. Am. 88, 13851391. [ Links ]
53. van den Honert C. and Stypulkowski P.H. (1984). Physiological properties of the electrically stimulated auditory nerve. II. Single fiber recordings. Hear. Res. 14, 225243. [ Links ]
54. Miller C.A., Abbas P.J. and Rubinstein J.T. (1999). An empirically based model of the electrically evoked compound action potential. Hear. Res. 135, 118. [ Links ]
55. Miller C.A. et al. (1998). Electrically evoked compound action potentials of guinea pig and cat: responses to monopolar, monophasic stimulation. Hear. Res. 119, 142154. [ Links ]
56. Miller C.A., Abbas P.J., Robinson B.K., Rubinstein J.T. and Matsuoka A.J. (1999). Electrically evoked single-fiber action potentials from cat: responses to monopolar, monophasic stimulation. Hear. Res. 130, 197218. [ Links ]
57. Lai W.K. and Dillier N. (2000). A simple two-component model of the electrically evoked compound action potential in the human cochlea. Audiol. Neurootol. 5, 333345. [ Links ]
58. Burke D., Kiernan M.C. and Bostock H. (2001). Excitability of human axons. Clin. Neurophysiol. 112, 15751585. [ Links ]
59. Bostock H. and Rothwell J.C. (1997). Latent addition in motor and sensory fibres of human peripheral nerve. J. Physiol. (Lond.) 498, 277294. [ Links ]
60. Bostock H., Sears T.A. and Sherratt R.M. (1983). The spatial distribution of excitability and membrane current in normal and demyelinated mammalian nerve fibres. J. Physiol. (Lond.) 341, 4158. [ Links ]
61. Atkins P.W. (1995). Physical Chemistry, 5th edn. Oxford University Press, Oxford. [ Links ]
62. Hille B. (2001). Ionic Channels of Excitable Membrane, 3rd edn. Sinauer Associates, Sunderland, Massachusetts. [ Links ]
Received 3 March. Accepted 30 July 2008.
‡ Author for correspondence. E-mail: firstname.lastname@example.com
Full equations and parameter values for the human auditory nerve fibre model follow. The model was run at body temperature (37°C), although the temperature dependence of the parameters is also stated. The model was based on the cable model of Rattay.6 The dendrite and soma (except for the soma diameter) reproduce Rattay's model and only the axon was replaced by the new model, for which electrical parameter values are listed in Table A1 and morphometric parameter values in Table A2.
The change in the membrane potential (Vk) at the centre of the k-th compartment is described by the cable equation6
The membrane potential is given by Vk = Vi,k Ve,k Vres, having an initial value Vk(0) equal to 0. Vi,k is the intracellular potential, Ve,k the extracellular potential and Vres the resting membrane potential. The HH-model ionic membrane current (Iion,k) is described in terms of the Na+, K+ and leakage ionic conductances21.
Equilibrium potentials are given by
where R is the universal gas constant, F the Faraday constant, TK the temperature (in kelvin) and [ion]o/[ion]i the extracellular to intracellular ion concentration ratio for Na+, K+ and leakage ions, respectively.
Myelinated internodes are simple double-cable structures.28 The leaky myelin sheath and axolemma were considered combined together in series, having a high resistance and low capacitance. The total capacitance is given by
with cmem the same value as the nodal membrane capacitance and cmy the myelin membrane capacitance (Table A1). The internodal conductance is given by
where Nmy is the number of myelin layers, Rmy the temperature-dependent myelin membrane resistance and Rmem the temperature-dependent axolemmal membrane resistance (see Table A2 and Blight28). Iint is therefore given by
The dynamics of the opening probabilities (m,h and n, respectively) of the ion channels are described by
with initial values21 m(0) = 0.5, h(0) = 0.6, and n(0) = 0.32.
Ion channel gating variables are given by
where constants B,C and D are the original HH-model parameters21 (Table A3). The factors given by A indicate the acceleration of the activation and inactivation of membrane permeability to the specific ion species, as suggested by Huxley.27


text:
Video Review - Realms of Ancient War
Tom Mc Shea brings quick death to Lava Guardians in this video review for Realms of Ancient War.
Tom Mc Shea brings quick death to Lava Guardians in this video review for Realms of Ancient War.
The warrior goes on a rampage killing dogs in the forest while honing his skills with blades.
Kite and corral the thieves' camp into a nice little dock in order to dispense poisonous pain on them.
Kite some leprous creatures around and around a tree while waiting for your ability cooldowns to come back.
The Rogue uses her abilities to possess and skeleton and use it to her advantage.
Rogue fights through many monsters and an Ancient Lich
Rogue battles the Mad Sorcerer and sells items
Rogue takes on zombie like creatures and the Lava Guardian
Rogue takes on hordes of enemies and the Dominant Werewolf
This week we check out Resident Evil 6, NBA 2K13, Carrier Command: Gaea Mission War of the Roses and Realms of Ancient War
Get your hack'n'slash fill with this gameplay cooperative video for Realms of Ancient War.
Check out this reveal trailer for the Rogue class in R.A.W.
Check out a gameplay overview video showing all the features along with gameplay sequences.
The Wizard is the second of three playable heroes introduced so far in R.A.W.
Here's a R.A.W. gameplay video featuring one of the three playable heroes of the game: the warrior!
Here's a teaser trailer for the upcoming hack-and-slash title, R.A.W.
Use your keyboard!
Log in to comment

subset: commoncrawl


text:
A rare 1903 Ford Model A that's one of the oldest surviving cars made by the company was purchased at auction by Bill Ford Jr.
The great-grandson of Ford Motor Co. founder Henry Ford bid $264,000 for the 109-year-old Model A Rear Entry Tonneau in October and plans to show the car during a year-long celebration of the sesquicentennial of Henry Ford's birth July 30, 1863. Henry Ford died in 1947 at the age of 83.
In its first year in business, the fledgling Ford Motor sold two-cylinder, 100-cubic inch, 8-horsepower Model A motor cars from July 1903 to March 1904 with an original list price of $850. The open-air horseless carriage's top speed was an astounding (for the time) 30 mph.
"The timing was perfect to bring this key part of Ford heritage back to the family as we celebrate the 150th anniversary of my great-grandfather's birth and his vision to improve people's lives by making cars affordable for the average family," Bill Ford, executive chairman of Ford Motor Co., said in a statement.
At $264,000, the vintage Model A was a bargain of sorts. It was sold for a bid of $630,000 in 2007 by RM Auctions in Hershey, Pa.
The car, whose engine was rebuilt in 2007, has all of its original features and completed the London to Brighton Veteran Car Run in 2003 when it turned 100 years old.
"The Model A helped keep our company going during a difficult time and enabled my great-grandfather to continue pursuing his vision of putting the world on wheels," Bill Ford said. "We look forward to carrying that same spirit of innovation forward as we develop new technologies for safer, cleaner, more fuel-efficient vehicles."
Ford has software fix for recalled cars
Ford dealers are receiving a software upgrade to resolve a problem with severe overheating that prompted the recall of nearly 90,000 2013 Ford Escapes and Fusions.
The overheating issue affects only vehicles with 1.6-liter EcoBoost, 4-cylinder engines that were recalled Nov. 30. Ford said 12 fires in Escapes and one in a Fusion were related to the problem caused by a loss of coolant pressure necessary for proper circulation.
Ford recalled 73,320 Escape SE and SEL models and 15,833 Fusions with the turbocharged EcoBoost engine, all sold in North America.
Some drivers who experienced engine fires heard a warning chime and had a red light and others said the message "Engine Power Reduced to Lower Temps" or "Engine over temp, stop safely," appeared in the instrument cluster.
Ford Group Vice President for Global Production Development Raj Nair said the software upgrade would electronically control some of the valves to better manage engine temperatures.
"That will resolve the issue," Nair told The New York Times.
The upgrade will take about four hours and the Los Angeles Times says dealers will arrange for loaner vehicles for owners at no charge.
The redesigned Escape has had four recalls since it went on sale in June.
EPA to investigate Ford hybrid mileage claims
Does the new Ford C-MAX hybrid really get 47 miles per gallon?
Consumer Reports magazine says its tests didn't get that kind of mileage and the U.S. Environmental Protection Agency plans to review Ford's fuel efficiency advertising.
CR said during its testing a C-MAX only got 37 mpg overall, 35 mpg in city driving and 38 mpg on the highway. The Ford Fusion, which advertises the same 47 mpg overall, got 39 mpg in combined city/highway driving, 35 mpg city and 41 mpg highway.
"These two vehicles have the largest discrepancy between our overall-mpg results and the estimates published by the EPA that we've seen among any current models," Consumer Reports said in a statement.
The EPA said it would "look at the [CR] report and data."
Ford said fuel economy of hybrids varies with driving styles and conditions. The C-MAX can go 62 mph on batteries only before its 4-cylinder gasoline engine starts to recharge the battery.
If the car is driven over 62 mph it has to use gasoline to maintain electric power, reducing mileage, The Detroit News said.
"Early C-MAX hybrid and Fusion hybrid customers praise the vehicles and report a range of fuel economy figures, including some reports above 47 mpg," a Ford spokesman said. "This reinforces the fact that driving styles, driving conditions and other factors can cause mileage to vary."
Average fuel economy of new vehicles sold in the United States was 24.1 mpg in November, the same as the record set in October, the University of Michigan Eco-Driving Index found. That's a 20 percent [4 mpg] improvement in new vehicle fuel economy from October 2007 when the survey began.
Honda developing a smaller crossover SUV
Honda Motor Co. plans to show a small crossover SUV concept vehicle at next month's North American International Auto Show in Detroit.
One of Honda's top sellers is the CR-V crossover SUV based on the Honda Civic platform. The concept SUV -- which would be smaller and cheaper -- would be based on the same platform as the subcompact Honda Fit.
Honda calls it an "urban SUV concept."
Dream cars, dream customers
While drivers may lust after dream cars, automakers are looking for their dream customers.
A market analysis by credit reporting giant Experian Automotive in Schaumburg, Ill., found the average amount financed for a new-vehicle loan rose by $90 to $25,963 in the third quarter. The average credit score of a new-car customer was 755, down from 763 a year earlier.
Not surprisingly, buyers of luxury brands like Volvo, Lexus and Acura had the highest credit scores, of 818, 816 and 813, respectively, followed by imports Audi, Infiniti, Jaguar and Porsche, all 810.
The brand selling to buyers with the lowest credit scores was Mitsubishi, whose average shopper had a credit score of 694, followed by Suzuki at 704.
Suzuki, which is leaving the U.S. market in 2013, has sold about 23,000 vehicles in the United States this year. Chevrolet, Fiat, Dodge, Chrysler and Ram buyers also were among those with lower credit scores.
Chrysler Group customers had an average credit score of 718, the third lowest in the survey, followed by Kia, at 721.
Experian Automotive said sub-prime loans (riskier loans with higher interest rates) for new vehicles rose 3 percent in the third quarter and made up a quarter of all new car loans.
"Expanding loans to lower-risk tiers opens the market for more car shoppers while an increase in leasing means it is easier for consumers to get more vehicle for a lower monthly payment," Melinda Zabritski, director of automotive credit at Experian Automotive, said in a release.


text:
Co-Captain Oliver McNally and the Crimson are searching for the program's second straight Ivy League title (Drew Hallowell).
- Complete Game Notes (PDF)
- Live Statistics at Columbia
- Live Video at Columbia (with subscrption)
- Live Audio at Columbia (free)
- Live Statistics at Cornell
- Live Video at Cornell (ESPN3.com)
- Live Audio at Cornell (free)
The Particulars
Harvard (24-4, 10-2 Ivy) sits one-half game up in first place in the Ivy League and will visit Columbia (14-14, 3-9) Friday evening.
Harvard's 24-4 overall start is the best start in program history and has set a new program mark for wins in a season (surpassing 23 in 2010-11). The Crimson is also off to a 10-2 Ivy League start for the second consecutive season.
Game Coverage
Live Video will be available for a subscription at GoColumbiaLions.om. Guest TV/radio personality Guy Adami of CNBC's "Fast Money" will join WHRB's Charlie Hobbs and James Yoon for the audio call on WHRB-FM and GoCrimson.com (for free). Live statistics will also be available for the game at GoCrimson.com.
Saturday's game will be shown live on ESPN3.com. Charlie Hobbs and James Yoon will have the audio call on WHRB-FM and GoCrimson.com (for free). Live statistics will also be available for the game at GoCrimson.com.
Around the Ivy League
In other Ancient Eight contests this evening, Penn hosts Brown, Yale visits Princeton, and Dartmouth heads to Ithaca, N.Y., to face Cornell.
Series History Against Columbia
Friday's game marks the 168th meeting between Harvard and Columbia, with the Lions owning a 93-74 advantage in the series that started back in 1900-01. The Crimson has taken six of the last seven games against the Lions, including a season sweep in each of the last two years.
Harvard's Last Time Out
Kyle Casey scored 12 points and grabbed six rebounds, while Wesley Saunders tallied 10 points on 5-of-6 shooting, but the Crimson fell at home to Penn, 55-54, Feb. 25. The loss snapped Harvard's 28-game home win streak, which spanned more than two years (Feb. 19, 2010-Feb. 25, 2012). The Crimson only shot 2-of-11 from beyond the arc (.182) and turned the ball over 20 times.
Columbia's Last Time Out
Columbia is coming off a 94-78 loss at Brown Feb. 25. Brian Barbour led the way with 18 points, followed by Mark Cisco (15), Alex Rosenberg (13) and Meiko Lyles (10). Barbour connected on 8-of-9 free throws and also dished out 10 assists to earn a double-double. Brown outrebounded the Lions, 34-25, and the Bears sank 57.7 percent of their shots (30-of-52).
Best Ivy Start
Harvard began conference play with a 7-0 start for the first time in program history. The Crimson is 10-2 in the Ivy League for the second straight season.
Harvard currently sits at No. 38 in the RPI, according to collegerpi.com. The Crimson earned the highest ranking in program history, No. 14, Dec. 2, 2011.
Harvard Against The Ivy League
Over the last two seasons, the Crimson boasts a 22-5 (.814) against Ivy League opponents. During that stretch, the Crimson is 9-3 (.750) against Ancient Eight opponents on the road and 13-1 at home (.929). This season, Harvard is 10-2 in conference games, having swept Dartmouth, Brown and Yale, defeated Penn in a road contest and downed Cornell. Columbia and Princeton at home.
Back To 20
For the third straight year and the third time in program history, Harvard has won 20 games in a season, boasting a 24-4 overall mark this season. The Crimson went 21-8 in 2009-10 and posted a 23-7 overall mark last season. Harvard's 24 victories set a new program record.
Stepping Up On D
The Crimson is allowing only 54.0 points per game this season, good for third in the nation in scoring defense. Wisconsin paces the nation, surrendering only 51.7 points per contest, while Virginia sits second (52.2 points allowed per game)Harvard has only allowed 70 points twice and surrendered 50 or less points in 11 games and less than 40 points twice.
Free-Throw Defense
Entering the weekend, Harvard was 20th in the nation in free throw shooting defense, as opponents are only making 65.0 percent of attempts (266-of-409). Coppin State leads the nation (.619).
Rejection List
With 42 blocks this season, Keith Wright now ranks first in program history with 148 rejections, having surpassed Brian Cusworth '07. Wright broke the record with a rejection in the second half against Penn Feb. 25, 2012. Wright's 54 blocks last year also stand second in Harvard history for a single season. Brian Banks '78 had 59 rejections during the 1977-78 campaign.
Kyle Casey has rejected 89 blocks in his career, including 31 this season, ranking him fifth in program history in rejections.
Handing Out Dishes
Brandyn Curry has handed out 413 assists in his career, ranking the junior fifth in program history. Curry trails Glenn Fine '79 (559) for fourth place in the Harvard record book.
The Crimson will play at least nine games on national or regional television this season.
Harvard is 5-3 on TV this year after earning wins over Utah (HDNet), No. 20/22 Florida State (Versus) and Central Florida (Versus) at the Battle 4 Atlantis. The Crimson also defeated Boston University (NESN) and Boston College (ESPN3), but fell on the road at No. 9/9 Connecticut (ESPN2), at Princeton (ESPNU) and at home to Penn (ESPN3).
Coming Down With It
With his 10-rebound performance against Brown Feb. 17, Keith Wright now has 24 double digit rebound games in his career. Wright also has five double-doubles this season and has led Harvard in rebounding in 21 of 28 contests. Wright stands sixth in program history with 715 career rebounds. Harvard has outrebounded 15 of its last 18 opponents.
Hitting Baskets
Keith Wright stands first in the Ivy League in field-goal percentage, hitting 59.0 percent of his attempts this season (125-of-212).
Casting Ballots
Earlier this season, the Crimson became the first Ivy team ranked in the AP poll since Princeton was rated No. 8 in the final poll of the 1997-98 season. On Jan. 2, Harvard was No. 21 in the coaches poll and No. 22 in the AP poll, the highest rankings in program history. The Crimson matched the No. 21 ranking in the coaches poll Feb. 6.
Harvard is the only Ivy League team to have received at least one vote in a major national poll this season. The Crimson appeared in the ESPN/USA Today Coaches poll eight straight weeks: Dec. 19-Feb. 6.
Protecting The Ball
Entering the week, Brandyn Curry ranked first in the Ivy League and tied for 17th in the country in assist/turnover ratio (2.8).
Double-Double Show
Keith Wright leads the Crimson with five double-doubles (at Holy Cross Nov. 15, Florida Atlantic Dec. 22, at Monmouth Jan. 10, at Princeton Feb. 11 and Brown Feb. 17), while Kyle Casey (Saint Joseph's Dec. 31) and Jonah Travis (Seattle Dec. 4) have recorded one apiece this year. Wright has amassed 17 double-doubles over the course of his career in Cambridge.
Harvard/Amaker Against Columbia and Cornell
The Crimson boasts a 6-3 mark against Columbia under coach Amaker. After losing the first three games against the Lions under Amaker, Harvard has reeled off six consecutive victories since the 2008-09 season.
Lavietes Is The Place To Be
Harvard enjoyed a 28-game win streak at home, a program record, between Feb. 19, 2010 and Feb. 24, 2012. The streak was the second longest in the country during that stretch and Harvard finished 11-1 at home during this season after going 14-0 at Lavietes Pavilion last year.
Iron Horse
Oliver McNally has played in 115 games during his Harvard career, putting him tied for first with Jeremy Lin '10 for the most games played in Harvard history (115). Keith Wright has played in 106 games, placing him tied for seventh in program history.
Sold Out Lavietes
Harvard enjoyed 10 sellout crowds at Lavietes Pavilion this season (MIT, Saint Joseph's, Dartmouth, George Washington, Cornell, Columbia, Brown, Yale, Princeton and Penn). The Crimson sold out 10 of its 12 home games this season, a program record.
Defense Wins Games
The Crimson enters the week third in the country in scoring defense (54.0 points allowed per game).
Harvard had not allowed more than 49 points in four straight games (Nov. 24-Dec. 1) for the first time since the 1946-47 season, which was prior to the invention of the shot clock and the 3-point line.The Crimson also surrendered 38 or less points in two straight games (Jan. 21-27) for the first time since 1946-47. Harvard has only allowed more than 60 points in nine of 28 games this year and has held opponents to less than 60 points in nine of the last 12 contests.
Road Warriors
The Crimson, which currently owns a 13-3 record in road/neutral sites, will play a at least a total of 18 road/neutral games this winter. Harvard's 13 road/neutral sites wins this year is a new program record, surpassing 10 victories during the 2009-10 campaign. The Crimson is 10-3 on the road and 3-0 in neutral sites in 2011-12.
LinSanity: Harvard In The NBA
Former Harvard guard and three-time All-Ivy League honoree Jeremy Lin '10 has made quite an impact this season as a member of the New York Knicks. Lin, who was named to the NBA's Rising Stars Game (Feb. 24), is averaging 14.4 points per game and 5.8 assists per contest in 17 games with the New York Knicks this season. Lin tallied a career-high 38 points in a win over the Los Angeles Lakers Feb. 10, 2012.
With his NBA debut for the Golden State Warriors against the Los Angeles Clippers Oct. 29, 2010, Lin became the first Ivy League player to suit up for an NBA team since Penn's Matt Maloney played for the Atlanta Hawks and Yale's Chris Dudley was a member of the Portland Trail Blazers in 2003.
Lin joined former Harvard standouts Saul Mariaschin '47 (Boston Celtics) and Edward Smith '51 (New York Knicks) as Crimson players who have seen time in the NBA. During his first season in the NBA with Golden State, Lin played in 29 games, averaging 2.6 points per game and 1.4 assists per contest.
Head Coach Tommy Amaker
Tommy Amaker (Duke '87) is in his fifth season as head coach of the Harvard men's basketball team. He registered his 250th career coaching victory Dec. 4, 2011 against Seattle at Lavietes Pavilion. Amaker has guided Harvard to its first national ranking, as the Crimson was rated No. 25 in the AP poll and No. 24 in the ESPN/USA Today coaches ranking Dec. 5, 2011. Amaker also led the Crimson to its first Ivy League title as well as the program's first appearance in the NIT. In addition, the Crimson established a program record with 23 victories in 2010-11.
He brings a 266-194 (.578) career head coaching record into today's game, including a 90-55 (.621) mark at Harvard, a 108-84 (.563) record at Michigan and a 68-55 (.553) record at Seton Hall.
Monthly Consistency
In the months of November, December, January and February, Harvard won six games. The Crimson went 6-0 in Nove mber, 6-1 in December, 6-1 in January and 6-2 in February.


text: Charlotte Ronsonplayed to her crowd of twenty-somethings at Lincoln Center with a collection that's equal parts Angela Chase and Rayanne Graff. Floral dresses topped white baby tees and plaid flannel was wrapped around the waists of baby doll dresses. Teeny-tiny "I got bored in class" kind of braids drove the point home, especially when coupled with leather chokers, lip rings and Samantha Ronson's playlist — it included both "Stay" and "Laid".


text:
Rudimentary Peni's Archaic was originally released in June 2004 on ten inch vinyl and CD. Some tracks are written by Grant and some by Nick whilst others are co-written by both members. Archaic deals more with personal experience than the majority of the bands previous releases. The twelve songs on the album cover a variety of, shall we say, darker topics including mortality, despair, cremation, and the closing of the British national health service. The brevity of the lyrics (often a single line) is matched by the pummelling harshness of the guitar riffs, which hammer away as if pouring salt into an open wound.
We're now proud to present the remastered version of Archaic. The vinyl version is on 180g white wax and features gatefold sleeve, 6 full size double-sided art cards, bonus poster, and download card. Also available: CD version in gatefold wallet with 16 page art/lyrics booklet, and a limited edition shirt.
Truth told, we had a bit of trouble with this one. Firstly, in between cutting the vinyl and being ready to press it, our original pressing plant managed to damage one side of the metalwork. We decided to move to another pressing plant and had the damaged side recut there. We pressed the album, only to discover that it now had two B-sides. That original plant had also managed to mislabel the metalwork, so the side we thought was damaged (A) was actually side B. Now we had to recut B again at the new plant. This time we pressed it on white vinyl so there can be no confusion. Honestly, the final cuts are much better sounding than the ones we discarded, so we're not going to cry into our milk for too long about it. About 50 copies of the double-B side version on black vinyl made it into circulation via our mail order department before we caught the mistake. Those customers have already been sent replacements at no charge. All of the rest of the double-B side vinyls have been destroyed.
Next up in the Rudimentary Peni reissue series is Death Church, in January.
Personnel • Nick Blinko • Grant Matthews • Jon Grenville
Track Listing:
- One and All
- Suffer
- In Crematorium Flame
- Lost
- The Rain
- Mercy of Slumber
- The Curse
- The Enlightened Dreamer
- Farewell Tomorrow
- House of the Void
- Rehearsal for Morality
Total Running Time: 15:33
Buy Rudimentary Peni stuff from the Southern web shop.


text:
A businessman was about to go on a long business trip, and was worried that his wife would cheat on him while he was gone. So to prevent this, he visited the local sex shop in order to buy his wife a vibrator to keep her occupied in his absence.
After examining the products, he hadn't found an appropriately amazing vibrator and asked the store clerk for help. The store clerk recommended the "Voodoo D**k."
"How does it work?" asked the businessman.
The clerk unwrapped the Voodoo D**k from its ceremonial tiki box and said to it, "Voodoo D**k that door." The vibrator flew out of the box and attacked the door with such vigor that the door split in half.
"Fantastic," said the man. "I'll take it!"
He instructed his wife on how to use the Voodoo D**k and left on his business trip. Soon, his wife decided to try it out and said the magic words: "Voodoo D**k my p***y."
The Voodoo D**k flew out of the box and gave her orgasm after orgasm. But soon it became too much, and she couldn't figure out how to make it stop. So she got into her car and began driving to the hospital, swerving so much that she got pulled over by the police. The policeman asked her why she was driving so recklessly and she explained to him that she had a Voodoo D**k inside her that wouldn't leave her alone.
The policeman looked at her skeptically and said, "Voodoo D**k, my ass."


text:
Posted by Mike on July 10, 2001
In Reply to: Black Irish posted by Amy McGee on January 13, 19100
: : : : What does it mean to call someone a "Black Irishman".
: : According to rumors and legends,Black Irish are the descendants of a few surviving ill-fated Spanish sailors who sailed with the Felícima Armada from Spain to invade England but were ultimately shipwrecked on the northern and western coasts of Ireland in the autumn of 1588. A very small number of the more than seven hundred Spanish men who made it alive to the Irish coast survived, and a few of those who did allegedly became intimate with enough Irish women so as to engender a new inter-racial (Hibernian-Iberian) strain of progeny whose "dark hair and eyes and soft brown Southern skin testifies to its remote Spanish ancestry."
: :
: : Follow on the link below for a very, very detailed essay, with footnotes, on the Black Irish!
: Thank you! I have some "Black Irish" ancestry, and I never knew exactly what it meant. I was a little timid to claim it without knowing!


text:
How to Use the Images
Photos 1 and 2: Aftermath of the Johnstown Flood.
The flood snapped large trees like sticks and turned them into battering rams that could pierce wall. Shattered buildings were thrown into piles three stories high, completely filling some blocks.
Questions for Photos 1 and 2
1. Why do you think some buildings survived the flood while others were completely destroyed?
2. How might the people in the photos have been feeling at the time these images were taken?
* The photos on this screen have a resolution of 72 dots per inch (dpi), and therefore will print poorly. You can obtain a high quality version of Photo 1 and Photo 2, but be aware that each file will take as much as 40 seconds to load with a 28.8K modem.


text:
It was 6 a.m. on October 3, 2009 when Staff. Sgt. Clinton Romesha and 52 of his fellow soldiers awoke to find their small outpost not far from Afghanistan's border with Pakistan, under attack.
They were outnumbered – eight times over – by more than 400 heavily armed Taliban fighters who had occupied the high ground on all four sides of the small base, nestled on the floor of a tiny valley of the Hindu Kush.
"Four hundred Taliban versus 53 American soldiers. It just doesn't seem fair – to the Taliban," Mr. Romesha joked at a Pentagon ceremony Tuesday, before sounding a somber note. The outpost "was our home," he said, "and they simply couldn't have it."
But they were going to try. The Taliban were raining down fire upon the American troops at Combat Outpost Keating, using rocket-propelled grenades (RPGs), mortars, anti-aircraft machine guns, and small arms to fire into what senior military officials described as a "fish bowl."
It was a battle that was to last one full day – a day that ultimately became the deadliest of that year for US troops, leaving eight American soldiers dead and 80 percent of the buildings on the base destroyed.
On Monday, in a ceremony at the White House, Romesha, who was wounded in the battle, was awarded the Medal of Honor by President Obama. Mr. Obama cited the now retired staff sergeant's "conspicuous gallantry" and adherence to the code of never leaving behind a fallen comrade as he rallied the American force and called in airstrikes to repel the Taliban attackers.
On Tuesday, it was the Pentagon's opportunity to pay tribute to one of its own as it inducted Romesha into the Hall of Heroes, only the fourth living recipient to be awarded the military's highest honor for the wars in Iraq and Afghanistan.
Romesha "embodies the essence of a soldier, and represents what every man and woman who dons this uniform strives to be," Army Chief of Staff Gen. Raymond Odierno, the service's top officer, said during the ceremony.
General Odierno pointed to Romesha's fellow soldiers from his Bravo troop of the 4th Brigade Combat Team of the 4th Infantry Division, which became one of most decorated units in US military history, earning nine Silver Stars, 18 Bronze Star medals with Valor, and 27 Purple Hearts.
On that October morning in 2009, Romesha, who had already served two tours of duty in Iraq, distinguished himself, repeatedly moving through an open and uncovered avenue on the base, which was being hit with a barrage of gunfire and RPG fire, as he made sure his fellow soldiers were in place and well-equipped.
Romesha at one point took cover near a generator to fire at a Taliban machine gun team that that was on high ground. "After destroying this team," he turned his sights on another machine gun team "that was firing an overwhelming amount of fire" onto the base, according to the Defense Department's official narrative of the battle.
As he was doing that, however, an RPG hit the generator and knocked Romesha backward, onto his assistant gunner.
"Not noticing his own wounds, Romesha re-engaged the enemy with his weapon system until an additional soldier arrived to man the machine gun."
At this point, Romesha moved back along the base's deadly open avenue to assemble another team and to make sure they were well equipped with ammunition.
It was only when he arrived back at the barracks to put together the team did another soldier notice his wounds and provide first aid.
His shrapnel wounds treated, Romesha assembled a five-man team and told them to load up on ammunition. In the meantime, he went to check on a fellow soldier holding Taliban at bay.
As he did, Romesha grabbed "the only accessible sniper rifle along the way, a Dragunov belonging to the Afghan National Army."
"With complete disregard for his own safety," according to the official citation, Romesha "engaged multiple enemy positions," including a machine gun nest and sniper. He also killed three Taliban fighters who had breached the perimeter of the outpost.
Along the way, the team also secured the ammunition depot and an entry control point that the Taliban was trying to break through.
He and his fellow soldiers then pushed forward 100 meters to prevent Taliban fighters from taking the bodies of US soldiers who had been killed during the battle.
"The Medal of Honor is not often given when things went well on a battlefield," Romesha pointed out during the Pentagon induction ceremony.
Romesha is part of a "new greatest generation of Americans" that have stepped forward after 9/11, Defense Secretary Leon Panetta told the assembled audience Tuesday. "This generation has endured enormous hardships and they have done it with tremendous courage."
As he prepares to depart his post as Defense secretary, Mr. Panetta took time during the ceremony to reflect on the condolence letters he has signed, and "the lives that were cut short in the prime of their life – the promises, the dreams, the aspirations that each of those fallen heroes carried with them."
He said he hoped their sacrifice would encourage politicians to "carefully weigh when we send American men and women into battle."
Then he turned to Romesha. "Your courage," Panetta told him, "is now a part of American history."


text:
Denver Police Chief Robert White made plain Tuesday that it will not be business as usual in his department — announcing the replacement of two top cops, the elimination of an entire layer of senior administration and plans to reassign some or all of the commanders in the city's six districts.
White, who was sworn in last December, also plans to increase the number of commanders from the current seven to 11.
Gone will be the rank of division chief, currently held by four senior officers.
He will boost the number of officers available to patrol the streets by as many as 70 men and women, but that will happen over time and depend on the department's budget. White said he would move those new patrol officers into the divisions by reassigning some members of specialized units, such as the gang bureau, and hiring civilians to handle some jobs now held by cops.
The changes will increase accountability, make the department more responsive to residents and improve its ability to fight crime, White told the City Council's Committee on Public Safety in an afternoon meeting.
"This reorganization will absolutely, unequivocally put us in a position to be more efficient, more effective, more responsive to the citizens in our community," White said.
Over time, it also will save money, he added.
The pace of the rollout will depend on the money available for the department's budget. The realignment will begin at the end of March, with White's appointment of new district commanders.
He hopes to have up to 30 new officers on the streets not long after the commanders are in place.
The present district commanders can reapply for their jobs, but it is likely that some, if not all, will be replaced.
"We have a lot of talent on the police department from the rank of lieutenant and above," he said.
He asked that each City Council member submit the name of one member of their community to sit on a selection board that will pick 12 candidates from the applicants for district commander.
"I sincerely believe, wherever it is possible, the decisions we make we should have some involvement with the community," White said.
Because council members represent that community, White added, "I thought it would be appropriate to ask them to provide someone who would be interested in doing that and that could represent their constituents."
White, who will provide the board with a job description for the positions, will then select six of the candidates to fill those slots.
"I am pleased to see the level of community involvement," committee chairman Paul Lopez said.
White also named two deputy chiefs Tuesday — David Quinones, who had been division chief of patrol, and William Nagle, who had been acting division chief of research. Quinones and Nagle also will sit on the board, White said.
The previous deputy chiefs and four division chiefs will return to their civil-service ranks — such as captain — and will have the opportunity to apply to be commanders.
"It is an effort to flatten the organization. … Flattening the organization gives us an opportunity to hold people more accountable for what they're doing," White said.
Commanders will have more power than in the past to control the way they use officers and other resources in their divisions, and they will report to the new deputy chiefs.
Nick Rogers, president of the Denver Police Protective Association, said he welcomes some change.
"I trust that these changes will be beneficial to the citizens and detrimental to the criminals," Rogers said.
Current District 6 Cmdr. Tony Lopez said he would reapply for his job.
"We are going to get the best and the brightest to compete for these coveted roles, and that is a benefit for our city. In 29 years, I have never seen such an exciting time. This is a fresh perspective," Lopez said.
Tom McGhee: 303-954-1671 or email@example.com


text:
> Home > FAQs > How to complain
If for any reason you are unhappy with us, we would like to hear from you. Making a complaint will not prejudice your right to take legal proceedings.
If you have a complaint about any aspect of this policy, our service or a claim please write to:
The Customer Relations ManagerThistle Insurance Services LimitedSouthgate HouseSouthgate StreetGloucesterGL1 1UB.
If the complaint is still not resolved to your satisfaction, you can approach The Financial Ombudsman Service (FOS) at the address below:
The Financial Ombudsman ServiceExchange TowerLondonE14 9SRTel: 0800 023 4567
The above complaints procedure is in addition to your statutory rights as a consumer. For further information about your statutory rights contact your local authority Trading Standards Service or Citizens Advice Bureau.
We use cookies to manage your application, report traffic statistics, track referrals of visitors, and target advertising. By using this site you are consenting to this. You may change these settings at any time. Please note - Our cookie policy changed on 5/1/2015.
Your current cookie settings:
Strictly necessary cookies Performance cookies Functionality cookies Targeting/advertising cookies
Photoguard is a trading style of Thistle Insurance Services Limited. Thistle Insurance Services Limited is authorised and regulated by the Financial Conduct Authority. FRN 310419. Lloyd's Broker. Registered in England No. 00338645. Registered office: Rossington's Business Park, West Carr Road, Retford, Nottinghamshire, DN22 7SW.