Direction Selectivity Of Simple Cells Research Articles

Inhibition facilitates fast, robust motion detection in the visual cortex

Event Abstract Back to Event Inhibition facilitates fast, robust motion detection in the visual cortex A classical question of computational and systems neuroscience addresses the mechanism underlying direction selectivity of simple cells of primary visual cortex. In a prominent class of models, a cortical cell integrates excitatory inputs of different response latencies and offset receptive field positions arranged such that inputs arrive synchronously for stimuli moving in the preferred direction, but dispersed in time for stimuli in the null direction. Selectivity is assumed to be sharpened by a spike threshold. Here we probe this mechanism quantitatively: in particular, in the presence of an additional noisy input (due to, for example, random background activity), which is known to affect the threshold nonlinearity of the input-output relationship. Furthermore, we explore a possible role for inhibition, which has been found to be tuned for the same direction as excitation, but with different relative timing (Priebe and Ferster, 2005). We implement this model based on an exponential integrate-and-fire neuron (Fourcaud-Trocme et al., 2003). We model the noisy input by i) an additional noise current and/or ii) different degrees of spontaneous activity of input neurons. Our basic results are captured also by a simple rate model. We find that if only excitatory inputs are present, small levels of noisy input reduce direction selectivity strongly. For large noise, the mean firing rate for both stimulus directions is approximately equal, resulting in a very weakly selective neuron. In this regime, the firing rate is approximately proportional to input strength. Since the total number of inputs is the same for both directions (only their temporal order differs) the mean firing rate is approximately equal for both directions. In contrast, when inhibitory inputs are included and arranged in a push-pull fashion, as observed by Priebe and Ferster (2005), selectivity is fully recovered even for large levels of noise. For the null direction, both excitatory and inhibitory inputs arrive dispersed in time and therefore largely cancel each other resulting in a firing rate close to baseline. For the preferred direction, excitatory and inhibitory inputs each arrive synchronously, but with a temporal lag relative to each other. Since firing rate is bounded by zero, the increase in firing rate due to the excitatory inputs can greatly exceed the decrease caused by the inhibitory inputs, resulting in a strongly direction selective neuron. A similar result holds when probing the neuron with a drifting grating and defining selectivity based on the first Fourier component of firing rates during a stimulus period. Interestingly, in the presence of inhibition, the neuron responds selectively even after one stimulus cycle (~100ms) for various levels of noise. We conclude that inhibition in a push-pull organization is an essential part of the mechanism underlying cortical direction selectivity, providing robust selective responses in the presence of noisy or unrelated background activity, even after brief stimulus presentations. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). Inhibition facilitates fast, robust motion detection in the visual cortex. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.149 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Feb 2009; Published Online: 02 Feb 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Standing Waves and Traveling Waves Distinguish Two Circuits in Visual Cortex

The visual cortex represents stimuli through the activity of neuronal populations. We measured the evolution of this activity in space and time by imaging voltage-sensitive dyes in cat area V1. Contrast-reversing stimuli elicit responses that oscillate at twice the stimulus frequency, indicating that signals originate mostly in complex cells. These responses stand clear of the noise, whose amplitude decreases as 1/frequency, and yield high-resolution maps of orientation preference and retinotopy. We first show how these maps are combined to yield the responses to focal, oriented stimuli. We then study the evolution of the oscillating activity in space and time. In the orientation domain, it is a standing wave. In the spatial domain, it is a traveling wave propagating at 0.2-0.5 m/s. These different dynamics indicate a fundamental distinction in the circuits underlying selectivity for position and orientation, two key stimulus attributes.

Direction selectivity of simple cells in the primary visual cortex: Comparison of two alternative mathematical models. II: Velocity tuning and response to moving bars

The two models of direction selectivity, presented in a previous paper, are used to investigate the response of simple cells to moving bars with different length, luminance and orientation. Most results agree with experimental data reported in the literature. However, a striking difference between the models is observable after a reduction in bar length. The antiphase model predicts that the optimal direction of movement for a short bar is equal to the optimal direction for a long bar, whereas the in-phase model predicts that the two optimal directions are orthogonal. This difference may allow experimental discrimination between the two models.

Direction selectivity of simple cells in the primary visual cortex: Comparison of two alternative mathematical models. I: Response to drifting gratings

Two models of a single hypercolumn in the primary visual cortex are presented, and used for the analysis of direction selectivity in simple cells. The two models differ as to the arrangement of inhibitory connections: in the first (“antiphase model”) inhibition is in phase opposition with excitation, but with a similar orientation tuning; in the second (“in-phase model”), inhibition is in phase with excitation, but with broader orientation tuning. Simulation results, performed by using drifting gratings with different orientations, and different spatial and temporal frequencies, show that both models are able to explain the origin of direction preference of simple cells.

Direction Selectivity of Excitation and Inhibition in Simple Cells of the Cat Primary Visual Cortex

Direction selectivity in simple cells of primary visual cortex, defined from their spike responses, cannot be predicted using linear models. It has been suggested that the shunting inhibition evoked by visual stimulation is responsible for the nonlinear component of direction selectivity. Cortical inhibition would suppress a neuron's firing when stimuli move in the nonpreferred direction, but would allow responses to stimuli in the preferred direction. Models of direction selectivity based solely on input from the lateral geniculate nucleus, however, propose that the nonlinear response is caused by spike threshold. By extracting excitatory and inhibitory components of synaptic inputs from intracellular records obtained in vivo, we demonstrate that excitation and inhibition are tuned for the same direction, but differ in relative timing. Further, membrane potential responses combine in a linear fashion. Spike threshold, however, quantitatively accounts for the nonlinear component of direction selectivity, amplifying the direction selectivity of spike output relative to that of synaptic inputs.

Learning direction selectivity through spike-timing dependent modification of neurotransmitter release probability

It has recently been proposed that the direction selectivity of simple cells emerges from an interplay of depressing and non-depressing synapses projecting in an asymmetric arrangement onto these cells. We show that such an asymmetric arrangement may develop from a temporally asymmetric spike-based learning rule. The rule redistributes the probability of vesicle discharge, producing synapses with high discharge probability and strong depression in one-half of the receptive field and low discharge probability and weak depression in the other. This spatial shift together with the temporal phase advance of the depressing synapses adds up with the response of the surrounding non-depressing synapses only when the stimulus moves in the preferred direction.

Inhibitory contributions to spatiotemporal receptive-field structure and direction selectivity in simple cells of cat area 17.

Intracortical inhibition contributes to direction selectivity in primary visual cortex, but how it acts has been unclear. We investigated this problem in simple cells of cat area 17 by taking advantage of the link between spatiotemporal (S-T) receptive-field structure and direction selectivity. Most cells in layer 4 have S-T-oriented receptive fields in which gradients of response timing across the field confer a preferred direction of motion. Linear summation of responses across the receptive field, followed by a static nonlinear amplification, has been shown previously to account for directional tuning in layer 4. We tested the hypotheses that inhibition acts by altering S-T structure or the static nonlinearity or both. Drifting and counterphasing sine wave gratings were used to measure direction selectivity and S-T structure, respectively, in 17 layer 4 simple cells before and during iontophoresis of bicuculline methiodide (BMI), a GABAA antagonist. S-T orientation was quantified from fits to response temporal phase versus stimulus spatial phase data. Bicuculline reduced direction selectivity and S-T orientation in nearly all cells, and reductions in the two measures were well correlated (r = 0.81) and reversible. Using conventional linear predictions based on response phase and amplitude, we found that BMI-induced changes in S-T structure also accounted well for absolute changes in the amplitude and phase of responses to gratings drifting in the preferred and nonpreferred direction. For each cell we also calculated an exponent used to estimate the static nonlinearity. Bicuculline reduced the exponent in most cells, but the changes were not correlated with reductions in direction selectivity. We conclude that GABAA-mediated inhibition influences directional tuning in layer 4 primarily by sculpting S-T receptive-field structure. The source of the inhibition is likely to be other simple cells with certain spatiotemporal relationships to their target. Despite reductions in the two measures, most receptive fields maintained some directional tuning and S-T orientation during BMI. This suggests that their excitatory inputs, arising from the lateral geniculate nucleus and within area 17, are sufficient to create some S-T orientation and that inhibition accentuates it. Finally, BMI also reduced direction selectivity in 8 of 10 simple cells tested in layer 6, but the reductions were not accompanied by systematic changes in S-T structure. This reflects the fact that S-T orientation, as revealed by our first-order measures of the receptive field, is weak there normally. Inhibition likely affects layer 6 cells via more complex, nonlinear interactions.

Strobe rearing reduces direction selectivity in area 17 by altering spatiotemporal receptive-field structure.

Strobe rearing reduces direction selectivity in area 17 by altering spatiotemporal receptive-field structure. J. Neurophysiol. 80: 2991-3004, 1998. Direction selectivity in simple cells of cat area 17 is linked to spatiotemporal (S-T) receptive-field structure. S-T inseparable receptive fields display gradients of response timing across the receptive field that confer a preferred direction of motion. Receptive fields that are not direction selective lack gradients; they are S-T separable, displaying uniform timing across the field. Here we further examine this link using a developmental paradigm that disrupts direction selectivity. Cats were reared from birth to 8 mo of age in 8-Hz stroboscopic illumination. Direction selectivity in simple cells was then measured using gratings drifting at different temporal frequencies (0.25-16 Hz). S-T structure was assessed using stationary bars presented at different receptive-field positions, with bar luminance being modulated sinusoidally at different temporal frequencies. For each cell, plots of response phase versus bar position were fit by lines to characterize S-T inseparability at each temporal frequency. Strobe rearing produced a profound loss of direction selectivity at all temporal frequencies; only 10% of cells were selective compared with 80% in normal cats. The few remaining directional cells were selective over a narrower than normal range of temporal frequencies and exhibited weaker than normal direction selectivity. Importantly, the directional loss was accompanied by a virtual elimination of S-T inseparability. Nearly all cells were S-T separable, like nondirectional cells in normal cats. The loss was clearest in layer 4. Normally, inseparability is greatest there, and it correlates well (r = 0.77) with direction selectivity; strobe rearing reduced inseparability and direction selectivity to very low values. The few remaining directional cells were inseparable. In layer 6 of normal cats, most direction-selective cells are only weakly inseparable, and there is no consistent relationship between the two measures. However, after strobe rearing, even the weak inseparability was eliminated along with direction selectivity. The correlated changes in S-T structure and direction selectivity were confirmed using conventional linear predictions of directional tuning based on responses to counterphasing bars and white noise stimuli. The developmental changes were permanent, being observed up to 12 yr after strobe rearing. The deficits were remarkably specific; strobe rearing did not affect spatial receptive-field structure, orientation selectivity, spatial or temporal frequency tuning, or general responsiveness to visual stimuli. These results provide further support for a critical role of S-T structure in determining direction selectivity in simple cells. Strobe rearing eliminates directional tuning by altering the timing of responses within the receptive field.

Strobe rearing prevents the convergence of inputs with different response timings onto area 17 simple cells.

Strobe rearing prevents the convergence of inputs with different response timings onto area 17 simple cells. J. Neurophysiol. 80: 3005-3020, 1998. The preceding paper showed that the loss of direction selectivity in simple cells induced by strobe rearing reflects the elimination of spatially ordered response timing differences across the receptive field that underlie spatiotemporal (S-T) inseparability. Here we addressed whether these changes reflected an elimination of certain timings or an alteration in how timings were associated in single cells. Timing in receptive fields was measured using stationary bars undergoing sinusoidal luminance modulation at different temporal frequencies (0.5-6 Hz). For each bar position, response phase versus temporal frequency data were fit by a line to obtain two measures: absolute phase and latency. In normal cats, many individual simple cells display a wide range of timings; in layer 4, the mean range for absolute phase and latency was 0.21 cycles and 39 ms, respectively. Strobe rearing compressed the mean timing ranges in single cells, to 0.08 cycles and 31 ms, respectively, and this compression accounted for the loss of inseparability. A similar compression was measured in layer 6 cells. In contrast, the range of timing values across the simple-cell population was relatively normal. Single cells merely sampled narrower than normal regions of the timing space. We sought to understand these cortical changes in terms of how inputs from the lateral geniculate nucleus (LGN) may have been affected by strobe rearing. In normal cats, a wide range of absolute phase and latency values exists among lagged and nonlagged LGN cells, and these thalamic timings account for most of the cortical timings. Also, S-T inseparability in many simple cells can be attributed to the convergence of lagged and/or nonlagged inputs. Strobe rearing did not change the sampling of lagged and nonlagged cells, and the geniculate timings continued to account for most of the cortical timings. However, strobe rearing virtually eliminated cortical receptive fields with mixed lagged and nonlagged timing, and it compressed the timing range in cells dominated by one or the other geniculate type. Thus strobe rearing did not eliminate certain timings in LGN or cortex, but prevented the convergence of different timings on single cells. To account for these results, we propose a developmental model in which strobe stimulation alters the correlational structure of inputs based on their response timing. Only inputs with similar timing become associated on single cortical cells, and this produces S-T separable receptive fields that lack the ability to confer a preferred direction of motion.

Development of spatiotemporal receptive fields of simple cells: I. Model formulation.

A model for the development of spatiotemporal receptive fields of simple cells in the visual cortex is proposed. The model is based on the 1990 hypothesis of Saul and Humphrey that the convergence of four types of input onto a cortical cell, viz. non-lagged ON and OFF inputs and lagged ON and OFF inputs, underlies the spatial and temporal structure of the receptive fields. It therefore explains both orientation and direction selectivity of simple cells. The response properties of the four types of input are described by the product of linear spatial and temporal response functions. Extending the 1994 model of one of the authors (K.D. Miller), we describe the development of spatiotemporal receptive fields as a Hebbian learning process taking into account not only spatial but also temporal correlations between the different inputs. We derive the correlation functions that drive the development both for the period before and after eye-opening and demonstrate how the joint development of orientation and direction selectivity can be understood in the framework of correlation-based learning. Our investigation is split into two parts that are presented in two papers. In the first, the model for the response properties and for the development of direction-selective receptive fields is presented. In the second paper we present simulation results that are compared with experimental data, and also provide a first analysis of our model.

Direction selectivity of synaptic potentials in simple cells of the cat visual cortex.

Direction selectivity of synaptic potentials in simple cells of the cat visual cortex. J. Neurophysiol. 78: 2772-2789, 1997. The direction selectivity of simple cells in the visual cortex is generated at least in part by nonlinear mechanisms. If a neuron were spatially linear, its responses to moving stimuli could be predicted accurately from linear combinations of its responses to stationary stimuli presented at different positions within the receptive field. In extracellular recordings, this has not been found to be the case. Although the extracellular experiments demonstrate the presence of a nonlinearity, the cellular process underlying the nonlinearity, whether an early synaptic mechanism such as a shunting inhibition or simply the spike threshold at the output, is not known. To differentiate between these possibilities, we have recorded intracellularly from simple cells of the intact cat with the whole cell patch technique. A linear model of direction selectivity was used to analyze the synaptic potentials evoked by stationary sine-wave gratings. The model predicted the responses of cells to moving gratings with considerable accuracy. The degree of direction selectivity and the time course of the responses to moving gratings were both well matched by the model. The direction selectivity of the synaptic potentials was considerably smaller than that of the intracellularly recorded action potential, indicating that a nonlinear mechanism such as threshold enhances the direction selectivity of the cell's output over that of its synaptic inputs. At the input stage, however, the cells apparently sum their synaptic inputs in a highly linear fashion. A more constrained test of linearity of synaptic summation based on principal component analysis was applied to the responses of direction-selective cells to stationary gratings. The analysis confirms that the summation in these cells is highly linear. The principal component analysis is consistent with a model in which direction selectivity in cortical simple cells is generated by only two subunits, each with a different receptive-field position and response time course. The response time course for each of the two subunits is derived for four analyzed cells. Each derived subunit is linear in spatial summation, suggesting that the neurons that comprise each subunit are either geniculate X-cells or receive their primary synaptic input from X-cells. The amplitude of the response of each subunit is linearly related to the contrast of the stimulus. The subunits are nonlinear in the time domain, however: the response to a stationary stimulus whose contrast is modulated sinusoidally in time is nonsinusoidal. The principal component analysis does not exclude models of direction selectivity based on more than two subunits, but such higher-order models would have to include the constraint that the extra subunits form a smooth continuum of interpolation between the properties derived from the two subunit solution.

Modeling direction selectivity of simple cells in striate visual cortex within the framework of the canonical microcircuit

Nearly all models of direction selectivity (DS) in visual cortex are based on feedforward connection schemes, where geniculate input provides all excitatory synaptic input to both pyramidal and inhibitory neurons. Feedforward inhibition then suppresses feedforward excitation for nonoptimal stimuli. Anatomically, however, the majority of asymmetric, excitatory, synaptic contacts onto cortical cells is provided by other cortical neurons, as embodied in the Canonical Microcircuit of Douglas and Martin (1991). In this view, weak geniculate input is strongly amplified in the preferred direction by the action of intracortical excitatory connections, while in the null direction inhibition reduces geniculate-induced excitation. We investigate analytically and through biologically realistic computer simulations the functioning of a cortical network based on massive excitatory, cortico-cortical feedback. The behavior of this network is compared to physiological data as well as to the behavior of a purely feedforward model of DS based on nonlagged input. Our model explains a number of puzzling features of direction selective simple cells, including the small somatic input conductance changes that have been measured experimentally during stimulation in the null direction, and the persistence of DS while fully blocking inhibition in a single cell. Although the operation at the heart of our network is amplification, the network passes the linearity test of (Jagadeesh et al., 1993). We make specific predictions concerning the effect of selective blockade of cortical inhibition on the velocity-response curve.

Contribution of linear mechanisms to the specification of local motion by simple cells in areas 17 and 18 of the cat.

A reverse correlation technique, which permits estimation of three-dimensional first-order properties of receptive fields (RFs), was applied to simple cells in areas 17 and 18 of cat. Two classes of simple cells were found. For one class, the spatial and temporal RF characteristics were separable, i.e. they could be synthesized as the product of spatial and temporal weighting functions. RFs in the other class were inseparable, i.e. bright and dark subregions comprising each field were obliquely oriented in space-time. Based on a linear superposition model, these observations led to testable hypotheses: (1) simple cells with separable space-time characteristics should be speed but not direction selective and (2) simple cells with inseparable space-time characteristics should be direction selective and the optimal velocity of moving stimuli should be predictable from the slope of the oriented subregions. These hypotheses were tested by comparing responses to moving bars with those predicted by application of the convolution integral. Linear predictions accounted for waveforms of responses to moving bars in detail. For cells with oriented space-time characteristics, the preferred direction was always predicted correctly and the optimal speed was predicted quite well. Most cells with separable space-time characteristics were not direction selective as predicted. The major discrepancies between measured and predicted behavior were twofold. First, 8/32 cells with separable space-time RFs were direction selective. Second, predicted directional indices were weakly correlated with actual measurements. These conclusions hold for simple cells in both areas 17 and 18. The major difference between simple RFs in these areas is the coarser spatial scale seen in area 18. These results demonstrate a significant linear contribution to the speed and direction selectivity of simple cells in areas 17 and 18. Where additional, nonlinear mechanisms are inferred, they appear to act synergistically with the linear mechanism.

Linearity of summation of synaptic potentials underlying direction selectivity in simple cells of the cat visual cortex.

Intracellular recordings from simple cells of the cat visual cortex were used to test linear models for the generation of selectivity for the direction of visual motion. Direction selectivity has been thought to arise in part from nonlinear processes, as suggested by previous experiments that were based on extracellular recordings of action potentials. In intracellular recordings, however, the fluctuations in membrane potential evoked by moving stimuli were accurately predicted by the linear summation of responses to stationary stimuli. Nonlinear mechanisms were not required.

Spatiotemporal organization of simple-cell receptive fields in the cat's striate cortex. II. Linearity of temporal and spatial summation.

1. We have tested the hypothesis that simple cells in the cat's visual cortex perform a linear spatiotemporal filtering of the visual image. To conduct this study we note that a visual neuron behaves linearly if the responses to small, brief flashes of light are mathematically related, via the Fourier transform, to the responses elicited by sinusoidal grating stimuli. 2. We have evaluated the linearity of temporal and spatial summation for 118 simple cells recorded from the striate cortex (area 17) of adult cats and kittens at ages 4 and 8 wk postnatal. These neurons represent a subset of the population of cells for which we have described the postnatal development of spatiotemporal receptive-field structure in the preceding paper. Spatiotemporal receptive-field profiles are constructed, with the use of a reverse correlation technique, from the responses to random sequences of small bar stimuli that are brighter or darker than the background. Fourier analysis of spatiotemporal receptive-field profiles yields linear predictions of the cells' spatial and temporal frequency tuning. These predicted responses are compared with spatial and temporal frequency tuning curves measured by the use of drifting, sinusoidal-luminance grating stimuli. 3. For most simple cells, there is good agreement between spatial and temporal frequency tuning curves predicted from the receptive-field profile and those measured by the use of sinusoidal gratings. These results suggest that both spatial and temporal summation within simple cells are approximately linear. There is a tendency for predicted tuning curves to be slightly broader than measured tuning curves, a finding that is consistent with the effects of a threshold nonlinearity at the output of these neurons. In some cases, however, predicted tuning curves deviate from measured responses only at low spatial and temporal frequencies. This cannot be explained by a simple threshold nonlinearity. 4. If linearity is assumed, it should be possible to predict the direction selectivity of simple cells from the structure of their spatiotemporal receptive-field profiles. For virtually all cells, linear predictions correctly determine the preferred direction of motion of a visual stimulus. However, the strength of the directional bias is typically underestimated by a factor of about two on the basis of linear predictions. Consideration of the expansive exponential nonlinearity revealed in the contrast-response function permits a reconciliation of the discrepancy between measured and predicted direction selectivity indexes. 5. Overall, these findings show that spatiotemporal receptive-field profiles obtained with the use of reverse correlation may be used to predict a variety of response properties for simple cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Local cortical lesions abolish lateral inhibition at direction selective cells in cat visual cortex.

Many cells in the cat visual cortex display a strong selectivity for the direction of motion of an optimally oriented stimulus. Postsynaptic inhibition has been suggested to generate this direction selectivity in simple cells, but the intracortical pathways involved have not been identified. While continuously recording from simple cells in layers 4 and 6, we have inactivated the superficial cortical layers in small regions 0.4-2.5 mm from the cortical column under study by using heat lesions, localized cooling or gamma-aminobutyric acid (GABA) microiontophoresis. When inactivation affected cortical regions retinotopically representing motion in the non-preferred direction towards the receptive field, the responses to movement in this direction increased, and the recorded cells lost direction selectivity due to loss of inhibition. Our results indicate that direction selectivity of simple cells involves asymmetric inhibition of predictable cortical topography.

Influence of stimulus length on directional bias of complex cells in cat striate cortex

Visual cortical cells respond optimally to an oriented bar moving either in one unique direction or in directions 180 apart. Length-dependence of this direction selectivity was investigated in the striate cortex of lightly anaesthetized cats. Approaching half of all complex cells showed some lability in their direction selectivity. The incidence was highest in standard and intermediate (length-summating) complex cells, less amongst special complex cells (those with only localized summation) and least amongst end-stopped cells, especially those of the special category. By contrast, direction selectivity of simple cells was length-independent. No correlation between a cell's overt selectivity (i.e. bidirectional, directionbiased or direction-selective) and its lability with bar length or polarity of contrast (light/dark) was evident. Moreover, since individual neurons amongst a population of complex cells could exhibit either increase, decrease, or no change of direction selectivity with length, it is unlikely that length per se can be coded by direction-selectivity.

Direction selectivity of simple cells in cat striate cortex to moving light bars. II. Relation to moving dark bar responses.

The response properties of 84 simple striate cells in anaesthetized (N2O/O2 supplemented with sodium pentobarbital) and paralyzed cats were examined quantitatively using narrow optimally-oriented light and dark bars moving at optimal velocities. Different cells gave two to five spatially-offset response peaks, the light bar and the dark bar response peaks alternating with one another. With only 5 exceptions, the cells had the same preferred direction for movement of the dark bar as for the light bar. Static-field plots were prepared from 32 of the 84 cells using stationary flashing bars. The receptive fields of different cells had from two to four subregions responding either at light on (ON subregion) or at light off (OFF subregion) although one cell had only a single subregion. In the preferred direction of stimulus movement cells gave either the same number of response peaks to moving bars as there were subregions or one additional response peak. The additional response peak, termed a boundary response, always occurred at the end of the sequence of response peaks and was always completely direction selective. The direction selectivities of the individual response peaks in the responses from 49 of the 84 cells were analyzed. To ensure that each response peak and the corresponding peak in the opposite direction both came from the same subregion, the 49 cells were selected on the basis of having a response in the nonpreferred direction sufficient for analysis and of having a stimulus velocity less than 2.5 degrees/s so as to avoid significant spatial shifts of the peaks due to response latencies. For all but two of the 49 cells, the response peaks in any given profile always showed a progressively greater degree of direction selectivity as the stimulus advanced from one subregion to the next, the first subregion giving the least directionally-selective response peak and the last subregion the most directionally-selective peak. This observation was independent of the direction of stimulus motion and of the particular sequence in which the ON and the OFF subregions were traversed by the stimulus. The response patterns observed experimentally have been correlated with theoretical response patterns based on the responses of lateral geniculate neurons.

Direction selectivity of simple cells in cat striate cortex to moving light bars. I. Relation to stationary flashing bar and moving edge responses.

Quantitative estimates of the direction selectivities of 118 simple cells in response to moving light bars were expressed as a percentage calculated from the ratio of the response peaks: (preferred minus nonpreferred)/preferred. Virtually all simple cells were direction selective to some degree (mean direction selectivity 73.6%). Static-field plots to a stationary flashing bar were prepared from 74 of the 118 cells. Particular attention was given to the 42 cells with only two subregions in their static-field plot, one subregion responding at light on and the other at light off. It was concluded that interactive effects between subregions, whether synergistic or antagonistic, have little if any influence on the direction selective mechanism when the stimulus is a narrow light bar. Eighty two of the 118 cells were also tested with moving light and dark edges and of these 53 had response profiles with only two response peaks, one to the light edge and the other to the dark edge. Forty one of the 53 cells were each not only direction selective for both a light edge and a dark edge but also had a preferred direction for both edges that was the same as that for a light bar. Only two cells had preferred directions for both light and dark edges that were opposite to the direction preferred by the light bar. With one possible exception, every cell with two response static-field plot showed a one-to-one correspondence between the ordinal sequence of the response peaks and the ordinal sequence of the subregions. Depending upon the polarity of the moving edge and the ordinal sequence of the subregions, the mean level of the direction selectivity to a moving edge was significantly below that to a narrow moving light bar. This reduction in the degree of the direction selectivity appears to be due to an interaction between the subregions leading to a reduction in the amplitude of the response in the preferred direction rather than a suppression of the direction selective mechanism that operates in the nonpreferred direction. Moving edges cause a weak interactive effect between the subregions that seems always to reduce the degree of the direction selectivity, never increasing it.

Laminar distribution of first-order neurons and afferent terminals in cat striate cortex.

ArticlesLaminar distribution of first-order neurons and afferent terminals in cat striate cortexJ. Bullier, and G. H. HenryJ. Bullier, and G. H. HenryPublished Online:01 Sep 1979https://doi.org/10.1152/jn.1979.42.5.1271MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByBiophysical Support for Functionally Distinct Cell Types in the Frontal Eye FieldJeremiah Y. Cohen, Pierre Pouget, Richard P. Heitz, Geoffrey F. Woodman, and Jeffrey D. Schall1 February 2009 | Journal of Neurophysiology, Vol. 101, No. 2Laminar Organization of Response Properties in Primary Visual Cortex of the Gray Squirrel (Sciurus carolinensis)J. Alexander Heimel, Stephen D. Van Hooser, and Sacha B. 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Lund1 July 1999 | Journal of Neurophysiology, Vol. 82, No. 1Inhibitory Contributions to Spatiotemporal Receptive-Field Structure and Direction Selectivity in Simple Cells of Cat Area 17Aditya Murthy, and Allen L. Humphrey1 March 1999 | Journal of Neurophysiology, Vol. 81, No. 3Strobe Rearing Prevents the Convergence of Inputs With Different Response Timings Onto Area 17 Simple CellsAllen L. Humphrey, Alan B. Saul, and Jordan C. Feidler1 December 1998 | Journal of Neurophysiology, Vol. 80, No. 6Encoding of Binocular Disparity by Complex Cells in the Cat's Visual CortexIzumi Ohzawa, Gregory C. Deangelis, and Ralph D. 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