Organization of orientation and direction selectivity in areas 17 and 18 of cat cerebral cortex

1987 ◽  
Vol 58 (4) ◽  
pp. 676-699 ◽  
Author(s):  
N. E. Berman ◽  
M. E. Wilkes ◽  
B. R. Payne
Keyword(s):  
Receptive Fields ◽  
Direction Selectivity ◽  
Preferred Orientation ◽  
Wide Field ◽  
Area 17 ◽  
Stimulus Motion ◽  
Area 18 ◽  
Preferred Direction ◽  
Area Centralis ◽  
Areas 17 And 18

1. The organization of subunits and sequences subserving preferred stimulus orientation and preferred direction of stimulus motion in cat cerebral cortical areas 17 and 18 was determined by making vertical, tangential, and oblique microelectrode penetrations into those areas. 2. Quantitative measurements of direction selectivity indicated that not all shades of direction selectivity are equally represented in area 17. Peaks in the distribution of direction indices may correspond to the bidirectional, direction biased, and direction selective categories used in qualitative studies. 3. The relationship between preferred direction and location in the visual field was examined for units with receptive fields centered more than 15 degrees from the area centralis. Simple cells had orientation preferences that tended to be parallel to radii extending out from the area centralis. Wide-field complex cells had orientation preferences that tended to be parallel to concentric circles centered on the area centralis; the direction preferences of this group were biased toward motion away from the area centralis. 4. Unit pairs separated by 200 microns or less were 4.2 times as likely to have the same preferred direction as to have opposite preferred directions, indicating that, on average, strings of five neurons have similar direction preferences. 5. Tracks in area 18 showed a similar pattern to those in area 17. 6. In the vertical tracks in area 17 a small proportion (12%) of the units recorded in infragranular layers had preferred orientations that deviated 30 degrees or more from the first unit recorded in the same column. The presence of these cells most likely reflects the relative crowding of columns in infragranular layers, which occurs at the crown of the lateral gyrus. Columns with such large jumps in preferred orientation were not observed in area 18, which occupies a relatively flat region of cortex. 7. In both areas 17 and 18 direction preference in vertical tracks usually reversed at least once, either between supra- and infragranular layers or within infragranular layers. Along these same tracks, orientation preference usually did not change. 8. In tangential tracks, preferred direction and orientation preferences changed together in small increments. Occasionally a large jump in preferred direction would occur with only a small change in preferred orientation. These large jumps were considered to mark the boundaries of the direction sequences. Most frequently these boundaries were separated by 400-600 microns. This value is approximately half the size of a complete set of orientation preferences (700-1,200 microns).(ABSTRACT TRUNCATED AT 400 WORDS)

Receptive-field properties and neuronal connectivity in striate and parastriate cortex of contour-deprived cats

1976 ◽  
Vol 39 (3) ◽  
pp. 613-630 ◽  
Author(s):  
W. Singer ◽  
F. Tretter
Keyword(s):  
Electrical Stimulation ◽  
Receptive Field ◽  
Visual Experience ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Connectivity Pattern ◽  
Area 18 ◽  
Efferent Connections ◽  
Receptive Field Properties ◽  
Areas 17 And 18

An attempt was made to relate the alterations of cortical receptive fields as they result from binocular visual deprivation to changes in afferent, intrinsic, and efferent connections of the striate and parastriate cortex. The experiments were performed in cats aged at least 1 jr with their eyelids sutured closed from birth.The results of the receptive-field analysis in A17 confirmed the reduction of light-responsive cells, the occasional incongruity of receptive-field properties in the two eyes, and to some extent also the loss of orientation and direction selectivity as reported previously. Other properties common to numerous deprived receptive fields were the lack of sharp inhibitory sidebands and the sometimes exceedingly large size of the receptive fields. Qualitatively as well as quantitatively, similar alterations were observed in area 18. A rather high percentage of cells in both areas had, however, preserved at least some orientation preference, and a few receptive fields had tuning properties comparable to those in normal cats. The ability of area 18 cells in normal cats to respond to much higher stimulus velocities than area 17 cells was not influenced by deprivation.The results obtained with electrical stimulation suggest two main deprivation effects: 1) A marked decrease in the safety factor of retinothalamic and thalamocortical transmission. 2) A clear decrease in efficiency of intracortical inhibition. But the electrical stimulation data also show that none of the basic principles of afferent, intrinsic, and efferent connectivity is lost or changed by deprivation. The conduction velocities in the subcortical afferents and the differentiation of the afferents to areas 17 and 18 into slow- and fast-conducting projection systems remain unaltered. Intrinsic excitatory connections remain functional; this is also true for the disynaptic inhibitory pathways activated preferentially by the fast-conducting thalamocortical projection. The laminar distribution of cells with monosynaptic versus polsynaptic excitatory connections is similar to that in normal cats. Neurons with corticofugal axons remain functionally connected and show the same connectivity pattern as those in normal cats. The nonspecific activation system from the mesencephalic reticular formation also remains functioning both at the thalamic and the cortical level.We conclude from these and several other observations that most, if not all, afferent, intrinsic, and efferent connections of areas 17 and 18 are specified from birth and depend only little on visual experience. This predetermined structural plan, however, allows for some freedom in the domain of orientation tuning, binocular correspondence, and retinotopy which is specified only when visual experience is possible.

Response properties of area 17 neurons in cats reared in stroboscopic illumination

1987 ◽  
Vol 57 (5) ◽  
pp. 1511-1535 ◽  
Author(s):  
J. Cremieux ◽  
G. A. Orban ◽  
J. Duysens ◽  
B. Amblard
Keyword(s):  
Peripheral Vision ◽  
Receptive Fields ◽  
Response Strength ◽  
Direction Selectivity ◽  
Orientation Tuning ◽  
Area 17 ◽  
Central Vision ◽  
Response Properties ◽  
Adult Cat ◽  
Areas 17 And 18

The response properties of 196 area 17 cells were studied qualitatively in seven cats reared from birth in a stroboscopically illuminated environment (frequency, 2/s; duration, 200 microseconds). Quantitative testing with the multihistogram technique was carried out in 115 cells. As control population, 453 neurons recorded in area 17 of the normal adult cat and tested qualitatively (of which 301 neurons were tested quantitatively) were available. In area 17 of strobe-reared cats, a number of spatial characteristics of receptive fields investigated with hand-held stimuli were found to be abnormal. There was a strong reduction in the encounter frequency both of end-stopped cells and of binocularly driven cells in the strobe-reared cats. Central receptive fields in strobe-reared cats were wider than in normal cats, but the increase in receptive-field width with eccentricity was still observed. More cells than in normal cats showed either no selectivity or only a weak bias for stimulus orientation, but the orientation tuning of orientation-selective cells was similar in strobe-reared and normal cats. Quantitative testing revealed that the velocity preference of cells in area 17 subserving central vision was different in strobe-reared cats from that of normal cats, due to a reduction in the encounter frequency of cells showing a preference for low velocities. There was no difference in velocity preference between strobe-reared and normal cats in the parts of area 17 that subserve peripheral vision, the proportion of neurons responding to fast velocities showing a similar increase in both groups of animals. Fewer cells were direction selective in strobe-reared cats than in normal cats. Most of the remaining direction-selective cells had peripheral receptive fields and the synergism between leaving an OFF subregion and entering an ON subregion contributed to their direction selectivity. Latency of neurons in area 17 of strobe-reared cats was slightly higher than in normal cats, but the response strength of neurons was the same in the two groups. The proportion of cells failing to respond to briefly flashed stationary stimuli was significantly lower in strobe-reared than in normal animals. Qualitative and quantitative testing showed that strobe rearing has a stronger effect on the parts of area 17 that subserve central vision than on those that subserve peripheral vision. Comparing the present results with those of Kennedy and Orban (37) shows that strobe rearing has less effect on area 17 than on area 18 and that the functional differences between areas 17 and 18 in strobe-reared cats are smaller than in normal cats.

Visual responsiveness and direction selectivity of cells in area 18 during local reversible inactivation of area 17 in cats

1992 ◽  
Vol 9 (6) ◽  
pp. 581-593 ◽  
Author(s):  
C. Casanova ◽  
Y. Michaud ◽  
C. Morin ◽  
P.A. McKinley ◽  
S. Molotchnikoff
Keyword(s):  
Receptive Field ◽  
Specific Effect ◽  
Direction Selectivity ◽  
Area 17 ◽  
Visual Responses ◽  
Drug Injection ◽  
Area 18 ◽  
Preferred Direction ◽  
Receptive Field Properties ◽  
Number Of Cells

AbstractWe have investigated the effects of inactivation of localized sites in area 17 on the visual responses of cells in visuotopically corresponding regions of area 18. Experiments were performed on adult normal cats. The striate cortex was inactivated by the injection of nanoliters of lidocaine hydrochloride or of γ-aminobutyric acid (GABA) dissolved in a staining solution. Responses of the simple and complex cells of area 18 to optimally oriented light and dark bars moving in the two directions of motion were recorded before, during, and after the drug injection. Two main effects are described.First, for a substantial number of cells, the drug injection provoked an overall reduction of the cell's visual responses. This nonspecific effect largely predominated in the complex cell family (76% of the units affected). This effect is consistent with the presence of long-range excitatory connections in the visual cortex.Second, the inactivation of area 17 could affect specific receptive-field properties of cells in area 18. The main specific effect was a loss of direction selectivity of a number of cells in area 18, mainly in the simple family (more than 53% of the units affected). The change in direction selectivity comes either from a disinhibitory effect in the nonpreferred direction or from a reduction of response in the preferred direction. It is proposed that the disinhibitory effects were mediated by inhibitory interneurones within area 18. In a very few cases, the change of directional preference was associated with a modification of the cell's response profile.These results showed that the signals from area 17 are necessary to drive a number of units in area 18, and that area 17 can contribute to, or at least modulate, the receptive-field properties of a large number of cells in the parastriate area.

Velocity selectivity in the cat visual system. III. Contribution of temporal factors

1985 ◽  
Vol 54 (4) ◽  
pp. 1068-1083 ◽  
Author(s):  
J. Duysens ◽  
G. A. Orban ◽  
J. Cremieux ◽  
H. Maes
Keyword(s):  
Receptive Field ◽  
Receptive Fields ◽  
Area 17 ◽  
High Contrast ◽  
Low Contrast ◽  
Area 18 ◽  
Duration Threshold ◽  
Area Centralis ◽  
Velocity Selectivity ◽  
Stimulation Of

In 149 units from area 17 and 48 units from area 18 the responses to stationary stimulation of different durations were compared with the responses to the same stimulus (a 0.3 degrees-wide light or dark bar) moving at different velocities. The aim was to test the hypothesis that the range of effective velocities depends on the time needed for the bar to cross the receptive field. Forty-two percent of the area 17 cells and 8% of the area 18 cells responded poorly or not at all to briefly presented stationary stimulation. These cells were unable to respond at high velocities, and for these "duration-sensitive" cells the velocity characteristics are well predicted on the basis of responses to stationary stimulation of different durations. Cells that responded equally well to periods of stationary stimulation ranging from 12.5 to 3,200 ms ("duration-insensitive cells") were found to be able to respond at all equivalent velocities, but their preference for either high, low, or intermediate velocities was not reflected in differences in responsiveness to the different durations tested. Duration-sensitive cells in area 17 tended to have a receptive field near the area centralis, and 73% of them were classified as S-family cells, one third being end-stopped S-cells. In contrast only 18% of the duration-insensitive cells were of the S family, and these S-family cells were rarely end-stopped (1/12) or rarely had receptive fields within 5 degrees of the fovea (3/12). Duration-sensitive cells had very long latencies (median 285 ms) in response to a stationary flashed light bar of 1 s duration but much shorter latencies (median 91 ms) when tested with a slowly moving light bar. This difference was not seen in duration-insensitive cells (median latencies = 61 and 59 ms). The ability to respond at high velocity was contrast dependent. At a low contrast level all cells failed to respond to brief stimulation, whether moving or stationary. At high contrast levels only the duration-insensitive cells showed an increased responsivity to brief stimuli. The absence of responses in duration-sensitive cells to brief stimuli of high contrast may depend upon suppressive influences reaching these cells before the excitatory influences. We conclude that the velocity upper cutoff of most S-family cells with a central receptive field can be predicted from a knowledge of the minimum duration of stationary presentation required for their activation (median ON duration threshold, 200 ms).(ABSTRACT TRUNCATED AT 400 WORDS)

Visual response properties of cortical inputs to an extrastriate cortical area in the cat

1989 ◽  
Vol 3 (3) ◽  
pp. 249-265 ◽  
Author(s):  
Helen Sherk
Keyword(s):  
Ocular Dominance ◽  
Receptive Fields ◽  
Great Majority ◽  
Direction Selectivity ◽  
Field Size ◽  
Visual Response ◽  
Area 17 ◽  
Response Properties ◽  
Novel Approach ◽  
Areas 17 And 18

AbstractThe existence of multiple areas of extrastriate visual cortex raises the question of how the response properties of each area are derived from its visual input. This question was investigated for one such area in the cat, referred to here as the Clare-Bishop area (Hubel & Wiesel, 1969); it is the region of lateral suprasylvian cortex that receives input from area 17. A novel approach was used, in which kainic acid was injected locally into the Clare-Bishop area, making it possible to record directly from afferent inputs.The response properties of the great majority of a sample of 424 presumed afferents resembled cells in areas 17 and 18. Thus, a systematic comparison was made with cells from area 17's upper layers, the source of its projection to the Clare-Bishop area (Gilbert & Kelly, 1975), to see whether these afferents had distinctive properties that might distinguish them from cells projecting to areas 18 or 19. Some differences did emerge: (1) The smallest receptive fields typical of area 17 were relatively scarce among afferents. (2) Direction-selective afferents were more abundant than were such cells in area 17. (3) End-stopped afferents were extremely rare, although end-stopped cells were common in area 17's upper layers.Despite these differences, afferents were far more similar in their properties to cells in areas 17 and 18 than to cells in the Clare-Bishop area. Compared to the latter, afferents showed major discrepancies in receptive-field size, in direction selectivity, in end-stopping, and in ocular dominance distribution. These differences seem most likely to stem from circuitry intrinsic to the Clare-Bishop area.

Response properties of visual cortical neurons in cats reared in stroboscopic illumination

1983 ◽  
Vol 49 (3) ◽  
pp. 686-704 ◽  
Author(s):  
H. Kennedy ◽  
G. A. Orban
Keyword(s):  
Visual Field ◽  
Receptive Fields ◽  
Normal Animal ◽  
Area 17 ◽  
Central Vision ◽  
Area 18 ◽  
Areas 17 And 18 ◽  
Contralateral Eye ◽  
Visual Cortical ◽  
High Pass

1. The response properties of 182 units were studied in the primary visual cortices (155 in area 18 and 27 in area 17) in eight cats reared from birth in a stroboscopically illuminated environment (frequency, 2/s; duration, 200 microseconds). Multihistogram quantitative testing was carried out in 82 units (64 in area 18 and 18 in area 17). Two hundred three neurons recorded and quantitatively tested in areas 17 and 18 of the normal adult cat were used for comparison. 2. Spatial characteristics of receptive fields investigated using hand-held stimuli were found to be abnormal. The correlation between receptive-field width and eccentricity was lost in area 18 and consequently, receptive fields were significantly wider in area 18 subserving central vision. Cells could be classified according to the spatial characteristics of their receptive fields. There was a much smaller proportion of end-stopped cells in strobe-reared animals. Orientation tuning in the deprived animals was normal except for a small number of cells that showed no selectivity for stimulus orientation. 3. Compilation of velocity-response curves made it possible to classify areas 17 and 18 neurons into four categories: velocity low-pass, velocity broad-band, velocity tuned, and velocity high-pass cells. The proportion of velocity high-pass cells was reduced in area 18 subserving peripheral vision, as was the proportion of velocity-tuned cells in area 18 subserving central vision. 4. In the strobe-reared animal velocity sensitivity was somewhat different from that of the normal animal. Neurons in area 18 subserving the peripheral visual field failed to respond to fast velocities. Neurons in area 17 subserving the central visual field in strobe-reared animals responded to slightly higher velocities than in the normal animal. 5. In the deprived animals the number of neurons that were selective to the direction of motion was strongly reduced. The majority of neurons failed to show a selectivity for direction at all velocities. A number of neurons could be directional at some velocities but were unreliable, since they inverted their preferred direction with velocity changes. 6. Binocular convergence onto visual cortical cells was perturbed. In area 18 the majority of neurons were driven by the contralateral eye. In area 17 most neurons could be driven only by either the ipsilateral or contralateral eye. 7. Quantitative testing (of direction selectivity, sensitivity to high velocities, response latency, and strength) and qualitative testing (receptive-field width, end stopping, and ocular dominance) showed that the normal influence of eccentricity on functional properties was strongly reduced by strobe rearing.

Directional selectivity and spatiotemporal structure of receptive fields of simple cells in cat striate cortex

1991 ◽  
Vol 66 (2) ◽  
pp. 505-529 ◽  
Author(s):  
R. C. Reid ◽  
R. E. Soodak ◽  
R. M. Shapley
Keyword(s):  
Time Course ◽  
Linear Prediction ◽  
Striate Cortex ◽  
Receptive Fields ◽  
Quantitative Measure ◽  
Direction Selectivity ◽  
Simple Cells ◽  
Preferred Direction ◽  
Orientation Contrast ◽  
Cat Striate Cortex

1. Simple cells in cat striate cortex were studied with a number of stimulation paradigms to explore the extent to which linear mechanisms determine direction selectivity. For each paradigm, our aim was to predict the selectivity for the direction of moving stimuli given only the responses to stationary stimuli. We have found that the prediction robustly determines the direction and magnitude of the preferred response but overestimates the nonpreferred response. 2. The main paradigm consisted of comparing the responses of simple cells to contrast reversal sinusoidal gratings with their responses to drifting gratings (of the same orientation, contrast, and spatial and temporal frequencies) in both directions of motion. Although it is known that simple cells display spatiotemporally inseparable responses to contrast reversal gratings, this spatiotemporal inseparability is demonstrated here to predict a certain amount of direction selectivity under the assumption that simple cells sum their inputs linearly. 3. The linear prediction of the directional index (DI), a quantitative measure of the degree of direction selectivity, was compared with the measured DI obtained from the responses to drifting gratings. The median value of the ratio of the two was 0.30, indicating that there is a significant nonlinear component to direction selectivity. 4. The absolute magnitudes of the responses to gratings moving in both directions of motion were compared with the linear predictions as well. Whereas the preferred direction response showed only a slight amount of facilitation compared with the linear prediction, there was a significant amount of nonlinear suppression in the nonpreferred direction. 5. Spatiotemporal inseparability was demonstrated also with stationary temporally modulated bars. The time course of response to these bars was different for different positions in the receptive field. The degree of spatiotemporal inseparability measured with sinusoidally modulated bars agreed quantitatively with that measured in experiments with stationary gratings. 6. A linear prediction of the responses to drifting luminance borders was compared with the actual responses. As with the grating experiments, the prediction was qualitatively accurate, giving the correct preferred direction but underestimating the magnitude of direction selectivity observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Processing of form and motion in area 21a of cat visual cortex

1993 ◽  
Vol 10 (1) ◽  
pp. 93-115 ◽  
Author(s):  
B. Dreher ◽  
A. Michalski ◽  
R. H. T. Ho ◽  
C. W. F. Lee ◽  
W. Burke
Keyword(s):  
Spatial Organization ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Orientation Tuning ◽  
Area 17 ◽  
Horizontal Strip ◽  
Tuning Curves ◽  
Mean Width ◽  
Area 21A ◽  
The Mean

AbstractExtracellular recordings from single neurons have been made from presumed area 21a of the cerebral cortex of the cat, anesthetized with N2O/O2/sodium pentobarbitone mixture. Area 21a contains mainly a representation of a central horizontal strip of contralateral visual field about 5 deg above and below the horizontal meridian.Excitatory discharge fields of area 21a neurons were substantially (or slightly but significantly) larger than those of neurons at corresponding eccentricities in areas 17, 19, or 18, respectively. About 95% of area 21a neurons could be activated through either eye and the input from the ipsilateral eye was commonly dominant. Over 90% and less than 10% of neurons had, respectively, C-type and S-type receptive-field organization. Virtually all neurons were orientation-selective and the mean width at half-height of the orientation tuning curves at 52.9 deg was not significantly different from that of neurons in areas 17 and 18. About 30% of area 21a neurons had preferred orientations within 15 deg of the vertical.The mean direction-selectivity index (32.8%) of area 21a neurons was substantially lower than the indices for neurons in areas 17 or 18. Only a few neurons exhibited moderately strong end-zone inhibition. Area 21a neurons responded poorly to fast-moving stimuli and the mean preferred velocity at about 12.5 deg/s was not significantly different from that for area 17 neurons.Selective pressure block of Y fibers in contralateral optic nerve resulted in a small but significant reduction in the preferred velocities of neurons activated via the Y-blocked eye. By contrast, removal of the Y input did not produce significant changes in the spatial organization of receptive fields (S or C type), the size of the discharge fields, the width of orientation tuning curves, or direction-selectivity indices.Our results are consistent with the idea that area 21a receives its principal excitatory input from area 17 and is involved mainly in form rather than motion analysis.

scholarly journals Modelling Drosophila motion vision pathways for decoding the direction of translating objects against cluttered moving backgrounds

2020 ◽  
Vol 114 (4-5) ◽  
pp. 443-460
Author(s):  
Qinbing Fu ◽  
Shigang Yue
Keyword(s):  
Motion Perception ◽  
Computational Modelling ◽  
Fruit Fly ◽  
Neural System ◽  
Direction Selectivity ◽  
System Model ◽  
Wide Field ◽  
Motion Vision ◽  
Preferred Direction ◽  
On And Off Pathways

Abstract Decoding the direction of translating objects in front of cluttered moving backgrounds, accurately and efficiently, is still a challenging problem. In nature, lightweight and low-powered flying insects apply motion vision to detect a moving target in highly variable environments during flight, which are excellent paradigms to learn motion perception strategies. This paper investigates the fruit fly Drosophila motion vision pathways and presents computational modelling based on cutting-edge physiological researches. The proposed visual system model features bio-plausible ON and OFF pathways, wide-field horizontal-sensitive (HS) and vertical-sensitive (VS) systems. The main contributions of this research are on two aspects: (1) the proposed model articulates the forming of both direction-selective and direction-opponent responses, revealed as principal features of motion perception neural circuits, in a feed-forward manner; (2) it also shows robust direction selectivity to translating objects in front of cluttered moving backgrounds, via the modelling of spatiotemporal dynamics including combination of motion pre-filtering mechanisms and ensembles of local correlators inside both the ON and OFF pathways, which works effectively to suppress irrelevant background motion or distractors, and to improve the dynamic response. Accordingly, the direction of translating objects is decoded as global responses of both the HS and VS systems with positive or negative output indicating preferred-direction or null-direction translation. The experiments have verified the effectiveness of the proposed neural system model, and demonstrated its responsive preference to faster-moving, higher-contrast and larger-size targets embedded in cluttered moving backgrounds.

Response selectivity of neurons in area MT of the macaque monkey during reversible inactivation of area V1

1992 ◽  
Vol 67 (6) ◽  
pp. 1437-1446 ◽  
Author(s):  
P. Girard ◽  
P. A. Salin ◽  
J. Bullier
Keyword(s):  
Receptive Field ◽  
Macaque Monkey ◽  
Direction Selectivity ◽  
Area 17 ◽  
Visual Responses ◽  
Area Mt ◽  
Reversible Inactivation ◽  
Mt Neurons ◽  
Preferred Direction ◽  
Blocking Index

1. Behavioral results in the monkey and clinical studies in human show remarkable residual visual capacities after a lesion of area V1. Earlier work by Rodman et al. demonstrated that visual activity can be recorded in the middle temporal area (MT) of the macaque monkey several weeks after a complete lesion of V1. These authors also tested the effect of a reversible block of area V1 on the visual responses of a small number of neurons in area MT and showed that most of these cells remain visually responsive. From the results of that study, however, it is difficult to assess the contribution of area 17 to the receptive-field selectivity of area MT neurons. To address this question, we have quantitatively measured the effects of a reversible inactivation of area 17 on the direction selectivity of MT neurons. 2. A circular part of the opercular region of area V1 was reversibly inactivated by cooling with a Peltier device. A microelectrode was positioned in the lower layers of V1 to control the total inactivation of that area. Eighty percent of the sites recorded in the retinotopically corresponding region of MT during inactivation of V1 were found to be visually responsive. The importance of the effect was assessed by calculating the blocking index (0 for no effect, 1 for complete inactivation). Approximately one-half of the quantitatively studied neurons gave a blocking index below 0.6, illustrating the strong residual responses recorded in many neurons. 3. Receptive-field properties were examined with multihistograms. It was found that, during inactivation of V1, the preferred direction changed for most neurons but remained close to the preferred direction or to its opposite in the control situation. During inactivation of V1, the average tuning curve of neurons became broader mostly because of strong reductions in the response to directions close to the preferred and nonpreferred. Very little change was observed in the responses for directions at 90 degrees to the optimal. These results are consistent with a model in which direction selectivity is present without an input from V1 but is reinforced by the spatial organization of this excitatory input. 4. Residual responses were found to be highly dependent on the state of anesthesia because they were completely abolished by the addition of 0.4-0.5% halothane to the ventilation gases. Finally, visual responses were recorded in area MT several hours after an acute lesion of area 17.(ABSTRACT TRUNCATED AT 400 WORDS)

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