Inhibitory components in the neuronal response of the lateral suprasylvian cortical area in the cat

Inhibitory components in the response evoked by presentation of mobile visual stimuli in neurons belonging to the lateral suprasylvian area of the cerebral cortex were investigated in cats. It was demonstrated by comparing poststimulus histograms of neuronal response to movement in two opposite directions that the location of discharge centers within the receptive fields changed in relation to movement direction. No spatial area giving rise to the inhibitory component of response could be found in any of the neurons with monotone stationary structure of their receptive fields. Findings from experiments involving techniques of stimulating a test area of the receptive field separately indicated that inhibitory components of response in neurons of the lateral suprasylvian area with monotone organization of the receptive field could represent inhibitory after-response following the neuronal excitation produced by the visual stimulus traveling across this field.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 299–308, May–June, 1987.     

Visual cortical unit responses to photic stimulation of different zones of the receptive fields in cats

In acute experiments on unanesthetized curarized cats the intensity functions, response thresholds, inhibition thresholds, and differential sensitivity of 96 neurons in the primary visual projection cortex were investigated by extracellular recording of unit activity during central and peripheral stimulation of their receptive fields. In darkness the neurons had wide threshold and above-threshold reliefs (3–30°). The threshold reliefs of the receptive fields of some cells were found to be V-shaped, whereas others were marked by alternation of zones of increased and reduced excitability. Sensitivity of both excitatory and inhibitory inputs of the receptive field as a rule was greatest in the center. Inhibitory inputs of different cortical neurons were much more standard and less sensitive to light, and they were mainly activated within the intermediate (mesoptic) range of brightnesses. During light adaptation the threshold contour of the receptive field narrows sharply, mainly because of the fall in sensitivity of its peripheral inputs. Compared with the lateral geniculate body and retina, the relative number of low-threshold elements, sensitivity in the system of inhibitory elements, and differential brightness sensitivity are greater in the cortex. The mechanisms of formation of receptive fields of cortical neurons and their modification during changes in the level of adaptation, and also the role of excitatory and inhibitory inputs of the cell in these effects are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 11, No. 3, pp. 227–235, May–June, 1979.     

Somatosensory and visual cortical unit activity in rabbits during receptive field testing and food-getting behavior

Somatosensory and visual cortical unit activity was compared in experiments on unrestrained rabbits during receptive field testing and natural "self-stimulation" of the receptive surfaces of surrounding objects in the course of food-getting behavior. Unit activity evoked by receptive field testing may correspond completely, partially, or not at all to its activity during food-getting behavior, i.e., neurons demonstrating connection during testing with particular receptive fields (parts of the body or retina) may preserve it, modify it, or lose it during food-getting behavior. Differences of activity during food-getting behavior were observed even in the case of neurons with identical receptive fields during testing. The possible nonidentity of the overall firing pattern of the neurons during food-getting behavior with the pattern which can be simulated by receptive field testing is discussed.Institute of Psychology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 254–262, March–April, 1984.     

Characteristics of inhibition in receptive fields of the cat visual cortex

Unit responses of neurons of zone 17 in the cat striate cortex to stripes of different widths were studied. Changes in the number of spikes during different time intervals (cuts) from the beginning of the response were analyzed in relation to stimulus area. Comparison of the results with those obtained by the study of receptive fields of the lateral geniculate body showed a significant difference in the dynamics of inhibition between cortical and geniculate receptive fields. Similar results were obtained when cortical unit responses to simultaneous and consecutive appearance of two stripes in the receptive field, one in the excitatory zone and the other at the inhibitory periphery, were studied. Evidence of the longer duration of cortical inhibition also was obtained by the same technique. When both stripes were placed in the excitatory center of the field another feature of cortical inhibition was revealed: its dependence on the order of stimulus application. If the order of stimulus application coincided with the optimal direction of movement of the stripe for the given field, the unit response to the next stimulus was strongly facilitated by the action of the stimulus applied previously. Application of stimuli in the opposite order invoked inhibition. The sensitivity of inhibition to the order of stimulus application was observed in the center of the field; it diminished toward the periphery, where application of the stimuli in any order evokes inhibition of the response.Medical Academy, Sofia, Bulgaria, I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 339–346, July–August, 1977.     

Somatosensory cortical unit responses to stimulation of the vibrissae in cats

Characteristics of extra- and intracellular responses of 57 neurons in the vibrissal projection zone of the first somatosensory area of the cat cortex were investigated. The intensity of both excitatory and inhibitory unit responses was found to diminish during successive stimulation of different parts of the receptive fields in the direction from center toward periphery. Usually, when central parts of receptive fields were stimulated, inhibition in the unit responses was postexcitatory, whereas when peripheral parts were stimulated inhibition could precede excitation. The possibility of an increase in the role of interaction between excitatory and inhibitory processes arising in neurons in response to vibrissal stimulation with an increase in the distance from center to periphery of receptive fields of single cortical cells is discussed. Neurons found during one insertion of the microelectrode were seen to have common center for their receptive fields, but the diameters of the receptive fields of individual neurons could differ significantly. Moreover, during such vertical insertions responses of neurons with primary inhibition to the stimuli presented were recorded.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 124–130, March–April, 1980.     

Organization of receptive fields of motion-senstitive neurons in the cat pulvinar

The distribution of 70 visually sensitive neurons in the cat pulvinar sensitive to motion in the receptive fields was studied. The experimental results showed that components with directional characteristics are present in the structure of these fields of both direction-selective and unselective neurons. In the receptive fields of direction-selective neurons the directional elements of the substructure have identical preferred directions, which coincide with the preferred directions of response to stimulus movement over the entire receptive field. The organization of receptive fields of direction-selective neurons of the visual association structure thus does not differ significantly from that of analogous fields of visual projection neurons. Directional elements of the receptive fields of direction-unselective neurons were found to have different preferred directions, thereby providing a basis for organization of the nondirectional response of the neuron to a stimulus moving across the entire receptive field.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 339–346, July–August, 1982.     

Receptive fields of neurons in the lateral suprasylvian area of the cat

The structure of receptive fields of single neurons in the lateral suprasylvian area of the cat's cortex was studied. Receptive fields of neurons in this area are larger (up to 2000 deg² or more) than those of the visual projection cortex. A difference was found in the sizes of these fields of the same neuron when measured by presentation of a black object and spot of light. Experimental results showed that most neurons of the area (104 of 148) that are sensitive to visual stimulation respond clearly to flashes of a stationary spot of light. Because of this feature the structure of the receptive fields of the neurons were studied by point by point testing of their whole surface. Intensities of on- and off-components of on-off neurons were found to differ. Only 16% of receptive fields had equal numbers of discharges in on- and off-components of the on-off response. Dominance of one component was observed in 84% of on-off neurons. Receptive fields with several discharge centers are a characteristic feature of neurons in this area. A concentric organization of the receptive fields was found in 11% of neurons.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan, Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 278–283, May–June, 1982.     

Structure of receptive fields of cat pulvinar neurons sensitive to photic stimulation

Receptive fields of 262 pulvinar neurons were studied. Receptive fields of 142 of these neurons were studied in detail with the aid of a stationary spot of light, flashing in different parts of the receptive field. Depending on responses to presentation of the stationary stimulus the neurons were divided into six groups. The first group included neurons with on—off responses to photic stimulation (44 of 142), the second group neurons with off responses only (42 of 142). In cells of the third group (19 of 142) an on response only was recorded in all structures of the receptive field tested. Neurons of the fourth group (eight of 142) had a receptive field of similar structure to that of the simple receptive fields of neurons in cortical area 17. The fifth group (10 of 142) included neurons with a receptive field of concentric structure, the sixth (19 of 142) consisted of neurons with receptive fields with multiple discharge centers. The structure of the receptive field of these neurons was mosaic, with an irregular distribution of exciting and "silent" zones. The mean response latency of the pulvinar neurons was 40–70 msec. Responses of neurons with shorter (20 msec) and longer (130–160 msec) latent periods also were recorded.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 1, pp. 3–10, January–February, 1979.     

Responses and properties of receptive fields of neurons in the visual projection zone of the pigeon hyperstriatum

Unit responses in the hyperstriatal region of the pigeon forebrain to the action of various visual stimuli were investigated. Particular attention was paid to the discovery of retinotopic projection in the Wulst region. It was shown that as the electrode was advanced in the caudal direction in the zone of visual projection of the hyperstriatum the receptive fields of the neurons recorded shifted in the opposite direction in the visual field. The receptive fields of neurons of the ventral and dorsal hyperstriatum lie higher in the visual field and are larger in diameter than those of neurons of the accessory hyperstriatum. Unit responses in the visual projection zone of the Wulst depend on the intensity of illumination, size, and speed and direction of movement of the test objects across the receptive field. The functional role of the retino-thalamo-telencephalic system in visual interpretation in birds is discussed and it is suggested that the Wulst region is comparable with the striatal and also with the frontal regions of the mammalian cortex.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 230–236, May–June, 1976.     

Spatial frequency characteristics of receptive fields of neurons in the lateral suprasylvian area of the cat cortex

Two-dimensional spatial frequency characteristics of receptive fields of 46 neurons in the lateral suprasylvian area of the cat cortex were obtained. These receptive fields possessed orientation anisotropy. Peak frequencies lay in the frequency region below 1.5 cycles/deg. The transmission band width was measured during optimal orientation of test gratings in 21 neurons. It averaged 1.47±0.6 octave. In the remaining neurons the lower boundary frequency was shifted into the region of spatial frequencies below the range used. During nonoptimal orientation of test gratings, inhibition of the discharge was observed in 17 neurons. The inhibitory spatial frequency characteristics of six neurons were of the narrow band type, and averaged 1.1±0.6 octave.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 6, pp. 608–614, November–December, 1982.     

Responses of cat pulvinar neurons to moving visual stimuli

Responses of 114 pulvinar neurons to moving visual stimuli were studied. Most (79) neurons possessed spontaneous activity (10–25 spikes/sec). Of 59 neurons tested, 31 responded to stimulation of both retinas and 28 to stimulation only of the contralateral retina. Of 114 neurons, 41 responded only to movement of black objects, while the rest responded to movement of both black and light objects. According to the character of their responses to movement the neurons were divided into two main groups. The first group consisted of neurons sensitive to the direction of motion and responding with a spike discharge to movement in one direction and by inhibition to movement in the opposite direction. The second group included neurons insensitive to the direction of motion and responding by an equal number of discharges to movements in two opposite directions. Besides these two main groups, other neurons responding to movement in two opposite directions by discharges with different temporal distribution and also neurons which changed the character of their response from nondirectional to directional depending on the size of the moving stimulus, were found.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 10, No. 4, pp. 348–354, July–August, 1978.     

Structural organization of receptive fields of lateral suprasylvian cortical neurons in cats

The substructural organization of receptive fields of lateral suprasylvian cortical neurons, sensitive to movement of visual stimuli, was investigated in cats. The experimental results showed that receptive fields of neurons in this cortical area, judging by responses to movement, consist mainly of cells with qualitatively different characteristics. With the unmasked method of presentation of a moving stimulus, a reduction in the amplitude of movement as a rule evoked a directional response of the cell, whereas with the masked method, and with the same amplitudes of movement, a nondirectional response appeared. The receptive fields of some neurons were particularly sensitive to movement of borders but did not respond to the body of the stimulus like receptive fields of neurons described in other visual structures. Heterogeneity of the substructural organization of receptive fields of lateral suprasylvian cortical neurons can be explained by convergence of inputs on the neuron and it is regarded as the basis of integrative mechanisms in this structure.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 293–300, May–June, 1985.     

Asymmetry in structure of in termediate and large neurons of frog retinal ganglion layer

We have carried out a morphometric investigation of the symmetry of intermediate (type II) and large (types III and V) ganglion cells on silver-impregnated retinal wholemounts of frog retina. We selected the nucleolus of theneuron and the axis passing through the nucleolus in the direction of the optic disk (central and bilateral symmetry) as elements of symmetry. We have shown that the dendritic ramification angles of all cell types are smaller than 360° and those of type II cells smaller than 180°; the cell somata do not lie in the center of the dendritic field and consequently the ganglion cells do not possess radial symmetry. In the vast majority of ganglion cells the directions of the start of the axon and dendrites are opposite to each other, the dendrites being oriented in the direction from the retinal center towards the periphery in all quadrants of the retinal map. For the estimation of the bilateral symmetry we measured the distance from the most remote dendritic terminals to the axis on the left and right of the axis, and counted the number of ramification knots and basal dendrites. We established that the majority of ganglion cells are asymmetrical as regards two or three of the characteristics mentioned. Consequently the asymmetrical structure of ganglion cells of the frog is a normal characteristic rather than an exception. The correlation between the asymmetry of the structure of ganglion cells and the functional asymmetry of their receptive fields is discussed.N. I. Lobachevskii Research Institute of Applied Mathematics and Cybernetics, University of Gorki. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 456–462, July–August, 1985.     

Single cell responses from the optic tectum of the zebra finch (Taeniopygia guttata castanotis Gould)

Responses of neurons of the optic tectum, the prominent, highly laminated mesencephalic station of the tectofugal visual pathway in birds, to computer-generated and other visual stimuli were examined in zebra finches. Our study shows that the contralateral retina projects to the tectum in topographic order. The representation of the visual field is tilted against the horizon by 22°. The representation of the contralateral hemifield extends to the ipsilateral side by 15°. Most neurons have receptive fields with excitatory centres of different shapes and inhibitory surround. A new type of neuronal receptive field is described which has an excitatory centre and a surround which is movement sensitive and preferably excited by very small spots. The first type of neurons is mostly located in upper tectal layers, the latter only in deeper layers. Excitatory centre sizes increase with depth, and there is a tendency of smaller receptive fields in the foveal region. The representation of the frontal visual field does not show specializations which could be expected if it were used for fixation of grain during pecking. Our results are in accordance with previous behavioural experiments. Accepted: 30 April 1999     

Neurons with visual receptive fields independent of eye position in the caudal section of the ventral bank of cat cruciate slucus

Neurons responding to tactile and visual stimulation were found in the caudal section of the cruciate slucus ventral bank in awake cats. Tactile receptive fields were located on the face, mainly around the mouth. Visual stimuli evoked a response when presented close to the tactile receptive field. It was found that the visual responses of these bimodal neurons located in layer VI of the cortex display spatial consistency. The position of these visual receptive fields remained constant through saccadic eye movements, while still linked to the tactile receptive field.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neifofiziologiya, Vol. 18, No. 6, pp. 800–805, November–December, 1986.     

Contributions of short-wavelength cones to goldfish ganglion cells

Summary There are conflicting reports about the existence and nature of a short-wavelength cone (S-cone) contribution to ganglion cells in the goldfish retina. The present study sought to resolve these discrepancies by examining the S-cone contribution while recording from single ganglion cells in the excised, isolated goldfish retina. The effect of variations in the retinal preparation (gas content and type of background lighting during recording) on the S-cone input was also examined. Cells were classified into one of three types based on the responses at light onset and offset, when responses were driven only by the long-wavelength cone system (L-cones) of the receptive field's center (L+/–(on-excitation/off-inhibition) L–/+, and L+/+). With rare exceptions, the threshold spectral sensitivities of the centers and surrounds of cells that possessed opposite on and off responses (L+/–and L–/+) exhibited S-cone contributions, either prior to and/or during chromatic adaptation of the middle-and long-wavelength cones; the S-cone response was antagonistic to the L-cone input. The L + / + center cells also contained a S-cone input, but it was synergistic to the L-cone input at suprathreshold intensities. These findings were robust across all of the retinal preparations employed. The discrepancies in the previous work were probably due to the incomplete classification of cells because of the use of threshold responses only.This work is based in part on a dissertation submitted by RMM in partial fulfillment of the requirements for a PhD degree from the New School for Social Research, New York, New York     

Mechanism of directional selectivity of neurons with complex receptive fields in the cat visual cortex

Spatio-temporal interactions within complex receptive fields in the cat visual cortex were investigated by sequential presentation of two stationary stimuli. When two stimuli were presented in phase (on-on or off-off) in the order corresponding to preferred direction of movement, facilitation or weak inhibition of the response to the second stimulus was observed, whereas if it corresponded to zero direction of movement, the response was strongly inhibited. In the case of stimulation out of phase (on-off or off-on), in the order corresponding to the preferred direction of movement, considerable inhibition of the response to the second stimulus was observed, whereas in the opposite order, facilitation or weak inhibition was observed. The strength of interaction between different parts of the field depended on the distance between them and the duration of the interval between stimuli. Directional selectivity of "complex" neurons is thus ensured by asymmetry of spatio-temporal interactions between receptive field inputs of the same type. Interactions between inputs of different types, arising when a multiedge stimulus (bar, grating) can be used by the visual system to distinguish an object from the background and to assess changes in size of objects and the relative velocity of their movement.V. Kapsukas State University, Vilnius. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 505–512, July–August, 1984.     

Sensory input to neurons of the motor projection of biceps in the cat cortex

Correlation of cortical unit activity in the motor area for the biceps muscle was studied in chronic experiments on cats. In a group of neurons whose activity correlated with movement 68.1% of units had no sensory input from the working limb whereas in a group of neurons not correlating with movement there were 97.6% such units. In 24.2% of group I neurons cutaneous receptive fields of activation type were discovered on the distal part of the dorsal surface of the working limb. Five neurons responding to sensory input from the joints of the working limb were studied in this group.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 563–569, November–December, 1977.     

Orientation selectivity and spatial frequency characteristics of receptive fields of occipital cortical neurons in cats

Spatial frequency characteristics of receptive fields of occipital cortical neurons were investigated in cats during presentation of visual stimuli consisting of gratings in four or eight standard orientations. The maximal increase in discharge frequency of the neurons was observed when the grating was presented in one particular orientation, which was taken to be optimal for those particular neurons. Responses of some neurons to presentation of gratings in nonoptimal orientations were less than optimal; inhibition of activity below the spontaneous discharge level was observed in other cells in this case. Maximal inhibition was observed to the orientation perpendicular to optimal. Inhibition of unit activity evoked by presentation of gratings in the nonoptimal orientation was shown to be a function of spatial frequency.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 227–232, May–June, 1981.     

Receptive field dynamics of neurons in the cat visual cortex and lateral geniculate body

Spike responses of single neurons in the primary visual cortex and lateral geniculate body to random presentation of local photic stimuli in different parts of the receptive field of the cell were studied in acute experiments on curarized cats. Series of maps of receptive fields with time interval of 20 msec obtained by computer enabled the dynamics of the excitatory and inhibitory zones of the field to be assessed during development of on- and off-responses to flashes. Receptive fields of all cortical and lateral geniculate body neurons tested were found to undergo regular dynamic reorganization both after the beginning and after the end of action of the photic stimulus. During the latent period of the response no receptive field was found in the part of the visual field tested, but later a small zone of weak responses appeared only in the center of the field. Gradually (most commonly toward 60–100 msec after application of the stimulus) the zone of the responses widened to its limit, after which the recorded field began to shrink, ending with complete disappearance or disintegration into separate fragments. If two bursts of spikes were generated in response to stimulation, during the second burst the receptive field of the neuron changed in the same way. The effects described were clearly exhibited if the level of background illumination, the intensity of the test bars, their contrast with the background, duration, angles subtended, and orientation were varied, although the rate and degree of reorganization of the receptive field in this case changed significantly. The functional importance of the effect for coding of information about the features of a signal by visual cortical neurons is discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 14, No. 6, pp. 622–630, November–December, 1982.