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.     

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.     

Investigation of functional organization of receptive fields in the cat visual cortex

Receptive fields of neurons in Area 17 of the visual cortex were investigated in cats. Concentrically shaped fields, fields responding selectively to orientation of a strip or edge, and fields which can be regarded as intermediate between the first two types are described. The boundary between zones of summation and of lateral inhibition coincides in some receptive fields with the boundary between central and peripheral zones with opposite forms of response, while in other fields they do not coincide. For some cells there is no peripheral zone or it may disappear with worsening of the state of function. Cells were observed for which an increase in area of the stimulus in the central zone inhibits the response reaction. Analysis of these data suggests that several cells of the geniculate ganglion converge on some cortical neurons, and several cortical cells on others. An effect of adaptive inhibition was found in which constant illumination of an area in the center of the receptive field inhibits the response in another part. It is shown that this effect is unconnected with the action of scattered light. Constant illumination of the peripheral part of the receptive field deinhibits adaptive inhibition. The boundary between the zones of summation and of lateral inhibition coincides with the boundary between the zones of adaptive inhibition and deinhibition.I. V. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 90–100, July–August, 1969.     

Dependence of functional organization of receptive fields of the cat lateral geniculate body on visual stimulus contrast

The spatial organization of receptive fields of the lateral geniculate body in response to visual stimuli with different degrees of contrast was studied in cats. During variation of contrast changes in organization of the central zone were found to take place in some receptive fields. Inside the central zone of the receptive field as revealed by the use of low stimulus contrasts, an additional inhibitory ring appears in response to a stimulus of high contrast. The weighting function of the central zone of the receptive field becomes variable in sign. The role of this phenomenon in transmission of information on high spatial frequencies (increase in visus) at high contrasts is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 789–796, November–December, 1984.     

Effect of removal of corticofugal influences on receptive fields of lateral geniculate neurons in the cat

Unilateral division of corticogeniculate connections increases the number of spikes in unit responses of the ipsilateral lateral geniculate body to receptive field stimulation and potentiates the effects of lateral inhibition. The area of the zone of complete summation of all lateral geniculate neurons recorded on the side of operation depends on contrast of the local photic stimulus. It is concluded that cortical fibers descending to the lateral geniculate body are inhibitory in nature and that the existence of receptive fields with a variable zone of spatial summation is due to intrageniculate mechanisms.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 7, No. 5, pp. 486–492, September–October, 1975.     

Inhibitory zones of receptive fields of the lateral geniculate body and visual cortex of the cat

Unit responses to moving strips were investigated. The organization of the inhibitory zones in the receptive fields of the lateral geniculate body and visual cortex of the cat was compared. The response in the receptive field of the lateral geniculate body was inhibited only during simultaneous stimulation of the excitatory and inhibitory zones of the field. Stimulation of the inhibitory zone in the receptive field of the visual cortex was effective for a long time (several hundreds of milliseconds) after stimulation of the excitatory zone. The inhibitory zones of the simple and complex receptive fields of the visual cortex differed significantly. An increase in the width of the strip above the optimal size reduced the inhibitory effect in the complex fields. This was not observed in the simple receptive fields. The functional and structural models of the receptive field of the visual cortex are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 201–209, March–April, 1973.     

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.     

On the characteristic of nonlinear spatial summation observed in the lateral geniculate cells of cats

The spatial summation characteristic in the receptive fields of cat lateral geniculate cells were investigated. First, the central area of the receptive field was determined using a spot of light. Then the response of the cell were obtained using disc-shaped stimuli of various radii located in the middle point of the receptive field center. When the radius was increased gradually, the response tended to increase, at first, until it reached a peak value and began to decrease thereafter. The radius where the peak response took place was generally less than that of the receptive field center. Furthermore, this radius decreased when the intensity of the stimulus light was increased. These neurophysiological findings could be simulated by a model. The model consists of two parts. The first part receives the input from the photoreceptors. It is of homogeneous structure with shunting inhibition. The second part receives the input from the first part. The structure is characterized by the conventional center-surround type lateral interaction.     

Stimulus size selectivity and receptive field organization of ectostriatal neurons in the pigeon

The avian ectostriatum is the telencephalic recipient zone of the tectofugal pathway, which may be homologous to the colliculo-pulvinar-cortical pathway in mammals. The present paper studies the visual response properties and receptive field organization of ectostriatal cells in pigeons with extracellular recording and computer mapping techniques. The results indicate that 90% of ectostriatal cells prefer forward, downward and upward motion of visual stimuli at velocities in the range of 16-128 degrees s(-1). They respond optimally to small stimuli (1-4 degrees visual angle), mostly preferring a target of 2 degrees. Most cells (78.8%) have one excitatory receptive field that usually possesses one or two hotspots, some cells (13.5%) have two excitatory receptive fields each having one or two hotspots, and a few cells (7.7%) have one excitatory receptive field with an unresponsive region in the center. An inhibitory receptive field is not found surrounding the excitatory receptive field in the ectostriatal cells examined. These response properties and receptive field organization may reflect the possible roles of the ectostriatum in stimulus discrimination and visual cognition.     

Unit responses in the cat auditory cortex to electrical stimulation of nerve fibers innervating receptor cells in different parts of the organ of corti

Responses of 200 primary auditory cortical neurons to electrical stimulation of nerve fibers in different receptor zones of the cochlea were studied in cats anesthetized with pentobarbital. Under the influence of paired stimulation, after the response to the conditioning stimulus a state of prolonged (from 4 to 200 msec) refractiveness to the second stimulus developed in all the neurons tested. This long-lasting inhibition of unit activity was due to inhibition developing in the thalamus and the auditory cortex itself. The intensity and duration of excitation and inhibition in the cortical projection focus were maximal when the center of the receptive field was stimulated and decreased when the stimulus shifted from the center to the periphery. The region of the receptor surface of the cochlea to stimulation of which the auditory cortical neurons respond by an action potential is much narrower than the region whose electrical stimulation depresses the discharge of these neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 418–425, July–August, 1982.     

Orientation-selective neurons in the squirrel visual cortex

The organization of receptive fields of neurons sensitive to orientation of visual stimuli was investigated in the squirrel visual cortex. Neurons with mutually inhibitory on- and off-areas of the receptive field, with partially and completely overlapping excitatory and inhibitory mechanisms, were distinguished. Neurons of the second group are most typical. They exhibit orientation selectivity within the excitatory area of the receptive field because, if the stimulus widens in the zero direction, perpendicular to the preferred direction, lateral inhibition is much stronger than if it widens in the preferred direction. Additional inhibitory areas (outside the excitatory area) potentiate this inhibition and increase selectivity. It is suggested that there is no strict separation of simple (with separate excitatory and inhibitory mechanisms in the receptive field) and complex (with overlapping of these mechanisms) neurons in the squirrel visual cortex.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 11, No. 6, pp. 540–549, November–December, 1979.     

Rabbit visual cortical neurons with simple and complex receptive fields

Receptive fields of neurons of the rabbit visual cortex selective for stimulus orientation were investigated. These receptive fields were less well differentiated than those of the analogous neurons of the cat visual cortex (large in size and circular in shape). Two mechanisms of selectivity for stimulus orientation were observed: inhibition between on and off zones of the receptive field (sample type) and oriented lateral inhibition within the same zone of the receptive field (complex type). Lateral inhibition within the same zone of the receptive field also took place in unselective neurons; "complex" selective neurons differed from them in the orientation of this inhibition. A combination of both mechanisms was possible in the receptive field of the same neuron. It is suggested that both simple and complex receptive fields are derivatives of unselective receptive fields and that "complex" neurons are not the basis for a higher level of analysis of visual information than in "simple" neurons.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 13–21, January–February, 1978.     

A functional model of the wiring of the simple cells of visual cortex

A computer model of the simple cells in the mammalian visual cortex was constructed. The model cells received inputs from a great number of isopolar centre/surround cells assumed to be located in the lateral geniculate nucleus (LGN). The distribution of input to the model simple cells was either inhibitory/excitatory or inhibitory/excitatory/inhibitory. Such arrangements produced receptive fields containing four or five consecutively antagonistic subfields. Responses produced by the model cells to different types of stimuli (periodical as well as nonperiodical) were obtained and compared to responses of living cells reported from various laboratories under comparable stimulus conditions. In all the situations tested, the responses of the model cells corresponded qualitatively very well to those of living cells. It was seen that the same wiring mechanism was able to account for orientation selectivity, spatial frequency filtering, various phase relationships between stimulus and response, subfield orientational selectivity, and slight end-inhibition. Furthermore, the receptive fields of the model simple cells closely resemble Gabor functions.     

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.     

Temporal pattern discrimination within the receptive field of cat retinal ganglion cells

ON-center and OFF-center receptive fields of cat retinal ganglion cells can be divided into two categories: sensitive (type N) and insensitive (type L) to three statistical temporal visual stimuli with different second order statistics but identical first order statistics (Tsukada et al. 1982). The temporal pattern sensitivity of type N response is closely related to the nonlinear stage of Y cells depending on the interaction between center and surround mechanism. The temporal pattern sensitivity of type N responses has a spatial profile within the receptive field; it is highly sensitive in the center region of the receptive field and less sensitive toward the field periphery. The temporal pattern sensitivity in the center region of the receptive field to statistical properties (irregular or regular) of a surrounding flash annulus shows modulation like a switching element: when the surrounding area is stimulated by a more regular flash stimulus with normal distribution of inter-stimulus intervals the system is sensitive (switching on) to the temporal pattern, while a change to an irregular one with an exponential distribution makes it insensitive (switching off) to the temporal pattern.     

Characteristics of dynamic reorganization of receptive fields of cortical and geniculate visual neurons of cat in response to changes in photic stimulation parameters

The effect of parameters of local photic stimulation of different points of the receptive field on the characteristics of dynamic reorganization of receptive fields of cortical and geniculate visual neurons within microintervals of time observed previously was studied in computer-controlled experiments on unanesthetized, curarized cats. Dependence on the degree of widening of the receptive field and the temporal characteristics of this process on the background illumination level, intensity, contrast, area, duration, energy, and orientation of a local rectangular or circular photic stimulus flashing in random order at 100 points of the tested part of the visual field was studied. It was concluded that the background illumination level and the intensity, size, duration, and orientation of the stimulus have a specific effect on dynamic reorganization of the receptive field. The effects of all the parameters studied on the dynamics of the receptive field were shown to be nonlinear functions with optimal values that differed for different cells. The possible functional role of this effect and also the probability that it may participate in information coding in the visual system are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 15, No. 4, pp. 339–346, July–August, 1983.     

High-frequency (300-800 Hz) components in cat geniculate (dLGN) early visual responses.

We analysed the early visual responses of relay cells of the dorsal part of cat lateral geniculate nucleus (dLGN) for the occurrence and characteristics of high-frequency (>300 Hz) spike patterns comparable to the high-frequency oscillations (HFO) found in the human somatosensory system. By using a special algorithm for correcting response latency, we can show that the vast majority of dLGN visual responses which were elicited by a sudden change in contrast show HFOs in the range of 300 to more than 800 Hz. After response time correction these HFOs are clearly visible in summed responses, indicating that these patterns are highly reproducible by identical stimuli. On this basis we analysed the HFOs in more detail. We found the oscillation frequency to increase with stimulus contrast and the area of the receptive field centre covered by an excitatory stimulus. Inhibition reduces the oscillation frequency as demonstrated with additional stimulation of the antagonistic surround of the receptive field and by blocking inhibition with micro-iontophoretical application of bicuculline methiodide. The HFO was almost independent of the state of the system as estimated from the EEG pattern. Based on these findings we discuss whether bursts of action potentials triggered by the low-threshold calcium spike (LTS) can contribute to this pattern of visual thalamic activity.     

Principle of neuronal organization of defensive reflexes in mollusks

Spontaneous and evoked synaptic activity of command neurons for the defensive response of spiracle closing were studied by simultaneous intracellular recording of activity of several identified CNS neurons in snails. Comparison of monosynaptic EPSPs in command neurons evoked by discharges of presynaptic neurons with spontaneous synaptic potentials indicated that the central organization of the defensive reflex is in the form of a two-layered neuron net in which each neuron of the afferent layer possesses a local receptive field, but which overlaps with other afferent neurons. Each neuron of the afferent layer is connected with each neuron of the efferent layer by monosynaptic excitatory connections that differ in efficiency (maximal only with one neuron of the efferent layer). Both receptive fields of neurons of the afferent layer and "fields of efficiency of synaptic connections" are distributed according to the normal law. As a result of this organization the neuron net acquires a new quality: The action of different stimuli leads to the appearance of differently located "spatial excitation profiles" of efferent layer neurons even when this action of the stimulus occurs not at the center of the receptive field.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 26–34, January-February, 1984.     

Structure of the simple receptive field of the cat visual cortex

Comparison of unit responses of simple receptive fields of the cat visual cortex (area 17) to presentation of sinusoidal gratings and thin light and dark bars showed that excitatory and inhibitory on- and off-zones of the field are composed of on- and off-subfields of the lateral geniculate body converging on the cortical neuron. Each zone is formed by a pair of opposing subfields, activation of one of which gives an excitatory, and the other, an inhibitory effect. This organization is evidence that the simple field has linear properties. However, a real simple field is not a linear system because of deviations from the ideal organization described above, namely displacement of the subfields relative to each other, nonhomogeneity of the properties of the subfields, and absence of an antagonistic subfield in one of the zones. Even within the same field phasic and tonic subfields may be present.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 4, pp. 339–344, July–August, 1981.     

Responses of nervous elements of the visual cortex of the chipmunk Eutamias sibiricus to moving and stationary stimuli]

The receptive field organization of cortical units has been studied in experiments with testing by moving and stationary light spots. The size of the receptive fields varied from 3 degrees to 10 degrees. Receptive fields which were tested by a stationary light spot exhibited various types of organization. Some of the neurons produced extensive excitatory on- and off-responses to stimulation by a light spot. Neuronal excitation evoked by light decreased if the stimulus was near the field boundary. Some of the neurons produced either on- or off-responses in any point of the receptive field. A small part of neurons had receptive fields with on- and off-reactions in the center, and either on- or off-responses at the peripheral zones. Most of the neurons exhibited specialization with respect to high-speed motion.