[The retinotopic organization of the posterior suprasylvian area of the cerebral cortex in the cat]. / Retinotopicheskaia organizatsiia zadnei suprasil'vievoi oblasti kory mozga koshki.

Posterior suprasylvian area (PSA) is one of the extrastriate visual structures of the cat cortex. Representation of the visual field in the PSA has been investigated by the mapping method. Results of experiments revealed that receptive fields (RF) of the PSA neurons were located mostly in the upper contralateral quadrant of the visual field. About 10% of RF were located in the upper ipsilateral quadrant of the visual field. In the upper PSA (21a, 21b) area centralis is mainly represented including the space of the radius of 20-30 degrees of the visual field. In the lower PSA (20a, 20b) more peripheral part of the visual field was represented. The experiments did not confirm essential differences in the retinotopic organization between areas 20a and 20b, 21a and 21b. Proceeding from the presented experiments the suggestion is put forward that PSA consists of two main areas (21 and 20) without dividing into subareas.

[Structure of receptive fields of visually sensitive neurons of the cat hippocampus]. / Stroenie retseptivnykh polei zritel'nochuvstvitel'nykh neironov gippokampa koshki.

Structure of receptive fields of visually sensitive neurons in areas CA1 and CA3 of the dorsal hippocampus was investigated in alert cats with the brain-stem pretrigeminal section. The receptive field (RF) structure of 76 hippocampal neurons was analyzed by methods of scanning the RF by moving stimuli and mapping all their surface by a stationary flashing spot. According to presented data the neurons were classified into three groups: neurons with homogeneous structure of the RF (54%), with nonhomogeneous (28%) and neurons more sensitive to stimulus motion (18%) than to a stationary flashing light. Experiments have shown that responses of hippocampal neurons are highly specific ones. Thus, 9% of neurons with the nonhomogeneous RF structure have shown specific responses to variation of the contrast and contours of moving stimuli. The presented results show that hippocampal visually driven neurons have well developed mechanism for processing visual sensory information and apparently this quality ensures participation of the limbic system in visually controlled behavior of the animal.

[Inhibitory components in responses of neurons of the lateral suprasylvian area of the cat cortex]. / Tormoznye komponenty v otvetakh neironov lateral'noi suprasil'vievoi oblasti kory koshki.

Inhibitory components of neuronal responses to moving visual stimuli in the lateral suprasylvian area of the cat cortex have been studied. Comparison of PST histograms of responses to two opposite directions of the movement allows revealing changes in the spatial localization of discharge centres in receptive fields relative to the movement direction. In all neurons investigated which revealed monotonous stationary structure of receptive fields no subregions coincidental with the inhibitory components of the responses are found. The presented experiments have promoted a conclusion that inhibitory components of responses of observed neurons could represent aftereffects following excitation of the cell when the stimulus is crossing the discharge centre of the receptive field.

[Responses of neurons of dorsal hippocampus field CA1 to visual stimulation in the cat]. / Otvety neironov polia CA1 dorsal'nogo gippokampa koshki na zritel'nye razdrazheniia.

In acute experiments on cats with pretrigeminal brain-stem section responses of 46 hippocampal neurons were investigated. Most neurons (71%) had small sizes of visual receptive fields. The responses of neurons to stationary stimuli were of phasic (66%), as well as tonic (34%) types. All neurons investigated responded to dark and bright spots moving across their receptive fields. 27% of sensitive neurons were direction-selective. Some neurons respond more intensively to moving dark spots in comparison with bright spots or bars. The results presented confirmed the suggestion that certain neurons in the CA1 field of the dorsal hippocampus have highly organized visual sensory input.

[Organization of the substructure of the receptive fields of neurons of the lateral suprasylvian area of the cat cortex]. / Organizatsiia substruktury retseptivnykh polei neironov lateral'noi suprasil'vievoi oblasti kory koshki.

The substructure of receptive fields of the lateral suprasylvian area neurons was investigated in cats. It was shown that the majority of receptive fields investigated were organized of subelements with different qualitative characteristics according to their responses to moving visual stimuli. With the unmasking method of stimulation, small amplitudes of the motion evoked, as a rule, directional responses, whereas with the masking method the same amplitude of the motion produced nondirectional responses. Some receptive fields of the investigated neurons responded vigorously to the motion of borders of the visual stimuli. The heterogeneity in organization of the substructure of the receptive fields was explained by the convergence of different inputs to the investigated neurons.

[Dynamic and static features of the receptive fields of neurons of the lateral suprasylvian area of the cat cortex]. / Dinamicheskie i staticheskie osobennosti retseptivnykh polei neironov lateral'noi suprasil'vievoi oblasti kory koshki.

Dynamic and static properties of neurons were investigated in lateral suprasylvian area of cat. It was shown that neurons with different dynamic characteristics could have the receptive fields with similar static organization. Thus strict correlation between static and dynamic organization of the receptive fields of suprasylvian neurons were not observed. The majority of black-sensitive neurons appear to have off-fields. The contrast reversal test of moving stimuli revealed that the generation of responses both to the light and to the black stimuli was performed by the same part of the receptive field and was not conditioned by the spatially separate on- and off-discharge centers in the receptive field.

[Organization of receptive fields of tonic and phasic neurons in cat pulvinar]. / Organizatsiia retseptivnykh polei tonicheskikh i fazicheskikh neironov podushki zritel'nogo bugra koshki.

The receptive fields of 26% out of 163 pulvinar neurons were characterized by phasic pattern of responses whereas those of 15% of neurons had tonic characteristics. The receptive fields of 59% of neurons consisted both of tonic and phasic subfields. These findings suggested convergence of two types of afferents on the same pulvinar neuron. The cell population receiving pure tonic or pure phasic afferents constituted 41% of all the neurons under study. The measurement of latencies of responses to the stationary flashing spot revealed that phasic responses had a shorter latency than tonic and mixed responses.

[Characteristics of neurons of the lateral suprasylvian region of the cat cerebral cortex sensitive to the movement of black stimuli]. / Osobennosti neironov lateral'noi suprasil'vievoi oblasti kory mozga koshki, chuvstvitel'nykh k dvizheniiu chernykh stimulov.

Visually sensitive neurons of the lateral suprasylvian area were investigated in cats with pretrigeminal brain stem sections. Nearly 25% of a neuron population responding to the visual stimuli revealed great sensitivity to movement of black stimuli across their receptive fields. These neurons were called "black-sensitive". As a rule, they had either a low-level or no background activity. Nearly 89% of these neurons revealed direction-selective properties. The most characteristic feature of "black-sensitive" neurons was a change in response patterns with the reversion of the stimulus contrast.

[Receptive fields of lateral suprasylvian neurons in the cat]. / Retseptivnye polia neironov lateral'noi suprasil'vievoi oblasti kory mozga koshki.

The receptive field structure of single neurons in lateral suprasylvian area was investigated in cat. Receptive fields were of larger sizes comparing with visual cortex (up to 2000 sq. deg.). The dimensions of receptive fields measured by black objects and light spots revealed differences, the receptive fields being usually larger when black objects were used. The experiments showed that the visually sensitive neurons of the lateral suprasylvian area could be activated by stationary flashing light stimulus. The neurons were qualified in three groups as on, off and on-off. Distribution of the activity all over the receptive field surface was investigated using flashing light spots. Receptive fields with the plural discharge centres were revealed.

[Responses of cat pulvinar neurons to stationary visual stimuli]. / Otvety Neironov pul'vinara koshki na statsionarnye zritel'nye stimuly.

The activity of 130 neurons in pulvinar was investigated using static visual stimuli (light spots of different dimensions flashing in the center of receptive fields, and diffuse flashing light). 50 neurons of 130 did not respond to light stimuli but only to the movement of black stimuli. The majority of investigated neurons revealed "on--off" types of reactions to the flashing light spot, 14 neurons gave "on" responses, and 28 -- "off" responses. The receptive fields of pulvinar neurons had mainly homogenous structure without center and antagonistic surrounding, although some of them appeared to have concentric type of receptive fields. Some neurons revealed responses similar to those of neurons in the Clare--Bishop area. The responses of such neurons were the regular bursts of discharges during the time of stimulation which suggests the compound structure of receptive field with elements of different latency.

[Structure of the receptive fields of cat pulvinar neurons sensitive to photic stimulation]. / Struktura retseptivnykh polei neironov pulvinar koshki, chuvstvitel'nykh k svetomu razdrazheniiu.

The structure of receptive fields of 262 neurons was studied in pulvinar. Of 262 neurons 142 were investigated in detail for receptive fields using stationary and dynamic visual stimuli. The receptive fields were classified into 6 groups according to the responses to the stationary light stimuli. The first group contained on-off receptive fields (44 of 142), all the investigated parts of which produced on-off responses to the flashing light spot. The second group (42 of 142) included neurons with the off-reactions from the whole surface of the receptive field. The third group comprised the on-receptive fields (19 of 142). Eight receptive fields (the fourth group) were similar to the "simple fields" of primary visual cortex. The fifth group (10 of 142 neurons) was characterized as concentric having on-off centre and on or off surrounding. The sixth group (19 of 142) included receptive fields with multiple discharge centres, the receptive field surface having silent zones for both on- and off-responses. The neurons having such receptive fields responded by multimodaly distributed discharges during the stimulation by moving and stationary visual stimuli. The average latency of responses of most neurons in pulvinar was 40-70 ms, some neurons displaying shorter (20 ms) and some longer (130-160 ms) latencies.

[Organization of neurons in the cat Clare-Bishop area which react to photic stimulation]. / Organizatsiia neironov oblasti Kler-Bishopa koshki, reagiruiushchikh na svetovoe razdrazhenie.

Organization of neurons in Clare-Bishop associative cortex was investigated by means of microelectrode vertical penetrations and recording of the neuronal responses to visual stimulation. Of 463 electrode penetrations 255 showed responses to visual stimulation. In 131 penetrations only 1 or 2 visually driven neurons were noted, in 55 cases more than 3 neurons were registered. Of 55 investigated penetrations 8 showed distinct columnar organization, i.e. all neurons in each column had similar characteristics. In 24 penetrations neurons were organized in groups of 2 or 3 similar neurons intermingled with neurons of other types. In 18 penetrations a great degree of overlapping of the receptive fields of neurons in a single column was observed. In 5 penetrations a chaotic organization of different neurons was found. A conclusion is made that the columnar organization of visually driven neurons as a functional cortical unit can not be regarded as a prominent feature in Clare-Bishop area.

[Responses of neurons in the Clare-Bishop cortical association area of the cat cerebral cortex to photic stimulation]. / Otvety neironov korkovoi assotsiativnoi oblasti Klera--Bishopa kory mozga koshki na svetovoe razdrazhenie.

In acute experiments on cats with protrigeminal section immobilized by flaxedil the electrical activity of single neurons in associative visual cortex of Clare-Bishop was investigated by the extracellular registration of their spike activity. 95.5% of investigated neurons responding to natural stimulation (light spots) were sensitive to the movement of stimulus through the receptive field. Nearly 55% of neurons exhibited selective responses to the direction of stimulus movement. Some neurones responded only when the stimulus was crossing the border points of receptive field. Nearly 85.3% of neurons responded to the flashing spot with "on", "on-off" and "off" reactions, and also to the stimulation by diffuse flashes. Receptive fields of neurons in the Clare-Bishop area were of strip-like form with longitudinal axis in horizontal orientation. Presented observations allow concluding that the Clare-Bishop cortical association area plays an essential role in the central processing of visual information.

[Responses of pulvinar neurons in cats to presentation of moving visual stimuli]. / Otvety neironov pulvinar koshki na pred''iavlenie dvizhushchikhsia zritel'nykh stimulov.

Responses of 114 pulvinar neurons to stimulation by moving light spots were studied. Most neurons (79) displayed background activity, the mean frequency of discharges being about 10-25 imp/s. 35 neurons showed no background activity, 41 neurons responded only to the movement of black stimuli, the rest being excited either by black or by light stimulus. The neurons were divided into two groups: those sensitive to the movement direction and those responding to two opposite directions of the movement by the equal numbers of discharges. A small number of neurons was observed responding to two opposite directions by regular bursts of spikes differently distributed in time (multimodal responses). Some neurons changed their nondirectional responses to the direction-sensitive ones after modifying the dimensions of the light spot.