[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.

[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.

The fine structure of the receptive fields of visually driven neurons in the cat's lateral suprasylvian area.

The fine structure of the receptive fields of the lateral suprasylvian area neurons was investigated in the pretrigeminal cat preparation. A majority of the receptive fields consisted of subregions with different qualitative characteristics according to their response to moving visual stimuli. There was an asymmetry in the spatial distribution of inhibitory mechanisms over the receptive field. The steady illumination of the receptive field usually enhanced the inhibitory processes, whereas darkness, decreased the effectivity of inhibitory influences on the neuron. Some receptive fields of neurons reacted vigorously to the motion of borders of visual stimuli. It is suggested that the differences in response patterns to moving stimuli depend in part on the heterogenous fine structure of their receptive fields.

Dynamic and static properties of neurons in the lateral suprasylvian area of the cat.

The response properties and receptive field organization of 106 LSA neurons were investigated in pretrigeminal preparations using moving dark and bright stimuli with particular reference to the dynamic and static structure of receptive fields. About 61percent neurons revealed equal sensitivity to the motions of dark and bright stimuli. A majority of them had an ON-OFF static structure of receptive fields. Nearly 24 percent of cells had higher sensitivity to the motion of dark stimuli in comparison with the bright ones. Their receptive fields constituted the OFF-uniform spatial distribution when tested by stationary flashing lights. No clear-cut correlations were found between the static and dynamic properties of LSA neurons. It was shown that the same region of the receptive field is responsible for the reactions to dark or bright moving stimuli. A group of dark-sensitive neurons (24 percent of the total) was described, some examples of which had no stationary receptive fields at all.