[Study of the mechanism of directionality of the receptive fields of the visual cortex in the cat].

The responses of directional-sensitive striate cortex neurons to two light bars one of which was located in the centre of the receptive field and the other--in the inhibitory zone were investigated in unanaesthetized cats. The order of presentation and the time intervals between the stimuli varied; so the presentation of the pair of stationary bars was an analog of a moving stimulus. It was shown that the inhibitory off-zone located on the side of the preferred direction of movement is characterized by an early inhibitory phase followed by a phase of disinhibition and by the second inhibitory phase. The presentation of a pair of stationary bars with different time intervals between them elicited inhibition when the central zone stimulation coincided with the inhibitory phases and facilitation when it coincided with the disinhibitory phase. For the inhibitory off-zone located on the side of the null direction no disinhibitory phase was found. The significance of the time characteristics of the inhibitory zones for the appearance of directional sensitivity in striate neurons is discussed.