RESPONSES OF SINGLE UNITS OF THE CAT VISUAL SYSTEM TO RECTANGULAR STIMULUS PATTERNS

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Abstract
Microelectrode measurements were made of responses of single units of the visual system of the cat to rectangular light patterns in various positions and orientations. Evidence is cited for the presence, in cortex, of on- and off-cells with concentric field organization like that found in the optic tract and lateral geniculate body. On-cells were maximally excited when their receptive field centers were illuminated by the higher luminance portion of a contrast pattern, near a boundary with a darker region. Off-cells were maximally excited when their field centers corresponded to the darker region of a stimulus pattern adjacent to a boundary with a lighter region. Number of spikes in response to onset of a stimulus of this kind was greater than the number occurring in the off-response following illumination of the field center at a higher level. Some off-cells were found which give neither an "on" nor "off" response in a small, well-defined region of the visual field, but showed on-inhibition and off-activation in the visual field around this region. A number of cells, presumably all cortical, responded only to elongated patterns of stimulation in certain orientations, or to moving stimuli with specific motion direction.