Abstract
Averaged responses to photic stimuli were recorded from single cortical cells in a circumscribed small region of the nonstriate area (F0-3 and L2-3 in H-C coordinates) of cats. The retinas were stimulated monocularly by various stimuli, such as a diffuse light flash, an intermittent light spot, or a moving light slit, of different sizes and shapes under various conditions of dark and light adaptations. Studies were made on a total of 86 units.
1) The cortical cells had relatively large receptive fields, usually about 20°C×20°C. They were responsive to a diffuse flash, and responsiveness was influenced by background illumination.
2) The responses of 27 units to a moving slit were suppressed and those of 13 units were facilitated by background illumination.
3) Four units showed a reversal of the preferred direction.
4) Three units that had no preferred orientation in the dark developed it in the presence of background illumination.
5) The response patterns of 39 units were unaltered by background illumination.
