Unit responses to moving stimuli in area 18 of the cat.

In paralyzed cats units were recorded from the peripheral projections on area 18. Of 46 cells, 71 percent responded to moving visual stimuli. From this sample 91 percent responded to velocities ranging from 5 to 400 degrees-sec(-1). Within this group, two classes of neurons could be distinguished. The first class had small receptive fields and responded repetitively to a moving grating. They had low spontaneous activity and were located in the superficial cortical layers. Random pattern movement elicited no response. The second class had large receptive fields and higher spontaneous activity. These neurons, found in the deeper layer of the cortex, responded better to slits than to grating. Responses to random pattern motion reached 50-100 percent of grating motion responses. A similar distinction holds for fast movement sensitive neurons of area 17. The identification of both these classes with simple and complex cells is discussed.