Area 18 cell responses in cat during reversible inactivation of area 17.

1. A region of area 17 in the cat was temporarily inactivated by cooling, and cells in a topographically corresponding part of area 18 were studied during the blockage of area 17 input. 2. The responses of most area 18 cells were markedly reduced by cooling area 17 and recovered on rewarming primary visual cortex. 3. The selectivity of area 18 cells for oriented stimuli was not affected by inactivating area 17. These cells also, in general, retained their selectivities for the direction of stimulus movement and for the sign of contrast (light or dark) of a moving edge in the absence of input from area 17. 4. There was a greater decrease, on the average, of area 18 cell responses to slowly moving stimuli than to rapidly moving stimuli when area 17 was cooled; however, the exact pattern of change varied considerably from cell to cell. 5. These results suggest that cells in area 18 are to some degree dependent on input from area 17 for their responses, but to a large extent are independent in their selectivity for those stimulus parameters (orientation, direction of movement, sign of contrast) studied.