Journal of Neurophysiology, Vol 41, Issue 1 55-64, Copyright © 1978 by APS
Nonequivalent visual, auditory, and somatic corticotectal influences in cat
B. E. Stein
1. The effects of cortical cooling on the responses of cells to visual,
somatic, and acoustic stimuli were studied in the cat superior colliculus
(SC). When the visual cortex was cooled, the responses of many visual cells
of the SC were depressed or eliminated, but the activity of nonvisual cells
remained unchanged. This response depression was found in visual cells
located in both superficial and deep laminae and was most pronounced in
neurons which were binocular and directionally selective. 2. Cooling
somatic and/or auditory cortex had no effect on visual SC cells and, with
few exceptions, did not alter the activity of somatic or acoustic cells
either. 3. The specificity of visual cortex influences on visual responding
in the SC was most apparent in multimodal cells. In trimodal cells, the
simultaneous cooling of visual, somatic, and auditory cortex eliminated
responses to visual stimuli, but did not affect responses to somatic or
acoustic stimuli. Visual responses were returned to the precooling level in
both unimodal and multimodal cells by cortical rewarming. 4. The present
experiments indicate that despite the organizational parallels among
visual, somatic, and acoustic cells of the cat SC, the influences they
receive from cortex are non-equivalent. Cortical influences appear to play
a more critical role in the responses of visual cells than in the responses
of somatic and acoustic cells. These observations raise questions about the
functional significance of nonvisual corticotectal systems.
