Journal of Neurophysiology, Vol 52, Issue 4 625-637, Copyright © 1984 by APS
Visual desynchronization of cortical EEG impaired by lesions of superior colliculus in rats
P. Dean, P. Redgrave and L. Molton
It is unclear whether rats with lesions of the superior colliculus (SC)
neglect visual stimuli because a) they fail to notice the stimuli or b)
they notice the stimuli but fail to make specific orienting movements of
the eyes and head toward them. To investigate this issue, we used an index
of "noticing" that does not involve overt orienting movements, namely,
desynchronization of the cortical electroencephalogram (EEG) in drowsy
animals. In the first experiment, large collicular lesions with some
invasion of surrounding areas severely impaired EEG desynchronization to a
brief overhead flash of light but did not significantly affect
desynchronization to brief bursts of white noise. No impairment was found
after control lesions of cerebral cortex overlying the superior colliculus
or of striate cortex. A subsequent experiment found that the visual
impairment was still present when lesions were confined to the superior
colliculus. It appears that rats with lesions of the superior colliculus
can, in certain circumstances, fail to notice visual stimuli and that in
rats, the superior colliculus is concerned not only with specific orienting
movements to visual stimuli but also with visual desynchronization of the
cortical EEG.
