Auditory compensation of the effects of visual deprivation in the cat's superior colliculus.

Neurones in the superior colliculus of normal and visually deprived cats were analyzed for their responses to visual, auditory and somatosensory stimuli. The percentage of auditory-responsive cells throughout all layers had increased from 11% to 42% after binocular deprivation. Some auditory responses were found even in superficial layers. The number of somatosensory responses, though not systematically tested, was also higher in the visually deprived animals. Visually responsive units did not significantly decrease in number, thus resulting in an increased proportion of multisensory neurones. The vigour of auditory responses had increased after visual deprivation, while the vigour of visual responses had decreased significantly. In addition to the auditory effects of visual deprivation found, our study confirms previous findings on the visual effects of visual deprivation in the superior colliculus. Since only qualitative changes of visual responses, but no suppression of visual by non-visual activity was found, the neuronal mechanisms responsible for these changes may be different from competition as present in the visual cortex.