SINGLE-UNIT ACTIVITY IN THE INFERIOR COLLICULUS OF THE RAT ELICITED BY ELECTRICAL-STIMULATION OF THE COCHLEA

The activity of single neurons (n = 182) of the central nucleus of the inferior colliculus (CIC) of the rat was recorded in response to unil ateral electrical stimulation of the left cochlea and/or acoustical st imulation of the right ear. The probability of response to both modes of stimulation was comparable (90 per cent for contralateral and 60 pe r cent for ipsilateral presentation), Response patterns consisted pred ominantly of onset excitations. Response latencies to electrical stimu li ranged from 3 to 21 ms, with an average value of 9.7 ms (SD = 3.5 m s) in the ipsilateral CIC and 6.6 ms (SD = 3.4 ms) in the contralatera l CIC. With respect to binaural inputs, the majority of units were exc ited by stimulation of either ear (EE; about 60 per tent) while about one third were influenced by one ear only (EO). Units excited by one e ar and inhibited by the Ether (EI) were rare. The main difference betw een the present implanted rats and normal animals was the virtual abse nce here of inhibitory effects for both types of stimuli when they wer e delivered to the ipsilateral ear (very few EI units).