Rôle of the Cat Superior Olive S Segment in the Processing of Auditory Neurophysiological Data

Abstract

S-segment cells with CF's above about 1.0 kHz receive inputs from each ear with the ipsilateral input being excitatory and the contralateral inputs from each ear with the ipsilateral input being excitatory and the contralateral input being inhibitory. Measurements on excitatory and inhibitory tuning curves disclose that the tonal frequencies that are capable of exciting a cell when presented to the ipsilateral ear are nearly identical to the frequencies that inhibit the cell when presented to the contralateral ear. Measurements on excitatory and inhibitory intensity functions reveal that the contralateral input is about as effective in determining the output of the cell as is the ipsilateral input, although in an opposite manner. When the two inputs are equal, there is little or no discharge from S-segment cells. Appreciable discharge results only when the ipsilateral input is greater than the contralateral input. The rôle of the S-segment is to extract dissimilarities from the signals present in the two inputs. Signals common to the two inputs are not transmitted.