Binaural Interaction in the Cat Superior Olive S Segment

Abstract

With the exception of low-frequency characteristic frequency (CF) units, the ipsilaterally evoked discharge of the majority of S-segment cells can be inhibited with simultaneous stimulation of the contralateral ear. The contralateral inhibitory CF is usually identical to the ipsilateral excitatory CF. The width of the contralateral inhibitory tuning curve is similar to the width of the ipsilateral excitatory tuning curve. Partial inhibition of the ipsilaterally evoked discharge increases the interspike intervals and increases the variability of the discharge. Inhibition, like excitation, is tonically acting. The contralateral inhibitory input with equally intense tones (measured in terms of decibels above threshold) is either about as effective as the excitatory input or less effective, rarely more effective. The primary factor determining the spike output from S-segment cells is not the absolute intensity level of the stimulus but rather the relative intensity difference of the stimulus at the two ears. [Work supported in part by National Institutes of Health, U. S. Department of Health, Education, and Welfare.]