Monaural Double Click Interactions at the Round Window, Eighth Nerve, and Inferior Colliculus of Cat

Abstract

These experiments study the interactions between successive, supra-threshold stimuli in the auditory nervous system of the anesthetized cat. Experiments have been carried out using two clicks to stimulate the ear of the anesthetized cat. The clicks were varied as to intensity and intra-click interval (delta interval). The effect of the first click upon the response to the second click was studied by measuring the electrophysiological response at the round window, eighth nerve, and inferior colliculus. The results obtained at the round window were different for the two components of the potential observed there. A smooth, monotonic recovery was found for the N1, whereas the recovery of the N2 between cats showed a depression for low-intensity click-pairs for delta intervals of 5 to 20 msec. Measurement of recovery at the inferior colliculus demonstrated three characteristics. An oscillatory component was observed. There was a difference in the relative recovery amplitudes of the evoked potentials which was related to the click intensity at short delta intervals. Finally a depression in recovery was observed which depended upon click intensity for delta intervals between 6 and 20 msec. (This work is supported by the Alfred P. Sloan Foundation and the National Institutes of Neurological Diseases and Blindness.)