Microelectrode study of superior olivary nuclei

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Abstract
The superior olivary nucleus of barbiturate anesthetized cats was explored with microelectrodes. Both slow wave and single unit activity was recorded to clicks, tones and noise delivered to the two ears. The several segments of the superior olivary complex (e.g. the n. accessorius and n. trapezoid body, to mention 2 of the 5) are differently innervated from the two ears, and the physiological findings correlated well with the known anatomical data. In response to tones most units displayed a best frequency and a response area here as elsewhere in the auditory system. Intensity increase aroused more activity from most units and brought additional ones into action, but several important exceptions to this rule were studied. Units in n. accessorius proved to be exquisitely sensitive to whether the right ear or the left was stimulated first by paired clicks; the unique physiological and anatomical characteristics of these cells seem relevant to the binaural sound localization problem. Several lines of evidence, finally, suggest the existence of a class of units concerned chiefly with preserving the exact time of arrival of stimuli at the cochlea, this class being different in important ways from those dealing with tone-frequency mediation.