Binaural-Click Analysis by Brain-Stem Auditory Neurons

Abstract

Previous studies have shown that medial superior-olivary (accessory nucleus) units of cat show a decrease in probability of response and an increase in latency when stimulated by binaural clicks of appropriate intensive and time differences. Recent findings from the same medullary region reveal a complex synaptic organization of neurons, some of which are differentially responsive to large and some, as previously reported, to small interaural time differences. The former units, which show binaural interactions to large time differences (ca. 10 msec), are driven consistently by both monaural left and monaural right clicks. When, however, binaural clicks with large time disparities are delivered, the response probabilities to both clicks are significantly decreased. Some of the units that show binaural interaction to small time differences regularly fire twice to a monaural click. These units, in contrast to the former ones, discharge only to one ear stimulation, never to both. To binaural clicks, either one of these spikes or both may be inhibited as time or intensive differences of the clicks are systematically changed. The spike latencies also of both responses are dependent upon these parameters of the clicks.