Binaural Reverberatory Responses in Medial Geniculate Free

Neurons in lower auditory nuclei generally respond for a period no longer than the duration of the stimulus. Medial geniculate neurons that responded in such fashion fell into two categories: those responding with one or two spikes to the onset and those responding with a secondary burst as well, which terminated abruptly at the stimulus offset. The latter type evidenced complex binaural interaction. Other neurons showed response durations longer than stimulus durations. These responded with an onset burst followed by reverberatory volleys whose duration was independent of stimulus duration. Changes in the stimulus caused independent variations in the characteristics of the onset and reverberatory responses. Inhibitory influences lasting for several hundred milliseconds are partially responsible for reverberation, and level of anesthesia was shown to be an important parameter. Finally, some neurons were found to respond to the first five or six stimuli of a repetitive train, failing to respond again unless a stimulus parameter was varied. The reverberatory medial geniculate responses may be related to various psychophysical phenomena. [Supported by U. S. Public Health Service grants to G. Moushegian.]