Responses of single units in cerebellar vermis of the cat to monaural and binaural stimuli.

The responses of 146 cerebellar neurons to tone stimuli were studied in 29 cats anesthetized with chloralose-urethan and in 7 decerebrate preparations. Units were classified as onset or sustained firing. Onset spikes occurred on stimulation of either ear and showed binaural facilitation, while sustained discharges were frequently only excited by monaural stimulation. The latent periods of sustained discharges appeared to be shorter than those of onset responses, and sustained discharges were also more sharply tuned than the onset units. Evidence was presented suggesting that onset responses reflected input from the inferior colliculus and sustained responses, the cochlear nucleus. The sterotyped facilitatory behavior of onset units suggested that a maximal discharge might occur if sounds were of equal intensity at each ear; 26 neurons were examined with variable interaural time or intensity differences and 10 of these exhibited maximal firing when the interaural time and intensity difference was zero--i.e., if the sound was located directly in front of the head.