Frequency sensitivities of auditory neurons in the cerebellum of the cat.

Threshold tuning curves were obtained from neurons in the cerebellar auditory area of the cat. The threshold of the brainstem auditory evoked response was also measured in each animal as a function of sound frequency in order to monitor the overall frequency sensitivity of the auditory periphery. Cerebellar auditory neurons responded to sound stimuli with little discrimination for the sound frequency. The values of Q10dB (a measure of the sharpness of tuning) were less than 2 for most of the neurons in this study. There was no significant difference in the sharpness of tuning for neurons in the various layers of the cerebellar auditory area. Electrophysiological mapping showed that the frequency sensitivity of single neurons did not appear to vary as a function of location within the cerebellar auditory area which includes lobules VI and VII of Larsell. Broad tuning was observed in long-latency (greater than 11 ms) neurons which responded to binaural sound stimuli as well as in short-latency (less than 6 ms) neurons which only responded to monaural sound stimuli. Within each animal, tuning curves of single cerebellar neurons were essentially superimposable onto each other and matched well with the overall frequency sensitivity of the animal as shown by brainstem auditory evoked response. Since the frequency tuning of these neurons appeared to reflect the overall frequency sensitivity of the auditory periphery, auditory neurons in the posterior vermis may receive inputs that involve convergence and integration from the entire length of the cochlea.