EFFECT OF CALORIC STIMULATION ON PRIMARY VESTIBULAR FIBERS ORIGINATING FROM OTOLITH ORGANS IN THE GUINEA-PIG

The influence of caloric stimulation on the primary vestibular fibers originating from the otolith organ was investigated in the guinea pig. Firing rates were recorded from single vestibular neurons in the supe rior vestibular (Scarpa's) ganglion which were identified physiologica lly as originating from the otolith organs, mainly from the utricles. Eighty-six percent of the neurons responded to caloric stimulation. Ne urons with a high coefficient of variation of firing regularity reacte d more sensitively to tilting and also had a tendency to react more se nsitively to caloric stimulation. There was a tendency for neurons wit h increased firing rates in response to ipsilateral tilting to have in creased firing rates to warm stimulation, while neurons whose rates in creased to contralateral tilting had increased firing rates to cold st imulation. These results indicate that the otolith organs have the sam e unidirectional tendency to caloric simulation with results comparabl e to optimal tilting directions.