Electrophysiological Studies on the Otolith Organ

The mode of function of the otolith organ was investigated by recording action potentials from the first order neuron of the guinea pig. In the present experiment ‘nose-down’ unit was recorded more frequently than ‘nose-up’ unit, whereas ‘side-up’ unit was almost equal in number to ‘side-down’ unit. The reaction of the otolith organ was much influenced by tilting speed-more remarkable in slow tilt than in rapid one. Two different kinds of units were noted in sustained tilt, one showed remarkable adaptation and the other showed moderate adaptation. They were recorded in the ratio of 1:5. In galvanic stimulation every unit showed enhancement in cathodic stimulation and suppression in anodic stimulation. Two kinds of adaptation were also found in the same fashion as in tilting stimulation. It is the precent authors' working hypothesis that the difference of adaptation is due to different size of the nerve fibers.