Abstract
The effect of vestibular efferent system stimulation on the vestibular action potential (VAP) recorded after brief mechanical ampullopetal stimulation of the lateral canal crista was studied in the cat. When an inhibitory action was recorded it had an effect on the VAP component N2 potential and was also characterized by a positive post potential. When stimulation seemed to have no effect, computer averaging showed a weak facilitating action affecting the N1 potential. The hypothesis of a double efferent system is discussed.