Response characteristics of neurons in the cat vestibular nuclei during slow and constant velocity off-vertical axes rotations in the clockwise and counterclockwise rotations.

The responses to slow constant velocity rotations in the clockwise (CW) and counterclockwise (CCW) directions about an axis tilted 10 degrees from the earth's vertical were studied in static tilt-sensitive neurons in the vestibular nuclei of decerebrate cats. Each unit responded to any 360 degrees unidirectional rotation with a position-dependent discharge maximum. The location of the maximum, obtained by rotation in one direction, differed from that obtained by an oppositely directed rotation (phase difference). In about 80% of the units such phase difference (up to 160 degrees in second-order neurons) in response to oppositely directed rotations was unaffected by different amplitudes of head displacement (5-25 degrees). Units were thus classified into two groups depending on the location of the CW discharge maximum relative to the CCW counterpart. The direction of rotation had no influence on the response gains of these units.