Response of medullary reticular neurons of cat to off-vertical axis rotations

Abstract

To investigate whether neurons in the medullary reticular formation of decerebrate cats can encode spatial orientation during 360° off-vertical axis rotations (OVAR), responses of these units were studied during constant velocity OVAR in clockwise (CW) and counterclockwise (CCW) directions. Tilt-sensitive units, some of which were activated by antidromic stimulation of the thoracic cord, were found to respond to 360° OVAR with position and direction-dependent modulation in discharge rates. For the individual responsive unit there was a difference in the spatial location of the CW and CCW discharge maxima, while a comparable response gain was obtained for rotations in either direction. The orientation of the best response of each unit was not significantly modified by changes in the amplitude of head tilt and/or velocity of rotation. Such characterized directional axes of the medullary reticular units were found to have a fairly equal distribution over the 360°. The role that neurons in the medullary reticular formation plays in encoding otolith inputs with respect to head movements is discussed.