NEURONAL RESPONSES IN THE Y-GROUP NUCLEUS OF UNILATERALLY LABYRINTHECTOMIZED CATS DURING OFF-VERTICAL AXIS ROTATIONS

In cats which were decerebrated and unilaterally labyrinthectomized on the day of the experiment, the responses of neurons in the y group nu cleus on the lesioned side were studied during constant velocity off-v ertical axis rotations, which selectively stimulated the remaining int act otolith receptors. During 360 degrees rotations, neurons exhibited position-dependent modulation in discharge rate, thus showing that th e y group neurons receive signals of head positional changes from the contralateral otoliths. Most y group neurons had their best response o rientations within +/-45 degrees of the head-up and head-down position s (i.e. antero-posterior or pitch direction) in the plane of rotation studied. This implies that the spatial coding property of these otolit h neurons enables them to be particularly catered for small head tilts about the sagittal plane of the animal.