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 nucleus on the lesioned side were studied during constant velocity off-vertical axis rotations, which selectively stimulated the remaining intact otolith receptors. During 360 degrees rotations, neurons exhibited position-dependent modulation in discharge rate, thus showing that the y group neurons receive signals of head positional changes from the contralateral otoliths. Most y group neurons had their best response orientations within +/- 45 degrees of the head-up and head-down positions (i.e. antero-posterior or pitch direction) in the plane of rotation studied. This implies that the spatial coding property of these otolith neurons enables them to be particularly catered for small head tilts about the sagittal plane of the animal.