Mechanisms of the interaction of the angular and linear components of the horizontal vestibulo-ocular reflex in the pigeon.

Intact pigeons (Columba livia, n = 30) were rotated in a horizontal plane in the dark at different orientations relative to the axis of rotation. A total of 24 birds showed different directions of changes in the duration of contrarotatory nystamus (on transition from central rotation to eccentric), along with displacement of the otolith membranes in both the frontal and sagittal planes. These pigeons showed a direct relationship between changes in the duration of the primary phase of nystagmus and the peak rate of the slow component on the background of increasing centrifugal force, while no such relationship was seen in conditions of decreasing centrifugal force. Increases in the duration of the primary phase were accompanied by decreases in the duration of the secondary phase (i.e., the reversive phase) and vice versa. These data provide evidence that the otolith component is not decreased to zero by rotation at constant angular rates or immediately after this stopped; in conditions of negative angular acceleration, this component was biphasic. The results are in good agreement with a hypothesis [2] suggesting that the otolith component represents asymmetric (different in paired brain structures) neuronal activity modifying the canal component even when the level of asymmetry is itself insufficient to initiate eye movements.