Brainstem mechanisms of otolith-visual interaction in the control of eye movement produced by sinusoidal vertical linear acceleration

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Eye movement responses were examined in alert during sinusoidal vertical linear acceleration at 0.20-0.85Hz with an amplitude of 10.5cm (corresponding to 0.02-0.31g). Sinusoidal linear acceleration in the light produced robust eye movement responses with near compensatory phase at all stimulus frequencies tested. In the dark, however, only small responses with advanced phase (by 70ﾟ) were obtained. Optokinetic stimulation alone produced more lag of response phase with smaller gain as stimulus frequency increased. Linear acceleration in cats that had received bilateral labyrinthectomies resulted in more phase lag at higher stimulus frequencies and decreased gain at all frequencies tested. These results indicate that the interaction of otolith and visual inputs produces robust eye movement responses with near compensatory phase during sinusoidal linear acceleration in the light.To examine brainstem mechanisms for this interaction, neuronal activity was recorded in the interstitial nucleu … More s of Cajal (INC) and vestibular nuclei (VN). Activity of all eye movement-related burst-tonic (BT) and tonic (T) neurons in the INC was modulated in correlation to eye movement responses in the light. However, in the dark, most of them (84%) did not respond. The remaining cells responded to linear acceleration ; their mean phase values advanced by 801 and gain dropped by 55% compared to the responses in the light. These results suggest that the otolith-visual interaction occurs before the level of these neurons. Many INC cells other than BT and T cells responded to linear acceleration in the dark and optokinetic stimulation, indicating that these cells received otolith and visual inputs. Responses of some of these cells during linear acceleration in the light could be explained by addition of otolith and visual inputs. Many VN cells that responded to pitch rotation, including cells with vertical eye position sensitivity, did not respond to linear acceleration in the dark. A minority of VN cells responded to linear acceleration in the dark. These results suggest that the otolith-visual interaction may occur both in the INC and VN at neurons that do not have eye position sensitivity. Less