title: Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation.
abstract: The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.
authors.affiliation: Dept. of Neurology, Mount Sinai School of Medicine, New York, NY 10029, USA. sergei.yakushin@mssm.edu
authors.forename: Sergei B
authors.initials: SB
authors.lastname: Yakushin
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D005133:Eye Movements / Q000502:physiology; D006112:Gravitation; D019416:Head Movements / Q000502:physiology; D008252:Macaca fascicularis; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*