Characteristics of the VOR in response to linear acceleration.
The primate linear VOR (LVOR) includes two forms. First, eye-movement responses to translation [e.g., horizontal responses to interaural (i.a.) motion] help maintain binocular fixation on targets, and therefore a stable bifoveal image. The translational LVOR is strongly modulated by fixation distance, and operates with high-pass dynamics (> 1 Hz). Second, other LVOR responses occur that cannot be compensatory for translation and instead seem compensatory for head tilt. This reflects an otolith response ambiguity--that is, an inability to distinguish head translation from head tilt relative to gravity. Thus, ocular torsion is appropriately compensatory for head roll-tilt, but also occurs during IA translation, since both stimuli entail IA acceleration. Unlike the IA-horizontal response, IA torsion behaves with low-pass dynamics (with respect to "tilt"), and is uninfluenced by fixation distance. Interestingly, roll-tilt, like IA translation, also produces both horizontal (a translational reflex) and torsional (a tilt reflex) responses, further emphasizing the ambiguity problem. Early data from subjects following unilateral labyrinthectomy, which demonstrates a general immediate decline in translational LVOR responses, are also presented, followed by only modest recovery over several months. Interestingly, the usual high-pass dynamics of these reflexes shift to an even higher cutoff. Both eyes respond roughly equally, suggesting that unilateral otolith input generates a binocularly symmetric LVOR.
Paige
G D
GD
Department of Neurobiology and Anatomy, University of Rochester, New York 14642, USA. gary_paige@urmc.rochester.edu
Seidman
S H
SH
D000054:Acceleration; D000818:Animals; D008954:Models, Biological; D011187:Posture / Q000502:physiology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D014722:Vestibule, Labyrinth / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology