A reexamination of the gain of the vestibuloocular reflex

Abstract

The properties of the vestibuloocular reflex (VOR) when the axis of rotation is behind the eyes and fixation of a near target is required were studied in the monkey. The magnitude of VOR gain in each eye was found to be above 1.0 and near the ideal value for stabilizing a retinal image. Evidence that this large VOR gain was not visually mediated was provided by the observations that no reduction in gain and no phase lag were observed at high frequencies of head rotation (2 Hz), large gain was observed in the dark, and large gain was observed within 10-20 ms of the start of head rotation. The magnitude of VOR gain was found to increase with increasing radius of head rotation and also to increase with decreasing target distance. When the distances from the two eyes to the target were different the instantaneous velocities and VOR gains of the eyes were also different. The dependence on radius of rotation indicates that the VOR is mediated by a combination of otolith and canal inputs. A general model for otolith-canal interaction is proposed in which VOR gain is based on a computation of target location relative to the head. This model simplifies to the classical VOR reflex when a cyclopean eye is subjected only to angular displacement.

Temporal dynamics of semicircular canal and otolith function following acute unilateral vestibular deafferentation in humans

“…Transient rotation at high acceleration has been employed in combination with eccentric rotation axes and different target distances in monkey (Snyder and King 1992) and in younger (Anastasopoulos et al 1996;Crane et al 1997;Crane and Demer 1998) and older humans (Tian et al 2001a). Rotation about eccentric axes can deliver significant otolith stimulation that is either synergistic or antagonistic with canal stimulation, and produces an effect on the VOR that varies systematically with target distance (Viirre et al 1986;Snyder and King 1992;Crane et al 1997;Crane and Demer 1998;Tian et al 2001a). As geometrically appropriate to gaze stabilization, VOR gain for rotation about an axis posterior to head is greater for near than for distant targets (Viirre et al 1986;Crane and Demer 1998;Tian et al 2001a), but is reduced for a near target for rotation about an axis anterior to head (Sargent and Paige 1991;Crane and Demer 1998;Tian et al 2001a).…”

“…Rotation about eccentric axes can deliver significant otolith stimulation that is either synergistic or antagonistic with canal stimulation, and produces an effect on the VOR that varies systematically with target distance (Viirre et al 1986;Snyder and King 1992;Crane et al 1997;Crane and Demer 1998;Tian et al 2001a). As geometrically appropriate to gaze stabilization, VOR gain for rotation about an axis posterior to head is greater for near than for distant targets (Viirre et al 1986;Crane and Demer 1998;Tian et al 2001a), but is reduced for a near target for rotation about an axis anterior to head (Sargent and Paige 1991;Crane and Demer 1998;Tian et al 2001a). The earliest component of the transient VOR of younger normal subjects is attributable to the semicircular canals and has a latency of 7-10 ms; it is independent of rotational axis and target distance .…”

The horizontal angular vestibulo-ocular reflex: A non-linear mechanism for context-dependent responses

“…It can be demonstrated geometrically that the magnitude of the ocular deviations required for compensating a translation of the eyes depends on the location of the fixation target relative to the observer. That is, the gain of the AVOR must increase as a function of decreasing fixation distance [2]. Holding gaze on a near target requires more ocular rotation than for a relatively far target during head movements since the eyes are not centered on the head.…”

Levels of Analysis of the Vestibulo-Ocular Reflex: A Postmodern Approach

“…Although the VOR has been thought of as a purely angular phenomenon, nearly all rotations of the head cause a physical translation of the eyes because the centre of rotation of the eyes are not on the axis of most head rotations. The VOR is sensitive to this (Biguer and Prablanc, 1981;Viirre and Demer, 1995;Viirre, Milner, Tweed and Vilis, 1986) and is even responsive to extending the distance between the eyes and the axis of head rotation (Snyder and King, 1992).…”

“…Deviations have been reported around pitch, roll and yaw axes (Biguer and Prablanc, 1981;Viirre and Demer, 1995;Viirre, Milner, Tweed and Vilis, 1986) but have been less well investigated in intermediate axes (but see Solomon, Straumann and Zee, 1997). We then altered the response around one axis and looked again at the variation of response amongst axes.…”