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Modulation of saccade curvature by ocular counterroll


Weber, K P; Bockisch, C J; Olasagasti, M I; Straumann, D (2009). Modulation of saccade curvature by ocular counterroll. Investigative Ophthalmology and Visual Science, 50(3):1158-1167.

Abstract

PURPOSE: On close inspection, most saccadic trajectories are not straight, but curve slightly, i.e. they are not single-axis ocular rotations. We asked whether saccade curvatures are systematically influenced by static ocular counterroll (OCR). METHODS: OCR was elicited by static whole-body roll position. Eight healthy human subjects performed horizontal and vertical saccades (amplitude: 10 degrees ; eccentricity: 0 degrees and 10 degrees ; head-fixed coordinate system) in upright and ear-down whole-body roll positions (45 degrees right, 45 degrees left). Three-dimensional eye movements were recorded with modified dual search coils at 1000Hz. RESULTS: Saccade curvature was systematically modulated by OCR depending on saccade direction. In the horizontal-vertical plane, primarily vertical saccades were modulated with downward saccades curving towards the upper ear and upward saccades curving towards the lower ear. Modulation of saccade curvature in the torsional direction only correlated significantly with OCR in abducting saccades. CONCLUSIONS: No universal mechanism like visual-motor coordinate transformation or kinematical characteristics of the saccadic burst generator alone could explain the complex modulation pattern of saccade curvature. OCR-induced changes of the ocular motor plant, including transient force imbalances between agonist eye muscles (vertical rectus and oblique muscles) and shifting eye muscle pulleys, are suitable to explain the found direction-dependent modulation pattern.

Abstract

PURPOSE: On close inspection, most saccadic trajectories are not straight, but curve slightly, i.e. they are not single-axis ocular rotations. We asked whether saccade curvatures are systematically influenced by static ocular counterroll (OCR). METHODS: OCR was elicited by static whole-body roll position. Eight healthy human subjects performed horizontal and vertical saccades (amplitude: 10 degrees ; eccentricity: 0 degrees and 10 degrees ; head-fixed coordinate system) in upright and ear-down whole-body roll positions (45 degrees right, 45 degrees left). Three-dimensional eye movements were recorded with modified dual search coils at 1000Hz. RESULTS: Saccade curvature was systematically modulated by OCR depending on saccade direction. In the horizontal-vertical plane, primarily vertical saccades were modulated with downward saccades curving towards the upper ear and upward saccades curving towards the lower ear. Modulation of saccade curvature in the torsional direction only correlated significantly with OCR in abducting saccades. CONCLUSIONS: No universal mechanism like visual-motor coordinate transformation or kinematical characteristics of the saccadic burst generator alone could explain the complex modulation pattern of saccade curvature. OCR-induced changes of the ocular motor plant, including transient force imbalances between agonist eye muscles (vertical rectus and oblique muscles) and shifting eye muscle pulleys, are suitable to explain the found direction-dependent modulation pattern.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Otorhinolaryngology
04 Faculty of Medicine > University Hospital Zurich > Ophthalmology Clinic
04 Faculty of Medicine > Neuroscience Center Zurich
04 Faculty of Medicine > Center for Integrative Human Physiology
04 Faculty of Medicine > University Hospital Zurich > Clinic for Neurology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:March 2009
Deposited On:22 Jun 2009 15:34
Last Modified:05 Apr 2016 12:49
Publisher:Association for Research in Vision and Ophthalmology
ISSN:0146-0404
Publisher DOI:https://doi.org/10.1167/iovs.08-2453
PubMed ID:19011016

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