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Quick phases of infantile nystagmus show the saccadic inhibition effect

Harrison, James J., Sumner, Petroc, Dunn, Matthew, Erichsen, Jonathan Thor and Freeman, Thomas Charles Augustus 2015. Quick phases of infantile nystagmus show the saccadic inhibition effect. Investigative Ophthalmology and Visual Science 56 , pp. 1594-1600. 10.1167/iovs.14-15655

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Abstract

Purpose: Infantile nystagmus (IN) is a pathological, involuntary oscillation of the eyes consisting of slow, drifting eye movements interspersed with rapid reorienting quick phases. The extent to which quick phases of IN are programmed similarly to saccadic eye movements remains unknown. We investigated whether IN quick phases exhibit 'saccadic inhibition', a phenomenon typically related to normal targeting saccades, in which the initiation of the eye movement is systematically delayed by task-irrelevant visual distractors. Methods: We recorded eye position from 10 observers with early-onset idiopathic nystagmus while task-irrelevant distractor stimuli were flashed along the top and bottom of a large screen at ±10° eccentricity. The latency distributions of quick phases were measured with respect to these distractor flashes. Two additional participants, one with possible albinism and one with fusion maldevelopment nystagmus syndrome, were also tested. Results: All observers showed that a distractor flash delayed the execution of quick phases that would otherwise have occurred around 100 ms later, exactly as in the standard saccadic inhibition effect. The delay did not appear to differ between the two main nystagmus types under investigation (idiopathic IN with unidirectional and bidirectional jerk). Conclusions: The presence of the saccadic inhibition effect in IN quick phases is consistent with the idea that quick phases and saccades share a common programming pathway. This could allow quick phases to take on flexible, goal-directed behaviour, at odds with the view that IN quick phases are stereotyped, involuntary eye movements.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Optometry and Vision Sciences
Psychology
Publisher: Association for Research in Vision and Ophthalmology
ISSN: 0146-0404
Last Modified: 10 Dec 2017 06:21
URI: http://orca.cf.ac.uk/id/eprint/70601

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