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UBC Theses and Dissertations

Low-level and high-level motion perception in children with unilateral amblyopia Paul, Pamela S.


It has been suggested that there are two motion systems: (1) a passive, low-level motion system that automatically signals motion and has been linked to the directionally selective neurons of primary visual cortex and the medial temporal area (MT) and (2) an active, high-level motion system that is engaged by tracking the visible features of a stimulus by actively attending to it (Cavanagh, 1992). This thesis tests the possibility that the high-level motion system is selectively disrupted in amblyopia. Amblyopia is a developmental visual disorder characterised by reduced visual acuity in an otherwise healthy, properly refracted eye. It is usually associated with deficits in spatial vision. Recent work suggests that visual attention may also be disrupted and the status of motion perception is an unresolved issue. The present study assessed 13 children with unilateral amblyopia and 24 age-matched controls on one low-level motion task and four high-level motion tasks. Children with amblyopia showed similar performance to controls in both eyes (the amblyopic eye and non-amblyopic, fellow eye) on a low-level motion coherence task and two high-level motion tasks: apparent motion and visual search. Performance on a single-object tracking task was depressed in the amblyopic eye. Children with amblyopia showed depressed performance in both eyes on a multiple-object tracking task. These results suggest that there is a preservation of low-level motion perception in amblyopia, while children with amblyopia have deficits at attentively tracking multiple targets.

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