Abstract
Eye movement is crucial to humans in allowing them to aim the foveae at objects of
interest. We examined the voluntary control of saccadic and smooth-pursuit eye movements
in 18 subjects with learning disorders (LDs) (aged 8–16) and 22 normal controls (aged
7–15). The subjects were assigned visually guided, memory-guided, and anti-saccade
tasks, and smooth-pursuit eye movements (SPEM). Although, the LD subjects showed normal
results in the visually guided saccade task, they showed more errors in the memory-guided
saccade task (e.g. they were unable to stop themselves reflexively looking at the
cue) and longer latencies, even when they performed correctly. They also showed longer
latencies than the controls in the anti-saccade task. These results suggest that they
find it difficult to voluntarily suppress reflexive saccades and initiate voluntary
saccades when a target is invisible. In SPEM using step-ramp stimuli, the LD subjects
showed lower open- and closed-loop gains. These results suggest disturbances of both
acceleration of eye movement in the initial state and maintenance of velocity in minimizing
retinal slip in the steady state. Recent anatomical studies in LD subjects have suggested
abnormalities in the structure of certain brain areas such as the frontal cortex.
Frontal eye movement-related areas such as the frontal eye fields and supplementary
eye fields may be involved in these disturbances of voluntary control of eye movement
in LDs.
Keywords
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Article info
Publication history
Accepted:
March 11,
2005
Received in revised form:
March 4,
2005
Received:
December 22,
2004
Identification
Copyright
© 2005 Elsevier B.V. Published by Elsevier Inc. All rights reserved.
