Rizzo J, Hudson TE, Abdou A, Lui YW, Rucker JC, Raghavan
P and Landy MS (2017).
Front. Neurol. 8:12.
doi: 10.3389/fneur.2017.00012
Saccades
rapidly direct the line of sight to targets of interest to make use of the high
acuity foveal region of the retina. These fast eye movements are instrumental
for scanning visual scenes, foveating targets, and, ultimately, serve to guide
manual motor control, including eye-hand coordination. Cerebral injury has long
been known to impair ocular motor control. Recently, it has been suggested that
alterations in control may be useful as a marker for recovery. We measured eye
movement control in a saccade task in subjects with chronic middle cerebral
artery (MCA) stroke with both cortical and substantial basal ganglia
involvement, and in healthy controls. Saccade latency distributions were
bimodal, with an early peak at 60 msec (anticipatory saccades) and a later peak
at 250 msec (regular saccades). Although the latencies corresponding to these
peaks were the same in the two groups, there were clear differences in the size
of the peaks. Classifying saccade latencies relative to the saccade ‘go signal’
into anticipatory (latencies up to 80 ms), ‘early’ (latencies between 80 and
160 ms), and ‘regular’ types (latencies longer than 160 ms), stroke subjects
displayed a disproportionate number of anticipatory saccades, whereas control
subjects produce the m¬¬ajority of their saccades in the regular range. We
suggest that this increase in the number of anticipatory saccade events may
result from a disinhibition phenomenon that manifests as an impairment in the
endogenous control of ocular motor events (saccades) and interleaved fixations.
These preliminary findings may help shed light on the ocular motor deficits of
neurodegenerative conditions, results that may be subclinical to an examiner,
but clinically significant secondary to their functional implications.
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