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KMID : 1036520110010010065
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Clinical Neuro-Ophthalmology
2011 Volume.1 No. 1 p.65 ~ p.68
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Analysis of Smooth Pursuit Initiation Using Step-ramp Stimuli in Normal Subjects: A Pilot Study
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Kim Eui-Joong
Oh Sun-Young
Shin Byoung-Soo
Seo Man-Wook
Jeong Seul-Ki
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Abstract
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Background: Using step-ramp stimuli, the initiation of smooth pursuit was investigated in normal subjects.
Methods: We analyzed the onset latency and the initial acceleration during the first 100 ms of the horizontal smooth pursuit in 30 healthy subjects. In the rightward paradigm, the target was presented at the center for 0.5 seconds and moved 2.5° to the left (step) and began moving toward the right (ramp) with 3 target velocities (5°/sec, 10°/sec, and 20°/sec). Leftward paradigms were initiated with the target which is located center for 0.5 seconds moved to the right and then move to the leftward.
Results: Onset latency of pursuit appeared to be shortened as higher the target velocity. As target velocity progressively increased,acceleration of pursuit also increased. There were no significant directional differences in the latency and the acceleration of smooth pursuit between rightward and leftward movements. Older subjects showed significantly increased latencies at all frequencies and reduced initial accelerations at high frequency.
Conclusions: The target velocity of step-ramp paradigm appeared to affect on the latency and initial acceleration of pursuit system. The open-loop system of the pursuit was degraded in the elderly subjects. Decreasing sensitivity to retinal image motion or limiting the conversion of visual motion signals into commands for smooth pursuit might be the cause.
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KEYWORD
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Smooth pursuit, Step-ramp, Sinusoidal, Onset latency, Initial acceleration
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