1. Probing the mechanism of saccade-associated head movements through observations of head movement propensity and cognition in the elderly.
- Author
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Thumser, Zachary C., Adams, Nancy L., Lerner, Alan J., and Stahl, John S.
- Subjects
SACCADIC eye movements ,COGNITION ,VISUAL perception ,HYPOTHESIS ,PSYCHOLOGY - Abstract
Humans may accomplish gaze shifts by eye-only saccades or combined eye–head saccades. The mechanisms that determine whether the head moves remain poorly understood. Many observations can be explained if phylogenetically ancient circuits generate eye–head saccades by default and frontal cerebral structures interrupt this synergy when eye-only saccades are preferable. Saccade-associated head movements have been reported to increase in the elderly. To test the hypothesis of frontal inhibition of head movements, we investigated whether the increase is associated with a decline in frontal cognitive function. We measured head movement tendencies and cognition in volunteers aged 61–80. Measures of head movement tendency included the customary range of eye eccentricity, customary range of head eccentricity, range of target eccentricities evoking predominantly eye-only saccades, and two measures of head amplitude variation as a function of target eccentricity. Cognitive measures encompassed verbal fluency, verbal memory, non-verbal memory, and executive function. There was no correlation between cognition and any measure of head movement tendency. We combined these elderly data with measurements of head movements in a group aged 21–67 and found mildly reduced, not increased, head movement tendencies with age. However, when confronted with a task that could be accomplished without moving the head, young subjects were more likely to cease all head movements. While inconclusive regarding the hypothesis of inhibition of saccade-associated head movements by cerebral structures, the results indicate the need to distinguish between mechanisms that define head movement tendencies and mechanisms that adapt head motion to the geometry of a specific task. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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