Motor Control in the Aging Brain: Bilateral Activation and Interhemispheric Communication

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Anderson, Emily M.
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Recent technological advances allowing scientists to view the brain in action have revealed exciting discoveries about structure-function relationships of the human brain. One area where neuroimaging has been particularly illuminating is the study of the process of aging. Although it was traditionally thought that aging resulted in irrevocable cerebral deterioration, recent evidence (Gross, 2000; Kempermann, Kuhn, & Gage, 1998) has suggested that the adult brain is capable of cerebral cell birth and plasticity. This evidence is promising for the field of cognitive aging because it suggests that the brain may be able to compensate for the structural and biochemical changes that occur as a result ofthe aging process. In fact, many recent neuroimaging studies have revealed that cognitive tasks that show highly lateralized brain activation patterns in young adults (i.e., right hemisphere or left hemisphere activation) show bilateral brain activation patterns in older adults (i.e., activation of both left and right hemispheres). This bilateral activation appears to be compensatory, as studies suggest that it is related to task performance. This finding is known as HAROLD [hemispheric asymmetry reduction in older adults] (Cabeza,2002). Although this bilateral activation pattern is well documented for brain regions recruited for many cognitive tasks, it is unknown whether this pattern occurs only in the prefrontal regions supporting cognitive behaviors, or whether HAROLD is a more general phenomenon that might also be observed during sensorimotor tasks. The current study examines whether bilateral activation is also observed for sensorimotor tasks in addition to cognitive tasks, and whether it reflects functional compensation. In addition, the current study explores whether this pattern of bilateral activity is dependent upon interhemispheric communication. In this paper, I will review the evidence for the HAROLD model, evidence for the applicability of the HAROLD model to motor control, and the role of interhemispheric communication. I will then present the current study and discuss its implications for the field of cerebral aging.
v, 54 p.
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