Relationship between sensorimotor adaptation and cognitive functions in younger and older subjects.

We investigated whether deficits of adaptive improvement in seniors are related to an age-dependent decay of the brain's executive functions. Younger and older subjects completed a battery of cognitive tests, and preformed aimed arm movements before and during exposure to rotated visual feedback. In accordance with previous work, we found that adaptive improvement during exposure was degraded in seniors, while the transfer of adaptation to a new motor task was not. This pattern of findings confirms that strategic control but not sensorimotor recalibration is affected by old age. Using multiple linear regression (MLR) to extract separate executive components from our test battery, we found that basic response speed and decision-making, but not the inhibition of prepotent responses or mental flexibility, were degraded in our older subjects. Again using MLR, we found that degraded adaptive improvement in our seniors was partly related to the decay of basic response speed and decision-making, and partly to age-dependent phenomena not addressed by our cognitive-test battery. Finally, we observed that interindividual variability of cognition and adaptive improvement was larger in old than in young subjects, which could explain why some previous studies found degraded adaptation in seniors while others did not.