Udo Eversheim | PubMed Health

PubMed2003

Human adaptation to rotated vision: interplay of a continuous and a discrete process.

The mechanisms for adaptation to visual rotation were investigated by exposing subjects to different rotation angles in a stepwise fashion. We found that response direction continuously changed to compensate for the imposed rotation, but this change was limited to 90 deg. Larger changes were accomplished by inverting both spatial axes (which is equivalent to a 180 deg rotation), and then gradually changing response direction "backwards" to the prescribed value. The angle of 0 deg had no such limiting value like 90 deg: Response direction could continuously change through 0 deg and beyond. Our data provided no evidence that adaptation to opposite-directed visual rotations results in interference, due to competition in working memory; instead subjects' performance under such conditions is fully explained by the said continuous changes of response direction. We conclude that adaptation is achieved by a coordinated interplay of continuous (gradual rotation between +/-90 deg) and discrete (sign reversal) processes.

Adaptation, Physiological↗

PubMed2003

Sensorimotor performance and computational demand during short-term exposure to microgravity.

INTRODUCTION: Previous research suggests that human sensorimotor performance depends both on task difficulty, and on the allocation of the brain's computational resources to the task. We employ this view to analyze the changes of sensorimotor performance during the microgravity episodes of parabolic flight. METHODS: There were seven subjects who participated before, during, and after exposure to the microgravity episodes of parabolic flight. They performed a tracking task with one hand, and a four-choice reaction time task with the other hand, either alone or concurrently. Overall performance scores across tasks were calculated. RESULTS: Overall single-task performance deteriorated by about 50% microgravity, with little sign of recovery during the flight. Overall dual-task interference was more than twice as great at the onset of microgravity than at the onset of the 1-G baseline, but converged toward that baseline within about 4.5 min. CONCLUSIONS: Our subjects accepted a consistently poor level of sensorimotor performance throughout exposure to microgravity. To maintain that level, they increased the allocation of computational resources to the tasks at the onset of microgravity, but an increase was no longer necessary after 4.5 min of microgravity exposure. We take the initial increase as evidence of a brief phase of sensorimotor adaptation.

Adult↗