Visuomotor adaptation to a gradual or sudden screen cursor rotation was investigated in healthy young and elderly subjects. Both age groups were equally divided into two subgroups; one subgroup was exposed to 11.25° step increments of visual feedback rotation, every 45 trials (up to a total of 90°), whereas a second subgroup was subjected to 90° rotation from the onset of exposure. Participants performed discrete, horizontal hand movements to virtual targets in four randomized directions. Targets appeared on a computer screen in front of them, and a board prevented vision of the hand at all times. Differential effects of aging on visuomotor adaptation were found, depending on the time course of the visual distortion. In both age groups, early exposure to the sudden visual feedback distortion resulted in typical spiral-like trajectories, which became straighter by late exposure. However, the final adaptation level was reduced in the aged group, although the aftereffects were similar. When subjects were exposed to the gradual distortion, no statistically significant differences in measures of adaptation with advancing age were found. In this case, both age groups appeared to adapt equally. However, after removal of the distortion, elderly subjects showed reduced aftereffects as compared with the young group. These findings suggest differential effects of aging on adaptation to gradual versus sudden visual feedback distortions, and may help to explain the conflicting results obtained in previous visuomotor adaptation studies

For 8 different groups of Ss, individual patterns from sets of either 4-, 3-, or 2-alternative patterns were shown to each S under 2 conditions in a forced-choice recognition task. In one condition, exposure duration was varied by E and thresholds were determined for each pattern. In the other condition, choice reaction times (CRT) were obtained, measured from stimulus onset to S's key press. It was predicted and found that the order of CRTs would parallel the order of thresholds in each combination of patterns. This finding supports the assumption that the time required to receive spatial information sufficient to distinguish patterns is an identifiable component of CRT.

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