Motor timing learned without motor training.

Improvements due to perceptual training are often specific to the trained task and do not generalize to similar perceptual tasks. Surprisingly, given this history of highly constrained, context-specific perceptual learning, we found that training on a perceptual task showed significant transfer to a motor task. This result provides evidence for a common neural architecture underlying analysis of sensory input and control of motor output, and suggests a potential role for perception in motor development and rehabilitation.

Unequal weighting of monocular inputs in binocular combination: implications for the compression of stereoscopic imagery.

For efficient storage and transmission of stereoscopic images over bandwidth-limited channels, compression can be achieved by degrading 1 monocular input of a stereo pair and maintaining the other at the desired quality. The desired quality of the fused stereoscopic image can be achieved, provided that binocular vision assigns greater weight to the nondegraded input. A psychophysical matching procedure was used to determine if such over-weighting occurred when the monocular degradation included blur or blocking artifacts. Over-weighting of the nondegraded input occurred for blur, but under-weighting of the nondegraded input occurred for blockiness. Some participants exhibited ocular dominance, but this did not affect the blur results. The authors conclude that blur, but not blockiness, is an acceptable form of monocular degradation.

Reaching into cluttered visual environments: spatial and temporal influences of distracting objects.

Subjects reached for visual target lights in the presence of distractor lights. Previous studies (e.g., Tipper, Lortie, & Baylis, 1992) have shown that distractors at locations between the starting position of the hand and the target location caused greater interference (as indexed by response time) than distractors beyond the target. This finding has been attributed to the former distractors being in the path of the response to the target, but we provide evidence that they interfere more because of their proximity to the starting position of the hand (a "proximity-to-hand effect"). Also, distractors located in the hemispace ipsilateral to the responding hand caused more interference than contralateral distractors (an "ipsilateral effect"). The proximity-to-hand and ipsilateral effects were found in both reaction and movement time, suggesting that the resolution of the selection problem caused by a distractor could occur before or after movement initiation. Further evidence for this suggestion was provided by individual differences in movement initiation strategies which were predictive of the temporal locus of distractor influence. Errors of touching the distractor location also showed proximity-to-hand and ipsilateral effects. We discuss applications of these findings to real-world situations in which people reach for the wrong object in multiple-object visual displays.

Visuomotor processing in unilateral neglect.

The extent to which visual information on the contralateral, unattended side influences the performance of patients with hemispatial neglect was studied in a visuomotor reaching task. We replicated the well-established finding that, relative to target-alone trials, normal subjects are slower to reach to targets in the presence of visual distractors which appear either ipsilateral or contralateral to the target, with greater interference in the former condition. Six patients with hemispatial neglect showed even greater interference than did the normal subjects when the distractor appeared ipsilaterally but showed no significant interference from contralateral distractors. This pattern of performance was qualitatively similar for patients with lesions restricted to posterior regions and for patients with more extensive lesions involving both posterior and anterior brain regions. These findings suggest that, in the visuomotor domain, information on the contralateral side is processed minimally, if at all, in patients with hemispatial neglect.