Head and body hemispace to left and right III: Vibrotactile stimulation and sensory and motor components.

Response latencies were measured to vibrotactile stimulation delivered to the forefingers of the left or right hands which were positioned ipsilaterally or contralaterally (across the midline) in left or right hemispace. While the two hands did not differ in speed of response, either hand performed better when located in right hemispace (experiment 1). This effect was greatly reduced, though not eliminated, with 90 degrees lateral head turn, when performance was better with stimulation and responding in right-of-head hemispace, but not right-of-body hemispace (experiment 2). When different hands received stimulation and initiated responses, and were located in either the same or opposite hemispace, right-hemispace superiority was found to be motor rather than sensory (experiment 3). These findings are discussed in the context of the true and the phenomenological midline and the clinical syndrome of hemineglect.