Memory and coordination in bimanual isometric finger force production.

Isometric force output of the dominant hand has previously been shown to decline when feedback of that output is withdrawn. This effect is more pronounced for higher levels of force output, and appears to rely upon visuomotor memory processes. In the present study these existing findings are extended to a task where subjects produced force output with both the dominant and non-dominant hand, and with both hands together. The results suggested that force change following the withdrawal of feedback follows the same pattern in bimanual conditions as it does in unimanual conditions. In addition it was found that the proportion of the total force contributed by each hand in the bimanual condition varied through a trial, which was achieved without a corresponding drop in force output when feedback was available. Taken together, the results support the idea of a central representation for target force level, which, when available, makes use of visual information to control a mutually redundant pair of effectors.