Long-term forced-use therapy after sensorimotor cortex lesions restores contralesional hand function and promotes its preference in Macaca mulatta.

Injury to one cerebral hemisphere can result in paresis of the contralesional hand and subsequent preference of the ipsilesional hand in daily activities. However, forced use therapy in humans can improve function of the contralesional paretic hand and increase its use in daily activities, although the ipsilesional hand may remain preferred for fine motor activities. Studies in monkeys have shown that minimal forced use of the contralesional hand, which was the preferred hand prior to brain injury, can produce remarkable recovery of function. Here we tested the hypothesis that long-term forced use of the contralesional hand during the post-lesion period can return it to preferred status. Four rhesus monkeys received tests of hand preference prior to surgical lesions of primary motor cortex, lateral premotor cortex and anterior parietal cortex (F2P2 lesion) contralateral to the preferred hand. Beginning two weeks after the lesion, forced use therapy involving contralateral hand reaches to acquire food targets occurred 3X weekly with at least 300 reaches/session until 24 weeks post-lesion. Despite initial paresis of the contralesional hand, its manipulation skill returned to near pre-lesion levels or higher and all four monkeys returned to a contralesional hand preference late in the post-lesion period. Favorable reorganization of spared cortical and subcortical neural networks may promote recovery of hand function and preference. These results have relevance for the use of extensive forced-use therapy in humans who experience unilateral periRolandic injury to potentially support better recovery of contralesional hand function.