Functional reorganization for movement of affected hand was induced in the contralesional hemisphere of the rat brain following focal ischemia

Saramu Momma1), Megumi Goto1), Tomoko Shimizu1), Takashi Mikami2), Akira Mitani1)

1) Neurorehabilitaion, Department of Human Health Sciences, Graduate School of Medicine, Kyoto University
2) Biotex Research Laboratory, Kyoto


Functional reorganization is induced in the brain after a series of rehabilitative training in limbs affected by stroke. Resent studies have indicated that contralesional hemisphere, intact hemisphere, is activated during movement of affected hand. However, the role of contralesional hemisphere in recovery of its motor function remains unknown. In the present study, we investigated the functional changes induced in the rat contralesional sensorimotor cortex following training of affected forelimb using intracortical microstimulation (ICMS) and multi-unit recording. Rats had completed the skilled reaching training (more than 90% of success score) and were randomly divided into three groups: training, non-training and sham. The training and non-training groups were subjected to photothrombosis on the sensorimotor cortex to affect trained forelimb, and the training group received retraining in which the rats were forced to use their affected hand by skilled reaching for 6 weeks. The motor function was evaluated periodically through skilled reaching training as a behavioral test. In behavioral test, the success score in the training group was significantly higher than that in the non-training group. ICMS applied in the contralesional hemisphere revealed that the threshold for ICMS-evoked affected hand movements decreased in the training group. Furthermore, we recorded multi-unit activities in the contralesional sensorimotor cortex with a telemetry system. The firing rate in the training group significantly increased during reaching movement. These results suggest that the contralesional sensorimotor cortex plays an important role in the motor recovery following training of affected hand.