Role of the interhemispheric interaction for recovery after spinal cord injury

We found that macaque monkeys with lesion to the corticospinal tract at the C4/C5 show significant recovery of precision grip in several weeks (Sasaki et al. 2004). Here, the ipsilesional sensorimotor cortices increased the activity and contributed to recovery during the early recovery phase (Nishimura et al. 2007). More recently, we demonstrated that the functional connectivity from the contralesional to ipsilesional premotor cortex (PM) increased during the recovery by mathematical analysis of large-scaled ECoG data (Chao et al. 2019). Here, to prove the role of interhemispheric pathway, we unidirectionally blocked the interhemispheric pathway from the contralesional PM to the ipsilesional PM with chemogenetic techniques combined with the double viral vector technology (Kinoshita et al. 2012), and found that the recovering dexterous hand movements were impaired and the movement-related activity in the motor cortex was declined. Thus, the above hypothesis on the role of the interhemispheric pathway was demonstrated.