State-dependent role of interhemispheric pathway for motor recovery in primates

Whether and how the interhemispheric pathway is involved in post-injury motor recovery is controversial. Unidirectional chemogenetic blockade of the interhemispheric pathway from the contralesional to ipsilesional premotor cortex impaired dexterous hand movements during the early recovery stage after lesioning the lateral corticospinal tract in macaques. Furthermore, electrocorticographical recording showed that the low frequency band activity of the ipsilesional premotor cortex around the movement onset was decreased by the blockade during the early recovery stage, while it was increased by blockade during the intact state and the late recovery stage. These results demonstrate that the action of the interhemispheric pathway changed from inhibition to facilitation, leading to the involvement of the ipsilesional sensorimotor cortex in hand movements during the early recovery stage. The present study offers new insights into the state-dependent role of the interhemispheric pathway and a therapeutic target in the early recovery stage after lesioning of the corticospinal tract.