Motor Control and Neural Plasticity through Interhemispheric Interactions
Figure 1
Changes in interhemispheric interaction and inhibitory noninvasive brain stimulation (NIBS) therapy in patients with subcortical stroke. (a) Mechanisms underlying the changes in interhemispheric interaction after stroke. In healthy subjects, the interhemispheric interaction changes from an inhibitory to an excitatory influence on the active motor cortex around movement onset. In contrast, stroke patients with motor deficits do not show this release from interhemispheric inhibition for the movement of the paretic hand; rather, they exhibit a persistent inhibitory influence on the ipsilesional motor cortex [34]. These pathological effects contribute to the reduced performance of the paretic hand. (b) Inhibitory NIBS over the unaffected hemisphere. Inhibitory NIBS decreases the excitability of the contralesional motor cortex and reduces the interhemispheric inhibition from the contralesional to the ipsilesional motor cortex. The excitatory interhemispheric interaction from the contralesional to the ipsilesional motor cortex might be relatively strong because of a reduced inhibitory influence. The change in interhemispheric interaction after inhibitory NIBS increases the excitability of the ipsilesional motor cortex. Facilitation of the ipsilesional motor cortex improves the motor function of the paretic hand in patients with subcortical stroke [99, 115]. However, it remains to be determined whether the excitatory interhemispheric interaction itself actually changes after inhibitory NIBS.
