Not all brain regions are created equal for improving bimanual coordination in individuals with chronic stroke

• Published in: Clinical neurophysiology Vol. 130; no. 8; pp. 1218 - 1230
• Main Authors: Liao, Wan-wen, Whitall, Jill, Wittenberg, George F., Barton, Joseph E., McCombe Waller, Sandy
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2019
• Subjects: Adult; Aged; Arm rehabilitation; Bimanual coordination; Cluster analysis; Contralesional dorsal premotor cortex; Female; Functional Laterality; Hand - physiopathology; Humans; Male; Middle Aged; Motor Cortex - physiopathology; Motor Skills; Repetitive transcranial magnetic stimulation; Stroke; Stroke - physiopathology; Cluster analysis; Contralesional dorsal premotor cortex; Stroke; Repetitive transcranial magnetic stimulation; Bimanual coordination; Arm rehabilitation
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2019.04.711

•Patients with greater arm/hand impairment improved bimanual coordination with facilitation of contralesional dorsal premotor cortex (cPMd).•Patients with fewer arm/hand impairment improved bimanual coordination with facilitation of ipsilesional primary motor cortex (iM1).•Wrist/hand function and the interhemispheric inhibition strength seem to affect responses to cPMd and iM1 facilitation. The now standard cortical stimulation approach of inhibiting contralesional primary motor cortex (cM1) disrupts bimanual coordination while facilitating ipsilesional M1 (iM1) fails to enhance paretic arm function, in severely impaired individuals. We propose an alternative target, enhancing contralesional dorsal premotor cortex (cPMd) to improve bimanual coordination and compare its effects to iM1. Fourteen participants with stroke received 5-Hz repetitive transcranial magnetic stimulation (rTMS) on cPMd or iM1 in a repeated cross-over design. Bimanual force/neuromuscular coordination and cortical excitability were assessed. We also examined the relationship of baseline motor function/interhemispheric inhibition (IHI) to participant’s responses to each stimulation target. We identified two patterns of responses. Participants with more severe impairment and weaker IHI improved bimanual force/neuromuscular coordination, ipsilesional activations and reduced IHI after cPMd-rTMS; whereas, those with milder impairment and stronger IHI improved only after iM1-rTMS. Cortical stimulation protocols could be tailored to the types of tasks and to individuals’ severity of impairment. Facilitation of cPMd may improve bimanual coordination especially for individuals with limited arm/hand function. Our study is the first to identify cortical stimulation strategies for improving bimanual coordination for individuals with different level of severity of stroke.