Continuous Theta Burst Stimulation Inhibits Contralesional Parietal and Occipital Activity During Imagined Movements After Stroke

ABSTRACT Repetitive transcranial magnetic stimulation, when paired with skilled motor practice, shows promise for motor recovery after stroke via modulation of cortical excitability. After stroke, continuous theta burst stimulation (cTBS) has been used to reduce excitability in the contralesional cortex. In theory this increases excitability in the homologous motor area in the ipsilesional motor cortex. However, the response to cTBS is inconsistent. In turn, it is difficult to understand the broader impact of cTBS on brain activity after stroke. Here, 30 participants with middle cerebral artery stroke (> 6 months post-stroke; nine females; 68 ± 13 years; 15 left hemisphere stroke) underwent both active and sham cTBS applied over the contralesional primary motor cortex, in counterbalanced order across individuals. Before and after cTBS, participants completed a functional magnetic resonance imaging experiment where they engaged in a motor imagery (the mental rehearsal of a movement) task involving opening a door with their stroke affected arm/hand. Continuous TBS led to reduced activity (pre > post) in parietal and occipital brain regions including the calcarine sulcus, cuneus, precuneus, and posterior cingulate cortex during motor imagery. No changes in brain activity were observed following sham stimulation. These findings suggest that cTBS can decrease activity in regions involved in higher-order or compensatory visuospatial processing. Overall, this work furthers our understanding of how cTBS influences brain activity in individuals with stroke, which is critical to inform the use of cTBS as a potential therapy for individuals with stroke.