Investigating factors that influence motor imagery-related brain activation after stroke

Motor imagery (MI), the mental rehearsal of a movement, activates sensorimotor brain regions and shows promise as an intervention for motor recovery after stroke. However, the factors that influence how the brain responds to MI after stroke, such as sex, MI ability, and repeated MI exposure, remain poorly understood. The current research aimed to address factors influencing the variability in MI-related brain activation observed after stroke. This overall aim was addressed through two experiments. In Experiment 1, participants with chronic stroke performed a single MI session of a complex upper-limb task with their paretic limb while undergoing functional magnetic resonance imaging (fMRI). Overall, MI-related brain activation was observed across sensorimotor regions. Group-level contrasts considering the impact of sex revealed greater activation in sensorimotor regions for females vs. males, while greater activation in cerebellar and parietal regions was noted in males vs. females. Females also recruited greater ipsilesional regions vs. males. MI ability was associated with brain activation localized to occipital regions. Our findings suggest that females and males may respond differently to MI-based tasks. Further, we did not find a relationship between questionnaire-based kinaesthetic MI-ability data and activity in sensorimotor regions. Experiment 2 followed the same experimental design, except participants returned for a second session of MI inside the scanner. Group-level contrasts revealed a more focal pattern of brain activation in Session 2 vs. Session 1 (9 regions vs. 30 regions, respectively). MI-related brain activation in Session 2 vs. Session 1 was primarily localized to sensorimotor regions involved in MI. Collectively, this work illustrates the variable brain response to MI after stroke and may help advance knowledge of how to effectively prescribe MI interventions after stroke.