ABSTRACT
Motor hand deficits impact autonomy in everyday life, and neuroplasticity processes of motor recovery can be explored using functional MRI (fMRI). However, few studies have used fMRI to explore the mechanisms underlying hand recovery following stroke. Based on the dual visuomotor model positing that two segregated dorsomedial and dorsolateral cerebral networks control reach and grasp movements, we explored the relationship between motor task-related activity in the sensorimotor network and hand recovery following stroke. Behavioral recovery was explored with a handgrip force task assessing simple grasp, and a visuomotor reaching and precise grasping task, the Purdue Pegboard Test (PPT). We used a passive wrist flexion-extension task to measure fMRI activity in 36 sensorimotor brain areas. Behavioral and fMRI measurements were performed in 27 patients (53.2 ± 9.5 years) 1-month following stroke, and then 6-month and 24-month later. The effects of sensorimotor activity on hand recovery were analyzed using correlations and linear mixed models (LMMs). PPT and handgrip force correlated with fMRI activity measures in the sensorimotor and parietal areas. PPT recovery was modeled by fMRI measures in the ipsilesional primary motor cortex (MI-4p), superior parietal lobule (SPL-7M) and parietal operculum OP1, and lesion side. Handgrip force was modeled by ipsilesional MI-4a, OP1, and contralesional inferior parietal lobule (IPL-PFt). Moreover, the relationship between fMRI activity and hand recovery was time-dependent, occurring in the early recovery period in SPL-BA-7M, and later in MI. These results suggest that areas of both dorsolateral and dorsomedial networks participate to visuomotor reach and grasp tasks (PPT), while dorsolateral network areas may control recovery of simple grasp (handgrip force), suggesting that the type of movement modulates network recruitment. We also found functional dissociations between MI-4p related to PPT that required independent finger movements and MI-4a related to simple grasp without independent finger movements. These findings need to be replicated in further studies.
