Greater Activation of Secondary Motor Areas Is Related to Less Arm Use After Stroke

Abstract

Background. Past studies have identified reorganization of brain activity in relation to motor outcome through standardized laboratory measures, which are quantifiable surrogates for arm use in real life. In contrast, accelerometers can provide a real-life estimate of arm and hand usage. Methods. Ten persons with chronic, subcortical stroke and 10 healthy controls of similar age performed a squeeze motor task at 40% maximum voluntary contraction during functional magnetic resonance imaging (fMRI). Use of the upper extremity was quantified over 3 consecutive days using wrist accelerometers. Correlations were performed between arm use and peak percent signal change (PSC) during grasp force production in 6 regions of interest (ROIs): bilateral primary motor cortex (M1), supplementary motor area (SMA), and premotor cortex (PM). Results. Results demonstrate that in healthy controls, PSC across all ROIs did not show a relationship between arm use and brain activation during force production. In contrast, after stroke, contralesional PM and M1 showed a significant (P ≤ .05) correlation between increasing activation and decreasing paretic arm use, whereas ipsilesional PM showed a significant correlation ( P ≤ .05) between increasing activation and decreasing nonparetic arm use. Conclusions. The results of this pilot study demonstrate a negative relationship between brain activation and actual arm use after stroke. Larger studies using accelerometers that can detect amount and types of movement may offer further insight into brain reorganization and rehabilitation interventions.