Use-Dependent Up- and Down-Regulation of Sensorimotor Brain Circuits in Stroke Patients

Abstract

Objective. To examine whether cerebral activity during passive movements decreases with time after stroke, and if reduced activity in the representation for the upper extremity can be reversed with training. Methods. Brain activity was measured by functional magnetic resonance imaging (fMRI) during passive wrist flexion-extension in 7 patients at varying time points after stroke, in a cross-sectional design. Upper limb function was also measured in all patients. Five of the patients took part in a training program and were measured again, behaviorally and with fMRI posttraining. Healthy control individuals of comparable age were also studied. Results. In patients, reduced activity over time after stroke was found for the group in the supplementary motor area (SMA), contralateral primary motor cortex, and prefrontal and parietal association areas along with ipsilateral cerebellum. Activity in most of these areas was also reduced in the patient group as compared to the control group. After a half-hour of daily training for 4 weeks with repetitive passive and active arm movements, cerebral activation increased in the pre-SMA and SMA, ipsilateral primary sensory cortex and intraparietal sulcus, and contralateral cerebellum in parallel with functional improvements of the upper limb. Areas common to both analyses included the SMA, pre-SMA, primary sensory cortex, intraparietal sulcus, and cerebellum. Conclusions. Our findings suggest that a down-regulation of sensorimotor activity occurs progressively over time as a result of inactivity and that training may reverse the reduced brain activity.