Plasticity and response to action observation: a longitudinal FMRI study of potential mirror neurons in patients with subacute stroke

Abstract

Background: Action observation has been suggested as a possible gateway to retraining arm motor function post stroke. However, it is unclear if the neuronal response to action observation is affected by stroke and if it changes during the course of recovery.

Objective: To examine longitudinal changes in neuronal activity in a group of patients with subacute stroke when observing and executing a bimanual movement task.

Methods: Eighteen patients were examined twice using 3-T functional magnetic resonance imaging; 1 to 2 weeks and 3 months post stroke symptom onset. Eighteen control participants were examined once. Image time series were analyzed (SPM8) and correlated with clinical motor function scores.

Results: During action observation and execution, an overlap of neuronal activation was observed in the superior and inferior parietal lobe, precentral gyrus, insula, and inferior temporal gyrus in both control participants and patients (P < .05; false discovery rate corrected). The neuronal response in the observation task increased from 1 to 2 weeks to 3 months after stroke. Most activated clusters were observed in the inferior temporal gyrus, the thalamus and movement-related areas, such as the premotor, supplementary and motor cortex (BA4, BA6). Increased activation of cerebellum and premotor area correlated with improved arm motor function. Most patients had regained full movement ability.

Conclusions: Plastic changes in neurons responding to action observation and action execution occurred in accordance with clinical recovery. The involvement of motor areas when observing actions early and later after stroke may constitute a possible access to the motor system.

Keywords: action observation; arm motor function; fMRI; mirror neurons; rehabilitation; stroke.