Neurophysiological and behavioural adaptations to a bilateral training intervention in individuals following stroke

Objective: To examine the neurophysiological and behavioural adaptations to a bilateral training protocol in individuals with hemiparesis due to stroke. Design: Subjects performed daily practice sessions of three specific upper limb tasks over a four-week period. Performance of the tasks was recorded on video for later analysis over the duration of the study. For the first week of the training period the tasks were practised with the impaired upper limb. Only then, with a random start day between 8 and 13, the tasks were practised using a bilateral training protocol. Functional assessments of the affected upper limb and neurophysiological investigations of contra- and ipsilateral pathways from the affected and nonaffected cortical hemispheres were completed prior to the start of the intervention, at the end of the unimanual practice period, and at the conclusion of the bimanual practice period. Subjects: Six individuals between one month and four years post stroke. Interventions: Unimanual and bimanual training protocols. Main measures: Task performance with the affected limb only; motor impairment of the affected upper limb; ipsi- and contralateral corticospinal pathway excitability. Results: Baseline task performance varied markedly between subjects. Most individuals demonstrated little, if any, additional beneficial effect of bimanual practice on task performance. Results of neurophysiological investigations were inconsistent between subjects. Conclusions: Short-term bilateral training following unilateral training may have limited effectiveness in enhancing upper limb motor performance in acute and chronic individuals poststroke. The neural mechanisms associated with bilateral activation therapies remain uncertain.