Reorganization of brain function during force production after stroke: a systematic review of the literature

Abstract

Background and purpose: Damage to motor areas of the brain caused by stroke can produce devastating motor deficits, including aberrant control of force. Reorganization of brain function is a fundamental mechanism involved in recovery of motor control after stroke, and recent advances in neuroimaging have enabled study of this reorganization. This review focuses on neuroimaging studies that have examined reorganization of brain function during force production and force modulation after stroke.

Methods: The type and extent of reorganization after stroke were characterized by three factors: severity of injury, time after stroke, and impact of therapeutic interventions on brain activation during force production. Twenty-six studies meeting the inclusion criteria could be identified in MEDLINE (1980-2007).

Results: Relevant characteristics of studies (lesion location, chronicity of stroke, and motor task) and mapping techniques varied. During force production, increased activation in secondary motor areas occurred in persons with more severe strokes. Reduced recruitment of secondary motor areas during force production was found as a function of increased time since stroke. During force modulation, increased activation in motor areas occurred with greater force generation. Persons with more severe stroke showed greater activation with increasing force compared with persons with less severe stroke. Alteration of brain activation during and after rehabilitative interventions was identified in some studies.

Discussion and conclusion: This systematic review establishes that reorganization of brain function during force production and force modulation can occur after stroke. These findings imply that therapeutic strategies may target brain reorganization to improve force control and functional recovery after stroke.

Figure 1. Medial and lateral views of the non-affected hemisphere (A) and affected hemisphere (B) of the brain depicting areas having increased activation with increased severity OR decreased outcome in at least two or more studies

A. Non-affected hemisphere shows increased activation in M1, SMA, PM, cingulate sulcus, intraparietal sulcus, cerebellum. B. Affected hemisphere shows increased activation in M1, SMA, PM, cingulate sulcus and intraparietal sulcus. Note: M1 = primary motor cortex, SMA = supplementary motor area, PM = premotor cortex.