Brain repair after stroke--a novel neurological model

Abstract

Following stroke, patients are commonly left with debilitating motor and speech impairments. This article reviews the state of the art in neurological repair for stroke and proposes a new model for the future. We suggest that stroke treatment--from the time of the ictus itself to living with the consequences--must be fundamentally neurological, from limiting the extent of injury at the outset, to repairing the consequent damage. Our model links brain and behaviour by targeting brain circuits, and we illustrate the model though action observation treatment, which aims to enhance brain network connectivity. The model is based on the assumptions that the mechanisms of neural repair inherently involve cellular and circuit plasticity, that brain plasticity is a synaptic phenomenon that is largely stimulus-dependent, and that brain repair required both physical and behavioural interventions that are tailored to reorganize specific brain circuits. We review current approaches to brain repair after stroke and present our new model, and discuss the biological foundations, rationales, and data to support our novel approach to upper-extremity and language rehabilitation. We believe that by enhancing plasticity at the level of brain network interactions, this neurological model for brain repair could ultimately lead to a cure for stroke.

Figure 1

Possible mirror neuron network for syllable observation and imitation. A model of shared brain networks activated by observation and execution of speech, as determined by functional MRI in humans. Solid lines show connections that are common to observation and imitation, whereas dashed lines show connections that are more important in imitation than in observation. Pink rectangles represent core nodes in the putative ‘mirror neuron’ network. These networks suggest that a flow of information during imitation—starting at the posterior superior temporal cortex and ending in the motor cortex—enhances input to the motor cortex in the service of speech execution.

Figure 2

Visual stimuli for action observation treatment. During action observation treatment, patients watch video sequences containing daily life hand and arm actions (top panels) or leg and foot actions (bottom panels) for 6 min, and then perform the action for 6 min, using the same movement and objects shown in the video clip. On each day of treatment, a ‘unit’ of three limb movements of increasing complexity is presented. In each video, the presented action is shown from three perspectives. A complete session consists of three or four such videos. Patients typically undergo 20 rehabilitation sessions over 20 consecutive weekdays. During both observation and execution, patients are instructed to focus on the goal of the action rather than on the movement per se.