Remodeling the brain with behavioral experience after stroke

Abstract

Background and purpose: Behavioral experience can drive brain plasticity, but we lack sufficient knowledge to optimize its therapeutic use after stroke.

Methods: We outline recent findings from rodent models of cortical stroke of how experiences interact with postinjury events to influence synaptic connectivity and functional outcome. We focus on upper extremity function.

Results: After unilateral cortical infarcts, behavioral experiences shape neuronal structure and activity in both hemispheres. Experiences that matter include interventions such as skill training and constraint-like therapy as well as unguided behaviors such as learned nonuse and behavioral compensation. Lateralized behaviors have bihemispheric influences. Ischemic injury can alter the sensitivity of remaining neocortical neurons to behavioral change and this can have positive and negative functional effects.

Conclusions: Because experience is ongoing in stroke survivors, a better understanding of its interaction with brain reorganization is needed so that it can be manipulated to improve function and prevent its worsening.

Figure 1. Behavioral interventions change the course of neural reorganization after sensorimotor cortical infarcts

Rats use their forepaws in dexterous ways for food handling (A) and reaching behaviors (B), making them suitable for modeling aspects of upper extremity impairments., After unilateral cortical infarcts, rats have enduring contralesional impairments in sensitive measures of these behaviors, and they develop a reliance on the "unaffected" ipsilesional forepaw. Skill acquisition with the unaffected forelimb interacts with injury-induced cellular changes to drive a robust plasticity of dendrites and synapses (*) in the contralesional motor cortex (layer V, C)., However, it also reduces neuronal activation in peri-infarct cortex and worsens the efficacy of later motor rehabilitative training focused on the impaired forelimb., Cortical stimulation (CS) combined with motor training of the impaired limb improves its efficacy and increases the density of dendrites and synapses in peri-infarct motor cortex (D).,, MI, primary motor, SI, primary somatosensory cortex.