The interaction between training and plasticity in the poststroke brain

Abstract

Purpose of review Recovery after stroke can occur either via reductions in impairment or through compensation. Studies in humans and non-human animal models show that most recovery from impairment occurs in the first 1 to 3 months after stroke as a result of both spontaneous reorganization and increased responsiveness to enriched environments and training. Improvement from impairment is attributable to a short-lived sensitive period of post-ischemic plasticity defined by unique genetic, molecular, physiological and structural events. In contrast, compensation can occur at any time after stroke. Here we address both the biology of the brain's post-ischemic sensitive period and the difficult question of what kind of training (task-specific vs. a stimulating environment for self-initiated exploration of various natural behaviors) best exploits this period. Recent findings Data suggest that three important variables determine the degree of motor recovery from impairment: (i) the timing, intensity, and approach to training with respect to stroke onset, (ii) the unique post-ischemic plasticity milieu, and (iii) the extent of cortical reorganization. Summary Future work will need to further characterize the unique interaction between types of training and post-ischemic plasticity, and find ways to augment and prolong the sensitive period using pharmacological agents or non-invasive brain stimulation.

Moving Rehabilitation Research Forward: Developing Consensus Statements for Rehabilitation and Recovery Research

“…One of the most important findings to emerge from decades of work in rodents was the identification of a period of spontaneous biological recovery during which the effect of training is heightened (15). Investigating the mechanisms involved in humans would reveal exciting therapeutic targets.…”

Moving rehabilitation research forward: Developing consensus statements for rehabilitation and recovery research

“…One of the most important findings to emerge from decades of work in rodents was the identification of a period of spontaneous biological recovery during which the effect of training is heightened. 15 Investigating the mechanisms involved in humans would reveal exciting therapeutic targets. A different type of problem, specific to human studies, is heterogeneity in the residual structural and functional post-stroke brain architecture and the impact this has on potential interventions.…”

SMART Arm Training With Outcome-Triggered Electrical Stimulation in Subacute Stroke Survivors With Severe Arm Disability: A Randomized Controlled Trial

“…In this current study, 20 hours of training over four weeks for stroke survivors with severe paresis was almost certainly too little practice, over too short a time period, to shift the recovery profile, above the spontaneous recovery profile 13,[40][41][42] . There is increasing evidence that the greatest opportunity for motor recovery after stroke occurs during the unique 'sensitive period', in which time-enhanced spontaneous as well as intervention-mediated plasticity exists 13 .…”

“…There is increasing evidence that the greatest opportunity for motor recovery after stroke occurs during the unique 'sensitive period', in which time-enhanced spontaneous as well as intervention-mediated plasticity exists 13 . As the 'sensitive period' is presumed to begin within two weeks after stroke and to continue for approximately three months 40,42,43 greater spontaneous recovery may have occurred for participants who were earlier post stroke.…”

“…Accordingly, changes in muscle activation patterns 11 and increases in corticospinal reactivity 12 , that have accompanied increases in capacity to perform reaching movements, have exhibited some of the characteristics of 'true' recovery 13 . The feasibility of SMART Arm training in the home with minimal supervision has also been demonstrated in a single case study 14 .…”