Enriched Rehabilitation Reduces Abnormal Motor Synergies and Enhances Motor Plasticity Following Severe Stroke in Rats.

Background: Stroke results in loss of upper motor neuron control over voluntary movements and emergence of abnormal synergies. Presently, it is unclear to what extent poststroke recovery reflects true recovery (restitution), compensation, or some combination of these processes. Here, we investigated this question using behavioral and kinematic analyses of skilled reaching in rats subjected to severe stroke that affected both the forelimb motor cortex and dorsolateral striatum.

Poststroke Impairment and Recovery Are Predicted by Task-Specific Regionalization of Injury.

Lesion size and location affect the magnitude of impairment and recovery following stroke, but the precise relationship between these variables and functional outcome is unknown. Herein, we systematically varied the size of strokes in motor cortex and surrounding regions to assess effects on impairment and recovery of function. Female Sprague Dawley rats ( = 64) were evaluated for skilled reaching, spontaneous limb use, and limb placement over a 7 week period after stroke.

Interhemispheric modulations of motor outputs by the rostral and caudal forelimb areas in rats.

In rats, forelimb movements are evoked from two cortical regions, the caudal and rostral forelimb areas (CFA and RFA, respectively). These areas are densely interconnected and RFA induces complex and powerful modulations of CFA outputs. CFA and RFA also have interhemispheric connections, and these areas from both hemispheres send projections to common targets along the motor axis, providing multiple potential sites of interactions for movement production.

The Effect of Lesion Size on the Organization of the Ipsilesional and Contralesional Motor Cortex.

Recovery of hand function following lesions in the primary motor cortex (M1) is associated with a reorganization of premotor areas in the ipsilesional hemisphere, and this reorganization depends on the size of the lesion. It is not clear how lesion size affects motor representations in the contralesional hemisphere and how the effects in the 2 hemispheres compare. Our goal was to study how lesion size affects motor representations in the ipsilesional and contralesional hemispheres.

Inhibition of the contralesional hemisphere after stroke: reviewing a few of the building blocks with a focus on animal models.

The last decade of neuroscience research has revealed that the adult brain can undergo substantial reorganization following injury. Plasticity after stroke has traditionally been perceived as adaptive and supporting recovery, but recent studies have suggested that some plasticity may also be detrimental. In particular, increased activity in the unaffected (contralesional) hemisphere has been proposed to contribute to motor deficits of the paretic hand in some patients.

Acute inactivation of the contralesional hemisphere for longer durations improves recovery after cortical injury.

A rapidly growing number of studies using inhibition of the contralesional hemisphere after stroke are reporting improvement in motor performance of the paretic hand. These studies have used different treatment onset time, duration and non-invasive methods of inhibition. Whereas these results are encouraging, several questions regarding the mechanisms of inhibition and the most effective treatment parameters are currently unanswered.