Effects of Postlesion Experience on Behavioral Recovery and Neurophysiologic Reorganization after Cortical Injury in Primates

Abstract

Previous studies have shown that after injury to the hand representation in primary motor cortex (M1), size of the spared hand representation decreased dramatically unless the unimpaired hand was restrained and monkeys received daily rehabilitative training using the impaired fingers. The goal of this study was to determine if restriction of the unimpaired hand was sufficient to retain spared hand area after injury or if retention of the spared area required repetitive use of the impaired limb. After infarct to the hand area of M1 in adult squirrel monkeys, the unimpaired hand was restrained by a mesh sleeve over the unimpaired arm. Monkeys did not receive rehabilitative training. Electrophysiologic maps of M1 were derived in anesthetized monkeys before infarct and 1 month after infarct by using intracortical microstimulation. One month after the lesion, the size of the hand representation had decreased. Areal changes were significantly smaller than those in animals in a previous study that had received daily repetitive training after infarct (p < 0.05). Areal changes were not different from those in a group of animals that received neither rehabilitative intervention nor hand restraint after injury. These results suggest that retention of hand area in M1 after a lesion requires repetitive use of the impaired hand.

Thinning, movement, and volume loss of residual cortical tissue occurs after stroke in the adult rat as identified by histological and magnetic resonance imaging analysis

“…Indeed, intracortical microstimulation and fMRI studies have found that electrophysiological maps can reorganize after cortical stroke in order to compensate for the functional loss in the stroke infarct. Better behavioural outcome is also correlated with the extent of cortical map reorganization (Castro-Alamancos and Borrel, 1995;Friel et al, 2000;Frost et al, 2003;Gharbawie et al, 2005;Kleim et al, 2003;. This cortical reorganization may be mediated by two mechanisms.…”

Motor cortical stimulation promotes synaptic plasticity and behavioral improvements following sensorimotor cortex lesions

“…Subtotal motor cortical lesions disrupt the functional integrity of remaining motor cortical areas . However, practice in skilled reaching improves post-lesion reaching deficits and reinstates motor maps Friel et al, 2000;Conner et al, 2005;Ramanathan et al, 2006). Disruption of motor cortical plasticity decreases reaching performance (Kleim et al, 2003a;Luft et al, 2004).…”

Behavioral and neurophysiological effects of delayed training following a small ischemic infarct in primary motor cortex of squirrel monkeys

“…An index of motor performance (finger flexions per food pellet retrieved during post-infarct assessment divided by baseline finger flexions per food pellet retrieved) was derived to control for individual differences in baseline motor skill (Friel et al 2000). A motor performance index of "1" means that pre-and post-infarct performance was equal, an index greater than "1" indicates that the monkey made more finger flexions to retrieve pellets after the infarct, and an index less than "1" indicates that post-infarct performance was improved from pre-infarct performance.…”