Functional MRI of Reorganization in Rat Brain after Stroke

Rick Dijkhuizen

MGH-NMR Center
Department of Radiology
Massachusetts General Hospital, Harvard Medical School

Stroke regularly causes acute loss of sensorimotor function. Although often incomplete, some degree of functional recovery is common at later stages, which has been associated with brain plasticity. Our goal was to correlate recovery of sensorimotor function with changes in brain activation patterns in relation to the cerebral pathophysiological status, as measured with functional MRI techniques, in a rat stroke model. Our results indicate that early after stroke, when sensorimotor deficits are severe, activation-induced responses are absent in the damaged hemisphere upon stimulation of the impaired forelimb. However, significant responses are detected in the intact hemisphere, which is ipsilateral to the stimulated forelimb. At chronic stages, when function of the impaired limb has largely recovered, signs of activation are found in the infarction borderzone and in the intact hemisphere. These findings of extension of forelimb representational areas into adjacent cortical areas, and activation responses in the intact hemisphere after unilateral stroke in rat brain, are consistent with the reorganization observed in human brain recovering from ischemic injury. Our data also suggest that the degree of dysfunction of the impaired limb is related to loss of brain activation in the contralateral sensorimotor cortex. Restoration of sensorimotor function may be associated with recruitment of peri- and contralesional functional fields in the brain.

The lecture will take place:

in the Lecture Hall, Room 401, 44 Cummington St.
on Tuesday, October 25, 2000
at 3:00 pm