Sci. Aging Knowl. Environ., 24 October 2001
Emergency Response Teams Share Strategies: Human and rat brains reorganize similarly after stroke
Key Words: stroke brain functional magnetic resonance imaging plasticity ischemic
Abstract: The human brain behaves like a close-knit community. When natural disaster destroys a few houses, friends across town as well as those next door lend a hand. Similarly, in a stroke-damaged human brain, the uninjured hemisphere tries to help, and later the neighborhood around the hardest hit region recovers enough to pitch in as well. Now, researchers have used functional magnetic resonance imaging (fMRI)--the same technique that uncovered this behavior in human brains--to show that rats' brains reorganize similarly after stroke. Functional magnetic resonance imaging of rat brains after stroke offers a new experimental model for studying how the brain repairs itself and for evaluating therapies.
Dijkhuizen and colleagues induced a stroke in rats by tying off an artery in the right side of the animals' brains; as a result, the left side of the body became temporarily clumsy. They then exploited fMRI to assess how the brains changed as the rats' disabled left limbs recovered. This technique measures blood flow, a reflection of metabolic activity; fMRI generates information about which regions of the brain respond when the subject performs a task. While the animals slept inside the fMRI machine, the researchers gently shocked the rats' left paws to simulate the task of tapping fingers. Three days after the stroke, the brains of sham-operated rats responded on the side opposite the injured limb, but the damaged rats' brains lit up on the unharmed left side. After 14 days, when the animals had regained some control over their left paws, the brightness of the unaffected hemisphere dwindled; the edges of the lesion, however, glowed for the first time.
Functional magnetic resonance imaging provides a noninvasive way to pinpoint sites of physiological change that occur during recovery from a stroke. Because rat and human brains appear to share healing strategies, researchers are optimistic that the new system will provide an experimental model in which to study stroke and its potential treatments. They hope to develop new approaches, because the two therapies currently available are not always effective: Clot-busting drugs work only if used in the first few hours after the mishap, and physical therapy doesn't succeed in all patients. For the approximately 4 million Americans who live with stroke-related disabilities, innovative therapies offer hope of regaining control over their bodies and minds--and toward that end, neighborly rats might now lend a paw.
R. M. Dijkhuizen, J. Ren, J. B. Mandeville, O. Wu, F. M. Ozdag, M. A. Moskowitz, B. R. Rosen, S. P. Finklestein, Functional magnetic resonance imaging of reorganization in rat brain after stroke. Proc. Natl. Acad. Sci. U.S.A. 98, 12766-12771 (2001). [Abstract] [Full Text]
Citation: K. Miller, Emergency Response Teams Share Strategies: Human and rat brains reorganize similarly after stroke. Science's SAGE KE (24 October 2001), http://sageke.sciencemag.org/cgi/content/abstract/sageke;2001/4/nw14
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