Healthy parts of the brain can compensate for areas damaged by a stroke. Some of these changes are probably a result of the 'unmasking' of previously unused pathways rather than active rewiring.

Timothy Murphy and his colleagues at the University of British Columbia in Vancouver, Canada, induced small strokes in mice and then monitored their sensory brain activity for up to two hours while stimulating the animals' forepaws. If the stroke occurred in the right hemisphere (controlling the left paw), for example, sensory activity was higher in the left hemisphere when the left or right paw was stimulated, compared with sensory activity prior to the stroke.

Some of the changes occurred as early as 30 minutes after the stroke, too soon to have resulted from circuit rewiring. The authors suggest that stroke unleashes electrical signals that remove the inhibition that normally blocks certain existing pathways.

Proc. Natl Acad. Sci. USA doi:10.1073/pnas.1101914108 (2011)