Restoration of function after
stroke may be associated with structural remodeling of neuronal connections outside the infarcted area. However, the spatiotemporal profile of poststroke alterations in neuroanatomical connectivity in relation to functional recovery is still largely unknown. We performed in vivo magnetic resonance imaging (MRI)-based neuronal tract tracing with
manganese in combination with immunohistochemical detection of the neuronal tracer
wheat-germ agglutinin horseradish peroxidase (
WGA-HRP), to assess changes in intra- and interhemispheric sensorimotor network connections from 2 to 10 weeks after unilateral
stroke in rats. In addition, functional recovery was measured by repetitive behavioral testing. Four days after tracer injection in perilesional sensorimotor cortex,
manganese enhancement and
WGA-HRP staining were decreased in subcortical areas of the ipsilateral sensorimotor network at 2 weeks after
stroke, which was restored at later time points. At 4 to 10 weeks after
stroke, we detected significantly increased
manganese enhancement in the contralateral hemisphere. Behaviorally, sensorimotor functions were initially disturbed but subsequently recovered and plateaued 17 days after
stroke. This study shows that
manganese-enhanced MRI can provide unique in vivo information on the spatiotemporal pattern of neuroanatomical plasticity after
stroke. Our data suggest that the plateau stage of functional recovery is associated with restoration of ipsilateral sensorimotor pathways and enhanced interhemispheric connectivity.