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Age-related brain injuries including stroke, are a major cause of physical and mental disabilities. Therefore studying the basic mechanism underlying functional recovery after brain stroke in middle aged subjected it is of considerable clinical interest. Data from our lab and elsewhere indicate that, behaviorally, middle aged rats were more severely impaired by stroke than were young rats, and they also showed diminished functional recovery. Infarct volume did not differ significantly in young and middle aged animals, but critical differences were apparent in the cytological response to stroke, most notably an age-related acceleration of the establishment of the glial scar. The early infarct in older rats is associated with a premature accumulation of BrdU-positive microglia and astrocytes, persistence of activated oligodendrocytes, a high incidence of neuronal degeneration, and accelerated apoptosis. In middle aged rats, neuroepithelial-positive cells were rapidly incorporated into the glial scar, but these neuroepithelial-like cells did not make a significant contribution to neurogenesis in the infarcted cortex in young or middle aged animals. Stroke is accompanied by a strong inflammatory reaction in the brain. We hypothesized that a mild systemic inflammatory reaction as caused by periodontal disease prior to stroke onset, may exert a neuroprotective effect in a rat model of focal ischemia. To test this hypothesis, marginal periodontitis was induced in BB/LL Wistar rats for 3 weeks. Two weeks after periodontitis initiation, focal cerebral ischemia was produced by reversible occlusion of the right middle cerebral artery. After a survival time of 7 days after ischemia, rat brains were analyzed. In addition, markers of systemic inflammation were determined in a different group of laboratory animals at 14 days after the onset of periodontitis. We found that rats with a mild systemic inflammation had a significantly reduced infarct volume and a significant reduction in the number of brain macrophages in the infarcted area. Conclusions: The available evidence indicates that the middle aged brain has the capability to mount a cytoproliferative response to injury, but the timing of the cellular and genetic response to cerebral insult is deregulated in middle aged animals, thereby further compromising functional recovery. In addition we found that that mild systemic inflammation elicited prior to stroke onset may have a neuroprotective effect in rats by reducing the infarct volume and tissue destruction by brain macrophages.
Sensorimotor representations of swallowing in pre- and postcentral gyri of both cerebral hemispheres are interconnected by callosal tracts. We were interested in (1) the callosal location of fibers interconnecting the precentral gyri (with the primary motor cortex; M1) and the postcentral gyri (with the primary somatosensory cortex; S1) relevant for swallowing, and (2) the importance of their integrity given the challenges of swallowing compliance after recovery of dysphagia following stroke. We investigated 17 patients who had almost recovered from dysphagia in the chronic stage following stroke and age-matched and gender-matched healthy controls. We assessed their swallowing compliance, investigating swallowing of a predefined bolus in one swallowing movement in response to a ‘go’ signal when in a lying position. A somatotopic representation of swallowing was mapped for the pre- and postcentral gyrus, and callosal tract location between these regions was compared to results for healthy participants. We applied multi-directional diffusion-weighted imaging of the brain in patients and matched controls to calculate fractional anisotropy (FA) as a tract integrity marker for M1/S1 callosal fibers. Firstly, interconnecting callosal tract maps were well spatially separated for M1 and S1, but were overlapped for somatotopic differentiation within M1 and S1 in healthy participants’ data (HCP: head/face representation; in house dataset: fMRI-swallowing representation in healthy volunteers). Secondly, the FA for both callosal tracts, connecting M1 and S1 swallowing representations, were decreased for patients when compared to healthy volunteers. Thirdly, integrity of callosal fibers interconnecting S1 swallowing representation sites was associated with effective swallowing compliance. We conclude that somatosensory interaction between hemispheres is important for effective swallowing in the case of a demanding task undertaken by stroke survivors with good swallowing outcome from dysphagia.