Left inferior parietal cortex integrates time and space during collision judgments

Left inferior parietal lobe lesions can cause perturbation of the space-time plans underlying skilled actions. But does the perceptual integration of spatiotemporal information use the same neural substrate or is the role of the left inferior parietal cortex restricted to visuomotor transformations? We use fMRI and a collision judgment paradigm to examine whether the left inferior parietal cortex integrates temporal and spatial variables in situations in which no complex action and no visuomotor transformation is required. We used a perceptual task in which healthy subjects indicated by simple button presses whether two moving objects (of the same or different size) would or would not collide with each other. This task of interest was contrasted with a control task that employed the same stimuli and identical motor responses but in which the size of the two moving objects had to be compared. To assess putative differential eye-movement effects both tasks were performed with and without central fixation. Analysis of the fMRI data (employing a random-effects model and SPM99) showed that collision judgments (relative to size judgments) provoked a significant increase in neural activity in the left inferior parietal cortex (supramarginal gyrus) only. These results show that left inferior parietal cortex is involved in the integration of perceptual spatiotemporal information and thus provide a neural correlate for the use of space-time plans (whose perturbation can lead to apraxia as originally hypothesized by Liepmann). Furthermore, the data suggest that the left supramarginal gyrus combines temporal and spatial variables more widely than previously supposed.     

Astrocytes re-express nestin in deafferented target territories of the adult rat hippocampus.

Up-regulation of the intermediate filament protein, nestin, is a sensitive indicator for the extent of astrocytic activation in regions of CNS close to the point of injury. However, it remains unclear whether activated astrocytes in distant, deafferented CNS territories are also capable of nestin re-expression. Here, we demonstrate that traumatic injury to the dentate gyrus is followed by the rapid but transient expression of nestin in astrocytes located in the stratum lucidum of field CA3. Up-regulation of nestin was first detected at 1 day, was still visible at 14 days, and returned to close to control levels by 28 days post-injury. The present investigation clearly demonstrates the sensitivity of nestin expression as a indicator of astroglial activation in hippocampal target territories undergoing deafferentation-related changes.     

The effects of alcohol on blood pressure and electrolytes

The interaction between alcohol abuse, changes in blood pressure, and electrolyte abnormalities is complex. Some effects of alcohol are seen only with acute ingestion, some during withdrawal, and some only in chronic drinkers. Careful attention to the interactions between the metabolism of various electrolytes can prevent unnecessary morbidity and mortality in alcoholic patients.