Alzheimer's disease (AD), the most common dementing disorder of aging, is a progressive neurodegenerative disease of unknown etiology. Two of the common clinical features of AD are progressive cognitive and functional impairment, and disturbed sleep/wake patterns. We examined sleep/wake patterns and cognitive and functional status measures in a large sample of AD subjects ranging from mild to moderate-severe in impairment. All subjects survived at least 2 years after initial diagnosis. Regression analyses revealed that sleep/wake variables were highly correlated with and explained significant variance in cognitive and functional measures. More wakefulness during the night and longer REM latencies were associated with impaired cognition and function while more REM and slow-wave sleep were associated with preserved cognition and function. These results indicate that with advancing severity of the disease, sleep/wake patterns are disrupted in parallel with the disturbances in cognition and function that are the hallmarks of AD. Further, they suggest that the neural substrates underlying each process degenerate at somewhat comparable rates.
Many mammals eat salt irrespective of need. This behavior, called salt preference or appetite, is studied primarily in adults. Little is known about its ontogeny. In these experiments, 3-18-day-old rat pups were offered saline, quinine, or ammonium chloride solutions by infusion through an anterior oral catheter, and intake was measured. At 6-18 days, pups showed the inverted U-shaped preference-aversion curve for NaCl that is characteristic of adult rats. Thus, rats express a preference for salt at a very early age. However, the curves were broader than the typical adult curve and were shifted along the concentration gradient in an age-related fashion. Consumption of quinine and ammonium chloride showed similar age-related changes. These changes may reflect the postnatal timing of the development of the rat gustatory system.
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