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Neurosteroids and cognitive performance

Relations between neurosteroid levels within distinct brain regions and cognitive performance, attention and motivation in old rats have been established. This has required the development of a new, very sensitive behavioural test for attention and motivation. These experiments will be pursued to determine whether changes in steroid levels during early life are predictive for later cognitive impairments.

Neurosteroids influence cognition, attention and motivation by modulating the activity of cholinergic neurons in the fore- and hinbrain. Cholinergic neurons of the medial septum, which project to the hippocampus, are involved in the promnesic effects of pregnenolone sulfate. When infused into the medial septum, pregnenolone sulfate increased spatial memory performance and enhanced acetylcholine release within the dorsal hippocampus. Neurosteroids also modulate the activity of cholinergic neurons within the peduncolopontine tegmental nucleus (PTT) of the posterior brain. Morphological alterations of the cholinergic neurons of the PTT have been related to the memory performance of old rats.

These studies have also provided evidence for the first time that mild cognitive deficits observed in old subjects are clearly associated with alterations of the circadian rhytmicity, mainly reflecting fragmentation of sleep parameters.

Reported by

Institut national de la santé e de la recherche médicale
Rue Camille Saint-Saens
33077 Bordeaux
France
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