We investigated the detrimental effects of chronic consumption of sweet or sweetened beverages in mice. We report that consumption of beverages containing small amounts of sucrose during several weeks impaired reward systems. This is evidenced by robust changes in the activation pattern of prefrontal brain regions associated with abnormal risk-taking and delayed establishment of decision-making strategy. Supporting these findings, we find that chronic consumption of low doses of artificial sweeteners such as saccharin disrupts brain regions’ activity engaged in decision-making and reward processes. Consequently, this leads to the rapid development of inflexible decisions, particularly in a subset of vulnerable individuals. Our data also reveal that regular consumption, even at low doses, of sweet or sweeteners dramatically alters brain neurochemistry, i.e., dopamine content and turnover, and high cognitive functions, while sparing metabolic regulations. Our findings suggest that it would be relevant to focus on long-term consequences on the brain of sweet or sweetened beverages in humans, especially as they may go metabolically unnoticed.
In this paper, we review recent (published and novel) data showing inter-individual variation in decision-making strategies established by mice in a gambling task (MGT for Mouse Gambling Task). It may look intriguing, at first, that congenic animals develop divergent behaviors. However, using large groups of mice, we show that individualities emerge in the MGT, with about 30% of healthy mice displaying risk-averse choices while about 20-25% of mice make risk-prone choices. These strategies are accompanied by different brain network mobilization and individual levels of regional -prefrontal and striatal- monoamines. We further illustrate three ecological ways that influence drastically cognitive strategies in healthy adult mice: sleep deprivation, sucrose or artificial sweetener exposure, and regular exposure to stimulating environments. Questioning how to unmask individual strategies, what are their neural/neurochemical bases and whether we can shape or reshape them with different environmental manipulations is of great value, first to understand how the brain may build flexible decisions, and second to study behavioral plasticity, in healthy adult, as well as in developing brains. The latter may open new avenues for the identification of vulnerability traits to adverse events, before the emergence of mental pathologies.
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