Chronic exposure to mild unpredictable stressors (CMS) has previously been found to reduce the consumption of palatable, sweet solutions in rats. In the present study, the utility of this procedure was assessed in mice. Male AP mice subjected to CMS showed reduced consumption of a 2% or 4% sucrose solution. This effect was reversed by chronic (3 weeks) treatment with the tricyclic antidepressant imipramine (20 mg/kg per day). These results extend previous reports of a generalized decrease in sensitivity to reward (anhedonia) in rats caused by CMS and the efficacy of antidepressant treatment in this paradigm. Chronic unpredictable mild stress in mice appears to provide a realistic animal model of depression.
This report includes the first sibling study of mouse behavior, and presents evidence for a heritable general cognitive ability (g) factor influencing cognitive batteries. Data from a population of male and female outbred mice (n = 84), and a replication study of male sibling pairs (n = 167) are reported. Arenas employed were the T-maze, the Morris water maze, the puzzle box, the Hebb-Williams maze, object exploration, a water plus-maze, and a second food-puzzle arena. The results show a factor structure consistent with the presence of g in mice. Employing one score per arena, this factor accounts for 41% of the variance in the first study (or 36% after sex regression) and 23% in the second, where this factor also showed sibling correlations of 0.17-0.21, which translates into an upper-limit heritability estimate of around 40%. Reliabilities of many tasks are low and consequently set an even lower ceiling for inter-arena or sibling correlations. Nevertheless, the factor structure is seen to remain fairly robust across permutations of the battery composition and the current findings fit well with other recent studies.
The heterogeneous stock (HS) is a genetically outbred line of mice established more than 30 years ago from an 8-way cross of C57BL/6, BALB/c, RIII, AKR, DBA/2, I, A/J and C3H inbred mouse strains. The present study compared the performance of 40 HS mice across a battery of diverse cognitive tasks under a variety of motivations. Indices of emotionality were also included in order to assess their influence on performance. All measures of ability loaded positively on an unrotated first principal component that accounted for 31% of the variance, suggesting the presence of a common factor of general cognitive ability (g) underlying all tasks. A first factor derived from anxiety indices correlated nonsignificantly with all cognitive tasks and nonsignificantly with this g factor, supporting the hypothesis that the factor is cognitive rather than temperamental in nature. The factor was also robust in relation to outliers and sex differences, accounting for 28% of the variance after removal of outlier individuals and also after correcting for variance owing to sex differences. A general cognitive ability (g) appears to underlie the performance of HS mice on a battery tapping diverse cognitive demands.
In adolescents, immediate visual memory (IVM) is more sensitive than working memory to impairment by alcohol, and women are more vulnerable to the neurotoxic effects of alcohol than men, because the cognitive tolerance effect of alcohol on IVM develops in binge drinking (BD) women but not in BD men.
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