Location response to a startling noise depends on the preferred grooming site in mice

Further evidence that mice learn a win-shift but not a win-stay contingency under water-escape motivation

Previous research (C. Locurto, C. Emidy, & S. Hannan, 2002) indicated that mice quickly learned a water-escape task under a win-shift contingency but did not exceed chance-level performance under a win-stay contingency. We examined the robustness of this conclusion in two experiments by varying procedural and temporal aspects of that earlier experiment. Results of both experiments indicated that the preference for win-shift learning in mice under water-escape motivation could not be attributed to procedural or design features of that earlier study and were independent of the influence of intertrial interval, normally a variable that produces strong effects on learning. In neither experiment did subjects exposed to a win-stay contingency perform at above-chance levels.

Contrasting grooming phenotypes in three mouse strains markedly different in anxiety and activity (129S1, BALB/c and NMRI)

129S1/SvImJ (129S1), NMRI and BALB/c mice are widely used in behavioural research, demonstrating marked strain differences in their behavioural phenotypes. Grooming is a complex and essential ritual in the rodent behavioural repertoire with a general cephalocaudal progression (forepaws-nose-face-body-legs-tail and genitals). Various stressors as well as genetic manipulations have been reported to alter mouse grooming and its patterning, underlying the importance of analysis of grooming behaviours. Although strain differences between these mice have been assessed in many studies, no comparative analyses of their grooming have been performed. Here we show strain differences in spontaneous (novelty-induced) grooming between 129S1, NMRI and BALB/c mice. Overall, 129S1 mice demonstrated lower grooming activity and impaired microstructure (more interrupted bouts and incorrect transitions contrary to the cephalocaudal rule), accompanied by lower vertical exploration. In contrast, BALB/c and NMRI mice showed high vertical activity and unimpaired grooming microstructure, also exhibiting different grooming levels (BALB/c>NMRI). Our study suggests that contrasting grooming phenotypes in these mice may not be due to the strain differences in their sensory abilities, general activity levels, brain anatomy or aggressiveness, but rather reflect a complex interplay between anxiety, motor and displacement activity in these strains (hypoactive anxious phenotype in 129S1 mice, active anxious phenotype in BALB/c and non-anxious high displacement phenotype in NMRI mice). We suggest that ethological analysis of mouse grooming, such as that reported here, may be a useful tool in neurobehavioural research.

Brain weights correlate with behavioral parameters in individual inbred mice housed in a common and enriched environment

Fifty 8-week-old Balb/c mice were individually identified and housed together in a large and enriched environment for 5 months. Maze and open field exploration, response to an aversive noise, swimming, and induced grooming tests were applied to each mouse in an initial search for possible relationships between brain morphology and spontaneous behavior in isogenic individuals living in a complex social and physical environment. The tasks generated 39 quantitative behavioral indices which include locomotion, rearing, still, and grooming bout frequencies, latencies, total, and mean bout durations. At the end of the tests, the 7-month-old mice were sacrificed and the fresh weights of their whole brain, cerebellum, brain stem, diencephalon, telencephalon, and prosencephalon were rapidly obtained. Behavioral data have wide variations and do not adjust to normal population distributions. Means of the same parameter differ between tests. A Spearman correlation matrix of all data yielded many significant correlations between indices of the same task which can be interpreted in terms of time budget and sequence probability. Significant correlations between indices of different tests suggest diverse emotionalities, exploratory strategies, and motor skills. The correlations between body and brain weights and among separate brain regions were not significant. There were several low but significant correlations between brain weights and behavioral indices. Such correlations, the resulting factors, and significant behavioral differences between mice with large and small brains suggest that mice displaying low motor activity in novel environments have larger brains and forebrain/hindbrain ratios than mice with high activity, and that animals with high scores of some specific behaviors have larger brain areas physiologically related to such behaviors.(ABSTRACT TRUNCATED AT 250 WORDS)