Effects of valence and arousal on implicit approach/ avoidance tendencies: A fMRI study.

To date, it is still a matter of debate, whether valence or valence and arousal interactively foster implicit approach and avoidance tendencies, and which neural circuitries underlie these effects. To address these questions, we investigated the effects of valence and arousal on implicit approach/avoidance tendencies during fMRI in healthy volunteers (N=46). The implicit approach of positive social scenes was associated with shorter response preparation times and increased activation of the lingual, parahippocampal and fusiform gyri. Valence and arousal did not influence reaction times interactively, but we observed increased activation of prefrontal, motor, temporal, middle cingulate and parietal cortex during the approach of positive highly arousing and negative mildly arousing pictures, and the avoidance of positively mildly arousing and negative highly arousing pictures. These findings confirm the facilitation of implicit approach by positive scenes and advance our understanding regarding the neurobiological correlates of implicit approach-/avoidance biases.

Selective breeding for ethanol-related traits alters circadian phenotype.

Previous studies in mice and rats have shown that selective breeding for high and low ethanol preference results in divergence of circadian phenotype in the selected lines. These results indicate that some alleles influencing ethanol preference also contribute to circadian rhythm regulation. Selective breeding has also been used to produce lines of mice differing in a number of other ethanol-related traits, while studies of phenotypic and genetic correlation indicate that diverse ethanol-related traits are influenced by both shared and unshared genetics. In the present study, we examined several features of circadian activity rhythms in a mouse line selected for binge-like drinking and in mouse lines selected for high and low severity of ethanol withdrawal convulsions. Specifically, Experiment 1 compared High Drinking in the Dark (HDID-1) mice to their genetically heterogeneous progenitor line (HS/Npt), and Experiment 2 compared Withdrawal Seizure-Prone (WSP-2) and Withdrawal Seizure-Resistant (WSR-2) mice. Both line pairs displayed differences in their daily activity patterns under light-dark conditions. In addition, HDID-1 mice showed shorter free-running periods in constant light and less coherent activity rhythms across lighting conditions relative to HS/Npt controls, while WSP-2 mice showed longer free-running periods in constant darkness relative to WSR-2 mice. These results strengthen the evidence for genetic linkages between responsiveness to ethanol and circadian regulation, and extend this evidence to include ethanol-related phenotypes other than preference drinking. However, the present results also indicate that the nature of genetic correlations between and within phenotypic domains is highly complex.

Escalation of intake under intermittent ethanol access in diverse mouse genotypes.

Experimental animals offered continuous 24-hour free choice access to ethanol rarely display voluntary ethanol consumption at levels sufficient to induce intoxication or to engender dependence. One of the simplest ways to increase voluntary ethanol intake is to impose temporal limitations on ethanol availability. Escalation of ethanol intake has been observed in both rats and mice under a variety of different schedules of alternating ethanol access and deprivation. Although such effects have been observed in a variety of rat and mouse genotypes, little is known concerning possible genetic correlations between responses to intermittent ethanol access and other ethanol-related phenotypes. In the present study, we examined the effects of intermittent ethanol access in mouse genotypes characterized by divergent responses to ethanol in other domains, including ethanol preference (C57BL/6J and C3H/HeJ mice), binge-like ethanol drinking (High Drinking in the Dark and HS/Npt mice) and ethanol withdrawal severity (Withdrawal Seizure-Prone and Withdrawal Seizure-Resistant mice). Although intermittent ethanol access resulted in escalated ethanol intake in all tested genotypes, the robustness of the effect varied across genotypes. On the other hand, we saw no evidence that the effects of intermittent access are correlated with either binge-like drinking or withdrawal severity, and only weak evidence for a genetic correlation with baseline ethanol preference. Thus, these different ethanol-related traits appear to depend on largely unique sets of genetic mediators.