Strong seduction: impulsivity and the impact of contextual cues on instrumental behavior in alcohol dependence.

Alcohol-related cues acquire incentive salience through Pavlovian conditioning and then can markedly affect instrumental behavior of alcohol-dependent patients to promote relapse. However, it is unclear whether similar effects occur with alcohol-unrelated cues. We tested 116 early-abstinent alcohol-dependent patients and 91 healthy controls who completed a delay discounting task to assess choice impulsivity, and a Pavlovian-to-instrumental transfer (PIT) paradigm employing both alcohol-unrelated and alcohol-related stimuli. To modify instrumental choice behavior, we tiled the background of the computer screen either with conditioned stimuli (CS) previously generated by pairing abstract pictures with pictures indicating monetary gains or losses, or with pictures displaying alcohol or water beverages. CS paired to money gains and losses affected instrumental choices differently. This PIT effect was significantly more pronounced in patients compared to controls, and the group difference was mainly driven by highly impulsive patients. The PIT effect was particularly strong in trials in which the instrumental stimulus required inhibition of instrumental response behavior and the background CS was associated to monetary gains. Under that condition, patients performed inappropriate approach behavior, contrary to their previously formed behavioral intention. Surprisingly, the effect of alcohol and water pictures as background stimuli resembled that of aversive and appetitive CS, respectively. These findings suggest that positively valenced background CS can provoke dysfunctional instrumental approach behavior in impulsive alcohol-dependent patients. Consequently, in real life they might be easily seduced by environmental cues to engage in actions thwarting their long-term goals. Such behaviors may include, but are not limited to, approaching alcohol.

Gene expression in the suprachiasmatic nuclei and the photoperiodic time integration.

In mammals, the 24 h-rhythmicity of many physiological events is driven by the circadian clock contained in the suprachiasmatic nuclei (SCN). In the SCN, clock gene expressions produce the rhythmicity and control the expression of clock-controlled genes which play a role in the distribution of daily messages. The daily expression of all these genes is modulated by the duration of the light phase (i.e. photoperiod). The aim of this study was first to determine if these daily changes of expression reflect a real integration of a new photoperiod by the circadian clock or reflect only a passive effect of the light. In this way, we performed a time course of the modifications of gene expression after a transfer of Syrian hamsters from long to short photoperiod (LP and SP). Our results demonstrate that the core of the SCN (clock genes) integrates quickly a new photoperiod which entrains a slow adaptation of the clock-controlled gene expressions and induces a differential daily functioning of an SCN-target tissue, the pineal gland. We next asked the question whether SCN are involved in the photorefractory phase observed in Syrian hamsters exposed to SP for 26 weeks. All genes analyzed present a similar daily expression in SP-refractory and in SP with the exception of Clock. Its particular expression in SP-refractory is different than ones observed in SP or in LP. Thus, Clock seems to play a role in the development of the photorefractory phase, or this physiological state may modify the expression of Clock in the SCN. As a conclusion, it appears that the photoperiodic time measurement involves daily modifications of the molecular functioning of the SCN and that SCN also play a role in the measurement of the duration of the time passed in a short photoperiod.