Response-independent outcome presentations weakens the instrumental response-outcome association

The present paper explored the fate of previously formed response-outcome associations when the relation between R and O was disrupted by arranging for O to occur independently of R. In each of three experiments response independent outcome delivery selectively reduced the R earning that O. Nevertheless, in Experiments 1 and 2, the R continued to show sensitivity to outcome devaluation, suggesting that the strength of the R-O association was undiminished by this treatment. These experiments used a two-lever, two-outcome design introducing the possibility that devaluation reflected the influence of specific Pavlovian lever-outcome associations. In an attempt to nullify these incidental Pavlovian cues, Experiment 3 used a single bidirectional vertical lever that rats could press left or right for different outcomes. Again, response-independent outcome presentation selectively depressed the performance of the R that delivered the response-independent O. However, in this situation, the response independent O also reduced the sensitivity of R to outcome devaluation; whereas the non-degraded R was sensitive to devaluation, the degraded R was not. We conclude that selective degradation of the instrumental contingency can weaken a specific R-O association while leaving other R-O associations intact. Furthermore, the use of a bidirectional vertical lever in Experiment 3 revealed that instrumental manipulanda, such as levers or chains, produce Pavlovian cues capable of forming incidental associations with the instrumental outcome, obscuring the relative influence of R-O associations after various manipulations.

Attentional capture by signals of food and drink reward persists following outcome devaluation

Attention, the mechanism that prioritises stimuli in the environment for further processing, plays an important role in behavioural choice. In the current study we investigated the automatic orienting of attention to cues that signal reward. Such attentional capture occurs despite negative consequences, but the sensitivity of this counterproductive and reflexive behaviour to shifts in outcome value has not yet been investigated. Thirsty participants completed a visual-search task, in which the colour of a distractor stimulus in the search display signalled whether participants would earn water or potato chips for making a rapid eye movement to a diamond target, but looking at the coloured distractor was punished by omission of the signalled reward. Nevertheless, participants looked at the water-signalling distractor more frequently than the chips-signalling distractor. Half the participants then drank water ad libitum before continuing with the visual-search task. Although the water was now significantly less desirable for half of the participants, there was no difference between groups in the tendency for the water-signalling distractor to capture attention. These findings suggest that once established, attentional bias to signals of food and drink rewards persists, even when those outcomes are no longer valuable. This suggests a ‘habit-like’ attentional mechanism which prioritises reward stimuli in the environment for further action, regardless of whether those stimuli are aligned with current goals, or currently desired.

Is the habit system altered in individuals with obesity? A systematic review

Habit-like eating behavior is repeatedly pointed to as a key cognitive mechanism contributing to the maintenance of overweight and obesity. Here, we conducted a systematic review of the literature to assess the existent behavioural evidence for the Habit Hypothesis for Overeating (HHO) which states that overweight and obesity are the consequence of an imbalance between the habit and goal-directed reward learning systems, leading to overconsumption of food. We found a total of 16 studies implementing a variety of different experimental protocols (i.e., free operant paradigm, slips-of-action test, two-step task, Pavlovian-to-Instrumental (PIT) paradigm, probabilistic learning task) and manipulations that rely on radically different theoretical stances. Studies using satiety-based outcome devaluation procedures as well as probabilistic learning tasks seem to provide preliminary evidence for the HHO. However, findings from different outcome devaluation procedures, sequential decision-making tasks, and PIT paradigms fail to show increased habitual eating behavior propensity in obesity. Taken together, the results of these studies do not support the HHO conclusively. More research along these lines is needed, as if proved, HHO might have a transformative impact on public health, shifting the traditional framework in the treatment and prevention of overweight and obesity.

Basolateral Amygdala to Nucleus Accumbens Communication Differentially Mediates Devaluation Sensitivity of Sign- and Goal-Tracking Rats

Rats rely on communication between the basolateral amygdala (BLA) and nucleus accumbens (NAc) to express lever directed approach in a Pavlovian lever autoshaping (PLA) task that distinguishes sign- and goal-tracking rats. During PLA, sign-tracking rats preferentially approach an insertable lever cue, while goal-tracking rats approach a foodcup where rewards are delivered. While sign-tracking rats inflexibly respond to cues even after the associated reward is devalued, goal-tracking rats flexibly reduce responding to cues during outcome devaluation. Here, we sought to determine whether BLA–NAc communication, which is necessary for sign, but not goal-tracking, drives a rigid appetitive approach of sign-tracking rats that are insensitive to manipulations of outcome value. Using a contralateral chemogenetic inactivation design, we injected contralateral BLA and NAc core with inhibitory DREADD (hm4Di-mCherry) or control (mCherry) constructs. To determine sign- and goal-tracking groups, we trained rats in five PLA sessions in which brief lever insertion predicts food pellet delivery. We sated rats on training pellets (devalued condition) or chow (valued condition) before systemic clozapine injections (0.1 mg/kg) to inactivate BLA and contralateral NAc during two outcome devaluation probe tests, in which we measured lever and foodcup approach. Contralateral BLA–NAc chemogenetic inactivation promoted a flexible lever approach in sign-tracking rats but disrupted the flexible foodcup approach in goal-tracking rats. Consistent with a prior BLA–NAc disconnection lesion study, we find contralateral chemogenetic inactivation of BLA and NAc core reduces lever, but not the foodcup approach in PLA. Together these findings suggest rigid appetitive associative encoding in BLA–NAc of sign-tracking rats hinders the expression of flexible behavior when outcome value changes.

Individual differences in the engagement of habitual control over alcohol seeking predicts the development of compulsive alcohol seeking and drinking

Excessive drinking is an important behavioural characteristic of alcohol addiction, but not the only one. Individuals addicted to alcohol crave alcoholic beverages, spend time seeking alcohol despite negative consequences, and eventually drink to intoxication. With prolonged use, control over alcohol seeking devolves to anterior dorsolateral striatum, dopamine-dependent mechanisms implicated in habit learning and individuals in whom alcohol-seeking relies more on these mechanisms are more likely to persist in seeking alcohol despite the risk of punishment. Here, we tested the hypothesis that the development of habitual alcohol-seeking predicts the development of compulsive seeking and that, once developed, it is associated with compulsive alcohol drinking. Male alcohol-preferring rats were pre-exposed intermittently to a two-bottle choice procedure, and trained on a seeking–taking chained schedule of alcohol reinforcement until some individuals developed punishment-resistant seeking behaviour. The associative basis of their seeking responses was probed with an outcome-devaluation procedure, early or late in training. After seeking behaviour was well established, subjects that had developed greater resistance to outcome-devaluation (were more habitual) were more likely to show punishment-resistant (compulsive) alcohol seeking. These individuals also drank more alcohol, despite quinine adulteration, even though having similar alcohol preference and intake before and during instrumental training. They were also less sensitive to changes in the contingency between seeking responses and alcohol outcome, providing further evidence of recruitment of the habit system. We therefore provide direct behavioural evidence that compulsive alcohol seeking emerges alongside compulsive drinking in individuals that have preferentially engaged the habit system.

An experimental test of the habit-goal framework: Depressive rumination is associated with heightened habitual characteristics of negative thinking but not habit-directed behavior control

Habitual thinking may underpin a heightened disposition to engage in rumination in response to negative mood, a widely held notion that has rarely been directly tested. The purpose of the current study was to investigate whether rumination is associated with habitual attributes and whether it is related to an imbalance in habit relative to goal-directed behavior control. University students (N=115) completed self-report questionnaires, a rumination induction paradigm and an outcome devaluation task that measures habitual vs goal-directed behavior control. Greater habitual characteristics of negative thinking (e.g., automaticity, lack of conscious awareness, control, and intent) were associated with ruminative brooding but not ruminative reflection and predicted more persistent dysphoric mood following rumination induction. Rumination was not, however, consistently associated with an imbalance in habit versus goal-directed behavior control. These findings indicate that depression vulnerability may be in the form of rumination being habitually triggered (without awareness or intent) with deleterious effects on mood. Although habitual, rumination may not be related to an imbalance in habit relative to goal-directed behavior control. These findings provide support for current theoretical accounts of rumination and set important boundary conditions in the search for specific factors that contribute to rumination as a habit.

Basolateral amygdala to nucleus accumbens projections differentially mediate flexibility of sign- and goal-tracking rats

Rats rely on communication between basolateral amygdala (BLA) and nucleus accumbens (NAc) to express lever directed approach in a Pavlovian lever autoshaping (PLA) task that distinguishes sign- and goal-tracking rats. While sign-tracking rats inflexibly respond to cues even after the associated outcome is devalued, goal-tracking rats flexibly suppress conditioned responding during outcome devaluation. Here, we sought to determine whether BLA-NAc communication in sign-trackers drives rigid appetitive approach that is insensitive to manipulations of outcome value. Using a contralateral chemogenetic inactivation design, we injected contralateral BLA and NAc core with inhibitory DREADD (hm4D-mcherry) or control (mcherry) constructs. To determine sign- and goal-tracking groups, we trained rats in five PLA sessions in which brief lever insertion predicts food pellet delivery. We sated rats on training pellets (devalued condition) or chow (valued condition) prior to systemic clozapine injections (0.1 mg/kg) to inactivate BLA and contralateral NAc during two outcome devaluation probe tests, in which we measured lever and foodcup approach. Contralateral BLA-NAc chemogenetic inactivation promoted flexible lever approach in sign-tracking rats, but disrupted flexible food-cup approach in goal-tracking rats. Consistent with a prior BLA-NAc disconnection lesion study, we find contralateral chemogenetic inactivation of BLA and NAc core reduces lever, but not foodcup approach in PLA. Together these findings suggest rigid appetitive associative encoding in BLA-NAc of sign-tracking rats hinders the expression of flexible behavior when outcome value changes.

Alcohol Dependence Differentially Alters Action and Outcome Related Orbitofrontal Cortex Activity

Alcohol dependence results in long-lasting deficits in decision-making and behavioral control. Neurobiological investigations have identified orbitofrontal cortex (OFC) as important for value contributions to decision-making as well as action control, and alcohol dependence induces long-lasting changes to OFC function that persist into protracted withdrawal. However, it is unclear which contributing OFC computations are disrupted in alcohol dependence. Here, we combined a well-validated mouse model of alcohol dependence with in vivo extracellular recordings during an instrumental task in which lever press duration serves as the contingency, and lever pressing is sensitive to outcome devaluation. We found prior alcohol dependence did not impair use of duration contingency control but did reduce sensitivity to outcome devaluation. Further, alcohol dependence increased OFC activity associated with lever-pressing but decreased OFC activity during outcome-related epochs. Hence, alcohol dependence induces a long-lasting disruption to OFC function such that activity associated with actions is enhanced, but OFC activity in relation to outcomes is diminished. This has important implications for hypotheses regarding compulsive and habitual phenotypes observed in addiction.