Behavioral specifications of reward-associated long-term memory enhancement in humans

Recent functional imaging studies link reward-related activation of the midbrain substantia nigra-ventral tegmental area (SN/VTA), the site of origin of ascending dopaminergic projections, with improved long-term episodic memory. Here, we investigated in two behavioral experiments how (1) the contingency between item properties and reward, (2) the magnitude of reward, (3) the uncertainty of outcomes, and (4) the contextual availability of reward affect long-term memory. We show that episodic memory is enhanced only when rewards are specifically predicted by the semantic identity of the stimuli and changes nonlinearly with increasing reward magnitude. These effects are specific to reward and do not occur in relation to outcome uncertainty alone. These behavioral specifications are relevant for the functional interpretation of how reward-related activation of the SN/VTA, and more generally dopaminergic neuromodulation, contribute to long-term memory.     

Anticipatory and consummatory components of the experience of pleasure: A scale development study

The Temporal Experience of Pleasure Scale (TEPS) was designed to measure individual trait dispositions in both anticipatory and consummatory experiences of pleasure. From an initial pool of theory-based items, we developed a 10-item anticipatory pleasure scale and an 8-item consummatory pleasure scale using several large college-age samples; the two scales were both internally consistent and temporally stable. As expected, these two scales were moderately, positively correlated with each other. Examination of convergent and discriminant validity indicated that the two scales measured distinct and specific constructs. In particular the anticipatory scale was related to reward responsiveness and imagery, while consummatory pleasure was related to openness to different experiences, and appreciation of positive stimuli. Potential applications of the TEPS, particularly in psychopathology research, are discussed.     

Ventral tegmental area and substantia nigra neural correlates of spatial learning

The ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) may provide modulatory signals that, respectively, influence hippocampal (HPC)- and striatal-dependent memory. Electrophysiological studies investigating neural correlates of learning and memory of dopamine (DA) neurons during classical conditioning tasks have found DA neural activity in VTA and SNc to be tightly coupled with reinforcement expectations. Also, VTA integrity and DA in HPC have been found to regulate the encoding of HPC-dependent memories. Therefore, to determine the nature of the neural code HPC may receive from midbrain DA regions, the present study investigated VTA and SNc neural activity as navigating rats engaged in new spatial learning and experienced changes in expected goal locations. VTA and SNc cells were differentially engaged during training to a series of three novel goal locations. During task acquisition, the peak firing rates of VTA neurons decreased at the time of reward and shifted to time points before reward retrieval, whereas the peak firing rates of SNc neurons remained elevated at the time of reward during training to all three goal locations. Both VTA and SNc egocentric coding was strongest during training to the first goal location, which coincided with the time subjects learned the behavioral rules specific to the task. These data imply that VTA and SNc play complementary yet distinct roles in spatial learning to optimize adaptive behavior.     

Neurophysiological differences in reward processing in anhedonics

Anhedonia is characterized by a reduced capacity to experience pleasure in response to rewarding stimuli and has been considered a possible candidate endophenotype in depression and schizophrenia. However, it is still not well understood whether these reward deficits are confined to anticipatory and/or to consummatory experiences of pleasure. In the present study, we recorded electrophysiological responses (event-related brain potentials [ERPs] and oscillatory activity) to monetary gains and losses in extreme groups of anhedonic and nonanhedonic participants. The anhedonic participants showed reduced motivation to incur risky decisions, especially after monetary rewards. These sequential behavioral effects were correlated with an increased sensitivity to punishment, which psychometrically characterized the anhedonic group. In contrast, both electrophysiological measures associated with the impacts of monetary losses and gains—the feedback-related negativity (FRN) and the beta–gamma oscillatory component—clearly revealed preserved consummatory responses in anhedonic participants. However, anhedonics showed a drastic increase in frontal medial theta power after receiving the maximum monetary gain. This increase in theta oscillatory activity could be associated with an increase in conflict and cognitive control for unexpected large positive rewards, thus indexing the violation of default negative expectations built up across the task in anhedonic participants. Thus, the present results showed that participants with elevated scores on Chapman’s Physical Anhedonia Scale were more sensitive to possible punishments, showed deficits in the correct integration of response outcomes in their actions, and evidenced deficits in sustaining positive expectations of future rewards. This overall pattern suggests an effect of anhedonia in the motivational aspects of approach behavior rather than in consummatory processes.     

Distinguishing between learning and motivation in behavioral tests of the reinforcement sensitivity theory of personality

According to Gray's (1973) Reinforcement Sensitivity Theory (RST), a Behavioral Inhibition System (BIS) and a Behavioral Activation System (BAS) mediate effects of goal conflict and reward on behavior. BIS functioning has been linked with individual differences in trait anxiety and BAS functioning with individual differences in trait impulsivity. In this article, it is argued that behavioral outputs of the BIS and BAS can be distinguished in terms of learning and motivation processes and that these can be operationalized using the Signal Detection Theory measures of response-sensitivity and response-bias. In Experiment 1, two measures of BIS-reactivity predicted increased response-sensitivity under goal conflict, whereas one measure of BAS-reactivity predicted increased response-sensitivity under reward. In Experiment 2, two measures of BIS-reactivity predicted response-bias under goal conflict, whereas a measure of BAS-reactivity predicted motivation response-bias under reward. In both experiments, impulsivity measures did not predict criteria for BAS-reactivity as traditionally predicted by RST.     

The roles of aggressive and affiliative behaviors in resource control: A behavioral ecological perspective

Extant literature in developmental psychology has documented the co-occurrence of aggressive and affiliative behaviors with various measures of social dominance. While these findings have been taken as evidence for the functional value of aggression, they have not been integrated into a more general theoretical frame accounting for contextual variation. In this paper the literature on aggression, agonism, affiliation, and social dominance is reviewed in light of behavioral ecological theory suggesting that different forms of competition (scramble and contest) determine, respectively, the use of affiliative and aggressive strategies. Results generally support the hypotheses advanced by this theory. In order to further integrate these findings suggestions for the study sequences of behavior, where reconciliations follow aggression, are made.     

Is who you are who you're talking to? Interpersonal style and complementarity in mixed-sex interactions

To investigate interpersonal theory, the authors examined the social behavior of 112 previously unacquainted male-female pairs collaborating on a joint task. Structural equation modeling analyses provided clear evidence of complementarity: In addition to trait affiliation and dominance both predicting situational behavior, each interaction partner's behavior influenced the other's in accordance with the theory, eliciting similar levels of affiliation and opposite levels of dominance. There were also clear biases related to participants' interpersonal traits: When behavior, as indexed by observers, was held constant, more trait affiliative participants tended to view themselves and their partner as warmer during the interaction; likewise, more trait dominant participants perceived themselves to act more dominantly than they actually did. Throughout, there were no sex differences.     

Emotional arousal and affiliation

Schachter's 1959 emotional comparison theory was criticized by Sarnoff and Zimbardo 1961, who demonstrated that there are certain kinds of emotional arousal in which isolation is preferred. The generality of the theory was restricted and the direction of affiliative behaviors in different emotional-arousal conditions was questioned. In an attempt to reconcile the opposing findings, affiliative reactions to general and specific emotional arousal were compared. General arousal, anxiety state, was experimentally induced by confronting subjects with unspecified and cognitively unclear threat which allowed undetermined modes of personal interpretations. Specific arousal was induced by replicating Sarnoff and Zimbardo's experimental procedures. As predicted, general arousal increased affiliation while specific arousal decreased it. Birth order failed to interact significantly with any variables, and did not affect affiliation.Based on present and previous findings, some generalizations about emotional comparison and affiliation were offered, and problems of studying underlying motivations for affiliation were discussed.     

Processes and outcomes in prevention-focused time-limited groups for girls

Processes and outcomes in 8-week prevention-focused, school-based groups for preadolescent girls were assessed in a naturalistic study. Specifically, whether such groups would facilitate their social-emotional development and whether affiliative processes in the groups were related to outcome were explored. In addition to expecting the groups to be effective, it was hypothesized that affiliative processes would be directly related to outcome and, more particularly, that increased positive affiliative feelings from the group toward the individual would be more predictive of positive treatment outcome than increased positive feelings from the individual toward the group. While findings did not support these hypotheses linking process to outcome, ancillary analyses revealed that different patterns of affiliation over time (i.e., U-shape pattern versus inverted U-shape pattern) distinguished the high- versus low-outcome participants, respectively.     

The central amygdala projection to the substantia nigra reflects prediction error information in appetitive conditioning

The central amygdala nucleus (CeA) plays a critical role in cognitive processes beyond fear conditioning. For example, intact CeA function is essential for enhancing attention to conditioned stimuli (CSs). Furthermore, this enhanced attention depends on the CeA's connections to the nigrostriatal system. In the current study, we examined the role of the CeA's connections to two midbrain dopamine regions, the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA), in processing CS information when predictions of reward or nonreward were confirmed or disconfirmed. Initially, two different retrograde tracers were injected into the SNc and the VTA of rats, to label CeA cells. Different groups of rats then received a visual CS either paired or unpaired with food. Finally, Fos induction was assessed after a test session in which rats were exposed to the visual CS alone or paired with food. Colabeling of Fos and the retrograde tracer(s) showed that CeA neurons projecting to the SNc, but not to the VTA, were engaged in processing CS information when the training and testing conditions differed. These results suggest that the CeA-nigral pathway represents prediction error information during appetitive conditioning.     

CHRONIC SOCIAL STRESS, AFFILIATION, AND CELLULAR IMMUNE RESPONSE IN NONHUMAN PRIMATES

Abstract ——We report the first experimental study of the effect of long–term (over 2 years) exposure to a stressor on cellular immune response Forty–three male cynomolgus monkeys were randomly assigned to stable or unstable social conditions for 26 months The proportion of time spent in affiliative behaviors was assessed by observations made twice weekly T–cell immune response (mitogen–stimulated cell proliferation) was assessed weekly for 3 weeks immediately following the 26–month manipulation The possibility that affiliative behavior represents an attempt to cope with social stress was supported by greater affiliation among animals m the unstable condition than in the stable condition Animals in the unstable condition also demonstrated relatively suppressed immune response More affiliative animals showed enhanced immune response, with the beneficial effects of affiliation occurring primarily among unstable animals The data are interpreted as consistent with the stress–buffering hypothesis, that IS, affiliation protects animals from the potentially pathogenic influences of chronic social stress     

Modulation of memory consolidation by the basolateral amygdala or nucleus accumbens shell requires concurrent dopamine receptor activation in both brain regions

Previous findings indicate that the basolateral amygdala (BLA) and the nucleus accumbens (NAc) interact in influencing memory consolidation. The current study investigated whether this interaction requires concurrent dopamine (DA) receptor activation in both brain regions. Unilateral, right-side cannulae were implanted into the BLA and the ipsilateral NAc shell or core in male Sprague-Dawley rats ( approximately 300 g). One week later, the rats were trained on an inhibitory avoidance (IA) task and, 48 h later, they were tested for retention. Drugs were infused into the BLA and NAc shell or core immediately after training. Post-training intra-BLA infusions of DA enhanced retention, as assessed by latencies to enter the shock compartment on the retention test. Infusions of the general DA receptor antagonist cis-Flupenthixol (Flu) into the NAc shell (but not the core) blocked the memory enhancement induced by the BLA infusions of DA. In the reverse experiment, post-training intra-NAc shell infusions of DA enhanced retention and Flu infusions into the BLA blocked the enhancement. These findings indicate that BLA modulation of memory consolidation requires concurrent DA receptor activation in the NAc shell but not the core. Similarly, NAc shell modulation of memory consolidation requires concurrent DA receptor activation in the BLA. Together with previous findings, these results suggest that the dopaminergic innervation of the BLA and NAc shell is critically involved in the modulation of memory consolidation.     

Positive expectancies and perceived impaired control mediate the influence of reward drive and rash impulsiveness on alcohol use

Recent factor analytic studies indicate that the broad trait of impulsivity comprises at least two distinct dimensions with regard to substance use. Thus, a two-factor model of impulsivity, comprising reward drive (i.e., sensitivity to rewarding stimuli) and rash impulsiveness (i.e., rash behaviour devoid of forethought), has been proposed. It is argued that distinct cognitive processes may mediate the association of these impulsivity factors with alcohol use. Specifically, it was hypothesised that drinking expectancies would mediate the association between reward drive and alcohol use, and that perceived impaired control would mediate the effect of rash impulsiveness on alcohol. Utilising established scales, 132 participants aged 18 to 70 years were surveyed in order to assess the capacity of the two-factor model to differentially predict alcohol use through distinct cognitive mediators. The hypotheses were supported, providing support for a two-factor approach. Thus, reward drive and rash impulsiveness appear to influence alcohol use through distinct cognitive processes.     

Spontaneous recovery of consummatory behavior, but not of consummatory successive negative contrast

Five experiments were designed to study spontaneous recovery (SR) in two situations involving consummatory behavior: consummatory successive negative contrast (cSNC) and consummatory extinction (cE). SR of consummatory suppression should occur if incentive downshift induces an egocentric memory encoding information about the emotional reaction to the downshift that is counterconditioned or extinguished during exposure to the downshifted reward. SR of cSNC failed to occur after resting periods of 24, 96, or 336 h interpolated following complete (Experiment 1) and incomplete (Experiment 2) recuperation of consummatory behavior, and was not induced by the opioid-receptor antagonist naloxone (2 mg/kg), known to enhance cSNC (Experiment 3). However, SR of consummatory behavior occurred across sessions in cSNC (Experiment 3) and cE (Experiments 4-5). Furthermore, naloxone facilitated cE without affecting SR (Experiments 4-5). These results are discussed in relation to evidence for the development of an egocentric memory of the aversive downshift experience in consummatory situations.     

奖赏环路与阿片成瘾:喙内侧被盖核的调节作用

喙内侧被盖核(RMTg)位于腹侧被盖区(VTA)的尾部, 富含抑制性的γ-氨基丁酸(GABA)能神经元.RMTg是中脑边缘多巴胺系统的一个综合调节器.它的GABA能神经元接受外侧缰核(LHb)的输入, 然后投射到VTA多巴胺能神经元, 进而抑制多巴胺的释放.这三个脑区是奖赏环路的重要组成部分, 其中RMTg在阿片类物质激活的奖赏环路中尤为重要.阿片类物质主要通过抑制RMTg GABA能神经元使VTA多巴胺能神经元去抑制, 进而激活奖赏系统.因此, RMTg有望成为治疗药物成瘾(尤其是阿片成瘾)的一个重要靶点.此外, 胆碱类物质作用于RMTg的毒蕈碱受体能够抑制阿片类物质诱导的奖赏效应.未来研究应深入探讨RMTg调控的负性奖赏环路, 这对弱化觅药动机,促进消退和戒断具有重要意义.     

Relationships Among Sleep Disturbance,Reward System Functioning,Anhedonia, and Depressive Symptoms

Recent models propose reward system dysfunction as a key mediator of the relationship between sleep and depression and anhedonia. This study explored interrelationships among sleep disturbance, depressive symptoms, anhedonia, and reward responsiveness. Two-hundred and sixty undergraduate students completed questionnaires and a daily diary paradigm assessing sleep, reward responsiveness, depression, anhedonia, and positive affect over 1 week. Baseline sleep disturbance was associated with depressive symptoms, anhedonia, and reward responsiveness. Daily diary sleep parameters showed differential associations with anticipatory versus consummatory reward responsiveness and positive affect. Poorer sleep quality, shorter sleep duration, and longer awakening after sleep onset predicted blunted anticipatory and consummatory reward responsiveness, while increased sleep onset latency and lower sleep efficiency predicted only decreased consummatory reward responsiveness. All sleep indices, except sleep onset latency, were associated with positive affect. Findings demonstrate unique associations between disparate sleep disturbance and reward responsiveness elements, highlighting new treatment mechanisms for anhedonia and depression.     

Facial appearance, gender, and emotion expression

Western gender stereotypes describe women as affiliative and more likely to show happiness and men as dominant and more likely to show anger. The authors assessed the hypothesis that the gender-stereotypic effects on perceptions of anger and happiness are partially mediated by facial appearance markers of dominance and affiliation by equating men's and women's faces for these cues. In 2 studies, women were rated as more angry and men as more happy-a reversal of the stereotype. Ratings of sadness, however, were not systematically affected. It is posited that markers of affiliation and dominance, themselves confounded with gender, interact with the expressive cues for anger and happiness to produce emotional perceptions that have been viewed as simple gender stereotypes.     

Anticipatory pleasure predicts motivation for reward in major depression

Anhedonia, the lack of interest or pleasure in response to hedonic stimuli or experiences, is a cardinal symptom of depression. This deficit in hedonic processing has been posited to influence depressed individuals' motivation to engage in potentially rewarding experiences. Accumulating evidence indicates that hedonic processing is not a unitary construct but rather consists of an anticipatory and a consummatory phase. We examined how these components of hedonic processing influence motivation to obtain reward in participants diagnosed with major depression and in never-disordered controls. Thirty-eight currently depressed and 30 never-disordered control participants rated their liking of humorous and nonhumorous cartoons and then made a series of choices between viewing a cartoon from either group. Each choice was associated with a specified amount of effort participants would have to exert before viewing the chosen cartoon. Although depressed and control participants did not differ in their consummatory liking of the rewards, levels of reward liking predicted motivation to expend effort for the rewards only in the control participants; in the depressed participants, liking and motivation were dissociated. In the depressed group, levels of anticipatory anhedonia predicted motivation to exert effort for the rewards. These findings support the formulation that anhedonia is not a unitary construct and suggest that, for depressed individuals, deficits in motivation for reward are driven primarily by low anticipatory pleasure and not by decreased consummatory liking.     

Psychometric Evaluation of a Controlled Social Affiliation Paradigm: Findings From Anxiety,Depressive Disorder,and Healthy Samples

Social impairments are common across many psychiatric conditions. Standardized dyadic assessments intended to elicit social affiliation between unacquainted partners are used to elucidate mechanisms that disrupt relationship formation and inform possible treatment targets; however, the psychometric properties of such paradigms remain poorly understood. This study evaluated the psychometric properties of a controlled social affiliation paradigm intended to induce connectedness between a target participant and trained confederate. Individuals with an anxiety or depressive disorder diagnosis (clinical group; n = 132) and those without (control group; n = 35) interacted face-to-face with a trained confederate; partners took turns answering a series of increasingly intimate questions about themselves. Social connectedness, affect, and affiliative behavior measures were collected during the interaction. Participant symptom and social functioning measures were collected to examine validity. The paradigm elicited escalating social connectedness throughout the task for both participants and confederates. Parallel forms (i.e., different question sets) elicited similar affiliation outcomes. Self-reported (but not behavioral) affiliation differed across some demographic variables (e.g., participant gender, Hispanic ethnicity). Within-task affiliation measures were associated with one another and with global social connectedness and social anxiety symptom measures, but not with somatic anxiety measures. Clinical participants reported lower social affiliation and positive affect reactivity and higher negative affect reactivity than healthy participants. These findings provide initial psychometric support for a standardized and controlled dyadic affiliation paradigm that could be used to reliably probe social disconnection mechanisms across psychopathology.     

The behavioral pharmacology of effort-related choice behavior: dopamine, adenosine and beyond

For many years, it has been suggested that drugs that interfere with dopamine (DA) transmission alter the "rewarding" impact of primary reinforcers such as food. Research and theory related to the functions of mesolimbic DA are undergoing a substantial conceptual restructuring, with the traditional emphasis on hedonia and primary reward yielding to other concepts and lines of inquiry. The present review is focused upon the involvement of nucleus accumbens DA in effort-related choice behavior. Viewed from the framework of behavioral economics, the effects of accumbens DA depletions and antagonism on food-reinforced behavior are highly dependent upon the work requirements of the instrumental task, and DA-depleted rats show a heightened sensitivity to response costs, especially ratio requirements. Moreover, interference with accumbens DA transmission exerts a powerful influence over effort-related choice behavior. Rats with accumbens DA depletions or antagonism reallocate their instrumental behavior away from food-reinforced tasks that have high response requirements, and show increased selection of low reinforcement/low cost options. Nucleus accumbens DA and adenosine interact in the regulation of effort-related functions, and other brain structures (anterior cingulate cortex, amygdala, ventral pallidum) also are involved. Studies of the brain systems regulating effort-based processes may have implications for understanding drug abuse, as well as symptoms such as psychomotor slowing, fatigue or anergia in depression and other neurological disorders.