Rewarding Events Research Articles

First impressions or good endings? Preferences depend on when you ask.

Rewards often unfold over time; we must summarize events in memory to guide future choices. Do first impressions matter most, or is it better to end on a good note? Across nine studies (N = 569), we tested these competing intuitions and found that preferences depend on when rewards occur and when we are asked to evaluate an experience. In our "garage sale" task, participants opened boxes containing sequences of objects with values. All boxes were equally valuable, but rewards were either evenly distributed or clustered at the beginning, middle, or end of the sequence. First, we tested preferences and valuation shortly after learning; we consistently found that boxes with rewards at the beginning were strongly preferred and overvalued. Object-value associative memory was impaired in boxes with early rewards, suggesting that value information was linked to the box rather than the objects. However, when tested after an overnight delay, participants equally preferred boxes with any cluster of rewards, whether at the beginning, middle, or end of the experience. Finally, we demonstrated that evaluating shortly after an experience led to lasting preferences for early rewards. Overall, we show that people summarize rewarding experiences in a nonlinear and time-dependent way, unifying prior work on affect, memory, and decision making. We propose that short-term preferences are biased by first impressions. However, when we wait and evaluate an experience after a delay, we summarize rewarding events in memory to inform adaptive longer term preferences. Preferences depend on when rewards occur and when we first evaluate an experience. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Social Media and Adolescents' Prosocial Behavior: Evidence of the Interaction Between Short Videos and Social Value Orientation.

Social media significantly influences adolescents' prosocial behavior. With smartphones becoming ubiquitous, short videos have emerged as the predominant social media format for adolescents. However, the effects of adolescents' engagement with short videos on their prosocial behavior remain uncertain. This study aims to address the problem of how short videos (content and consequences) affect prosocial behavior in adolescents, and simultaneously explores the differences of this effect among individuals with different social value orientations. The current study conducted two research laboratory experiments using the between-subject study design of two factors. Study 1 (N=148) reveals that viewing prosocial short videos significantly predicts adolescents' prosocial behavior more so than neutral short videos. The interaction between short video content and social value orientation on prosocial behavior illustrates that the encouraging impact of prosocial content is primarily evident in prosocial individuals, rather than in pro-self individuals. In Study 2 (N=152), we introduce new dimensions by assessing adolescents' response to varying consequences of the same prosocial behavior (ie, reward, punishment) within the short video context. Findings indicate that reward consequences significantly bolster adolescents' prosocial behavior, whereas punitive measures tend to adversely affect it. Furthermore, the interaction between the consequences of prosocial short videos and social value orientation suggests that prosocial individuals exhibit no significant behavioral difference between rewards and punishments; instead, the reward/punishment consequences notably influence the prosocial behavior of pro-self individuals. Short videos (content and consequences) and social value orientations interactively influence adolescents' prosocial behaviors. This study underscores the need to recognize individual differences in adolescents' use of short videos and its impact on their prosocial behavior, particularly highlighting the crucial role of their social value orientations. Practically, the research offers valuable insights for parents and professionals seeking to foster adolescents' prosocial behavior.

Anterior cingulate cortex provides the neural substrates for feedback-driven iteration of decision and value representation

Adjusting decision-making under uncertain and dynamic situations is the hallmark of intelligence. It requires a system capable of converting feedback information to renew the internal value. The anterior cingulate cortex (ACC) involves in error and reward events that prompt switching or maintenance of current decision strategies. However, it is unclear whether and how the changes of stimulus-action mapping during behavioral adaptation are encoded, nor how such computation drives decision adaptation. Here, we tracked ACC activity in male mice performing go/no-go auditory discrimination tasks with manipulated stimulus-reward contingencies. Individual ACC neurons integrate the outcome information to the value representation in the next-run trials. Dynamic recruitment of them determines the learning rate of error-guided value iteration and decision adaptation, forming a non-linear feedback-driven updating system to secure the appropriate decision switch. Optogenetically suppressing ACC significantly slowed down feedback-driven decision switching without interfering with the execution of the established strategy.

Differential phase-amplitude coupling in nucleus accumbens and orbitofrontal cortex reflects decision-making during a delay discounting task

BackgroundThe impulsive choice is characterized by the preference for a small immediate reward over a bigger delayed one. The mechanisms underlying impulsive choices are linked to the activity in the Nucleus Accumbens (NAc), the orbitofrontal cortex (OFC), and the dorsolateral striatum (DLS). While the study of functional connectivity between brain areas has been key to understanding a variety of cognitive processes, it remains unclear whether functional connectivity differentiates impulsive-control decisions. MethodsTo study the functional connectivity both between and within NAc, OFC, and DLS during a delay discounting task, we concurrently recorded local field potential in NAc, OFC, and DLS in rats. We then quantified the degree of phase-amplitude coupling (PAC), coherence, and Granger Causality between oscillatory activities in animals exhibiting either a high (HI) or low (LI) tendency for impulsive choices. ResultsOur results showed a differential pattern of PAC during decision-making in OFC and NAc, but not in DLS. While theta-gamma PAC in OFC was associated with self-control decisions, a higher delta-gamma PAC in both OFC and NAc biased decisions toward impulsive choices in both HI and LI groups. Furthermore, during the reward event, Granger Causality analysis indicated a stronger NAc➔OFC gamma contribution in the HI group, while the LI group showed a higher OFC➔NAc gamma contribution. ConclusionsThe overactivity in NAc during reward in the HI group suggests that exacerbated contribution of NAcCore can lead to an overvaluation of reward that biases the behavior toward the impulsive choice.

Distinct Action Signals by Subregions in the Nucleus Accumbens during STOP-Change Performance.

The nucleus accumbens (NAc) is thought to contribute to motivated behavior by signaling the value of reward-predicting cues and the delivery of anticipated reward. The NAc is subdivided into core and shell, with each region containing different populations of neurons that increase or decrease firing to rewarding events. While there are numerous theories of functions pertaining to these subregions and cell types, most are in the context of reward processing, with fewer considering that the NAc might serve functions related to action selection more generally. We recorded from single neurons in the NAc as rats of both sexes performed a STOP-change task that is commonly used to study motor control and impulsivity. In this task, rats respond quickly to a spatial cue on 80% of trials (GO) and must stop and redirect planned movement on 20% of trials (STOP). We found that the activity of reward-excited neurons signaled accurate response direction on GO, but not STOP, trials and that these neurons exhibited higher precue firing after correct trials. In contrast, reward-inhibited neurons significantly represented response direction on STOP trials at the time of the instrumental response. Finally, the proportion of reward-excited to reward-inhibited neurons and the strength of precue firing decreased as the electrode traversed the NAc. We conclude that reward-excited cells (more common in core) promote proactive action selection, while reward-inhibited cells (more common in shell) contribute to accurate responding on STOP trials that require reactive suppression and redirection of behavior.

Dialogues on the Theory of Reward for the Good and Retribution for the Evil during Late Ming and Early Qing Dynasties

Abstract The theory of reward for the good and retribution for the evil (善恶报应) was one of the key issues in the dialogue between Catholicism and indigenous religions in the late Ming and early Qing dynasties. Under the monotheistic framework, Catholicism advocates a supernatural God for rewarding good and punishing evil. It thus had a more logical and rigorous theological argumentation at its disposal in its exchanges and dialogues with Chinese native religions on the standards of good and evil, the question of who has the right to reward and punish, the consequences of reward and retribution, and so on. This article begins by analyzing the Confucian theory of stimulus-response between the heaven and human beings (天人感应). Secondly, it sketches the views expressed by the theories of reward for the good and retribution for the evil in Buddhism and Taoism. Then, it discusses the Catholic views on rewarding good and punishing evil during late Ming and early Qing, and also examines the responses of the native religions of China to the Catholic views on rewarding good and punishing evil. Finally, it summarizes the similarities and differences of the theories of reward for the good and retribution for the evil between Catholicism and Confucianism, Buddhism and Taoism. As for the intention to do good, there were some commonalities between Catholicism and Confucianism, Buddhism and Taoism in the movement to promote good deeds during late Ming and early Qing. However, they were distinct in the perspective of the standards of good and evil, the subjects of retribution, and the roles of individuals in retribution, which caused the conflicts between Catholicism and its opponents in China. The introduction of the Catholic theory of reward for the good and retribution for the evil has undoubtedly further enriched Chinese religious thoughts since the late Ming dynasty.

NAPE-PLD in the ventral tegmental area regulates reward events, feeding and energy homeostasis.

The N-acyl phosphatidylethanolamine-specific phospholipase D (NAPE-PLD) catalyzes the production of N-acylethanolamines (NAEs), a family of endogenous bioactive lipids, which are involved in various biological processes ranging from neuronal functions to energy homeostasis and feeding behaviors. Reward-dependent behaviors depend on dopamine (DA) transmission between the ventral tegmental area (VTA) and the nucleus accumbens (NAc), which conveys reward-values and scales reinforced behaviors. However, whether and how NAPE-PLD may contribute to the regulation of feeding and reward-dependent behaviors has not yet been investigated. This biological question is of paramount importance since NAEs are altered in obesity and metabolic disorders. Here, we show that transcriptomic meta-analysis highlights a potential role for NAPE-PLD within the VTA→NAc circuit. Using brain-specific invalidation approaches, we report that the integrity of NAPE-PLD is required for the proper homeostasis of NAEs within the midbrain VTA and it affects food-reward behaviors. Moreover, region-specific knock-down of NAPE-PLD in the VTA enhanced food-reward seeking and reinforced behaviors, which were associated with increased in vivo DA release dynamics in response to both food- and non-food-related rewards together with heightened tropism towards food consumption. Furthermore, midbrain knock-down of NAPE-PLD, which increased energy expenditure and adapted nutrient partitioning, elicited a relative protection against high-fat diet-mediated body fat gain and obesity-associated metabolic features. In conclusion, these findings reveal a new key role of VTA NAPE-PLD in shaping DA-dependent events, feeding behaviors and energy homeostasis, thus providing new insights on the regulation of body metabolism.

FORECASTING THE FUTURE: OLDER ADULTS’ ANTICIPATED STRESSORS AND REWARDS IN THE CONTEXT OF COVID-19

Abstract Stress research typically focuses on past/current events as opposed to future ones. We identified future anticipated stressful and rewarding events at 2 timepoints utilizing qualitative data from older adults (N = 103, Mage = 68.11, 68.9% female, 93.2% white) who participated in a study of social reintegration after vaccines were available in the US. COVID-19 cases were typically below 1 million during T1 (Fall 2021), but exceeded 5 million during T2 (Winter 2022), coinciding with the Omicron variant. This afforded the opportunity to examine anticipated stressors and rewards at timepoints with different levels of COVID-19 threat. We used content analysis to identify anticipated stressors and rewards, which fit into 13 categories (Cohen’s κ = .86-.96) and examined rates of ambivalence (i.e., same event was a stressor and reward within timepoints) and chronicity (i.e., same stressor or reward was named across timepoints). At T1, the modal stressor was own transition/change (13.6%; e.g., relocating). At T2, it was the pandemic (20.4%; e.g., family member recovering from COVID). Family/friend relationships (e.g., celebrating grandkids’ birthdays) was the modal reward at T1 (32%) and T2 (24.3%). A quarter of participants demonstrated ambivalence (T1 = 23.3%; T2 = 28.2%). Stressor and reward chronicity (22.3% and 32%, respectively) were low. Findings highlight variability in the events older adults were concerned and excited about within and across timepoints. Salience of the pandemic as an anticipated stressor ebbed and flowed alongside emerging variants, despite vaccine availability.

Explicit learning based on reward prediction error facilitates agile motor adaptations.

Error based motor learning can be driven by both sensory prediction error and reward prediction error. Learning based on sensory prediction error is termed sensorimotor adaptation, while learning based on reward prediction error is termed reward learning. To investigate the characteristics and differences between sensorimotor adaptation and reward learning, we adapted a visuomotor paradigm where subjects performed arm movements while presented with either the sensory prediction error, signed end-point error, or binary reward. Before each trial, perturbation indicators in the form of visual cues were presented to inform the subjects of the presence and direction of the perturbation. To analyse the interconnection between sensorimotor adaptation and reward learning, we designed a computational model that distinguishes between the two prediction errors. Our results indicate that subjects adapted to novel perturbations irrespective of the type of prediction error they received during learning, and they converged towards the same movement patterns. Sensorimotor adaptations led to a pronounced aftereffect, while adaptation based on reward consequences produced smaller aftereffects suggesting that reward learning does not alter the internal model to the same degree as sensorimotor adaptation. Even though all subjects had learned to counteract two different perturbations separately, only those who relied on explicit learning using reward prediction error could timely adapt to the randomly changing perturbation. The results from the computational model suggest that sensorimotor and reward learning operate through distinct adaptation processes and that only sensorimotor adaptation changes the internal model, whereas reward learning employs explicit strategies that do not result in aftereffects. Additionally, we demonstrate that when humans learn motor tasks, they utilize both learning processes to successfully adapt to the new environments.

Imager-A mobile health mental imagery-based ecological momentary intervention targeting reward sensitivity: A randomized controlled trial.

Robust reward sensitivity may help preserve mental well-being in the face of adversity and has been proposed as a key stress resilience factor. Here, we present a mobile health application, "Imager," which targets reward sensitivity by training individuals to create mental images of future rewarding experiences. We conducted a two-arm randomized controlled trial with 95 participants screened for reward sensitivity. Participants in the intervention group received an ecological momentary intervention-Imager, which encouraged participants to create mental images of rewarding events for 1 week. The control group participants received only ecological momentary assessment, without the instruction to generate mental images. Adherence to Imager was high; participants in the intervention group engaged in 88% of the planned activities. In the follow-up assessment, the intervention group reported less mental health symptoms, mainly in depression (β = -0.34, df = 93, p = .004) and less perceived stress (β = -0.18, df = 93, p = .035), than control group participants and compared with the baseline assessment. Our results show the positive effects of Imager on mental health symptoms. The encouraging effects of the app on mental health outcomes may lead to greater use of ecological momentary interventions in the clinical preventive practice of affective disorders.

Detection, processing and reinforcement of social cues: regulation by the oxytocin system.

Many social behaviours are evolutionarily conserved and areessential for the healthy development ofan individual. The neuropeptide oxytocin (OXT) is crucial for the fine-tuned regulation of social interactions in mammals. The advent and application of state-of-the-art methodological approaches that allow the activity of neuronal circuits involving OXT to be monitored and functionally manipulated in laboratory mammals have deepened our understanding of the roles of OXT in these behaviours. In this Review, we discuss how OXT promotes the sensory detection and evaluation of social cues, the subsequent approach and display of social behaviour, and the rewarding consequences of social interactions in selected reproductive and non-reproductive social behaviours. Social stressors - such as social isolation, exposure to social defeat or social trauma, and partner loss - are often paralleled by maladaptations of the OXT system, and restoring OXT system functioning can reinstate socio-emotional allostasis. Thus, the OXT system acts as a dynamic mediator of appropriate behavioural adaptations to environmental challenges by enhancing and reinforcing social salience and buffering social stress.

Bimodal modulation of L1 interneuron activity in anterior cingulate cortex during fear conditioning.

The anterior cingulate cortex (ACC) plays a crucial role in encoding, consolidating and retrieving memories related to emotionally salient experiences, such as aversive and rewarding events. Various studies have highlighted its importance for fear memory processing, but its circuit mechanisms are still poorly understood. Cortical layer 1 (L1) of the ACC might be a particularly important site of signal integration, since it is a major entry point for long-range inputs, which is tightly controlled by local inhibition. Many L1 interneurons express the ionotropic serotonin receptor 3a (5HT3aR), which has been implicated in post-traumatic stress disorder and in models of anxiety. Hence, unraveling the response dynamics of L1 interneurons and subtypes thereof during fear memory processing may provide important insights into the microcircuit organization regulating this process. Here, using 2-photon laser scanning microscopy of genetically encoded calcium indicators through microprisms in awake mice, we longitudinally monitored over days the activity of L1 interneurons in the ACC in a tone-cued fear conditioning paradigm. We observed that tones elicited responses in a substantial fraction of the imaged neurons, which were significantly modulated in a bidirectional manner after the tone was associated to an aversive stimulus. A subpopulation of these neurons, the neurogliaform cells (NGCs), displayed a net increase in tone-evoked responses following fear conditioning. Together, these results suggest that different subpopulations of L1 interneurons may exert distinct functions in the ACC circuitry regulating fear learning and memory.

Positive affect training to reduce mental health problems during the COVID-19 pandemic: a proof-of-concept randomised clinical trial

BackgroundThe social restrictions occurring during the pandemic contributed to loss of many sources of reward, which contributes to poor mental health.ObjectiveThis trial evaluated a brief positive affect training programme to...

Rat hippocampal CA1 region represents learning-related action and reward events with shorter latency than the lateral entorhinal cortex

The hippocampus and entorhinal cortex are deeply involved in learning and memory. However, little is known how ongoing events are processed in the hippocampal-entorhinal circuit. By recording from head-fixed rats during action-reward learning, here we show that the action and reward events are represented differently in the hippocampal CA1 region and lateral entorhinal cortex (LEC). Although diverse task-related activities developed after learning in both CA1 and LEC, phasic activities related to action and reward events differed in the timing of behavioral event representation. CA1 represented action and reward events almost instantaneously, whereas the superficial and deep layers of the LEC showed a delayed representation of the same events. Interestingly, we also found that ramping activity towards spontaneous action was correlated with waiting time in both regions and exceeded that in the motor cortex. Such functional activities observed in the entorhinal-hippocampal circuits may play a crucial role for animals in utilizing ongoing information to dynamically optimize their behaviors.

0039 Investigating the role of striatal dopamine in sleep and narcolepsy-cataplexy

Abstract Introduction Dopamine release in the striatum is known to govern reward, motor, and sleep behaviors. There also exists a link between pharmacological manipulation of dopamine receptors and cataplexy occurrence, yet the precise spatial and temporal dynamics of dopamine release in relation to cataplexy onset are not understood. In the present study, we evaluate dopamine release dynamics in orexin knockout (OX KO) mice during cataplexy and physiological behaviors. Methods OX KO mice were implanted with EEG/EMG electrodes, and dLight1.1 was expressed in the nucleus accumbens core (NAcc), shell (NAcSh), and dorsolateral striatum (DLS) to perform in vivo fiber photometry of dopamine release in freely-moving animals. In NAcc and NAcSh mice, ChrimsonR was retrogradely expressed in the ventral tegmental area (VTA), to allow for precise optogenetic control of midbrain dopamine projections to different regions of the striatum. We also expressed dLight1.1 in the NAcc of wildtype (WT) mice as a control. Three different stimulation parameters were used in independent recordings: phasic 20 Hz stimulation, phasic 10-40 Hz variable stimulation, and tonic 2 Hz stimulation. Results First, we show that while dopamine release in response to rewarding behaviors is muted in OX KO animals, there is no difference in dopamine release across sleep state transitions between OX KO and WT animals. Second, we demonstrate that there is a striking increase in dopamine release in both the NAcc and NAcSh, but not in the DLS, at the onset of cataplexy. This increase occurs independently of the behaviors that the animals were engaged in immediately prior to cataplexy, suggesting that the increase is characteristic of all cataplexy episodes. Finally, we find that while high frequency phasic stimulation did not affect cataplexy frequency, low frequency, tonic stimulation reduced both cataplexy and REM occurrence. Conclusion We show that there are differences in dopamine release in response to rewarding events, but not changes in sleep states, in OX KO and WT animals. We also identify dopamine release in the ventral striatum as a key node in cataplexy regulation, which helps to further our understanding of the limbic circuitry that underlies narcolepsy symptoms. Support (if any) University of Michigan Gilmore Award and Rackham Graduate Research Award.

Environmental context-dependent activation of dopamine neurons via putative amygdala-nigra pathway in macaques

Seeking out good and avoiding bad objects is critical for survival. In practice, objects are rarely good every time or everywhere, but only at the right time or place. Whereas the basal ganglia (BG) are known to mediate goal-directed behavior, for example, saccades to rewarding objects, it remains unclear how such simple behaviors are rendered contingent on higher-order factors, including environmental context. Here we show that amygdala neurons are sensitive to environments and may regulate putative dopamine (DA) neurons via an inhibitory projection to the substantia nigra (SN). In male macaques, we combined optogenetics with multi-channel recording to demonstrate that rewarding environments induce tonic firing changes in DA neurons as well as phasic responses to rewarding events. These responses may be mediated by disinhibition via a GABAergic projection onto DA neurons, which in turn is suppressed by an inhibitory projection from the amygdala. Thus, the amygdala may provide an additional source of learning to BG circuits, namely contingencies imposed by the environment.

Affective trajectories: Are hens influenced by positive and negative changes in their living conditions?

Most studies of the effects of housing and husbandry on animals' affective states and welfare investigate the impact of stable living conditions, comparing for example, animals living in enriched environments with those living in non-enriched ones. Changes in living conditions, including from more to less enriched environments, have also been found to have effects on measures of affective state and welfare in some species. But these studies have not investigated whether it is the trajectory of change that has affected the animals (e.g., worsening conditions), or simply the nature of their final environment (e.g., non-enriched). Here, we hypothesised that laying hens living in worsening conditions across a six-week period (gradually moving from preferred to non-preferred living conditions; "Trajectory to Non-Preferred", TNP, n = 30), would show evidence of more negative affective states and poorer welfare than those living continuously in non-preferred conditions for the same duration ("Stable Non-Preferred", SNP, n = 30). We also hypothesised that hens living in improving conditions (gradually moving from non-preferred to preferred living conditions; "Trajectory to Preferred", TP, n = 30), would show evidence of more positive affective states and better welfare than those living continuously in preferred conditions ("Stable Preferred", SP, n = 30). The preferred living condition provided extensive resources and intermittent rewarding events (such as the delivery of food treats) known to be valued and preferred by most hens, while the non-preferred living condition provided just basic resources and intermittent aversive events (e.g., loud noises). The hens' affective states and welfare were measured using home-pen behavioural observations, body condition assessments, physiological stress measures (e.g., blood corticosterone, glucose, etc.), physical challenge tests, and judgement bias tests. A number of differences between hens in the trajectory and stable living conditions were found: TP hens were lighter, showed more foraging behaviour and less standing alert and head-shaking than SP hens, while TNP hens showed more head-shaking, mild feather pecking and aggressive attacking of pen mates than SNP hens. However, some of these differences failed to reach significance following Benjamini adjustments for multiple testing. The groups also did not differ in their judgement biases (measured in a sub-sample of 12 hens per experimental group), response to physical challenges, or measures of physiological stress. We conclude that the hens in the present study showed some evidence of responsiveness to 'affective trajectories' in their living conditions, but no definitive effects on their affective states and welfare.

Aggression Results in the Phosphorylation of ERK1/2 in the Nucleus Accumbens and the Dephosphorylation of mTOR in the Medial Prefrontal Cortex in Female Syrian Hamsters.

Like many social behaviors, aggression can be rewarding, leading to behavioral plasticity. One outcome of reward-induced aggression is the long-term increase in the speed in which future aggression-based encounters is initiated. This form of aggression impacts dendritic structure and excitatory synaptic neurotransmission in the nucleus accumbens, a brain region well known to regulate motivated behaviors. Yet, little is known about the intracellular signaling mechanisms that drive these structural/functional changes and long-term changes in aggressive behavior. This study set out to further elucidate the intracellular signaling mechanisms regulating the plasticity in neurophysiology and behavior that underlie the rewarding consequences of aggressive interactions. Female Syrian hamsters experienced zero, two or five aggressive interactions and the phosphorylation of proteins in reward-associated regions was analyzed. We report that aggressive interactions result in a transient increase in the phosphorylation of extracellular-signal related kinase 1/2 (ERK1/2) in the nucleus accumbens. We also report that aggressive interactions result in a transient decrease in the phosphorylation of mammalian target of rapamycin (mTOR) in the medial prefrontal cortex, a major input structure to the nucleus accumbens. Thus, this study identifies ERK1/2 and mTOR as potential signaling pathways for regulating the long-term rewarding consequences of aggressive interactions. Furthermore, the recruitment profile of the ERK1/2 and the mTOR pathways are distinct in different brain regions.

Internet-delivered approach-avoidance conflict task shows temporal stability and relation to trait anxiety

Excessive avoidance causes functional impairment and maintains anxiety disorders. In the laboratory, approach-avoidance conflict tasks (AACT) can be used to study approach-avoidance behavior in mixed outcome situations (i.e., the same behavior entails both aversive and rewarding consequences). We tested the feasibility of a novel, internet-delivered AACT (iAACT) by conceptually replicating results from laboratory AACTs, including the temporal stability of results and the relation between trait anxiety and approach-avoidance behavior. Individuals from the general population (n = 186) completed a measure of trait anxiety and the iAACT, which entailed choosing either to approach aversive stimuli (image-sound) and receive a reward (points), or to avoid them and not receive a reward (i.e., costly avoidance). The temporal stability of approach-avoidance behavior was assessed by inviting participants to repeat the iAACT six weeks later (n = 91). Consistent with previous findings in laboratory AACTs, results showed that approach behavior to aversive stimuli increased with higher reward levels. These findings were replicated in the follow-up session. Also consistent with previous studies, higher trait anxiety was associated with elevated costly avoidance. In conclusion, the consistency of our results with laboratory studies indicates that the iAACT is feasible and may provide a cost-effective and scalable method to study anxiety-related approach-avoidance behavior remotely.

Dopamine systems and biological rhythms: Let's get a move on.

How dopamine signaling regulates biological rhythms is an area of emerging interest. Here we review experiments focused on delineating dopamine signaling in the suprachiasmatic nucleus, nucleus accumbens, and dorsal striatum to mediate a range of biological rhythms including photoentrainment, activity cycles, rest phase eating of palatable food, diet-induced obesity, and food anticipatory activity. Enthusiasm for causal roles for dopamine in the regulation of circadian rhythms, particularly those associated with food and other rewarding events, is warranted. However, determining that there is rhythmic gene expression in dopamine neurons and target structures does not mean that they are bona fide circadian pacemakers. Given that dopamine has such a profound role in promoting voluntary movements, interpretation of circadian phenotypes associated with locomotor activity must be differentiated at the molecular and behavioral levels. Here we review our current understanding of dopamine signaling in relation to biological rhythms and suggest future experiments that are aimed at teasing apart the roles of dopamine subpopulations and dopamine receptor expressing neurons in causally mediating biological rhythms, particularly in relation to feeding, reward, and activity.