Unique and Transdiagnostic Dimensions of Reward Functioning in Attention-Deficit/Hyperactivity Disorder and Alcohol Use Disorder Symptoms

Aims Contemporary theories of attention-deficit/hyperactivity disorder (ADHD) and alcohol use disorder (AUD) emphasize core dysfunctions in reward-related processes and behaviors as pathognomonic characteristics. However, to date, it is unclear which domains of reward functioning are unique to ADHD versus AUD symptom dimensions, and which represent underlying shared correlates. Methods The current study employed secondary data analyses from a large community sample of emerging adults (N = 602; 57.3% female) and novel transdiagnostic modeling (i.e. bi-factor confirmatory factor analyses and structural equation modeling) of ADHD, AUD and shared symptom dimensions to identify unique and common reward-related dimensions: environmental suppressors, reward probability, hedonic capacity, proportionate substance-related reinforcement and delay discounting. Results The presence of environmental suppressors was the only reward-related construct that correlated with the underlying ADHD-AUD shared dimension. The AUD symptom dimension was uniquely associated with proportionate substance-related reinforcement, whereas the ADHD symptom dimension was uniquely associated with limited reward probability. No significant associations were found for delay discounting or hedonic capacity. Conclusions These novel findings highlight specific aspects of reward-related functioning in ADHD, AUD and shared symptom dimensions. In so doing, this work meaningfully advances theoretical conceptualizations of these two commonly co-occurring presentations and suggests future directions for research on transdiagnostic correlates. Future longitudinal studies should include clinical samples with diagnoses of AUD and ADHD to further identify underlying correlates over time.

Aberrant orbitofrontal cortex reactivity to erotic cues in Compulsive Sexual Behavior Disorder

Background and aimsCompulsive Sexual Behavior Disorder (CSBD) is characterized by increased reactivity to erotic reward cues. Cue-encoded reward parameters, such as type (e.g. erotic or monetary) or probability of anticipated reward, shape reward-related motivational processes, increase the attractiveness of cues and therefore might enhance maladaptive behavioral patterns in CSBD. Studies on the neural patterns of cue processing in individuals with CSBD have been limited mainly to ventral striatal responses. Therefore, here we aimed to examine the cue reactivity of multiple key structures in the brain's reward system, taking into account not only the type of predicted reward but also its probability.MethodsTwenty Nine men seeking professional help due to CSBD and 24 healthy volunteers took part in an fMRI study with a modified Incentive Delay Task with erotic and monetary rewards preceded by cues indicating a 25%, 50%, or 75% chance of reward. Analyses of functional patterns of activity related to cue type and probability were conducted on the whole-brain and ROI levels.ResultsIncreased anticipatory response to cues predictive of erotic rewards was observed among CSBD participants when compared to controls, in the ventral striatum and anterior orbitofrontal cortex (aOFC). The activity in aOFC was modulated by reward probability.Discussion and conclusionsType of anticipated reward (erotic vs monetary) affects reward-related behavioral motivation in CSBD more strongly than reward probability. We present evidence of abnormal aOFC function in CSBD by demonstrating the recruitment of additional subsections of this region by erotic reward cues.

Uncertainty modulates visual maps during non-instrumental information demand

Animals are intrinsically motivated to resolve uncertainty and predict future events. This motivation is encoded in cortical and subcortical structures, but a key open question is how it generates concrete policies for attending to informative stimuli. We examined this question using neural recordings in the monkey lateral intraparietal area (LIP), a visual area implicated in attention and gaze, during non-instrumental information demand. We show that the uncertainty that was resolved by a visual cue enhanced visuo-spatial responses of LIP cells independently of reward probability. This enhancement was independent of immediate saccade plans but correlated with the sensitivity to uncertainty in eye movement behavior on longer time scales (across sessions/days). The findings suggest that topographic visual maps receive motivational signals of uncertainty, which enhance the priority of informative stimuli and the likelihood that animals will orient to the stimuli to reduce uncertainty.

A time-varying diffusion model analysis of value-based decision-making: effects of adult age and probability information saliency

Empirical evidence has shown that visually enhancing the saliency of reward probability information can ease the cognitive demands of value comparisons and improve value-based decision-making in old age. In the present study, we used a time-varying DDM that includes starting time parameters (henceforth starting time DDM, stDDM) to better understand how increasing the saliency of probability may affect the dynamics of value-based decision-making. We enhanced the saliency of reward probability by using a color-coding scheme as a decision-aid in a mixed lottery choice task, with which the decisions of younger and older adults were assessed. Older adults’ evidence accumulation processes were less sensitive to information about outcome probability and magnitude than those of younger adults. The decision-aid enhanced the weighting of probability and magnitude information in both age groups, as well as the starting time advantage for probability information relative to magnitude information. Older adults who had a lower baseline value sensitivity, as reflected in the parameters from non-aid trials, benefited more from increasing information saliency in improving decisions. Furthermore, in older adults, this aid-induced effect was related to individual’s spontaneous eye-blink rate, a potential proxy of dopamine functioning. Taken together, analyzing the behavioral data using the stDDM revealed new evidence for adult age differences during value-based decisions: not do only older adults weigh the outcome probability and magnitude less than younger adults, they also do not process information about probability sooner than magnitude. Visually enhancing the saliency of probability information can benefit older decision makers in shifting their decision dynamics to be more similar to younger adults.

Breaking Deadlocks: Reward Probability and Spontaneous Preference Shape Voluntary Decisions and Electrophysiological Signals in Humans

Choosing between equally valued options is a common conundrum, for which classical decision theories predicted a prolonged response time (RT). This contrasts with the notion that an optimal decision maker in a stable environment should make fast and random choices, as the outcomes are indifferent. Here, we characterize the neurocognitive processes underlying such voluntary decisions by integrating cognitive modelling of behavioral responses and EEG recordings in a probabilistic reward task. Human participants performed binary choices between pairs of unambiguous cues associated with identical reward probabilities at different levels. Higher reward probability accelerated RT, and participants chose one cue faster and more frequent over the other at each probability level. The behavioral effects on RT persisted in simple reactions to single cues. By using hierarchical Bayesian parameter estimation for an accumulator model, we showed that the probability and preference effects were independently associated with changes in the speed of evidence accumulation, but not with visual encoding or motor execution latencies. Time-resolved MVPA of EEG-evoked responses identified significant representations of reward certainty and preference as early as 120 ms after stimulus onset, with spatial relevance patterns maximal in middle central and parietal electrodes. Furthermore, EEG-informed computational modelling showed that the rate of change between N100 and P300 event-related potentials modulated accumulation rates on a trial-by-trial basis. Our findings suggest that reward probability and spontaneous preference collectively shape voluntary decisions between equal options, providing a mechanism to prevent indecision or random behavior.

Evidence accumulation for value computation in the prefrontal cortex during decision making

A key step of decision making is to determine the value associated with each option. The evaluation process often depends on the accumulation of evidence from multiple sources, which may arrive at different times. How evidence is accumulated for value computation in the brain during decision making has not been well studied. To address this problem, we trained rhesus monkeys to perform a decision-making task in which they had to make eye movement choices between two targets, whose reward probabilities had to be determined with the combined evidence from four sequentially presented visual stimuli. We studied the encoding of the reward probabilities associated with the stimuli and the eye movements in the orbitofrontal (OFC) and the dorsolateral prefrontal (DLPFC) cortices during the decision process. We found that the OFC neurons encoded the reward probability associated with individual pieces of evidence in the stimulus domain. Importantly, the representation of the reward probability in the OFC was transient, and the OFC did not encode the reward probability associated with the combined evidence from multiple stimuli. The computation of the combined reward probabilities was observed only in the DLPFC and only in the action domain. Furthermore, the reward probability encoding in the DLPFC exhibited an asymmetric pattern of mixed selectivity that supported the computation of the stimulus-to-action transition of reward information. Our results reveal that the OFC and the DLPFC play distinct roles in the value computation during evidence accumulation.

Unique features of stimulus-based probabilistic reversal learning

Reversal learning paradigms are widely-used assays of behavioral flexibility with their probabilistic versions being more amenable to studying integration of reward outcomes over time. Prior research suggests differences between initial learning and learning following reversals including higher learning rates, a greater need for inhibitory control, and more perseveration after reversals. However, it is not well-understood what aspects of stimulus-based reversal learning are unique to reversals, and whether and how differences between initial and post-reversal learning depend on reward probability. Here, we used a visual probabilistic discrimination and reversal learning paradigm during which male and female rats selected between a pair of stimuli associated with different reward probabilities. We compared various measures of accuracy, rewards collected, omissions, latencies, win-stay/lose-shift strategies, and indices of perseveration between two different reward probability schedules. We found that discrimination (pre-reversal) and reversal learning are behaviorally more unique than similar: longer choice latencies following incorrect trials, lesser win-stay and lose-shift strategies employed, and more perseveration in early reversal learning. Additionally, fit of choice behavior using reinforcement learning models revealed a lower sensitivity to the difference in subjective reward values (greater exploration) and higher learning rates for the reversal phase. Interestingly, a consistent reward probability group difference emerged with a richer environment associated with longer reward collection latencies than a leaner environment. We also replicated previous reports on sex differences in reversal learning. Future studies should systematically compare the neural correlates of fine-grained behavioral measures to reveal possible dissociations in how the circuitry is recruited in each phase.

Base rate neglect and neural computations for subjective weight in decision under uncertainty

Base rate neglect, an important bias in estimating probability of uncertain events, describes humans’ tendency to underweight base rate (prior) relative to individuating information (likelihood). However, the neural mechanisms that give rise to this bias remain elusive. In this study, subjects chose between uncertain prospects where estimating reward probability was essential. We found that when the variability of prior and likelihood information about reward probability were systematically manipulated, prior variability significantly affected the degree to which subjects underweight the base rate of reward probability. Activity in the orbitofrontal cortex, medial prefrontal cortex, and putamen represented the relative subjective weight that reflected such bias. Further, sensitivity to likelihood relative to prior variability in the putamen correlated with individuals’ overall tendency to underweight base rate. These findings suggest that in combining prior and likelihood, relative sensitivity to information variability and subjective-weight computations critically contribute to the individual heterogeneity in base rate neglect.

Probabilistic Learning in Children With Attention-Deficit/Hyperactivity Disorder

Objective: The current study examined instrumental learning in ADHD. Method: A total of 58 children with ADHD and 58 typically developing (TD) children performed a probabilistic learning task using three reward probability conditions (100%, 85%, 70% reward). After a learning phase, application of what was learned was assessed in a test phase. Results: Results showed that children with ADHD performed less accurate compared with TD children during the learning phase, particularly in the 100% and 85% reward probability conditions. These findings were accompanied by a blunted learning rate in the first few task trials. Furthermore, children with ADHD showed poorer application of what was learned. Conclusion: To conclude, children with ADHD show initial learning problems, but increased performance in a similar manner as TD children independent of the probability of reward, although they fail to apply their knowledge. Findings are of clinical relevance as the application of knowledge is important to successfully adapt to daily challenges in life.