Variation in reward- and error-related neural measures attributable to age, gender, race, and ethnicity

Medial prefrontal transcranial alternating current stimulation for apathy in Huntington's disease

We investigated the effects of transcranial alternating current stimulation (tACS) targeted to the bilateral medial prefrontal cortex (mPFC) and administered at either delta or alpha frequencies, on brain activity and apathy in people with Huntington's disease (HD) (n = 17). Given the novelty of the protocol, neurotypical controls (n = 20) were also recruited. All participants underwent three 20-min sessions of tACS; one session at alpha frequency (Individualised Alpha Frequency (IAF), or 10 Hz when an IAF was not detected); one session at delta frequency (2 Hz); and a session of sham tACS. Participants completed the Monetary Incentive Delay (MID) task with simultaneous recording of EEG immediately before and after each tACS condition. The MID task presents participants with cues signalling potential monetary gains or losses that increase activity in key regions of the cortico-basal ganglia-thalamocortical networks, with dysfunction of the latter network being implicated in the pathophysiology of apathy. We used the P300 and Contingent Negative Variation (CNV) event-related potentials elicited during the MID task as markers of mPFC engagement. HD participants' CNV amplitude significantly increased in response to alpha-tACS, but not delta-tACS or sham. Neurotypical controls' P300 and CNV were not modulated by any of the tACS conditions, but they did demonstrate a significant decrease in post-target response times following alpha-tACS. We present this as preliminary evidence of the ability of alpha-tACS to modulate brain activity associated with apathy in HD.

Temporal dynamics of emotional processing: Parsing trial-wise variance of the late positive potential using Generalizability Theory

The reliability of individual trial event-related potential (ERP) components extracted from electroencephalogram has been consistently questioned since ERP research began. This ambivalence is based on misunderstood assumptions stemming from Cronbach and Classical Test Theory. Contemporary methods allow for the reliability of individual ERP trials to be estimated and for analyses of these trial-level ERP components to be meaningfully parsed. We illustrate the use of Generalizability Theory procedures in estimating the reliability of trial-level ERPs using the late positive potential (LPP), a neural measure of motivated attention toward emotionally evocative stimuli. Individuals (N = 88) completed a passive viewing task while continuous EEG was recorded. Variability in trial-level LPP responses was decomposed into facets corresponding to individual differences, chronological trial within block, stimulus type, their two-way interactions, and specific stimuli. We estimated various reliability coefficients and found that both overall and category-specific person-level LPP estimates have good-to-excellent reliability, while the reliability of within-person differences (i.e., change) between arousal categories was fair for the early LPP. These results were generally consistent across time windows, but were highest early in the LPP time course. We argue that investigating reliability using trial-level data allows researchers to pursue hypotheses focused on neurophysiological dynamics that unfold over the course of an experiment and not risk false inferences (i.e., ecological fallacy) when using person-level aggregates to deduce such processes. Moreover, such analyses provide information that allows researchers to optimize their protocols by potentially reducing the number of individual trials, burden on participants, and cost, while retaining sufficient reliability.

Associations between parental conflict and social and monetary reward responsiveness in adolescents with clinical depression

Increased rates of depression beginning in adolescence are thought to be attributed in part to marked developmental changes in reward systems and interpersonal relationships. Blunted reward response has been observed in depression and this may be shaped in part by social experiences, raising questions about the combined associations of parental conflict, depression, and reward response in both social and monetary domains. The present study used the reward positivity (RewP), an event-related potential that indexes both monetary and social reward processing, to examine the unique and combined associations of parental conflict and depressive symptoms on reward responsiveness in adolescents with clinical depression (N = 70) 14-18 years of age (M = 15.81, SD = 1.46; 65.7% female). Results indicated that depressive symptoms interacted with maternal conflict in characterizing the RewP to social, but not monetary, rewards. Specifically, higher levels of current depressive symptoms and potentiated maternal conflict together were associated with an attenuated RewP to social rewards in this clinical sample. We found no significant effects of paternal conflict. This investigation highlights maternal conflict as an important environmental factor for reward responsiveness and also emphasizes the utility of examining social reward responsiveness in depression in order to better understand the impacts of contextual factors.

Motivationally salient cue processing measured using the monetary incentive delay (MID) task with electroencephalography (EEG): A potential marker of apathy in Huntington's disease

We explored the utility of the Monetary Incentive Delay (MID) task with concurrent encephalography (EEG) as a marker of apathy in people with Huntington's disease (HD) as well as neurotypical controls. Specifically, we assessed between and within-group differences in the amplitude of the P300 and Contingent Negative Variation (CNV) event-related potentials as a function of motivational salience. In contrast to neurotypical controls, HD participants' ERP amplitudes were not differentially modulated by motivationally salient cues (i.e., signalling potential 'gain' or 'loss') compared to 'neutral' cues. Difference waves isolating amplitude specific to the motivationally salient cues were calculated for the P300 and CNV. Only the difference waves for ERPs elicited by 'gain' cues differentiated the groups. The CNV difference wave was also significantly correlated with clinical measures of apathy and processing speed in the HD group. These findings provide initial support for the use of the MID with EEG as a marker of apathy in HD, and its potential as a sensitive outcome measure for novel treatment development.

Ethnic differences in behavioral and physiological indicators of sensitivity to threat

The clinical presentation of anxiety may differ between Hispanics/Latinx (H/L) and non-H/L, although findings on ethnic differences in self-reported anxiety symptoms have been mixed. Fewer studies have focused on ethnic differences in quick and relatively automatic laboratory-assessed indicators of anxiety symptoms, which have the potential to be more objective indicators than self-report. Therefore, the present study examined ethnic differences in two laboratory-assessed indicators of threat sensitivity (an important transdiagnostic mechanism of anxiety): attentional bias to threat and electromyography startle reactivity to threat. White H/L (n = 117) and White non-H/L (n = 168) adults who were matched on demographics and lifetime psychopathology (including anxiety) completed a dot-probe task to assess attentional bias to threat and the No-Predictable-Unpredictable threat (NPU) task to assess startle reactivity to threat. Results indicated that H/L displayed less Slow OrientationRB (β = -0.27, p = 0.032, R2β∗ = 0.02), and increased Slow DisengagementRB (β = 0.31, p = 0.016, R2β∗ = 0.02) compared to non-H/L. H/L exhibited blunted overall startle compared to non-H/L (β = -0.30, p = 0.014, R2β∗ = 0.02), but groups did not differ in startle reactivity to either predictable or unpredictable threat. In summary, H/L and non-H/L may differ in their experience and presentation of anxiety symptoms and such differences may vary across indicators of sensitivity to threat.

Event-related potential (ERP) measures of error processing as biomarkers of externalizing disorders: A narrative review

Previous studies have shown that electrophysiological measures of error processing are affected in patients at risk or diagnosed with internalizing disorders, hence, suggesting that error processing could be a suitable biomarker for internalizing disorders. In this narrative review, we will evaluate studies that address the role of event-related potential (ERP) measures of error-processing in externalizing disorders and discuss to what extend these can be considered a biomarker for externalizing disorders. Currently, there is evidence for the notion that electrophysiological indices of error processing such as the error-related negativity (ERN) and error positivity (Pe) are reduced in individuals with substance use disorders, attention-deficit/hyperactivity disorder, and in forensic populations. However, it remains unclear whether this is also the case for other understudied disorders such as behavioral addiction. Furthermore, to fully understand how these deficits affect day to day behavior, we encourage research to focus on testing current theories and hypotheses of ERN and Pe. In addition, we argue that within an externalizing disorder, individual differences in error processing deficits may be related to prognosis and gender of the patient, methodological issues and presence of comorbidity. Next, we review studies that have related treatment trajectories with ERP measures of error processing, and we discuss the prospect of improving error processing as a treatment option. We conclude that ERP measures of error processing are candidate biomarkers for externalizing disorders, albeit we strongly urge researchers to continue looking into the predictive value of these measures in the etiology and treatment outcome through multi-method and longitudinal designs.

Social and Nonsocial Reward Anticipation in Typical Development and Autism Spectrum Disorders: Current Status and Future Directions

PURPOSE OF REVIEW

While there has been sustained interest in understanding the role of reward processing in autism spectrum disorder (ASD), researchers are just beginning to focus on the anticipation phase of reward processing in this population. This review aimed to briefly summarize recent advancements in functional imaging studies of anticipatory social and nonsocial reward processing in individuals with and without ASD and provide suggestions for avenues of future research.

RECENT FINDINGS

Reward salience and activation of the complex network of brain regions supporting reward anticipation vary across development and by important demographic characteristics, such as sex assigned at birth. Current research comparing social and nonsocial reward anticipation may possess confounds related to the mismatch in tangibility and salience of social and nonsocial experimental stimuli. Growing evidence suggests individuals with ASD demonstrate aberrant generalized reward anticipation that is not specific to social reward. Future research should carefully match social and nonsocial reward stimuli and consider employing a longitudinal design to disentangle the complex processes contributing to the development of reward anticipation. It may be useful to conceptualize differences in reward anticipation as a transdiagnostic factor, rather than an ASD-specific deficit.

Electrophysiological investigation of reward anticipation and outcome evaluation during slot machine play

Slot machines are a popular form of gambling, offering a tractable way to experimentally model reward processes. This study used a 3-reel slot paradigm to assess psychologically distinct phases of reward processing, reflecting anticipation, and early- and late-stage outcome processing. EEG measures of winning, nearly missing (a losing outcome revealed at the final, third reel), and "totally" missing (a losing outcome revealed earlier, at the second reel) were collected from healthy adults (n=54). Condition effects were evaluated in: i) event-related potential (ERP) components reflecting anticipatory attention (stimulus preceding negativity, SPN) and outcome processing (reward positivity, RewP and late-positive potential, LPP) and ii) total power and phase synchrony of theta and delta band oscillations. Behaviorally, trial initiation was fastest after a near miss outcome and slowest after a winning outcome. As expected, a significant SPN was observed for possible wins (AA) vs. total misses (AB), consistent with reward anticipation. Larger win (AAA) vs. near miss (AAB) amplitudes were observed for the RewP; LPP amplitudes were largest for wins (AAA), intermediate for near misses (AAB), and smallest for total misses (ABC), reflecting significant early (RewP) and late-stage (LPP) outcome processing effects. There was an effect of reel position on the RewP, with larger amplitude in the final reel (AAA-AAB) relative to the 2^nd-reel locked difference waves (AA-AB). Across all outcomes, near misses elicited the largest and most phase-synchronized theta responses, while wins elicited larger and more phase-synchronized delta responses than total misses, with delta band measures not distinguishing between near misses and wins. . Phase locking measures contrasting win vs. near miss delta and theta synchronization, within time windows corresponding to ERP measurements, covaried with RewP, but not SPN or LPP, amplitude. Lastly, EEG measures showed differential relationships with age and self-reported consummatory pleasure. In the context of slot machine play, where reward anticipation and attainment place minimal demands on effort and skill, ERP and time-frequency methods capture distinct neurophysiological signatures of reward anticipation and outcome processing.

The influence of psychological and cognitive states on error-related negativity evoked during post-stroke rehabilitation movements

Background

Recently, error-related negativity (ERN) signals are proposed to develop an assist-as-needed robotic stroke rehabilitation program. Stroke patients’ state-of-mind, such as motivation to participate and active involvement in the rehabilitation program, affects their rate of recovery from motor disability. If the characteristics of the robotic stroke rehabilitation program can be altered based on the state-of-mind of the patients, such that the patients remain engaged in the program, the rate of recovery from their motor disability can be improved. However, before that, it is imperative to understand how the states-of-mind of a participant affect their ERN signal.

Methods

This study aimed to determine the association between the ERN signal and the psychological and cognitive states of the participants. Experiments were conducted on stroke patients, which involved performing a physical rehabilitation exercise and a questionnaire to measure participants' subjective experience on four factors: motivation in participating in the experiment, perceived effort, perceived pressure, awareness of uncompleted exercise trials while performing the rehabilitation exercise. Statistical correlation analysis, EEG time-series and topographical analysis were used to assess the association between the ERN signals and the psychological and cognitive states of the participants.

Results

A strong correlation between the amplitude of the ERN signal and the psychological and cognitive states of the participants was observed, which indicate the possibility of estimating the said states using the amplitudes of the novel ERN signal.

Conclusions

The findings pave the way for the development of an ERN based dynamically adaptive assist-as-needed robotic stroke rehabilitation program of which characteristics can be altered to keep the participants’ motivation, effort, engagement in the rehabilitation program high. In future, the single-trial prediction ability of the novel ERN signals to predict the state-of-mind of stroke patients will be evaluated.

The ERP, frequency, and time-frequency correlates of feedback processing: Insights from a large sample study

Human learning, at least in part, appears to be dependent on the evaluation of how outcomes of our actions align with our expectations. Over the past 23 years, electroencephalography (EEG) has been used to probe the neural signatures of feedback processing. Seminal work demonstrated a difference in the human event-related potential (ERP) dependent on whether people were processing correct or incorrect feedback. Since then, these feedback evoked ERPs have been associated with reinforcement learning and conflict monitoring, tied to subsequent behavioral adaptations, and shown to be sensitive to a wide range of factors (e.g., Parkinson's disease). Recently, research has turned to frequency decomposition techniques to examine how changes in the EEG power spectra are related to underlying learning mechanisms. Although the literature on the neural correlates of feedback processing is vast, there are still methodological discrepancies and differences in results across studies. Here, we provide reference results and an investigation of methodological considerations for the ERP (reward positivity) and frequency (delta and theta power) correlates of feedback evaluation with a large sample size. Specifically, participants (n = 500) performed a two-armed bandit task while we recorded EEG. Our findings provide key information about the data characteristics and relationships that exist between the neural signatures of feedback evaluation. Additionally, we conclude with selected methodological recommendations for standardization of future research. All data and scripts are freely provided to facilitate open science.

Reward processing electrophysiology in schizophrenia: Effects of age and illness phase

BACKGROUND

Reward processing abnormalities may underlie characteristic pleasure and motivational impairments in schizophrenia. Some neural measures of reward processing show age-related modulation, highlighting the importance of considering age effects on reward sensitivity. We compared event-related potentials (ERPs) reflecting reward anticipation (stimulus-preceding negativity, SPN) and evaluation (reward positivity, RewP; late positive potential, LPP) across individuals with schizophrenia (SZ) and healthy controls (HC), with an emphasis on examining the effects of chronological age, brain age (i.e., predicted age based on neurobiological measures), and illness phase.

METHODS

Subjects underwent EEG while completing a slot-machine task for which rewards were not dependent on performance accuracy, speed, or response preparation. Slot-machine task EEG responses were compared between 54 SZ and 54 HC individuals, ages 19 to 65. Reward-related ERPs were analyzed with respect to chronological age, categorically-defined illness phase (early; ESZ versus chronic schizophrenia; CSZ), and were used to model brain age relative to chronological age.

RESULTS

Illness phase-focused analyses indicated there were no group differences in average SPN or RewP amplitudes. However, a group × reward outcome interaction revealed that ESZ differed from HC in later outcome processing, reflected by greater LPP responses following loss versus reward (a reversal of the HC pattern). While brain age estimates did not differ among groups, depressive symptoms in SZ were associated with older brain age estimates while controlling for negative symptoms.

CONCLUSIONS

ESZ and CSZ did not differ from HC in reward anticipation or early outcome processing during a cognitively undemanding reward task, highlighting areas of preserved functioning. However, ESZ showed altered later reward outcome evaluation, pointing to selective reward deficits during the early illness phase of schizophrenia. Further, an association between ERP-derived brain age and depressive symptoms in SZ extends prior findings linking depression with reward-related ERP blunting. Taken together, both illness phase and age may impact reward processing among SZ, and brain aging may offer a promising, novel marker of reward dysfunction that warrants further study.

Time of day differences in neural reward responsiveness in children

The Reward Positivity (∆RewP) event-related potential (ERP), generally quantified as the difference between neural responsiveness to monetary gains (RewP-Gain) and losses (RewP-Loss) is commonly used as an index of neural reward responsiveness. Despite the popularity of this ERP component in studies of reward processing, knowledge about the role of state-related influences on the ∆RewP is limited. The present study examined whether ∆RewP amplitudes may differ based on when during the day they are assessed and whether age or sex would moderate this link. Participants were 188 children between the ages of 7 and 11 (47.3% female) without a lifetime history of a major depressive disorder or any anxiety disorder recruited from the community. Children completed the Doors task during which continuous electroencephalography was recorded to isolate the ∆RewP. To better isolate this ERP component from other temporally or spatially overlapping ERPs, we used temporospatial principal component analysis. We found that time of day (ToD) differences in the ∆RewP amplitude varied based on children's age. Specifically, older, compared to younger, children exhibited stronger responses to gains versus losses between 11:15 a.m. and 12:30 p.m. and after around 5:15 p.m. Further, these age-related differences appeared to be driven specifically by older children's reduced neural responsiveness to losses. The findings have methodological implications by highlighting the importance of accounting for the ToD at which ∆RewP-focused study sessions are conducted as well as for demographic characteristics of the participants, such as their age.