Relationship between oscillatory neuronal activity during reward processing and trait impulsivity and sensation seeking

The neural correlates of reinforcement sensitivity theory: A systematic review of the frontal asymmetry and spectral power literature

The original Reinforcement Sensitivity Theory (oRST) proposes two systems of approach (BAS) and avoidance (BIS) motivation to underpin personality and behavior. The revised-RST (rRST) model separates avoidance motivation into passive (BIS; anxiety) and active (FFFS; fear) systems. Prior research has attempted to map RST onto lateralized frontal asymmetry to provide a neurophysiological marker of RST. The main aim is to examine the relationships of the o/rRST scales with trait (baseline) and state (manipulated through experimental paradigms) frontal asymmetry. A systematic review was conducted, resulting in 158 studies designated to neuroimaging research. In total, 54 studies were included in this review using either frontal asymmetry or spectral power. The results were split into three main categories: resting frontal alpha asymmetry (N = 23), emotional induction and state-related frontal alpha asymmetry (N = 20), and spectral analysis (N = 16). Findings indicated that BAS was associated with enhanced left frontal asymmetry at baseline and during state-related paradigms. Findings for BIS were more inconsistent, especially at rest, suggesting that BIS, in particular, may require active engagement with the environment. Only 9 of the 54 papers included used the revised RST model, highlighting the need for more rRST research.

Neural correlates of evaluations of non-binary social feedback: An EEG study

PURPOSE

In complex and diverse social circumstances, decision making is affected by social feedback. Although previous studies have examined the electrophysiological correlates of social feedback with a binary valence, those related to non-binary feedback, or the magnitude of social feedback, remain unclear. This study investigated the electrophysiological correlates of non-binary social feedback and subsequent action selection processing.

METHODS

Participants were asked to complete a Gabor patch direction judgment task in which they were required to make judgments before and after receiving social feedback. They were informed that the feedback stimuli represented the degree to which other participants made the same choice.

RESULTS & CONCLUSION

The results revealed that feedback that was highly concordant with the participant's judgments elicited greater P300 activity, which was associated with the fulfillment of expectations regarding social reward. Moreover, moderately concordant feedback induced stronger theta band power, which may indicate monitoring of subjective conflict. Temporal changes in theta power during feedback phase may also relate to adjustments in prediction error. Additionally, when an initial judgment was maintained following social feedback, we observed a stronger increase in beta power, indicating an association with post-social-feedback action processing.

Losses resulting from deliberate exploration trigger beta oscillations in frontal cortex

We examined the neural signature of directed exploration by contrasting MEG beta (16-30 Hz) power changes between disadvantageous and advantageous choices in the two-choice probabilistic reward task. We analyzed the choices made after the participants have learned the probabilistic contingency between choices and their outcomes, i.e., acquired the inner model of choice values. Therefore, rare disadvantageous choices might serve explorative, environment-probing purposes. The study brought two main findings. Firstly, decision making leading to disadvantageous choices took more time and evidenced greater large-scale suppression of beta oscillations than its advantageous alternative. Additional neural resources recruited during disadvantageous decisions strongly suggest their deliberately explorative nature. Secondly, an outcome of disadvantageous and advantageous choices had qualitatively different impact on feedback-related beta oscillations. After the disadvantageous choices, only losses-but not gains-were followed by late beta synchronization in frontal cortex. Our results are consistent with the role of frontal beta oscillations in the stabilization of neural representations for selected behavioral rule when explorative strategy conflicts with value-based behavior. Punishment for explorative choice being congruent with its low value in the reward history is more likely to strengthen, through punishment-related beta oscillations, the representation of exploitative choices consistent with the inner utility model.

High-Definition Transcranial Direct Current Stimulation Improves Decision-Making Ability: A Study Based on EEG

High-definition transcranial direct current stimulation (HD-tDCS) has been shown to modulate decision-making; however, the neurophysiological mechanisms underlying this effect remain unclear. To further explore the neurophysiological processes of decision-making modulated by HD-tDCS, health participants underwent ten anodal (n = 16)/sham (n = 17) HD-tDCS sessions targeting the left DLPFC. Iowa gambling task was performed simultaneously with electroencephalography (EEG) before and after HD-tDCS. Iowa gambling task performance, the P300 amplitude, and the power of theta oscillation as an index of decision-making were compared. Behavioral changes were found that showed anodal HD-tDCS could improve the decision-making function, in which participants could make more advantageous choices. The electrophysiological results showed that the P300 amplitude significantly increased in CZ, CPZ electrode placement site and theta oscillation power significantly activated in FCZ, CZ electrode placement site after anodal HD-tDCS. Significant positive correlations were observed between the changes in the percent use of negative feedback and the changes in theta oscillation power before and after anodal HD-tDCS. This study showed that HD-tDCS is a promising technology in improving decision-making and theta oscillation induced by may be a predictor of improved decision-making.

Intertemporal Decision-making and Risk Decision-making Among Habitual Nappers Under Nap Sleep Restriction: A Study from ERP and Time-frequency

Sleep restriction affects people's decision-making behavior. Nap restriction is a vital subtopic within sleep restriction research. In this study, we used EEG to investigate the impact of nap sleep restriction on intertemporal decision-making (Study 1) and decision-making across risky outcomes (Study 2) from ERP and time-frequency perspectives. Study 1 found that habitual nappers restricting their naps felt more inclined to choose immediate, small rewards over delayed, large rewards in an intertemporal decision-making task. P200s, P300s, and LPP in our nap-restriction group were significantly higher than those in the normal nap group. Time-frequency results showed that the delta band (1 ~ 4 Hz) power of the restricted nap group was significantly higher than that of the normal nap group. In Study 2, the nap-restriction group was more likely to choose risky options. P200s, N2s, and P300s in the nap deprivation group were significantly higher than in the normal nap group. Time-frequency results also found that the beta band (11 ~ 15 Hz) power of the restricted nap group was significantly lower than that of the normal nap group. The habitual nappers became more impulsive after nap restriction and evinced altered perceptions of time. The time cost of the LL (larger-later) option was perceived to be too high when making intertemporal decisions, and their expectation of reward heightened when making risky decisions-believing that they had a higher probability of receiving a reward. This study provided electrophysiological evidence for the dynamic processing of intertemporal decision-making, risky decision-making, and the characteristics of nerve concussions for habitual nappers.

Expectations of immediate and delayed reward differentially affect cognitive task performance

The current study used a modified Monetary Incentive Delay task to examine the neural mechanisms underlying anticipating and receiving an immediate or delayed reward and examined the influence of pursuing these rewards on cognitive task performance. A pre-cue indicating the potential of gaining a monetary reward (immediate-, delayed-, vs. no-reward) was followed by a target stimulus requiring a fast and accurate response. Then, response-contingent feedback was presented indicating whether or not the participant would receive the corresponding reward. Linear mixed-effect models revealed the fastest behavioural responses and the strongest neural activity, as reflected in event-related-potentials and event-related-spectral-perturbation responses, for immediate reward, followed by delayed reward, with the slowest behavioural responses and the weakest neural activities observed in the no-reward condition. Expectations related to the cue-P3 component and the cue-delta activities predicted behavioural performance, especially in the immediate reward condition. Moreover, exploratory analyses revealed that depression moderated the relationship between target-locked neural activity and behavioural performance in the delayed reward condition, with lower neural activity being related to worse behavioural performance amongst participants scoring high on depression. These results indicate that differential value representations formed through delay discounting directly affect neural responses in reward processing and directly influence the effort invested in the current task, which is reflected by behavioural responses and is in agreement with the expected value of control theory.

Trait sensation seeking is associated with heightened beta-band oscillatory dynamics over left ventrolateral prefrontal cortex during reward expectancy

BACKGROUND

Sensation Seeking, the proclivity toward novel and stimulating experiences, is associated with greater left ventrolateral prefrontal cortex (vlPFC) activity during uncertain reward expectancy. Here, we examined relationships between sensation seeking and vlPFC oscillatory dynamics using electroencephalography (EEG).

METHODS

In 26 adolescents/young adults (16 female; 22.3 ± 1.7yrs), EEG was measured during uncertain reward expectancy. Event-related spectral perturbations (ERSP) from 15-80 Hz (beta/gamma bands) were compared as a function of uncertain reward expected value and assessed for relationships with feedback-related negativity (FRN) response to outcome feedback and response tendency measures of risk for BD.

RESULTS

Event-related synchronization (ERS) between 15-25 Hz (beta) over left vlPFC was sensitive to the expected value of uncertain reward (rho=0.46; p = 0.048), and correlated with sensation seeking (r = 0.49, p < 0.01) and feedback-related negativity (FRN), where greater beta ERS was related to larger FRN (r = -0.39, p = 0.047). FRN was also related to behavioral inhibition (r = 0.49, p < 0.01).

LIMITATIONS

It is unknown whether results may extrapolate to clinical populations, given the healthy sample used here. Further, although we have confidence that the beta-band signal we measure in this study arises from left prefrontal cortex, we largely infer a left vlPFC source.

CONCLUSIONS

These findings highlight the role of left vlPFC in evaluation of immediate rewards. We now provide a link between reward expectancy-related left vlPFC activity and the well-characterized FRN, with a known role in attentive processing. These findings can guide treatment development for mania/hypomania at-risk individuals, including transcranial alternating current stimulation.

Simultaneous EEG-fMRI reveals theta network alterations during reward feedback processing in borderline personality disorder

Previous studies using imaging techniques such as electroencephalography (EEG) or functional magnetic resonance imaging (fMRI) have identified neurophysiological markers of impaired feedback processing in patients with Borderline Personality Disorder (BPD). These mainly include reduced oscillatory activity in the theta frequency range in the EEG and altered activations in frontal and striatal regions in fMRI studies. The aim of the present study is to integrate these results using a coupling of simultaneously recorded EEG and fMRI. Simultaneous EEG (64-channel) and fMRI (3-Tesla Siemens Prisma) was recorded whilst participants (19 BPD patients and 18 controls) performed a gambling task. Data was analysed for the two imaging techniques separately as well as in a single-trial coupling of both modalities. Evoked theta oscillatory power as a response to loss feedback was reduced in BPD patients. EEG-fMRI coupling revealed an interaction between feedback valence and group in prefrontal regions centering in the dorsolateral prefrontal cortex (dlPFC), with healthy controls showing stronger modulation by theta responses during loss when compared to gain feedback and the opposite effect in BPD patients. Our results show multiple alterations in the processing of feedback in BPD, which were partly linked to impulsivity. The dlPFC was identified as the seed of theta-associated activation differences.

Alterations of oscillatory neuronal activity during reward processing in schizophrenia

OBJECTIVES

Reward system dysfunctions are considered to be a pathophysiological mechanism in schizophrenia. Electrophysiological studies of reward system functions have identified frequency-specific brain networks for the processing of positive (high-beta frequency) and negative (theta frequency) events. Remarkably, midbrain dopaminergic signalling also includes theta and high-beta frequency modes, which have been assumed to reflect tonic and phasic dopamine responses, respectively. The aim of the present study was to identify alterations of oscillatory responses to reward feedback in patients with schizophrenia.

METHODS

Seventeen patients with schizophrenia and 18 healthy controls performed a gambling task during recording of 64-channel electroencephalography. The theta and high-beta band total power were investigated in response to feedback events depending on feedback valence (loss or gain) and magnitude (5 vs. 25 points).

RESULTS

Both the increase of theta oscillatory activity in response to loss feedback (compared to gain feedback) and the increase of high-beta oscillatory activity in response to gain feedback (compared to loss feedback) were reduced in patients. The difference in high-beta responses to gain versus loss feedback in patients was associated with the severity of negative symptoms.

CONCLUSIONS

Our findings are consistent with current models of reward system dysfunction in schizophrenia, and indicate deficits in both cortical tonic and subcortical phasic dopamine activity, consistent with the complex dopaminergic abnormalities in schizophrenia.

An insight-related neural reward signal

Moments of insight, a phenomenon of creative cognition in which an idea suddenly emerges into awareness as an "Aha!" are often reported to be affectively positive experiences. We tested the hypothesis that problem-solving by insight is accompanied by neural reward processing. We recorded high-density EEGs while participants solved a series of anagrams. For each solution, they reported whether the answer had occurred to them as a sudden insight or whether they had derived it deliberately and incrementally (i.e., "analytically'). Afterwards, they filled out a questionnaire that measures general dispositional reward sensitivity. We computed the time-frequency representations of the EEGs for trials with insight (I) solutions and trials with analytic (A) solutions and subtracted them to obtain an I-A time-frequency representation for each electrode. Statistical Parametric Mapping (SPM) analyses tested for significant I-A and reward-sensitivity effects. SPM revealed the time, frequency, and scalp locations of several I ​> ​A effects. No A ​> ​I effect was observed. The primary neural correlate of insight was a burst of (I ​> ​A) gamma-band oscillatory activity over prefrontal cortex approximately 500 ​ms before participants pressed a button to indicate that they had solved the problem. We correlated the I-A time-frequency representation with reward sensitivity to discover insight-related effects that were modulated by reward sensitivity. This revealed a separate anterior prefrontal burst of gamma-band activity, approximately 100 ​ms after the primary I-A insight effect, which we interpreted to be an insight-related reward signal. This interpretation was supported by source reconstruction showing that this signal was generated in part by orbitofrontal cortex, a region associated with reward learning and hedonically pleasurable experiences such as food, positive social experiences, addictive drugs, and orgasm. These findings support the notion that for many people insight is rewarding. Additionally, these results may explain why many people choose to engage in insight-generating recreational and vocational activities such as solving puzzles, reading murder mysteries, creating inventions, or doing research. This insight-related reward signal may be a manifestation of an evolutionarily adaptive mechanism for the reinforcement of exploration, problem solving, and creative cognition.

Synchronization of Independent Neural Ensembles in Human EEG during Choice Tasks

During behavioral experiments, humans placed in a situation of having to choose between a more valuable but risky reward and a less valuable but guaranteed reward make their decisions in accordance with external situational factors and individual characteristics, such as inclination to risk or caution. In such situations, humans can be divided into “risk-inclined” and “risk-averse” (or “cautious”) subjects. In this work, characteristics of EEG rhythms, such as phase–phase relationships and time lags between rhythms, were studied in pairs of alpha–beta and theta–beta rhythms. Phase difference can also be expressed as a time lag. It has been suggested that statistically significant time lags between rhythms are due to the combined neural activity of anatomically separate, independent (in activation/inhibition processes) ensembles. The extents of synchronicity between rhythms were compared as percentages between risk-inclined and risk-averse subjects. The results showed that synchronicity in response to stimuli was more often observed in pairs of alpha–beta rhythms of risk-averse subjects compared with risk-inclined subjects during the choice of a more valuable but less probable reward. In addition, significant differences in the percentage ratio of alpha and beta rhythms were revealed between (i) cases of synchronization without long time lags and (ii) cases with long time lags between rhythms (from 0.08 to 0.1 s).

Decision- and feedback-related brain potentials reveal risk processing mechanisms in patients with alcohol use disorder

Individuals with alcohol use disorder (AUD) are aware of the risks of alcohol abuse yet continue risky drinking. Research indicates that dysfunctional decision processes and trait variables such as impulsivity contribute to this awareness-behavior discrepancy. The present study focused on decision-related versus feedback-related processes as potential contributors to decision making in AUD by examining the relationship between decision choices and decision- and feedback-related ERP phenomena in the balloon analogue risk task (BART). N = 39 AUD and n = 35 healthy comparison participants (HC) performed the BART modified for EEG assessment. In each of 100 runs, participants made a series of choices about whether to pump up a virtual balloon, which popped pseudorandomly, ending the run. Alternatively, participants ended the run by pressing a "cash-out" button. Each pump not producing a pop provided .05 €; popping resulted in loss of the run's accumulated gain. Groups made similar choices, though AUD responded more slowly. The decision P3 200-400 ms after decision prompt (balloon) was larger in AUD than in HC, and decision P3 enhancement on high-risk trials predicted choices to pump. Feedback-related negativity (FRN) after loss (relative to cash out) feedback was smaller in AUD than in HC, suggesting indifference to negative feedback. In AUD, high impulsivity was associated with risk-modulated decision P3 but not FRN. Results indicate atypical decision- and feedback-related processes that could contribute to difficulties in engaging with daily challenges effectively.

Oscillatory Dynamics of Feedback Processing in Adolescents with Prenatal Cocaine Exposure

Prenatal cocaine exposure (PCE) has ramifications for feedback processing. Measuring neural oscillatory dynamics (during electroencephalography) provides insight into the time signatures and neural processes of feedback processing in adolescents with PCE. We measured spectral power in alpha and theta frequency bands while 49 adolescents with PCE and 34 non-drug exposed (NDE) performed a task with win/no-win feedback. Compared to NDE individuals, those with PCE showed reduced alpha power and increased theta power in response to no-win feedback. These findings suggest altered reactivity in PCE adolescents.

Internal cost of spontaneous deception revealed by ERPs and EEG spectral perturbations

Abundant literature has studied the behavioral and neural correlates of deception, but little research has focused on the internal cost of spontaneous deception. In the present study, the event-related potential and event-related spectral perturbations techniques were used to measure the internal cost of spontaneous deception by having participants perform a sender–receiver task in which they decided whether to send deceptive messages to increase their payoff from the task. Several important main findings emerged from this study. We observed a reward positivity (RewP) after senders sent the message, suggesting an integration of reward with associated cost after response in our task. Furthermore, spontaneous deception decreased the amplitude of the RewP and power in the delta and beta bands, whereas it increased the amplitude of power in the theta band, indicating that deception carried an internal cost that devalued individuals’ rewards.

Altered Oscillatory Responses to Feedback in Borderline Personality Disorder are Linked to Symptom Severity

Several studies using electroencephalography (EEG) demonstrate that the processing of feedback in patients suffering from borderline personality disorder (BPD) is altered in comparison to healthy controls. Differences occur in the theta (ca. 5 Hz) and high-beta frequency-ranges (ca. 20 Hz) of oscillations in response to negative and positive feedback, respectively. However, alpha (ca. 10 Hz) and low-beta (ca. 15 Hz) oscillations have also been shown to be involved in feedback processing. We hypothesized that additional alterations might occur in these frequency ranges in BPD. Eighteen patients with BPD and twenty-two healthy controls performed a gambling task while 64-channel-EEG was recorded. Induced oscillatory responses to positive (i.e. gain) and negative (i.e. loss) feedback in the alpha and low-beta frequency range were investigated. No significant differences were found in the alpha frequency range. Regarding the low-beta frequency range a significant Group (i.e. BPD vs. healthy controls) × Valence (i.e. gain vs. loss) interaction in the time frame between 600 and 700 milliseconds after feedback was found. This effect showed a significant correlation with symptom severity (assessed with the BSL-23). The results indicate that feedback processing in BPD could be more heavily altered than previously expected, with more severe symptomatology being linked to stronger alterations in oscillatory responses to feedback in the low-beta range.

Power of Feedback-Induced Beta Oscillations Reflect Omission of Rewards: Evidence From an EEG Gambling Study

The functional role of high beta oscillations (20–35 Hz) during feedback processing has been suggested to reflect unexpected gains. Using a novel gambling task that separates gains and losses across blocks and directly compares reception of monetary rewards to a ‘no-reward/punishment’ condition with equal probability we aimed to further investigate the role of beta oscillations. When contrasting different feedback conditions across rewards, we found that a late low beta component (12–20 Hz) had increased in power during the omission of rewards relative to the reception of rewards, while no differences were observed during the loss domain. These findings may indicate that late low beta oscillations in the context of feedback processing may respond to omission of gains relative to other potential outcomes. We speculate that late low beta oscillations may operate as a learning mechanism that signals the brain to make future adequate decisions. Overall, our study provides new insights for the role of late low beta oscillations in reward processing.

Event-Related Potentials in Relation to Risk-Taking: A Systematic Review

Event-related potentials (ERPs) have been used to investigate neural mechanisms underlying risk-related decisions over the last 16 years. We aimed to systematically evaluate associations between risk-taking and ERP components elicited during decisions and following feedback. A total of 79 articles identified from PsychINFO and PubMed databases met the inclusion criteria. Selected articles assessed early ERP components (feedback-related negativity/FRN, error-related negativity/ERN, and medial frontal negativity/MFN) and the mid-latency P3 component, all using gambling paradigms that involved selecting between choices of varying risk (e.g., Iowa Gambling Task, Balloon Analogue Risk Task, and two-choice gambling tasks). The P3 component was consistently enhanced to the selection of risky options and when positive feedback (as compared to negative feedback) was provided. Also consistently, the early negative components were found to be larger following feedback indicating monetary losses as compared to gains. In the majority of studies reviewed here, risk was conceptualized in the context of simple economical decisions in gambling tasks. As such, this narrow concept of risk might not capture the diversity of risky decisions made in other areas of everyday experience, for example, social, health, and recreational risk-related decisions. It therefore remains to be seen whether the risk-sensitivity of the ERP components reviewed here generalizes to other domains of life.

Stress Elevates Frontal Midline Theta in Feedback-based Category Learning of Exceptions

Adapting behavior based on category knowledge is a fundamental cognitive function, which can be achieved via different learning strategies relying on different systems in the brain. Whereas the learning of typical category members has been linked to implicit, prototype abstraction learning, which relies predominantly on prefrontal areas, the learning of exceptions is associated with explicit, exemplar-based learning, which has been linked to the hippocampus. Stress is known to foster implicit learning strategies at the expense of explicit learning. Procedural, prefrontal learning and cognitive control processes are reflected in frontal midline theta (4–8 Hz) oscillations during feedback processing. In the current study, we examined the effect of acute stress on feedback-based category learning of typical category members and exceptions and the oscillatory correlates of feedback processing in the EEG. A computational modeling procedure was applied to estimate the use of abstraction and exemplar strategies during category learning. We tested healthy, male participants who underwent either the socially evaluated cold pressor test or a nonstressful control procedure before they learned to categorize typical members and exceptions based on feedback. The groups did not differ significantly in their categorization accuracy or use of categorization strategies. In the EEG, however, stressed participants revealed elevated theta power specifically during the learning of exceptions, whereas the theta power during the learning of typical members did not differ between the groups. Elevated frontal theta power may reflect an increased involvement of medial prefrontal areas in the learning of exceptions under stress.

Oscillatory rhythm of reward: anticipation and processing of rewards in children with and without autism

Background

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition, and multiple theories have emerged concerning core social deficits. While the social motivation hypothesis proposes that deficits in the social reward system cause individuals with ASD to engage less in social interaction, the overly intense world hypothesis (sensory over-responsivity) proposes that individuals with ASD find stimuli to be too intense and may have hypersensitivity to social interaction, leading them to avoid these interactions.

Methods

EEG was recorded during reward anticipation and reward processing. Reward anticipation was measured using alpha asymmetry, and post-feedback theta was utilized to measure reward processing. Additionally, we calculated post-feedback alpha suppression to measure attention and salience. Participants were 6- to 8-year-olds with (N = 20) and without (N = 23) ASD.

Results

Children with ASD showed more left-dominant alpha suppression when anticipating rewards accompanied by nonsocial stimuli compared to social stimuli. During reward processing, children with ASD had less theta activity than typically developing (TD) children. Alpha activity after feedback showed the opposite pattern: children with ASD had greater alpha suppression than TD children. Significant correlations were observed between behavioral measures of autism severity and EEG activity in both the reward anticipation and reward processing time periods.

Conclusions

The findings provide evidence that children with ASD have greater approach motivation prior to nonsocial (compared to social) stimuli. Results after feedback suggest that children with ASD evidence less robust activity thought to reflect evaluation and processing of rewards (e.g., theta) compared to TD children. However, children with ASD evidence greater alpha suppression after feedback compared to TD children. We hypothesize that post-feedback alpha suppression reflects general cognitive engagement-which suggests that children with ASD may experience feedback as overly intense. Taken together, these results suggest that aspects of both the social motivation hypothesis and the overly intense world hypothesis may be occurring simultaneously.

Theta and high-beta networks for feedback processing: a simultaneous EEG-fMRI study in healthy male subjects

The reward system is important in assessing outcomes to guide behavior. To achieve these purposes, its core components interact with several brain areas involved in cognitive and emotional processing. A key mechanism suggested to subserve these interactions is oscillatory activity, with a prominent role of theta and high-beta oscillations. The present study used single-trial coupling of simultaneously recorded electroencephalography and functional magnetic resonance imaging data to investigate networks associated with oscillatory responses to feedback during a two-choice gambling task in healthy male participants (n=19). Differential associations of theta and high-beta oscillations with non-overlapping brain networks were observed: Increase of high-beta power in response to positive feedback was associated with activations in a largely subcortical network encompassing core areas of the reward network. In contrast, theta-band power increase upon loss was associated with activations in a frontoparietal network that included the anterior cingulate cortex. Trait impulsivity correlated significantly with activations in areas of the theta-associated network. Our results suggest that positive and negative feedback is processed by separate brain networks associated with different cognitive functions. Communication within these networks is mediated by oscillations of different frequency, possibly reflecting different modes of dopaminergic signaling.

EEG to Primary Rewards: Predictive Utility and Malleability by Brain Stimulation

Theta burst stimulation (TBS) is thought to affect reward processing mechanisms, which may increase and decrease reward sensitivity. To test the ability of TBS to modulate response to strong primary rewards, participants hypersensitive to primary rewards were recruited. Twenty men and women with at least two opposite-sex, sexual partners in the last year received two forms of TBS. Stimulations were randomized to avoid order effects and separated by 2 hours to reduce carryover. The two TBS forms have been demonstrated to inhibit (continuous) or excite (intermittent) the left dorsolateral prefrontal cortex using different pulse patterns, which links to brain areas associated with reward conditioning. After each TBS, participants completed tasks assessing their reward responsiveness to monetary and sexual rewards. Electroencephalography (EEG) was recorded. They also reported their number of orgasms in the weekend following stimulation. This signal was malleable by TBS, where excitatory TBS resulted in lower EEG alpha relative to inhibitory TBS to primary rewards. EEG responses to sexual rewards in the lab (following both forms of TBS) predicted the number of orgasms experienced over the forthcoming weekend. TBS may be useful in modifying hypersensitivity or hyposensitivity to primary rewards that predict sexual behaviors. Since TBS altered the anticipation of a sexual reward, TBS may offer a novel treatment for sexual desire problems.

Willing to wait: Elevated reward-processing EEG activity associated with a greater preference for larger-but-delayed rewards

While almost everyone discounts the value of future rewards over immediate rewards, people differ in their so-called delay-discounting. One of the several factors that may explain individual differences in delay-discounting is reward-processing. To study individual-differences in reward-processing, however, one needs to consider the heterogeneity of neural-activity at each reward-processing stage. Here using EEG, we separated reward-related neural activity into distinct reward-anticipation and reward-outcome stages using time-frequency characteristics. Thirty-seven individuals first completed a behavioral delay-discounting task. Then reward-processing EEG activity was assessed using a separate reward-learning task, called a reward time-estimation task. During this EEG task, participants were instructed to estimate time duration and were provided performance feedback on a trial-by-trial basis. Participants received monetary-reward for accurate-performance on Reward trials, but not on No-Reward trials. Reward trials, relative to No-Reward trials, enhanced EEG activity during both reward-anticipation (including, cued-locked delta power during cue-evaluation and pre-feedback alpha suppression during feedback-anticipation) and reward-outcome (including, feedback-locked delta, theta and beta power) stages. Moreover, all of these EEG indices correlated with behavioral performance in the time-estimation task, suggesting their essential roles in learning and adjusting performance to maximize winnings in a reward-learning situation. Importantly, enhanced EEG power during Reward trials, as reflected by stronger 1) pre-feedback alpha suppression, 2) feedback-locked theta and 3) feedback-locked beta, was associated with a greater preference for larger-but-delayed rewards in a separate, behavioral delay-discounting task. Results highlight the association between a stronger preference toward larger-but-delayed rewards and enhanced reward-processing. Moreover, our reward-processing EEG indices detail the specific stages of reward-processing where these associations occur.

Oscillatory responses to reward processing in borderline personality disorder

OBJECTIVES

Previous electrophysiological studies have confirmed impaired reward processing in patients with BPD. However, it is not clear which aspects of reward processing are affected and which brain regions are involved. The present study investigated both evoked and induced event-related oscillations (EROs) to feedback events (thought to represent different aspects of feedback processing), and used source localization (sLORETA) to assess activity in two areas known to contribute to reward processing, the dorsomedial prefrontal/anterior cingulate cortex (dmPFC/ACC) and the orbitofrontal cortex (OFC).

METHODS

Eighteen patients with BPD and 22 healthy controls performed a gambling task, while 64-channel electroencephalographic activity was recorded. Evoked and induced theta and high-beta band EROs as well as activity in the two regions of interest were investigated depending on the valence and magnitude of feedback events.

RESULTS

Theta-band responses to negative feedback were reduced in BPD, an effect that involved only evoked responses and the dmPFC/ ACC region, and was associated with trait impulsivity in patients. sLORETA analyses revealed disturbed evoked responses depending on feedback magnitude in the theta (OFC) and high-beta (dmPFC/ACC and OFC) frequency range.

CONCLUSIONS

The results indicate multiple dysfunctions of feedback processing in patients with BPD, implicating several distinct subsets of reward-processing mechanisms.

The Subthalamic Nucleus, Limbic Function, and Impulse Control

It has been well documented that deep brain stimulation (DBS) of the subthalamic nucleus (STN) to address some of the disabling motor symptoms of Parkinson's disease (PD) can evoke unintended effects, especially on non-motor behavior. This observation has catalyzed more than a decade of research concentrated on establishing trends and identifying potential mechanisms for these non-motor effects. While many issues remain unresolved, the collective result of many research studies and clinical observations has been a general recognition of the role of the STN in mediating limbic function. In particular, the STN has been implicated in impulse control and the related construct of valence processing. A better understanding of STN involvement in these phenomena could have important implications for treating impulse control disorders (ICDs). ICDs affect up to 40% of PD patients on dopamine agonist therapy and approximately 15% of PD patients overall. ICDs have been reported to be associated with STN DBS. In this paper we will focus on impulse control and review pre-clinical, clinical, behavioral, imaging, and electrophysiological studies pertaining to the limbic function of the STN.

Human oscillatory activity in near-miss events

Near-miss events are situations in which an action yields a negative result but is very close to being successful. They are known to influence behavior, especially in gambling scenarios. Previous neuroimaging studies have described an 'anomalous' activity of brain reward areas following these events. The goal of the present research was to study electrophysiological correlates of near-misses in the expectation and outcome phases. Electroencephalography was recorded while participants were playing a simplified version of a slot machine. Four possible outcomes (gain, near-miss, loss and no-information) were presented in a pseudorandom order to ensure fixed proportions. Results from the time-frequency analysis for the theta (4-8 Hz), alpha (9-13 Hz), low beta (15-22 Hz) and beta-gamma (25-35 Hz) frequency-bands presented larger power increases for wins and near-misses compared with losses. In the anticipation phase, power changes were lower than in the resolution phase. The current results are in agreement with previous studies showing that near-miss events recruit brain areas of the reward network. Likewise, the oscillatory activity in near-misses is very similar to the one elicited in the gain condition. In addition, present findings suggest that oscillatory activity in the expectation phase does not play a crucial role in near-miss events.

Resting-state theta-band connectivity and verbal memory in schizophrenia and in the high-risk state

BACKGROUND

Disturbed functional connectivity is assumed to underlie neurocognitive deficits in patients with schizophrenia. As neurocognitive deficits are already present in the high-risk state, identification of the neural networks involved in this core feature of schizophrenia is essential to our understanding of the disorder. Resting-state studies enable such investigations, while at the same time avoiding the known confounder of impaired task performance in patients. The aim of the present study was to investigate EEG resting-state connectivity in high-risk individuals (HR) compared to first episode patients with schizophrenia (SZ) and to healthy controls (HC), and its association with cognitive deficits.

METHODS

64-channel resting-state EEG recordings (eyes closed) were obtained for 28 HR, 19 stable SZ, and 23 HC, matched for age, education, and parental education. The imaginary coherence-based multivariate interaction measure (MIM) was used as a measure of connectivity across 80 cortical regions and six frequency bands. Mean connectivity at each region was compared across groups using the non-parametric randomization approach. Additionally, the network-based statistic was applied to identify affected networks in patients.

RESULTS

SZ displayed increased theta-band resting-state MIM connectivity across midline, sensorimotor, orbitofrontal regions and the left temporoparietal junction. HR displayed intermediate theta-band connectivity patterns that did not differ from either SZ or HC. Mean theta-band connectivity within the above network partially mediated verbal memory deficits in SZ and HR.

CONCLUSIONS

Aberrant theta-band connectivity may represent a trait characteristic of schizophrenia associated with neurocognitive deficits. As such, it might constitute a promising target for novel treatment applications.