A comparison of reward processing during Becker-DeGroot-Marschak and Vickrey auctions: An ERP study

Vickrey auctions (VA) and Becker-DeGroot-Marschak auctions (BDM) are strategically equivalent demand-revealing mechanisms, differentiated only by a human opponent in the VA, and a random-number-generator opponent in the BDM. Game parameters are such that players are incentivized to reveal their private subjective values (SV) and behavior should be identical in both tasks. However, this has been repeatedly shown not to be the case. In this study, the neural correlates of outcome feedback processing during VA and BDM were directly compared using electroencephalography. Twenty-eight healthy participants bid for household products which were then divided into high- and low-SV categories. The VA included a human opponent deception to induce a social environment, while in reality a random-number-generator was used in both tasks. A P3 component peaking at 336 ms over midline parietal sites showed more positive amplitudes for high bid values, and for win outcomes in the VA but not the BDM. Both auctions also elicited a Reward Positivity potential, maximal at 275 ms along the central midline electrodes, that was not modulated by auction task or SV. Further, an exploratory N170 potential in the right occipitotemporal electrodes and a vertex positive potential component were stronger in the VA relative to the BDM. Results point to an enhanced cortical response to bid outcomes during VA task in a potential component associated with emotional control, and to the occurrence of face-sensitive potentials in VA but not in BDM auction. These findings suggest modulation of bid outcome processing by the social-competitive aspect of auction tasks. Directly comparing two prominent auction paradigms affords the opportunity to isolate the impact of social environment on competitive, risky decision-making. Findings suggest that feedback processing as early as 176 ms is facilitated by the presence of a human competitor, and later processing is modulated by social context and subjective value.

Altered theta oscillations in resting EEG of fibromyalgia syndrome patients

Background

Fibromyalgia syndrome (FM) is a chronic pain disorder characterized by widespread pain, sleep disturbance, fatigue and cognitive/affective symptoms. Functional imaging studies have revealed that FM and other chronic pain syndromes can affect resting brain activity. This study utilized electroencephalographic (EEG) recordings to investigate the relative power of ongoing oscillatory activity in the resting brain.

Methods

A 64‐channel EEG was recorded at rest in 19 female FM patients and 18 healthy, age‐matched, control subjects. The Manual Tender Point Scale (MTPS) examination was performed to quantify tonic pain and tenderness on the day of testing along with measures of mood, arousal and fatigue. Oscillations in delta, theta, alpha, beta and gamma frequency bands were analysed using Standardised Low‐Resolution Brain Electromagnetic Tomography to evaluate sources of spectral activity throughout the whole brain.

Results

FM patients exhibited greater pain, tiredness and tension on the day of testing relative to healthy control participants and augmented theta activity in prefrontal and anterior cingulate cortices. No significant differences were seen in other frequency bands. Augmented frontal theta activity in FM patients significantly correlated with measures of tenderness and mean tiredness scores.

Conclusions

The findings indicate that alterations to resting‐state oscillatory activity may relate to ongoing tonic pain and fatigue in FM, and manifest in brain regions relevant for cognitive‐attentional aspects of pain processing and endogenous pain inhibition. Enhanced low‐frequency oscillations were previously seen in FM and other chronic pain syndromes, and may relate to pathophysiological mechanisms for ongoing pain such as thalamocortical dysrhythmia.

Significance

Increased prefrontal theta activity may contribute to persistent pain in fibromyalgia or represent the outcome of prolonged symptoms. The findings point to the potential for therapeutic interventions aimed at normalizing neural oscillations, while further research utilizing quantitative analysis of resting EEG could benefit our understanding of fibromyalgia pathophysiology.

Modulation of pain by emotional sounds: a laser-evoked potential study

BACKGROUND

Previous studies have shown increases in experimental pain during induction of a negative emotion with visual stimuli, verbal statements or unpleasant odours. The goal of the present study was to analyse the spatio-temporal activation patterns underlying pain augmentation during negative emotional sounds.

METHODS

Negative (e.g., crying), positive (e.g., laughter) and neutral (e.g., distant traffic) sound samples of 4 s duration were presented while noxious laser stimuli were administered to the dorsum of the right hand in 16 healthy participants. The electroencephalographic laser-evoked potentials (LEPs) were modelled using six equivalent source dipoles located in the left and right fronto-opercular/anterior-insular cortex, left parietal operculum, left primary somatosensory cortex, medial parietal cortex and left medial temporal cortex.

RESULTS

Negative emotional sounds were associated with stronger pain than neutral or positive sounds. The source activity in the left medial temporal cortex, purportedly involving hippocampal formation, in the epoch 294-330 ms was greater during negative than neutral or positive sounds. In the left fronto-opercular/anterior-insular cortex, negative sounds failed to show the positive potential component at around 260 ms that was observed during positive and especially during neutral sounds.

CONCLUSIONS

Results suggest increased input of pain-related information into the hippocampal formation when listening to negative emotional sounds, which may in turn facilitate temporal binding between representations of noxious and other behaviourally relevant stimuli, and perhaps associative learning. Absence of the positive potential component fronto-opercular/anterior-insular cortex during negative sounds points to a slow attentional disengagement from pain and increased awareness of the painful stimulus.