Larger Theta Power Research Articles

Group identity modulates bidding behavior in repeated lottery contest: neural signatures from event-related potentials and electroencephalography oscillations.

A contest usually involves expenditures, termed "overbidding," exceeding the theoretical Nash equilibrium. A considerable number of studies have shown that group identity can affect decision-making and competitive behavior, thus providing a new perspective on alleviating the overbidding problem. How group identity influences brain activity when competitors bid in different groups is not yet clear, however. In this study, we implemented group identity manipulation into the lottery contest game and we recorded behavioral and electroencephalography (EEG) data at the same time. Two experimental treatments were conducted to study the effect of group identity on bidding behavior. The event-related potentials (ERP) and event-related oscillations (ERO) techniques were utilized to explore brain activity differences caused by participants' different bidding behaviors under in-group and out-group conditions. Behavioral results showed that individual expenditure was significantly lower when bidding with in-group opponents than with out-group opponents. Analyses of EEG results revealed that compared to in-group conditions, greater N2 amplitudes and theta power were found under out-group conditions. To extend previous studies, we performed supplementary analysis to explore whether enhancement of group identity had effects on conflict alleviation. Behavioral results indicated that individual expenditure was significantly lower after enhancing group identity when bidding with in-group, and EEG results showed more negative N2 amplitudes, smaller P3 amplitudes and larger theta power after enhancing group identity. Collectively, these findings indicate that group identity modulated bidding behavior, and they provide insight into a mechanism to de-escalate group conflict by enhancing group identity.

Cooperate or aggress? An opponent's tendency to cooperate modulates the neural dynamics of interpersonal cooperation

Humans are social animals and need to cooperate to survive. However, individuals are not cooperative in every social interaction, and their cooperation may depend on social context. The present study used a social dilemma game to investigate whether an opponent's tendency to be cooperative over time influenced a player's behavior and neural response to outcomes in the game. University students (“players”) thought they were playing against other students (“opponents”) in the Chicken Game but were actually playing against a programmed computer. Participants were randomly assigned to play with an opponent who tended to be competitive (cooperative 20% of the time) or who tended to be cooperative (cooperative 80% of the time). The results showed that early in the game, participants in both groups adopted a “tit-for-tat” strategy. However, as the game progressed and the opponent's behavioral tendency became more noticeable, players in the competitive-opponent group became generally more cooperative to limit their losses. ERPs analyses indicated that players had a higher P300 and larger theta power in response to the opponent's aggression but not to the opponent's cooperation when their opponent showed a tendency to be cooperative vs. competitive. The results suggest that people adjust their cooperative behavior based on their opponent's behavior in social interaction, and aggression captures more attention than cooperation in this process.

Appearance and modulation of a reactive temporal-lobe 8–10-Hz tau-rhythm

Spontaneous 8- to 10-Hz “tau-rhythm” in magnetoencephalographic (MEG) recordings has been reported to originate in the auditory cortex and be suppressed by sound. For unknown reasons however, tau-rhythm is often difficult to detect. In this study, we sought to characterize its emergence and auditory reactivity. Using a 306-channel MEG on 26 right-handed participants, we delivered six-second-long, natural, monaural sounds with pleasant, unpleasant, or neutral emotional valence. In eight participants, a clear, sound-related bilateral suppression of 8–10 Hz tau-rhythm occurred in the temporal areas, close to the source of the 100-ms auditory response. Moreover, these eight “tau subjects” exhibited significantly larger temporal-lobe theta-band (4–8 Hz) power over the entire experimental period compared to the remaining 18 “non-tau subjects”. As it is known that larger theta power is one of signs of drowsiness, this result is consistent with a previously proposed idea that tau-rhythm emerges during drowsiness. Tau-rhythm was furthermore significantly affected by emotional valence in the right hemisphere, where it was respectively suppressed by unpleasant and neutral sounds 8% and 6% more than by pleasant sounds, significantly. Altogether, our results reveal characteristics of tau-rhythm appearance and modulation which have hitherto been difficult to detect non-invasively.

Brain and behavioral inhibitory control of kindergartners facing negative emotions.

Inhibitory control (IC) - one of the most critical functions underlying a child's ability to self-regulate - develops significantly throughout the kindergarten years. Experiencing negative emotions imposes challenges on executive functioning and may specifically affect IC. In this study, we examined kindergartners' IC and its related brain activity during a negative emotional situation: 58 children (aged 5.5-6.5years) performed an emotion-induction Go/NoGo task. During this task, we recorded children's performance and brain activity, focusing on the fronto-central N2 component in the event-related potential (ERP) and the power of its underlying theta frequency. Compared to Go trials, inhibition of NoGo trials was associated with larger N2 amplitudes and theta power. The negative emotional experience resulted in better IC performance and, at the brain level, in larger theta power. Source localization of this effect showed that the brain activity related to IC during the negative emotional experience was principally generated in the posterior frontal regions. Furthermore, the band power measure was found to be a more sensitive index for children's inhibitory processes than N2 amplitudes. This is the first study to focus on kindergartners' IC while manipulating their emotional experience to induce negative emotions. Our findings suggest that a kindergartner's experience of negative emotion can result in improved IC and increases in associated aspects of brain activity. Our results also suggest the utility of time-frequency analyses in the study of brain processes associated with response inhibition in young children.