Ключарёв Василий Андреевич

MEG study of social conformity

2013 · CHAPTER · en

Electrophysiological precursors of social conformity

2013 · ARTICLE · en

Humans often change their beliefs or behavior due to the behavior or opinions of others. This study explored, with the use of human event-related potentials (ERPs), whether social conformity is based on a general performance-monitoring mechanism. We tested the hypothesis that conflicts with a normative group opinion evoke a feedback-related negativity (FRN) often associated with performance monitoring and subsequent adjustment of behavior. The experimental results show that individual judgments of facial attractiveness were adjusted in line with a normative group opinion. A mismatch between individual and group opinions triggered a frontocentral negative deflection with the maximum at 200 ms, similar to FRN. Overall, a conflict with a normative group opinion triggered a cascade of neuronal responses: from an earlier FRN response reflecting a conflict with the normative opinion to a later ERP component (peaking at 380 ms) reflecting a conforming behavioral adjustment. These results add to the growing literature on neuronal mechanisms of social influence by disentangling the conflict-monitoring signal in response to the perceived violation of social norms and the neural signal of a conforming behavioral adjustment.

Нейроэкономика: нейробиология принятия решений

2011 · ARTICLE · ru

Происходящий в настоящее время синтез экономических наук, психологии и нейробиологии в рамках новой дисциплины – нейроэкономики, а также развитие новейших нейроимиджинговых методов обещают появление новой междисциплинарной модели, объясняющей механизмы принятия решений. Результаты нейроэкономических исследований демонстрируют, что принятие решений обусловлено работой относительно независимых нейрональных систем мозга, отобранных посредством естественного отбора. Взаимодействие «когнитивных» и «эмоциональных» нейрональных механизмов принятия решений определяет степень рациональности поведения человека.

Downregulation of the posterior medial frontal cortex prevents social conformity

2011 · ARTICLE · en

We often change our behavior to conform to real or imagined group pressure. Social influence on our behavior has been extensively studied in social psychology, but its neural mechanisms have remained largely unknown. Here we demonstrate that the transient downregulation of the posterior medial frontal cortex by theta-burst transcranial magnetic stimulation reduces conformity, as indicated by reduced conformal adjustments in line with group opinion. Both the extent and probability of conformal behavioral adjustments decreased significantly relative to a sham and a control stimulation over another brain area. The posterior part of the medial frontal cortex has previously been implicated in behavioral and attitudinal adjustments. Here, we provide the first interventional evidence of its critical role in social influence on human behavior.

Celebrities and shoes on the female brain: The neural correlates of product evaluation in the context of fame

2010 · ARTICLE · en

Celebrity endorsement is omnipresent. However, despite its prevalence, it is unclear why celebrities are more persuasive than (equally attractive) non-famous endorsers. The present study investigates which processes underlie the effect of fame on product memory and purchase intention by the use of functional magnetic resonance imaging methods. We find an increase in activity in the medial orbitofrontal cortex (mOFC) underlying the processing of celebrity–product pairings. This finding suggests that the effectiveness of celebrities stems from a transfer of positive affect from celebrity to product. Additional neuroimaging results indicate that this positive affect is elicited by the spontaneous retrieval of explicit memories associated with the celebrity endorser. Also, we demonstrate that neither the activation of implicit memories of earlier exposures nor an increase in attentional processing is essential for a celebrity advertisement to be effective. By explaining the neural mechanism of fame, our results illustrate how neuroscience may contribute to a better understanding of consumer behavior.

Reinforcement learning signal predicts social conformity

2009 · ARTICLE · en

We often change our decisions and judgments to conform with normative group behavior. However, the neural mechanisms of social conformity remain unclear. Here we show, using functional magnetic resonance imaging, that conformity is based on mechanisms that comply with principles of reinforcement learning. We found that individual judgments of facial attractiveness are adjusted in line with group opinion. Conflict with group opinion triggered a neuronal response in the rostral cingulate zone and the ventral striatum similar to the "prediction error" signal suggested by neuroscientific models of reinforcement learning. The amplitude of the conflict-related signal predicted subsequent conforming behavioral adjustments. Furthermore, the individual amplitude of the conflict-related signal in the ventral striatum correlated with differences in conforming behavior across subjects. These findings provide evidence that social group norms evoke conformity via learning mechanisms reflected in the activity of the rostral cingulate zone and ventral striatum.

Brain mechanisms of persuasion: how 'expert power' modulates memory and attitudes

2008 · ARTICLE · en

Human behaviour is affected by various forms of persuasion. The general persuasive effect of high expertise of the communicator, often referred to as ’expert power’, is well documented. We found that a single exposure to a combination of an expert and an object leads to a long-lasting positive effect on memory for and attitude towards the object. Using functional magnetic resonance imaging, we probed the neural processes predicting these behavioural effects. Expert context was associated with distributed left-lateralized brain activity in prefrontal and temporal cortices related to active semantic elaboration. Furthermore, experts enhanced subsequent memory effects in the medial temporal lobe (i.e. in hippocampus and parahippocampal gyrus) involved in memory formation. Experts also affected subsequent attitude effects in the caudate nucleus involved in trustful behaviour, reward processing and learning. These results may suggest that the persuasive effect of experts is mediated by modulation of caudate activity resulting in a re-evaluation of the object in terms of its perceived value. Results extend our view of the functional role of the dorsal striatum in social interaction and enable us to make the first steps toward a neuroscientific model of persuasion.

Effect of emotional context in auditory-cortex processing.

2007 · ARTICLE · en

We examined how emotional context influences processing of emotionally neutral acoustic stimuli in the human auditory cortex. Nine subjects performed a simple discrimination task. In the positive-emotional trials correct performance was awarded with money, whereas in the negative-emotional trials, correct performance resulted in avoidance of the loss of money. Auditory stimuli were identical in both trial types. An event-related brain potential (ERP) N100 deflection, generated in the auditory cortex, was significantly larger in the negative as compared to the positive-emotional trials. This result demonstrates that emotional context influences early sensory-specific cortical processing. In addition, we found some evidence in favor of assumption that processing of positive visual feedback was faster in negative-emotional trials. This was reflected in the tendency for the latency of visual ERPs to be shorter in the latter case. We suggest that our results indicate that the systemic organization at all stages of deployment of behavior depends on emotional context. Dynamics of learning the discrimination task was also dependent on emotional context.

Interaction of gaze direction and facial expressions processing: ERP study

2004 · ARTICLE · en

Event related potentials (ERPs) were recorded from 11 subjects watching photographs of angry and happy faces with different gaze directions. ERPs to right averted gaze differed from those to straight and left averted gaze at 85 and 460 ms whereas ERPs to happy and angry expressions differed at 115, 330 and 380 ms. We suggest that short-latency effects, maximal over occipital cortex, reflect the involvement of visual cortex in the early analysis of socially-relevant stimuli. Interaction of gaze and expressions was reflected in ERPs at 270 - 450 ms. We conclude that gaze and emotional expressions are analyzed in parallel at the early stages of visual processing. The interaction of these two processing streams starts no earlier than at 270 ms.

Electrophysiological indicators of phonetic and non-phonetic multisensory interactions during audiovisual speech perception.

2003 · ARTICLE · en

We studied the interactions in neural processing of auditory and visual speech by recording event-related brain potentials (ERPs). Unisensory (auditory - A and visual - V) and audiovisual (AV) vowels were presented to 11 subjects. AV vowels were phonetically either congruent (e.g., acoustic /a/ and visual /a/) or incongruent (e.g., acoustic /a/ and visual /y/). ERPs to AV stimuli and the sum of the ERPs to A and V stimuli (A+V) were compared. Similar ERPs to AV and A+V were hypothesized to indicate independent processing of A and V stimuli. Differences on the other hand would suggest AV interactions. Three deflections, the first peaking at about 85 ms after the A stimulus onset, were significantly larger in the ERPs to A+V than in the ERPs to both congruent and incongruent AV stimuli. We suggest that these differences reflect AV interactions in the processing of general, non-phonetic, features shared by the acoustic and visual stimulus (spatial location, coincidence in time). The first difference in the ERPs to incongruent and congruent AV vowels peaked at 155 ms from the A stimuli onset. This and two later differences are suggested to reflect interactions at phonetic level. The early general AV interactions probably reflect modified activity in the sensory-specific cortices, whereas the later phonetic AV interactions are likely generated in the heteromodal cortices. Thus, our results suggest that sensory-specific and heteromodal brain regions participate in AV speech integration at separate latencies and are sensitive to different features of A and V speech stimuli.