Andrey V. Bocharov

Predisposition to depression and implicit emotion processing

Depression, one of the most widespread mental disorders, is associated with considerable alterations in emotional functioning. It is unclear whether these alterations are associated with clinical depression or exist already at preclinical stages. Here, in clinically healthy individuals, a combination of neuroticism and introversion was used as a predisposition to depression (PD) scale. Participants were presented with pictures of emotional facial expressions and performed the gender discrimination task, while their electroencephalogram (EEG) was recorded. The affective processing bias (i.e., longer reaction time and higher error rate for angry faces) was found in low, but not in high PD scorers. High PD scorers also showed reduced theta synchronization and enhanced alpha desynchronization in the test interval and higher delta and theta power in the interstimuli interval. The latter effect implies that activity of emotional circuits, which is mirrored in low-frequency oscillations, is tonically increased in predisposed-to-depression individuals, thus precluding an adequate response to external emotional cues. This results in unspecific general activation reflected in enhanced alpha desynchronization and in disrupted ability to differentiate incoming emotional information.

Anxiety, depression, and oscillatory dynamics in a social interaction model

Although anxiety and depression frequently co-occur and share a substantial part of genetic vulnerability and other risk factors, they are distinct disorders and their effect on social functioning and accompanying cognitive and emotional processing could be different. In this study, in a nonclinical sample, we compared effects of trait anxiety and depressive symptoms on oscillatory dynamics accompanying perception of emotional facial expressions in the context of social interactions. Anxiety was associated with a longer reaction time, with preference of avoidance behavior, and with enhanced event-related alpha desynchronization and diminished theta synchronization. Depression did not show significant behavioral effects and was associated with diminished alpha desynchronization and augmented delta and theta synchronization in prefrontal cortical regions. Thus, in spite of frequent comorbidity, anxiety and depression show opposite patterns of associations with oscillatory dynamics accompanying social interactions. These patterns imply that anxiety is associated with hyper-reactive attentional system, whereas depression show signs of diminished cognitive reactivity. Depression-related enhancement of low-frequency synchronization in prefrontal cortex may reflect a compensatory mechanism of cognitive and emotional upregulation, which depression-prone individuals engage in the process of social interactions.

Depression and implicit emotion processing: An EEG study

OBJECTIVES Depression is one of the most prevalent mental illnesses and is associated with changes in emotion processing. The aim of this study was to determine the influence of depressive symptoms on EEG oscillatory dynamics accompanying implicit processing of angry and happy facial expressions in 46 healthy subjects. METHODS The Beck Depression Inventory was used to assess the presence of depressive symptoms in normal subjects. During the experiment, they were told to categorize the gender of angry, neutral, or happy faces presented to them, while high-resolution EEG was recorded. Analysis of the event-related spectral perturbations and the analysis of dipoles were carried out on EEG recordings using the EEGLAB toolbox. RESULTS High depression (HD) and low depression (LD) groups did not differ on error rate and reaction time during categorization of gender. The perception of happy faces was accompanied by higher theta synchronization in the LD than the HD group. In contrast, theta synchronization was higher in the HD than the LD group during perception of angry faces. CONCLUSION These findings imply that even at preclinical stages, HD scorers evidence increased emotional arousal to negative and decreased emotional arousal to positive stimuli during implicit emotion processing.

Oscillatory correlates of moral decision-making: Effect of personality.

The role of emotion in moral decision-making is still a matter of debate. Greene, Sommerville, Nystrom, Darley, and Cohen (2001) argue that ‘personal’ moral judgments are driven by emotional responses, while ‘impersonal’ judgments are largely driven by cognitive processes. In this study, oscillatory correlates of decision-making were compared in moral personal, moral impersonal, and nonmoral conditions, as well as in trials associated with utilitarian (i.e., favoring the ‘greater good’ over individual rights) and non-utilitarian choices. Event-related synchronization in delta and theta bands was greater in the right temporal lobe in personal than in both nonmoral and impersonal moral condition. Graph-theoretical analysis of connectivity patterns showed the prominent role of the orbitofrontal and cingulate cortices in personal moral decision-making, implying greater emotional and self-processing. Higher conscientiousness and intellect and lower behavioral activation were associated with greater difference in oscillatory responses between utilitarian and non-utilitarian choices in personal than in impersonal condition, indicating that sensitivity to moral issues and the ability to grasp the nuances of moral situation are essential for understanding the implications of utilitarian choices in personal and impersonal conditions.

Depressive symptoms and autobiographical memory: A pilot electroencephalography (EEG) study

ABSTRACT Introduction: Functional magnetic resonance imaging studies have shown changes in the activity of medial prefrontal, medial temporal, and occipital regions in major depressive disorder patients during recall of autobiographical memories. Electrophysiological underpinning of these changes is not known. It is also not clear whether they are a part of the clinical picture or appear at preclinical stages in individuals predisposed to depression. Method: In this study, the effect of depressive symptoms, as measured by the Beck Depression Inventory (BDI–II), on oscillatory dynamics accompanying retrieval of emotionally positive and negative autobiographical memories was investigated in a nonclinical sample using electroencephalographic event-related spectral power and connectivity measures. Results: Psychometric results showed that BDI scores correlated positively with the strength of negative emotion, vividness of negative memories, and their importance for participant’s life. In high BDI scorers, low-frequency synchronization, which is frequently used as a marker of emotional arousal, prevailed in negative episodes, whereas in low BDI scorers it prevailed in positive episodes. sLORETA localized sources of this synchronization in the medial prefrontal cortex. In negative episodes, depressive symptoms were associated with a diminished event-related connectivity in the alpha band in posterior regions and increased connectivity in beta and gamma bands in frontal regions. Conclusions: Overall, these results show that even at preclinical stages, depressive symptoms are associated with changes in electrophysiological processes accompanying retrieval of autobiographical memories.

Resting State Networks Mediate the Effect of Genotype by Environment Interaction on Mental Health

A number of studies have shown that the presence of short (S) allele of the serotonin transporter-linked polymorphic region (5-HTTLPR) is associated with a higher risk for depression following exposure to stressful life events. These findings are in line with neuroimaging studies showing that 5-HTTLPR polymorphism has an effect on the connectivity among key areas involved in emotion regulation. Here using mediated moderation analysis, we show that electrophysiological manifestations of resting state networks in the alpha frequency band mediate the effect of 5-HTTLPR by stress interaction on depression/anxiety symptoms in a nonclinical sample. Specifically, at the brain level, both L-allele homozygotes and S-allele carriers are similarly responsive to stress exposure. However, these brain responses seem to act as triggers of psychopathological symptoms in S-allele carriers, but as suppressors in L-allele homozygotes. This finding implies that the interpretation of the effect of gene by environment interaction on psychopathology seems more complicated than behavioral results alone would imply. It is not just differential sensitivity to stress, but rather different ways of coping with stress, which distinguish S-allele carriers and L-allele homozygotes.

EEG dynamics of spontaneous stimulus-independent thoughts

ABSTRACT In this study, we aimed to compare the oscillatory dynamics accompanying self-referential and non-self-referential stimulus-independent thoughts. Electroencephalograms were recorded in 30 healthy participants who were asked to press buttons classifying their spontaneous thoughts as self-referential or non-self-referential. EEG data were analyzed using independent component analysis in conjunction with dipole localization. Self-referential thoughts, as compared to non-self-referential thoughts, were accompanied by more pronounced decreases of theta, alpha, and beta spectral power in the anterior hub of the default-mode network, in the left lateral prefrontal, motor/somatosensory, and temporal cortices. These oscillatory dynamics are interpreted as a reflection of autobiographical memory retrieval intrinsic to self-referential thoughts. Abbreviations: BA: Brodmann area; BOLD: blood oxygenation level-dependent; DMN: default mode network; EEG: electroencephalogram; ERSP: event-related spectral perturbations; fMRI: functional magnetic resonance imaging; PCC: posterior cingulate cortex; PET: positron emission tomography; PFC: prefrontal cortex; SIT: stimulus-independent thought; WM: working memory.

Effect of 5-HTTLPR on current source density, connectivity, and topological properties of resting state EEG networks

The S allele of serotonin transporter gene (5-HTTLPR) has been found to increase the risk of depression and other mental health problems, but some evidence suggests that S-allele carriers outperform subjects carrying the long allele in an array of cognitive tasks. Evidence linking this polymorphism with individual variation in electrophysiological properties of resting state brain networks is very limited. This study investigated the effect of 5-HTTLPR polymorphism on EEG current source density, connectivity, and topological properties of resting state networks. We collected genetic and resting state EEG data in 113 Caucasians. As compared to L-homozygotes, S-allele carriers showed lower current source density and connectivity in most frequency bands in areas overlapping with the default mode and emotion regulation regions. The analysis of graph-theoretical measures showed that S-allele carriers, as compared to L-homozygotes, have less optimal topological properties of brain networks in theta, but more optimal in alpha band. This dissociation may reflect the predisposition to emotional disorders, which is inherent to S-allele carriers, and, on the other hand, their superior functioning in some cognitive domains.

Severity of depressive symptoms and oscillatory responses to emotional facial expressions

Differences in oscillatory responses to emotional facial expressions were studied in 40 subjects (19 men and 21 women aged from 18 to 30 years) varying in severity of depressive symptoms. Compared with perception of angry and neutral faces, perception of happy faces was accompanied by lower Δ synchronization in subjects with a low severity of depressive symptoms (Group 2) and higher Δ synchronization in subjects with a high severity of depressive symptoms (Group 1). Because synchronization of Δ oscillations is usually observed in aversive states, it was assumed that happy faces were perceived as negative stimuli by the Group 1 subjects. Perception of angry faces was accompanied by α desynchronization in Group 2 and α synchronization in Group 1. Based on Klimesch’s theory, the effect was assumed to indicate that the Group 1 subjects were initially set up for perception of negative emotional information. The effect of the emotional stimulus category was significant in Group 2 and nonsignificant in Group 1, testifying that the recognition of emotional information is hindered in depression-prone individuals.