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Nonlinear EEG analysis offers the potential for both increased diagnostic accuracy and deeper mechanistic understanding of psychopathology. EEG complexity measures have previously been shown to positively correlate with clinical depression. In this study, resting state EEG recordings were taken across multiple sessions and days with both eyes open and eyes closed conditions from a total of 306 subjects, 62 of which were in a current depressive episode, and 81 of which had a history of diagnosed depression but were not currently depressed. Three different EEG montages (mastoids, average, and Laplacian) were also computed. Higuchi fractal dimension (HFD) and sample entropy (SampEn) were calculated for each unique condition. The complexity metrics showed high internal consistency within session and high stability across days. Higher complexity was found in open-eye recordings compared to closed eyes. The predicted correlation between complexity and depression was not found. However, an unexpected sex effect was observed, in which males and females exhibited different topographic patterns of complexity., (© 2023 Society for Psychophysiological Research.)

Frontal alpha asymmetry (FAA) is considered to be a reliable marker of affective processing and psychopathology. Traditionally, the magnitude of alpha is calculated by taking the average over a nomothetic fixed frequency window (e.g., 8 to 13 Hz). Alternatively, methods have been proposed to extract individualized alpha frequency (IAF) peaks and windows in hopes of improving the reliability and validity of signal detection. However, no study has compared the nomothetic to IAF approaches to examine the reliability and validity of resting FAA in a large well-characterized data set. In this study, we assessed the psychometric performance of the standard fixed window approach, a PZ-alpha based IAF approach and a global-alpha based IAF windows detection approach on a previously collected EEG data set (8 recordings per subject collected on four occasions across two weeks). Our results revealed that resting FAA calculated with these three different methods are highly correlated at all frontal regions (mean r = .98). The stability across the 8 recordings over the two weeks also showed no substantial difference between approaches as indicated by intraclass correlations. Moreover, internal-consistency reliability, validity with respect to measures of emotion and emotion-related psychopathology and state-trait Structure equation model (SEM) fitting were evaluated and yielded no significant differences across methods. Our results supported the overall reliability and validity of two different IAF approaches to assessing resting FAA but fail to find any incremental advantage over nomothetic approaches to defining alpha bands. Guidelines for methods selection for future research are provided., (© 2022 Society for Psychophysiological Research.)

Resting frontal encephalographic (EEG) asymmetry, often conceptualized as a trait marker for depression, is influenced by occasion-specific factors, including time of year and the time of day of the recording session as demonstrated recently (Peterson and Harmon-Jones, 2009). The current study examined the influence of seasonal and chronological variables on resting frontal asymmetry, and also assessed whether different reference montages or surface transformations were equally susceptible to these influences. In a direct replication attempt, contrary to previous findings, no simple time of year by time of day interaction was found. Time awake at recording, however, was an important moderating variable of the relationship between photoperiod and time of day. EEG asymmetry scores based on current-source density (CSD) transformed data, however, appeared less vulnerable to these influences, providing further evidence to suggest that the CSD transform may be advantageous for examining stable trait estimates of frontal EEG asymmetry., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: Although it has been argued that frontal electroencephalographic (EEG) asymmetry at rest may be a risk marker for major depressive disorder (MDD), it is unclear whether a pattern of relatively less left than right activity characterizes depressed individuals during emotional challenges. Examination of frontal asymmetry during emotion task manipulations could provide an assessment of the function of systems relevant for MDD, and test the limits of frontal EEG asymmetry as a marker of risk for depression., Methods: EEG data were assessed during a facial emotion task, wherein 306 individuals age 18-34 (31% male) with (n=143) and without (n=163) DSM-IV defined lifetime MDD made directed facial actions of approach (angry and happy) and withdrawal (afraid and sad) expressions., Results: Lifetime depressed individuals displayed less relative left frontal activity than never-depressed individuals during all facial expressions across four EEG reference montages, findings that were not due to emotional experience, facial expression quality, electromyographic (EMG) activity, or current depression status., Limitations: Although this was a sizable sample, only one emotion task was utilized., Conclusions: Results provide further support for frontal EEG asymmetry as a risk marker for MDD., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Background: Pre-menstrual dysphoric disorder (PMDD), a dysphoric form of pre-menstrual syndrome, is included as a diagnosis for further study in the DSM-IV-TR (APA, 2000). The present study investigated whether a marker of risk for major depressive disorder (MDD), prefrontal brain asymmetry, also characterizes women with PMDD., Methods: In a sample of 25 college women with PMDD symptomatology and 25 matched controls, resting frontal electroencephalographic (EEG) activity was assessed on four occasions within a two-week span., Results: Across several frontal sites women with PMDD had relatively less left than right prefrontal brain activity, consistent with a diathesis-stress model for menstrual-related dysphoria., Conclusions: The findings suggest an overlap in the risk profile for MDD and PMDD., (Published by Elsevier B.V.)

Resting frontal electroencephalographic (EEG) asymmetry has been hypothesized as a marker of risk for major depressive disorder (MDD), but the extant literature is based predominately on female samples. Resting frontal asymmetry was assessed on 4 occasions within a 2-week period in 306 individuals aged 18-34 (31% male) with (n = 143) and without (n = 163) lifetime MDD as defined by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (American Psychiatric Association, 1994). Lifetime MDD was linked to relatively less left frontal activity for both sexes using a current source density (CSD) reference, findings that were not accounted for solely by current MDD status or current depression severity, suggesting that CSD-referenced EEG asymmetry is a possible endophenotype for depression. In contrast, results for average and linked mastoid references were less consistent but demonstrated a link between less left frontal activity and current depression severity in women., (Copyright 2010 APA, all rights reserved)

Background: Tryptophan depletion (TD) reduces brain serotonin and may induce acute depressive symptomatology, especially among those with a history of Major Depression. Depressive response to TD among euthymic patients with a history of depression also predicts future depression. Better prediction might result by assessing a putative endophenotype for depressive risk, frontal electroencephalographic (EEG) asymmetry, in the context of TD., Method: Nine euthymic history-positive participants and nine controls were administered TD. Symptomatic and EEG frontal asymmetry data were collected for 6 h following TD, and clinical status was followed for the next 12 months., Results: The magnitude of TD-induced change in frontal EEG asymmetry significantly predicted the development of depression during the ensuing six to twelve months, and with greater sensitivity than symptomatic response., Limitations: The results are tempered by the small sample size., Conclusions: Despite the limited sample size, these preliminary results suggest that TD-induced changes in frontal EEG asymmetry may provide a more sensitive indicator of risk for imminent depression than symptomatic response to TD.

Frontal alpha asymmetry is typically computed using alpha power averaged across many overlapping epochs. Previous reports have estimated the internal consistency reliability of asymmetry by dividing resting EEG sessions into segments of equal duration (e.g., 1 min) and treating asymmetry scores for each segment as "items" to estimate internal consistency reliability using Cronbach's alpha. Cronbach's alpha partly depends on the number of items, such that this approach may underestimate reliability by using less than the number of distinct items available. Reliability estimates for resting EEG data in the present study (204 subjects, 8 sessions) were obtained using mean split-half correlations with epoch alpha power as treated as separate items. Estimates at all scalp sites and reference schemes approached .90 with as few as 100 epochs, suggesting the internal consistency of frontal asymmetry is greater than that previously reported.

Objective: The error-related negativity (ERN) is a response-locked brain potential (ERP) occurring 80-100ms following response errors. This report contrasts three views of the genesis of the ERN, testing the classic view that time-locked phasic bursts give rise to the ERN against the view that the ERN arises from a pure phase-resetting of ongoing theta (4-7Hz) EEG activity and the view that the ERN is generated - at least in part - by a phase-resetting and amplitude enhancement of ongoing theta EEG activity., Methods: Time-domain ERP analyses were augmented with time-frequency investigations of phase-locked and non-phase-locked spectral power, and inter-trial phase coherence (ITPC) computed from individual EEG trials, examining time courses and scalp topographies. Simulations based on the assumptions of the classic, pure phase-resetting, and phase-resetting plus enhancement views, using parameters from each subject's empirical data, were used to contrast the time-frequency findings that could be expected if one or more of these hypotheses adequately modeled the data., Results: Error responses produced larger amplitude activity than correct responses in time-domain ERPs immediately following responses, as expected. Time-frequency analyses revealed that significant error-related post-response increases in total spectral power (phase- and non-phase-locked), phase-locked power, and ITPC were primarily restricted to the theta range, with this effect located over midfrontocentral sites, with a temporal distribution from approximately 150-200ms prior to the button press and persisting up to 400ms post-button press. The increase in non-phase-locked power (total power minus phase-locked power) was larger than phase-locked power, indicating that the bulk of the theta event-related dynamics were not phase-locked to response. Results of the simulations revealed a good fit for data simulated according to the phase-locking with amplitude enhancement perspective, and a poor fit for data simulated according to the classic view and the pure phase-resetting view., Conclusions: Error responses produce not only phase-locked increases in theta EEG activity, but also increases in non-phase-locked theta, both of which share a similar topography., Significance: The findings are thus consistent with the notion advanced by Luu et al. [Luu P, Tucker DM, Makeig S. Frontal midline theta and the error-related negativity; neurophysiological mechanisms of action regulation. Clin Neurophysiol 2004;115:1821-35] that the ERN emerges, at least in part, from a phase-resetting and phase-locking of ongoing theta-band activity, in the context of a general increase in theta power following errors.

Researchers interested in measuring individual differences in affective style via asymmetries in frontal brain activity have depended almost exclusively upon the resting state for EEG recording. This reflects an implicit conceptualization of affective style as a response predisposition that is manifest in frontal EEG asymmetry, with the goal to describe individuals in terms of their general approach or withdrawal tendencies. Alternatively, the response capability conceptualization seeks to identify individual capabilities for approach versus withdrawal responses during emotionally salient events. The capability approach confers a variety of advantages to the study of affective style and personality, and suggests new possibilities for the approach/withdrawal motivational model of frontal EEG asymmetry and emotion. Logical as well as empirical arguments supportive of this conclusion are presented.

Resting frontal electroencephalographic (EEG) asymmetry has been hypothesized to tap a diathesis toward depression or other emotion-related psychopathology. Frontal EEG asymmetry was assessed in college women who reported high (n = 12) or low (n = 11) levels of premenstrual negative affect. Participants were assessed during both the follicular and the late luteal phases of the menstrual cycle. Women reporting low premenstrual dysphoric symptomatology exhibited greater relative left frontal activity at rest than did women high in premenstrual dysphoric symptomatology, an effect that was not qualified by phase of cycle. Although women with extreme levels of symptomatology were assessed, the question of whether such symptoms qualified for premenstrual dysphoric disorder criteria was not assessed. These results are consistent with a diathesis-stress model for premenstrual dysphoric symptomatology., (2006 APA, all rights reserved)

Objective: (1) To investigate the neural synchrony hypothesis by examining if there was more synchrony for upright than inverted Mooney faces, replicating a previous study; (2) to investigate whether inverted stimuli evoke neural synchrony by comparing them to a new scrambled control condition, less likely to produce face perception., Methods: Multichannel EEG was recorded via nose reference while participants viewed upright, inverted, and scrambled Mooney face stimuli. Gamma-range spectral power and inter-electrode phase synchrony were calculated via a wavelet-based method for upright stimuli perceived as faces and inverted/scrambled stimuli perceived as non-faces., Results: When the frequency of interest was selected from the upright condition exhibiting maximal spectral power responses (as in the previous study) greater phase synchrony was found in the upright than inverted/scrambled conditions. However, substantial synchrony was present in all conditions, suggesting that choosing the frequency of interest from the upright condition only may have been biased. In addition, artifacts related to nose reference contamination by micro-saccades were found to be differentially present across experimental conditions in the raw EEG. When frequency of interest was selected instead from each experimental condition and the data were transformed to a laplacian 'reference free' derivation, the between-condition phase synchrony differences disappeared. Spectral power differences were robust to the change in reference, but not the combined changes in reference and frequency selection criteria., Conclusions: Synchrony differences between face/non-face perceptions depend upon frequency selection and recording reference. Optimal selection of these parameters abolishes differential synchrony between conditions., Significance: Neural synchrony is present not just for face percepts for upright stimuli, but also for non-face percepts achieved for inverted/scrambled Mooney stimuli.

There exists a substantial literature examining frontal electroencephalographic asymmetries in emotion, motivation, and psychopathology. Research in this area uses a specialized set of approaches for reducing raw EEG signals to metrics that provide the basis for making inferences about the role of frontal brain activity in emotion. The present review details some of the common data processing routines used in this field of research, with a focus on statistical and methodological issues that have captured, and should capture, the attention of researchers in this field.

Frontal EEG asymmetry appears to serve as (1) an individual difference variable related to emotional responding and emotional disorders, and (2) a state-dependent concomitant of emotional responding. Such findings, highlighted in this review, suggest that frontal EEG asymmetry may serve as both a moderator and a mediator of emotion- and motivation-related constructs. Unequivocal evidence supporting frontal EEG asymmetry as a moderator and/or mediator of emotion is lacking, as insufficient attention has been given to analyzing the frontal EEG asymmetries in terms of moderators and mediators. The present report reviews the frontal EEG asymmetry literature from the framework of moderators and mediators, and overviews data analytic strategies that would support claims of moderation and mediation.

Although resting frontal electroencephalographic (EEG) alpha asymmetry has been shown to be a stable measure over time in nonclinical populations, its reliability and stability in clinically depressed individuals has not been fully investigated. The internal consistency and test-retest stability of resting EEG alpha (8-13 Hz) asymmetry were examined in 30 women diagnosed with major depression at 4-week intervals for 8 or 16 weeks. Asymmetry scores generally displayed good internal consistency and exhibited modest stability over the 8- and 16-week assessment intervals. Changes in asymmetry scores over this interval were not significantly related to changes in clinical state. These findings suggest that resting EEG alpha asymmetry can be reliably assessed in clinically depressed populations. Furthermore, intraclass correlation stability estimates suggest that although some traitlike aspects of alpha asymmetry exist in depressed individuals, there is also evidence of changes in asymmetry across assessment occasions that are not closely linked to changes in depressive severity.

Two studies have examined whether there exists a relationship between resting frontal alpha asymmetry and the Behavioral Inhibition and Activation Scales (C. S. Carver & T. L. White, 1994), which are based on Gray's Behavioral Inhibition and Behavioral Activation Systems. Findings suggest that greater relative left frontal activity characterizes individuals higher in self-reported behavioral activation sensitivity (E. Harmon-Jones & J. J. B. Allen, 1997; S. K. Sutton & R. J. Davidson, 1997), and, in one instance, lower behavioral inhibition sensitivity (S. K. Sutton & R. J. Davidson, 1997). In the present study, relatively greater left frontal activity correlated positively with behavioral activation scores. No significant relationship between resting frontal alpha asymmetry and the behavioral inhibition score emerged. These data suggest that relatively greater left frontal activity is indeed an index of approach oriented, appetitive motivational tendencies, whereas the relationship between relative right frontal activity and the behavioral inhibition system is likely to be complex and not accounted for by behavioral withdrawal alone.

Background: Since the replication crisis, standardization has become even more important in psychological science and neuroscience. As a result, many methods are being reconsidered, and researchers' degrees of freedom in these methods are being discussed as a potential source of inconsistencies across studies. New Method: With the aim of addressing these subjectivity issues, we have been working on a tutorial-like EEG (pre-)processing pipeline to achieve an automated method based on the semi-automated analysis proposed by Delorme and Makeig. Results: Two scripts are presented and explained step-by-step to perform basic, informed ERP and frequency-domain analyses, including data export to statistical programs and visual representations of the data. The open-source software EEGlab in MATLAB is used as the data handling platform, but scripts based on code provided by Mike Cohen (2014) are also included. Comparison with existing methods: This accompanying tutorial-like article explains and shows how the processing of our automated pipeline affects the data and addresses, especially beginners in EEG-analysis, as other (pre)-processing chains are mostly targeting rather informed users in specialized areas or only parts of a complete procedure. In this context, we compared our pipeline with a selection of existing approaches. Conclusion: The need for standardization and replication is evident, yet it is equally important to control the plausibility of the suggested solution by data exploration. Here, we provide the community with a tool to enhance the understanding and capability of EEG-analysis. We aim to contribute to comprehensive and reliable analyses for neuro-scientific research. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusess topics within the issue including electroencephalogram asymmetry; research on frontal asymmetry in motivation; and individuals with a history of childhood onset depression.

For over 35 years, research has examined frontal alpha EEG asymmetry, discussed in terms of relative left frontal activity (rLFA) in the present review, as a concurrent and prospective marker of affective processing and psychopathology. Because rLFA may index (a) neural correlates of frontal asymmetry, or (b) psychological constructs to which frontal asymmetry relates, rLFA can advance our understanding of both neural and psychological models of emotion and psychopathology. In order to improve such understanding, the specific role of rLFA in extending or challenging existing theory must be clear to researchers and readers alike. In particular, in 2004, Coan and Allen argued that examination of rLFA as a mediator or moderator may improve our theoretical understanding of rLFA. Despite being a commonly cited paper in the field, most rLFA research today still fails to acknowledge the statistical role of rLFA in the research. The aim of the present paper is to (a) convince the reader of the importance of distinguishing rLFA as a predictor, outcome, mediator, or moderator in order to conduct theory-driven research, and (b) highlight some of the major advances in rLFA literature since the review by Coan and Allen (2004) in the framework of mediators and moderators. We selected a broad range of search terms to capture relevant rLFA research and included only those studies utilizing established methods for rLFA measurement. [ABSTRACT FROM AUTHOR]

Frontal EEG alpha asymmetry provides a promising index of depression risk, yet very little is known about the neural sources of alpha asymmetry. To identify these sources, this study examined alpha asymmetry using a distributed inverse solution: exact low resolution brain electromagnetic tomography (eLORETA). Findings implicated a generator in lateral midfrontal regions that contributed to both surface asymmetry and depression risk. Participants with any lifetime history of depressive episodes were characterized by less left than right activity in the precentral gyrus and midfrontal gyrus. Anhedonia accounted for a significant portion of the relationship between alpha asymmetry and lifetime major depressive disorder. Results are suggestive of convergence between motivational and capability models of asymmetry and replicate results from experimental studies in a large resting-state data set. The capability model of frontal alpha asymmetry is contextualized in terms of motor preparedness following emotional mobilization. [ABSTRACT FROM AUTHOR]

The capability model of frontal electroencephalographic ( EEG) asymmetry suggests that brain activity during emotional challenge will be a more powerful indicator of predispositions toward psychopathology than activity observed at rest. EEG data were assessed during a resting baseline and a facial emotion task, wherein individuals with ( n = 143) and without ( n = 163) lifetime major depressive disorder ( MDD) made approach (angry and happy) and withdrawal (afraid and sad) facial expressions. EEG asymmetry during emotional challenge was a more powerful indicator of MDD status than resting asymmetry for average, Cz, and linked mastoid references, results in support of the capability model. However, current-source-density ( CSD) transformed asymmetry was indicative of lifetime MDD status under resting and task-elicited conditions. Findings suggest that CSD-transformed data may be more robust indicators of trait frontal EEG asymmetry. [ABSTRACT FROM AUTHOR]

To examine how stress affects cognitive functioning, individual differences in trait vulnerability (punishment sensitivity) and state reactivity (negative affect) to social evaluative threat were examined during concurrent reinforcement learning. Lower trait-level punishment sensitivity predicted better reward learning and poorer punishment learning; the opposite pattern was found in more punishment sensitive individuals. Increasing state-level negative affect was directly related to punishment learning accuracy in highly punishment sensitive individuals, but these measures were inversely related in less sensitive individuals. Combined electrophysiological measurement, performance accuracy and computational estimations of learning parameters suggest that trait and state vulnerability to stress alter cortico-striatal functioning during reinforcement learning, possibly mediated via medio-frontal cortical systems. [ABSTRACT FROM PUBLISHER]

Relatively less right parietal activity may reflect reduced arousal and signify risk for major depressive disorder (MDD). Inconsistent findings with parietal electroencephalographic (EEG) asymmetry, however, suggest issues such as anxiety comorbidity and sex differences have yet to be resolved. Resting parietal EEG asymmetry was assessed in 306 individuals (31% male) with ( n=143) and without ( n=163) a DSM-IV diagnosis of lifetime MDD and no comorbid anxiety disorders. Past MDD+ women displayed relatively less right parietal activity than current MDD+ and MDD− women, replicating prior work. Recent caffeine intake, an index of arousal, moderated the relationship between depression and EEG asymmetry for women and men. Findings suggest that sex differences and arousal should be examined in studies of depression and regional brain activity. [ABSTRACT FROM AUTHOR]

Error-related activity in the medial prefrontal cortex (mPFC) is thought to work in conjunction with lateral prefrontal cortex (lPFC) as a part of an action-monitoring network, where errors signal the need for increased cognitive control. The neural mechanism by which this mPFC-lPFC interaction occurs remains unknown. We hypothesized that transient synchronous oscillations in the theta range reflect a mechanism by which these structures interact. To test this hypothesis, we extracted oscillatory phase and power from current-source-density-transformed electroencephalographic data recorded during a Flanker task. Theta power in the mPFC was diminished on the trial preceding an error and increased immediately after an error, consistent with predictions of an action-monitoring system. These power dynamics appeared to take place over a response-related background of oscillatory theta phase coherence. Theta phase synchronization between FCz (mPFC) and F5/6 (lPFC) sites was robustly increased during error trials. The degree of mPFC-lPFC oscillatory synchronization predicted the degree of mPFC power on error trials, and both of these dynamics predicted the degree of posterror reaction time slowing. Oscillatory dynamics in the theta band may in part underlie a mechanism of communication between networks involved in action monitoring and cognitive control. [ABSTRACT FROM AUTHOR]