EEG Frontal Asymmetry in Dysthymia, Major Depressive Disorder and Euthymic Bipolar Disorder

In the last few decades, the incidence of mood disorders skyrocketed worldwide and has brought an increasing human and economic burden. Depending on the main symptoms and their evolution across time, they can be classified in several clinical subgroups. A few psychobiological indices have been extensively investigated as promising markers of mood disorders. Among these, frontal asymmetry measured at rest with quantitative EEG has represented the main available marker in recent years. Only a few studies so far attempted to distinguish the features and differences among diagnostic types of mood disorders by using this index. The present study measured frontal EEG asymmetry during a 5-min resting state in three samples of patients with bipolar disorder in a Euthymic phase (EBD, n = 17), major depressive disorder (MDD, n = 25) and persistent depressive disorder (PDD, n = 21), once termed dysthymia. We aimed to test the hypothesis that MDD and PDD lack the typical leftward asymmetry exhibited by normal as well as EBD patients, and that PDD shows greater clinical and neurophysiological impairments than MDD. Clinical scales revealed no symptoms in EBD, and significant larger anxiety and depression scores in PDD than in MDD patients. Relative beta (i.e., beta/alpha ratio) EEG asymmetry was measured from lateral frontal sites and results revealed the typical greater left than right frontal beta activity in EBD, as well as a lack of asymmetry in both MDD and PDD. The last two groups also had lower bilateral frontal beta activity in comparison with the EBD group. Results concerning group differences were interpreted by taking into account both the clinical and the neurophysiological domains.

Fearful temperament in middle childhood predicts adolescent attention bias and anxiety symptoms: The moderating role of frontal EEG asymmetry

The current study provided first analyses of the moderating effect of baseline-to-task frontal EEG asymmetry on the associations between 9-year fearful temperament and adolescent attention bias to threat as well as anxiety symptoms. Participants include a community sample of 122 children (60 boys, 62 girls; Mage = 14.66 years; Range = 11.82–18.13 years). Baseline-to-task frontal EEG asymmetry at age 9 moderated the relation between fearful temperament at age 9 and adolescent anxiety symptoms. Specifically, fearful temperament predicted adolescent anxiety symptoms when children showed greater right activation from baseline to an executive function task, but not greater left activation. Baseline-to-task frontal EEG asymmetry moderated the association between fearful temperament and sustained (i.e., stimulus onset asynchrony is 1250 ms) but not automatic attention bias (i.e., stimulus onset asynchrony is 500 ms). Children with greater left frontal activation from baseline to task more efficiently direct attention away from threat. Adolescent automatic attention bias to threat was related to concurrent anxiety symptoms. These findings illustrate the importance of considering frontal EEG asymmetry to shape how fearful children process threat and to influence their behavioral problems.

Testing the Asymmetric Inhibition Model: Frontal EEG Asymmetry Does Not Predict Inhibitory Control of Emotional Distractors

<p>Frontal electroencephalographic (EEG) asymmetry is a reliable marker of psychopathology vulnerability, yet the mechanisms underlying this relationship remain unclear. There is accumulating evidence that frontal asymmetry reflects individual differences in ability to use cognitive control to regulate emotional processing. This thesis provides the first test of the asymmetric inhibition model (Grimshaw & Carmel, 2014), which holds that frontal asymmetry reflects ability to engage valence-specific inhibitory control mechanisms supported by dorsolateral prefrontal cortex (dlPFC): left dlPFC inhibits negative distractors and right dlPFC inhibits positive distractors. Frontal asymmetry was tested as a predictor of ability to inhibit distracting emotional images. Frontal asymmetry was measured at rest and during emotional challenge, which is argued to provide a more powerful measure of individual differences (capability model; Coan, Allen, & McKnight, 2006). Emotional challenge was induced using a stressful serial subtraction task, verified to be effective in Study 1, followed by a silent speech preparation task, during which EEG was recorded. An irrelevant distractor paradigm measured ability to inhibit emotional distraction; participants identified a target letter within a central symbol array while attempting to inhibit positive, negative and neutral peripheral images (Study 2). Overall, positive and negative images were more distracting than neutral images. Critically, neither resting nor emotional challenge frontal asymmetry predicted distraction by positive, negative or neutral images, suggesting that frontal asymmetry does not reflect ability to inhibit irrelevant emotional distractors. Thus, the asymmetric inhibition model was not supported. This thesis provides the first direct test of the relationship between frontal EEG asymmetry and inhibitory control of emotion, paving the way for future explorations into this relationship. These findings add to a growing literature attempting to elucidate the cognitive mechanisms underlying frontal asymmetry in order to better understand the etiology of psychopathology.</p>

Emotion Regulation and Vulnerability to Depression: A Longitudinal Test of the Diathesis-Stress Model

<p>Maladaptive emotion regulation is an established vulnerability marker for depression. Within a diathesis-stress framework individual differences in emotion regulation constitute sensitivity to stress, such that people who are less able to effectively regulate their emotions are more likely to become depressed when stress is encountered. Markers of maladaptive emotion regulation have been examined from affective, neurological, and cognitive perspectives and, for the most part, have been examined in independent lines of research. As such, the independent and interactive contributions of maladaptive emotion regulation markers are still unknown. The current thesis addresses this gap with a longitudinal study. Emotion regulation markers and depression were assessed at the outset of the study (time one) then life stress and depression were measured three months (time two) and twelve months (time three) later. Three trait measures of emotion regulation were assessed: spontaneous emotion regulation (as indexed by startle reactivity following negative images), frontal and parietal resting EEG asymmetries, and brooding rumination. All emotion regulation markers were found to be independent markers of vulnerability to depression. The emotion regulation markers measured at time one were then tested within a diathesis stress framework to predict stress sensitivity at time two. Poorer online regulation interacted with life stress to predict depression. That is, poor online regulators were sensitive to stress at three months, whereas good online regulators were not. Stress sensitivity was tested again at time three, twelve months after the initial assessment. At this time point frontal asymmetry, parietal asymmetry and life stress interacted to predict depression. When right parietal activity was low, rightward frontal asymmetries showed more sensitivity to stress. However, people with leftward asymmetries showed less stress sensitivity. Brooding predicted depression at three months but not at twelve months and did not interact with stress at either time point. The findings of this thesis show that, within the diathesis-stress framework, online regulation measures indicate short-term sensitivity to stress; however, EEG asymmetry measures show sensitivity to stress in the longer term.</p>

Emotion Regulation and Vulnerability to Depression: A Longitudinal Test of the Diathesis-Stress Model

<p>Maladaptive emotion regulation is an established vulnerability marker for depression. Within a diathesis-stress framework individual differences in emotion regulation constitute sensitivity to stress, such that people who are less able to effectively regulate their emotions are more likely to become depressed when stress is encountered. Markers of maladaptive emotion regulation have been examined from affective, neurological, and cognitive perspectives and, for the most part, have been examined in independent lines of research. As such, the independent and interactive contributions of maladaptive emotion regulation markers are still unknown. The current thesis addresses this gap with a longitudinal study. Emotion regulation markers and depression were assessed at the outset of the study (time one) then life stress and depression were measured three months (time two) and twelve months (time three) later. Three trait measures of emotion regulation were assessed: spontaneous emotion regulation (as indexed by startle reactivity following negative images), frontal and parietal resting EEG asymmetries, and brooding rumination. All emotion regulation markers were found to be independent markers of vulnerability to depression. The emotion regulation markers measured at time one were then tested within a diathesis stress framework to predict stress sensitivity at time two. Poorer online regulation interacted with life stress to predict depression. That is, poor online regulators were sensitive to stress at three months, whereas good online regulators were not. Stress sensitivity was tested again at time three, twelve months after the initial assessment. At this time point frontal asymmetry, parietal asymmetry and life stress interacted to predict depression. When right parietal activity was low, rightward frontal asymmetries showed more sensitivity to stress. However, people with leftward asymmetries showed less stress sensitivity. Brooding predicted depression at three months but not at twelve months and did not interact with stress at either time point. The findings of this thesis show that, within the diathesis-stress framework, online regulation measures indicate short-term sensitivity to stress; however, EEG asymmetry measures show sensitivity to stress in the longer term.</p>

Testing the Asymmetric Inhibition Model: Frontal EEG Asymmetry Does Not Predict Inhibitory Control of Emotional Distractors

<p>Frontal electroencephalographic (EEG) asymmetry is a reliable marker of psychopathology vulnerability, yet the mechanisms underlying this relationship remain unclear. There is accumulating evidence that frontal asymmetry reflects individual differences in ability to use cognitive control to regulate emotional processing. This thesis provides the first test of the asymmetric inhibition model (Grimshaw & Carmel, 2014), which holds that frontal asymmetry reflects ability to engage valence-specific inhibitory control mechanisms supported by dorsolateral prefrontal cortex (dlPFC): left dlPFC inhibits negative distractors and right dlPFC inhibits positive distractors. Frontal asymmetry was tested as a predictor of ability to inhibit distracting emotional images. Frontal asymmetry was measured at rest and during emotional challenge, which is argued to provide a more powerful measure of individual differences (capability model; Coan, Allen, & McKnight, 2006). Emotional challenge was induced using a stressful serial subtraction task, verified to be effective in Study 1, followed by a silent speech preparation task, during which EEG was recorded. An irrelevant distractor paradigm measured ability to inhibit emotional distraction; participants identified a target letter within a central symbol array while attempting to inhibit positive, negative and neutral peripheral images (Study 2). Overall, positive and negative images were more distracting than neutral images. Critically, neither resting nor emotional challenge frontal asymmetry predicted distraction by positive, negative or neutral images, suggesting that frontal asymmetry does not reflect ability to inhibit irrelevant emotional distractors. Thus, the asymmetric inhibition model was not supported. This thesis provides the first direct test of the relationship between frontal EEG asymmetry and inhibitory control of emotion, paving the way for future explorations into this relationship. These findings add to a growing literature attempting to elucidate the cognitive mechanisms underlying frontal asymmetry in order to better understand the etiology of psychopathology.</p>

Improvement of Emotional Response to Negative Stimulations With Moderate-Intensity Physical Exercise

It is widely accepted that physical exercises (PEs) not only are good for fitness but also contribute to mental health and well-being. The positive influence of PEs on emotion has become a topic of much excitement. However, a quantitative study is required to discuss the effect of short-term moderate-intensity PE on the emotional response by using electroencephalogram (EEG) asymmetry. The experiments, including 20-min moderate-intensity cycling and EEG data acquisition with picture-induced emotion assessment protocol, were designed in this paper. The experiment procedure consists of two emotion assessment sessions, each of which contains 24 pictures. About 80 participants were randomly allocated into the exercise group and the control group. Participants in the exercise group were instructed to have a 20-min moderate-intensity cycling after the first assessment session, then rested until their heart rates recovered to baselines and their emotional states were assessed again in the second session. The control group only had a 20-min break without the cycling exercise between the two sessions. It was observed that, in the control group, the EEG asymmetry had no significant difference in these two assessment sessions for both positive and negative stimulations. However, in the exercise group, the difference of the EEG asymmetry before and after PE was significant only in response to negative stimulations. Further, the in-depth analysis of EEG asymmetry index changes of individual participants shows that the short-term moderate-intensity PE has a positive impact in response to negative stimulations. The proposed experiments show that the negative emotional experience can be reduced by the moderate-intensity PE and support the hypothesis that the moderate-intensity PE is good at improving emotional response to negative stimulations. This study provides the evidence of positive effects of PE in the domain of emotion regulation with experimental data.