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>

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>

Affectionate Touch in the Context of Breastfeeding and Maternal Depression Influences Infant Neurodevelopmental and Temperamental Substrates

<b><i>Background:</i></b> While numerous studies have demonstrated maternal depression’s influence on infant brain development, few studies have examined the changes that occur as a consequence of co-occurring experiential factors that affect quality of mother and infant affectionate touch as well as infant temperament and neurophysiological systems. The aim of the study was to examine the interactive effects of maternal depression and breastfeeding on mother and infant affectionate touch and infant temperament and cortical maturation patterns across early development. <b><i>Methods:</i></b> 113 mothers and their infants participated when infants were 1 and 3 months of age. Questionnaires to assess maternal depressive symptoms, feeding, and temperament were completed. Tonic EEG patterns (asymmetry and left and right activity) were collected and the dyads were video-recorded during feeding to assess mother and infant affectionate touch patterns. <b><i>Results:</i></b> Data analysis showed that EEG activity and mother-infant affectionate touch differed as a function of mood and feeding method. Notably, only infants of depressed mothers that bottle-fed showed right frontal EEG asymmetry and attenuated change in the left frontal region across 3 months. Breastfeeding positively impacted affectionate touch behaviors and was associated with increased left and decreased right frontal EEG activation even for depressed groups. Furthermore, a model incorporating physiology, maternal depression, touch, temperament, and feeding indicated significant prediction for infant affectionate touch (with breastfeeding and affectively positive temperament demonstrating the strongest prediction). <b><i>Con­clusion:</i></b> The findings suggest that breastfeeding and the infant’s positive temperament influence mother-infant affectionate touch patterns and result in neuroprotective outcomes for infants, even those exposed to maternal depression within early development.