Event-related potentials (ERPs) to hemifield presentations of emotional stimuli: differences between depressed patients and healthy adults in P3 amplitude and asymmetry

Personality and emotional processing: A relationship between extraversion and the late positive potential in adolescence

Neuroticism and extraversion are multifaceted affective-laden personality traits that have been associated with major depressive disorder (MDD). Research and theory have argued that extraversion, and particularly its facet positive emotionality, is specific to MDD, while neuroticism is common across internalizing disorders. Converging evidence has suggested that MDD is associated with reduced engagement with emotional stimuli, but it remains unclear whether either extraversion, neuroticism, or both modulate reactivity to emotional cues. The late positive potential (LPP) is an event-related brain potential that is uniquely suited to assess engagement with emotional stimuli because it reflects sustained attention toward emotional content. The current study examined the LPP in relation to personality traits that may confer risk for depression by examining the relationship between the LPP and both neuroticism and extraversion in never-depressed adolescent girls. Specifically, 550 girls aged 13.5-15.5 with no lifetime history of depression completed an emotional picture-viewing task, and the LPP was measured in response to neutral, pleasant, and unpleasant pictures. Personality traits were gathered via self- and informant report. Results indicated that high extraversion was associated with a potentiated LPP to emotional pictures-and this effect was accounted for by positive emotionality in particular. In contrast, there was no association between the LPP and neuroticism or its facets. The present study is one of the first to demonstrate that extraversion is associated with variation in neural indices of emotional picture processing, similar to what has been observed among individuals with depression and at high risk for depression.

Hemifield-dependent N1 and event-related theta/delta oscillations: An unbiased comparison of surface Laplacian and common EEG reference choices

Surface Laplacian methodology has been used to reduce the impact of volume conduction and arbitrary choice of EEG recording reference for the analysis of surface potentials. However, the empirical implications of employing these different transformations to the same EEG data remain obscure. This study directly compared the statistical effects of four commonly-used (nose, linked mastoids, average) or recommended (reference electrode standardization technique [REST]) references and their spherical spline current source density (CSD) transformation for a large data set stemming from a well-understood experimental manipulation. ERPs (72 sites) recorded from 130 individuals during a visual half-field paradigm with highly-controlled emotional stimuli were characterized by mid-parietooccipital N1 (125 ms peak latency) and event-related synchronization (ERS) of theta/delta (160 ms), which were most robust over the contralateral hemisphere. All five data transformations were rescaled to the same covariance and submitted to a single temporal or time-frequency PCA (Varimax) to yield simplified estimates of N1 or theta/delta ERS. Unbiased nonparametric permutation tests revealed that these hemifield-dependent asymmetries were by far most focal and prominent for CSD data, despite all transformations showing maximum effects at mid-parietooccipital sites. Employing smaller subsamples (signal-to-noise) or window-based ERP/ERS amplitudes did not affect these comparisons. Furthermore, correlations between N1 and theta/delta ERS at these sites were strongest for CSD and weakest for nose-referenced data. Contrary to the common notion that the spatial high pass filter properties of a surface Laplacian reduce important contributions of neuronal generators to the EEG signal, the present findings demonstrate that instead volume conduction inherent in surface potentials weakens the representation of neuronal activation patterns at scalp that directly reflect regional brain activity.

Neural correlates of attention to emotional facial expressions in dysphoria

The present study investigated whether dysphoric individuals have a difficulty in disengaging attention from negative stimuli and/or reduced attention to positive information. Sad, neutral and happy facial stimuli were presented in an attention-shifting task to 18 dysphoric and 18 control participants. Reaction times to neutral shapes (squares and diamonds) and the event-related potentials to emotional faces were recorded. Dysphoric individuals did not show impaired attentional disengagement from sad faces or facilitated disengagement from happy faces. Right occipital lateralisation of P100 was absent in dysphoric individuals, possibly indicating reduced attention-related sensory facilitation for faces. Frontal P200 was largest for sad faces among dysphoric individuals, whereas controls showed larger amplitude to both sad and happy as compared with neutral expressions, suggesting that dysphoric individuals deployed early attention to sad, but not happy, expressions. Importantly, the results were obtained controlling for the participants' trait anxiety. We conclude that at least under some circumstances the presence of depressive symptoms can modulate early, automatic stages of emotional processing.

Electrophysiological evidence of the time course of attentional bias in non-patients reporting symptoms of depression with and without co-occurring anxiety

Anxiety is characterized by attentional biases to threat, but findings are inconsistent for depression. To address this inconsistency, the present study systematically assessed the role of co-occurring anxiety in attentional bias in depression. In addition, the role of emotional valence, arousal, and gender was explored. Ninety-two non-patients completed the Penn State Worry Questionnaire (Meyer et al., 1990; Molina and Borkovec, 1994) and portions of the Mood and Anxiety Symptom Questionnaire (Watson et al., 1995a,1995b). Individuals reporting high levels of depression and low levels of anxiety (depression only), high levels of depression and anxiety (combined), or low levels of both (control) completed an emotion-word Stroop task during event-related brain potential recording. Pleasant and unpleasant words were matched on emotional arousal level. An attentional bias was not evident in the depression-only group. Women in the combined group had larger N200 amplitude for pleasant than unpleasant stimuli, and the combined group as a whole had larger right-lateralized P300 amplitude for pleasant than unpleasant stimuli, consistent with an early and later attentional bias that is specific to unpleasant valence in the combined group. Men in the control group had larger N200 amplitude for pleasant than unpleasant stimuli, consistent with an early attentional bias that is specific to pleasant valence. The present study indicates that the nature and time course of attention prompted by emotional valence and not arousal differentiates depression with and without anxiety, with some evidence of gender moderating early effects. Overall, results suggest that co-occurring anxiety is more important than previously acknowledged in demonstrating evidence of attentional biases in depression.

Individual differences in automatic emotion regulation affect the asymmetry of the LPP component

The main goal of this study was to investigate how automatic emotion regulation altered the hemispheric asymmetry of ERPs elicited by emotion processing. We examined the effect of individual differences in automatic emotion regulation on the late positive potential (LPP) when participants were viewing blocks of positive high arousal, positive low arousal, negative high arousal and negative low arousal pictures from International affect picture system (IAPS). Two participant groups were categorized by the Emotion Regulation-Implicit Association Test which has been used in previous research to identify two groups of participants with automatic emotion control and with automatic emotion express. The main finding was that automatic emotion express group showed a right dominance of the LPP component at posterior electrodes, especially in high arousal conditions. But no right dominance of the LPP component was observed for automatic emotion control group. We also found the group with automatic emotion control showed no differences in the right posterior LPP amplitude between high- and low-arousal emotion conditions, while the participants with automatic emotion express showed larger LPP amplitude in the right posterior in high-arousal conditions compared to low-arousal conditions. This result suggested that AER (Automatic emotion regulation) modulated the hemispheric asymmetry of LPP on posterior electrodes and supported the right hemisphere hypothesis.

Cognition in late onset depression

The aim of study was to assess cognition in patients with late onset depression in a symptom-free remission period measuring event-related potentials and reaction times (RT) in a modified computer version of the Stroop test. Thirty four patients with late-onset depression were included after they had reached remission. They were compared to age-, gender- and education-matched healthy controls. Each participant completed a single item computer version of the Stroop Color-word task using verbal response mode. EEG and RT were simultaneously recorded. RTs were significantly prolonged in patients in all conditions of the Stroop paradigm, and the interference effect was significantly greater in patients compared to controls. Results also revealed abnormal late positive Stroop related potentials in the period of about 500-600 ms period corresponding to the so-called P300b wave. Our study supports the view that patients with late onset depression are also cognitively impaired and that this impairment persists in the period of early remission. Using more sensitive ERP measurement of the Stroop task we demonstrated impaired information processing at an earlier, pre-response related stage.

Auditory P3 in antidepressant pharmacotherapy treatment responders, non-responders and controls

Event-related potentials (ERPs), derived from electroencephalographic (EEG) recordings, can index electrocortical activity related to cognitive operations. The fronto-central P3a ERP is involved in involuntary processing of novel auditory information, whereas the parietal P3b indexes controlled attention processing. The amplitude of the auditory P3b has been found to be decreased in major depressive disorder (MDD). However, few studies have examined the relations between the P3b, the related P3a, and antidepressant treatment response. We tested 53 unmedicated individuals (25 females) with MDD, as well as 43 non-depressed controls (23 females) on the novelty oddball task, wherein infrequent deviant (target) and frequent standard (non-target) tones were presented, along with infrequent novel (non-target/distractor) sounds. The P3a and P3b ERPs were assessed to novel and target sounds, respectively, as were their accompanying behavioral performance measures. Depression ratings and the antidepressant response status were assessed following 12 weeks of pharmacotherapy with three different regimens. Antidepressant treatment non-responders had smaller baseline P3a/b amplitudes than responders and healthy controls. Baseline P3b amplitude also weakly predicted the extent of depression rating changes by week 12. Females exhibited larger P3a/b amplitudes than males. With respect to task performance, controls had more target hits than treatment non-responders. ERP measures correlated with clinical changes in males and with behavioral measures in females. These results suggest that greater (or control-like) baseline P3a/b amplitudes are associated with a positive antidepressant response, and that gender differences characterize the P3 and, by extension, basic attentive processes.

Neuronal generators of posterior EEG alpha reflect individual differences in prioritizing personal spirituality

Prominent posterior EEG alpha is associated with depression and clinical response to antidepressants. Given that religious belief was protective against depression in a longitudinal study of familial risk, we hypothesized that individuals who differed by strength of spiritual beliefs might also differ in EEG alpha. Clinical evaluations and self-reports of the importance of religion or spirituality (R/S) were obtained from 52 participants, and again at 10-y followup when EEG was measured. EEG alpha was quantified using frequency PCA of current source densities (CSD-fPCA). Participants who rated R/S as highly important at initial assessment showed greater alpha compared to those who did not. Those who rated R/S important in both sessions showed greater alpha than those who changed their ratings. EEG differences were particularly well-defined for participants with lifetime depression. Findings extend the view of alpha as a marker for affective processes, suggesting an association with the ontogenesis of spirituality.

Distinct modulation of event-related potentials during motor preparation in patients with motor conversion disorder

Objective

Conversion paresis patients and healthy people feigning weakness both exhibit weak voluntary movement without detectable neuropathology. Uniquely, conversion patients lack a sense of conscious awareness of the origin of their impairment. We investigated whether conversion paresis patients show distinct electroencephalographic (EEG) markers associated with their unconscious movement deficits.

Methods

Six unilateral upper limb conversion paresis patients, 12 feigning participants asked to mimic weakness and 12 control participants performed a precued reaction time task, requiring movements of either hand, depending on precue information. Performance measures (force, reaction and movement time), and event-related EEG potentials (ERP) were compared, between groups and across hands or hemisphere, using linear mixed models.

Results

Feigners generated the same inter-hand difference in reaction and movement time as expressed by patients, even though no specific targets were set nor feedback given on these measures. We found novel ERP signatures specific to patients. When the symptomatic hand was precued, the P3 ERP component accompanying the precue was dramatically larger in patients than in feigning participants. Additionally, in patients the earlier N1 ERP component was diminished when the precue signalled either the symptomatic or asymptomatic hand.

Conclusions

These results are consistent with previous suggestions that lack of awareness of the origin of their symptoms in conversion disorder patients may result from suppression of brain activity normally related to self-agency. In patients the diminished N1 to all precues is consistent with a generalised reduction in cognitive processing of movement-related precues. The P3 enhancement in patients is unlikely to simply reflect changes required for generation of impaired movements, because it was not seen in feigners showing the same behavioural deficits. Rather, this P3 enhancement in patients may represent a neural biomarker of unconscious processes, including additional emotional loading, related to active suppression of brain circuits involved in the attribution of self-agency.

Using the high-risk family design to identify biomarkers for major depression

The familial nature of major depressive disorder (MDD) is now well recognized. We followed children and grandchildren of probands with and without MDD to examine transmission of depression over generations, and to identify early vulnerability markers prior to the onset of disease. The study now includes three generations and five completed assessment waves spanning 25 years, with a sixth wave underway. Beginning with the fourth wave, we collected measures of brain structure (magnetic resonance imaging, MRI) and physiology (electroencephalography, EEG) and DNA in order to examine at a biological level why the offspring of depressed parents were at higher risk. In this paper, we provide an overview of the study design, the main findings, including new data, and the role of the high-risk design in translational research. We demonstrate that offspring of depressed parents ('high-risk'), when compared with those of non-depressed parents ('low-risk'), were at increased risk for depressive and anxiety disorders, with anxiety appearing earlier and being a predisposing factor for MDD. Offspring with two generations previously affected were at greatest risk. Thinning of the cortical mantle (MRI) and reduced resting-state activity (EEG) within the right parieto-temporal hemisphere differentiated high- from low-risk offspring, regardless of whether the offspring had MDD, suggesting that these measures might serve as familial trait markers for depression and related syndromes. The high- and low-risk offspring also differed by serotonin transporter promoter length polymorphism genotypes, even though the same genotypes were not associated with the presence of MDD. The high-risk epidemiological design appears to be a particularly valuable asset in translational research as it allows targeting of biological processes that emerge prior to the onset of disease, and identifies individuals at high risk for the disorder who may carry the trait or marker but not yet be affected.

Emotional processing modulates attentional capture of irrelevant sound input in adolescents

The main goal of this study was to investigate how emotional processing modulates the allocation of attention to irrelevant background sound events in adolescence. We examined the effect of viewing positively and negatively valenced video clips on components of event-related brain potentials (ERPs), while irrelevant sounds were presented to the ears. All sounds evoked the P1, N1, P2, and N2 components. The infrequent, randomly occurring novel environmental sounds evoked the P3a component in all trial types. The main finding was that the P3a component was larger in amplitude when evoked by salient, distracting background sound events when participants were watching negatively charged video clips, compared to when viewing of the positive or neutral video clips. The results suggest that the threshold for involuntary attention to the novel sounds was lowered during viewing of the negative movie contexts. This indicates a survival mechanism, which would be needed for more automatic processing of irrelevant sounds to monitor the unattended environment in situations perceived as more threatening.

Measuring affective reactivity in individuals with autism spectrum personality traits using the visual mismatch negativity event-related brain potential

The primary aim of this research was to determine how modulation of the visual mismatch negativity (vMMN) by emotionally laden faces is related to autism spectrum personality traits. Emotionally neutral faces served as the standard stimuli and happy and sad expressions served as vMMN-eliciting deviants. Consistent with prior research, it was anticipated that the amplitude of the vMMN would be increased for emotionally salient stimuli. Extending this finding, it was expected that this emotion-based amplitude sensitivity of the vMMN would be decreased in individuals with higher levels of autism spectrum personality traits as measured by the Adult Autism Spectrum Quotient (AQ). Higher AQ scores were associated with smaller amplitudes of the vMMN in response to happy, but not sad emotional deviants. The fact that higher AQ scores were associated with less sensitivity only to happy emotional expressions is interpreted to be consistent with the negative experience of social interactions reported by individuals who are high on the autism spectrum. This research suggests that the vMMN elicited by deviant emotional expressions may be a useful indicator of affective reactivity and may thus be related to social competency in Autism Spectrum Disorder (ASD).

Relationship of resting EEG with anatomical MRI measures in individuals at high and low risk for depression

Studies have found abnormalities of resting EEG measures of hemispheric activity in depressive disorders. Similar EEG findings and a prominent thinning of the cortical mantle have been reported for persons at risk for depression. The correspondence between EEG alpha power and magnetic resonance imaging (MRI) measures of cortical thickness was examined in a multigenerational study of individuals at risk for depression. Seventy-five participants underwent resting EEG and approximately 5 years later underwent MRI scanning. High-risk participants (n = 37) were biological descendants of probands having major depression and low-risk participants (n = 38) were descendants of individuals without a history of depression. EEG alpha power was interpolated across the surface of a template brain and coregistered with measures of cortical thickness. Voxel-wise correlations of cortical thickness and alpha power were computed while covarying for age and gender. The high-risk group, when compared to the low-risk group, showed greater alpha asymmetry in an eyes-closed condition, with relatively less activity over right parietal cortex. Alpha power correlated inversely with cortical thickness, particularly over the right posterior region, indicating that EEG evidence of reduced cortical activity was associated with increased cortical thinning. This is the first report of widespread correlation of EEG alpha activity with MRI measures of cortical thickness. Although both EEG and MRI measures are associated with risk for depression, we did not detect evidence that cortical thickness mediated the alpha asymmetry findings. Thus, alpha asymmetry, alone or in combination with MRI, may be a marker of vulnerability for a familial form of depression.

Abnormal functional brain asymmetry in depression: evidence of biologic commonality between major depression and dysthymia

Prior studies have found abnormalities of functional brain asymmetry in patients having a major depressive disorder (MDD). This study aimed to replicate findings of reduced right hemisphere advantage for perceiving dichotic complex tones in depressed patients, and to determine whether patients having "pure" dysthymia show the same abnormality of perceptual asymmetry as MDD. It also examined gender differences in lateralization, and the extent to which abnormalities of perceptual asymmetry in depressed patients are dependent on gender. Unmedicated patients having either a MDD (n=96) or "pure" dysthymic disorder (n=42) and healthy controls (n=114) were tested on dichotic fused-words and complex-tone tests. Patient and control groups differed in right hemisphere advantage for complex tones, but not left hemisphere advantage for words. Reduced right hemisphere advantage for tones was equally present in MDD and dysthymia, but was more evident among depressed men than depressed women. Also, healthy men had greater hemispheric asymmetry than healthy women for both words and tones, whereas this gender difference was not seen for depressed patients. Dysthymia and MDD share a common abnormality of hemispheric asymmetry for dichotic listening.

The temporal electrocortical profile of emotive facial processing in depressed males and females and healthy controls

BACKGROUND

Previous work indicates that emotive processing, such as of facial expressions, may be altered in major depressive disorder (MDD). Individuals with MDD tend to exhibit a mood-congruent processing bias, though MDD may also be characterized by blunted emotive processing in general. Females tend to exhibit enhanced facial emotive processing than males. Few groups have examined the temporal electrophysiological event-related potential (ERP)-indexed profiles, spanning preconscious to sustained, conscious processing of facial expressions in MDD; systematic comparisons of ERPs to emotive stimuli between depressed males and females are also lacking.

METHODS

This study examined the temporal ERP profile to a simple expression recognition task in depressed adult males and females (N=52; 29 females) and controls (N=43; 23 females).

RESULTS

The MDD group rated facial expressions as sadder overall than controls. Females exhibited enhanced and speeded pre- and conscious face processing than males. Subtle group differences emerged to specific expressions at mid-latency ERPs (N2, P2) indicating both blunted late pre-conscious perceptual processing of expressions and prolonged processing of intensely sad faces.

LIMITATIONS

A more involved emotive processing task, employing threatening faces, may have revealed more robust group ERP differences. Menstrual cycle should also be controlled for in future work.

CONCLUSIONS

This is the first study to systematically assess the temporal ERP profile, including of ERPs preceding the face-sensitive N170/VPP, to expressions in MDD. Overall, early perceptual and late conscious expression processing did not differ fundamentally between groups. Altered emotive processing may be a candidate index for monitoring and predicting antidepressant treatment outcome.

Electrocortical reactivity to emotional faces in young children and associations with maternal and paternal depression

BACKGROUND

The late positive potential (LPP) is an event-related potential component that indexes selective attention toward motivationally salient information and is sensitive to emotional stimuli. Few studies have examined the LPP in children. Depression has been associated with reduced reactivity to negative and positive emotional stimuli, including reduced LPPs in response to emotional faces. The current study sought to identify the time course and scalp distribution of the LPP in response to emotional faces in young children and to determine whether reduced reactivity is observed among children at risk for depression.

METHODS

Electrocortical reactivity to emotional faces was examined in a large sample of young children and as a function of maternal and paternal depression.

RESULTS

In the overall sample, emotional faces were associated with increased positivities compared to neutral faces at occipital sites 200-600 ms after stimulus onset and at parietal sites 600-1,000 ms after stimulus onset. Children of mothers with a history of depressive disorders exhibited reduced differentiation in the early occipital LPP for emotional compared to neutral faces.

CONCLUSIONS

Results suggest that children as young as 6 years exhibit LPPs to emotional faces, and patterns of electrocortical reactivity to emotional stimuli may be associated with vulnerability to depressive disorders.

Dopaminergic mechanisms of target detection - P300 event related potential and striatal dopamine

The P300 is a cortically generated event related potential (ERP) widely used in neurophysiological research since it is related to cognitive functions and central information processing. Intracerebral recordings and functional neuroimaging studies have demonstrated that this potential is generated by various brain regions including frontal, temporal and parietal cortices. Regarding the neurochemical background, clinical and genetic investigations suggest that dopaminergic neurons could be involved in the generation of the P300. However, there is no direct evidence in vivo that P300 amplitudes and latencies are related to dopaminergic parameters. The aim of this study was to further elucidate dopaminergic aspects of the P300 ERP by combining neurophysiological and nuclear medicine assessments in vivo. Patients with a major depressive episode underwent both P300 recordings and dynamic [¹²³I] IBZM SPECT for the evaluation of striatal dopamine D₂/D₃-receptor availability. There were statistically significant positive correlations of the striatal dopamine D₂/D₃-receptor status with P300 amplitudes and significant negative correlations with P300 latencies. Using this combined approach, the study presents direct evidence in vivo that the central dopaminergic system might play an important role in the generation of the P300 and that central dopaminergic activity could be involved in the modulation of P300 parameters. This association might be of relevance for the interpretation of P300 studies in psychiatric disorders.

Dysfunction of fronto-limbic brain circuitry in depression

BACKGROUND

depression is characterized by a stable negative bias toward emotional stimuli. This bias is associated with abnormal activities in emotion-processing regions (such as the amygdala) and cognitive-control regions (such as the dorsolateral prefrontal cortex [DLPFC]). However, it remains unclear whether the emotion-processing and cognitive-control regions affect negative cognitive bias independently or reciprocally.

EXPERIMENTAL PROCEDURE

a functional magnetic resonance imaging (fMRI) study of 16 depressed patients and 16 matched control subjects was conducted during an emotion-interference task.

RESULTS

the accuracies were significantly lower in the depressed group than in the control group when subjects attended to the happy and the neutral faces. Compared with control participants, depressed patients showed abnormal activity in bilateral amygdala and the right DLPFC. In addition, a significant correlation was found between the right amygdala and the right DLPFC when subjects observed the happy faces.

CONCLUSIONS

the results suggest that the dysfunction in positive emotion-processing and cognitive-control regions may reciprocally affect negative cognitive bias. Additionally, altered positive emotional interference processing in the fronto-limbic brain circuitry might be another cause of negative cognitive bias that finally leads to depression.

Do positive and negative temperament traits interact in predicting risk for depression? A resting EEG study of 329 preschoolers

Researchers have long been interested in whether particular temperamental traits in childhood connote risk for depressive disorders. For example, children characterized as having high negative emotionality (NE; sadness, fear, anger) and low positive emotionality (PE; anhedonia, listlessness, and lack of enthusiasm) are hypothesized to be at risk for depression. Few studies, however, have examined whether (and how) these two temperamental dimensions interact to confer risk. In a sample of 329 preschoolers, the present study addressed this question by examining the relation between PE and NE and asymmetry in resting EEG activity in frontal and posterior regions, which are putative biomarkers for depression. Using a laboratory battery to define temperament, we found an interaction of PE and NE on posterior asymmetry. Specifically, when PE was high, NE was associated with greater relative right activity. When PE was low, NE was not related to posterior asymmetry. These results were driven by differences in EEG activity in right posterior regions, an area associated with emotional processing and arousal, and were specific to girls. We found no relation between temperament and frontal asymmetry. These findings suggest that, at least for girls, PE and NE may have an interactive effect on risk for depression.

The Effects of Valence and Arousal on Hemispheric Asymmetry of Emotion

The independent influence of valence and arousal on emotional hemispheric brain asymmetry was investigated to decide between three contrasting hypotheses: the right hemisphere hypothesis, the valence hypothesis, and the integrative hypothesis. Event-related potentials (ERPs) were recorded while participants (N = 20) viewed positive high arousal, positive low arousal, negative high arousal, and negative low arousal pictures, following a baseline measure of ERPs while viewing gray squares. Self-ratings of emotional state in terms of valence and arousal were taken after each of the four emotion blocks. Valence and arousal effects on hemispheric asymmetry were analyzed for the time windows 130–170, 170–280, 280–450, and 450–600 ms. Right dominance on N2 during negative high arousal and left dominance on P3 and late positive potentials during negative low arousal were found over the frontal lobe. Right dominance on P2, P3, and late positive potentials over the parietal lobes appeared during high arousal. No frontal asymmetry was found in positive emotion. Our result partly supported the integrative hypothesis and did not provide evidence for the right hemisphere hypothesis or the valence hypothesis. These results suggested that arousal plays the main role in the ERPs’ hemispheric asymmetry.

The oft-neglected role of parietal EEG asymmetry and risk for major depressive disorder

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.

Time course of affective processing bias in major depression: An ERP study

The current study investigated the time course of the affective processing bias in major depressive disorder (MDD) in a visual three-stimulus semantic oddball task using event-related potentials (ERPs). MDD patients showed decreased P1 latency over right posterior regions to negative relative to positive target stimuli, reflecting a very early onset of the negativity bias in emotional perception. Compared to controls, MDD patients showed enlarged anterior P2 amplitude to positive target stimuli, reflecting an affective bias in the early attentional stages of processing. In addition, MDD patients showed relatively high N2 and reduced P3 amplitudes to negative compared with positive target stimuli, as well as marginally reduced N2 amplitude to positive target stimuli compared with controls. This suggests that the negativity bias also occurs during later strategic evaluation stages. Therefore, the present study extended previous findings by demonstrating that the affective processing bias in MDD begins in the early stages of perceptual processing and continues at later cognitive stages.

Early processing of threat cues in posttraumatic stress disorder-evidence for a cortical vigilance-avoidance reaction

BACKGROUND

The present study investigated the influence of posttraumatic stress disorder (PTSD) on early visual processing of affective stimuli in survivors of war and torture.

METHODS

Trauma-exposed refugees with (n = 36) and without (n = 21) PTSD as well as unexposed control subjects (n = 16) participated in a magnetoencephalography study with pictures that varied in emotional content.

RESULTS

We found evidence for a biphasic cortical response in patients with PTSD in comparison with the two control groups. In response to aversive (relative to neutral or positive) pictures, PTSD patients showed elevated cortical activity over right prefrontal areas as early as 130-160 msec after stimulus onset followed by a decrease of the affect-related response in the parieto-occipital cortex at 206-256 msec.

CONCLUSIONS

The increased early activity in the right prefrontal cortex most likely represents an enhanced alarm response or the fear network toward aversive stimuli in PTSD, whereas the subsequent decreased activation in right parieto-occipital areas in response to aversive pictures seems to reflect the tendency to disengage from emotional content. This finding is consistent with the hypothesis of a vigilance-avoidance reaction pattern to threat in anxiety disorders and helps to reconcile contradicting results of over- and under-responsiveness in the sensory processing of threatening stimuli in PTSD.

Electrocortical effects of acute tryptophan depletion on emotive facial processing in depression-prone individuals

This study assessed the effects of acute tryptophan depletion (ATD), which transiently lowers CNS 5-HT, on electrocortical responses to facial expression processing in individuals with a family history of depression (FH+). Electroencephalograph (EEG)-derived event-related potentials (ERPs) were acquired from 18 FH+ individuals during a facial expression recognition task (neutral and sad, joy and surprise at 50% and 100% intensities). Both early positive (P1 and P2) and the face-specific N170 ERP components were differentially altered by emotional intensity and valence. Increased depression, confusion and total mood disturbance scores, and decreased calmness, were observed with ATD (versus placebo). ATD was also associated with enhanced P1 and P2 amplitudes for sad versus joyful expressions. The N170 was not modulated by treatment, but was affected by emotive valence. Therefore, ATD enhanced ERP-indexed early processing of sad facial expressions, and altered the processing of positive ones, in FH+ individuals.

Inhibition dysfunction in depression: event-related potentials during negative affective priming

The study aimed to investigate whether depressed patients show impairment of valence-dependent inhibition and its neurophysiological correlates. Event-related potentials (ERPs) were collected from 18 patients with unipolar depression and 18 normal controls during an affective negative priming task. A less effective inhibition in patients was specific for negative information. These behavioral effects were paralleled by ERP differences. In addition to the overall reduced P2 amplitude for negative trials and the overall reduced late positive component (LPC) amplitude for positive and negative trials in patients, ERP differences in different conditions for each group were also found. The patients showed reduced central-parietal P2 amplitude and shorter LPC latency in response to negative experimental targets, whereas the controls showed larger left central P2 amplitude and delayed LPC latency in response to negative experimental targets. No such effects were found for positive targets. These results suggest that the inhibition dysfunction of negative affect influences the earlier attention allocation stage and the later evaluation stage in depressed patients.

Time course of attentional bias in anxiety: emotion and gender specificity

Anxiety is characterized by cognitive biases, including attentional bias to emotional (especially threatening) stimuli. Accounts differ on the time course of attention to threat, but the literature generally confounds emotional valence and arousal and overlooks gender effects, both addressed in the present study. Nonpatients high in self-reported anxious apprehension, anxious arousal, or neither completed an emotion-word Stroop task during event-related potential (ERP) recording. Hypotheses differentiated time course of preferential attention to emotional stimuli. Individuals high in anxious apprehension and anxious arousal showed distinct early ERP evidence of preferential processing of emotionally arousing stimuli along with some evidence for gender differences in processing. Healthy controls showed gender differences at both early and later processing stages. The conjunction of valence, arousal, and gender is critical in the time course of attentional bias.

Neuropsychological and interpersonal antecedents of youth depression

This research examined neuropsychological and interpersonal factors that jointly confer vulnerability to youth depression. We proposed that (1) a reduced posterior right hemisphere bias during the processing of facial expressions contributes to subsequent depressive symptoms in youth, and (2) maladaptive responses to interpersonal stress account for this association. Drawing from theory and research indicating sex differences in rates of hemispheric development, we also investigated sex differences in the associations among a reduced posterior right hemisphere bias, maladaptive responses to interpersonal stress, and depressive symptoms. Hypotheses were examined in a longitudinal study of 95 4^th - 8^th graders (M age = 12.33, SD = 1.10). Results supported the notion that a reduced posterior right hemisphere bias confers vulnerability to depressive symptoms over time in a sex-specific fashion, and implicate maladaptive stress responses as an explanatory mechanism.

Emotional facilitation effect in the picture-word interference task: an ERP study

In this paper, we aimed to verify the emotional facilitation effect in the picture-word interference task using event-related potentials. Twenty-one healthy subjects were asked to categorize the emotional valences of pictures accompanied by emotionally congruent, either centrally or laterally positioned Chinese words. For both the foveal and lateral word presentations, the reaction times were faster compared to the picture-only presentation. Compared to the picture-only presentation, P200 amplitude increased under the foveal word presentation condition and decreased under the lateral word presentation condition, indicating that more attentional resources were required when an accompanying word was in the center of a picture than when the word was in the lateral position. Latency of P300 was shorter in response to picture-word stimuli irrespective of word position, indicating that an emotionally congruent word facilitated the emotional processing of the target picture, which verified the emotional facilitation effect and was consistent with the results in psychology. The late positive component was more positive when the picture-word stimuli were more positive, which reflected the feature of positivity offset. The findings suggest that the time window for an emotional facilitation effect may be limited to processing aspects associated with P300 (i.e., affective evaluation).

Evidence for modulation of facial emotional processing bias during emotional expression decoding by serotonergic and noradrenergic antidepressants: an event-related potential (ERP) study

RATIONALE

Serotonergic (SSRI) and noradrenergic (NRI) antidepressants modulate biases in emotional processing such that perceptual bias is shifted away from negative and towards positive emotional material. However, the effects of serotonergic and noradrenergic modulation on the temporal course (occurring in milliseconds) of emotional processing, and in particular, the rapid physiological changes associated with the different stages of emotional processing, are unknown.

OBJECTIVE

The current study assessed the effects of acute serotonergic (i.e. with citalopram) and noradrenergic (i.e. with reboxetine) augmentation on event-related potential (ERP) measures associated with 'structural encoding' (N170) and emotion expression decoding (N250 and late positive potential [LPP]) for positive (happy) and negative (sad) facial stimuli relative to neutral facial stimuli.

MATERIALS AND METHODS

This study employed a double-blind, placebo-controlled, cross-over design in which 12 healthy male participants completed a facial expression recognition task tested under three acute conditions: (a) placebo, (b) citalopram (20 mg) and (c) reboxetine (4 mg).

RESULTS

Both citalopram and reboxetine had no effect on the N170 ERP component associated with structural encoding, but potentiated the N250 associated with happy (relative to neutral) emotional facial expression decoding. Both drugs had no valence effects on later ERP measures of emotion expression decoding (LPP).

CONCLUSIONS

Citalopram and reboxetine have selective effects on the temporal course of emotional processing with evidence to suggest specific effects on emotion expression decoding of positive (happy) emotional facial stimuli as evidenced by changes in the attention-modulated N250 but not structural encoding. These findings provide physiological evidence that antidepressants may shift perceptual biases in emotional processing away from negative and towards positive stimuli.

Visual processing of emotional expressions in mixed anxious-depressed subclinical state: an event-related potential study on a female sample

AIMS

Controversy remains about the existence and the nature of a specific bias in emotional facial expression processing in mixed anxious-depressed state (MAD).

MATERIAL AND METHODS

Event-related potentials were recorded in the following three types of groups defined by the Spielberger state and trait anxiety inventory (STAI) and the Beck depression inventory (BDI): a group of anxious participants (n=12), a group of participants with depressive and anxious tendencies (n=12), and a control group (n=12). Participants were confronted with a visual oddball task in which they had to detect, as quickly as possible, deviant faces amongst a train of standard neutral faces. Deviant stimuli changed either on identity, or on emotion (happy or sad expression).

RESULTS

Anxiety facilitated emotional processing and the two anxious groups produced quicker responses than control participants; these effects were correlated with an earlier decisional wave (P3b) for anxious participants. Mixed anxious-depressed participants showed enhanced visual processing of deviant stimuli and produced higher amplitude in attentional complex (N2b/P3a), both for identity and emotional trials. P3a was also particularly increased for emotional faces in this group.

CONCLUSION

Anxious state mainly influenced later decision processes (shorter latency of P3b), whereas mixed anxious-depressed state acted on earlier steps of emotional processing (enhanced N2b/P3a complex). Mixed anxious-depressed individuals seemed more reactive to any visual change, particularly emotional change, without displaying any valence bias.

Effects of nicotine and depressive traits on affective priming of lateralized emotional word identification

Based on evidence suggesting that depressive traits, emotional information processing, and the effects of nicotine may be mediated by lateralized brain mechanisms, analyses assessed the influence of depressive traits and nicotine patch on emotional priming of lateralized emotional word identification in 61 habitual smokers. Consistent with hypotheses, nicotine as compared to placebo patch enhanced right visual field (RVF) emotional word identification while decreasing performance of emotional word identification in the left visual field (LVF). Nicotine also enhanced positive affect and decreased negative affect. Consistent with the Heller model of depression, scoring high in depressive traits was associated with a general decrease in LVF emotional word identification. Additionally, this general LVF deficit was especially pronounced for positive word identification in individuals scoring high in trait depression. Positive primes facilitated positive target identification in the RVF and negative primes facilitated negative target identification in the LVF. Thus, nicotine promoted a LVF word-identification deficit similar to that observed in those with depressive traits. However, nicotine also enhanced RVF processing and reduced negative affect, whereas it enhanced positive affect.

Alcoholism leads to early perceptive alterations, independently of comorbid depressed state: an ERP study

INTRODUCTION

Alcoholism is associated with a deficit in the processing of emotional facial expressions (EFE) and with a delayed P3b component, partially mediated by earlier perceptive deficits (P100, N170). Since alcohol dependence often occurs with depression, we aim at investigating whether classical event-related potentials (ERP) alterations observed in alcoholism are modulated or not by depression.

METHODS

Four groups (controls; alcoholics; depressed; alcoholics-depressed) of 12 participants performed two different discrimination tasks, a gender and an emotional one. They had to decide as quickly as possible about the gender or the emotion displayed by facial stimuli during an ERP recording session (32 channels). Reaction times (RTs), P100, N100, N170 and P3b were recorded.

RESULTS

At the behavioural level, control participants discriminated EFE (but not gender) more rapidly than the three other groups. At the ERP level, the differences observed on RTs for emotional task were neurophysiologically indexed by a delayed P3b component. This delay was associated with earlier ERP alterations (P100, N100, N170), but only in participants suffering from alcohol dependence, in association or not with depression.

DISCUSSION

On the one hand, individuals with alcoholism, associated or not with a comorbid depression, were impaired in the processing of EFE. This deficit was neurophysiologically indexed by early perceptive (P100, N100, N170) and decisional (P3b) alterations. On the other hand, non-alcoholic patients with depression only exhibited P3b impairment. These results lead to potential implications concerning the usefulness of the ERP for the differential diagnosis in psychiatry, notably concerning the comorbidities in alcoholism.

Hemispatial PCA dissociates temporal from parietal ERP generator patterns: CSD components in healthy adults and depressed patients during a dichotic oddball task

Event-related potentials (31-channel ERPs) were recorded from 38 depressed, unmedicated outpatients and 26 healthy adults (all right-handed) in tonal and phonetic oddball tasks developed to exploit the perceptual challenge of a dichotic stimulation. Tonal nontargets were pairs of complex tones (corresponding to musical notes G and B above middle C) presented simultaneously to each ear (L/R) in an alternating series (G/B or B/G; 2-s fixed SOA). A target tone (note A) replaced one of the pair on 20% of the trials (A/B, G/A, B/A, A/G). Phonetic nontargets were L/R pairs of syllables (/ba/, /da/) with a short voice onset time (VOT), and targets contained a syllable (/ta/) with a long VOT. Subjects responded with a left or right button press to targets (counterbalanced across blocks). Target detection was poorer in patients than controls and for tones than syllables. Reference-free current source densities (CSDs; spherical spline Laplacian) derived from ERP waveforms were simplified and measured using temporal, covariance-based PCA followed by unrestricted Varimax rotation. Target-related N2 sinks and mid-parietal P3 sources were represented by CSD factors peaking at 245 and 440 ms. The P3 source topography included a secondary, left-lateralized temporal lobe maximum for both targets and nontargets. However, a subsequent hemispheric spatiotemporal PCA disentangled temporal lobe N1 and P3 sources as distinct factors. P3 sources were reduced in patients compared with controls, even after using performance as a covariate. Results are consistent with prior reports of P3 reduction in depression and implicate distinct parietal and temporal generators of P3 when using a dichotic oddball paradigm.

Grandchildren at high and low risk for depression differ in EEG measures of regional brain asymmetry

BACKGROUND

Electrophysiologic studies have found abnormalities of alpha asymmetry in depressed adults and offspring of depressed parents, which have been hypothesized to be vulnerability markers of depression. Resting electroencephalogram (EEG) was measured in grandchildren participating in a multigenerational high-risk study.

METHODS

Electroencephalogram from 12 electrodes at six homologous sites over each hemisphere (digitally linked-ears reference) was compared in right-handed grandchildren in three groups: 1) both parent and grandparent having major depressive disorder (MDD; n = 19); 2) either parent or grandparent having MDD (n = 14); and 3) neither having MDD (n = 16).

RESULTS

Grandchildren with both depressed parent and grandparent showed greater alpha asymmetry, with relatively less right than left hemisphere activity, when compared with those with neither depressed parent nor grandparent. This difference was present over the parietal region in the eyes-closed condition. Grandchildren having either depressed parent or grandparent also tended to show heightened alpha asymmetry at parietal sites, but they did not differ significantly from those with neither depressed parent nor grandparent. Low-risk grandchildren with neither depressed parent nor grandparent showed no significant alpha asymmetry.

CONCLUSIONS

High-risk grandchildren displayed a parietal alpha asymmetry similar to that seen in adolescents or adults having a MDD and in second-generation offspring of parents concordant for MDD. Its presence in high-risk offspring and grandchildren without a lifetime history of MDD supports the hypothesis that an alpha asymmetry indicative of relatively less right than left parietal activity is an endophenotypic marker of vulnerability to a familial form of major depression.

Heartbeat perception and P300 amplitude in a visual oddball paradigm

OBJECTIVE

The perception of bodily signals ("interoceptive awareness") was found to modulate evoked potential components, especially the P300, in response to emotional pictures and to internal signals. It remains an open question whether this variable is related to more elaborated information processing in general.

METHODS

The present study investigated the relationship between heartbeat perception and the amplitude of the P300 to target stimuli in a visual oddball paradigm.

RESULTS

Interoceptive awareness was positively correlated with the P300 amplitude at Cz which remained significant after controlling for anxiety differences.

CONCLUSIONS

Our results demonstrate a positive relationship between interoceptive awareness and the attentive processing of visual stimuli.

SIGNIFICANCE

Interoception is related to more elaborated information processing in general. This effect could be mediated by arousal differences and might rely on common neuroanatomical structures.

Spatial frequencies or emotional effects?

The influence of the emotional attributes of a visual scene on early perception processes remains a key question in contemporary affective neurosciences. The International Affective Picture System (IAPS; Lang et al., 2005) was developed to provide a set of standardized stimuli for experimental investigations of emotional processes. These stimuli have been widely used in brain activity investigations to study the influence of valence and/or arousal on visual processing. However, visual perception is strongly influenced by the physical properties of the images shown, especially their spatial frequency content, an aspect that has been unexpectedly neglected at large. In this study, we examine the complete set of IAPS with a discrete wavelet transform to highlight relations between the energy in different spatial frequencies and the emotional features of the pictures. Our results showed that these associations are weak when the complete dataset is considered, but for selected subsets of pictures, clear differences are present in both affective and spatial frequency content. The IAPS remains a powerful tool to explore emotional processing, but we strongly suggest that researchers use subsets of images that are controlled for the energy of their spatial frequencies when investigating emotional influence on visual processing.

P300 is enhanced in responders to vagus nerve stimulation for treatment of major depressive disorder

BACKGROUND

Vagus nerve stimulation (VNS) is a new therapy option for treatment of otherwise therapy-refractory major depressive disorder. However, the mechanism of central nervous action is poorly understood. Electroencephalographic (EEG) studies may be of interest since chronic peripheral current application to the vagus nerve may exert lasting neurophysiologically detectable effects on central electrical activity. In an exploratory study, we investigated the effects of VNS on auditory event-related potentials (ERP).

METHODS

Thirteen depressive patients (mean Hamilton depression score (HAMD) at baseline=24.2) receiving VNS were investigated prior to implantation and 10 weeks after standard cycling VNS. Stimulation intensity was 0.94+/-0.46 mA, pulse width 0.250 mus, and frequency 20 Hz. 1 h prior to follow-up investigation, VNS was turned off. Auditory ERP were elicited using a standard auditory oddball paradigm and were recorded with 29-channel EEG.

RESULTS

Post VNS, grand averages of the auditory ERP did not show significant differences as compared to baseline recording. However, differential effects were found when separating ERP of responders (N=5, mean HAMD post VNS=8.8) and non-responders (N=8, mean HAMD post VNS=22.4). In VNS responders only, P300 at midline electrodes Fz and Cz was significantly increased and correlated with HAMD scores.

CONCLUSION

Auditory ERP seem to provide a useful tool for investigating VNS-induced changes concerning information processing in major depressive disorder. In our sample, enhancement of P300 distinguished VNS responders from non-responders 10 weeks after therapy onset. Our findings may be relevant for the understanding of both neurophysiological mechanism of action of VNS and pathophysiology of depression.

Perceptual asymmetry and youths' responses to stress: Understanding vulnerability to depression

This research examined the hypothesis that reduced posterior right hemisphere activity interferes with the regulation of emotions and behavior in response to stress, creating vulnerability to depression. Consistent with a diathesis-stress model, we predicted that youth with a reduced posterior right hemisphere bias in emotional processing would engage in less adaptive responses to stress, which would be associated with depressive symptoms in those who reported the recent experience of high, but not low, levels of stress. Participants were 510 4^th through 8^th graders who completed the Chimeric Faces Task and measures of responses to stress and depressive symptoms. Results supported the idea that responses to stress account for the association between reduced posterior right hemisphere activity and depressive symptoms in youth who report high, but not low, levels of stress. This study provides insight into one process through which reduced posterior right hemisphere activity may confer vulnerability to depressive symptoms, and implicates responses to stress as a target for intervention.

Genes mediate the association between P3 amplitude and externalizing disorders

Reduced P3 amplitude has been consistently linked to a spectrum of externalizing disorders. Utilizing data from a large sample of adolescent male twins (N=1196), we used biometric modeling to assess the genetic and environmental contributions to the association between reduced P3 amplitude and a general vulnerability to externalizing disorders. Externalizing vulnerability was indexed by a composite of symptoms of conduct disorder, adult antisocial behavior, and alcohol, nicotine, and drug dependence. The sample included two independent age cohorts, providing an internal replication of the findings. For the best-fitting model, genetic influences alone accounted for the association between P3 amplitude and externalizing disorders, with an estimated genetic correlation of r(g)=-.22. Results replicated across the two age cohorts and demonstrate that reduced P3 amplitude is a marker of the biological vulnerability to externalizing disorders.

Event Related Potentials (Erp) and Behavioral Measurements to Verbal Stimulation of Visual Fields

Event related potentials (ERP) to visually presented linguistic stimuli were examined using a lexical-decision task and an oddball paradigm. Stimuli were presented to the central, right or left visual fields (CVF, RVF and LVF) and generated ERP with very clear N100-P300 components. The question addressed was whether there is ERP evidence for left hemisphere (LH) superiority in linguistic discrimination as reported behaviorally. Nineteen young, right-handed male subjects participated. The main factor influencing the latency and amplitude of N100 was that of contralateral versus ipsilateral stimulation. Shorter N100 latency and larger amplitude were recorded over the hemisphere contralateral to the visual field stimulated. In contrast, the factors influencing the P300 parameters were the visual field stimulated and the hemisphere over which the ERP was recorded. P300 amplitude was significantly larger and P300 latency significantly shorter over the LH than over the RH. Significantly shorter P300 latency and larger peak amplitude were found for RVF than for LVF stimulation.

Abnormal asymmetry of N200 and P300 event-related potentials in subclinical depression

Sex differences for depression in prevalence and symptom profile may in part be due to differences between men and women in brain dysfunction associated with the disorder. Changes in event-related potential (ERP) measures similar to those seen in clinical populations are reported in subclinical or premorbid forms of depression. The current study investigates sex differences in ERPs associated with subclinical depression. One-hundred-and-forty healthy, right-handed adults (aged 20-60 years; screened to exclude clinical depression and psychosis) completed an auditory oddball task and the Depression Anxiety and Stress Scale (DASS). Seventy (n = 35 men) subclinically depressed (SD) (i.e. scoring >2 for depression on DASS) participants were matched for age and education with 70 (n = 35 men) participants showing no signs of depression (ND). Repeated measures multivariate analysis of variance was used to test for differences in N200 and P300 amplitude between SD and ND groups. ND, but not SD groups had asymmetry (R > L) of central N200 amplitude. Similar asymmetry was seen in ND, but not SD men at posterior sites. SD groups demonstrated left > right posterior P300 amplitude asymmetry due to P300 enhancement at left temporoparietal sites. Results support involvement of various cognitive mechanisms measured by P300 and N200 in subclinical depressive symptoms some of which may rely on sex.