Impact of depression heterogeneity on attention: an auditory oddball event related potential study

The effects of deep TMS on purpose in life, quantitative EEG and event-related potentials in major depressive disorder

BACKGROUND

Perceived purpose in life (PIL) is linked with many vital health outcomes, including Major Depressive Disorder (MDD).

METHODS

In this study, biomarkers associated with depression and PIL were investigated using Brain Network Activation (BNA) based quantitative electroencephalography (QEEG) and event-related potential (ERP) measures in a sample of individuals with MDD. Data were analyzed before and after a 36-session, Deep transcranial magnetic stimulation (TMS) program.

RESULTS

At baseline, the study observed that increased slow-frequency resting-state activity in the frontal and temporal regions correlated with higher levels of depression and reduced PIL. Additionally, a reduced P3b amplitude was found to predict elevated depressive symptoms. However, with the application of Deep TMS treatment notable improvements were observed in both depression (p < .001. d = 2.15) and PIL (p < .001, d = 1.59) levels. The treatment also successfully regulated resting-state QEEG (delta/beta) and ERP characteristics (P200 latency), bringing them closer to healthy levels.

CONCLUSIONS

This attenuation of brain activity patterns relating to depression is encouraging as it suggests that effects were robust and are more likely to be sustained over time. This study represents the first exploration of the effects of Deep TMS on PIL and relevant QEEG and ERP biomarkers. The initial evidence suggests that Deep TMS holds promise in enhancing both PIL and neurophysiological health. Future investigations should continue exploring the utility of Deep TMS in targeting a wide range of neuropsychological and physical health conditions, leveraging objective biomarkers such as QEEG and ERP.

Differentiating melancholic and non-melancholic depression via biological markers: A review

OBJECTIVES

Melancholia is a severe form of depression that is typified by greater genetic and biological influence, distinct symptomatology, and preferential response to physical treatment. This paper sought to broadly overview potential biomarkers of melancholia to benefit differential diagnosis, clinical responses and treatment outcomes. Given nuances in distinguishing melancholia as its own condition from other depressive disorder, we emphasised studies directly comparing melancholic to non-melancholic depression.

METHODS

A comprehensive literature search was conducted. Key studies were identified and summarised qualitatively.

RESULTS

105 studies in total were identified. These studies covered a wide variety of biomarkers, and largely fell into three domains: endocrinological (especially cortisol levels, particularly in response to the dexamethasone suppression test), neurological, and immunological (particularly inflammatory markers). Less extensive evidence also exists for metabolic, genetic, and cardiovascular markers.

CONCLUSIONS

Definitive conclusions were predominantly limited due to substantial heterogeneity in how included studies defined melancholia. Furthermore, this heterogeneity could be responsible for the between- and within-group variability observed in the candidate biomarkers that were examined. Therefore, clarifying these definitional parameters may help identify underlying patterns in biomarker expression to improve diagnostic and therapeutic precision for the depressive disorders.

Electrophysiological biomarkers and age characterize phenotypic heterogeneity among individuals with major depressive disorder

Introduction: Despite the high need for effective treatments for major depressive disorder (MDD), the development of novel medicines is hampered by clinical, genetic and biological heterogeneity, unclear links between symptoms and neural dysfunction, and tenuous biomarkers for clinical trial contexts of use. Methods: In this study, we examined the International Study to Predict Optimized Treatment in Depression (iSPOT-D) clinical trial database for new relationships between auditory event-related potential (ERP) responses, demographic features, and clinical symptoms and behavior, to inform strategies for biomarker-driven patient stratification that could be used to optimize future clinical trial design and drug development strategy in MDD. Results: We replicate findings from previous analyses of the classic auditory oddball task in the iSPOT-D sample showing smaller than typical N1 and P300 response amplitudes and longer P300 latencies for target and standard stimuli in patients with MDD, suggesting altered bottom-up sensory and top-down attentional processes. We further demonstrate that age is an important contributor to clinical group differences, affecting both topographic distribution of the clinically informative ERP responses and the types of the stimuli sensitive to group differences. In addition, the observed brain-behavior associations indicate that levels of anxiety and stress are major contributing factors to atypical sensory and attentional processing among patients with MDD, particularly in the older subgroups. Discussion: Our novel findings support the possibility of accelerated cognitive aging in patients with MDD and identify the frontal P300 latency as an additional candidate biomarker of MDD. These results from a large, well-phenotyped sample support the view that heterogeneity of the clinical population with MDD can be systematically characterized based on age and neural biomarkers of sensory and attentional processing, informing patient stratification strategies in the design of clinical trials.

The influence of pride emotion on executive function: Evidence from ERP

BACKGROUND

The current study examined the influence of positive "basic" emotions on executive function; there is limited evidence about the influence of positive "self-conscious"emotions, such as pride, on executive functions processes.

METHODS

Pride is a status-related self-conscious emotion and the present research explored the influence of pride on the subcomponents of executive function, using three experiments that adopted the digit size-parity switching, N-back, and dual choice oddball paradigms.

RESULTS

The behavioral results suggested that cognitive load and behavior inhibition effects in the pride emotion were significantly higher than the neutral emotion. The ERP results showed that the pride emotion elicited smaller P3 difference wave for the switching task and dual choice oddball task. In the N-back task, the pride emotion elicited larger N1 amplitude and smaller P2 difference wave compared to the neutral emotion. A comparison among results from the three experiments indicated that pride emotion restrains all subcomponents of executive function, though with different manifestations of the impact.

CONCLUSION

Experiencing positive emotions is typically viewed as desirable and adaptive in educational settings; however, pride as a unique positive emotion may damage people's cognitive performance, indicating that we need to be cautious when performing cognitive operations in a pride mood.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): III. Emotional dysfunction superspectrum

The Hierarchical Taxonomy of Psychopathology (HiTOP) is a quantitative nosological system that addresses shortcomings of traditional mental disorder diagnoses, including arbitrary boundaries between psychopathology and normality, frequent disorder co-occurrence, substantial heterogeneity within disorders, and diagnostic unreliability over time and across clinicians. This paper reviews evidence on the validity and utility of the internalizing and somatoform spectra of HiTOP, which together provide support for an emotional dysfunction superspectrum. These spectra are composed of homogeneous symptom and maladaptive trait dimensions currently subsumed within multiple diagnostic classes, including depressive, anxiety, trauma-related, eating, bipolar, and somatic symptom disorders, as well as sexual dysfunction and aspects of personality disorders. Dimensions falling within the emotional dysfunction superspectrum are broadly linked to individual differences in negative affect/neuroticism. Extensive evidence establishes that dimensions falling within the superspectrum share genetic diatheses, environmental risk factors, cognitive and affective difficulties, neural substrates and biomarkers, childhood temperamental antecedents, and treatment response. The structure of these validators mirrors the quantitative structure of the superspectrum, with some correlates more specific to internalizing or somatoform conditions, and others common to both, thereby underlining the hierarchical structure of the domain. Compared to traditional diagnoses, the internalizing and somatoform spectra demonstrated substantially improved utility: greater reliability, larger explanatory and predictive power, and greater clinical applicability. Validated measures are currently available to implement the HiTOP system in practice, which can make diagnostic classification more useful, both in research and in the clinic.

Spontaneous eye blinking as a diagnostic marker in prolonged disorders of consciousness

Clinical diagnosis of patients with prolonged disorders of consciousness is very challenging. As spontaneous eye blink rate (EBR) is reliably correlated with cognitive activity in healthy individuals, we investigated whether EBR could serve as a marker of patients' level of consciousness. We assessed ten patients in prolonged Vegetative State/Unresponsive Wakefulness Syndrome (VS/UWS; three females; mean age = 50.3 ± 17.8 years) and fourteen patients in Minimally Conscious State (MCS; three females; mean age = 52.9 ± 17.5 years) at their admission to a rehabilitation unit after the acute phase. During two separate 3-min rest conditions, we recorded patients' EBR by integrating on-line visual and off-line electro-oculographic count. We also assessed EBR during two auditory oddball tasks, i.e. passive listening and active counting of target tones in a sub-group of patients. EBR was significantly higher in MCS than in VS/UWS; moreover, EBR positively correlated with a validated index of responsiveness derived from the Coma Recovery Scale-Revised. Patients' mean EBR showed no significant differences within sessions and across experimental conditions of the oddball task, in both VS/UWS and MCS. Our findings suggest that, at least in the post-acute phase, observing patients' EBR for 3 min at rest could help to discriminate between VS/UWS and MCS, improving accuracy of clinical diagnosis.

Moving beyond belief: A narrative review of potential biomarkers for transcutaneous vagus nerve stimulation

Transcutaneous vagus nerve stimulation (tVNS) is a non-invasive neurostimulation technique that is currently being tested as a potential treatment for a myriad of neurological and psychiatric disorders. However, the working mechanisms underlying tVNS are poorly understood and it remains unclear whether stimulation activates the vagus nerve for every participant. Finding a biological marker of tVNS is imperative, as it can help guide research on clinical applications and can inform researchers on optimal stimulation sites and parameters to further optimize treatment efficacy. In this narrative review, we discuss five potential biomarkers for tVNS and review currently available evidence for these markers for both invasive and tVNS. While some of these biomarkers hold promise from a theoretical perspective, none of the potential biomarkers provide clear and definitive indications that tVNS increases the vagal activity or augments activity in the locus coeruleus-noradrenaline network. We conclude the review by providing several recommendations for how to tackle the challenges and opportunities when researching potential biomarkers for the effects of tVNS.

The P300 in alcohol use disorder: A meta-analysis and meta-regression

OBJECTIVE

The P300 ERP component is a marker of reduced capacity in alcohol use disorder (AUD) to engage attentional mechanisms and update memory representations. No meta-analysis to date has been completed comparing effect size estimates of auditory vs. visual stimuli in AUD. In addition, there is a lack of consensus on whether the P3b in women is reduced, or whether the P3a - an earlier, more frontally distributed component - is reduced in AUD.

METHODS

Strict inclusion criteria and data-analysis plans were implemented. Eligible studies needed to diagnose AUD using DSM or ICD-10 and exclude patients with any psychiatric co-morbidities. Data analysis was completed using a refined variance estimator of the random effects model.

RESULTS

Effect size estimates were large for both auditory (Hedges' g = 1.01, p = .056) and visual (Hedges' g = 0.77, p = .040) P300 amplitudes, but only marginally significant for the auditory modality. Auditory P300 latency was significantly increased in AUD patients (Hedges' g = 0.73, p = .027). The moderator analysis did not show significant sex differences for either auditory (p = .97) or visual (p = .45) P3b. Finally, the P3a was not reduced in patients with AUD (Hedges' g = 1.01; p = .59).

CONCLUSION

This meta-analysis clarifies important questions related to P300 in AUD. By resolving inconsistencies, it is hoped that this information will facilitate the design of futurestudies.

Neuropsychiatric Disorders as Erratic Attention Regulation - Lessons from Electrophysiology

Attention related electrophysiological waves, such as P300, often deviate from norm in various populations of neuropsychiatric patients. For example, the amplitude is often smaller and the latency is often longer in major depressive disorder, in bipolar disorder and in schizophrenia. On the other hand, in other neuropsychiatric populations, it is often possible to note the opposite phenomena of larger P300 amplitude and shorter latency in comparison with norm, but only for a specific subset of stimuli. This is often reported in various anxiety disorders, substance abuse and various chronic pain syndromes. These findings in the various clinical populations, on their commonalities and differences, are presented in this work. The prevalence of these two types of deviations in the electrophysiological markers of attention, shared by multiple neuropsychiatric populations, raise interesting questions regarding the role of attention deviation and regulation in neuropsychiatry. We present these questions and outline a possible hypothesis in this regard. Furthermore, such potential sensitivity of the attention-related markers to clinical dynamics suggests they could be candidates for monitoring and, potentially, early-sensing of clinical dynamics. Therefore, we discuss the potential usability of such markers.

Staging model in psychiatry: Review of the evolution of electroencephalography abnormalities in major psychiatric disorders

AIM

Clinical staging in psychiatry aims to classify patients according to the severity of their symptoms, from stage 0 (increased risk, asymptomatic) to stage 4 (severe illness), enabling adapted treatment at each stage of the illness. The staging model would gain specificity if one or more quantifiable biological markers could be identified. Several biomarkers reflecting possible causal mechanisms and/or consequences of the pathophysiology are candidates for integration into the clinical staging model of psychiatric illnesses.

METHODS

This review covers the evolution (from stage 0 to stage 4) of the most important brain functioning impairments as measured with electroencephalography (EEG), in psychosis spectrum and in severe mood disorders.

RESULTS

The present review of the literature demonstrates that it is currently not possible to draw any conclusion with regard to the state or trait character of any of the EEG impairments in both major depressive disorder and bipolar disorder. As for schizophrenia, the most promising markers of the stage of the illness are the pitch mismatch negativity as well as the p300 event-related potentials, as these components seem to deteriorate with increasing severity of the illness.

CONCLUSIONS

Given the complexity of major psychiatric disorders, and that not a single impairment can be observed in all patients, future research should most likely consider combinations of markers in the quest for a better identification of the stages of the psychiatric illnesses.

Abnormalities in P300 components in depression: an ERP-sLORETA study

BACKGROUND

Alterations in P300 components occur in depressed patients, but the brain regions contributing to these changes remain unclear.

AIMS

Thus, the aim of the present study was to examine the underlying neural activation of P300 components in patients with depression to explore brain regions related to depression.

METHODS

P300 components were evoked by an oddball auditory paradigm and recorded from 30 patients with current depression, as well as 30 age-, gender-, and education level-matched healthy controls. The standardized Low-Resolution Brain Electromagnetic Tomography (sLORETA) method was used to explore the source activation of P300 components.

RESULTS

Compared with healthy controls, depressed patients tended to exhibit lower P200 and P300 amplitudes and prolonged P300 latency. In depressed patients, P200 source activations were reduced in the right insula, right precentral gyrus, left anterior cingulate, medial frontal gyrus, superior frontal gyrus, and middle frontal gyrus. Decreased source activations of P300 were identified in the right insula, postcentral gyrus, superior temporal gyrus, inferior parietal lobule, transverse temporal gyrus, cingulate gyrus, precentral gyrus, middle frontal gyrus, superior frontal gyrus, medial frontal gyrus, and paracentral gyrus.

CONCLUSIONS

Extensive dysfunction over the right hemisphere and bilateral prefrontal dysfunction may be involved in the pathophysiology of depression.

Simple Electroencephalographic Treatment-Emergent Marker Can Predict Repetitive Transcranial Magnetic Stimulation Antidepressant Response-A Feasibility Study

OBJECTIVES

Prefrontal repetitive transcranial magnetic stimulation (rTMS) repeated daily for 4 to 6 weeks is used to treat major depressive disorder, but more than 50% of patients do not achieve significant response. Here we test the validity of a simple electroencephalographic (EEG) marker that predicts nonresponse to rTMS. Such a marker could potentially increase rTMS effectiveness by directing nonresponders to alternative treatments or by guiding early modification of stimulation parameters.

METHODS

We retrospectively analyzed 2-channel EEG data captured in the OPT-TMS National Institute of Mental Health-sponsored, multicenter study. Cumulative Brain Engagement Index (cBEI), a measure derived from template matching that allows scoring EEG dynamics along treatment, was computed.

RESULTS

Six hundred sixty-five EEG recordings were analyzed. In the rTMS group, the median cBEI was found to increase in the responder group but remained unchanged in the nonresponder group. The difference between the cBEI of the groups became statistically significant by the third valid EEG sample. Within 5 samples, 91% of the responders presented with a cBEI above a preset threshold. Within 9 samples, 17% of the nonresponders had a cBEI above the threshold.

CONCLUSIONS

This study demonstrates the feasibility of a simple-to-capture EEG marker as a treatment-emergent marker of response to rTMS treatment of depression. In the OPT-TMS study, discontinuing treatment when the cBEI dropped below the threshold between the fifth to ninth treatment potentially could have avoided administration of 485 (63%) of 765 treatments. Because the marker can be generated online, it would be of interest to evaluate, in future studies, whether it could be used to tune treatment parameters and improve remission rates.

Concomitant Transcranial Direct Current Stimulation With Ultrabrief Electroconvulsive Therapy: A 2-Week Double-Blind Randomized Sham-Controlled Trial

OBJECTIVE

The feasibility and effectiveness of concomitant use of transcranial direct current stimulation (tDCS) with electroconvulsive therapy (ECT) has not been investigated. The study principally aimed at determining whether tDCS when combined with ECT improved the speed of antidepressant response. Secondarily, the ease of generation of seizures during electroconvulsive therapy and cognitive outcomes were investigated.

METHODS

Consecutive patients referred for ECT to treat major depression were randomized to tDCS with dorsolateral prefrontal electrode placements (n = 8) or sham (n = 8) used daily and just before thrice weekly, 6 times threshold, right unilateral ultrabrief (0.3 ms) pulse width ECT. Change of depression severity was determined using the Montgomery Asberg Depression Rating Scale along with cognitive assessments using Montreal Cognitive Assessment and visual memory testing at weeks 1 and 2, which were compared with baseline.

RESULTS

Change of depression severity from baseline was similar in tDCS and ECT compared with sham tDCS and ECT at week1 (mean [standard deviation {SD}] = 16.00 [6.78]; 13.75 [7.83]; P = 0.89) and at week 2 (mean [SD] = 23.00 [4.96]; 19.75 [9.85], P = 0.08). No between-group differences were obtained in the cognitive tests at weeks 1 and 2. Combining tDCS with ECT resulted in higher restimulation: 62.5% requiring 3 stimulations to achieve threshold in contrast to 12.5% with sham tDCS and ECT (P = 0.04). The mean suprathreshold dose was higher in the tDCS and ECT group compared with sham tDCS and ECT: mean [SD] = 144.0 [43.54] and mean [SD] = 122.4 [20.36], P = 0.04, respectively.

CONCLUSIONS

Concomitant use of tDCS with ultrabrief right unilateral ECT is feasible and safe albeit with higher rates of restimulation when tDCS was combined with ECT. However, there were no statistically significant differences in the speed of antidepressant response or cognitive outcomes at weeks 1 and 2 after the commencement of treatments.

Do Event-Related Evoked Potentials Reflect Apathy Tendency and Motivation?

Apathy is a mental state of diminished motivation. Although the reward system as the foundation of the motivation in the human brain has been studied extensively with neuroimaging techniques, the electrophysiological correlates of motivation and apathy have not been fully explored. Thus, in 14 healthy volunteers, we examined whether event-related evoked potentials (ERP) obtained during a simple number discrimination task with/without rewards reflected apathy tendency and a reward-dependent tendency, which were assessed separately using the apathy scale and the temperament and character inventory (TCI). Participants were asked to judge the size of a number, and received feedback based on their performance in each trial. The P3 amplitudes related to the feedback stimuli increased only in the reward condition. Furthermore, the P2 amplitudes related to the negative feedback stimuli in the reward condition had a positive correlation with the reward-dependent tendency in TCI, whereas the P3 amplitudes related to the positive feedback stimuli had a negative correlation with the apathy score. Our result suggests that the P2 and P3 ERPs to reward-related feedback stimuli are modulated in a distinctive manner by the motivational reward dependence and apathy tendency, and thus the current paradigm may be useful for investigating the brain activity associated with motivation.

Emotion Regulating Attentional Control Abnormalities In Major Depressive Disorder: An Event-Related Potential Study

Major depressive disorders (MDD) exhibit cognitive dysfunction with respect to attention. The deficiencies in cognitive control of emotional information are associated with MDD as compared to healthy controls (HC). However, the brain mechanism underlying emotion that influences the attentional control in MDD necessitates further research. The present study explores the emotion-regulated cognitive competence in MDD at a dynamic attentional stage. Event-Related Potentials (ERPs) were recorded from 35 clinical MDD outpatients and matched HCs by applying a modified affective priming dot-probe paradigm, which consisted of various emotional facial expression pairs. From a dynamic perspective, ERPs combined with sLORETA results showed significant differences among the groups. In compared to HC, 100 ms MDD group exhibited a greater interior-prefrontal N100, sensitive to negative-neutral faces. 200 ms MDD showed an activated parietal-occipital P200 linked to sad face, suggesting that the attentional control ability concentrated on sad mood-congruent cognition. 300 ms, a distinct P300 was observed at dorsolateral parietal cortex, representing a sustained attentional control. Our findings suggested that a negatively sad emotion influenced cognitive attentional control in MDD in the early and late attentional stages of cognition. P200 and P300 might be predictors of potential neurocognitive mechanism underlying the dysregulated attentional control of MDD.

A Pilot Study of Possible Easy-to-Use Electrophysiological Index for Early Detection of Antidepressive Treatment Non-Response

INTRODUCTION

The evaluation of response to pharmacological treatment in MDD requires 4-8 weeks. Therefore, the ability to predict response, and especially lack of response to treatment, as early as possible after treatment onset or change, is of prime significance. Many studies have demonstrated significant results regarding the ability to use EEG and ERP markers, including attention-associated markers such as P300, for early prediction of response to treatment. But these markers are derived from long EEG/ERP samples, often from multiple channels, which render them impractical for frequent sampling.

METHODS AND RESULTS

We developed a new electrophysiological attention-associated marker from a single channel (two electrodes), using 1-min samples with auditory oddball stimuli. This work presents an initial evaluation of the ability to use this marker's dynamics between repetitive measures for early (<2 weeks) differentiation between responders and non-responders to antidepressive treatment, in 26 patients with various levels of depression and heterogeneous treatment interventions. The slope of change in the marker between early consecutive samples was negative in the non-responders, but not in the responders. This differentiation was stronger for patients suffering from severe depression (p < 0.001).

CONCLUSION

This pilot study supports the feasibility of the EEG marker for early recognition of treatment-resistant depression. If verified in large-scale prospective studies, it can contribute to research and clinical work.

Depression-Related Brain Connectivity Analyzed by EEG Event-Related Phase Synchrony Measure

This study is to examine changes of functional connectivity in patients with depressive disorder using synchronous brain activity. Event-related potentials (ERPs) were acquired during a visual oddball task in 14 patients with depressive disorder and 19 healthy controls. Electroencephalogram (EEG) recordings were analyzed using event-related phase coherence (ERPCOH) to obtain the functional network. Alteration of the phase synchronization index (PSI) of the functional network was investigated. Patients with depression showed a decreased number of significant electrode pairs in delta phase synchronization, and an increased number of significant electrode pairs in theta, alpha and beta phase synchronization, compared with controls. Patients with depression showed lower target-dependent PSI increment in the frontal-parietal/temporal/occipital electrode pairs in delta-phase synchronization than healthy participants. However, patients with depression showed higher target-dependent PSI increments in theta band in the prefrontal/frontal and frontal-temporal electrode pairs, higher PSI increments in alpha band in the prefrontal pairs and higher increments of beta PSI in the central and right frontal-parietal pairs than controls. It implied that the decrease in delta PSI activity in major depression may indicate impairment of the connection between the frontal and parietal/temporal/occipital regions. The increase in theta, alpha and beta PSI in the frontal/prefrontal sites might reflect the compensatory mechanism to maintain normal cognitive performance. These findings may provide a foundation for a new approach to evaluate the effectiveness of therapeutic strategies for depression.

Just Swap Out of Negative Vibes? Rumination and Inhibition Deficits in Major Depressive Disorder: Data from Event-Related Potentials Studies

Major depression is a serious disorder of impaired emotion regulation. Emotion hyperactivity leads to excessive negative ruminations that daily hijack the patient’s mental life, impacting their mood. Evidence from past researches suggest that depressive patients present several cognitive impairments in attention and working memory, leading to a more acute selective attention for negative stimuli and a greater accessibility of negative memories. Recently, is has been proposed that impaired inhibitory functioning with regard to emotional information processing might be one of the mechanisms of ruminations linking memory, attention and depression. It seems that inhibition deficit is present at both the input level (i.e., the ability to reduce the interference from emotional distracters) and the higher level (i.e., the ability to direct the attention away from emotional material that has already been processed) of emotional information processing. Event-related potentials (ERP) have widely been used to study inhibition in adults suffering from various psychopathological states. In particular, depressive disorder has been linked to ERPs modulations, at early as well as at latter stages of the information-processing stream, when processing affective material. For instance, deficits in inhibiting negative information have been indexed by changes in the parameters (amplitudes and latencies) of early P2, P1 and N1 components while other ERP studies have shown an ability to differentiate depressed patients from normal controls based upon response inhibition difficulties in go-nogo tasks, indexed by later NoGo P3 differences. In this review, we will focus on results of ERP studies investigating inhibition and its interaction with emotional related cue processing in depressive populations. Implications for future research and theoretical perspectives will be discussed within the framework of current models of depressive disorder, based upon the hypothesis that negative ruminations are at the center of depression processes.

Neurophysiological Mechanisms of Auditory Information Processing in Adolescence: A Study on Sex Differences

To date, little is known about sex differences in the neurophysiological correlates underlying auditory information processing. In the present study, auditory evoked potentials were evoked in typically developing male (n = 15) and female (n = 14) adolescents (13-18 years) during an auditory oddball task. Girls compared to boys displayed lower N100 and P300 amplitudes to targets. Larger N100 amplitudes in adolescent boys might indicate higher neural sensitivity to changes of incoming auditory information. The P300 findings point toward sex differences in auditory working memory and might suggest that adolescent boys might allocate more attentional resources when processing relevant auditory stimuli than adolescent girls.

A Possible Common Neurophysiologic Basis for MDD, Bipolar Disorder, and Schizophrenia: Lessons from Electrophysiology

There is ample electrophysiological evidence of attention dysfunction in the EEG/ERP signal of major depressive disorder (MDD), bipolar disorder, and schizophrenia. The reduced attention-related ERP waves show much similarity between MDD, bipolar disorder, and schizophrenia, raising the question whether there are similarities in the neurophysiologic process that underlies attention dysfunction in these pathologies. The present work suggests that there is such a unified underlying neurophysiologic process, which results in reduced attention in the three pathologies. Naturally, as these pathologies involve different clinical manifestations, we expect differences in their underlying neurophysiology. These differences and their subtle manifestation in the ERP marker for attention are also discussed. MDD, bipolar disorder, and schizophrenia are just three of multiple neuropsychiatric disorders, which involve changes in the EEG/ERP manifestations of attention. Further work should expand the basic model presented here to offer comprehensive modeling of these multiple disorders and to emphasize similarities and dissimilarities of the underlying neurophysiologic processes.

Investigating attentional processes in depressive-like domestic horses (Equus caballus)

Some captive/domestic animals respond to confinement by becoming inactive and unresponsive to external stimuli. Human inactivity is one of the behavioural markers of clinical depression, a mental disorder diagnosed by the co-occurrence of symptoms including deficit in selective attention. Some riding horses display 'withdrawn' states of inactivity and low responsiveness to stimuli that resemble the reduced engagement with their environment of some depressed patients. We hypothesized that 'withdrawn' horses experience a depressive-like state and evaluated their level of attention by confronting them with auditory stimuli. Five novel auditory stimuli were broadcasted to 27 horses, including 12 'withdrawn' horses, for 5 days. The horses' reactions and durations of attention were recorded. Non-withdrawn horses reacted more and their attention lasted longer than that of withdrawn horses on the first day, but their durations of attention decreased over days, but those of withdrawn horses remained stable. These results suggest that the withdrawn horses' selective attention is altered, adding to already evidenced common features between this horses' state and human depression.

Auditory selective attention in adolescents with major depression: An event-related potential study

BACKGROUND

Major depression (MD) is associated with deficits in selective attention. Previous studies in adults with MD using event-related potentials (ERPs) reported abnormalities in the neurophysiological correlates of auditory selective attention. However, it is yet unclear whether these findings can be generalized to MD in adolescence. Thus, the aim of the present ERP study was to explore the neural mechanisms of auditory selective attention in adolescents with MD.

METHODS

24 male and female unmedicated adolescents with MD and 21 control subjects were included in the study. ERPs were collected during an auditory oddball paradigm.

RESULTS

Depressive adolescents tended to show a longer N100 latency to target and non-target tones. Moreover, MD subjects showed a prolonged latency of the P200 component to targets. Across groups, longer P200 latency was associated with a decreased tendency of disinhibited behavior as assessed by a behavioral questionnaire.

LIMITATIONS

To be able to draw more precise conclusions about differences between the neural bases of selective attention in adolescents vs. adults with MD, future studies should include both age groups and apply the same experimental setting across all subjects.

CONCLUSIONS

The study provides strong support for abnormalities in the neurophysiolgical bases of selective attention in adolecents with MD at early stages of auditory information processing. Absent group differences in later ERP components reflecting voluntary attentional processes stand in contrast to results reported in adults with MD and may suggest that adolescents with MD possess mechanisms to compensate for abnormalities in the early stages of selective attention.

Overnight changes in waking auditory evoked potential amplitude reflect altered sleep homeostasis in major depression

OBJECTIVE

Sleep homeostasis is altered in major depressive disorder (MDD). Pre- to postsleep decline in waking auditory evoked potential (AEP) amplitude has been correlated with sleep slow wave activity (SWA), suggesting that overnight changes in waking AEP amplitude are homeostatically regulated in healthy individuals. This study investigated whether the overnight change in waking AEP amplitude and its relation to SWA is altered in MDD.

METHOD

Using 256-channel high-density electroencephalography, all-night sleep polysomnography and single-tone waking AEPs pre- and postsleep were collected in 15 healthy controls (HC) and 15 non-medicated individuals with MDD.

RESULTS

N1 and P2 amplitudes of the waking AEP declined after sleep in the HC group, but not in MDD. The reduction in N1 amplitude also correlated with fronto-central SWA in the HC group, but a comparable relationship was not found in MDD, despite equivalent SWA between groups. No pre- to postsleep differences were found for N1 or P2 latencies in either group. These findings were not confounded by varying levels of alertness or differences in sleep variables between groups.

CONCLUSION

MDD involves altered sleep homeostasis as measured by the overnight change in waking AEP amplitude. Future research is required to determine the clinical implications of these findings.

The impact of depression heterogeneity on inhibitory control

OBJECTIVE

Major depressive disorder (MDD) is associated with deficits in executive cognitive function, including inhibitory control. However, inconsistencies have been found across studies. Depression is a heterogeneous disorder and these inconsistencies may therefore relate to heterogeneity in relatively small samples.

METHOD

Here we sought to examine event-related potentials (ERPs) during a cognitive Go/No-Go task in melancholic (n = 60) and non-melancholic depressed patients (n = 54) relative to controls (n = 114).

RESULTS

Behavioural responses indicate that inhibitory control processes are differentially affected by subtypes of depression such that melancholic patients exhibit a greater number of commission errors and more variable response rates in comparison to non-melancholic patients and controls respectively. However, ERPs do not differ during a cognitive Go/No-Go task when ERPs associated with correct responses are examined.

CONCLUSIONS

These findings indicate that while patients with melancholia differ from patients without melancholia and controls, no neurophysiological differences are observed when controlling for observable behavioural impairment.

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.

Thalamocortical changes in major depression probed by deconvolution and physiology-based modeling

Auditory event-related potentials (ERPs) have been extensively studied in patients with depression, but most studies have focused on purely phenomenological analysis methods, such as component scoring. In contrast, this study applies two recently developed physiology-based methods-fitting using a thalamocortical model of neuronal activity and waveform deconvolution - to data from a selective-attention task in four subject groups (49 patients with melancholic depression, 34 patients with non-melancholic depression, 111 participants with subclinical depressed mood, and 98 healthy controls), to yield insight into physiological differences in attentional processing between participants with major depression and controls. This approach found evidence that: participants with depressed mood, regardless of clinical status, shift from excitation in the thalamocortical system towards inhibition; that clinically depressed participants have decreased relative response amplitude between target and standard waveforms; and that patients with melancholic depression also have increased thalamocortical delays. These findings suggest possible physiological mechanisms underlying different depression subtypes, and may eventually prove useful in motivating new physiology-based diagnostic methods.

Mismatch negativity in treatment-resistant depression and borderline personality disorder

OBJECTIVE

Cognitive dysfunctions, such as attentional impairment, are central features of both treatment-resistant depression (TRD) and borderline personality disorder (BPD). The treatment failure of TRD due to its comorbidity with BPD is debated in the literature. The mismatch negativity (MMN) of the event-related potentials provides an objective marker of involuntary stimulus selective processing, which might help shed light on this issue and provide an avenue for investigating a possible endophenotypic marker for TRD.

METHOD

We investigated MMN in 22 patients with TRD, 19 with BPD, and 22 with TRD cormorbid with BPD (TRD+BPD), as well as in 32 healthy volunteers, by employing an acoustic frequency deviance paradigm. In addition, we measured the depressive mood using the Plutchik-van Praag (PVP) depression inventory.

RESULTS

There was no significant between-group difference for the N1 latencies/amplitudes, both to the standard and deviant stimuli, and no significant between-group difference for MMN latencies. However, MMN amplitudes were higher in the TRD group than those in the other three groups. PVP scores were highest in TRD+BPD, then TRD, BPD patients, and lowest in healthy subjects. The higher MMN was not correlated with PVP score, nor with the duration of life-long depression, which can be considered as a neurophysiological marker for TRD.

CONCLUSION

An atypical lack of inhibition on the irrelevant stimuli or increased cortical neuronal activity, especially frontal area, or both, might be responsible for the finding.