Event-related potential measures of attention in moderately depressed subjects

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.

Endogenous evoked potentials assessment in depression: a review

Over the past 15 years, researchers have shown an increasing interest in using event-related potentials (ERPs) to study depression. These studies generally fall into four classes: 1), ERPs as a means of detecting depression; 2), ERPs as a tool for distinguishing subtypes of depression; 3), ERPs as a measure of pharmacological effectiveness; 4), ERPs as indicators of defective cognitive operations in depressed subjects. Results from these heterogeneous approaches are often inconsistent and disappointing. Although some ERP components often show increased latencies and diminished amplitudes, these changes seem to reflect principally a variety of non-specific disorders affecting a wide range of cognitive functions rather than a precise and consistent deficit of a particular function. These disappointing results seem to be attributable to methodological problems (heterogeneous patient populations, disproportionate use of the odd-ball paradigm), and do not necessarily call into question the value of studying the ERPs. Furthermore, recent advances in ERP methodology have opened up new perspectives for ERP use in psychopathology.

Effects of Repeated Concussions and Sex on Early Processing of Emotional Facial Expressions as Revealed by Electrophysiology

OBJECTIVES

Concussions affect the processing of emotional stimuli. This study aimed to investigate how sex interacts with concussion effects on early event-related brain potentials (ERP) measures (P1, N1) of emotional facial expressions (EFE) processing in asymptomatic, multi-concussion athletes during an EFE identification task.

METHODS

Forty control athletes (20 females and 20 males) and 43 multi-concussed athletes (22 females and 21 males), recruited more than 3 months after their last concussion, were tested. Participants completed the Beck Depression Inventory II, the Beck Anxiety Inventory, the Post-Concussion Symptom Scale, and an Emotional Facial Expression Identification Task. Pictures of male and female faces expressing neutral, angry, and happy emotions were randomly presented and the emotion depicted had to be identified as fast as possible during EEG acquisition.

RESULTS

Relative to controls, concussed athletes of both sex exhibited a significant suppression of P1 amplitude recorded from the dominant right hemisphere while performing the emotional face expression identification task. The present study also highlighted a sex-specific suppression of the N1 component amplitude after concussion which affected male athletes.

CONCLUSIONS

These findings suggest that repeated concussions alter the typical pattern of right-hemisphere response dominance to EFE in early stages of EFE processing and that the neurophysiological mechanisms underlying the processing of emotional stimuli are distinctively affected across sex. (JINS, 2018, 24, 673-683).

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 review of electroencephalographic changes in diabetes mellitus in relation to major depressive disorder

A bidirectional relationship exists between diabetes mellitus (DM) and major depressive disorder (MDD), with depression commonly reported in both type 1 DM (T1DM) and type 2 DM (T2DM), and depressive symptoms associated with a higher incidence of diabetes. However, how the two conditions are pathologically connected is not completely understood. Similar neurophysiological abnormalities have been reported in both DM and MDD, including elevated electroencephalographic (EEG) activity in low-frequency slow waves and increased latency and/or reduced amplitude of event-related potentials. It is possible that this association reflects some common underlying pathology, and it has been proposed that diabetes may place patients at risk for depression through a biological mechanism linking the metabolic changes of DM to changes in the central nervous system. In this review we will discuss EEG abnormalities in DM, as well as the biological mechanisms underlying various EEG parameters, in order to evaluate whether or not a common EEG biosignature exists between DM and MDD. Identifying such commonalities could significantly inform the current understanding of the mechanisms that subserve the development of the two conditions. Moreover, this new insight may provide the basis for informing new drug discovery capable of mitigating and possibly even preventing both conditions.

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.

Event-related potential based evidence of cognitive dysfunction in patients during the first episode of depression using a novelty oddball task

Studies using event-related potentials (ERP) to investigate cognitive dysfunction associated with depression have generated variable findings. The differences among reported results are typically attributed to the disparity of the samples. To eliminate the effects of factors such as medication and comorbidity with other psychiatric disorders, first-episode unmedicated patients suffering from depression were recruited in this study. Both depressed patients and matched controls performed an auditory novelty oddball task and ERPs were recorded. The depression group exhibited an increased P2 to standard tones. For the target tones, depressed subjects showed reduced N2 at anterior regions and reduced target P3 in the right hemisphere. In response to novel stimuli, there was a reduced amplitude of the novelty P3 component at the fronto-central region in depressed patients. Our findings suggest that patients with depression in the initial stages show an impaired ability in voluntary and involuntary attention and exhibit frontal lobe and right-hemisphere dysfunctions.

Fronto-temporal alterations within the first 200 ms during an attentional task distinguish major depression, non-clinical participants with depressed mood and healthy controls: a potential biomarker?

Attentional impairment in depression is a cardinal feature of depression and has been proposed as a candidate endophenotype for major depressive disorder. Event-related potentials (ERPs) elicited by oddball signal detection tasks provide objective markers of selective stimulus processing, and are pertinent endophenotypic markers for depression. While previous studies have sought to determine objective markers for attentional impairment in depression, evidence is inconsistent and may involve heterogeneity in relatively small samples. Here, we brought together oddball ERP recording with source localization of neural correlates of selective attention in outpatients with major depressive disorder (MDD; n = 78) and participants with depressed mood (PDM; n = 127) relative to healthy controls (CTL; n = 116). The key finding was a dimensional exaggeration of the P200 (140-270 ms) to both target (signal) and non-target (noise) stimuli, most pronounced in MDD, followed by PDM, relative to CTL. This exaggeration was coupled with slower and more variable response times, suggesting that neural systems are attempting to compensate for a difficulty in discriminating signal from noise. P200 alterations were localised to limbic (hippocampal), temporal and ventral prefrontal regions, key components of the signal detection network. A subsequent reduction and delay in the P300 was also revealed for MDD indicating that the pronounced lack of discrimination in clinical depression may also lead to impaired stimulus evaluation. This P200 increase in depression could provide a potential mechanism for the attentional impairment frequently observed in depression and consequent alterations in the P300 may differentiate clinically significant depression.

Familial risk for depression and p3b component as a possible neurocognitive vulnerability marker

OBJECTIVE

Complex genetic mechanisms are involved in the vulnerability to depressive disorders and cognitive dysfunctions found in depression. This study was performed to explore the effect of the familial risk for depression on electrophysiological correlates of attentional functions as demonstrated by an event-related potential (ERP) go/no-go experiment.

METHODS

The component P3b as an indicator of target detection processing was investigated in two groups of healthy subjects with or without a family history of depression (n = 14 each). An electrophysiological source localization method (LORETA) was employed to allow a neuro-anatomical interpretation for the ERP data.

RESULTS

The group with a familial risk for depression showed a reduced P3b amplitude over left temporal areas in contrast to the control group. This two-dimensional effect was associated with a significantly reduced activation of the left middle temporal gyrus.

CONCLUSIONS

The P3b amplitude decrement might represent a neurocognitive vulnerability marker for the development of depression.

Antiepileptic Drugs and the Significance of Event-Related Potentials

The authors compared cognitive changes in epilepsy patients with or without antiepileptic drugs using event-related potential (ERP) N270 and P300. The patients were divided into three groups according to treatment type: carbamazepine, valproate acid (VPA), or no treatment. One control group composed of healthy subjects was included. The Mini-Mental State Examination detected no clinical dementia in all subjects. A modified Sternberg paradigm was used as a task when an ERP was recorded. When a stimulus was different from the memorized item (conflict condition), N270 was elicited in both controls and patients. All the three patient groups showed a delayed and smaller N270 than the control group. P300 was elicited when a stimulus was the same one as the memorized item (match condition), and its amplitude decreased in the VPA group. P300 latency did not differ among the four groups. ERP (N270 and P300) was abnormal in patients with epilepsy. These results indicate that antiepileptic drugs, especially VPA, might enhance the impairment of cognitive processing. N270 is more sensitive than P300 in the early detection of minor cognitive impairment in epileptics.

PREDICTING SEVERITY OF NON-CLINICAL DEPRESSION: PRELIMINARY FINDINGS USING AN INTEGRATED APPROACH

INTRODUCTION

Depression is characterized by disturbances in affect, cognition, brain and body function, yet studies have tended to focus on single domains of dysfunction. An integrated approach may provide a more complete profile of the range of deficits characterized by depressed individuals, but it is unclear whether this approach is able to predict depression severity over and above that predicted by single tasks or domains of function. In this study, we examined the value of combining multiple domains of function in predicting depression severity.

METHODS

Participants contained in the International Brain Database, (http://www.brainresource.com) had completed three testing components including a web-based questionnaire of Personal History, the Brain Resource Cognition battery of Neuropsychological tests, Personality assessment and Psychophysiological testing. Two hundred and sixty six of these participants were able to be classified as either non-depressed, mild-moderately or severely (non-clinically) depressed, based on a depression screening questionnaire. Analysis of variance identified variables on which the categorized participants differed. Significant variables were then entered into a series of stepwise regressions to examine their ability to predict depression scores.

RESULTS

An integrated model including measures of affect (increased Neuroticism; decreased Emotional Intelligence), cognition (increased variability of reaction time during a working memory task; decreased "name the word component score" in the verbal interference task), brain (decreased left-lateralized P150 ERP component during a working memory task) and body function (increased negative skin conductance level gradient) were found to predict more of the variation in depression severity than any single domain of function.

DISCUSSION

On the basis of behavioral as well as Psychophysiological findings reported in this study, it was suggested that deficits in subclinically depressed individuals are more pronounced during automatic stages of stimulus processing, and that performance in these individuals may improve (to the level displayed by controls) when task demands are increased. Findings also suggest that it is important to consider disturbances across different domains of function in order to elucidate depression severity. Each domain may contribute unique explanatory information consistent with an integrative model of depression, taking into account the role of both behavior and underlying neural changes.

Abnormalities of P300 cortical current density in unmedicated depressed patients revealed by LORETA analysis of event-related potentials

The purpose of the present study was to investigate the neural substrates underlying event-related potential (ERP) abnormalities, with respect to the generators of the ERP components in depressed patients. Using an oddball paradigm, ERP from auditory stimuli were recorded from 22 unmedicated patients with current depressive episodes and compared with those from 22 age- and gender-matched normal controls. Cortical current densities of the N100 and P300 components were analyzed using low-resolution electromagnetic tomography (LORETA). Group differences in cortical current density were mapped on a 3-D cortex model. The results revealed that N100 cortical current densities did not differ between the two groups, while P300 cortical current densities were significantly lower in depressed patients over the bilateral temporal lobes, the left frontal region, and the right temporal-parietal area. Furthermore, the cortical area in which the group difference in P300 current density had been identified was remarkably larger over the right than the left hemisphere, thus supporting the hypothesis of right hemisphere dysfunction in depression.

Habituation deficit in auditory event-related potentials in tinnitus complainers

According to Hallam's habituation theory of tinnitus, most of the suffering caused by tinnitus is due to difficulties in habituation to the perceived tinnitus sound. Thus tinnitus complainers are assumed to display a less pronounced habituation as compared to tinnitus non-complainers. In the present study, an experimental test of this theory was undertaken using event-related potentials (ERPs) as indicators of habituation to exogenously administered tone pips. In 22 patients (10 tinnitus complainers and 12 tinnitus non-complainers) and 10 healthy controls, the habituation of ERPs to series of auditory stimuli across four consecutive trials was studied. Diminuition of the N(1) and P(2) amplitudes of the ERPs was taken to measure the habituation process across the trials. Tinnitus complainers showed a less distinct habituation of the N(1)-P(2) amplitude difference (vertex potential) compared to tinnitus non-complainers. The results are in accordance with Hallam's theory and support the notion that patients with a severe tinnitus fail to properly habituate to auditory stimuli.

Reduced attention in mice overproducing corticotropin-releasing hormone

Data from several studies suggest that unrestrained secretion of corticotropin-releasing hormone in the CNS produces several signs and symptoms of depression. Recent evidence indicates that blockade of the CRH receptor 1 reduced depression scores in depressed patients. One of the symptoms that occur is depression is impairment in attentional processes. Whether these impairments are due to alterations in the CRH system are so far unknown. In order to investigate whether overproduction of CRH alters attentional process, transgenic mice overproducing CRH were tested on an operant five choice serial reaction time task, a task which taxes sustained and divided attention. Mutants showed impaired autoshaping. During initial discrimination learning, transgenics performed below wildtype level, but with extended training with long stimulus durations, transgenic animals reached similar accuracy levels as wildtype mice. When animals were tested at shortest stimulus duration (0.5s), a mild but significant impairment in accurate responding emerged in transgenics. This was accompanied by longer correct response latencies, while incorrect latencies did not differ between groups, suggesting attentional impairment in CRH transgenics. Because these animals have been reported to also show increased anxiety-related behaviour, animals were treated with the anxiolytic benzodiazepine diazepam. Diazepam failed to affect accuracy, but transgenic mice showed a stronger behavioural disinhibition. This suggests that the attentional impairment seen in CRH overexpressors is independent of alterations in anxiety-like behaviour. These findings may have implications for understanding the pathophysiology of psychiatric disorders such as depression, where it has been suggested that an overactivity of the CRH system accounts for a variety of symptoms, including hyper-arousal and attentional impairment.

Effects of transient, mild mood states on semantic memory organization and use: an event-related potential investigation in humans

The effects of transient mood states on semantic memory organization and use were investigated using event-related potentials. Participants read sentence pairs ending with (1) the most expected word, (2) an unexpected word from the expected semantic category, or (3) an unexpected word from a different (related) category; half the pairs were read under neutral mood and half under positive mood. Under neutral mood, N400 amplitudes were smallest for expected items and smaller for unexpected items when these came from the expected category. In contrast, under positive mood, N400 amplitudes to the two types of unexpected items did not differ. Positive mood seemed to specifically facilitate the processing of distantly-related, unexpected items. The results suggest that transient mood states are associated with dynamic changes in how semantic memory is used on-line.

Event-related potential indices of auditory selective attention in dependent amphetamine users

BACKGROUND

The aim of the present study was to further investigate a previously reported attention-related impairment in dependent amphetamine users using event-related potential (ERP) indices of selective attention.

METHODS

ERPs were recorded during an auditory selective attention task (SAT) that involved detecting infrequent long-duration target tones presented among short-duration tones that varied in location (left vs. right ear) and pitch (low vs. high). Amphetamine users (n = 19) were divided into two groups, high dependence (n = 10) and low dependence (n = 10), based on amphetamine Severity of Dependence Scale scores, and compared to an age-matched control group (n = 9).

RESULTS

The high-dependence group showed slowed reaction time and reduced early processing negativity and peak N1 amplitude to location-relevant nontarget stimuli. Poor performance on the SAT was highly correlated with deficits in early processing, which were also related to poor performance on the Wechsler Memory Scale Attention/Concentration index.

CONCLUSIONS

It is suggested that severely dependent users suffer an inability to selectively enhance the sensory processing of relevant auditory information. This may produce poor automatic preferential processing of relevant information and increase load on limited attentional resources.

Selective attention is impaired in amyotrophic lateral sclerosis--a study of event-related EEG potentials

In humans, selective attention is assumed to be under control of the frontal lobe. A significant proportion of patients with amyotrophic lateral sclerosis (ALS) shows impairments in various tasks touching frontal lobe function. We, therefore, undertook a study of event-related EEG potentials (ERPs) in eight non-demented ALS patients in order to investigate a possible deficit of auditory selective attention: tones were presented in random sequence to the left or right ear, one of which was to be attended. The negative shift of the ERPs evoked by attended tones in relation to unattended tones ('processing negativity': PN) was smaller in ALS patients than in age-matched healthy control persons. This was true for Fz and Cz and for both a slow and a fast presentation rate of the tones. In the patients, reduced PN amplitude correlated with functional motor impairment. The utility of ERP testing to assess impaired frontal lobe function is shown for the first time in ALS patients. The results of our study fit to recent positron emission tomography (PET) and fMRI data.

The effect of aging on spectral parameters of event-related potentials

Forty-two healthy subjects ranging in age from 20 to 73 were divided into three groups according to age; a young group (20-33 years), a middle-aged group (34-49 years) and older group (50-73 years). Event-related potentials (ERPs) of three groups were recorded in two different experimental conditions that the infrequent stimulus was counted (Test 1) or uncounted (Test 2). ERPs were elicited using infrequent and frequent stimuli as red and green lights respectively. Spectral analysis of ERPs showed that decibel (dB) values of 1-2 and 3-4 Hz in young and middle-aged groups while dB value of 1-2 Hz in older group were significantly decreased in Test 2 compared with Test 1. When the number of subjects displaying amplitude maximum in each frequency band was considered, significant differences were found in 1-2 and 5-7 Hz frequency bands of young and middle-aged groups, but no significant differences were found for older group.

[Electrophysiologic tests and benzodiazepine hypnosis]

The effects of a pure benzodiazepine antagonist (Flumazenil) on the responses R1 and R2 of the blink reflex, psychomotor tests, and Event Related Potentials (ERP), in six healthy volunteers sedated with Midazolam have been compared. Measurements were made during each of four successive phases. Phase 0 corresponded to control recordings. Midazolam was administered rapidly during phase 1 and slowly during phase 2. Phase 3 corresponded to spontaneous waking once the administration of Midazolam had been stopped. Flumazenil was administered during phase 2. As the subjects fell asleep, R1 and R2 were the last parameters to disappear. Under the influence of Flumazenil, R1 was the first to reappear, while R2 did not recur until complete waking, and the other tests were unpracticable. During phase 3, R1 reappeared before R2 once more, the psychomotor test responses and ERP returning only later. The modifications of both R1 and R2 of the blink reflex are a good criterion of the presence of BZD in a toxic coma and a good test to indicate the depth of a coma or a sedation with BZD, whilst ERP, since they require the cooperation of the patient, are a test of vigilance and not of awakening.

Auditory selective attention is impaired in Parkinson's disease--event-related evidence from EEG potentials

Selective attention refers to the ability to focus on one channel of information in the presence of distracting other channels. For the visual modality, results on impairments of selective attention have been conflicting in patients with idiopathic Parkinson's disease (PD). Independent of possible interferences from visual or movement disturbances selective attention can be measured as the so-called 'processing negativity' (PN) using auditory evoked potentials. Therefore, auditory selective attention with the PN was measured in 14 patients with PD and 16 control subjects. Subjects had to attend to tones presented to one ear (i.e. to press a button to occasionally presented longer tones) and ignore tones presented to the other ear. Tones were presented at a rate of 1/s ('slow') or 2/s ('fast'). PN was measured as the difference of the potentials evoked by attended minus ignored standard tones. PN was significantly smaller in the PD patients than in the controls with slow presentation. There was no difference between both groups with fast presentation. PN remained unchanged when patients had a 12-h withdrawal of their usual anti-Parkinsonian drug therapy. PD patients and controls did not differ in their P3 component evoked in the usual 'oddball' task nor in the mismatch negativity evoked by the occasionally longer tones in the PN task. The results provide evidence for an impairment of auditory selective attention that is specific for patients with PD (i.e. independent of the P3 component).