The utility of P300 as a schizophrenia endophenotype and predictive biomarker: clinical and socio-demographic modulators in COGS-2

Duration of untreated psychosis and cognitive function in first-episode antipsychotic-naïve schizophrenia: Evidence from auditory P300

OBJECTIVE

The relationship between the duration of untreated psychosis (DUP) and cognitive function in schizophrenia (SZ) patients remains debated, with no empirical evidence from event-related potential (ERP) studies supporting their association. This study aims to investigate the relationship between DUP and cognitive functions, as well as psychiatric symptoms, in first-episode antipsychotic-naïve SZ (FEAN-SZ) patients using ERP.

METHODS

The study included 321 Chinese FEAN-SZ patients and 146 healthy controls. The DUP and sociodemographic characteristics of all participants were collected, and psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale. The P300 (P3) components, including P3a, P3b and N100, were recorded from all participants using auditory oddball paradigm.

RESULTS

25.5 % of patients did not receive timely treatment for over four years, and those with lower educational levels or more severe negative symptoms had longer DUP (p = 0.027, p = 0.020). Compared to healthy controls, FEAN-SZ patients exhibited longer latencies and lower amplitudes in the P3 components (all ps < 0.001). Significant differences in the P3 components were observed among three groups of DUP (< 8 months, 8 to 48 months, and ≥ 48 months) (all ps < 0.001). In the 8 ≤ DUP < 48 months group, the N1 amplitude and P3a latency predicted positive symptom scores and general psychopathology scores, respectively (β = -0.165, p = 0.037; β = 0.541, p < 0.001); P3b latency predicted negative symptom scores in the DUP < 8 months group (β = 0.391, p < 0.001). N1 amplitude predicted general psychopathology scores only in the DUP > 48 months group (β = -0.228, p = 0.040). Multiple linear regression analysis indicated that the latency and amplitude of P3a were independently associated with DUP (B = 0.124, p < 0.001; B = -1.161, p = 0.012).

CONCLUSIONS

SZ patients who have a longer DUP exhibit more severe P3 deficits, and the P3 components may be indicative of different psychiatric symptom severity in DUPs of different lengths, as well as the P3a component may serve as an electrophysiologic marker to assess the length of DUP.

Association between auditory P300 event-related potential and suicidal thoughts and behaviors in first-episode antipsychotic-naïve patients with schizophrenia

OBJECTIVE

Suicidal thoughts and behaviors (STBs) are critical concern in schizophrenia (SZ). Concurrent changes in event-related potential (ERP), particularly the P300 (P3) components, have been observed in SZ patients, but the association between these changes and STBs remains unclear. This study aims to explore the relationships between P3 components and STBs in first-episode antipsychotic-naïve SZ (FEAN-SZ) patients.

METHODS

The study included 321 FEAN-SZ patients and 146 healthy controls (HC). Sociodemographic data, clinical assessments, and ERP P3 components (N1, P3a, and P3b) were collected. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), while depressive symptoms were evaluated with the Hamilton Depression Scale (HAMD).

RESULTS

Compared to HC, FEAN-SZ patients exhibited lower N1 and P3 amplitudes and longer latencies (all ps < 0.001). Patients with STBs exhibited higher scores on negative, general psychopathology, PANSS total and HAMD, decreased N1 and P3a amplitudes, as well as prolonged P3a and P3b latencies compared to those without STBs (all ps < 0.001). The P3a latency predicted the general psychopathology scores (β = 0.103, p < 0.001), and the N1 amplitude predicted the HAMD scores (β = -1.057, p = 0.001), both exclusively within the STBs group. Logistic regression analysis identified that N1 amplitude (Beta = -0.132, p = 0.018, OR = 1.02, 95%CI = 1.01-1.04) and HAMD scores (Beta = 0.068, p = 0.001, OR = 1.07, 95%CI = 1.03-1.11) as independent predictors of STBs in FEAN-SZ patients. Combining these variables yielded an area under the receiver operating characteristic (AUCROC) curve of 0.840 for distinguishing between patients with and without STBs.

CONCLUSIONS

FEAN-SZ patients with STBs have lower P3 amplitude and longer latency. The N1 amplitude and depressive levels are associated with STBs in FEAN-SZ patients. The N1 amplitude may serve as an early biological marker for STBs in SZ patients.

Do smaller P300 amplitudes in schizophrenia result from larger variability in temporal processing?

The P3b is a prominent event-related potential (ERP) with maximal amplitude between 250 ms and 500 ms after the onset of a rare target stimulus within a sequence of standard non-target stimuli (oddball paradigm). Several studies found reduced P3b amplitudes in patients with schizophrenia compared to neurotypicals. Our work and the literature suggest that temporal imprecision may play a large pathophysiological role in schizophrenia. Here, we investigated whether reduced P3b amplitudes result from reduced neural activity (power) or temporal imprecision (inter-trial phase coherence; ITC) in delta and theta bands, using two EEG datasets from different studies with different oddball paradigms (Study 1: 19 patients with schizophrenia and 17 matched controls, Study 2: 26 patients and 26 controls). Both studies revealed typical P3b ERP components with smaller amplitudes in patients. Reduced ITC in patients was found in the delta band, which correlated with P3b peak amplitudes for all participant groups (ρ = 0.58-0.89). In Study 1, we also found significant differences between patients and controls in ITC in the theta band, which also correlated with P3b peak amplitudes (patients' ρ = 0.64, controls' ρ = 0.54). This was not found in Study 2. The results indicate that P3b amplitude reduction in patients with schizophrenia is linked to a reduction in temporal precision of neural activity. These results expand the notion of imprecision in temporal processing at phenomenological, psychological, and neurological levels that have been related to disturbances of the sense of self. They confirm that temporal imprecision may be more important than the reduction of neural activity itself.

Association of GAD1 gene polymorphism rs3749034 with the information processing and cognitive event-related potentials in schizophrenia patients and healthy subjects

OBJECTIVE

Glutamic acid decarboxylase, an enzyme in GABA biosynthesis, is encoded by the GAD1 gene, the transcriptional activity of which is affected by the rs3749034 polymorphism. The aim was to investigate the effects of rs3749034 on cognitive event-related potentials (P300) in healthy subjects and schizophrenic patients.

METHODS

Determination of rs3749034 polymorphism was performed in 89 healthy volunteers and 109 schizophrenic patients (males). Two-stimulus oddball task performance and P300 auditory evoked potentials were analyzed and patient symptomatology was assessed using the Positive and Negative Syndrome Scale (PANSS).

RESULTS

An increased frequency of C allele carriers was disclosed in patients. In controls, superior task performance was observed in cytosine-thymine carriers, while a greater P300 amplitude and shorter latency were found in C/C carriers. Analogous effects were found in patients with a disease onset before 25 years of age. Higher N5 and lower P3 and G5 PANSS scales were revealed in C/C homozygotes.

CONCLUSIONS

The findings substantiate an involvement of GABA-ergic mechanisms in maintaining an optimal excitatory-inhibitory balance and an association of rs3749034 with early-onset disorder and negative symptoms of schizophrenia.

SIGNIFICANCE

These results are important for understanding underlying mechanisms and the development of evidence-based methods for assessing the risk of schizophrenia.

P300 in schizophrenia: Then and now

The 1965 discovery of the P300 component of the electroencephalography (EEG)-based event-related potential (ERP), along with the subsequent identification of its alteration in people with schizophrenia, initiated over 50 years of P300 research in schizophrenia. Here, we review what we now know about P300 in schizophrenia after nearly six decades of research. We describe recent efforts to expand our understanding of P300 beyond its sensitivity to schizophrenia itself to its potential role as a biomarker of risk for psychosis or a heritable endophenotype that bridges genetic risk and psychosis phenomenology. We also highlight efforts to move beyond a syndrome-based approach to understand P300 within the context of the clinical, cognitive, and presumed pathophysiological heterogeneity among people diagnosed with schizophrenia. Finally, we describe several recent approaches that extend beyond measuring the traditional P300 ERP component in people with schizophrenia, including time-frequency analyses and pharmacological challenge studies, that may help to clarify specific cognitive mechanisms that are disrupted in schizophrenia. Moreover, we discuss several promising areas for future research, including studies of animal models that can be used for treatment development.

Temporal imprecision of phase coherence in schizophrenia and psychosis-dynamic mechanisms and diagnostic marker

Schizophrenia (SCZ) is a complex disorder in which various pathophysiological models have been postulated. Brain imaging studies using EEG/MEG and fMRI show altered amplitude and, more recently, decrease in phase coherence in response to external stimuli. What are the dynamic mechanisms of such phase incoherence, and can it serve as a differential-diagnostic marker? Addressing this gap in our knowledge, we uniquely combine a review of previous findings, novel empirical data, and computational-dynamic simulation. The main findings are: (i) the review shows decreased phase coherence in SCZ across a variety of different tasks and frequencies, e.g., task- and frequency-unspecific, which is further supported by our own novel data; (ii) our own data demonstrate diagnostic specificity of decreased phase coherence for SCZ as distinguished from major depressive disorder; (iii) simulation data exhibit increased phase offset in SCZ leading to a precision index, in the millisecond range, of the phase coherence relative to the timing of the external stimulus. Together, we demonstrate the key role of temporal imprecision in phase coherence of SCZ, including its mechanisms (phase offsets, precision index) on the basis of which we propose a phase-based temporal imprecision model of psychosis (PTP). The PTP targets a deeper dynamic layer of a basic disturbance. This converges well with other models of psychosis like the basic self-disturbance and time-space experience changes, as discussed in phenomenological and spatiotemporal psychopathology, as well as with the models of aberrant predictive coding and disconnection as in computational psychiatry. Finally, our results show that temporal imprecision as manifest in decreased phase coherence is a promising candidate biomarker for clinical differential diagnosis of SCZ, and more broadly, psychosis.

Neurophysiological Models in Individuals at Clinical High Risk for Psychosis: Using Translational EEG Paradigms to Forecast Psychosis Risk and Resilience

Over the last several decades, there have been major research efforts to improve the identification of youth and young adults at clinical high-risk for psychosis (CHR-P). Among individuals identified as CHR-P based on clinical criteria, approximately 20% progress to full-blown psychosis over 2-3 years and 30% achieve remission. In more recent years, neurophysiological measures with established sensitivity to schizophrenia have gained traction in the study of CHR-P and its range of clinical outcomes, with the goal of identifying specific biomarkers that precede psychosis onset that 7 chapter, we review studies examining several translational electroencephalography (EEG) and event-related potential (ERP) measures, which have known sensitivity to schizophrenia and reflect abnormal sensory, perceptual, and cognitive processing of task stimuli, as predictors of future clinical outcomes in CHR-P individuals. We discuss the promise of these EEG/ERP biomarkers of psychosis risk, including their potential to provide (a) translational bridges between human studies and animal models focused on drug development for early psychosis, (b) target engagement measures for clinical trials, and (c) prognostic indicators that could enhance personalized treatment planning.

The Use of Event-Related Potentials in the Study of Schizophrenia: An Overview

Event-related potentials (ERPs) are small voltage changes in the brain that reliably occur in response to auditory or visual stimuli. ERPs have been extensively studied in both humans and animals to identify biomarkers, test pharmacological agents, and generate testable hypotheses about the physiological and genetic basis of schizophrenia. In this chapter, we discuss how ERPs are generated and recorded as well as review canonical ERP components in the context of schizophrenia research in humans. We then discuss what is known about rodent homologs of these components and how they are altered in common pharmacologic and genetic manipulations used in preclinical schizophrenia research. This chapter will also explore the relationship of ERPs to leading hypotheses about the pathophysiology of schizophrenia. We conclude with an evaluation of both the utility and limitations of ERPs in schizophrenia research and offer recommendations of future directions that may be beneficial to the field.

Psychosis Endophenotypes: A Gene-Set-Specific Polygenic Risk Score Analysis

BACKGROUND AND HYPOTHESIS

Endophenotypes can help to bridge the gap between psychosis and its genetic predispositions, but their underlying mechanisms remain largely unknown. This study aims to identify biological mechanisms that are relevant to the endophenotypes for psychosis, by partitioning polygenic risk scores into specific gene sets and testing their associations with endophenotypes.

STUDY DESIGN

We computed polygenic risk scores for schizophrenia and bipolar disorder restricted to brain-related gene sets retrieved from public databases and previous publications. Three hundred and seventy-eight gene-set-specific polygenic risk scores were generated for 4506 participants. Seven endophenotypes were also measured in the sample. Linear mixed-effects models were fitted to test associations between each endophenotype and each gene-set-specific polygenic risk score.

STUDY RESULTS

After correction for multiple testing, we found that a reduced P300 amplitude was associated with a higher schizophrenia polygenic risk score of the forebrain regionalization gene set (mean difference per SD increase in the polygenic risk score: -1.15 µV; 95% CI: -1.70 to -0.59 µV; P = 6 × 10-5). The schizophrenia polygenic risk score of forebrain regionalization also explained more variance of the P300 amplitude (R2 = 0.032) than other polygenic risk scores, including the genome-wide polygenic risk scores.

CONCLUSIONS

Our finding on reduced P300 amplitudes suggests that certain genetic variants alter early brain development thereby increasing schizophrenia risk years later. Gene-set-specific polygenic risk scores are a useful tool to elucidate biological mechanisms of psychosis and endophenotypes, offering leads for experimental validation in cellular and animal models.

Value of P300 amplitude in the diagnosis of untreated first-episode schizophrenia and psychosis risk syndrome in children and adolescents

BACKGROUND

Identifying the characteristic neurobiological changes of early psychosis is helpful for early clinical diagnosis. However, previous studies on the brain electrophysiology of children and adolescents with psychosis are rare.

METHODS

This study compared P300 amplitude at multiple electrodes between children and adolescents with first-episode schizophrenia (FES, n = 48), children and adolescents with psychosis risk syndrome (PRS, n = 24), and healthy controls (HC, n = 30). Receiver operating characteristic (ROC) analysis was used to test the ability of P300 amplitude to distinguish FES, PRS and HC individuals.

RESULTS

The P300 amplitude in the FES group were significantly lower than those in the HC at the Cz, Pz, and Oz electrodes. The P300 amplitude was also significantly lower in the prodromal group than in the HC at the Pz and Oz electrodes. ROC curve analysis showed that at the Pz electrode, the P300 amplitude evoked by the target and standard stimulus showed high sensitivity, specificity, accuracy, and area under the curve value for distinguishing FES from HC individuals.

CONCLUSIONS

This study found early visual P300 deficits in children and adolescents with FES and PRS, with the exclusion of possible influence of medication and chronic medical conditions, suggesting the value of P300 amplitude for the identification of early psychosis.

Disease-specific resting-state EEG network variations in schizophrenia revealed by the contrastive machine learning

Given a multitude of genetic and environmental factors, when investigating the variability in schizophrenia (SCZ) and the first-degree relatives (R-SCZ), latent disease-specific variation is usually hidden. To reliably investigate the mechanism underlying the brain deficits from the aspect of functional networks, we newly iterated a framework of contrastive variational autoencoders (cVAEs) applied in the contrasts among three groups, to disentangle the latent resting-state network patterns specified for the SCZ and R-SCZ. We demonstrated that the comparison in reconstructed resting-state networks among SCZ, R-SCZ, and healthy controls (HC) revealed network distortions of the inner-frontal hypoconnectivity and frontal-occipital hyperconnectivity, while the original ones illustrated no differences. And only the classification by adopting the reconstructed network metrics achieved satisfying performances, as the highest accuracy of 96.80% ± 2.87%, along with the precision of 95.05% ± 4.28%, recall of 98.18% ± 3.83%, and F1-score of 96.51% ± 2.83%, was obtained. These findings consistently verified the validity of the newly proposed framework for the contrasts among the three groups and provided related resting-state network evidence for illustrating the pathological mechanism underlying the brain deficits in SCZ, as well as facilitating the diagnosis of SCZ.

Discrimination of auditory verbal hallucination in schizophrenia based on EEG brain networks

Auditory verbal hallucinations (AVH) are a core positive symptom of schizophrenia and are regarded as a consequence of the functional breakdown in the related sensory process. Yet, the potential mechanism of AVH is still lacking. In the present study, we explored the difference between AVHs (n = 23) and non-AVHs (n = 19) in schizophrenia and healthy controls (n = 29) by using multidimensional electroencephalograms data during an auditory oddball task. Compared to healthy controls, both AVH and non-AVH groups showed reduced P300 amplitudes. Additionally, the results from brain networks analysis revealed that AVH patients showed reduced left frontal to posterior parietal/temporal connectivity compared to non-AVH patients. Moreover, using the fused network properties of both delta and theta bands as features for in-depth learning made it possible to identify the AVH from non-AVH patients at an accuracy of 80.95%. The left frontal-parietal/temporal networks seen in the auditory oddball paradigm might be underlying biomarkers of AVH in schizophrenia. This study demonstrated for the first time the functional breakdown of the auditory processing pathway in the AVH patients, leading to a better understanding of the atypical brain network of the AVH patients.

Auditory P300 in individuals with high schizotypy: associations of schizotypal traits with amplitude and latency under different oddball conditions

Background

The aim of this study was to compare the characteristics of auditory P300 between non-clinical individuals with high and low schizotypal traits, and investigate the relationship between schizotypy and P300 under various oddball conditions.

Methods

An extreme-group design was adopted. After screening 1,519 young adults using the Schizotypal Personality Questionnaire (SPQ), sixty-three participants were chosen and divided into two groups (schizotypy group: 31 participants; control group: 32 participants). Basic demographic information was assessed and matched between groups. Depression and anxiety indexes were evaluated and controlled. The P300 component was evoked by an auditory oddball paradigm with different frequencies and durations.

Results

(1) The duration P300 amplitude at PZ site was significantly weaker in the schizotypy group than in the control group [F(1,54) = 7.455, p = 0.009, η_p² = 0.121]. (2) In the schizotypy group, the latency of frequency P300 at PZ site under large-variant oddball condition was significantly correlated with total SPQ scores (r_p = 0.451, p = 0.018) and disorganized dimension scores (r_p = 0.381, p = 0.050). (3) In the control group, significantly negative correlations was found between the negative dimension score of SPQ and the frequency P300 amplitudes under small variant condition (PZ: r_p = -0.393, p = 0.043; CPZ: r_p = -0.406, p = 0.035). In addition, a significant negative relationship was found between disorganized dimension scores and the duration P300 latency at CPZ site under large-variant oddball condition (r_p = -0.518, p = 0.006). Moreover, a significant negative association was found between the duration P300 amplitude at CPZ site under small-variant oddball condition and negative factor scores (r_p = -0.410, p = 0.034).

Conclusion

Individuals with high schizotypal traits were likely to have deficient attention and hypoactive working memory for processing auditory information, especially the duration of sounds. P300 effects were correlated with negative and disorganized schizotypy, rather than positive schizotypy. There were diverse patterns of relationship between schizotypal traits and P300 under different oddball conditions, suggesting that characteristics and parameters of target stimuli should be considered cautiously when implementing an auditory oddball paradigm for individuals with schizophrenia spectrum.

Neural substrates of cognitive impairment in a NMDAR hypofunction mouse model of schizophrenia and partial rescue by risperidone

N-methyl D-aspartate receptor (NMDAR) hypofunction is a pathophysiological mechanism relevant for schizophrenia. Acute administration of the NMDAR antagonist phencyclidine (PCP) induces psychosis in patients and animals while subchronic PCP (sPCP) produces cognitive dysfunction for weeks. We investigated the neural correlates of memory and auditory impairments in mice treated with sPCP and the rescuing abilities of the atypical antipsychotic drug risperidone administered daily for two weeks. We recorded neural activities in the medial prefrontal cortex (mPFC) and the dorsal hippocampus (dHPC) during memory acquisition, short-term, and long-term memory in the novel object recognition test and during auditory processing and mismatch negativity (MMN) and examined the effects of sPCP and sPCP followed by risperidone. We found that the information about the familiar object and its short-term storage were associated with mPFC→dHPC high gamma connectivity (phase slope index) whereas long-term memory retrieval depended on dHPC→mPFC theta connectivity. sPCP impaired short-term and long-term memories, which were associated with increased theta power in the mPFC, decreased gamma power and theta-gamma coupling in the dHPC, and disrupted mPFC-dHPC connectivity. Risperidone rescued the memory deficits and partly restored hippocampal desynchronization but did not ameliorate mPFC and circuit connectivity alterations. sPCP also impaired auditory processing and its neural correlates (evoked potentials and MMN) in the mPFC, which were also partly rescued by risperidone. Our study suggests that the mPFC and the dHPC disconnect during NMDAR hypofunction, possibly underlying cognitive impairment in schizophrenia, and that risperidone targets this circuit to ameliorate cognitive abilities in patients.

Global Functional Connectivity at Rest Is Associated with Attention: An Arterial Spin Labeling Study

Neural markers of attention, including those frequently linked to the event-related potential P3 (P300) or P3b component, vary widely within and across participants. Understanding the neural mechanisms of attention that contribute to the P3 is crucial for better understanding attention-related brain disorders. All ten participants were scanned twice with a resting-state PCASL perfusion MRI and an ERP with a visual oddball task to measure brain resting-state functional connectivity (rsFC) and P3 parameters (P3 amplitudes and P3 latencies). Global rsFC (average rsFC across the entire brain) was associated with both P3 amplitudes (r = 0.57, p = 0.011) and P3 onset latencies (r = -0.56, p = 0.012). The observed P3 parameters were correlated with predicted P3 amplitude from the global rsFC (amplitude: r = +0.48, p = 0.037; latency: r = +0.40, p = 0.088) but not correlated with the rsFC over the most significant individual edge. P3 onset latency was primarily related to long-range connections between the prefrontal and parietal/limbic regions, while P3 amplitudes were related to connections between prefrontal and parietal/occipital, between sensorimotor and subcortical, and between limbic/subcortical and parietal/occipital regions. These results demonstrated the power of resting-state PCASL and P3 correlation with brain global functional connectivity.

Tensor factorization approach for ERP-based assessment of schizotypy in a novel auditory oddball task on perceived family stress

Objective. Schizotypy, a potential phenotype for schizophrenia, is a personality trait that depicts psychosis-like signs in the normal range of psychosis continuum. Family communication may affect the social functioning of people with schizotypy. Greater family stress, such as irritability, criticism and less praise, is perceived at a higher level of schizotypy. This study aims to determine the differences between people with high and low levels of schizotypy using electroencephalography (EEG) during criticism, praise and neutral comments. EEGs were recorded from 29 participants in the general community who varied from low schizotypy to high schizotypy (HS) during a novel emotional auditory oddball task.Approach. We consider the difference in event-related potential parameters, namely the amplitude and latency of P300 subcomponents (P3a and P3b), between pairs of target words (standard, positive, negative and neutral). A model based on tensor factorization is then proposed to detect these components from the EEG using the CANDECOMP/PARAFAC decomposition technique. Finally, we employ the mutual information estimation method to select influential features for classification.Main results.The highest classification accuracy, sensitivity, and specificity of 93.1%, 94.73%, and 90% are obtained via leave-one-out cross validation.Significance. This is the first attempt to investigate the identification of individuals with psychometrically-defined HS from brain responses that are specifically associated with perceiving family stress and schizotypy. By measuring these brain responses to social stress, we achieve the goal of improving the accuracy in detection of early episodes of psychosis.

Documentation of Peripheral Auditory Function in Studies of the Auditory P300 Response

Abstract. A critical review was conducted to examine whether the peripheral hearing status of participants with neurological and psychological disorders was documented in published clinical studies of the auditory P300 response. Literature searches were conducted with three databases: PubMed, PsycINFO, and Scopus. Studies of participants with seven neurological or psychological disorders were included in the study. Each disorder was coupled with the main search phrase in separate searches on each database. Of the total 102 papers which met the inclusion criteria, the majority (64%) did not describe the peripheral hearing sensitivity of participants. In this review with studies that included participants at risk for hearing impairment, particularly age-related hearing loss, only a single publication adequately described formal hearing evaluation. Peripheral hearing status is rarely defined in studies of the P300 response. The inclusion of participants with a hearing loss likely affects the validity of findings for these studies. We recommend formal hearing assessment prior to inclusion of participants in studies of the auditory P300 response. The findings of this study may increase the awareness among researchers outside the field of audiology of the effects of peripheral hearing loss on the auditory P300.

Event-related potential correlates of affective response inhibition in bipolar I disorder: Comparison with schizophrenia

BACKGROUND

Individuals with bipolar I disorder (BD) have difficulty inhibiting context-inappropriate responses. The neural mechanisms contributing to these difficulties, especially in emotional contexts, are little understood. This study aimed to inform mechanisms of impaired impulsivity control in response to emotion in BD, and whether response inhibition indices are altered to a similar degree in schizophrenia spectrum disorders (SZ). We examined alterations to behavioral performance and event-related potentials (ERPs) during inhibition to affective stimuli in BD, relative to healthy control participants (HC) and SZ.

METHODS

Sixty-six participants with BD, 32 participants with SZ, and 48 HC completed a Go/No-Go task with emotional face stimuli while electroencephalography was recorded. Behavioral signal detection metrics (perceptual sensitivity, response bias) and ERPs (N200, P300) were compared across groups.

RESULTS

Relative to HC, participants with BD showed reduced (1) discrimination of Go vs. No-Go stimuli (i.e., emotional vs. neutral faces), and (2) P300 amplitudes elicited by emotional faces. Results similarly extended to SZ: BD and SZ groups did not differ on behavioral performance nor ERP amplitudes.

LIMITATIONS

Aspects of the Go/No-Go task design may have limited findings, and medication effects on ERP amplitudes in patient samples cannot be fully ruled out.

CONCLUSIONS

Findings suggest the difficulty participants with BD and SZ experienced on the current affective response inhibition task lied largely in discriminating between facial expressions. Difficulties with discriminating emotional from neutral expressions may contribute to difficulties with appropriate behavioral responding in social-affective contexts for individuals with BD and SZ.

Machine Learning Techniques for the Diagnosis of Schizophrenia Based on Event-Related Potentials

Antecedent

The event-related potential (ERP) components P300 and mismatch negativity (MMN) have been linked to cognitive deficits in patients with schizophrenia. The diagnosis of schizophrenia could be improved by applying machine learning procedures to these objective neurophysiological biomarkers. Several studies have attempted to achieve this goal, but no study has examined Multiple Kernel Learning (MKL) classifiers. This algorithm finds optimally a combination of kernel functions, integrating them in a meaningful manner, and thus could improve diagnosis.

Objective

This study aimed to examine the efficacy of the MKL classifier and the Boruta feature selection method for schizophrenia patients (SZ) and healthy controls (HC) single-subject classification.

Methods

A cohort of 54 SZ and 54 HC participants were studied. Three sets of features related to ERP signals were calculated as follows: peak related features, peak to peak related features, and signal related features. The Boruta algorithm was used to evaluate the impact of feature selection on classification performance. An MKL algorithm was applied to address schizophrenia detection.

Results

A classification accuracy of 83% using the whole dataset, and 86% after applying Boruta feature selection was obtained. The variables that contributed most to the classification were mainly related to the latency and amplitude of the auditory P300 paradigm.

Conclusion

This study showed that MKL can be useful in distinguishing between schizophrenic patients and controls when using ERP measures. Moreover, the use of the Boruta algorithm provides an improvement in classification accuracy and computational cost.

Visual P300 as a neurophysiological correlate of symptomatic improvement by a virtual reality-based computer AT system in patients with auditory verbal hallucinations: A Pilot study

Previous comparative trials showed that virtual reality (VR) therapies achieved larger effects than gold-standard cognitive-behavioral therapy (CBT) on overall auditory verbal hallucinations (AVHs). However, no trial has examined the corresponding underlying electrophysiological mechanisms. We performed a pilot randomized comparative trial evaluating the efficacy of a virtual reality-based computer AT system (CATS) over CBT for schizophrenia (SCZ) patients with treatment-resistant AVHs and explored these potential electrophysiological changes via the visual P300 component. Patients (CATS, n = 32; CBT, n = 33) completed the clinical assessments pre- and post-interventions and at 12-week follow-up. The visual P300 were measured before and after both therapies. The analysis of changes in psychiatric symptoms used linear mixed-effects models, and the P300 response in temporal and time-frequency domains was analyzed with repeated-measures analysis of variance. There was no interaction effect between change in clinical symptoms and treatment group. However, several statistically significant within-group improvements were found for CATS and CBT over time. AVH improved significantly after both treatments, as measured with the Psychotic Symptom Rating Scales-Auditory Hallucinations (PSYRATS-AH) sub-scores. Especially for the CATS group, omnipotence beliefs, anxiety symptoms, self-esteem, and quality of life also remained improved at the 12-week follow-up. Moreover, P300 amplitude had a significant interaction effect and correlation with AVH response. Overall, our analysis did not demonstrate general clinical superiority of CATS over CBT, but CATS improved refractory AVH in SCZ patients, likely by increasing P300 amplitude. These findings support the continued development of CATS for persistent AVH and suggest further trials to clarify the neurological effects of CATS.

Temporal and time-frequency features of auditory oddball response in distinct subtypes of patients at clinical high risk for psychosis

Individuals at clinical high risk (CHR) for psychosis exhibit a reduced P300 oddball response, which indicates deficits in attention and working memory processes. Previous studies have mainly researched these responses in the temporal domain; hence, non-phase-locked or induced neural activities may have been ignored. Event-related potential (ERP) and time-frequency (TF) information, combined with clinical and cognitive profiles, may provide an insight into the pathophysiology and psychopathology of the CHR stage. The 104 CHR individuals who completed cognitive assessments and ERP tests were recruited and followed up between 2016 and 2018. Individuals with CHR were classified by three clinical subtypes demonstrated before, specifically 32 from Cluster-1 (characterized by extensive negative symptoms and cognitive deficits, at the highest risk for conversion to psychosis), 34 from Cluster-2 (characterized by thought and behavioral disorganization, with moderate cognitive impairment), and 38 from Cluster-3 (characterized by the mildest symptoms and cognitive deficits). Electroencephalograms were recorded during the auditory oddball paradigm. The P300 ERPs were analyzed in the temporal domain. The event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) were acquired by TF analysis. A reduced P300 response to target tones was noted in Cluster-1 relative to the other two clusters. Moreover, the P300 amplitude of Cluster-1 was associated with speed of processing (SoP) scores. Furthermore, the P300 amplitude of Cluster-3 was significantly correlated with verbal and visual learning scores. In the TF analysis, decreased delta ERSP and ITC were observed in Cluster-1; delta ITC was associated with SoP scores in Cluster-3. The results indicate relatively disrupted oddball responses in a certain CHR subtype and a close affinity between these electrophysiological indexes and attention, working memory, and declarative memory within different CHR clusters. These findings suggest that the auditory oddball response is a potential neurophysiological marker for distinct clinical subtypes of CHR.

Psychosis Biotypes: Replication and Validation from the B-SNIP Consortium

Current clinical phenomenological diagnosis in psychiatry neither captures biologically homologous disease entities nor allows for individualized treatment prescriptions based on neurobiology. In this report, we studied two large samples of cases with schizophrenia, schizoaffective, and bipolar I disorder with psychosis, presentations with clinical features of hallucinations, delusions, thought disorder, affective, or negative symptoms. A biomarker approach to subtyping psychosis cases (called psychosis Biotypes) captured neurobiological homology that was missed by conventional clinical diagnoses. Two samples (called "B-SNIP1" with 711 psychosis and 274 healthy persons, and the "replication sample" with 717 psychosis and 198 healthy persons) showed that 44 individual biomarkers, drawn from general cognition (BACS), motor inhibitory (stop signal), saccadic system (pro- and anti-saccades), and auditory EEG/ERP (paired-stimuli and oddball) tasks of psychosis-relevant brain functions were replicable (r's from .96-.99) and temporally stable (r's from .76-.95). Using numerical taxonomy (k-means clustering) with nine groups of integrated biomarker characteristics (called bio-factors) yielded three Biotypes that were virtually identical between the two samples and showed highly similar case assignments to subgroups based on cross-validations (88.5%-89%). Biotypes-1 and -2 shared poor cognition. Biotype-1 was further characterized by low neural response magnitudes, while Biotype-2 was further characterized by overactive neural responses and poor sensory motor inhibition. Biotype-3 was nearly normal on all bio-factors. Construct validation of Biotype EEG/ERP neurophysiology using measures of intrinsic neural activity and auditory steady state stimulation highlighted the robustness of these outcomes. Psychosis Biotypes may yield meaningful neurobiological targets for treatments and etiological investigations.

Event-related potentials associated to N-back test performance in schizophrenia

Mapping of Event-Related Potentials (ERP) associated with auditory and visual odd-ball paradigms has shown consistent differences between healthy controls and schizophrenia patients. It may be hypothesized that higher task attentional/cognitive demand will result in larger differences in these paradigms, which may help understanding the substrates of cognitive deficits in this syndrome. To this aim, we performed an EEG study comparing the effects of increasing the attentional/cognitive load of an auditory N-back task on the Event-Related Potential in 50 subjects with schizophrenia (11 first episodes) and 35 healthy controls. We considered a post-target window of 1000 ms to explore possible between groups differences in N100, P300, and Late Slow Wave (LSW), and compared these components between 0-back ('lower attentional/cognitive load) and 1-back ('higher attentional/cognitive load') conditions. Our results showed that N100 and LSW amplitude increase from 0- to 1-back condition was significantly larger in healthy controls compared to schizophrenia patients. Furthermore, LSW amplitude difference between 0- and 1-back conditions positively correlated with performance in the behavioral cognitive assessment. Taken together, these results support that higher task attentional/cognitive load (0-back vs. 1-back condition) increase N100 amplitude differences and reveal new findings related to the LSW component in schizophrenia.

A Review on P300 in Obsessive-Compulsive Disorder

Neuropsychological studies indicate the presence of cognitive changes in patients with obsessive-compulsive disorder (OCD). Indeed, OCD may be included among the dysfunctions of the frontal lobes and their connections with the limbic system, associative cortex, and basal ganglia. P300 is a positive component of the human event-related potential (ERP); it is associated with processes of encoding, identification, and categorization constituting, as a whole, the superior cortical function of information processing. Thus, P300 explores several areas that are implicated in OCD pathophysiology. Our aim is to review all relevant studies on the P300 component of the human ERP in order to recognize any significant central nervous system (CNS) correlate of cognitive dysfunction in OCD. A PubMed-based literature search resulted in 35 articles assessing P300 in OCD and reporting neurophysiological correlates of response inhibition, cortical hyperarousal, and over-focused attention. A decreased P300 amplitude was reported in both adult and pediatric patients, with a trend toward normalization after pharmacological treatment. Source localization studies disclosed an association between P300 abnormalities and the functioning of brain regions involved in the pathophysiology of OCD. Moreover, studies converge on the evidence of neurophysiological dysfunction in the frontal areas with impairment of the normal inhibitory processes in OCD. At least some of these electrophysiological correlates might reflect the obsessive thoughts and compulsions that characterize this disorder. These findings may also support cognitive-behavioral therapy (CBT) approaches on over-focused attention and inflexibility of compulsive behaviors, which should be associated to pharmacological treatment in these patients.

N-methyl-d-aspartate receptor antagonism modulates P300 event-related potentials and associated activity in salience and central executive networks

Impairments in auditory information processing in schizophrenia as indexed electrophysiologically by P300 deficits during novelty (P3a) and target (P3b) processing are linked to N -methyl- D -aspartate receptor (NMDAR) dysfunction. This study in 14 healthy volunteers examined the effects of a subanesthetic dose of the NMDAR antagonist ketamine on P300 and their relationship to psychomimetic symptoms and cortical source activity (with eLORETA). Ketamine reduced early (e- P3a) and late (l-P3a) novelty P300 at sensor (scalp)-level and at source-level in the salience network. Increases in dissociation symptoms were negatively correlated with ketamine-induced P3b changes, at sensor-level and source-level, in both salience and central executive networks. These P3a alterations during novelty processing, and the symptom-related P3b changes during target processing support a model of NMDAR hypofunction underlying disrupted auditory attention in schizophrenia.

Auditory Oddball Responses Across the Schizophrenia-Bipolar Spectrum and Their Relationship to Cognitive and Clinical Features

OBJECTIVE

Neural activations during auditory oddball tasks may be endophenotypes for psychosis and bipolar disorder. The authors investigated oddball neural deviations that discriminate multiple diagnostic groups across the schizophrenia-bipolar spectrum (schizophrenia, schizoaffective disorder, psychotic bipolar disorder, and nonpsychotic bipolar disorder) and clarified their relationship to clinical and cognitive features.

METHODS

Auditory oddball responses to standard and target tones from 64 sensor EEG recordings were compared across patients with psychosis (total N=597; schizophrenia, N=225; schizoaffective disorder, N=201; bipolar disorder with psychosis, N=171), patients with bipolar disorder without psychosis (N=66), and healthy comparison subjects (N=415) from the second iteration of the Bipolar-Schizophrenia Network for Intermediate Phenotypes (B-SNIP2) study. EEG activity was analyzed in voltage and in the time-frequency domain (low, beta, and gamma bands). Event-related potentials (ERPs) were compared with those from an independent sample collected during the first iteration of B-SNIP (B-SNIP1; healthy subjects, N=211; psychosis group, N=526) to establish the repeatability of complex oddball ERPs across multiple psychosis syndromes (r values >0.94 between B-SNIP1 and B-SNIP2).

RESULTS

Twenty-six EEG features differentiated the groups; they were used in discriminant and correlational analyses. EEG variables from the N100, P300, and low-frequency ranges separated the groups along a diagnostic continuum from healthy to bipolar disorder with psychosis/bipolar disorder without psychosis to schizoaffective disorder/schizophrenia and were strongly related to general cognitive function (r=0.91). P50 responses to standard trials and early beta/gamma frequency responses separated the bipolar disorder without psychosis group from the bipolar disorder with psychosis group. P200, N200, and late beta/gamma frequency responses separated the two bipolar disorder groups from the other groups.

CONCLUSIONS

Neural deviations during auditory processing are related to psychosis history and bipolar disorder. There is a powerful transdiagnostic relationship between severity of these neural deviations and general cognitive performance. These results have implications for understanding the neurobiology of clinical syndromes across the schizophrenia-bipolar spectrum that may have an impact on future biomarker research.

Characteristic changes in EEG spectral powers of patients with opioid-use disorder as compared with those with methamphetamine- and alcohol-use disorders

Electroencephalography (EEG) likely reflects activity of cortical neurocircuits, making it an insightful estimation for mental health in patients with substance use disorder (SUD). EEG signals are recorded as sinusoidal waves, containing spectral amplitudes across several frequency bands with high spatio-temporal resolution. Prior work on EEG signal analysis has been made mainly at individual electrodes. These signals can be evaluated from advanced aspects, including sub-regional and hemispheric analyses. Due to limitation of computational techniques, few studies in earlier work could conduct data analyses from these aspects. Therefore, EEG in patients with SUD is not fully understood. In the present retrospective study, spectral powers from a data house containing opioid (OUD), methamphetamine/stimulants (MUD), and alcohol use disorder (AUD) were extracted, and then converted into five distinct topographic data (i.e., electrode-based, cortical subregion-based, left-right hemispheric, anterior-posterior based, and total cortex-based analyses). We found that data conversion and reorganization in the topographic way had an impact on EEG spectral powers in patients with OUD significantly different from those with MUD or AUD. Differential changes were observed from multiple perspectives, including individual electrodes, subregions, hemispheres, anterior-posterior cortices, and across the cortex as a whole. Understanding the differential changes in EEG signals may be useful for future work with machine learning and artificial intelligence (AI), not only for diagnostic but also for prognostic purposes in patients with SUD.

Brain variability in dynamic resting-state networks identified by fuzzy entropy: a scalp EEG study

Objective.Exploring the temporal variability in spatial topology during the resting state attracts growing interest and becomes increasingly useful to tackle the cognitive process of brain networks. In particular, the temporal brain dynamics during the resting state may be delineated and quantified aligning with cognitive performance, but few studies investigated the temporal variability in the electroencephalogram (EEG) network as well as its relationship with cognitive performance.Approach.In this study, we proposed an EEG-based protocol to measure the nonlinear complexity of the dynamic resting-state network by applying the fuzzy entropy. To further validate its applicability, the fuzzy entropy was applied into simulated and two independent datasets (i.e. decision-making and P300).Main results.The simulation study first proved that compared to the existing methods, this approach could not only exactly capture the pattern dynamics in time series but also overcame the magnitude effect of time series. Concerning the two EEG datasets, the flexible and robust network architectures of the brain cortex at rest were identified and distributed at the bilateral temporal lobe and frontal/occipital lobe, respectively, whose variability metrics were found to accurately classify different groups. Moreover, the temporal variability of resting-state network property was also either positively or negatively related to individual cognitive performance.Significance.This outcome suggested the potential of fuzzy entropy for evaluating the temporal variability of the dynamic resting-state brain networks, and the fuzzy entropy is also helpful for uncovering the fluctuating network variability that accounts for the individual decision differences.

Critical Dynamics in Spontaneous Resting-State Oscillations Are Associated With the Attention-Related P300 ERP in a Go/Nogo Task

Sustained attention is the ability to continually concentrate on task-relevant information, even in the presence of distraction. Understanding the neural mechanisms underlying this ability is critical for comprehending attentional processes as well as neuropsychiatric disorders characterized by attentional deficits, such as attention deficit hyperactivity disorder (ADHD). In this study, we aimed to investigate how trait-like critical oscillations during rest relate to the P300 evoked potential-a biomarker commonly used to assess attentional deficits. We measured long-range temporal correlations (LRTC) in resting-state EEG oscillations as index for criticality of the signal. In addition, the attentional performance of the subjects was assessed as reaction time variability (RTV) in a continuous performance task following an oddball paradigm. P300 amplitude and latencies were obtained from EEG recordings during this task. We found that, after controlling for individual variability in task performance, LRTC were positively associated with P300 amplitudes but not latencies. In line with previous findings, good performance in the sustained attention task was related to higher P300 amplitudes and earlier peak latencies. Unexpectedly, we observed a positive relationship between LRTC in ongoing oscillations during rest and RTV, indicating that greater criticality in brain oscillations during rest relates to worse task performance. In summary, our results show that resting-state neuronal activity, which operates near a critical state, relates to the generation of higher P300 amplitudes. Brain dynamics close to criticality potentially foster a computationally advantageous state which promotes the ability to generate higher event-related potential (ERP) amplitudes.

Contingent Negative Variation Blunting and Psychomotor Dysfunction in Schizophrenia: A Systematic Review

The contingent negative variation (CNV) is an event-related potential that provides a neural index of psychomotor processes (eg, attention and motor planning) well known to be dysfunctional in schizophrenia. Although evidence suggests that CNV amplitude is blunted in patients with schizophrenia (SZ) compared to healthy controls (HCs), there is currently no meta-analytic evidence for the size of the effect. Further, it is unknown how CNV blunting compares to closely related measures of psychomotor dysfunction, such as reaction time slowing. We used random-effects models to calculate the pooled effect size (ES) across 30 studies investigating CNV amplitude differences between patients and HCs (NSZ = 685, NHC = 714). Effect sizes for reaction time slowing across the studies were also quantified. Potential moderators, including sample characteristics and aspects of the CNV measurement, were examined. There was robust blunting of CNV activity in patients compared to HCs (ES = -0.79). The magnitude of this effect did not differ from reaction time slowing. Notably, CNV blunting in patients was significantly greater at central sites (ES = -0.87) compared to frontal sites (ES = -0.48). No other assessed methodological characteristics significantly moderated the magnitude of CNV differences. There is a large effect for CNV blunting in SZ that appears robust to potential confounds or methodological moderators. In addition, reduced CNV activity was statistically comparable to that of reaction time slowing. Blunting was the largest at central electrodes, which has been implicated in motor preparation. These findings speak to the complexity of psychomotor dysfunction in SZ and suggest significant promise for a biomarker.

Electroencephalography and Event-Related Potential Biomarkers in Individuals at Clinical High Risk for Psychosis

Clinical outcomes vary among youths at clinical high risk for psychosis (CHR-P), with approximately 20% progressing to full-blown psychosis over 2 to 3 years and 30% achieving remission. Recent research efforts have focused on identifying biomarkers that precede psychosis onset and enhance the accuracy of clinical outcome prediction in CHR-P individuals, with the ultimate goal of developing staged treatment approaches based on the individual's level of risk. Identifying such biomarkers may also facilitate progress toward understanding pathogenic mechanisms underlying psychosis onset, which may support the development of mechanistically informed early interventions for psychosis. In recent years, electroencephalography-based event-related potential measures with established sensitivity to schizophrenia have gained traction in the study of CHR-P and its clinical outcomes. In this review, we describe the evidence for event-related potential abnormalities in CHR-P and discuss how they inform our understanding of information processing deficits as vulnerability markers for emerging psychosis and as indicators of future outcomes. Among the measures studied, P300 and mismatch negativity are notable because deficits predict conversion to psychosis and/or CHR-P remission. However, the accuracy with which these and other measures predict outcomes in CHR-P has been obscured in the prior literature by the tendency to only report group-level differences, underscoring the need for inclusion of individual predictive accuracy metrics in future studies. Nevertheless, both P300 and mismatch negativity show promise as electrophysiological markers of risk for psychosis, as target engagement measures for clinical trials, and as potential translational bridges between human studies and animal models focused on novel drug development for early psychosis.

Testing Psychosis Phenotypes From Bipolar-Schizophrenia Network for Intermediate Phenotypes for Clinical Application: Biotype Characteristics and Targets

BACKGROUND

Psychiatry aspires to the molecular understanding of its disorders and, with that knowledge, to precision medicine. Research supporting such goals in the dimension of psychosis has been compromised, in part, by using phenomenology alone to estimate disease entities. To this end, we are proponents of a deep phenotyping approach in psychosis, using computational strategies to discover the most informative phenotypic fingerprint as a promising strategy to uncover mechanisms in psychosis.

METHODS

Doing this, the Bipolar-Schizophrenia Network for Intermediate Phenotypes (B-SNIP) has used biomarkers to identify distinct subtypes of psychosis with replicable biomarker characteristics. While we have presented these entities as relevant, their potential utility in clinical practice has not yet been demonstrated.

RESULTS

Here we carried out an analysis of clinical features that characterize biotypes. We found that biotypes have unique and defining clinical characteristics that could be used as initial screens in the clinical and research settings. Differences in these clinical features appear to be consistent with biotype biomarker profiles, indicating a link between biological features and clinical presentation. Clinical features associated with biotypes differ from those associated with DSM diagnoses, indicating that biotypes and DSM syndromes are not redundant and are likely to yield different treatment predictions. We highlight 3 predictions based on biotype that are derived from individual biomarker features and cannot be obtained from DSM psychosis syndromes.

CONCLUSIONS

In the future, biotypes may prove to be useful for targeting distinct molecular, circuit, cognitive, and psychosocial therapies for improved functional outcomes.

Analysis of KCNH2 and CACNA1C schizophrenia risk genes on EEG functional network modulation during an auditory odd-ball task

A deficit in task-related functional connectivity modulation from electroencephalogram (EEG) has been described in schizophrenia. The use of measures of neuronal connectivity as an intermediate phenotype may allow identifying genetic factors involved in these deficits, and therefore, establishing underlying pathophysiological mechanisms. Genes involved in neuronal excitability and previously associated with the risk for schizophrenia may be adequate candidates in relation to functional connectivity alterations in schizophrenia. The objective was to study the association of two genes of voltage-gated ion channels (CACNA1C and KCNH2) with the functional modulation of the cortical networks measured with EEG and graph-theory parameter during a cognitive task, both in individuals with schizophrenia and healthy controls. Both CACNA1C (rs1006737) and KCNH2 (rs3800779) were genotyped in 101 controls and 50 schizophrenia patients. Small-world index (SW) was calculated from EEG recorded during an odd-ball task in two different temporal windows (pre-stimulus and response). Modulation was defined as the difference in SW between both windows. Genetic, group and their interaction effects on SW in the pre-stimulus window and in modulation were evaluated using ANOVA. The CACNA1C genotype was not associated with SW properties. KCNH2 was significantly associated with SW modulation. Healthy subjects showed a positive SW modulation irrespective of the KCNH2 genotype, whereas within patients allele-related differences were observed. Patients carrying the KCNH2 risk allele (A) presented a negative SW modulation and non-carriers showed SW modulation similar to the healthy subjects. Our data suggest that KCNH2 genotype contributes to the efficient modulation of brain electrophysiological activity during a cognitive task in schizophrenia patients.

Are Difficult-To-Study Populations too Difficult to Study in a Reliable Way?

Abstract. Replication studies, pre-registration, and increases in statistical power will likely improve the reliability of scientific evidence. However, these measures face critical limitations in populations that are inherently difficult to study. Members of difficult-to-study populations (e.g., patients, children, non-human animals) are less accessible to researchers, which typically results in small-sample studies that are infeasible to replicate. Nevertheless, meta-analyses on clinical neuropsychological data suggest that difficult-to-study populations can be studied in a reliable way. These analyses often produce unbiased effect-size estimates despite aggregating across severely underpowered original studies. This finding can be attributed to a neuropsychological research culture involving the non-selective reporting of results from standardized and validated test procedures. Consensus guidelines, test manuals, and psychometric evidence constrain the methodological choices made by neuropsychologists, who regularly report the results from neuropsychological test batteries irrespective of their statistical significance or novelty. Comparable shifts toward more standardization and validation, complete result reports, and between-lab collaborations can allow for a meaningful and reliable study of psychological phenomena in other difficult-to-study populations.

Sex differences in event-related potential (ERP) waveforms of primary psychotic disorders: A systematic review

Research aimed at understanding primary psychotic disorders such as schizophrenia, schizophreniform disorder, and schizoaffective disorder, with electrophysiological methods has flourished over recent years. However, a significant component that is often overlooked or underreported in electrophysiological research of psychosis is the factor of biological sex. Thus, the goal of this systematic review was to summarize the current understanding of EEG sex differences in primary psychotic disorders. Our study found a consistent sex difference relating to the P300 component (male amplitude < females), and that research examining sex differences of ERP waveforms, other than the P300, is very limited with ambiguous findings. This review also addressed the lack of consideration of sex as an influencing factor in electrophysiological research.

Association Between P300 Responses to Auditory Oddball Stimuli and Clinical Outcomes in the Psychosis Risk Syndrome

IMPORTANCE

In most patients, a prodromal period precedes the onset of schizophrenia. Although clinical criteria for identifying the psychosis risk syndrome (PRS) show promising predictive validity, assessment of neurophysiologic abnormalities in at-risk individuals may improve clinical prediction and clarify the pathogenesis of schizophrenia.

OBJECTIVE

To determine whether P300 event-related potential amplitude, which is deficient in schizophrenia, is reduced in the PRS and associated with clinical outcomes.

DESIGN, SETTING, AND PARTICIPANTS

Auditory P300 data were collected as part of the multisite, case-control North American Prodrome Longitudinal Study (NAPLS-2) at 8 university-based outpatient programs. Participants included 552 individuals meeting PRS criteria and 236 healthy controls with P300 data. Auditory P300 data of participants at risk who converted to psychosis (n = 73) were compared with those of nonconverters who were followed up for 24 months and continued to be symptomatic (n = 135) or remitted from the PRS (n = 90). Data were collected from May 27, 2009, to September 17, 2014, and were analyzed from December 3, 2015, to May 1, 2019.

MAIN OUTCOMES AND MEASURES

Baseline electroencephalography was recorded during an auditory oddball task. Two P300 subcomponents were measured: P3b, elicited by infrequent target stimuli, and P3a, elicited by infrequent nontarget novel stimuli.

RESULTS

This study included 788 participants. The PRS group (n = 552) included 236 females (42.8%) (mean [SD] age, 19.21 [4.38] years), and the healthy control group (n = 236) included 111 females (47.0%) (mean [SD] age, 20.44 [4.73] years). Target P3b and novelty P3a amplitudes were reduced in at-risk individuals vs healthy controls (d = 0.37). Target P3b, but not novelty P3a, was significantly reduced in psychosis converters vs nonconverters (d = 0.26), and smaller target P3b amplitude was associated with a shorter time to psychosis onset in at-risk individuals (hazard ratio, 1.45; 95% CI, 1.04-2.00; P = .03). Participants with the PRS who remitted had baseline target P3b amplitudes that were similar to those of healthy controls and greater than those of converters (d = 0.51) and at-risk individuals who remained symptomatic (d = 0.41).

CONCLUSIONS AND RELEVANCE

In this study, deficits in P300 amplitude appeared to precede psychosis onset. Target P3b amplitudes, in particular, may be sensitive to clinical outcomes in the PRS, including both conversion to psychosis and clinical remission. Auditory target P3b amplitude shows promise as a putative prognostic biomarker of clinical outcome in the PRS.

Auditory and Visual Oddball Stimulus Processing Deficits in Schizophrenia and the Psychosis Risk Syndrome: Forecasting Psychosis Risk With P300

Identification of neurophysiological abnormalities associated with schizophrenia that predate and predict psychosis onset may improve clinical prediction in the psychosis risk syndrome (PRS) and help elucidate the pathogenesis of schizophrenia. Amplitude reduction of the P300 event-related potential component reflects attention-mediated processing deficits and is among the most replicated biological findings in schizophrenia, making it a candidate biomarker of psychosis risk. The relative extent to which deficits in P300 amplitudes elicited by auditory and visual oddball stimuli precede psychosis onset during the PRS and predict transition to psychosis, however, remains unclear. Forty-three individuals meeting PRS criteria, 19 schizophrenia patients, and 43 healthy control (HC) participants completed baseline electroencephalography recording during separate auditory and visual oddball tasks. Two subcomponents of P300 were measured: P3b, elicited by infrequent target stimuli, and P3a, elicited by infrequent nontarget novel stimuli. Auditory and visual target P3b and novel P3a amplitudes were reduced in PRS and schizophrenia participants relative to HC participants. In addition, baseline auditory and visual target P3b, but not novel P3a, amplitudes were reduced in 15 PRS participants who later converted to psychosis, relative to 18 PRS non-converters who were followed for at least 22 months. Furthermore, target P3b amplitudes predicted time to psychosis onset among PRS participants. These results suggest that P300 amplitude deficits across auditory and visual modalities emerge early in the schizophrenia illness course and precede onset of full psychosis. Moreover, target P3b may represent an important neurophysiological vulnerability marker of the imminence of risk for psychosis.

Nonlinear dynamics underlying sensory processing dysfunction in schizophrenia

Natural systems, including the brain, often seem chaotic, since they are typically driven by complex nonlinear dynamical processes. Disruption in the fluid coordination of multiple brain regions contributes to impairments in information processing and the constellation of symptoms observed in neuropsychiatric disorders. Schizophrenia (SZ), one of the most debilitating mental illnesses, is thought to arise, in part, from such a network dysfunction, leading to impaired auditory information processing as well as cognitive and psychosocial deficits. Current approaches to neurophysiologic biomarker analyses predominantly rely on linear methods and may, therefore, fail to capture the wealth of information contained in whole EEG signals, including nonlinear dynamics. In this study, delay differential analysis (DDA), a nonlinear method based on embedding theory from theoretical physics, was applied to EEG recordings from 877 SZ patients and 753 nonpsychiatric comparison subjects (NCSs) who underwent mismatch negativity (MMN) testing via their participation in the Consortium on the Genetics of Schizophrenia (COGS-2) study. DDA revealed significant nonlinear dynamical architecture related to auditory information processing in both groups. Importantly, significant DDA changes preceded those observed with traditional linear methods. Marked abnormalities in both linear and nonlinear features were detected in SZ patients. These results illustrate the benefits of nonlinear analysis of brain signals and underscore the need for future studies to investigate the relationship between DDA features and pathophysiology of information processing.

Different Contexts in the Oddball Paradigm Induce Distinct Brain Networks in Generating the P300

Despite the P300 event-related potential (ERP) differences between distinct stimulus sequences, the effect of stimulus sequence on the brain network is still left unveiled. To uncover the corresponding effect of stimulus sequence, we thus investigated the differences of functional brain networks, when a target (T) or standard (S) stimulus was presented preceding another T as background context. Results of this study demonstrated that, when an S was first presented preceding a T (i.e., ST sequence), the P300 experiencing large amplitude was evoked by the T, along with strong network architecture. In contrast, if a T was presented in advance [i.e., target-to-target (TT) sequence], decreased P300 amplitude and attenuated network efficiency were demonstrated. Additionally, decreased activations in regions, such as inferior frontal gyrus and superior frontal gyrus were also revealed in TT sequence. Particularly, the effect of stimulus sequence on P300 network could be quantitatively measured by brain network properties, the increase in network efficiency corresponded to large P300 amplitude evoked in P300 task.

Cholinergic Mechanisms of Target Oddball Stimuli Detection: The Late "P300-Like" Event-Related Potential in Rats

Event-related potentials (ERPs) and oscillations (EROs) provide powerful tools for studying the brain's synaptic function underlying information processing. The P300 component of ERPs indexing attention and working memory shows abnormal amplitude and latency in neurological and psychiatric diseases that are sensitive to pharmacological agents. In the active auditory oddball discriminant paradigm, behavior and auditory-evoked potentials (AEPs) were simultaneously recorded in awake rats to investigate whether P300-like potentials generated in rats responding to rare target oddball tones are sensitive to subcutaneous modulation of the cholinergic tone by donepezil (1 mg/kg) and scopolamine (0.64 mg/kg). After operant training, rats consistently discriminate rare target auditory stimuli from frequent irrelevant nontarget auditory stimuli by a higher level of correct lever presses (i.e., accuracy) in target trials associated with a food reward. Donepezil attenuated the disruptive effect of scopolamine on the level of accuracy and premature responses in target trials. Larger P300-like peaks with early and late components were revealed in correct rare target stimuli trials as compared to frequent tones. Donepezil enhanced the peak amplitude of the P300-like component to target stimuli and evoked slow theta and gamma oscillations, whereas scopolamine altered the amplitude of the P300-like component and EROs to target stimuli. Pretreatment with donepezil attenuated effects of scopolamine on the peak amplitude of the P300-like component and on EROs. This study provides evidence that AEP P300-like responses can be elicited by rats engaged in attentive and memory processing of target stimuli and outline the relevance of the cholinergic system in stimulus discrimination processing. The findings highlight the sensitivity of this translational index for investigating brain circuits and/or novel pharmacological agents, which modulate cholinergic transmission associated with increased allocation of attentional resources.

A longitudinal, within-person investigation of the association between the P3 ERP component and externalizing behavior problems in young children

BACKGROUND

Externalizing problems, including aggression and conduct problems, are thought to involve impaired attentional capacities. Previous research suggests that the P3 event-related potential (ERP) component is an index of attentional processing, and diminished P3 amplitudes to infrequent stimuli have been shown to be associated with externalizing problems and attention-deficit/hyperactivity disorder (ADHD). However, the vast majority of this prior work has been cross-sectional and has not examined young children. The present study is the first investigation of whether within-individual changes in P3 amplitude predict changes in externalizing problems, providing a stronger test of developmental process.

METHOD

Participants included a community sample of children (N = 153) followed longitudinally at 30, 36, and 42 months of age. Children completed an oddball task while ERP data were recorded. Parents rated their children's aggression and ADHD symptoms.

RESULTS

Children's within-individual changes in the P3 amplitude predicted concomitant within-child changes in their aggression such that smaller P3 amplitudes (relative to a child's own mean) were associated with more aggression symptoms. However, changes in P3 amplitudes were not significantly associated with ADHD symptoms.

CONCLUSIONS

Findings suggest that the P3 may play a role in development of aggression, but do not support the notion that the P3 plays a role in development of early ADHD symptoms.

Variation in reward- and error-related neural measures attributable to age, gender, race, and ethnicity

Event-related potentials (ERPs) have been widely applied to the study of individual differences in reward and error processing, including recent proposals of several ERPs as possible biomarkers of mental illness. A criterion for all biomarkers, however, is that they be generalizable across the relevant populations, something which has yet to be demonstrated for many commonly studied reward- and error-related ERPs. The aim of this study was to examine variation in reward and error-related ERPs across core demographic variables: age, gender, race, and ethnicity. Data was drawn from three studies with relatively large samples (N range 207-527). Results demonstrated that ERPs varied across the demographic variables of interest. Several examples include attenuated reward-related ERPs with increasing age, larger error-related ERPs for men than women, and larger ERPs to feedback after losses for individuals who identified as Hispanic/Latino. Overall, these analyses suggest systematic variation in ERPs that is attributable to core demographic variables, which could give rise to seemingly inconsistent results across studies to the extent that these sample characteristics differ. Future psychophysiological studies should include these analyses as standard practice and assess how these differences might exacerbate, mask, or confound relationships of interest.

Gender effects on auditory P300: A systematic review

The evidence suggests that gender-related effects could influence the electrophysiological P300 parameters and stand as an additional source of variation for both clinical and non-clinical subjects. The aim of this paper is to characterize gender-related differences in P300 potential as elicited with simple auditory paradigms. This knowledge (1) is important for the practical assessment of P300 potential in normal and clinical populations, and (2) can provide an insight into the understanding of gender differences in pathophysiology, particularly those with differential risk or prevalence in males and females. With this review it is shown that a limited number of studies encounter possible gender effects on parameters of auditory P300, and the findings need to be read with caution due to methodological limitations of the studies. Nevertheless, evidence supports that the P300 amplitude could be significantly modulated by gender, with greater amplitude in females relative to males. Noteworthy, gender has a minimal effect on the P300 latency, and it is often comparable between males and females. Furthermore, the effect of gender on P300 could be modulated by hormonal background, anatomy and some methodological aspects.