Mismatch negativity and low frequency oscillations in schizophrenia families

Altered theta band and theta/beta ratio in mismatch negativity associate with treatment effect in schizophrenia with auditory hallucinations

Evidence suggests that attenuated mismatch negative (MMN) waves have a close link to auditory verbal hallucinations (AVH) and their clinical outcomes, especially impaired neural oscillations such as θ, β representing attentional control. In current study, thirty patients with schizophrenia and AVH (SZ) and twenty-nine healthy controls (HC) underwent multi-feature MMN paradigm measurements including frequency and duration deviant stimuli (fMMN and dMMN). Clinical symptoms and MMN paradigm were followed up among SZ group after 8-week treatment. Results demonstrated that hallucinating patients exhibited attenuated dMMN amplitudes across Fz (p = 0.010), F1 (p = 0.020) and F2 (p = 0.014) electrodes, which were trendily recovered after treatment. Meanwhile, θ band and TBR at frontal fMMN and right temporal dMMN were significantly reduced in SZs. After treatment, SZs showed reduced scores of Hoffman's Auditory Hallucinations Rating Scale (AHRS), with a remarkable recovery in right temporal TBR of dMMN (p = 0.042) and a trending change in frontal TBR of fMMN (p = 0.090). The β band was decreased in dMMN (p = 0.035) by time. Additionally, P3 scores of Positive and Negative Syndrome Scale (PANSS) were negatively correlated with θ band of fMMN at baseline. Baseline scores of AHRS negatively predicted changes of dMMN amplitude after treatment, and changes of β band in left temporal dMMN predicted the reduction in scores of PANSS negative scale. These findings supported that deficits in θ oscillation and TBR during auditory attention process were crucial to clinical progression of schizophrenia with AVH.

From the Laboratory to the Real-World: The Role of Mismatch Negativity in Psychosis

Mismatch negativity (MMN) has gained attention as a biomarker for psychosis and a translational intermediate phenotype in animal models of psychosis, including rodents and non-human primates. MMN has been linked to global functioning (Global Assessment of Functioning [GAF] score) and prognosis (psychosis onset or remission), suggesting that MMN reflects activities beyond auditory processing alone. This review examines the 45-year history of MMN from the perspective of psychiatric researchers and discusses current advances in computational and translational research on MMN, summarizing the current understanding of the MMN generation mechanism. We then address the essential question, "What do we observe through MMN?" Currently, we regard the relationship between global functioning in the real world and MMN as the key to answering this question. As a preliminary investigation, we analyzed the relationship between GAF as an objective variable and MMN, diagnosis, and basic epidemiological factors (age, sex, premorbid intelligence quotient) as explanatory variables (total n = 201, healthy controls: n = 41, patients with psychiatric disorders: n = 160) without assuming diagnostic categories. The relationship between functional outcomes and MMN was confirmed without a case-control design. Finally, we propose that new neurophysiological studies should acknowledge psychophysiological responses such as emotion, intention, and autonomic responses, as well as behavioral differences among participants beyond the dichotomy between healthy controls and patients. Measurements could be conducted in various settings from the participant's perspective. We discuss the potential for research investigating psychosis based on the interaction between individuals and the environment, using MMN as an illustrative model.

Duration mismatch negativity under varying deviant conditions in individuals with high schizotypal traits

Background

Although impaired auditory mismatch negativity (MMN) has consistently been found in individuals with schizophrenia, there are few and inconsistent reports on nonclinical individuals with schizotypy. To date, no studies have thoroughly assessed MMN with different degrees of deviant oddballs in nonclinical schizotypal samples. The aim of this study was to examine the extent of duration MMN (dMMN) amplitudes under two deviant duration conditions (large and small) in nonclinical participants with high schizotypal traits.

Methods

An extreme-group design was utilized, in which 63 participants from the schizotypy and control groups were selected from a pool of 1519 young adults using the Schizotypal Personality Questionnaire (SPQ). MMN was measured using passive duration oddball paradigms. Basic demographic information and musical backgrounds were assessed and matched, while depression and anxiety were evaluated and controlled for. The repeated measures analysis of covariance was utilized to evaluate differences in dMMN between groups. The Bonferroni correction was applied for multiple comparisons. Partial correlation and multiple linear regression analyses were conducted to investigate the association between dMMN amplitudes and SPQ scores.

Results

The amplitudes of dMMN at Cz were significantly increased under the large deviance condition in nonclinical schizotypal individuals (F = 4.36, p = .04). Large-deviance dMMN amplitudes at Fz were positively correlated with mild cognitive-perceptual symptoms in the control group (rp = .42, p = .03). However, as schizophrenia-like symptoms worsened and approached the clinical threshold for schizophrenia, small-deviance dMMN amplitudes at Cz showed negative associations with the cognitive-perceptual factor in the schizotypy group (rp = -.40, p = .04).

Conclusion

These results suggest the importance of considering the degree of deviation in duration when implementing the auditory oddball paradigm among nonclinical participants with schizotypal traits. In addition, our findings reveal a potential non-linear relationship between bottom-up auditory processing and the positive dimension of the schizophrenia spectrum.

Mismatch Negativity in Schizophrenia, Unaffected First-degree Relatives, and Healthy Controls

BACKGROUND

Mismatch negativity (MMN) amplitude is attenuated in schizophrenia patients (SZ). However, variability in illness course among SZ samples and types of deviant stimuli used in MMN paradigms have contributed to inconsistent findings across studies. Though MMN is suggested to be impaired in schizotypy, the potential link between the two is yet to be systematically examined in unaffected first-degree relatives of schizophrenia patients (FDR).

METHODS

The SZ sample had twenty-two drug-naïve or drug-free patients (dSZ) and thirty chronic/medicated patients (cSZ). dSZ and cSZ patients were compared with thirty-six unaffected FDR and thirty-two healthy controls (HC) using a two-tone passive auditory oddball MMN paradigm in an event-related potential experiment with two conditions (presented as separate blocks)-duration-deviant (duration-MMN) and frequency-deviant (frequency-MMN). Schizotypy scores and MMN indices were examined for correlation in FDR.

RESULTS

Duration-MMN amplitude was significantly attenuated in both dSZ and cSZ compared to other groups. dSZ and cSZ did not differ on MMN indices. Psychopathology scores and features of illness (illness duration, medication dosage, etc.) did not correlate with MMN indices. In FDR, Schizotypal trait measures did not correlate with MMN indices.

CONCLUSIONS

Duration-MMN emerged as a more robust indicator of prediction error signalling deficit in SZ. Frequency-MMN amplitude did not significantly differ among the groups, and MMN indices did not correlate with state and trait measures of schizophrenia-related psychopathology. These findings reiterates that auditory sensory processing captured by MMN is likely reflective of dynamic cognitive functions at the point of testing, and is unlikely to be an expression of enduring symptomatology.

Mismatch negativity and polygenic risk scores for schizophrenia and bipolar disorder

OBJECTIVE

Auditory mismatch negativity (MMN) impairment is a candidate endophenotype in psychotic disorders, yet the genetic underpinnings remain to be clarified. Here, we examined the relationships between auditory MMN and polygenic risk scores (PRS) for individuals with psychotic disorders, including schizophrenia spectrum disorders (SSD) and bipolar disorder (BD) and in healthy controls (HC).

METHODS

Genotyped and clinically well-characterized individuals with psychotic disorders (n = 102), including SSD (n = 43) and BD (n = 59), and HC (n = 397) underwent a roving MMN paradigm. In addition MMN, we measured the memory traces of the repetition positivity (RP) and the deviant negativity (DN), which is believed to reflect prediction encoding and prediction error signals, respectively. SCZ and BD PRS were computed using summary statistics from the latest genome-wide association studies. The relationships between the MMN, RP, and DN and the PRSs were assessed with linear regressions.

RESULTS

We found no significant association between the SCZ or BD PRS and grand average MMN in the psychotic disorders group or in the HCs group (all p > 0.05). SCZ PRS and BD PRS were negatively associated with RP in the psychotic disorders group (β = -0.46, t = -2.86, p = 0.005 and β = -0.29, t = -0.21, p = 0.034, respectively). No significant associations were found between DN and PRS.

CONCLUSION

These findings suggest that genetic variants associated with SCZ and BD may be associated with MMN subcomponents linked to predictive coding among patients with psychotic disorders. Larger studies are needed to confirm these findings and further elucidate the genetic underpinnings of MMN impairment in psychotic disorders.

Mismatch Negativity and Theta Oscillations Evoked by Auditory Deviance in Early Schizophrenia

BACKGROUND

Amplitude reduction of mismatch negativity (MMN), an event-related potential component indexing NMDA receptor-dependent auditory echoic memory and predictive coding, is widely replicated in schizophrenia. Time-frequency analyses of single-trial electroencephalography epochs suggest that theta oscillation abnormalities underlie MMN deficits in schizophrenia. However, this has received less attention in early schizophrenia (ESZ).

METHODS

Patients with ESZ (n = 89), within 5 years of illness onset, and healthy control subjects (n = 105) completed an electroencephalography MMN paradigm (duration-deviant, pitch-deviant, duration + pitch double-deviant). Repeated measures analyses of variance assessed group differences in MMN, theta intertrial phase coherence (ITC), and theta total power from frontocentral electrodes, after normal age adjustment. Group differences were retested after covarying MMN and theta measures.

RESULTS

Relative to healthy control subjects, patients with ESZ showed auditory deviance deficits. Patients with ESZ had MMN deficits for duration-deviants (p = .041), pitch-deviants (ps = .007), and double-deviants (ps < .047). Patients with ESZ had reduced theta ITC for standards (ps < .040) and duration-deviants (ps < .030). Furthermore, patients with ESZ had reduced theta power across deviants at central electrodes (p = .013). MMN group deficits were not fully accounted for by theta ITC and power, and neither were theta ITC group deficits fully accounted for by MMN. Group differences in theta total power were no longer significant after covarying for MMN.

CONCLUSIONS

Patients with ESZ showed reduced MMN and theta total power for all deviant types. Theta ITC showed a relatively specific reduction for duration-deviants. Although MMN and theta ITC were correlated in ESZ, covarying for one did not fully account for deficits in the other, raising the possibility of their sensitivity to dissociable pathophysiological processes.

Spectral and phase-coherence correlates of impaired auditory mismatch negativity (MMN) in schizophrenia: A MEG study

BACKGROUND

Reduced auditory mismatch negativity (MMN) is robustly impaired in schizophrenia. However, mechanisms underlying dysfunctional MMN generation remain incompletely understood. This study aimed to examine the role of evoked spectral power and phase-coherence towards deviance detection and its impairments in schizophrenia.

METHODS

Magnetoencephalography data was collected in 16 male schizophrenia patients and 16 male control participants during an auditory MMN paradigm. Analyses of event-related fields (ERF), spectral power and inter-trial phase-coherence (ITPC) focused on Heschl's gyrus, superior temporal gyrus, inferior/medial frontal gyrus and thalamus.

RESULTS

MMNm ERF amplitudes were reduced in patients in temporal, frontal and subcortical regions, accompanied by decreased theta-band responses, as well as by a diminished gamma-band response in auditory cortex. At theta/alpha frequencies, ITPC to deviant tones was reduced in patients in frontal cortex and thalamus. Patients were also characterized by aberrant responses to standard tones as indexed by reduced theta-/alpha-band power and ITPC in temporal and frontal regions. Moreover, stimulus-specific adaptation was decreased at theta/alpha frequencies in left temporal regions, which correlated with reduced MMNm spectral power and ERF amplitude. Finally, phase-reset of alpha-oscillations after deviant tones in left thalamus was impaired, which correlated with impaired MMNm generation in auditory cortex. Importantly, both non-rhythmic and rhythmic components of spectral activity contributed to the MMNm response.

CONCLUSIONS

Our data indicate that deficits in theta-/alpha- and gamma-band activity in cortical and subcortical regions as well as impaired spectral responses to standard sounds could constitute potential mechanisms for dysfunctional MMN generation in schizophrenia, providing a novel perspective towards MMN deficits in the disorder.

Time-frequency analyses of repetition suppression and change detection in children with neurofibromatosis type 1

Children with neurofibromatosis type 1 (NF1) are at increased risk of developing cognitive problems, including attention deficits and learning difficulties. Alterations in brain response to repetition and change have been evidenced in other genetic conditions associated with cognitive dysfunctions. Whether the integrity of these fundamental neural responses is compromised in school-aged children with NF1 is still unknown. In this study, we examined the repetition suppression (RS) and change detection responses in children with NF1 (n = 36) and neurotypical controls (n = 41) aged from 4 to 13 years old, using a simple sequence of vowels. We performed time-frequency analyses to compare spectral power and phase synchronization between groups, in the theta, alpha and beta frequency bands. Correlational analyses were performed between the neural responses and the level of intellectual functioning, as well as with behavioral symptoms of comorbid neurodevelopmental disorders measured through parental questionnaires. Children with NF1 showed preserved RS, but increased spectral power in the change detection response. Correlational analyses performed with measures of change detection revealed a negative association between the alpha-band spectral power and symptoms of inattention and hyperactivity. These findings suggest atypical neural response to change in children with NF1. Further studies should be conducted to clarify the interaction with comorbid neurodevelopmental disorders and the possible role of altered inhibitory mechanisms in this enhanced neural response.

The Role of Alpha Oscillations among the Main Neuropsychiatric Disorders in the Adult and Developing Human Brain: Evidence from the Last 10 Years of Research

Alpha oscillations (7-13 Hz) are the dominant rhythm in both the resting and active brain. Accordingly, translational research has provided evidence for the involvement of aberrant alpha activity in the onset of symptomatological features underlying syndromes such as autism, schizophrenia, major depression, and Attention Deficit and Hyperactivity Disorder (ADHD). However, findings on the matter are difficult to reconcile due to the variety of paradigms, analyses, and clinical phenotypes at play, not to mention recent technical and methodological advances in this domain. Herein, we seek to address this issue by reviewing the literature gathered on this topic over the last ten years. For each neuropsychiatric disorder, a dedicated section will be provided, containing a concise account of the current models proposing characteristic alterations of alpha rhythms as a core mechanism to trigger the associated symptomatology, as well as a summary of the most relevant studies and scientific contributions issued throughout the last decade. We conclude with some advice and recommendations that might improve future inquiries within this field.

Temporal and Spectral Properties of the Auditory Mismatch Negativity and P3a Responses in Schizophrenia

The mismatch negativity (MMN) event-related potential (ERP) indexes relatively automatic detection of changes in sensory stimuli and is typically attenuated in individuals with schizophrenia. However, contributions of different frequencies of electroencephalographic (EEG) activity to the MMN and the later P3a attentional orienting response in schizophrenia are poorly understood and were the focus of the present study. Participants with a schizophrenia-spectrum disorder (n = 85) and non-psychiatric control participants (n = 74) completed a passive auditory oddball task containing 10% 50 ms "deviant" tones and 90% 100 ms "standard" tones. EEG data were analyzed using spatial principal component analysis (PCA) applied to wavelet-based time-frequency analysis and MMN and P3a ERPs. The schizophrenia group compared to the control group had smaller MMN amplitudes and lower deviant-minus-standard theta but not alpha event-related spectral perturbation (ERSP) after accounting for participant age and sex. Larger MMN and P3a amplitudes but not latencies were correlated with greater theta and alpha time-frequency activity. Multiple linear regression analyses revealed that control participants showed robust relationships between larger MMN amplitudes and greater deviant-minus-standard theta inter-trial coherence (ITC) and between larger P3a amplitudes and greater deviant-minus-standard theta ERSP, whereas these dynamic neural processes were less tightly coupled in participants with a schizophrenia-spectrum disorder. Study results help clarify frequency-based contributions of time-domain (ie, ERP) responses and indicate a potential disturbance in the neural dynamics of detecting change in sensory stimuli in schizophrenia. Overall, findings add to the growing body of evidence that psychotic illness is associated with widespread neural dysfunction in the theta frequency band.

Test-retest reliability of mismatch negativity and gamma-band auditory steady-state response in patients with schizophrenia

Patients with schizophrenia show widespread impairments in clinical, cognitive and psychosocial functioning. Mismatch negativity (MMN) and gamma-band auditory steady-state response (ASSR) are two neurophysiological biomarkers widely used to inform diagnosis, guide treatments and track response to interventions in schizophrenia. However, evidence for the test-retest reliability of these indices across multiple sessions in schizophrenia patients remains scarce. In the present study, we included 34 schizophrenia patients (17 females) and obtained duration MMN (dMMN), frequency MMN (fMMN) and 40-Hz ASSR data across three sessions with intervals of 2 days. Event-related spectrum perturbation (ERSP) and inter-trial coherence (ITC) were calculated following Morlet wavelet time-frequency decomposition of ASSR data. The intra-class correlation coefficient (ICC) was used to quantify the reliability of MMN and ASSR measures among the three sessions. We found fair to good reliability for dMMN amplitudes but poor reliability for fMMN amplitudes. For the ASSR measures, ERSP showed good to excellent test-retest reliability while ITC had poor to fair test-retest reliability. In addition, the average of dMMN amplitudes was significantly correlated with that of ERSP across the three sessions. In summary, we established for the first time the short-term test-retest reliability of MMN and ASSR measures in schizophrenia patients. These findings demonstrate that dMMN amplitudes and ERSP of ASSR are reliable indices which may be used in longitudinal observational studies.

Mismatch negativity amplitude in first-degree relatives of individuals with psychotic disorders: Links with cognition and schizotypy

Mismatch negativity (MMN) amplitude is reliably reduced in psychotic disorders. While several studies have examined this effect in first-degree relatives of individuals with schizophrenia, few have sought to quantify deficits in relatives of individuals with other psychotic disorders. While some conclude that, compared to healthy subjects, first-degree relatives of schizophrenia show reduced MMN, others contradict this finding. Furthermore, though MMN is often shown to be associated with cognitive impairments and clinical symptoms in psychotic disorders, to our knowledge no studies have sought to fully examine these relationships in studies of first-degree relatives. The present study sought to clarify the extent of MMN amplitude reductions in a large sample of siblings of individuals with diverse psychotic disorders (n = 67), compared to probands with psychosis (n = 221) and never psychotic comparison subjects (n = 251). We further examined associations of MMN amplitude with cognition and schizotypal symptoms across these groups. We found that MMN amplitude was intact in siblings compared to probands. MMN amplitude was associated with cognition and schizotypal symptoms dimensionally across levels of familial risk. The present results imply that MMN reductions do not reflect genetic risk for psychotic disorders per se, and instead emerge as a result of, or in conjunction with, clinical features associated with psychosis. Such findings carry important implications for the utility of MMN amplitude as an indicator of inherited risk, and suggest that this component may be best conceptualized as an endophenotype for clinical symptoms and cognitive impairments, rather than risk for psychosis per se.

A Role for Somatostatin-Positive Interneurons in Neuro-Oscillatory and Information Processing Deficits in Schizophrenia

Alterations in neocortical GABAergic interneurons (INs) have been affiliated with neuropsychiatric diseases, including schizophrenia (SZ). Significant progress has been made linking the function of a specific subtype of GABAergic cells, parvalbumin (PV) positive INs, to altered gamma-band oscillations, which, in turn, underlie perceptual and feedforward information processing in cortical circuits. Here, we review a smaller but growing volume of literature focusing on a separate subtype of neocortical GABAergic INs, somatostatin (SST) positive INs. Despite sharing similar neurodevelopmental origins, SSTs exhibit distinct morphology and physiology from PVs. Like PVs, SSTs are altered in postmortem brain samples from multiple neocortical regions in SZ, although basic and translational research into consequences of SST dysfunction has been relatively sparse. We highlight a growing body of work in rodents, which now indicates that SSTs may also underlie specific aspects of cortical circuit function, namely low-frequency oscillations, disinhibition, and mediation of cortico-cortical feedback. SSTs may thereby support the coordination of local cortical information processing with more global spatial, temporal, and behavioral context, including predictive coding and working memory. These functions are notably deficient in some cases of SZ, as well as other neuropsychiatric disorders, emphasizing the importance of focusing on SSTs in future translational studies. Finally, we highlight the challenges that remain, including subtypes within the SST class.

Classification of First-Episode Schizophrenia, Chronic Schizophrenia and Healthy Control Based on Brain Network of Mismatch Negativity by Graph Neural Network

Mismatch negativity (MMN) has been consistently found deficit in schizophrenia, which was considered as a promising biomarker for assessing the impairments in pre-attentive auditory processing. However, the functional connectivity between brain regions based on MMN is not clear. This study provides an in-depth investigation in brain functional connectivity during MMN process among patients with first-episode schizophrenia (FESZ), chronic schizophrenia (CSZ) and healthy control (HC). Electroencephalography (EEG) data of 128 channels is recorded during frequency and duration MMN in 40 FESZ, 40 CSZ patients and 40 matched HC subjects. We reconstruct the cortical endogenous electrical activity from EEG recordings using exact low-resolution electromagnetic tomography and build functional brain networks based on source-level EEG data. Then, graph-theoretic features are extracted from the brain networks with the support vector machine (SVM) to classify FESZ, CSZ and HC groups, since the SVM has good generalization ability and robustness as a universally applicable nonlinear classifier. Furthermore, we introduce the graph neural network (GNN) model to directly learn for the network topology of brain network. Compared to HC, the damaged brain areas of CSZ are more extensive than FESZ, and the damaged area involved the auditory cortex. These results demonstrate the heterogeneity of the impacts of schizophrenia for different disease courses and the association between MMN and the auditory cortex. More importantly, the GNN classification results are significantly better than those of SVM, and hence the EEG-based GNN model of brain networks provides an effective method for discriminating among FESZ, CSZ and HC groups.

Cognitive Workload in an Auditory Digit Span Task When Memory Span Is in the Neighborhood of Seven Items

Abstract. Task performance of digit span has been widely used in the research on human short-term memory. The present study was conducted to show that the dynamic change of underlying mental effort can be further estimated by measuring the strength of theta oscillations at a forehead site on the scalp. Fourteen healthy adults ( Mage = 26.1 years) performed a passive listening (PL) task and an auditory digit span (DS) task, and electroencephalography (EEG) data were recorded simultaneously during the two tasks. Considering that the digit span paradigm has often been conducted in a non-laboratory location, the EEG data were collected with a wireless single-channel headset system. The headset system was validated in this study by replicating the EEG (an enhancement of frontal theta power) as well as event-related potential (N200 and P300) responses to the deviant tone stimuli in the PL task. The outcomes of the DS task showed that the memory span of the participants was at least eight items. Moreover, frontal theta power in response to a list of six to eight digits increased significantly. This pattern of results supports a hypothesis that additional mental effort is required for short-term retention of verbal items when the number of stimulus items exceeds the newly proposed limit of short-term memory capacity. Some strengths and limitations of the current EEG headset system are also discussed.

Transcriptome-wide association study reveals two genes that influence mismatch negativity

Mismatch negativity (MMN) is a differential electrophysiological response measuring cortical adaptability to unpredictable stimuli. MMN is consistently attenuated in patients with psychosis. However, the genetics of MMN are uncharted, limiting the validation of MMN as a psychosis endophenotype. Here, we perform a transcriptome-wide association study of 728 individuals, which reveals 2 genes (FAM89A and ENGASE) whose expression in cortical tissues is associated with MMN. Enrichment analyses of neurodevelopmental expression signatures show that genes associated with MMN tend to be overexpressed in the frontal cortex during prenatal development but are significantly downregulated in adulthood. Endophenotype ranking value calculations comparing MMN and three other candidate psychosis endophenotypes (lateral ventricular volume and two auditory-verbal learning measures) find MMN to be considerably superior. These results yield promising insights into sensory processing in the cortex and endorse the notion of MMN as a psychosis endophenotype.

Identifying Clinically and Functionally Distinct Groups Among Healthy Controls and First Episode Psychosis Patients by Clustering on EEG Patterns

OBJECTIVE

The mismatch negativity (MMN) is considered as a promising biomarker that can inform future therapeutic studies. However, there is a large variability among patients with first episode psychosis (FEP). Also, most studies report a single electrode site and on comparing case-control group differences. Few have taken advantage of the full wealth of multi-channel EEG signals to examine observable patterns. None, to our knowledge, have used machine learning (ML) approaches to investigate neurophysiological derived subgroups with distinct cognitive and functional outcome characteristics. In this study, we applied ML to empirically stratify individuals into homogeneous subgroups based on multi-channel MMN data. We then characterized the functional, cognitive, and clinical profiles of these neurobiologically derived subgroups. We also explored the underlying low frequency range responses (delta, theta, alpha) during MMN.

METHODS

Clinical, neurocognitive, functioning data of 33 healthy controls and 20 FEP patients were collected. 90% of the patients had 6-month follow-up data. Neurocognition, social cognition, and functioning measures were assessed using the NCCB Cognitive Battery, the Awareness of Social Inference Test, UCSD Performance-Based Skills Assessment, and Multnomah Community Ability Scale. Symptom severity was collected using the PANSS. MMN amplitude and single-trial derived low frequency activity across 24 frontocentral channels were used as main variables in the ML k-means clustering analyses.

RESULTS

We found a consistent pattern of two distinctive subgroups. We labeled them as "better functioning" and "poorer functioning" clusters, respectively. Each subgroup can be mapped onto either better or poorer clinical, cognitive, and functioning profiles. Also, we identified two subgroups of patients: one showed improved MMN and one showed worsening of MMN over time. Patients with improved MMN had better follow-up clinical, cognitive, and functioning profile than those with worsening MMN. Among the low frequency bands, delta frequency appeared to be the most relevant to the observed MMN responses in all individuals. However, higher delta responses were not necessarily associated with a better functioning profile, suggesting that delta frequency alone may not be useful in clinical characterization.

CONCLUSIONS

The ML approach could be a robust tool to explore heterogeneity and facilitate the identification of neurobiological homogeneous subgroups in FEP.

NMDA Receptor Antagonist Effects on Speech-Related Mismatch Negativity and Its Underlying Oscillatory and Source Activity in Healthy Humans

Background: Previous studies in schizophrenia have consistently shown that deficits in the generation of the auditory mismatch negativity (MMN) – a pre-attentive, event-related potential (ERP) typically elicited by changes to simple sound features – are linked to N-methyl-D-aspartate (NMDA) receptor hypofunction. Concomitant with extensive language dysfunction in schizophrenia, patients also exhibit MMN deficits to changes in speech but their relationship to NMDA-mediated neurotransmission is not clear. Accordingly, our study aimed to investigate speech MMNs in healthy humans and their underlying electrophysiological mechanisms in response to NMDA antagonist treatment. We also evaluated the relationship between baseline MMN/electrocortical activity and emergent schizophrenia-like symptoms associated with NMDA receptor blockade.

Methods: In a sample of 18 healthy volunteers, a multi-feature Finnish language paradigm incorporating changes in syllables, vowels and consonant stimuli was used to assess the acute effects of the NMDA receptor antagonist ketamine and placebo on the MMN. Further, measures of underlying neural activity, including evoked theta power, theta phase locking and source-localized current density in cortical regions of interest were assessed. Subjective symptoms were assessed with the Clinician Administered Dissociative States Scale (CADSS).

Results: Participants exhibited significant ketamine-induced increases in psychosis-like symptoms and depending on temporal or frontal recording region, co-occurred with reductions in MMN generation in response to syllable frequency/intensity, vowel duration, across vowel and consonant deviants. MMN attenuation was associated with decreases in evoked theta power, theta phase locking and diminished current density in auditory and inferior frontal (language-related cortical) regions. Baseline (placebo) MMN and underlying electrophysiological features associated with the processing of changes in syllable intensity correlated with the degree of psychotomimetic response to ketamine.

Conclusion: Ketamine-induced impairments in healthy human speech MMNs and their underlying electrocortical mechanisms closely resemble those observed in schizophrenia and support a model of dysfunctional NMDA receptor-mediated neurotransmission of language processing deficits in schizophrenia.

Rodent Mismatch Negativity/theta Neuro-Oscillatory Response as a Translational Neurophysiological Biomarker for N-Methyl-D-Aspartate Receptor-Based New Treatment Development in Schizophrenia

Deficits in the generation of auditory mismatch negativity (MMN) generation are among the most widely replicated neurophysiological abnormalities in schizophrenia and are linked to underlying dysfunction of N-methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission. Here, we evaluate physiological properties of rodent MMN, along with sensitivity to NMDAR agonist and antagonist treatments, relative to known patterns of dysfunction in schizophrenia. Epidural neurophysiological responses to frequency and duration deviants, along with responses to standard stimuli, were obtained at baseline and following 2 and 4 weeks' treatment in rats treated with saline, phencyclidine (PCP, 15 mg/kg/d by osmotic minipump), or PCP+glycine (16% by weight diet) interventions. Responses were analyzed using both event-related potential (ERP) and neuro-oscillatory (evoked power) approaches. At baseline, rodent duration MMN was associated with increased theta (θ)-frequency response similar to that observed in humans. PCP significantly reduced rodent duration MMN (p<0.001) and θ-band (p<0.01) response. PCP effects were prevented by concurrent glycine treatment (p<0.01 vs PCP alone). Effects related to stimulus-specific adaptation (SSA) were observed primarily in the alpha (α) and beta (β) frequency ranges. PCP treatment also significantly reduced α-frequency response to standard stimuli while increasing θ-band response, reproducing the pattern of deficit observed in schizophrenia. Overall, we demonstrate that rodent duration MMN shows neuro-oscillatory signature similar to human MMN, along with sensitivity to the NMDAR antagonist and agonist administration. These findings reinforce recent human studies linking MMN deficits to θ-band neuro-oscillatory dysfunction and support utility of rodent duration MMN as a translational biomarker for investigation of mechanisms underlying impaired local circuit function in schizophrenia.

Using EEG-Guided Basket and Umbrella Trials in Psychiatry: A Precision Medicine Approach for Cognitive Impairment in Schizophrenia

Due to advances over the last several decades, many fields of medicine are moving toward a precision medicine approach where treatments are tailored to nuanced patient factors. While in some disciplines these innovations are commonplace leading to unique biomarker-guided experimental medicine trials, there are no such analogs in psychiatry. In this brief review, we will overview two unique biomarker-guided trial designs for future use in psychiatry: basket and umbrella trials. We will illustrate how such trials could be useful in psychiatry using schizophrenia as a candidate illness, the EEG measure mismatch negativity as the candidate biomarker, and cognitive impairment as the target disease dimension.

A tale of two sites: Differential impairment of frequency and duration mismatch negativity across a primarily inpatient versus a primarily outpatient site in schizophrenia

Deficits in mismatch negativity (MMN) generation are among the best replicated neurophysiological deficits in schizophrenia, with reduced amplitude reflecting impaired information processing at the level of supratemporal auditory cortex. Differential patterns of MMN dysfunction according to deviant types have been reported across studies, with some research groups showing impairment in duration MMN but not frequency MMN, and other research groups reporting both findings. We evaluate the hypothesis that recruitment setting, reflecting current functional status, might be an important determinant of the pattern of MMN dysfunction. Here, we evaluated patterns of MMN dysfunction, along with tone matching and neuropsychological performance in subjects drawn from 1) a predominant inpatient/residential care setting (Nathan Kline Institute) and 2) a predominant outpatient setting (Columbia University). As predicted, compared to healthy controls, deficits in duration MMN were observed across sites, whereas deficits in frequency MMN/tone matching were confined to the chronic inpatient setting. Within patients, the frequency MMN deficit was highly correlated with impairments in tone matching ability across sites (r=-0.52, p<0.0001), as well as impairments in verbal learning (r=-0.54, p<0.0001). Responses to standard stimuli in the MMN paradigm were assessed using measures of alpha evoked power and inter-trial coherence (ITC). While deficits in alpha ITC were observed across sites (both p<0.05), deficits in alpha power were observed at the inpatient (p=0.001) but not outpatient (p=0.2) site. Overall, these finding indicate that impairments of frequency MMN generation and response power to standard stimuli could be particularly linked to forms of schizophrenia that are associated with poor functional outcome.

Improvement in mismatch negativity generation during d-serine treatment in schizophrenia: Correlation with symptoms

BACKGROUND

Deficits in N-methyl-d-aspartate-type (NMDAR) function contribute to symptoms and cognitive dysfunction in schizophrenia. The efficacy of NMDAR agonists in the treatment of persistent symptoms of schizophrenia has been variable, potentially reflecting limitations in functional target engagement. We recently demonstrated significant improvement in auditory mismatch negativity (MMN) with once-weekly treatment with d-serine, a naturally occurring NMDAR glycine-site agonist. This study investigates effects of continuous (daily) NMDAR agonists in schizophrenia/schizoaffective disorder.

METHODS

Primary analysis was on MMN after double-blind crossover (60mg/kg/d, n=16, 6weeks) treatment with d-serine/placebo. Secondary measures included clinical symptoms, neurocognition, and the effects of open-label (30-120mg/kg/d, n=21) d-serine and bitopertin/placebo (10mg, n=29), a glycine transport inhibitor.

RESULTS

Double-blind d-serine treatment led to significant improvement in MMN frequency (p=0.001, d=2.3) generation and clinical symptoms (p=0.023, d=0.80). MMN frequency correlated significantly with change in symptoms (r=-0.63, p=0.002) following co-variation for treatment type. d-Serine treatment led to a significant, large effect size increase vs. placebo in evoked α-power in response to standards (p=0.036, d=0.81), appearing to normalize evoked α power relative to previous findings with controls. While similar results were seen with open-label d-serine, no significant effects of bitopertin were observed for symptoms or MMN.

CONCLUSIONS

These findings represent the first randomized double-blind placebo-controlled study with 60mg/kg d-serine in schizophrenia, and are consistent with meta-analyses showing significant effects of d-serine in schizophrenia. Results overall support suggest that MMN may have negative, as well as positive, predictive value in predicting efficacy of novel compounds.

CLINICAL TRIALS REGISTRATION

Clinicaltrials.gov: NCT00322023/NCT00817336 (d-serine); NCT01116830 (bitopertin).

Meta-analysis of mismatch negativity to simple versus complex deviants in schizophrenia

Mismatch negativity (MMN) deficits in schizophrenia (SCZ) have been studied extensively since the early 1990s, with the vast majority of studies using simple auditory oddball task deviants that vary in a single acoustic dimension such as pitch or duration. There has been a growing interest in using more complex deviants that violate more abstract rules to probe higher order cognitive deficits. It is still unclear how sensory processing deficits compare to and contribute to higher order cognitive dysfunction, which can be investigated with later attention-dependent auditory event-related potential (ERP) components such as a subcomponent of P300, P3b. In this meta-analysis, we compared MMN deficits in SCZ using simple deviants to more complex deviants. We also pooled studies that measured MMN and P3b in the same study sample and examined the relationship between MMN and P3b deficits within study samples. Our analysis reveals that, to date, studies using simple deviants demonstrate larger deficits than those using complex deviants, with effect sizes in the range of moderate to large. The difference in effect sizes between deviant types was reduced significantly when accounting for magnitude of MMN measured in healthy controls. P3b deficits, while large, were only modestly greater than MMN deficits (d=0.21). Taken together, our findings suggest that MMN to simple deviants may still be optimal as a biomarker for SCZ and that sensory processing dysfunction contributes significantly to MMN deficit and disease pathophysiology.

Mismatch negativity as a biomarker of theta band oscillatory dysfunction in schizophrenia

Mismatch negativity (MMN) is among the best established biomarkers of cortical dysfunction in schizophrenia. MMN generators are localized primarily to primary and secondary auditory regions, and are known to reflect activity mediated by cortical N-methyl-d-aspartate-type glutamate receptors (NMDAR). Nevertheless, mechanisms underlying MMN generation at the local circuit level remain incompletely understood. This review synthesizes recent advances in circuit-level conceptualization of MMN based upon neuro-oscillatory findings. In the neuro-oscillatory (aka event-related spectral perturbation, ERSP) approach, responses to sensory stimuli are decomposed into underlying frequency bands prior to analysis. MMN reflects activity primarily in theta (4-7Hz) frequency band, which is thought to depend primarily upon interplay between cortical pyramidal neurons and somatostatin (SST)-type local circuit GABAergic interneurons. Schizophrenia-related deficits in theta generation are also observed not only in MMN, but also in other auditory and visual contexts. At the local circuit level, SST interneurons are known to maintain tonic inhibition over cortical pyramidal interneurons. SST interneurons, in turn, are inhibited by a class of interneurons expressing vasoactive intestinal polypeptide (VIP). In rodents, SST interneurons have been shown to respond differentially to deviant vs. standard stimuli, and inhibition of SST interneurons has been found to selectively inhibit deviance-related activity in rodent visual cortex. Here we propose that deficits in theta frequency generation, as exemplified by MMN, may contribute significantly to cortical dysfunction in schizophrenia, and may be tied to impaired interplay between cortical pyramidal neurons and local circuit SST-type GABAergic interneurons.

Neural mechanisms of mismatch negativity dysfunction in schizophrenia

Schizophrenia is associated with cognitive deficits that reflect impaired cortical information processing. Mismatch negativity (MMN) indexes pre-attentive information processing dysfunction at the level of primary auditory cortex. This study investigates mechanisms underlying MMN impairments in schizophrenia using event-related potential, event-related spectral decomposition (ERSP) and resting state functional connectivity (rsfcMRI) approaches. For this study, MMN data to frequency, intensity and duration-deviants were analyzed from 69 schizophrenia patients and 38 healthy controls. rsfcMRI was obtained from a subsample of 38 patients and 23 controls. As expected, schizophrenia patients showed highly significant, large effect size (P=0.0004, d=1.0) deficits in MMN generation across deviant types. In ERSP analyses, responses to deviants occurred primarily the theta (4-7 Hz) frequency range consistent with distributed corticocortical processing, whereas responses to standards occurred primarily in alpha (8-12 Hz) range consistent with known frequencies of thalamocortical activation. Independent deficits in schizophrenia were observed in both the theta response to deviants (P=0.021) and the alpha-response to standards (P=0.003). At the single-trial level, differential patterns of response were observed for frequency vs duration/intensity deviants, along with At the network level, MMN deficits engaged canonical somatomotor, ventral attention and default networks, with a differential pattern of engagement across deviant types (P<0.0001). Findings indicate that deficits in thalamocortical, as well as corticocortical, connectivity contribute to auditory dysfunction in schizophrenia. In addition, differences in ERSP and rsfcMRI profiles across deviant types suggest potential differential engagement of underlying generator mechanisms.

Spatio-temporal source cluster analysis reveals fronto-temporal auditory change processing differences within a shared autistic and schizotypal trait phenotype

Social Disorganisation (SD) is a shared autistic and schizotypal phenotype that is present in the subclinical population. Auditory processing deficits, particularly in mismatch negativity/field (MMN/F) have been reported across both spectrum disorders. This study investigates differences in MMN/F cortical spatio-temporal source activity between higher and lower quintiles of the SD spectrum.

Sixteen low (9 female) and 19 high (9 female) SD subclinical adults (18–40years) underwent magnetoencephalography (MEG) during an MMF paradigm where standard tones (50ms) were interrupted by infrequent duration deviants (100ms).

Spatio-temporal source cluster analysis with permutation testing revealed no difference between the groups in source activation to the standard tone. To the deviant tone however, there was significantly reduced right hemisphere fronto-temporal and insular cortex activation for the high SD group (p= 0.038). The MMF, as a product of the cortical response to the deviant minus that to the standard, did not differ significantly between the high and low Social Disorganisation groups.

These data demonstrate a deficit in right fronto-temporal processing of an auditory change for those with more of the shared SD phenotype, indicating that right fronto-temporal auditory processing may be associated with psychosocial functioning.

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Autism and schizotypal spectra share a trait phenotype, Social Disorganisation (SD).

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Auditory mismatch paradigm demonstrates processing differences between high and low SD.

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High SD scorers have reduced fronto-temporal response to auditory change.

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Reduced fronto-temporal source activation in high SD is right lateralised.

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Psychosocial function is related to auditory deviant processing.

Mismatch field latency, but not power, may mark a shared autistic and schizotypal trait phenotype

The auditory mismatch negativity (MMN), a preattentive processing potential, and its magnetic counterpart (MMF) are consistently reported as reduced in schizophrenia and autism spectrum disorders. This study investigates whether MMF characteristics differ between subclinically high and low scorers on the recently discovered shared autism and schizophrenia phenotype, Social Disorganisation. A total of 18 low (10 females) and 19 high (9 females) Social Disorganisation scorers underwent magnetoencephalography (MEG) during a MMF paradigm of 50ms standard (1000Hz, 85%) and 100ms duration deviant tones. MMF was measured from the strongest active magnetometer over the right and left hemispheres (consistent across groups) after 100ms. No differences in MMF power were found, however there was a significant delay in the MMF peak (p=0.007). The P3am (following the MMF) was significantly reduced across both hemispheres for the high Social Disorganisation group (p=0.025), there were no specific hemispheric differences in P3am power or latency. Right MMF peak latency increased with higher scores on the schizotypal subscales Odd Speech, Odd Behaviour and Constricted Affect. Findings suggest that MMF peak latency delay marks a convergence of the autism and schizophrenia spectra at a subclinical. These findings have significant implications for future research methodology, as well as clinical practice.

A Meta-analytic Review of Auditory Event-Related Potential Components as Endophenotypes for Schizophrenia: Perspectives From First-Degree Relatives

INTRODUCTION

As endophenotypes bridge the gap between genetics and phenotypic disease expression, identifying reliable markers is important for fostering understanding of pathophysiology. The present aim was to conduct current meta-analyses of 3 key auditory event-related potential (ERP) components that have been held as potential endophenotypes for schizophrenia: P50, P300 amplitude and latency, and mismatch negativity (MMN), reflective of sensory gating, attention and classification speed, and perceptual discrimination ability, respectively. In order to assess endophenotype viability, these components were examined in unaffected relatives of patients with schizophrenia and healthy controls.

METHODS

Effect sizes (ES) were examined between relatives and controls for P50 suppression (10 studies, n = 360 relatives, 473 controls), P300 amplitude (20 studies, n = 868 relatives, 961 controls), P300 latency (17 studies, n = 674 relatives, 792 controls), and MMN (11 studies, n = 377 relatives, 552 controls).

RESULTS

Reliable differences in P50 suppression (ES = 0.86, P < .001), P300 amplitude (ES = -0.52, P < .001), and P300 latency (ES = 0.44, P < .05) were found between unaffected relatives and controls. A trend was found between relatives and controls for MMN (ES = 0.21, P = 0.06), and the use of extraneous channels was found to be a significant moderator (P = 0.01). When MMN was analyzed using frontocentral channel Fz, a significant difference was found (ES = 0.26, P < 0.01).

DISCUSSION

The results indicate that P50 suppression, P300 amplitude and P300 latency, and MMN may serve as viable endophenotypes for schizophrenia.

Schizotypy and auditory mismatch negativity in a non-clinical sample of young adults

Schizophrenia may be conceptualised using a dimensional approach to examine trait-like expression such as schizotypy within non-clinical populations to better understand pathophysiology. A candidate psychosis-risk marker, the auditory mismatch negativity (MMN) is thought to index the functionality of glutamatergic NMDA receptor mediated neurotransmission. Although the MMN is robustly reduced in patients with schizophrenia, the association between MMN and schizotypy in the general population is under-investigated. Thirty-five healthy participants completed the Schizotypal Personality Questionnaire (SPQ) and a multi-feature MMN paradigm (standards 82%, 50ms, 1000Hz, 80dB) with duration (100ms), frequency (1200Hz) and intensity (90dB) deviants (6% each). Spearman's correlations were used to explore the association between schizotypal personality traits and MMN amplitude. Few associations were identified between schizotypal traits and MMN. Higher Suspiciousness subscale scores tended to be correlated with larger frequency MMN amplitude. A median-split comparison of the sample on Suspiciousness scores showed larger MMN (irrespective of deviant condition) in the High compared to the Low Suspiciousness group. The trend-level association between MMN and Suspiciousness is in contrast to the robustly attenuated MMN amplitude observed in schizophrenia. Reductions in MMN may reflect a schizophrenia-disease state, whereas non-clinical schizotypy may not be subserved by similar neuropathology.

Neural indices of phonemic discrimination and sentence-level speech intelligibility in quiet and noise: A mismatch negativity study

Successful speech communication requires the extraction of important acoustic cues from irrelevant background noise. In order to better understand this process, this study examined the effects of background noise on mismatch negativity (MMN) latency, amplitude, and spectral power measures as well as behavioral speech intelligibility tasks. Auditory event-related potentials (AERPs) were obtained from 15 normal-hearing participants to determine whether pre-attentive MMN measures recorded in response to a consonant (from /ba/ to /bu/) and vowel change (from /ba/ to /da/) in a double-oddball paradigm can predict sentence-level speech perception. The results showed that background noise increased MMN latencies and decreased MMN amplitudes with a reduction in the theta frequency band power. Differential noise-induced effects were observed for the pre-attentive processing of consonant and vowel changes due to different degrees of signal degradation by noise. Linear mixed-effects models further revealed significant correlations between the MMN measures and speech intelligibility scores across conditions and stimuli. These results confirm the utility of MMN as an objective neural marker for understanding noise-induced variations as well as individual differences in speech perception, which has important implications for potential clinical applications.

Neurophysiological evidence of impaired self-monitoring in schizotypal personality disorder and its reversal by dopaminergic antagonism

Background

Schizotypal personality disorder (SPD) is a schizophrenia-spectrum disorder characterized by odd or bizarre behavior, strange speech, magical thinking, unusual perceptual experiences, and social anhedonia. Schizophrenia proper has been associated with anomalies in dopaminergic neurotransmission and deficits in neurophysiological markers of self-monitoring, such as low amplitude in cognitive event-related brain potentials (ERPs) like the error-related negativity (ERN), and the error positivity (Pe). These components occur after performance errors, rely on adequate fronto-striatal function, and are sensitive to dopaminergic modulation. Here we postulated that analogous to observations in schizophrenia, SPD individuals would show deficits in self-monitoring, as measured by the ERN and the Pe. We also assessed the capacity of dopaminergic antagonists to reverse these postulated deficits.

Methods

We recorded the electroencephalogram (EEG) from 9 SPD individuals and 12 healthy controls in two separate experimental sessions while they performed the Eriksen Flanker Task, a classical task recruiting behavioral monitoring. Participants received a placebo or 1 mg risperidone according to a double-blind randomized design.

Results

After placebo, SPD individuals showed slower reaction times to hits, longer correction times following errors and reduced ERN and Pe amplitudes. While risperidone impaired performance and decreased ERN and Pe in the control group, it led to behavioral improvements and ERN amplitude increases in the SPD individuals.

Conclusions

These results indicate that SPD individuals show deficits in self-monitoring analogous to those in schizophrenia. These deficits can be evidenced by neurophysiological measures, suggest a dopaminergic imbalance, and can be reverted by dopaminergic antagonists.

Frontal Glutamate and γ-Aminobutyric Acid Levels and Their Associations With Mismatch Negativity and Digit Sequencing Task Performance in Schizophrenia

IMPORTANCE

Auditory mismatch negativity (MMN) is a biomarker for schizophrenia thought to reflect glutamatergic N-methyl-d-aspartate receptor function and excitatory-inhibitory neurotransmission balance. However, the association of glutamate level with MMN has not been directly examined in patients with schizophrenia, to our knowledge.

OBJECTIVE

To investigate the contributions of glutamate and γ-aminobutyric acid (GABA) to MMN and digit sequencing task (DST) performance, an assessment of verbal working memory, in schizophrenia.

DESIGN, SETTING, AND PARTICIPANTS

Fifty-three control participants from the community and 45 persons with schizophrenia from outpatient clinics completed an electroencephalographic session for MMN, magnetic resonance spectroscopy for glutamate and GABA, and a DST. The study dates were July 2011 to May 2014, and the dates of our analysis were May 2014 to August 2015.

MAIN OUTCOMES AND MEASURES

Glutamate, GABA, the ratio of glutamine to glutamate, MMN amplitude, and DST. Structural equation modeling was used to test the effects of neurochemistry and MMN amplitude on DST performance.

RESULTS

The 45 persons with schizophrenia were a mean (SD) of 37.7 (12.8) years and the control participants were 37.1 (13.1) years. The schizophrenia group had a mean (SD) of 14.7 (12.1) years of illness. Mismatch negativity amplitude (F = 4.39, P = .04) and glutamate (F = 9.69, P = .002) were reduced in the schizophrenia group. Smaller MMN amplitude was significantly associated with lower GABA level (P = .008), lower glutamate level (P = .05), and higher ratio of glutamine to glutamate (P = .003). Reduced MMN amplitude was linked to poor verbal working memory in schizophrenia (P = .002). Modeling revealed that a proxy of glutamatergic function, indexed by the ratio of glutamine to glutamate, influenced a path from the ratio of glutamine to glutamate to MMN to verbal working memory (P = .38 [root-mean-square error of approximation, P < .001] by χ2 test), supporting the contention that MMN serves as an intermediate biomarker linking glutamatergic function to DST performance in schizophrenia.

CONCLUSIONS AND RELEVANCE

The role of glutamate and GABA in MMN and verbal working memory deficits in schizophrenia has been frequently debated. These data provide in vivo evidence that support glutamatergic and GABAergic regulation of MMN and verbal working memory function in schizophrenia.

Impaired prefrontal synaptic gain in people with psychosis and their relatives during the mismatch negativity

The mismatch negativity (MMN) evoked potential, a preattentive brain response to a discriminable change in auditory stimulation, is significantly reduced in psychosis. Glutamatergic theories of psychosis propose that hypofunction of NMDA receptors (on pyramidal cells and inhibitory interneurons) causes a loss of synaptic gain control. We measured changes in neuronal effective connectivity underlying the MMN using dynamic causal modeling (DCM), where the gain (excitability) of superficial pyramidal cells is explicitly parameterised. EEG data were obtained during a MMN task—for 24 patients with psychosis, 25 of their first‐degree unaffected relatives, and 35 controls—and DCM was used to estimate the excitability (modeled as self‐inhibition) of (source‐specific) superficial pyramidal populations. The MMN sources, based on previous research, included primary and secondary auditory cortices, and the right inferior frontal gyrus. Both patients with psychosis and unaffected relatives (to a lesser degree) showed increased excitability in right inferior frontal gyrus across task conditions, compared to controls. Furthermore, in the same region, both patients and their relatives showed a reversal of the normal response to deviant stimuli; that is, a decrease in excitability in comparison to standard conditions. Our results suggest that psychosis and genetic risk for the illness are associated with both context‐dependent (condition‐specific) and context‐independent abnormalities of the excitability of superficial pyramidal cell populations in the MMN paradigm. These abnormalities could relate to NMDA receptor hypofunction on both pyramidal cells and inhibitory interneurons, and appear to be linked to the genetic aetiology of the illness, thereby constituting potential endophenotypes for psychosis. Hum Brain Mapp 37:351–365, 2016. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Altered Spontaneous Brain Activity in Schizophrenia: A Meta-Analysis and a Large-Sample Study

Altered spontaneous brain activity as measured by ALFF, fALFF, and ReHo has been reported in schizophrenia, but no consensus has been reached on alternations of these indexes in the disorder. We aimed to clarify the regional alterations in ALFF, fALFF, and ReHo in schizophrenia using a meta-analysis and a large-sample validation. A meta-analysis of activation likelihood estimation was conducted based on the abnormal foci of ten studies. A large sample of 86 schizophrenia patients and 89 healthy controls was compared to verify the results of the meta-analysis. Meta-analysis demonstrated that the alternations in ALFF and ReHo had similar distribution in schizophrenia patients. The foci with decreased ALFF/fALFF and ReHo in schizophrenia were mainly located in the somatosensory cortex, posterior parietal cortex, and occipital cortex; however, foci with increased ALFF/fALFF and ReHo were mainly located in the bilateral striatum, medial temporal cortex, and medial prefrontal cortex. The large-sample study showed consistent findings with the meta-analysis. These findings may expound the pathophysiological hypothesis and guide future research.

Sensory processing dysfunction in the personal experience and neuronal machinery of schizophrenia

Sensory processing deficits, first investigated by Kraepelin and Bleuler as possible pathophysiological mechanisms in schizophrenia, are now being recharacterized in the context of our current understanding of the molecular and neurobiological brain mechanisms involved. The National Institute of Mental Health Research Domain Criteria position these deficits as intermediaries between molecular and cellular mechanisms and clinical symptoms of schizophrenia, such as hallucinations. The prepulse inhibition of startle responses by a weaker preceding tone, the inhibitory gating of response to paired sensory stimuli characterized using the auditory P50 evoked response, and the detection of slight deviations in patterns of sensory stimulation eliciting the cortical mismatch negativity potential demonstrate deficits in early sensory processing mechanisms, whose molecular and neurobiological bases are increasingly well understood. Deficits in sensory processing underlie more complex cognitive dysfunction and are in turn affected by higher-level cognitive difficulties. These deficits are now being used to identify genes involved in familial transmission of schizophrenia and to monitor potentially therapeutic drug effects for both treatment and prevention. This research also provides a clinical reminder that patients' sensory perception of the surrounding world, even during treatment sessions, may differ considerably from others' perceptions. A person's ability to understand and interact effectively with the surrounding world ultimately depends on an underlying sensory experience of it.

Mismatch negativity: translating the potential

The mismatch negativity (MMN) component of the auditory event-related potential has become a valuable tool in cognitive neuroscience. Its reduced size in persons with schizophrenia is of unknown origin but theories proposed include links to problems in experience-dependent plasticity reliant on N-methyl-d-aspartate glutamate receptors. In this review we address the utility of this tool in revealing the nature and time course of problems in perceptual inference in this illness together with its potential for use in translational research testing animal models of schizophrenia-related phenotypes. Specifically, we review the reasons for interest in MMN in schizophrenia, issues pertaining to the measurement of MMN, its use as a vulnerability index for the development of schizophrenia, the pharmacological sensitivity of MMN and the progress in developing animal models of MMN. Within this process we highlight the challenges posed by knowledge gaps pertaining to the tool and the pharmacology of the underlying system.

A review of recent literature employing electroencephalographic techniques to study the pathophysiology, phenomenology, and treatment response of schizophrenia

Clinical experience and research findings suggest that schizophrenia is a disorder comprised of multiple genetic and neurophysiological subtypes with differential response to treatment. Electroencephalography (EEG) is a non-invasive, inexpensive and useful tool for investigating the neurobiology of schizophrenia and its subtypes. EEG studies elucidate the neurophysiological mechanisms potentially underlying clinical symptomatology. In this review article recent advances in applying EEG to study pathophysiology, phenomenology, and treatment response in schizophrenia are discussed. Investigative strategies employed include: analyzing quantitative EEG (QEEG) spectral power during the resting state and cognitive tasks; applying machine learning methods to identify QEEG indicators of diagnosis and treatment response; and using the event-related brain potential (ERP) technique to characterize the neurocognitive processes underlying clinical symptoms. Studies attempting to validate potential EEG biomarkers of schizophrenia and its symptoms, which could be useful in assessing familial risk and treatment response, are also reviewed.