Mismatch Negativity in Response to Auditory Deviance and Risk for Future Psychosis in Youth at Clinical High Risk for Psychosis

The electroencephalography protocol for the Accelerating Medicines Partnership® Schizophrenia Program: Reliability and stability of measures

Individuals at clinical high risk for psychosis (CHR) have variable clinical outcomes and low conversion rates, limiting development of novel and personalized treatments. Moreover, given risks of antipsychotic drugs, safer effective medications for CHR individuals are needed. The Accelerating Medicines Partnership® Schizophrenia (AMP® SCZ) Program was launched to address this need. Based on past CHR and schizophrenia studies, AMP SCZ assessed electroencephalography (EEG)-based event-related potential (ERP), event-related oscillation (ERO), and resting EEG power spectral density (PSD) measures, including mismatch negativity (MMN), auditory and visual P300 to target (P3b) and novel (P3a) stimuli, 40-Hz auditory steady state response, and resting EEG PSD for traditional frequency bands (eyes open/closed). Here, in an interim analysis of AMP SCZ EEG measures, we assess test-retest reliability and stability over sessions (baseline, month-2 follow-up) in CHR (n = 654) and community control (CON; n = 87) participants. Reliability was calculated as Generalizability (G)-coefficients, and changes over session were assessed with paired t-tests. G-coefficients were generally good to excellent in both groups (CHR: mean = 0.72, range = 0.49-0.85; CON: mean = 0.71, range = 0.44-0.89). Measure magnitudes significantly (p < 0.001) decreased over session (MMN, auditory and visual target P3b, visual novel P3a, 40-Hz ASSR) and/or over runs within sessions (MMN, auditory/visual novel P3a and target P3b), consistent with habituation effects. Despite these small systematic habituation effects, test-retest reliabilities of the AMP SCZ EEG-based measures are sufficiently strong to support their use in CHR studies as potential predictors of clinical outcomes, markers of illness progression, and/or target engagement or secondary outcome measures in controlled clinical trials.

Neighborhood social fragmentation in relation to impaired mismatch negativity among youth at clinical high risk for psychosis and healthy comparisons

Impairments in mismatch negativity (MMN) are well-established in schizophrenia and have been observed in youth at clinical high-risk for psychosis (CHR-P). Prior animal studies have shown that social isolation may be related to neurobiological changes, including reduced MMN-like responses and schizophrenia-like behaviors. In parallel, neighborhood social fragmentation has been shown to be associated with the onset of psychosis. This study investigates the association between neighborhood social fragmentation and MMN impairment among CHR-P youth and healthy comparisons (HC). Data were collected from the North American Prodrome Longitudinal Study Phase 2. Electroencephalography was recorded during an unattended auditory oddball paradigm with duration-, pitch-, and double-deviant tones. Generalized linear mixed models tested the association between neighborhood social fragmentation and the frontal-central averaged MMN for three deviant types for youth at CHR-P and HC separately. The models adjusted for age, sex, race/ethnicity, parental education, parental history of psychosis, and neighborhood poverty. Participants (mean [SD] age: 18.69 [4.59], 41.9% females, 51.3% White non-Hispanic) included 304 CHR-P and 92 HC. In the CHR-P group, greater neighborhood social fragmentation was associated with impaired duration-deviant MMN (bootstrapped β = 0.18, 95% CI: 0.04 to 0.33, p = .022) but not for pitch-deviant (bootstrapped β = 0.09, 95% CI: -0.05 to 0.22, p = .199) or double-deviant MMN (bootstrapped β = 0.10, 95% CI: -0.09 to 0.17, p = .559). Greater neighborhood social fragmentation was associated with impaired duration-deviant MMN amplitude among high-risk individuals. Further research is needed to explore underlying mechanisms.

Unveiling distinct representations of P3a in schizophrenia through two-stimulus and three-stimulus auditory oddball paradigms

BACKGROUND

P3a event-related potential (ERP) is considered a potential biomarker for schizophrenia (SZ), can be elicited through both passive two-stimulus and active three-stimulus auditory oddball paradigms. While both types of P3a reflect involuntary attention shifts, the nuanced understanding of what P3a represents in different contexts is important and rarely studied. This study aims to examine correlations between P3a ERPs elicited from different paradigms and associations of each P3a with cognitive function, clinical symptoms, and antipsychotic medication.

METHODS

Our sample included 178 SZ patients and 127 healthy controls (HC). Data on two-stimulus paradigm, three-stimulus oddball paradigm, Chinese version of MATRICS Consensus Cognitive Battery (MCCB), symptom severity, and medication use were collected.

RESULTS

In both paradigms, SZ group's P3a amplitude was significantly reduced compared to HC's (both p < 0.05). P3a evoked by the two-stimulus paradigm and the three-stimulus paradigm were not correlated (r = -0.06, p = 0.661). Three-stimulus paradigm-P3a was significantly correlated with attention/vigilance (r = 0.27, p = 0.017) in SZ, and with working memory (r = 0.39, p = 0.001) and overall MCCB score (r = 0.25, p = 0.042) in HC. Additionally, the two-stimulus paradigm-P3a correlated with olanzapine equivalent antipsychotic dose (r = -0.26, p = 0.022).

CONCLUSIONS

Our findings offer new insights into the role of P3a in clinical research. P3a ERPs from different paradigms may represent functionally distinct components. The context in which the P3a is elicited should be taken into account when discussing its functional or neurocognitive significance.

Predictive routing emerges from self-supervised stochastic neural plasticity

Neurophysiology studies propose that predictive coding is implemented via alpha/beta (8-30 Hz) rhythms preparing specific pathways to process predicted inputs. This leads to a state of relative inhibition, reducing feedforward gamma (40-90 Hz) rhythms and spiking for predictable inputs. This is called predictive routing model. It is unclear which circuit mechanisms implement this push-pull interaction between alpha/beta and gamma rhythms. To explore how predictive routing is implemented, we developed a self-supervised learning algorithm we call generalized Stochastic Delta Rule (gSDR). Development of this algorithm was necessary because manual tuning of parameters (frequently used in computational modeling) is inefficient to search through a non-linear parameter space that leads to emergence of neuronal rhythms. We used gSDR to train biophysical neural circuits and validated the algorithm on simple objectives. Then we applied gSDR to model observed neurophysiology. We asked the model to reproduce a shift from baseline oscillatory dynamics (~<20Hz) to stimulus induced gamma (~40-90Hz) dynamics recorded in the macaque visual cortex. This gamma oscillation during stimulation emerged by self-modulation of synaptic weights via gSDR. We further showed that the gamma-beta push-pull interactions implied by predictive routing could emerge via stochastic modulation of the local circuitry as well as top-down modulatory inputs to a network. To summarize, gSDR succeeded in training biophysical neural circuits to satisfy a series of neuronal objectives. This revealed the inhibitory neuron mechanisms underlying the gamma-beta push-pull dynamics that are observed during predictive processing tasks in systems and cognitive neuroscience.

Early auditory impairments as a candidate marker of attenuated sensory symptoms of psychosis

BACKGROUND AND HYPOTHESIS

Deficits in early auditory processing (EAP), as indexed by tone-matching performance, have been consistently demonstrated in individuals with schizophrenia spectrum disorders. However, the ontogeny of tone-matching deficits in schizophrenia remains relatively unknown. The current study aims to determine the relationship between clinical high risk for psychosis and EAP.

STUDY DESIGN

We employed a web-based screening approach to identify CHR individuals. A sample of 892 community dwelling participants completed the 16-tem version of the prodromal questionnaire (PQ16) for the assessment of attenuated psychotic symptoms, a 9-item questionnaire of perceptual and cognitive aberrations (PCA) for the assessment of basic symptoms and a tone-matching task.

STUDY RESULTS

505 (43.4 %) participants met cut-off criteria for attenuated psychotic symptoms (PQ16 ≥ 6 endorsed items), 614 (68.3 %) for basic symptoms (PCA ≥ 3 endorsed items), 647 (72.0 %) for either and 358 (40.1 %) for both of them. No significant differences in tone-matching performance were observed between CHR and non-CHR subjects, using either attenuated psychotic symptoms, basic symptoms, either or both cutoffs. In the CHR group screened with attenuated psychotic symptoms, auditory and tactile sensory symptoms were significantly associated with tone-matching deficits.

CONCLUSION

Tone-matching may not serve as a reliable biomarker for CHR status but rather a risk marker for the emergence of early sensory manifestations.

Different abnormalities of mismatch negativity in schizophrenia and depression as assessed with magnetoencephalography

Mismatch negativity (MMN) is widely considered a candidate diagnostic biomarker for schizophrenia (SCZ). Although blunted MMN responses have been reliably observed in psychosis, the evidence for MMN deficits in other disorders, such as major depressive disorder (MDD), is mixed. This study explores whether MMN alterations in amplitude or latency are unique to SCZ or extend to non-psychotic MDD patients. Seventeen patients diagnosed with a first MDD episode, 18 with recurrent MDD, 17 with first episode of SCZ spectrum disorder, and 18 with chronic SCZ, along with two groups of age- and sex-matched neurotypical controls (NC, 17 and 18), participated in a passive auditory MMN task during magnetoencephalography (MEG) recording. We examined the magnetic MMN (mMMN) amplitude and latency, exploring potential links between observed MMN alterations and psychotropic medication treatments. The mMMN amplitudes were significantly attenuated in SCZ compared to NC. Although, on average, mMMN amplitudes also appeared to be small in MDD, there was no significant difference between MDD and SCZ or NC. Notably, MDD patients had longer mMMN latencies compared to SCZ and NC, especially those with recurrent MDD. These results remained consistent after controlling for mood stabilizers, antidepressants, or benzodiazepines. These findings show that mMMN amplitude reductions may be more pronounced in psychotic disorders than in depressive disorders, whereas abnormal mMMN latencies may be more specific to MDD, suggesting differential mMMN alterations in SCZ and MDD. Caution is advised regarding mMMN amplitude as a diagnostic biomarker for SCZ, as small reductions also occur in MDD.

Examining the Complex Mismatch Negativity in Early Phase Psychosis Using the Dual Rule Paradigm

Using electroencephalography (EEG) to examine the simple mismatch negativity (MMN), a marker of auditory cortex function, has been of great interest in the exploration of biomarkers for psychotic illness. Despite many studies reporting MMN deficits in chronic schizophrenia, there are inconsistent reports of MMN reductions in the early phases of psychotic illness, suggesting the MMN elicited by traditional paradigms may not be a sensitive enough measure of vulnerability to be used as a biomarker. Recently, a more computationally complex measure of auditory cortex function (the complex mismatch negativity; cMMN) has been hypothesized to provide a more sensitive marker of illness vulnerability. The current study employed a novel dual rule paradigm, in which two pattern rules are established and violated, to examine the cMMN in 14 individuals with early phase psychosis (EPP, < 5 years illness) and 15 healthy controls (HC). Relationships between cMMN waveforms, symptom severity, and measures of functioning were explored. We found reductions of cMMN amplitudes at the site of maximal amplitude in EPP (p = .017) with large effect sizes (Hedges' g = 0.96). This study is an early step in the exploration of the cMMN as a biomarker for psychosis. Our results provide evidence that the dual rule cMMN paradigm shows promise as a method for cMMN elicitation that captures more subtle neurofunctional changes in the early stages of illness.

Mismatch Negativity as an Index of Auditory Short-Term Plasticity: Associations with Cortisol, Inflammation, and Gray Matter Volume in Youth at Clinical High Risk for Psychosis

Mismatch negativity (MMN) event-related potential (ERP) component reduction, indexing N-methyl-D-aspartate receptor (NMDAR)-dependent auditory echoic memory and short-term plasticity, is a well-established biomarker of schizophrenia that is sensitive to psychosis risk among individuals at clinical high-risk (CHR-P). Based on the NMDAR-hypofunction model of schizophrenia, NMDAR-dependent plasticity is predicted to contribute to aberrant neurodevelopmental processes involved in the pathogenesis of schizophrenia during late adolescence or young adulthood, including gray matter loss. Moreover, stress and inflammation disrupt plasticity. Therefore, using data collected during the 8-center North American Prodrome Longitudinal Study (NAPLS-2), we explored relationships between MMN amplitudes and salivary cortisol, gray matter volumes, and inflammatory cytokines. Participants included 303 CHR-P individuals with baseline electroencephalography (EEG) data recorded during an MMN paradigm as well as structural magnetic resonance imaging (MRI) and salivary cortisol, of which a subsample (n = 57) also completed blood draws. More deficient MMN amplitudes were associated with greater salivary cortisol and pro-inflammatory cytokine levels in future CHR-Converters, but not among those who did not convert to psychosis within the next two years. More deficient MMN amplitude was also associated with smaller total gray matter volume across participants regardless of future clinical outcomes, and with subcortical gray matter volumes among future CHR-Converters only. These findings are consistent with the theory that deficient NMDAR-dependent plasticity results in an overabundance of weak synapses that are subject to over-pruning during psychosis onset, contributing to gray matter loss. Further, MMN plasticity mechanisms may interact with stress, cortisol, and neuroinflammatory processes, representing a proximal influence of psychosis.

Development of Biomarkers Potentially Sensitive to Early Psychosis Using Mismatch Negativity (MMN) to Complex Pattern Deviations

Infrequent stimulus deviations from repetitive sequences elicit mismatch negativity (MMN) even passively, making MMN practical for clinical applications. Auditory MMN is typically elicited by a change in one (or more) physical stimulus parameters (eg, pitch, duration). This lower-order simple MMN (sMMN) is impaired in long-term schizophrenia. However, sMMN contains activity from release from stimulus adaptation, clouding its face validity as purely deviance-related. More importantly, it is unreliably reduced in samples of first-episode psychosis, limiting its utility as a biomarker. Complex pattern-deviant MMN (cMMN) tasks, which elicit early and late responses, are based on higher-order abstractions and better isolate deviance detection. Their abstract nature may increase the sensitivity to processing deficits in early psychosis. However, both the early and late cMMNs are small, limiting separation between healthy and psychotic samples. In 29 healthy individuals, we tested a new dual-rule cMMN paradigm to assess additivity of deviance. Sounds alternated lateralization between left and right, and low and high pitches, creating a left-low, right-high alternating pattern. Deviants were a repeated left-low, violating lateralization and pitch patterns. Early and late cMMNs on the dual-rule task were significantly larger than those on the one-rule extra tone cMMN task (P < .05). Further, the dual-rule early cMMN was not significantly smaller than pitch or duration sMMNs (P > .48, .28, respectively). These results demonstrate additivity for cMMN pattern-violating rules. This increase in cMMN amplitude should increase group difference effect size, making it a prime candidate for a biomarker of disease presence at first psychotic episode, and perhaps even prior to the emergence of psychosis.

Bringing Imaging Biomarkers Into Clinical Reality in Psychiatry

Importance

Advancing precision psychiatry, where treatments are based on an individual's biology rather than solely their clinical presentation, requires attention to several key attributes for any candidate biomarker. These include test-retest reliability, sensitivity to relevant neurophysiology, cost-effectiveness, and scalability. Unfortunately, these issues have not been systematically addressed by biomarker development efforts that use common neuroimaging tools like magnetic resonance imaging (MRI) and electroencephalography (EEG). Here, the critical barriers that neuroimaging methods will need to overcome to achieve clinical relevance in the near to intermediate term are examined.

Observations

Reliability is often overlooked, which together with sensitivity to key aspects of neurophysiology and replicated predictive utility, favors EEG-based methods. The principal barrier for EEG has been the lack of large-scale data collection among multisite psychiatric consortia. By contrast, despite its high reliability, structural MRI has not demonstrated clinical utility in psychiatry, which may be due to its limited sensitivity to psychiatry-relevant neurophysiology. Given the prevalence of structural MRIs, establishment of a compelling clinical use case remains its principal barrier. By contrast, low reliability and difficulty in standardizing collection are the principal barriers for functional MRI, along with the need for demonstration that its superior spatial resolution over EEG and ability to directly image subcortical regions in fact provide unique clinical value. Often missing, moreover, is consideration of how these various scientific issues can be balanced against practical economic realities of psychiatric health care delivery today, for which embedding economic modeling into biomarker development efforts may help direct research efforts.

Conclusions and Relevance

EEG seems most ripe for near- to intermediate-term clinical impact, especially considering its scalability and cost-effectiveness. Recent efforts to broaden its collection, as well as development of low-cost turnkey systems, suggest a promising pathway by which neuroimaging can impact clinical care. Continued MRI research focused on its key barriers may hold promise for longer-horizon utility.

Opportunities for use of neuroimaging in de-risking drug development and improving clinical outcomes in psychiatry: an industry perspective

Neuroimaging, across positron emission tomography (PET), electroencephalography (EEG), and magnetic resonance imaging (MRI), has been a mainstay of clinical neuroscience research for decades, yet has penetrated little into psychiatric drug development beyond often underpowered phase 1 studies, or into clinical care. Simultaneously, there is a pressing need to improve the probability of success in drug development, increase mechanistic diversity, and enhance clinical efficacy. These goals can be achieved by leveraging neuroimaging in a precision psychiatry framework, wherein effects of drugs on the brain are measured early in clinical development to understand dosing and indication, and then in later-stage trials to identify likely drug responders and enrich clinical trials, ultimately improving clinical outcomes. Here we examine the key variables important for success in using neuroimaging for precision psychiatry from the lens of biotechnology and pharmaceutical companies developing and deploying new drugs in psychiatry. We argue that there are clear paths for incorporating different neuroimaging modalities to de-risk subsequent development phases in the near to intermediate term, culminating in use of select neuroimaging modalities in clinical care for prescription of new precision drugs. Better outcomes through neuroimaging biomarkers, however, require a wholesale commitment to a precision psychiatry approach and will necessitate a cultural shift to align biopharma and clinical care in psychiatry to a precision orientation already routine in other areas of medicine.

Abnormal inter-hemispheric effective connectivity from left to right auditory regions during Mismatch Negativity (MMN) tasks in psychosis

Anomalous Mismatch Negativity (MMN) in psychosis could be a consequence of disturbed neural oscillatory activity at sensory/perceptual stages of stimulus processing. This study investigated effective connectivity within and between the auditory regions during auditory odd-ball deviance tasks. The analyses were performed on two magnetoencephalography (MEG) datasets: one on duration MMN in a cohort with various diagnoses within the psychosis spectrum and neurotypical controls, and one on duration and pitch MMN in first-episode psychosis patients and matched neurotypical controls. We applied spectral Granger causality to MEG source-reconstructed signals to compute effective connectivity within and between the left and right auditory regions. Both experiments showed that duration-deviance detection was associated with early increases of effective connectivity in the beta band followed by increases in the alpha and theta bands, with the connectivity strength linked to the laterality of the MMN amplitude. Compared to controls, people with psychosis had overall smaller effective connectivity, particularly from left to right auditory regions, in the pathway where bilateral information converges toward lateralized processing, often rightward. Blunted MMN in psychosis might reflect a deficit in inter-hemispheric communication between auditory regions, highlighting a "dysconnection" already at preattentive stages of stimulus processing as a model system of widespread pathophysiology.

Antipsychotic Treatment in People at Clinical High Risk for Psychosis: A Narrative Review of Suggestions for Clinical Practice

PURPOSE

The "early intervention" paradigm in psychiatry holds significant promise for preventing psychosis. Recent evidence showed that individuals at clinical high risk for psychosis (CHR-P) with antipsychotic (AP) prescription at baseline have higher psychosis transition rates compared with those without AP, although the underlying cause remains unclear. In this article, we reviewed international guidelines on early intervention in CHR-P people, paying specific attention to clinical recommendations on AP treatment. Then, we comment on these suggestions in the light of recent empirical evidence examining AP prescription in CHR-P populations within "real-world" clinical settings.

METHODS

This search was conducted on PubMed/MEDLINE, PsycINFO, EMBASE, and Google, looking for both "Guidelines AND CHR-P OR UHR OR Early Psychosis."

RESULTS

International guidelines generally recommend not using AP as first-line treatment, but only when psychosocial interventions have failed. CHR-P people with AP drug showed high prevalence rates and had more severe clinical picture at entry. Is this a "warning signal" for potentially higher psychosis transition risk? Is it a direct AP iatrogenic effect? Is it possible to detect specific CHR-P subgroup that may benefit from AP? These are the questions that this article seeks to explore.

CONCLUSIONS

The current framework for identifying CHR-P subjects has defined psychometric criteria mainly based on positive symptoms. In our opinion, this is reductive, especially for evaluating therapeutic outcomes and prognosis. A more comprehensive assessment considering quality of life, psychiatric comorbidity, persistent negative symptoms, subjective experience of CHR-P psychopathology, and social/personal recovery is thus needed.

Identify Potential Causal Relationships Between Cortical Thickness, Mismatch Negativity, Neurocognition, and Psychosocial Functioning in Drug-Naïve First-Episode Psychosis Patients

BACKGROUND

Cortical thickness (CT) alterations, mismatch negativity (MMN) reductions, and cognitive deficits are robust findings in first-episode psychosis (FEP). However, most studies focused on medicated patients, leaving gaps in our understanding of the interrelationships between CT, MMN, neurocognition, and psychosocial functioning in unmedicated FEP. This study aimed to employ multiple mediation analysis to investigate potential pathways among these variables in unmedicated drug-naïve FEP.

METHODS

We enrolled 28 drug-naïve FEP and 34 age and sex-matched healthy controls. Clinical symptoms, neurocognition, psychosocial functioning, auditory duration MMN, and T1 structural magnetic resonance imaging data were collected. We measured CT in the superior temporal gyrus (STG), a primary MMN-generating region.

RESULTS

We found a significant negative correlation between MMN amplitude and bilateral CT of STG (CT_STG) in FEP (left: r = -.709, P < .001; right: r = -.612, P = .008). Multiple mediation models revealed that a thinner left STG cortex affected functioning through both direct (24.66%) and indirect effects (75.34%). In contrast, the effects of the right CT_STG on functioning were mainly mediated through MMN and neurocognitive pathways.

CONCLUSIONS

Bilateral CT_STG showed significant association with MMN, and MMN plays a mediating role between CT and cognition. Both MMN alone and its interaction with cognition mediated the effects of structural alterations on psychosocial function. The decline in overall function in FEP may stem from decreased CT_STG, leading to subsequent MMN deficits and neurocognitive dysfunction. These findings underline the crucial role of MMN in elucidating how subtle structural alterations can impact neurocognition and psychosocial function in FEP.

An EEG-Based Neuroplastic Approach to Predictive Coding in People With Schizophrenia or Traumatic Brain Injury

Despite different etiologies, people with schizophrenia (SCZ) or with traumatic brain injury (TBI) both show aberrant neuroplasticity. One neuroplastic mechanism that may be affected is prediction error coding. We used a roving mismatch negativity (rMMN) paradigm which uses different lengths of standard tone trains and is optimized to assess predictive coding. Twenty-five SCZ, 22 TBI (mild to moderate), and 25 healthy controls were assessed. We used a frequency-deviant rMMN in which the number of standards preceding the deviant was either 2, 6, or 36. We evaluated repetition positivity to the standard tone immediately preceding a deviant tone (repetition positivity [RP], to assess formation of the memory trace), deviant negativity to the deviant stimulus (deviant negativity [DN], which reflects signaling of a prediction error), and the difference wave between the 2 (the MMN). We found that SCZ showed reduced DN and MMN compared with healthy controls and with people with mild to moderate TBI. We did not detect impairments in any index (RP, DN, or MMN) in people with TBI compared to controls. Our findings suggest that prediction error coding assessed with rMMN is aberrant in SCZ but intact in TBI, though there is a suggestion that severity of head injury results in poorer prediction error coding.

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.

Accelerating Medicines Partnership® Schizophrenia (AMP® SCZ): Rationale and Study Design of the Largest Global Prospective Cohort Study of Clinical High Risk for Psychosis

This article describes the rationale, aims, and methodology of the Accelerating Medicines Partnership® Schizophrenia (AMP® SCZ). This is the largest international collaboration to date that will develop algorithms to predict trajectories and outcomes of individuals at clinical high risk (CHR) for psychosis and to advance the development and use of novel pharmacological interventions for CHR individuals. We present a description of the participating research networks and the data processing analysis and coordination center, their processes for data harmonization across 43 sites from 13 participating countries (recruitment across North America, Australia, Europe, Asia, and South America), data flow and quality assessment processes, data analyses, and the transfer of data to the National Institute of Mental Health (NIMH) Data Archive (NDA) for use by the research community. In an expected sample of approximately 2000 CHR individuals and 640 matched healthy controls, AMP SCZ will collect clinical, environmental, and cognitive data along with multimodal biomarkers, including neuroimaging, electrophysiology, fluid biospecimens, speech and facial expression samples, novel measures derived from digital health technologies including smartphone-based daily surveys, and passive sensing as well as actigraphy. The study will investigate a range of clinical outcomes over a 2-year period, including transition to psychosis, remission or persistence of CHR status, attenuated positive symptoms, persistent negative symptoms, mood and anxiety symptoms, and psychosocial functioning. The global reach of AMP SCZ and its harmonized innovative methods promise to catalyze the development of new treatments to address critical unmet clinical and public health needs in CHR individuals.

Neuroimaging and Biosample Collection in the Toronto Adolescent and Youth Cohort Study: Rationale, Methods, and Early Data

BACKGROUND

The Toronto Adolescent and Youth (TAY) Cohort Study will characterize the neurobiological trajectories of psychosis spectrum symptoms, functioning, and suicidality (i.e., suicidal thoughts and behaviors) in youth seeking mental health care. Here, we present the neuroimaging and biosample component of the protocol. We also present feasibility and quality control metrics for the baseline sample collected thus far.

METHODS

The current study includes youths (ages 11-24 years) who were referred to child and youth mental health services within a large tertiary care center in Toronto, Ontario, Canada, with target recruitment of 1500 participants. Participants were offered the opportunity to provide any or all of the following: 1) 1-hour magnetic resonance imaging (MRI) scan (electroencephalography if ineligible for or declined MRI), 2) blood sample for genomic and proteomic data (or saliva if blood collection was declined or not feasible) and urine sample, and 3) heart rate recording to assess respiratory sinus arrhythmia.

RESULTS

Of the first 417 participants who consented to participate between May 4, 2021, and February 2, 2023, 412 agreed to participate in the imaging and biosample protocol. Of these, 334 completed imaging, 341 provided a biosample, 338 completed respiratory sinus arrhythmia, and 316 completed all 3. Following quality control, data usability was high (MRI: T1-weighted 99%, diffusion-weighted imaging 99%, arterial spin labeling 90%, resting-state functional MRI 95%, task functional MRI 90%; electroencephalography: 83%; respiratory sinus arrhythmia: 99%).

CONCLUSIONS

The high consent rates, good completion rates, and high data usability reported here demonstrate the feasibility of collecting and using brain imaging and biosamples in a large clinical cohort of youths seeking mental health care.

Children at Familial High risk of Schizophrenia and Bipolar Disorder Exhibit Altered Connectivity Patterns During Pre-attentive Processing of an Auditory Prediction Error

BACKGROUND AND HYPOTHESIS

Individuals with schizophrenia or bipolar disorder have attenuated auditory mismatch negativity (MMN) responses, indicating impaired sensory information processing. Computational models of effective connectivity between brain areas underlying MMN responses show reduced connectivity between fronto-temporal areas in individuals with schizophrenia. Here we ask whether children at familial high risk (FHR) of developing a serious mental disorder show similar alterations.

STUDY DESIGN

We recruited 67 children at FHR for schizophrenia, 47 children at FHR for bipolar disorder as well as 59 matched population-based controls from the Danish High Risk and Resilience study. The 11-12-year-old participants engaged in a classical auditory MMN paradigm with deviations in frequency, duration, or frequency and duration, while we recorded their EEG. We used dynamic causal modeling (DCM) to infer on the effective connectivity between brain areas underlying MMN.

STUDY RESULTS

DCM yielded strong evidence for differences in effective connectivity among groups in connections from right inferior frontal gyrus (IFG) to right superior temporal gyrus (STG), along with differences in intrinsic connectivity within primary auditory cortex (A1). Critically, the 2 high-risk groups differed in intrinsic connectivity in left STG and IFG as well as effective connectivity from right A1 to right STG. Results persisted even when controlling for past or present psychiatric diagnoses.

CONCLUSIONS

We provide novel evidence that connectivity underlying MMN responses in children at FHR for schizophrenia and bipolar disorder is altered at the age of 11-12, echoing findings that have been found in individuals with manifest schizophrenia.

Neural Circuitry-Related Biomarkers for Drug Development in Psychiatry: An Industry Perspective

Drug development in psychiatry has been hampered by the lack of reliable ways to determine the neurobiological effects of the assets tested, difficulties in identifying patient subsets more amenable to benefit from a given asset, and issues with executing trials in a manner that would convincingly provide answers. An emerging idea in many companies is to validate tools to address changes in neural circuits by pharmacological tools as a key piece in quantifying the effects of our drugs. Here, we review past, present, and emerging approaches to capture the outcome of the modulation of brain circuits. The field is now ripe for implementing these approaches in drug development.

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.

Intact Mismatch Negativity Responses in Clinical High Risk for Psychosis and First-Episode Psychosis: Evidence From Source-Reconstructed Event-Related Fields and Time-Frequency Data

BACKGROUND

This study examined whether mismatch negativity (MMN) responses are impaired in participants at clinical high risk for psychosis (CHR-P) and patients with first-episode psychosis (FEP) and whether MMN deficits predict clinical outcomes in CHR-Ps.

METHODS

Magnetoencephalography data were collected during a duration-deviant MMN paradigm for a group of 116 CHR-P participants, 33 FEP patients (15 antipsychotic-naïve), clinical high risk negative group (n = 38) with substance abuse and affective disorder, and 49 healthy control participants. Analysis of group differences of source-reconstructed event-related fields as well as time-frequency and intertrial phase coherence focused on the bilateral Heschl's gyri and bilateral superior temporal gyri.

RESULTS

Significant magnetic MMN responses were found across participants in the bilateral Heschl's gyri and bilateral superior temporal gyri. However, MMN amplitude as well as time-frequency and intertrial phase coherence responses were intact in CHR-P participants and FEP patients compared with healthy control participants. Furthermore, MMN deficits were not related to persistent attenuated psychotic symptoms or transitions to psychosis in CHR-P participants.

CONCLUSIONS

Our data suggest that magnetic MMN responses in magnetoencephalography data are not impaired in early-stage psychosis and may not predict clinical outcomes in CHR-P participants.

Kenya Psychosis-Risk Outcomes Study (KePROS): Development of an Accelerated Medicine Partnership Schizophrenia-Aligned Project in Africa

Background and Hypothesis

The Accelerating Medicines Partnership Schizophrenia (AMP SCZ) funds a longitudinal study of 43 research sites across 5 continents to develop tools to stratify developmental trajectories of youth at clinical high risk for psychosis (CHR) and identify homogenous targets for future clinical trials. However, there are no sites in Africa, leaving a critical gap in our knowledge of clinical and biological outcomes among CHR individuals.

Study Design

We describe the development of the Kenya Psychosis-Risk Outcomes Study (KePROS), a 5-year NIH-funded project in Kenya designed to harmonize with AMP SCZ. The study will recruit over 100 CHR and 50 healthy participants and conduct multiple clinical and biomarker assessments over 2 years. Capacity building is a key component of the study, including the construction of an electroencephalography (EEG) laboratory and the upgrading of a local 3 T magnetic resonance imaging (MRI) machine. We detail community recruitment, study methodologies and protocols, and unique challenges with this pioneering research in Africa.

Study Results

This paper is descriptive only. Planned future analyses will investigate possible predictors of clinical outcomes and will be compared to results from other global populations.

Conclusions

KePROS will provide the research community with a rich longitudinal clinical and biomarker dataset from an African country in the developing Global South, which can be used alongside AMP SCZ data to delineate CHR outcome groups for future treatment development. Training in mental health assessment and investment in cutting-edge biomarker assessment and other technologies is needed to facilitate the inclusion of African countries in large-scale research consortia.

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.

Mismatch negativity in schizophrenia spectrum and bipolar disorders: Group and sex differences and associations with symptom severity

OBJECTIVE

Research increasingly implicates glutamatergic dysfunction in the pathophysiologies of psychotic disorders. Auditory mismatch negativity (MMN) is an electroencephalography (EEG) waveform linked to glutamatergic neurotransmission and is consistently attenuated in schizophrenia (SCZ). MMN consists of two subcomponents, the repetition positivity (RP) and deviant negativity (DN) possibly reflecting different neural mechanisms. However, whether MMN reduction is present across different psychotic disorders, linked to distinct symptom clusters, or related to sex remain to be clarified.

METHODS

Four hundred participants including healthy controls (HCs; n = 296) and individuals with SCZ (n = 39), bipolar disorder (BD) BD typeI (n = 35), or BD type II (n = 30) underwent a roving MMN paradigm and clinical evaluation. MMN, RP and DN as well their memory traces were recorded at the FCZ electrode. Analyses of variance and linear regression models were used both transdiagnostically and within clinical groups.

RESULTS

MMN was reduced in SCZ compared to BD (p = 0.006, d = 0.55) and to HCs (p < 0.001, d = 0.63). There was a significant group × sex interaction (p < 0.003) and the MMN impairment was only detected in males with SCZ. MMN amplitude correlated positively with Positive and Negative Syndrome Scale total score and negatively with Global Assessment of Functioning Scale score. The deviant negativity was impaired in males with SCZ. No group differences in memory trace indices of the MMN, DN, or RP.

CONCLUSION

MMN was attenuated in SCZ and correlated with greater severity of psychotic symptoms and lower level of functioning. Our results may indicate sex-dependent differences of glutamatergic function in SCZ.

Recent Updates on Predicting Conversion in Youth at Clinical High Risk for Psychosis

PURPOSE OF REVIEW

This review highlights recent advances in the prediction and treatment of psychotic conversion. Over the past 25 years, research into the prodromal phase of psychotic illness has expanded with the promise of early identification of individuals at clinical high risk (CHR) for psychosis who are likely to convert to psychosis.

RECENT FINDINGS

Meta-analyses highlight conversion rates between 20 and 30% within 2-3 years using existing clinical criteria while research into more specific risk factors, biomarkers, and refinement of psychosis risk calculators has exploded, improving our ability to predict psychotic conversion with greater accuracy. Recent studies highlight risk factors and biomarkers likely to contribute to earlier identification and provide insight into neurodevelopmental abnormalities, CHR subtypes, and interventions that can target specific risk profiles linked to neural mechanisms. Ongoing initiatives that assess longer-term (> 5-10 years) outcome of CHR participants can provide valuable information about predictors of later conversion and diagnostic outcomes while large-scale international biomarker studies provide hope for precision intervention that will alter the course of early psychosis globally.

Reduced magnetic mismatch negativity: a shared deficit in psychosis and related risk

BACKGROUND

Abnormal auditory processing of deviant stimuli, as reflected by mismatch negativity (MMN), is often reported in schizophrenia (SCZ). At present, it is still under debate whether this dysfunctional response is specific to the full-blown SCZ diagnosis or rather a marker of psychosis in general. The present study tested MMN in patients with SCZ, bipolar disorder (BD), first episode of psychosis (FEP), and in people at clinical high risk for psychosis (CHR).

METHODS

Source-based MEG activity evoked during a passive auditory oddball task was recorded from 135 patients grouped according to diagnosis (SCZ, BD, FEP, and CHR) and 135 healthy controls also divided into four subgroups, age- and gender-matched with diagnostic subgroups. The magnetic MMN (mMMN) was analyzed as event-related field (ERF), Theta power, and Theta inter-trial phase coherence (ITPC).

RESULTS

The clinical group as a whole showed reduced mMMN ERF amplitude, Theta power, and Theta ITPC, without any statistically significant interaction between diagnosis and mMMN reductions. The mMMN subgroup contrasts showed lower ERF amplitude in all the diagnostic subgroups. In the analysis of Theta frequency, SCZ showed significant power and ITPC reductions, while only indications of diminished ITPC were observed in CHR, but no significant decreases characterized BD and FEP.

CONCLUSIONS

Significant mMMN alterations in people experiencing psychosis, also for diagnoses other than SCZ, suggest that this neurophysiological response may be a feature shared across psychotic disorders. Additionally, reduced Theta ITPC may be associated with risk for psychosis.

Why mismatch negativity continues to hold potential in probing altered brain function in schizophrenia

The brain potential known as mismatch negativity (MMN) is one of the most studied indices of altered brain function in schizophrenia. This review looks at what has been learned about MMN in schizophrenia over the last three decades and why the level of interest and activity in this field of research remains strong. A diligent consideration of available evidence suggests that MMN can serve as a biomarker in schizophrenia, but perhaps not the kind of biomarker that early research supposed. This review concludes that MMN measurement is likely to be most useful as a monitoring and response biomarker enabling tracking of an underlying pathology and efficacy of interventions, respectively. The role of, and challenges presented by, pre-clinical models is discussed as well as the merits of different methodologies that can be brought to bear in pursuing a deeper understanding of pathophysiology that might explain smaller MMN in schizophrenia.

Changes in patterns of age-related network connectivity are associated with risk for schizophrenia

Alterations in fMRI-based brain functional network connectivity (FNC) are associated with schizophrenia (SCZ) and the genetic risk or subthreshold clinical symptoms preceding the onset of SCZ, which often occurs in early adulthood. Thus, age-sensitive FNC changes may be relevant to SCZ risk-related FNC. We used independent component analysis to estimate FNC from childhood to adulthood in 9,236 individuals. To capture individual brain features more accurately than single-session fMRI, we studied an average of three fMRI scans per individual. To identify potential familial risk-related FNC changes, we compared age-related FNC in first-degree relatives of SCZ patients mostly including unaffected siblings (SIB) with neurotypical controls (NC) at the same age stage. Then, we examined how polygenic risk scores for SCZ influenced risk-related FNC patterns. Finally, we investigated the same risk-related FNC patterns in adult SCZ patients (oSCZ) and young individuals with subclinical psychotic symptoms (PSY). Age-sensitive risk-related FNC patterns emerge during adolescence and early adulthood, but not before. Young SIB always followed older NC patterns, with decreased FNC in a cerebellar-occipitoparietal circuit and increased FNC in two prefrontal-sensorimotor circuits when compared to young NC. Two of these FNC alterations were also found in oSCZ, with one exhibiting reversed pattern. All were linked to polygenic risk for SCZ in unrelated individuals (R2 varied from 0.02 to 0.05). Young PSY showed FNC alterations in the same direction as SIB when compared to NC. These results suggest that age-related neurotypical FNC correlates with genetic risk for SCZ and is detectable with MRI in young participants.

Mismatch negativity generation in subjects at risk for psychosis: source analysis is more sensitive than surface electrodes in risk prediction

Background

Deficits of mismatch negativity (MMN) in patients with schizophrenia have been demonstrated many times and there is growing evidence that alterations of MMN already exist in individuals at risk for psychosis. The present study examines differences in MMN between subjects fulfilling ultra-high risk (UHR) or only basic symptoms criteria and it addresses the question, if MMN source analysis can improve prediction of transition to psychosis.

Methods

The MMN to duration, frequency, and intensity deviants was recorded in 50 healthy controls and 161 individuals at risk for psychosis classified into three subgroups: only basic symptoms (n = 74), only ultra-high risk (n = 13) and persons who fulfill both risk criteria (n = 74). Based on a three-source model of MMN generation, we conducted an MMN source analysis and compared the amplitudes of surface electrodes and sources among the three groups.

Results

Significant differences in MMN generation among the four groups were revealed at surface electrodes Cz and C4 (p < 0.05) and at the frontal source (p < 0.001) for duration deviant stimuli. The 15 subjects from the risk groups who subsequently developed a manifest psychosis had a significantly lower MMN amplitude at frontal source (p = 0.019) without showing significant differences at surface electrodes. Low activity at frontal MMN source increased the risk of transition to manifest disease by the factor 3.12 in UHR subjects.

Conclusion

MMN activity differed significantly between subjects presenting only basic symptoms and subjects which additionally meet UHR criteria. The largest differences between groups as well as between individuals with and without transition were observed at the frontal source. The present results suggest that source analysis is more sensitive than surface electrodes in psychosis risk prediction by MMN.

Early auditory processing dysfunction in schizophrenia: Mechanisms and implications

Schizophrenia is a major mental disorder that affects approximately 1% of the population worldwide. Cognitive deficits are a key feature of the disorder and a primary cause of long-term disability. Over the past decades, significant literature has accumulated demonstrating impairments in early auditory perceptual processes in schizophrenia. In this review, we first describe early auditory dysfunction in schizophrenia from both a behavioral and neurophysiological perspective and examine their interrelationship with both higher order cognitive constructs and social cognitive processes. Then, we provide insights into underlying pathological processes, especially in relationship to glutamatergic and N-methyl-D-aspartate receptor (NMDAR) dysfunction models. Finally, we discuss the utility of early auditory measures as both treatment targets for precision intervention and as translational biomarkers for etiological investigation. Altogether, this review points out the crucial role of early auditory deficits in the pathophysiology of schizophrenia, in addition to major implications for early intervention and auditory-targeted approaches.

Musicians show more integrated neural processing of contextually relevant acoustic features

Little is known about expertise-related plasticity of neural mechanisms for auditory feature integration. Here, we contrast two diverging hypotheses that musical expertise is associated with more independent or more integrated predictive processing of acoustic features relevant to melody perception. Mismatch negativity (MMNm) was recorded with magnetoencephalography (MEG) from 25 musicians and 25 non-musicians, exposed to interleaved blocks of a complex, melody-like multi-feature paradigm and a simple, oddball control paradigm. In addition to single deviants differing in frequency (F), intensity (I), or perceived location (L), double and triple deviants were included reflecting all possible feature combinations (FI, IL, LF, FIL). Following previous work, early neural processing overlap was approximated in terms of MMNm additivity by comparing empirical MMNms obtained with double and triple deviants to modeled MMNms corresponding to summed constituent single-deviant MMNms. Significantly greater subadditivity was found in musicians compared to non-musicians, specifically for frequency-related deviants in complex, melody-like stimuli. Despite using identical sounds, expertise effects were absent from the simple oddball paradigm. This novel finding supports the integrated processing hypothesis whereby musicians recruit overlapping neural resources facilitating more integrative representations of contextually relevant stimuli such as frequency (perceived as pitch) during melody perception. More generally, these specialized refinements in predictive processing may enable experts to optimally capitalize upon complex, domain-relevant, acoustic cues.