Mismatch negativity as a "translatable" brain marker toward early intervention for psychosis: a review

Mismatch negativity in common marmosets: Whole-cortical recordings with multi-channel electrocorticograms

Mismatch negativity (MMN) is a component of event-related potentials (ERPs) evoked by violations of regularity in sensory stimulus-series in humans. Recently, the MMN has received attention as a clinical and translatable biomarker of psychiatric disorders such as schizophrenia, and for the development animal models of these psychiatric disorders. In this study, we investigated the generation of MMN in common marmosets, which are an important non-human primate model with genetic manipulability. We recorded the electrocorticograms (ECoGs) from two common marmosets with epidurally implanted electrodes covering a wide range of cortical regions. ECoG recordings were conducted in a passive listening condition with a roving oddball paradigm. We compared the ERPs evoked by repeatedly presented standard stimuli and those evoked by the deviant stimuli. Significant differences in the ERPs were observed in several cortical areas. In particular, deviant stimuli elicited larger negative activity than standard stimuli in the temporal area. In addition, the latency and polarity of the activity were comparable to human MMNs. This is thus the first report of MMN-like activity in common marmosets. Our findings have the potential to advance future gene-manipulation studies that aim to establish non-human primate models of schizophrenia.

Diametrical diseases reflect evolutionary-genetic tradeoffs: Evidence from psychiatry, neurology, rheumatology, oncology and immunology

Tradeoffs centrally mediate the expression of human adaptations. We propose that tradeoffs also influence the prevalence and forms of human maladaptation manifest in disease. By this logic, increased risk for one set of diseases commonly engenders decreased risk for another, diametric, set of diseases. We describe evidence for such diametric sets of diseases from epidemiological, genetic and molecular studies in four clinical domains: (i) psychiatry (autism vs psychotic-affective conditions), (ii) rheumatology (osteoarthritis vs osteoporosis), (iii) oncology and neurology (cancer vs neurodegenerative disorders) and (iv) immunology (autoimmunity vs infectious disease). Diametric disorders are important to recognize because genotypes or environmental factors that increase risk for one set of disorders protect from opposite disorders, thereby providing novel and direct insights into disease causes, prevention and therapy. Ascertaining the mechanisms that underlie disease-related tradeoffs should also indicate means of circumventing or alleviating them, and thus reducing the incidence and impacts of human disease in a more general way.

Is it time to move mismatch negativity into the clinic?

Since its inception in the 1970s, the mismatch negativity (MMN) event-related potential has improved our understanding of pre-attentive detection of rule violations, which is a fundamental cognitive process considered by some a form of "primitive intelligence". The body of research to date ranges from animal studies (i.e. when investigating the neural mechanisms and pharmacological properties of MMN generation) to researching the psychophysiological nature of human consciousness. MMN therefore offers the possibility to detect abnormal functioning in the neural system involved in MMN generation, such as it occurs in some neurodevelopmental disorders or patients in vegetative state. While the clinical research data holds considerable promise for translation into clinical practice, standardization and normative data of an optimized (i.e. disorder-specific) MMN recording algorithm is needed in order for MMN to become a valuable clinical investigation tool.

Elementary sensory deficits in schizophrenia indexed by impaired visual mismatch negativity

INTRODUCTION

Mismatch negativity (MMN) is an automatic brain response to unexpected events. It represents a prediction error (PE) response, reflecting the difference between the sensory input and predictions. While deficits in auditory MMN are well known in schizophrenia, only few studies investigated impairments in predictive visual processing in schizophrenia. These studies used complex stimuli such as motion direction and emotional facial expressions. Here we studied whether automatic predictive processing of elementary features such as orientation is also impaired in schizophrenia.

METHODS

Altogether 28 patients with schizophrenia and 27 healthy controls matched in age, gender, and education participated in the study. EEG was recorded using 128 channels in the two experimental blocks. Using an oddball paradigm, horizontal stripes of Gabor patches were presented as frequent standards and vertical stripes as rare deviants in one block. Stimulus probabilities were swapped in the other block. Mismatch responses were obtained by subtracting responses to standard from those to deviant stimuli.

RESULTS

We found significant mismatch responses in healthy controls but not in patients in the prefrontal and occipital-parietal regions in the 90-200ms interval. Furthermore patients showed significantly decreased deviant minus standard difference waveforms relative to controls in the same regions with moderate to large effect sizes.

CONCLUSIONS

Our findings demonstrate that predictive processing of unattended low-level visual features such as orientation is impaired in schizophrenia. Our results complement reports of sensory deficits found in tasks requiring attentive processing and suggest that deficits are present in automatic visual sensory processes putatively mediated by glutamatergic functioning.

Forecasting psychosis by event-related potentials-systematic review and specific meta-analysis

BACKGROUND

Prediction and prevention of psychosis have become major research topics. Clinical approaches warrant objective biological parameters to enhance validity in prediction of psychosis onset. In this regard, event-related potentials (ERPs) have been identified as promising tools for improving psychosis prediction.

METHODS

Herein, the focus is on sensory gating, mismatch negativity (MMN) and P300, thereby discussing which parameters allow for a timely and valid detection of future converters to psychosis. In a first step, we systematically reviewed the studies that resulted from a search of the MEDLINE database. In a second step, we performed a meta-analysis of those investigations reporting transitions that statistically compared ERPs in converting versus nonconverting subjects.

RESULTS

Sensory gating, MMN, and P300 have been demonstrated to be impaired in subjects clinically at risk of developing a psychotic disorder. In the meta-analysis, duration MMN achieved the highest effect size measures.

CONCLUSIONS

In summary, MMN studies have produced the most convincing results until now, including independent replication of the predictive validity. However, a synopsis of the literature revealed a relative paucity of ERP studies addressing the psychosis risk state. Considering the high clinical relevance of valid psychosis prediction, future research should question for the most informative paradigms and should allow for meta-analytic evaluation with regard to specificity and sensitivity of the most appropriate parameters.

Disruption of information processing in schizophrenia: The time perspective

We review studies suggesting time disorders on both automatic and subjective levels in patients with schizophrenia. Patients have difficulty explicitly discriminating between simultaneous and asynchronous events, and ordering events in time. We discuss the relationship between these difficulties and impairments on a more elementary level. We showed that for undetectable stimulus onset asynchronies below 20 ms, neither patients nor controls merge events in time, as previously believed. On the contrary, subjects implicitly distinguish between events even when evaluating them to be simultaneous. Furthermore, controls privilege the last stimulus, whereas patients seem to stay stuck on the first stimulus when asynchronies are sub-threshold. Combining previous results shows this to be true for patients even for asynchronies as short as 8 ms. Moreover, this peculiarity predicts difficulties with detecting asynchronies longer than 50 ms, suggesting an impact on the conscious ability to time events. Difficulties on the subjective level are also correlated with clinical disorganization. The results are interpreted within the framework of predictive coding which can account for an implicit ability to update events. These results complement a range of other results, by suggesting a difficulty with binding information in time as well as space, and by showing that information processing lacks continuity and stability in patients. The time perspective may help bridge the gap between cognitive impairments and clinical symptoms, by showing how the innermost structure of thought and experience is disrupted.

Future clinical uses of neurophysiological biomarkers to predict and monitor treatment response for schizophrenia

Advances in psychiatric neuroscience have transformed our understanding of impaired and spared brain functions in psychotic illnesses. Despite substantial progress, few (if any) laboratory tests have graduated to clinics to inform diagnoses, guide treatments, and monitor treatment response. Providers must rely on careful behavioral observation and interview techniques to make inferences about patients' inner experiences and then secondary deductions about impacted neural systems. Development of more effective treatments has also been hindered by a lack of translational quantitative biomarkers that can span the brain-behavior treatment knowledge gap. Here, we describe an example of a simple, low-cost, and translatable electroencephalography (EEG) measure that offers promise for improving our understanding and treatment of psychotic illnesses: mismatch negativity (MMN). MMN is sensitive to and/or predicts response to some pharmacologic and nonpharmacologic interventions and accounts for substantial portions of variance in clinical, cognitive, and psychosocial functioning in schizophrenia (SZ). This measure has recently been validated for use in large-scale multisite clinical studies of SZ. Finally, MMN greatly improves our ability to forecast which individuals at high clinical risk actually develop a psychotic illness. These attributes suggest that MMN can contribute to personalized biomarker-guided treatment strategies aimed at ameliorating or even preventing the onset of psychosis.

Can age at sexual maturity act as a predictive biomarker for prodromal negative symptoms?

BACKGROUND

Puberty and reproductive hormones have been identified as having a potential role in schizophrenia. Earlier reports have suggested associations between later age at puberty and schizophrenia in males. Similarly, associations have been reported between testosterone levels and psychotic symptoms. In this report, we examined the association between age at puberty and prodromal symptoms of psychosis.

METHODS

58 child or adolescent family members of individuals with schizophrenia were interviewed using the Scale of Prodromal Symptoms and the Tanner Maturational Scale. Age at Tanner pubertal stage was determined and regression analyses were used to explore associations between prodromal symptoms and age at puberty.

RESULTS

Among males, delayed age at puberty was associated with greater severity of prodromal symptoms; the association between negative prodromal symptoms and delayed age was significant (p=0.001). In females, the association was not statistically significant.

CONCLUSIONS

Our results suggest that delayed age at puberty may be associated with negative prodromal symptoms of schizophrenia in males. Our findings suggest that delayed age at puberty could potentially be a predictive biomarker for psychopathology in males at risk for schizophrenia.

Validation of mismatch negativity and P3a for use in multi-site studies of schizophrenia: characterization of demographic, clinical, cognitive, and functional correlates in COGS-2

Mismatch negativity (MMN) and P3a are auditory event-related potential (ERP) components that show robust deficits in schizophrenia (SZ) patients and exhibit qualities of endophenotypes, including substantial heritability, test-retest reliability, and trait-like stability. These measures also fulfill criteria for use as cognition and function-linked biomarkers in outcome studies, but have not yet been validated for use in large-scale multi-site clinical studies. This study tested the feasibility of adding MMN and P3a to the ongoing Consortium on the Genetics of Schizophrenia (COGS) study. The extent to which demographic, clinical, cognitive, and functional characteristics contribute to variability in MMN and P3a amplitudes was also examined. Participants (HCS n=824, SZ n=966) underwent testing at 5 geographically distributed COGS laboratories. Valid ERP recordings were obtained from 91% of HCS and 91% of SZ patients. Highly significant MMN (d=0.96) and P3a (d=0.93) amplitude reductions were observed in SZ patients, comparable in magnitude to those observed in single-lab studies with no appreciable differences across laboratories. Demographic characteristics accounted for 26% and 18% of the variance in MMN and P3a amplitudes, respectively. Significant relationships were observed among demographically-adjusted MMN and P3a measures and medication status as well as several clinical, cognitive, and functional characteristics of the SZ patients. This study demonstrates that MMN and P3a ERP biomarkers can be feasibly used in multi-site clinical studies. As with many clinical tests of brain function, demographic factors contribute to MMN and P3a amplitudes and should be carefully considered in future biomarker-informed clinical studies.

Mismatch negativity latency as a biomarker of amnestic mild cognitive impairment in chinese rural elders

The aim was to evaluate the mismatch negativity (MMN) component, a correlate of the automatic detection of changes in the acoustic environment, in healthy adults, and adults with amnestic mild cognitive impairment (aMCI). Forty-three aMCI subjects and 43 healthy Chinese older adults were arranged into experimental group and control group, respectively. Their MMN amplitude and latency were measured at the FZ, FCZ, and CZ electrode sites under a passive auditory oddball task. The results showed that the latencies obtained from the FZ, FCZ, and CZ electrode sites were significantly longer in the aMCI adults than in the control adults (P  < 0.01) while there were no significant differences in MMN amplitude between two groups (P  > 0.05). The MMN latency was found to be a sensitive and specific biomarker of aMCI.

Future clinical uses of neurophysiological biomarkers to predict and monitor treatment response for schizophrenia

Advances in psychiatric neuroscience have transformed our understanding of impaired and spared brain functions in psychotic illnesses. Despite substantial progress, few (if any) laboratory tests have graduated to clinics to inform diagnoses, guide treatments, and monitor treatment response. Providers must rely on careful behavioral observation and interview techniques to make inferences about patients' inner experiences and then secondary deductions about impacted neural systems. Development of more effective treatments has also been hindered by a lack of translational quantitative biomarkers that can span the brain-behavior treatment knowledge gap. Here, we describe an example of a simple, low-cost, and translatable electroencephalography (EEG) measure that offers promise for improving our understanding and treatment of psychotic illnesses: mismatch negativity (MMN). MMN is sensitive to and/or predicts response to some pharmacologic and nonpharmacologic interventions and accounts for substantial portions of variance in clinical, cognitive, and psychosocial functioning in schizophrenia (SZ). This measure has recently been validated for use in large-scale multisite clinical studies of SZ. Finally, MMN greatly improves our ability to forecast which individuals at high clinical risk actually develop a psychotic illness. These attributes suggest that MMN can contribute to personalized biomarker-guided treatment strategies aimed at ameliorating or even preventing the onset of psychosis.

Equivalent mismatch negativity deficits across deviant types in early illness schizophrenia-spectrum patients

Neurophysiological abnormalities in auditory deviance processing, as reflected by the mismatch negativity (MMN), have been observed across the course of schizophrenia. Studies in early schizophrenia patients have typically shown varying degrees of MMN amplitude reduction for different deviant types, suggesting that different auditory deviants are uniquely processed and may be differentially affected by duration of illness. To explore this further, we examined the MMN response to 4 auditory deviants (duration, frequency, duration+frequency "double deviant", and intensity) in 24 schizophrenia-spectrum patients early in the illness (ESZ) and 21 healthy controls. ESZ showed significantly reduced MMN relative to healthy controls for all deviant types (p<0.05), with no significant interaction with deviant type. No correlations with clinical symptoms were present (all ps>0.05). These findings support the conclusion that neurophysiological mechanisms underlying processing of auditory deviants are compromised early in illness, and these deficiencies are not specific to the type of deviant presented.

Mismatch negativity (MMN) deficiency: a break-through biomarker in predicting psychosis onset

Currently, the mismatch negativity (MMN) deficit is one of the most robust and replicable findings in schizophrenia, reflecting cognitive and functional decline, psychosocial and socio-occupational impairment, and executive dysfunction in these patients. An important break-through has very recently taken place here in the prediction of conversion to psychosis when the MMN in particular to change in tone duration was recorded in clinically at risk-mental state (ARMS) individuals. Attenuations in the MMN in these patients may be very useful in helping clinicians determine who are most likely to develop a psychotic disorder, as we will review in the present article.

Prolonged cortical silent period among drug-naive subjects at ultra-high risk of psychosis

BACKGROUND

Deficits in gamma-aminobutyric acid (GABA) inhibitory neurotransmission have been associated with pathophysiological mechanisms underlying schizophrenia. However, little is known about whether these deficits occur before or after the onset of psychosis.

METHOD

We recruited 16 drug-naive subjects at ultra-high risk of psychosis (UHR), 17 schizophrenia patients and 28 healthy controls. Cortical inhibition was determined using transcranial magnetic stimulation (TMS) over the left primary motor cortex. TMS markers such as short-interval cortical inhibition (SICI), cortical silent period (CSP) and intracortical facilitation (ICF) were obtained from each subject. While SICI can reflect GABA type A (GABAA) mediated inhibition, CSP is thought to indicate GABA type B (GABAB) mediated inhibitory circuits.

RESULTS

As compared with healthy controls, UHR subjects showed a prolonged CSP with no change in SICI, whereas schizophrenia patients demonstrated both a prolonged CSP and a reduced SICI. No group differences were found for ICF. CSP in schizophrenia patients also had a positive correlation with positive symptom score of the positive and negative symptom scale (PANSS).

CONCLUSIONS

Cortical inhibitory deficits among UHR subjects were relatively limited compared to those among schizophrenia patients. Alterations might occur in some subgroup of GABA-mediated neurotransmitter systems before the onset of psychosis, while alterations in both GABAA and GABAB networks might contribute to full-blown psychosis.

Modulation of auditory deviance detection by acute nicotine is baseline and deviant dependent in healthy nonsmokers: a mismatch negativity study

OBJECTIVE

Cognitive enhancement resulting from nicotinic acetylcholine receptor stimulation may be evidenced by increased efficiency of the auditory-frontal cortex network of auditory discrimination, which is impaired in schizophrenia, a cognitive disorder associated with excessive tobacco use. Investigating automatic (preattentive) detection of acoustic change with the mismatch negativity (MMN) brain event-related potential in response to nicotine in individuals with varying baseline levels of auditory discrimination may provide useful insight into the cholinergic regulation of this neural network and its potential amelioration with novel nicotinic agents.

METHODS

Sixty healthy, non-smoking male volunteers were presented with an 'optimal' multi-feature MMN paradigm in a randomized, placebo controlled double-blind design with 6 mg of nicotine gum.

RESULTS

Participants with low, medium, and high baseline amplitudes responded differently to nicotine (vs. placebo), and nicotine response was feature specific. Whereas MMN in individuals with high amplitudes was diminished by nicotine, MMN increased in those with low amplitudes. Nicotine effects were not shown in medium amplitude participants.

CONCLUSIONS

These findings provide preliminary support for the role of nicotinic neurotransmission in sensory memory processing of auditory change and suggest that nicotinic receptor modulation can both enhance and diminish change detection, depending on baseline MMN and its eliciting stimulus feature.

Neurophysiological biomarkers informing the clinical neuroscience of schizophrenia: mismatch negativity and prepulse inhibition of startle

With the growing recognition of the heterogeneity of major brain disorders, and particularly the schizophrenias (SZ), biomarkers are being sought that parse patient groups in ways that can be used to predict treatment response, prognosis, and pathophysiology. A primary focus to date has been to identify biomarkers that predict damage or dysfunction within brain systems in SZ patients, that could then serve as targets for interventions designed to "undo" the causative pathology. After almost 50 years as the predominant strategy for developing SZ therapeutics, evidence supporting the value of this "find what's broke and fix it" approach is lacking. Here, we suggest an alternative strategy of using biomarkers to identify evidence of spared neural and cognitive function in SZ patients, and matching these residual neural assets with therapies toward which they can be applied. We describe ways to extract and interpret evidence of "spared function," using neurocognitive, and neurophysiological measures, and, suggest that further evidence of available neuroplasticity might be gleaned from studies in which the response to drug challenges and "practice effects" are measured. Finally, we discuss examples in which "better" (more normal) performance in specific neurophysiological measures predict a positive response to a neurocognitive task or therapeutic intervention. We believe that our field stands to gain tremendous therapeutic leverage by focusing less on what is "wrong" with our patients, and instead, focusing more on what is "right".

Mismatch negativity (MMN) as an index of cognitive dysfunction

Cognition is often affected in a variety of neuropsychiatric, neurological, and neurodevelopmental disorders. The neural discriminative response, reflected in mismatch negativity (MMN) and its magnetoencephalographic equivalent (MMNm), has been used as a tool to study a variety of disorders involving auditory cognition. MMN/MMNm is an involuntary brain response to auditory change or, more generally, to pattern regularity violation. For a number of disorders, MMN/MMNm amplitude to sound deviance has been shown to be attenuated or the peak-latency of the component prolonged compared to controls. This general finding suggests that while not serving as a specific marker to any particular disorder, MMN may be useful for understanding factors of cognition in various disorders, and has potential to serve as an indicator of risk. This review presents a brief history of the MMN, followed by a description of how MMN has been used to index auditory processing capability in a range of neuropsychiatric, neurological, and neurodevelopmental disorders. Finally, we suggest future directions for research to further enhance our understanding of the neural substrate of deviance detection that could lead to improvements in the use of MMN as a clinical tool.

Contributions of experimental psychiatry to research on the psychosis prodrome

In the recent decades, a paradigmatic change in psychosis research and treatment shifted attention toward the early and particularly the prodromal stages of illness. Despite substantial progress with regard to the neuronal underpinnings of psychosis development, the crucial biological mechanisms leading to manifest illness are yet insufficiently understood. Until today, one significant approach to elucidate the neurobiology of psychosis has been the modeling of psychotic symptoms by psychedelic substances in healthy individuals. These models bear the opportunity to evoke particular neuronal aberrations and the respective psychotic symptoms in a controlled experimental setting. In the present paper, we hypothesize that experimental psychiatry bears unique opportunities in elucidating the biological mechanisms of the prodromal stages of psychosis. Psychosis risk symptoms are attenuated, transient, and often only retrospectively reported. The respective neuronal aberrations are thought being dynamic. The correlation of unstable psychopathology with observed neurofunctional disturbances is thus yet largely unclear. In modeling psychosis, the experimental setting allows not only for evoking particular symptoms, but for the concomitant assessment of psychopathology, neurophysiology, and neuropsychology. Herein, the glutamatergic model will be highlighted exemplarily, with special emphasis on its potential contribution to the elucidation of psychosis development. This model of psychosis appears as candidate for modeling the prodrome by inducing psychotic-like symptoms in healthy individuals. Furthermore, it alters pre-attentive processing like the Mismatch Negativity, an electrophysiological component which has recently been identified as a potential predictive marker of psychosis development. In summary, experimental psychiatry bears the potential to further elucidate the biological mechanisms of the psychosis prodrome. A better understanding of the respective pathophysiology might assist in the identification of predictive markers, and the development of preventive treatments.