The Mechanisms and Meaning of the Mismatch Negativity

Cortical responses to looming sources are explained away by the auditory periphery

A wealth of behavioral evidence indicate that sounds with increasing intensity (i.e. appear to be looming towards the listener) are processed with increased attentional and physiological resources compared to receding sounds. However, the neurophysiological mechanism responsible for such cognitive amplification remains elusive. Here, we show that the large differences seen between cortical responses to looming and receding sounds are in fact almost entirely explained away by nonlinear encoding at the level of the auditory periphery. We collected electroencephalography (EEG) data during an oddball paradigm to elicit mismatch negativity (MMN) and others Event Related Potentials (EPRs), in response to deviant stimuli with both dynamic (looming and receding) and constant level (flat) differences to the standard in the same participants. We then combined a computational model of the auditory periphery with generative EEG methods (temporal response functions, TRFs) to model the single-participant ERPs responses to flat deviants, and used them to predict the effect of the same mechanism on looming and receding stimuli. The flat model explained 45% variance of the looming response, and 33% of the receding response. This provide striking evidence that difference wave responses to looming and receding sounds result from the same cortical mechanism that generate responses to constant-level deviants: all such differences are the sole consequence of their particular physical morphology getting amplified and integrated by peripheral auditory mechanisms. Thus, not all effects seen cortically proceed from top-down modulations by high-level decision variables, but can rather be performed early and efficiently by feed-forward peripheral mechanisms that evolved precisely to sparing subsequent networks with the necessity to implement such mechanisms.

Auditory prediction errors in sound frequency and duration generated different cortical activation patterns in the human brain: an ECoG study

Sound frequency and duration are essential auditory components. The brain perceives deviations from the preceding sound context as prediction errors, allowing efficient reactions to the environment. Additionally, prediction error response to duration change is reduced in the initial stages of psychotic disorders. To compare the spatiotemporal profiles of responses to prediction errors, we conducted a human electrocorticography study with special attention to high gamma power in 13 participants who completed both frequency and duration oddball tasks. Remarkable activation in the bilateral superior temporal gyri in both the frequency and duration oddball tasks were observed, suggesting their association with prediction errors. However, the response to deviant stimuli in duration oddball task exhibited a second peak, which resulted in a bimodal response. Furthermore, deviant stimuli in frequency oddball task elicited a significant response in the inferior frontal gyrus that was not observed in duration oddball task. These spatiotemporal differences within the Parasylvian cortical network could account for our efficient reactions to changes in sound properties. The findings of this study may contribute to unveiling auditory processing and elucidating the pathophysiology of psychiatric disorders.

Time-resolved dynamic computational modeling of human EEG recordings reveals gradients of generative mechanisms for the MMN response

Despite attempts to unify the different theoretical accounts of the mismatch negativity (MMN), there is still an ongoing debate on the neurophysiological mechanisms underlying this complex brain response. On one hand, neuronal adaptation to recurrent stimuli is able to explain many of the observed properties of the MMN, such as its sensitivity to controlled experimental parameters. On the other hand, several modeling studies reported evidence in favor of Bayesian learning models for explaining the trial-to-trial dynamics of the human MMN. However, direct comparisons of these two main hypotheses are scarce, and previous modeling studies suffered from methodological limitations. Based on reports indicating spatial and temporal dissociation of physiological mechanisms within the timecourse of mismatch responses in animals, we hypothesized that different computational models would best fit different temporal phases of the human MMN. Using electroencephalographic data from two independent studies of a simple auditory oddball task (n = 82), we compared adaptation and Bayesian learning models' ability to explain the sequential dynamics of auditory deviance detection in a time-resolved fashion. We first ran simulations to evaluate the capacity of our design to dissociate the tested models and found that they were sufficiently distinguishable above a certain level of signal-to-noise ratio (SNR). In subjects with a sufficient SNR, our time-resolved approach revealed a temporal dissociation between the two model families, with high evidence for adaptation during the early MMN window (from 90 to 150-190 ms post-stimulus depending on the dataset) and for Bayesian learning later in time (170-180 ms or 200-220ms). In addition, Bayesian model averaging of fixed-parameter models within the adaptation family revealed a gradient of adaptation rates, resembling the anatomical gradient in the auditory cortical hierarchy reported in animal studies.

Contribution of inter-trial phase coherence at theta, alpha, and beta frequencies in auditory change detection

Introduction

Auditory change detection is a pre-attentive cortical auditory processing ability. Many neurological and psychological disorders can lead to defects in this process. Some studies have shown that phase synchronization may be related to auditory discrimination. However, the specific contributions of phase synchronization at different frequencies remain unclear.

Methods

We analyzed the electroencephalogram (EEG) data of 29 healthy adults using an oddball paradigm consisting of a standard stimulus and five deviant stimuli with varying frequency modulation patterns, including midpoint frequency transitions and linear frequency modulation. We then compared the peak amplitude and latency of inter-trial phase coherence (ITC) at the theta(θ), alpha(α), and beta(β) frequencies, as well as the N1 component, and their relationships with stimulus changes. At the same time, the characteristics of inter-trial phase coherence in response to the pure tone stimulation and chirp sound with a fine time-frequency structure were also assessed.

Result

When the stimulus frequency did not change relative to the standard stimulus, the peak latency of phase coherence at β and α frequencies was consistent with that of the N1 component. The inter-trial phase coherence at β frequency (β-ITC)served as a faster indicator for detecting frequency transition when the stimulus frequency was changed relative to the standard stimulus. β-ITC demonstrates temporal stability when detecting pure sinusoidal tones and their frequency changes, and is less susceptible to interference from other neural activities. The phase coherence at θ frequency could integrate the frequency and temporal characteristics of deviant into a single representation, which can be compared with the memory trace formed by the standard stimulus, thus effectively identifying auditory changes. Pure sinusoidal tone stimulation could induce higher inter-trial phase coherence in a smaller time window, but chirp sounds with a fine time-frequency structure required longer latencies to achieve phase coherence.

Conclusion

Phase coherence at theta, alpha, and beta frequencies are all involved in auditory change detection, but play different roles in this automatic process. Complex time-frequency modulated stimuli require longer processing time for effective change detection.

Laminar neural dynamics of auditory evoked responses: Computational modeling of local field potentials in auditory cortex of non-human primates

Evoked neural responses to sensory stimuli have been extensively investigated in humans and animal models both to enhance our understanding of brain function and to aid in clinical diagnosis of neurological and neuropsychiatric conditions. Recording and imaging techniques such as electroencephalography (EEG), magnetoencephalography (MEG), local field potentials (LFPs), and calcium imaging provide complementary information about different aspects of brain activity at different spatial and temporal scales. Modeling and simulations provide a way to integrate these different types of information to clarify underlying neural mechanisms. In this study, we aimed to shed light on the neural dynamics underlying auditory evoked responses by fitting a rate-based model to LFPs recorded via multi-contact electrodes which simultaneously sampled neural activity across cortical laminae. Recordings included neural population responses to best-frequency (BF) and non-BF tones at four representative sites in primary auditory cortex (A1) of awake monkeys. The model considered major neural populations of excitatory, parvalbumin-expressing (PV), and somatostatin-expressing (SOM) neurons across layers 2/3, 4, and 5/6. Unknown parameters, including the connection strength between the populations, were fitted to the data. Our results revealed similar population dynamics, fitted model parameters, predicted equivalent current dipoles (ECD), tuning curves, and lateral inhibition profiles across recording sites and animals, in spite of quite different extracellular current distributions. We found that PV firing rates were higher in BF than in non-BF responses, mainly due to different strengths of tonotopic thalamic input, whereas SOM firing rates were higher in non-BF than in BF responses due to lateral inhibition. In conclusion, we demonstrate the feasibility of the model-fitting approach in identifying the contributions of cell-type specific population activity to stimulus-evoked LFPs across cortical laminae, providing a foundation for further investigations into the dynamics of neural circuits underlying cortical sensory processing.

Basic auditory processing and its relationship with symptoms in patients with schizophrenia: A systematic review

Processing of basic auditory features, one of the earliest stages of auditory perception, has been the focus of considerable investigations in schizophrenia. Although numerous studies have shown abnormalities in pitch perception in schizophrenia, other basic auditory features such as intensity, duration, and sound localization have been less explored. Additionally, the relationship between basic auditory features and symptom severity shows inconsistent results, preventing concrete conclusions. Our aim was to present a comprehensive overview of basic auditory processing in schizophrenia and its relationship with symptoms. We conducted a systematic review according to the PRISMA guidelines. PubMed, Embase, and PsycINFO databases were searched for studies exploring auditory perception in schizophrenia compared to controls, with at least one behavioral task investigating basic auditory processing using pure tones. Forty-one studies were included. The majority investigated pitch processing while the others investigated intensity, duration and sound localization. The results revealed that patients have a significant deficit in the processing of all basic auditory features. Although the search for a relationship with symptoms was limited, auditory hallucinations experience appears to have an impact on basic auditory processing. Further research may examine correlations with clinical symptoms to explore the performance of patient subgroups and possibly implement remediation strategies.

Sound localization and auditory selective attention in school-aged children with ADHD

This study aimed to identify the neurophysiologic bases of auditory attention deficits in children with attention-deficit/hyperactivity disorder (ADHD), focusing on the electroencephalography component of auditory spatial selective attention [the N2 anterior contralateral component (N2ac)]. EEG data were collected from 7- to 11-year-old children with ADHD (n = 54) and age-, sex-, and IQ-matched typically developing (TD) children (n = 61), while they performed an auditory spatial selective task. For behavior, the children with ADHD showed a shorter reaction time (RT) but a higher RT coefficient of variability (RT_CV) than TD children. For ERPs, the TD group showed a significant "adult-like" N2ac component; however, the N2ac component was absent in children with ADHD. More importantly, the smaller N2ac component could predict longer RT in both groups, as well as higher severity of inattentive symptoms in children with ADHD. Our results indicated that 7- to 11-year-old TD children have developed an "adult-like" ability to balance auditory target selection and distractor suppression; the absence of N2ac in children with ADHD provided novel evidence supporting their dysfunctional auditory spatial selective attention.

Relationship between early neural responses to syntactic and acoustic irregularities in music

Humans can detect various anomalies in a sound sequence without attending to each dimension explicitly. Event-related potentials (ERPs) have been used to examine the processes of auditory deviance detection. Previous research has shown that music-syntactic anomalies elicit early right anterior negativity (ERAN), whereas more general acoustic irregularities elicit mismatch negativity (MMN). Although these ERP components occur in a similar latency range with a similar scalp topography, the relationship between the detection processes they reflect remains unclear. This study compared these components by manipulating music-syntactic (chord progression) and acoustic (intensity) irregularities orthogonally in two experiments. Non-musicians (Experiment 1: N = 39; Experiment 2: N = 24) were asked to listen to chord sequences, each consisting of 5 four-voice chords, as they watched a silent video clip. Standard, harmonic-deviant, intensity-deviant and double-deviant chords occurred at the final position in each sequence. Deviant stimuli were presented infrequently (p = .10) in Experiment 1 and equiprobably (p = .25) in Experiment 2. Regardless of deviance probability, both harmonic and intensity deviants elicited similar negativities, which were indistinguishable in terms of latency or scalp distribution. When the two deviant types occurred simultaneously, the negativity increased in an additive manner; that is, the amplitude of the double-deviant ERP was as large as the sum of the single-deviant ERPs. These findings suggest that the detection of music-syntactic and acoustic irregularities works independently, based on different regularity representations.

Multi-feature mismatch negativity: How can reliable data be recorded in a short time?

OBJECTIVE

The aim of the study was to conduct multi-feature mismatch negativity (MMN) implementations and identify via a test-retest study the reliability of MMN responses obtained through a 5-stimulus version of the MMN paradigm. It was also aimed to identify a reliable MMN recording number by comparing the MMN responses obtained under conditions of ten and four recordings conditions while making the recording time shorter.

METHODS

Twenty-one healthy volunteers, aged between 18 and 36 years, were included in the study. A 5-stimulus version of the multi-feature MMN paradigm was presented to participants. Ten recordings were obtained for each participant under both test and retest conditions. The MATLAB program was utilized in the evaluation of MMN amplitude and latency. The Fz was chosen for the statistical analysis. Four of the ten recordings were chosen at random, and statistical analyses were performed again for those four recordings.

RESULTS

There was no statistically significant difference in amplitudes obtained from test and retest conditions with ten recordings. With four recordings, for frequency, intensity, duration, and gap deviants, there were no statistically significant differences between amplitudes obtained under test and retest conditions. However, there was a statistically significant difference between amplitudes of the location deviant. No statistically significant difference was observed among latencies under test-retest conditions with both ten and four recordings.

CONCLUSIONS

These findings demonstrate that MMN amplitudes could be used reliably as short-time evaluations with four recordings, but more recordings are required for MMN latencies. In terms of practicality, four recordings are more advantageous and comfortable for both clinicians and patients in MMN practice.

SIGNIFICANCE

When behavioral tests are required, MMN is regarded as an objective test that can be used reliably for adults, children, and infants who cannot be evaluated using behavioral methods. It is concluded that conditions with four recordings aremore advantageous and comfortable for both clinicians and patients in MMN practice.

Mismatch Negativity is associated with affective social behavior in microcephaly

Some children with severe microcephaly related to Zika virus infection show affective social-like behavior, such as smiling and rejection to a stranger's lap. Our objective was to check the association between this behavior and the occurrence of Mismatch Response (MMR) in event-related potentials. Twenty eight microcephalic children, aged 1-3 years, were divided in Affect(+) and Affect(-) groups, according to either the presence or absence of affective social-like behavior, respectively, and underwent the OddBall paradigm with vowels as auditory stimuli. MMR was statistically estimated comparing MMR sample means between both groups. The Affect(+) group significantly differed from the Affect(-) group and, as opposed to the latter, showed MMR as Mismatch Negativity (MMN) in the left occipital, left and right posterior temporal, and (especially) the right and median parietal leads. The relationship observed between MMN and affective social-like behavior suggests that these children may have cognitive mechanisms capable of providing some social interaction, despite their profound neurological dysfunction. MMN diagnostic techniques seem to be promising for the triage of microcephalic subjects regarding cognitive functions and for choosing a strategy for some social adaptation.

Clinical and investigational tools for monitoring noise-induced hyperacusis

Hyperacusis is a recognized perceptual consequence of acoustic overexposure that can lead to debilitating psychosocial effects. Despite the profound impact of hyperacusis on quality of life, clinicians and researchers lack objective biomarkers and standardized protocols for its assessment. Outcomes of conventional audiologic tests are highly variable in the hyperacusis population and do not adequately capture the multifaceted nature of the condition on an individual level. This presents challenges for the differential diagnosis of hyperacusis, its clinical surveillance, and evaluation of new treatment options. Multiple behavioral and objective assays are emerging as contenders for inclusion in hyperacusis assessment protocols but most still await rigorous validation. There remains a pressing need to develop tools to quantify common nonauditory symptoms, including annoyance, fear, and pain. This review describes the current literature on clinical and investigational tools that have been used to diagnose and monitor hyperacusis, as well as those that hold promise for inclusion in future trials.

Distinct Patterns of Automatic and Controlled Incongruent Information Processing in the Human Brain

It is a fundamental ability to discriminate incongruent information in daily activity. However, the underlying neural dynamics are still unclear. Using stereoelectroencephalography (SEEG), in this study, we investigated the fine-grained and different states of incongruent information processing in patients with refractory epilepsy who underwent intracranial electrode implantation. All patients performed a delayed match-to-sample paradigm in the sequential pairs of visual stimuli (S1 followed by S2). Participants were asked to discriminate whether the relevant feature of S2 was identical to S1 while ignoring the irrelevant feature. The spatiotemporal cortical responses evoked by different conditions were calculated and compared, respectively, in the context of brain intrinsic functional networks. In total, we obtained SEEG recordings from 241 contacts in gray matter. In the processing of irrelevant incongruent information, the activated brain areas included the superior parietal lobule, supramarginal gyrus, angular gyrus, inferior temporal gyrus, and fusiform gyrus. By comparing the relevant incongruent condition with the congruent condition, the activated brain areas included the middle frontal gyrus, superior temporal gyrus, middle temporal gyrus, posterior superior temporal sulcus, and posterior cingulate cortex. We demonstrated the dynamics of incongruent information processing with high spatiotemporal resolution and suggested that the process of automatic detection of irrelevant incongruent information requires the involvement of local regions and relatively few networks. Meanwhile, controlled discrimination of relevant incongruent information requires the participation of extensive regions and a wide range of nodes in the network. Furthermore, both the frontoparietal control network and default mode network were engaged in the incongruent information processing.

Electrophysiological and Behavioral Evidence for Hyper- and Hyposensitivity in Rare Genetic Syndromes Associated with Autism

Our study reviewed abnormalities in spontaneous, as well as event-related, brain activity in syndromes with a known genetic underpinning that are associated with autistic symptomatology. Based on behavioral and neurophysiological evidence, we tentatively subdivided the syndromes on primarily hyper-sensitive (Fragile X, Angelman) and hypo-sensitive (Phelan–McDermid, Rett, Tuberous Sclerosis, Neurofibromatosis 1), pointing to the way of segregation of heterogeneous idiopathic ASD, that includes both hyper-sensitive and hypo-sensitive individuals. This segmentation links abnormalities in different genes, such as FMR1, UBE3A, GABRB3, GABRA5, GABRG3, SHANK3, MECP2, TSC1, TSC2, and NF1, that are causative to the above-mentioned syndromes and associated with synaptic transmission and cell growth, as well as with translational and transcriptional regulation and with sensory sensitivity. Excitation/inhibition imbalance related to GABAergic signaling, and the interplay of tonic and phasic inhibition in different brain regions might underlie this relationship. However, more research is needed. As most genetic syndromes are very rare, future investigations in this field will benefit from multi-site collaboration with a common protocol for electrophysiological and event-related potential (EEG/ERP) research that should include an investigation into all modalities and stages of sensory processing, as well as potential biomarkers of GABAergic signaling (such as 40-Hz ASSR).

The Adaptation Model Offers a Challenge for the Predictive Coding Account of Mismatch Negativity

An unpredictable stimulus elicits a stronger event-related response than a high-probability stimulus. This differential in response magnitude is termed the mismatch negativity (MMN). Over the past decade, it has become increasingly popular to explain the MMN terms of predictive coding, a proposed general principle for the way the brain realizes Bayesian inference when it interprets sensory information. This perspective article is a reminder that the issue of MMN generation is far from settled, and that an alternative model in terms of adaptation continues to lurk in the wings. The adaptation model has been discounted because of the unrealistic and simplistic fashion in which it tends to be set up. Here, simulations of auditory cortex incorporating a modern version of the adaptation model are presented. These show that locally operating short-term synaptic depression accounts both for adaptation due to stimulus repetition and for MMN responses. This happens even in cases where adaptation has been ruled out as an explanation of the MMN (e.g., in the stimulus omission paradigm and the multi-standard control paradigm). Simulation models that would demonstrate the viability of predictive coding in a similarly multifaceted way are currently missing from the literature, and the reason for this is discussed in light of the current results.

Predictability-Based Source Segregation and Sensory Deviance Detection in Auditory Aging

When multiple sound sources are present at the same time, auditory perception is often challenged with disentangling the resulting mixture and focusing attention on the target source. It has been repeatedly demonstrated that background (distractor) sound sources are easier to ignore when their spectrotemporal signature is predictable. Prior evidence suggests that this ability to exploit predictability for foreground-background segregation degrades with age. On a theoretical level, this has been related with an impairment in elderly adults’ capabilities to detect certain types of sensory deviance in unattended sound sequences. Yet the link between those two capacities, deviance detection and predictability-based sound source segregation, has not been empirically demonstrated. Here we report on a combined behavioral-EEG study investigating the ability of elderly listeners (60–75 years of age) to use predictability as a cue for sound source segregation, as well as their sensory deviance detection capacities. Listeners performed a detection task on a target stream that can only be solved when a concurrent distractor stream is successfully ignored. We contrast two conditions whose distractor streams differ in their predictability. The ability to benefit from predictability was operationalized as performance difference between the two conditions. Results show that elderly listeners can use predictability for sound source segregation at group level, yet with a high degree of inter-individual variation in this ability. In a further, passive-listening control condition, we measured correlates of deviance detection in the event-related brain potential (ERP) elicited by occasional deviations from the same spectrotemporal pattern as used for the predictable distractor sequence during the behavioral task. ERP results confirmed neural signatures of deviance detection in terms of mismatch negativity (MMN) at group level. Correlation analyses at single-subject level provide no evidence for the hypothesis that deviance detection ability (measured by MMN amplitude) is related to the ability to benefit from predictability for sound source segregation. These results are discussed in the frameworks of sensory deviance detection and predictive coding.

Arousal State-Dependence of Interactions Between Short- and Long-Term Auditory Novelty Responses in Human Subjects

In everyday life, predictable sensory stimuli are generally not ecologically informative. By contrast, novel or unexpected stimuli signal ecologically salient changes in the environment. This idea forms the basis of the predictive coding hypothesis: efficient sensory encoding minimizes neural activity associated with predictable backgrounds and emphasizes detection of changes in the environment. In real life, the brain must resolve multiple unexpected sensory events occurring over different time scales. The local/global deviant experimental paradigm examines auditory predictive coding over multiple time scales. For short-term novelty [hundreds of milliseconds; local deviance (LD)], sequences of identical sounds (/xxxxx/) are interspersed with sequences that contain deviants (/xxxxy/). Long-term novelty [several seconds; global deviance (GD)] is created using either (a) frequent /xxxxx/ and infrequent /xxxxy/ sequences, or (b) frequent /xxxxy/ and infrequent /xxxxx/ sequences. In scenario (a), there is both an LD and a GD effect (LDGD, "double surprise"). In (b), the global deviant is a local standard, i.e., sequence of identical sounds (LSGD). Cortical responses reflecting LD and GD originate in different brain areas, have a different time course, and are differentially sensitive to general anesthesia. Neural processes underlying LD and GD have been shown to interact, reflecting overlapping networks subserving the detection of novel auditory stimuli. This study examined these interactions using intracranial electroencephalography in neurosurgical patients. Subjects performed a GD target detection task before and during induction of anesthesia with propofol. Recordings were made from the auditory cortex, surrounding auditory-related and prefrontal cortex in awake, sedated, and unresponsive states. High gamma activity was used to measure the neural basis of local-by-global novelty interactions. Positive interaction was defined as a greater response to the double surprise LDGD condition compared to LSGD. Negative interaction was defined as a weaker response to LDGD. Positive interaction was more frequent than negative interaction and was primarily found in auditory cortex. Negative interaction typically occurred in prefrontal cortex and was more sensitive to general anesthesia. Temporo-parietal auditory-related areas exhibited both types of interaction. These interactions may have relevance in a clinical setting as biomarkers of conscious perception in the assessment of depth of anesthesia and disorders of consciousness.

The role of attention and explicit knowledge in perceiving bistable auditory input

The auditory system frequently encounters ambiguous sound input that can be perceived in multiple ways. The current study investigated the role of explicit knowledge in modulating how sounds are represented in auditory memory for a bistable sound sequence that could be perceived equally as integrated or segregated. We hypothesized that the dominant percept of the bistable sequence would suppress representation of the alternative perceptual organization as a function of how much top-down knowledge the listener had about the structure of the sequence. Performance measures and event-related brain potentials were compared when participants had explicit knowledge about one perceptual organization in the first half of the experiment to when they had explicit knowledge of both in the second half. We hypothesized that knowledge would modify the brain response to the alternative percept of the bistable sequence. However, that did not occur. When participants were performing one task, with no explicit knowledge of the bistable structure of the sequence, both integrated and segregated percepts were represented in auditory working memory. This demonstrates that explicit knowledge about the sounds is not a necessary factor for deriving and maintaining representations of multiple sound organizations within a complex sound environment. Passive attention operates in parallel with active or selective attention to maintain consistent representations of the environment, representations that may or may not be useful for task performance. It suggests a highly adaptive system useful in everyday listening situations where the listener has no prior knowledge about how the sound environment is structured.

A Critical Review of the Deviance Detection Theory of Mismatch Negativity

Mismatch negativity (MMN) is a component of the difference waveform derived from passive auditory oddball stimulation. Since its inception in 1978, this has become one of the most popular event-related potential techniques, with over two-thousand published studies using this method. This is a testament to the ingenuity and commitment of generations of researchers engaging in basic, clinical and animal research. Despite this intensive effort, high-level descriptions of the mechanisms theorized to underpin mismatch negativity have scarcely changed over the past four decades. The prevailing deviance detection theory posits that MMN reflects inattentive detection of difference between repetitive standard and infrequent deviant stimuli due to a mismatch between the unexpected deviant and a memory representation of the standard. Evidence for these mechanisms is inconclusive, and a plausible alternative sensory processing theory considers fundamental principles of sensory neurophysiology to be the primary source of differences between standard and deviant responses evoked during passive oddball stimulation. By frequently being restated without appropriate methods to exclude alternatives, the potentially flawed deviance detection theory has remained largely dominant, which could lead some researchers and clinicians to assume its veracity implicitly. It is important to have a more comprehensive understanding of the source(s) of MMN generation before its widespread application as a clinical biomarker. This review evaluates issues of validity concerning the prevailing theoretical account of mismatch negativity and the passive auditory oddball paradigm, highlighting several limitations regarding its interpretation and clinical application.

Mismatch negativity as EEG biomarker supporting CNS drug development: a transnosographic and translational study

The lack of translation from basic research into new medicines is a major challenge in CNS drug development. The need to use novel approaches relying on (i) patient clustering based on neurobiology irrespective to symptomatology and (ii) quantitative biomarkers focusing on evolutionarily preserved neurobiological systems allowing back-translation from clinical to nonclinical research has been highlighted. Here we sought to evaluate the mismatch negativity (MMN) response in schizophrenic (SZ) patients, Alzheimer's disease (AD) patients, and age-matched healthy controls. To evaluate back-translation of the MMN response, we developed EEG-based procedures allowing the measurement of MMN-like responses in a rat model of schizophrenia and a mouse model of AD. Our results indicate a significant MMN attenuation in SZ but not in AD patients. Consistently with the clinical findings, we observed a significant attenuation of deviance detection (~104.7%) in rats subchronically exposed to phencyclidine, while no change was observed in APP/PS1 transgenic mice when compared to wild type. This study provides new insight into the cross-disease evaluation of the MMN response. Our findings suggest further investigations to support the identification of neurobehavioral subtypes that may help patients clustering for precision medicine intervention. Furthermore, we provide evidence that MMN could be used as a quantitative/objective efficacy biomarker during both preclinical and clinical stages of SZ drug development.

Selective adaptation in sentence comprehension: Evidence from event-related brain potentials

In this study, two event-related potential experiments were conducted to investigate whether readers adapt their expectations to morphosyntactically (Experiment 1) or semantically (Experiment 2) anomalous sentences when they are repeatedly exposed to them. To address this issue, we experimentally manipulated the probability of occurrence of grammatical sentences and syntactically and semantically anomalous sentences through experiments. For the low probability block, anomalous sentences were presented less frequently than grammatical sentences (with a ratio of 1 to 4), while they were presented as frequently as grammatical sentences in the equal probability block. Experiment 1 revealed a smaller P600 effect for morphosyntactic violations in the equal probability block than in the low probability block. Linear mixed-effects models were used to examine how the size of the P600 effect changed as the experiment went along. The results showed that the smaller P600 effect of the equal probability block resulted from an amplitude's decline in morphosyntactically violated sentences over the course of the experiment, suggesting an adaptation to morphosyntactic violations. In Experiment 2, semantically anomalous sentences elicited a larger N400 effect than their semantically natural counterparts regardless of probability manipulation. Little evidence was found in favour of adaptation to semantic violations in that the processing cost associated with the N400 did not decrease over the course of the experiment. Therefore, a dynamic aspect of language-processing system was demonstrated in this study. We will discuss why the language-processing system shows a selective adaptation to morphosyntactic violations.

Pre-attentive auditory change detection for rapid auditory transient combinations: Insight from age-related processing changes

The N1 event-related potential (ERP) enhancement to auditory transients preceded briefly by another transient has been interpreted as a reflection of latent inhibition, or alternatively, as a superimposing mismatch negativity (MMN) to rare transient event combinations. In a previous study (Volosin, Gaál, & Horváth, 2017a), when rare glides preceded frequent gaps by 150 ms in continuous tones, gap-related N1 was enhanced in younger adults while P2 was attenuated both in younger and older adults, which could be parsimoniously explained by MMN overlap which was delayed with aging. The present study replicated and extended these results with a condition in which the roles of the two event types were reversed. Transients separated by 150 ms elicited delayed MMN in older adults, supporting the MMN interpretation over the latent inhibition account. Furthermore, the divergence of N1 and MMN elicitation patterns demonstrated the independence of N1 and MMN.

High-frequency sound components of high-resolution audio are not detected in auditory sensory memory

High-resolution digital audio is believed to produce a better listening experience than the standard quality audio, such as compact disks (CDs) and digital versatile disks (DVDs). One common belief is that high-resolution digital audio is superior due to the higher frequency (> 22 kHz) of its sound components, a characteristic unique to this audio. This study examined whether sounds with high-frequency components were processed differently from similar sounds without these components in the auditory cortex. Mismatch negativity (MMN), an electrocortical index of auditory deviance detection in sensory memory, was recorded in young adults with normal hearing (N = 38) using two types of white noise bursts: original sound and digitally filtered sound from which high-frequency components were removed. The two sounds did not produce any MMN response and could not be discriminated behaviourally. In conclusion, even if high-resolution audio is superior to the standard format, the difference is apparently not detectable at the cortical level.

Prediction error signaling explains neuronal mismatch responses in the medial prefrontal cortex

The mismatch negativity (MMN) is a key biomarker of automatic deviance detection thought to emerge from 2 cortical sources. First, the auditory cortex (AC) encodes spectral regularities and reports frequency-specific deviances. Then, more abstract representations in the prefrontal cortex (PFC) allow to detect contextual changes of potential behavioral relevance. However, the precise location and time asynchronies between neuronal correlates underlying this frontotemporal network remain unclear and elusive. Our study presented auditory oddball paradigms along with "no-repetition" controls to record mismatch responses in neuronal spiking activity and local field potentials at the rat medial PFC. Whereas mismatch responses in the auditory system are mainly induced by stimulus-dependent effects, we found that auditory responsiveness in the PFC was driven by unpredictability, yielding context-dependent, comparatively delayed, more robust and longer-lasting mismatch responses mostly comprised of prediction error signaling activity. This characteristically different composition discarded that mismatch responses in the PFC could be simply inherited or amplified downstream from the auditory system. Conversely, it is more plausible for the PFC to exert top-down influences on the AC, since the PFC exhibited flexible and potent predictive processing, capable of suppressing redundant input more efficiently than the AC. Remarkably, the time course of the mismatch responses we observed in the spiking activity and local field potentials of the AC and the PFC combined coincided with the time course of the large-scale MMN-like signals reported in the rat brain, thereby linking the microscopic, mesoscopic, and macroscopic levels of automatic deviance detection.

Aberrant Frequency Related Change-Detection Activity in Chronic Tinnitus

Tinnitus is the perception of sound without the occurrence of an acoustic event. The deficit in auditory sensory or echoic memory may be the cause of the perception of tinnitus. This study considered the mismatch negativity (MMN) to investigate the potential difference between and within groups of persons with normal hearing (NH) and tinnitus. Using an auditory multi-feature paradigm to elicit the MMN, this study considered the MMN peak amplitude at two central frequencies for two MMN subcomponents. These central frequencies were 1 and 5 kHz, which the latter was closer to the perceived tinnitus frequency in the group with tinnitus. The deviants were higher frequency, lower frequency, higher intensity, lower intensity, duration, location (left), location (right), and gap. The pure tone audiometry (PTA) test and distortion product otoacoustic emissions (DPOAE) test showed no meaningful difference between the two groups. For the frontal subcomponent, the mean amplitudes of the MMN peak for the two groups illustrated less negative meaningful MMN peak amplitudes in the group of persons with tinnitus. For the supratemporal component at 5 kHz central frequency, amplitudes were lower for the group of persons with tinnitus, whereas for the central frequency of 1 kHz, most deviants exhibited meaningful differences. Additionally, within-group comparisons indicated that mean amplitudes for both groups were more negative at the central frequency of 1 kHz for the frontal MMN subcomponent. In comparison, the supratemporal component illustrated a lower peak amplitude at 5 kHz central frequency in the group of persons with tinnitus and no difference in the NH group, which is a unique observation of this study. Results of the between-groups are in accordance with previous studies and within-group comparisons consider the probability of decreasing the change detection capability of the brain. The results of this study indicate that increasing the frequency of the stimuli close to the tinnitus perceived frequencies decreases the prediction error, including the prediction error of the silence. Such a decrease may cause the prediction error of the spontaneous neural activity in the auditory pathway to exceed the silence prediction error, and as a result, increases the probability of occurrence of tinnitus in higher frequencies according to the predictive coding model.

Do rat auditory event related potentials exhibit human mismatch negativity attributes related to predictive coding?

Rodent models play a significant role in understanding disease mechanisms and the screening of new treatments. With regard to psychiatric disorders such as schizophrenia, however, it is difficult to replicate the human symptoms in rodents because these symptoms are often either 'uniquely human' or are only conveyed via self-report. There is a growing interest in rodent mismatch responses (MMRs) as a translatable 'biomarker' for disorders such as schizophrenia. In this review, we will summarize the attributes of human MMN, and discuss the scope of exploring the attributes of human MMN in rodents. Here, we examine how reliably MMRs that are measured in rats mimic human attributes, and present original data examining whether manipulations of stimulus conditions known to modulate human MMN, do the same for rat MMRs. Using surgically-implanted epidural electroencephalographic electrodes and wireless telemetry in freely-moving rats, we observed human-like modulations of MMRs, namely that larger MMRs were elicited to unexpected (deviant) stimuli that a) had a larger change in pitch compared to the expected (standard) stimulus, b) were less frequently presented (lower probability), and c) had no jitter (stable stimulus onset asynchrony) compared to high jitter. Overall, these findings contribute to the mounting evidence for rat MMRs as a good analogue of human MMN, bolstering the development of a novel approach in future to validate the preclinical models based on a translatable biomarker, MMN.

Combined Behavioral and Mismatch Negativity Evidence for the Effects of Long-Lasting High-Definition tDCS in Disorders of Consciousness: A Pilot Study

Objective

To evaluate the effects of long-term High-definition transcranial direct current stimulation (HD-tDCS) over precuneus on the level of consciousness (LOC) and the relationship between Mismatch negativity (MMN) and the LOC over the therapy period in patients with Disorders of consciousness (DOCs).

Methods

We employed a with-in group repeated measures design with an anode HD-tDCS protocol (2 mA, 20 min, the precuneus) on 11 (2 vegetative state and nine minimally conscious state) patients with DOCs. MMN and Coma Recovery Scale-Revised (CRS-R) scores were measured at four time points: before the treatment of HD-tDCS (T0), after a single session of HD-tDCS (T1), after the treatment of 7 days (T2) and 14 days (T3). A frequency-deviant oddball paradigm with two deviation magnitudes (standard stimulus: 1000 Hz, small deviant stimuli: 1050 Hz, large deviant stimuli: 1200 Hz) was adopted to elicit MMN.

Results

Significant improvements of CRS-R score were found after 7-day (T2) and 14-day (T3) treatment compared with baseline (T0). Regarding the MMN, significant improvements of MMN amplitudes were observed after a single session of stimulation (T1), 7-day (T2) and 14-day treatment (T3) compared with baseline (T0). Additionally, there were significant negative correlations between CRS-R scores and MMN amplitudes elicited by both large and small deviant stimuli.

Conclusion

Long-term HD-tDCS over precuneus might improve signs of consciousness in patients with DOCs as measured by CRS-R total scores, and MMN could be an assistant assessment in the course of tDCS treatment.

Cortical encoding of melodic expectations in human temporal cortex

Humans engagement in music rests on underlying elements such as the listeners' cultural background and interest in music. These factors modulate how listeners anticipate musical events, a process inducing instantaneous neural responses as the music confronts these expectations. Measuring such neural correlates would represent a direct window into high-level brain processing. Here we recorded cortical signals as participants listened to Bach melodies. We assessed the relative contributions of acoustic versus melodic components of the music to the neural signal. Melodic features included information on pitch progressions and their tempo, which were extracted from a predictive model of musical structure based on Markov chains. We related the music to brain activity with temporal response functions demonstrating, for the first time, distinct cortical encoding of pitch and note-onset expectations during naturalistic music listening. This encoding was most pronounced at response latencies up to 350 ms, and in both planum temporale and Heschl's gyrus.

The release from refractoriness hypothesis of N1 of event-related potentials needs reassessment

N1 of event-related potentials (ERPs) is augmented in amplitude in ∼50-150 ms by occasional changes (deviants) in the physical features of a sound repeated at intervals of from ∼400 ms to seconds (standard). The release-from-refractoriness hypothesis links the N1 augmentation to a deviant-feature-specific neural population that is fresh to fully respond as opposed to a standard-feature-specific neural population that is unresponsive due to its post-response refractoriness. The present work explored this hypothesis in the context of ERP studies, behavioral habituation studies and studies on stimulus-specific adaptation (SSA). The idea of hundreds of milliseconds neural population-level refractoriness was observed to be founded upon negative N1 evidence (no observable effect of dishabituating stimuli on N1 to standards - the null hypothesis retained) and merely supported by positive N1 evidence (null hypotheses rejected). This idea was also found to be directly challenged by positive N1 evidence. No conclusive network- or single-neuron-level evidence was found for the refractoriness. Therefore, the validity of the release-from-refractoriness hypothesis of N1 to guide psychophysiological research needs reassessment.

Encoding of deterministic and stochastic auditory rules in the human brain: The mismatch negativity mechanism does not reflect basic probability

Regularities in a sequence of sounds can be automatically encoded in a predictive model by the auditory system. When a sound deviates from the one predicted by the model, a mismatch negativity (MMN) is elicited, which is taken to reflect a prediction error at a particular level of the model hierarchy. Although there are many studies on deterministic regularities, only a few have investigated the brain's ability to encode non-deterministic regularities. We studied a simple stochastic regularity: two tone pitches (standards, each occurring on 45% of trials); this regularity was occasionally violated by another tone pitch (deviant, occurring on 10% of trials). We found MMN when the deviant's pitch was outside those of the standards, but not when it was between them. Importantly, when we alternated the occurrence of the same two standards, making them deterministic, the deviant elicited MMN, even when its pitch was between those of the standards. Thus, although the MMN system is extremely powerful in establishing even quite complex deterministic regularities, it fails with a simple stochastic regularity. We argue that the MMN system does not know basic probability.

Making Sense of Mismatch Negativity

Evoked potentials provide valuable insight into brain processes that are integral to our ability to interact effectively and efficiently in the world. The mismatch negativity (MMN) component of the evoked potential has proven highly informative on the ways in which sensitivity to regularity contributes to perception and cognition. This review offers a compendium of research on MMN with a view to scaffolding an appreciation for its use as a tool to explore the way regularities contribute to predictions about the sensory environment over many timescales. In compiling this work, interest in MMN as an index of sensory encoding and memory are addressed, as well as attention. Perspectives on the possible underlying computational processes are reviewed as well as recent observations that invite consideration of how MMN relates to how we learn, what we learn, and why.

Auditory Mismatch Negativity Under Predictive Coding Framework and Its Role in Psychotic Disorders

Traditional neuroscience sees sensory perception as a simple feedforward process. This view is challenged by the predictive coding model in recent years due to the robust evidence researchers had found on how our prediction could influence perception. In the first half of this article, we reviewed the concept of predictive brain and some empirical evidence of sensory prediction in visual and auditory processing. The predictive function along the auditory pathway was mainly studied by mismatch negativity (MMN)-a brain response to an unexpected disruption of regularity. We summarized a range of MMN paradigms and discussed how they could contribute to the theoretical development of the predictive coding neural network by the mechanism of adaptation and deviance detection. Such methodological and conceptual evolution sharpen MMN as a tool to better understand the structural and functional brain abnormality for neuropsychiatric disorder such as schizophrenia.

Evidence of Vowel Discrimination Provided by the Acoustic Change Complex

OBJECTIVES

The objectives of this study were to measure the effects of level and vowel contrast on the latencies and amplitudes of acoustic change complex (ACC) in the mature auditory system. This was done to establish how the ACC in healthy young adults is affected by these stimulus parameters that could then be used to inform translation of the ACC into a clinical measure for the pediatric population. Another aim was to demonstrate that a normalized amplitude metric, calculated by dividing the ACC amplitude in the vowel contrast condition by the ACC amplitude obtained in a control condition (no vowel change) would demonstrate good sensitivity with respect to perceptual measures of vowel-contrast detection. The premises underlying this research were that: (1) ACC latencies and amplitudes would vary with level, in keeping with principles of an increase in neural synchrony and activity that takes place as a function of increasing stimulus level; (2) ACC latencies and amplitudes would vary with vowel contrast, because cortical auditory evoked potentials are known to be sensitive to the spectro-temporal characteristics of speech.

DESIGN

Nineteen adults, 14 of them female, with a mean age of 24.2 years (range 20 to 38 years) participated in this study. All had normal-hearing thresholds. Cortical auditory evoked potentials were obtained from all participants in response to synthesized vowel tokens (/a/, /i/, /o/, /u/), presented in a quasi-steady state fashion at a rate of 2/sec in an oddball stimulus paradigm, with a 25% probability of the deviant stimulus. The ACC was obtained in response to the deviant stimulus. All combinations of vowel tokens were tested at 2 stimulus levels: 40 and 70 dBA. In addition, listeners were tested for their ability to detect the vowel contrasts using behavioral methods.

RESULTS

ACC amplitude varied systematically with level, and test condition (control versus contrast) and vowel token, but ACC latency did not. ACC amplitudes were significantly larger when tested at 70 dBA compared with 40 dBA and for contrast trials compared with control trials at both levels. Amplitude ratios (normalized amplitudes) were largest for contrast pairs in which /a/ was the standard token. The amplitude ratio metric at the individual level demonstrated up to 97% sensitivity with respect to perceptual measures of discrimination.

CONCLUSIONS

The present study establishes the effects of stimulus level and vowel type on the latency and amplitude of the ACC in the young adult auditory system and supports the amplitude ratio as a sensitive metric for cortical acoustic salience of vowel spectral features. Next steps are to evaluate these methods in infants and children with hearing loss with the long-term goal of its translation into a clinical method for estimating speech feature discrimination.

Visual Perceptual Load Does Not Affect the Frequency Mismatch Negativity

The mismatch negativity (MMN) has been of particular interest in auditory perception because of its sensitivity to auditory change. It is typically measured in an oddball task and is computed as the difference of deviant minus standard tones. Previous studies suggest that the oddball MMN can be reduced by crossmodal attention to a concurrent, difficult visual task. However, more recent studies did not replicate this effect. Because previous findings seem to be biased, we preregistered the present study and used Bayesian hypothesis testing to measure the strength of evidence for or against an effect of visual task difficulty. We manipulated visual perceptual load (high and low load). In the task, the visual stimuli were identical for both loads to avoid confounding effects from physical differences of the visual stimuli. We also measured the corrected MMN because the oddball MMN may be confounded by physical differences between deviant and standard tones. The corrected MMN is obtained with a separate control condition in which the same tone as the deviant (critical tone) is equiprobable with other tones. The corrected MMN is computed as deviant minus critical tones. Furthermore, we assessed working memory capacity to examine its moderating role. In our large sample (N = 49), the evidential strength in support of no effect of visual load was moderate for the oddball MMN (9.09 > BF01 > 3.57) and anecdotal to moderate for the corrected MMN (4.55 > BF01 > 2.17). Also, working memory capacity did not correlate with the visual load effect on the oddball MMN and the corrected MMN. The present findings support the robustness of the auditory frequency MMN to manipulations of crossmodal, visual attention and suggest that this relationship is not moderated by working memory capacity.

Formation and decay of auditory short-term memory in the macaque monkey

Echoic memory (EM) is a short-lived, precategorical, and passive form of auditory short-term memory (STM). A key hallmark of EM is its rapid exponential decay with a time constant between 1 and 2 s. It is not clear whether auditory STM in the rhesus, an important model system, shares this rapid exponential decay. To resolve this shortcoming, two rhesus macaques were trained to perform a delayed frequency discrimination task. Discriminability of delayed tones was measured as a function of retention duration and the number of times the standard had been repeated before the target. Like in the human, our results show a rapid decline of discriminability with retention duration. In addition, the results suggest a gradual strengthening of discriminability with repetition number. Model-based analyses suggest the presence of two components of auditory STM: a short-lived component with a time constant on the order of 550 ms that most likely corresponds to EM and a more stable memory trace with time constants on the order of 10 s that strengthens with repetition and most likely corresponds to auditory recognition memory. NEW & NOTEWORTHY This is the first detailed quantification of the rapid temporal dynamics of auditory short-term memory in the rhesus. Much of the auditory information in short-term memory is lost within the first couple of seconds. Repeated presentations of a tone strengthen its encoding into short-term memory. Model-based analyses suggest two distinct components: an echoic memory homolog that mediates the rapid decay and a more stable but less detail-rich component that mediates strengthening of the trace with repetition.

A Comparison of Auditory Oddball Responses in Dorsolateral Prefrontal Cortex, Basolateral Amygdala, and Auditory Cortex of Macaque

The mismatch negativity (MMN) is an ERP component seen in response to unexpected "novel" stimuli, such as in an auditory oddball task. The MMN is of wide interest and application, but the neural responses that generate it are poorly understood. This is in part due to differences in design and focus between animal and human oddball paradigms. For example, one of the main explanatory models, the "predictive error hypothesis", posits differences in timing and selectivity between signals carried in auditory and prefrontal cortex (PFC). However, these predictions have not been fully tested because (1) noninvasive techniques used in humans lack the combined spatial and temporal precision necessary for these comparisons and (2) single-neuron studies in animal models, which combine necessary spatial and temporal precision, have not focused on higher order contributions to novelty signals. In addition, accounts of the MMN traditionally do not address contributions from subcortical areas known to be involved in novelty detection, such as the amygdala. To better constrain hypotheses and to address methodological gaps between human and animal studies, we recorded single neuron activity from the auditory cortex, dorsolateral PFC, and basolateral amygdala of two macaque monkeys during an auditory oddball paradigm modeled after that used in humans. Consistent with predictions of the predictive error hypothesis, novelty signals in PFC were generally later than in auditory cortex and were abstracted from stimulus-specific effects seen in auditory cortex. However, we found signals in amygdala that were comparable in magnitude and timing to those in PFC, and both prefrontal and amygdala signals were generally much weaker than those in auditory cortex. These observations place useful quantitative constraints on putative generators of the auditory oddball-based MMN and additionally indicate that there are subcortical areas, such as the amygdala, that may be involved in novelty detection in an auditory oddball paradigm.

The Neuronal Basis of Predictive Coding Along the Auditory Pathway: From the Subcortical Roots to Cortical Deviance Detection

In this review, we attempt to integrate the empirical evidence regarding stimulus-specific adaptation (SSA) and mismatch negativity (MMN) under a predictive coding perspective (also known as Bayesian or hierarchical-inference model). We propose a renewed methodology for SSA study, which enables a further decomposition of deviance detection into repetition suppression and prediction error, thanks to the use of two controls previously introduced in MMN research: the many-standards and the cascade sequences. Focusing on data obtained with cellular recordings, we explain how deviance detection and prediction error are generated throughout hierarchical levels of processing, following two vectors of increasing computational complexity and abstraction along the auditory neuraxis: from subcortical toward cortical stations and from lemniscal toward nonlemniscal divisions. Then, we delve into the particular characteristics and contributions of subcortical and cortical structures to this generative mechanism of hierarchical inference, analyzing what is known about the role of neuromodulation and local microcircuitry in the emergence of mismatch signals. Finally, we describe how SSA and MMN are occurring at similar time frame and cortical locations, and both are affected by the manipulation of N-methyl- D-aspartate receptors. We conclude that there is enough empirical evidence to consider SSA and MMN, respectively, as the microscopic and macroscopic manifestations of the same physiological mechanism of deviance detection in the auditory cortex. Hence, the development of a common theoretical framework for SSA and MMN is all the more recommendable for future studies. In this regard, we suggest a shared nomenclature based on the predictive coding interpretation of deviance detection.

Cognitive neurophysiology: Event-related potentials

Event-related potentials (ERPs) are one of the most commonly used tools to assess cognitive processing with a high temporal resolution. We provide an updated view of the cortical origins of evoked responses and discuss potential mechanisms contributing to ERP generation. In particular, we focus on the relationship between evoked and ongoing oscillatory activity and discuss the differences between ERPs and cortical activation as indexed by high-frequency activity in human intracranial electroencephalography (EEG). We highlight several possibilities for how ERPs can precisely index human perception and behavior in nontraditional approaches, such as neuronal entrainment through steady-state evoked potentials, multivariate decoding, and cross-frequency correlations. We argue that analyses of time-locked responses are beneficial to assess nonlinear and nonsinusoidal neuronal activity on a fine-grained temporal scale, since analyses in the time domain are less susceptible to artifacts than spectral decomposition techniques. Taken together, the current review provides a state-of-the-art overview of ERPs and their application in cognitive and clinical neurophysiology.

Neuronal phase consistency tracks dynamic changes in acoustic spectral regularity

The brain parses the auditory environment into distinct sounds by identifying those acoustic features in the environment that have common relationships (e.g., spectral regularities) with one another and then grouping together the neuronal representations of these features. Although there is a large literature that tests how the brain tracks spectral regularities that are predictable, it is not known how the auditory system tracks spectral regularities that are not predictable and that change dynamically over time. Furthermore, the contribution of brain regions downstream of the auditory cortex to the coding of spectral regularity is unknown. Here, we addressed these two issues by recording electrocorticographic activity, while human patients listened to tone-burst sequences with dynamically varying spectral regularities, and identified potential neuronal mechanisms of the analysis of spectral regularities throughout the brain. We found that the degree of oscillatory stimulus phase consistency (PC) in multiple neuronal-frequency bands tracked spectral regularity. In particular, PC in the delta-frequency band seemed to be the best indicator of spectral regularity. We also found that these regularity representations existed in multiple regions throughout cortex. This widespread reliable modulation in PC - both in neuronal-frequency space and in cortical space - suggests that phase-based modulations may be a general mechanism for tracking regularity in the auditory system specifically and other sensory systems more generally. Our findings also support a general role for the delta-frequency band in processing the regularity of auditory stimuli.

Cascade and no-repetition rules are comparable controls for the auditory frequency mismatch negativity in oddball tasks

The mismatch negativity (MMN) has been widely studied with oddball tasks to index processing of unexpected auditory change. The MMN is computed as the difference of deviant minus standard and is used to capture the pattern violation by the deviant. However, this oddball MMN is confounded because the deviant differs physically from the standard and is presented less often. To improve measurement, the same tone as the deviant is presented in a separate condition. This control tone is equiprobable with other tones and is used to compute a corrected MMN (deviant minus control). Typically, the tones are in random order except that consecutive tones are not identical (no-repetition rule). In contrast, a recent study on frequency MMN presented tones in a regular up-and-down sequence (cascade rule). If the cascade rule is detected more easily than the no-repetition rule, there should be a lower risk of a confounding MMN within the cascade condition. However, in previous research, the cascade and no-repetition conditions differed not only in the regularity of the tone sequence but also in number of tones, frequency range, and proportion of tones. We controlled for these differences to isolate effects of regularity in the tone sequence. Results of our preregistered analyses provided moderate evidence (BF₀₁ >6) that the corrected MMN did not differ between cascade and no-repetition conditions. These findings imply that no-repetition and cascade rules are processed similarly and that the no-repetition condition provides an adequate control in frequency MMN.

Auditory Predictive Coding across Awareness States under Anesthesia: An Intracranial Electrophysiology Study

The systems-level mechanisms underlying loss of consciousness (LOC) under anesthesia remain unclear. General anesthetics suppress sensory responses within higher-order cortex and feedback connections, both critical elements of predictive coding hypotheses of conscious perception. Responses to auditory novelty may offer promise as biomarkers for consciousness. This study examined anesthesia-induced changes in auditory novelty responses over short (local deviant [LD]) and long (global deviant [GD]) time scales, envisioned to engage preattentive and conscious levels of processing, respectively. Electrocorticographic recordings were obtained in human neurosurgical patients (3 male, 3 female) from four hierarchical processing levels: core auditory cortex, non-core auditory cortex, auditory-related, and PFC. Stimuli were vowel patterns incorporating deviants within and across stimuli (LD and GD). Subjects were presented with stimuli while awake, and during sedation (responsive) and following LOC (unresponsive) under propofol anesthesia. LD and GD effects were assayed as the averaged evoked potential and high gamma (70-150 Hz) activity. In the awake state, LD and GD effects were present in all recorded regions, with averaged evoked potential effects more broadly distributed than high gamma activity. Under sedation, LD effects were preserved in all regions, except PFC. LOC was accompanied by loss of LD effects outside of auditory cortex. By contrast, GD effects were markedly suppressed under sedation in all regions and were absent following LOC. Thus, although the presence of GD effects is indicative of being awake, its absence is not indicative of LOC. Loss of LD effects in higher-order cortical areas may constitute an alternative biomarker of LOC.SIGNIFICANCE STATEMENT Development of a biomarker that indexes changes in the brain upon loss of consciousness (LOC) under general anesthesia has broad implications for elucidating the neural basis of awareness and clinical relevance to mechanisms of sleep, coma, and disorders of consciousness. Using intracranial recordings from neurosurgery patients, we investigated changes in the activation of cortical networks involved in auditory novelty detection over short (local deviance) and long (global deviance) time scales associated with sedation and LOC under propofol anesthesia. Our results indicate that, whereas the presence of global deviance effects can index awareness, their loss cannot serve as a biomarker for LOC. The dramatic reduction of local deviance effects in areas beyond auditory cortex may constitute an alternative biomarker of LOC.

A comprehensive analysis of auditory event-related potentials and network oscillations in an NMDA receptor antagonist mouse model using a novel wireless recording technology

There is growing evidence that impaired sensory processing significantly contributes to cognitive deficits found in schizophrenia. Electroencephalography (EEG) has become an important preclinical and clinical technique to investigate the underlying mechanisms of neurophysiological dysfunctions in psychiatric disorders. Patients with schizophrenia show marked deficits in auditory event-related potentials (ERP), the detection of deviant auditory stimuli (mismatch negativity, MMN), the generation and synchronization of 40 Hz gamma oscillations in response to steady-state auditory stimulation (ASSR) and reduced auditory-evoked oscillation in the gamma range. Due to a novel data-logging technology (Neurologger, TSE Systems), it is now possible to record wireless EEG data in awake, free-moving small rodents without any restrictions due to size of the device or attached cables. Recently, a new version of the Neurologger was released with improved performance to record time-locked event-related EEG signals. In this study, we were able to show in mice that pharmacological intervention with the NMDA receptor antagonists Ketamine and MK-801 can impair a comprehensive selection of EEG/ERP readouts (ERP N1 amplitude, 40 Hz ASSR, basal and evoked gamma oscillation, MMN) and therefore mimic the EEG deficits observed in patients with schizophrenia. Our data support the translational value of NMDA receptor antagonists as a model for preclinical evaluation of sensory processing deficits relevant to schizophrenia. Further, the new Neurologger system is a suitable device for wireless recording of clinically relevant EEG biomarkers in freely moving mice and a robust translational tool to investigate novel therapeutic approaches regarding sensory processing deficits related to psychiatric disorders such as schizophrenia.

Automatic Change Detection in Older and Younger Women: A Visual Mismatch Negativity Study

BACKGROUND

In comparison to controlled (attentional) processing, relatively little is known about the age-related changes of the earlier (preattentive) processes. An event-related potential (ERP) index of preattentive (automatic) visual processing, the visual mismatch negativity (vMMN) is a good candidate for analyzing age-related differences in the automatic processing of visual events.

OBJECTIVE

So far results concerning age-related changes in vMMN have been equivocal. Our aim was to develop a method resulting in a reliable vMMN in a paradigm short enough to use in the applied field.

METHODS

We investigated an older (mean age: 66.4 years, n = 15) and a younger (mean age: 22.4 years, n = 15) group of healthy women. ERPs were obtained for checkerboard onset patterns in a passive oddball condition (during which participants performed a tracking task). One of the checkerboards was frequent (standard; p = 0.8), and the other was rare (deviant; p = 0.2).

RESULTS

vMMN emerged over posterior locations in the latency range of 100-300 ms in both age groups. The amplitude of the earlier part of the vMMN was similar in the older and the younger participants, but latency was longer in the older group. The later part of the vMMN was slightly diminished in the elderly.

CONCLUSION

Automatic detection of violated sequential regularities, reflected by the vMMN, emerged in the two age groups (earlier vMMN). However, detection of stimulus change, a preattentive visual process delayed in the elderly, and identification of the specific change was compromised in the older participants.

Electrophysiological and Behavioral Outcomes of Berard Auditory Integration Training (AIT) in Children with Autism Spectrum Disorder

Autism is a pervasive developmental disorder of childhood characterized by deficits in social interaction, language, and stereotyped behaviors along with a restricted range of interests. It is further marked by an inability to perceive and respond to social and emotional signals in a typical manner. This might due to the functional disconnectivity of networks important for specific aspects of social cognition and behavioral control resulting in deficits of sensory information integration. According to several recent theories sensory processing and integration abnormalities may play an important role in impairments of perception, cognition, and behavior in individuals with autism. Among these sensory abnormalities, auditory perception distortion may contribute to many typical symptoms of autism. The present study used Berard's technique of auditory integration training (AIT) to improve sound integration in children with autism. It also aimed to understand the abnormal neural and functional mechanisms underlying sound processing distortion in autism by incorporating behavioral, psychophysiological and neurophysiological outcomes. It was proposed that exposure to twenty 30-min AIT sessions (total 10 h of training) would result in improved behavioral evaluation scores, improve profile of cardiorespiratory activity, and positively affect both early [N1, mismatch negativity (MMN)] and late (P3) components of evoked potentials in auditory oddball task. Eighteen children with autism spectrum disorder (ASD) participated in the study. A group of 16 typically developing children served as a contrast group in the auditory oddball task. Autonomic outcomes of the study reflected a linear increase of heart rate variability measures and respiration rate. Comparison of evoked potential characteristics of children with ASD versus typically developing children revealed several group difference findings, more specifically, a delayed latency of N1 to rare and frequent stimuli, larger MMN; higher P3a to frequent stimuli, and at the same time delayed latency of P3b to rare stimuli in the autism group. Post-AIT changes in evoked potentials could be summarized as a decreased magnitude of N1 to rare stimuli, marginally lower negativity of MMN, and decrease of the P3a to frequent stimuli along with delayed latency and higher amplitude of the P3b to the rare stimuli. These evoked potential changes following completion of Berard AIT course are in a positive direction, making them less distinct from those recorded in age-matched group of typical children, thus could be considered as changes towards normalization. Parental questionnaires clearly demonstrated improvements in behavioral symptoms such as irritability, hyperactivity, repetitive behaviors and other important behavioral domains. The results of the study propose that more controlled research is necessary to document behavioral and psychophysiological changes resulting from Berard AIT and to provide explanation of the neural mechanisms of how auditory integration training may affect behavior and psychophysiological responses of children with ASD.

Auditory Memory Decay as Reflected by a New Mismatch Negativity Score Is Associated with Episodic Memory in Older Adults at Risk of Dementia

The auditory mismatch negativity (MMN) is an event-related potential (ERP) peaking about 100–250 ms after the onset of a deviant tone in a sequence of identical (standard) tones. Depending on the interstimulus interval (ISI) between standard and deviant tones, the MMN is suitable to investigate the pre-attentive auditory discrimination ability (short ISIs, ≤ 2 s) as well as the pre-attentive auditory memory trace (long ISIs, >2 s). However, current results regarding the MMN as an index for mild cognitive impairment (MCI) and dementia are mixed, especially after short ISIs: while the majority of studies report positive associations between the MMN and cognition, others fail to find such relationships. To elucidate these so far inconsistent results, we investigated the validity of the MMN as an index for cognitive impairment exploring the associations between different MMN indices and cognitive performance, more specifically with episodic memory performance which is among the most affected cognitive domains in the course of Alzheimer’s dementia (AD), at baseline and at a 5-year-follow-up. We assessed the amplitude of the MMN for short ISI (stimulus onset asynchrony, SOA = 0.05 s) and for long ISI (3 s) in a neuropsychologically well-characterized cohort of older adults at risk of dementia (subjective memory impairment, amnestic and non-amnestic MCI; n = 57). Furthermore, we created a novel difference score (ΔMMN), defined as the difference between MMNs to short and to long ISI, as a measure to assess the decay of the auditory memory trace, higher values indicating less decay. ΔMMN and MMN amplitude after long ISI, but not the MMN amplitude after short ISI, was associated with episodic memory at baseline (β = 0.38, p = 0.003; β = −0.27, p = 0.047, respectively). ΔMMN, but not the MMN for long ISIs, was positively associated with episodic memory performance at the 5-year-follow-up (β = 0.57, p = 0.013). The results suggest that the MMN after long ISI might be suitable as an indicator for the decline in episodic memory and indicate ΔMMN as a potential biomarker for memory impairment in older adults at risk of dementia.