Alterations of mismatch negativity (MMN) in schizophrenia patients with auditory hallucinations experiencing acute exacerbation of illness

Auditory verbal hallucinations (AHs), or hearing 'voices', are one of the hallmark symptoms of patients with schizophrenia. The primary objective of this study was to compare hallucinating schizophrenia patients with respect to differences in deviance detection, as indexed by the auditory mismatch negativity (MMN). Patients were recruited during an acute psychotic episode requiring hospitalization, during which time symptoms of psychosis, including auditory hallucinations, are likely to be at their most severe. MMNs to duration, frequency, gap, intensity and location deviants (as elicited by the 'optimal' multi-feature paradigm) were recorded in 12 acutely ill schizophrenia patients (SZ) with persistent AHs and 15 matched healthy controls (HC). Electrical activity was recorded from 32 scalp electrodes. MMN amplitudes and latencies for each deviant were compared between groups and were correlated with trait (PSYRATS) and state measures of AH severity and Positive and Negative Syndrome Scale (PANSS) ratings in SZs. There were significant group differences for duration, gap, intensity and location MMN amplitudes, such that SZs exhibited reduced MMNs compared to HCs. Additionally, gap MMN amplitudes were correlated with measures of hallucinatory state and frequency of AHs, while location MMN was correlated with perceived location of AHs. In summary, this study corroborates previous research reporting a robust duration MMN deficit in schizophrenia, as well as reporting gap, intensity and location MMN deficits in acutely ill schizophrenia patients with persistent AHs. Additionally, MMN amplitudes were correlated with state and trait measures of AHs. These findings offer further support to previous work suggesting that the presence of auditory hallucinations may make a significant contribution to the widely reported MMN deficits in schizophrenia.     

Reduced late mismatch negativity and auditory sustained potential to rule‐based patterns in schizophrenia

Complex rule‐based auditory processing is abnormal in individuals with long‐term schizophrenia (SZ), as demonstrated by reduced mismatch negativity (MMN) to deviants in rule‐based patterns and reduced auditory sustained potential (ASP) that appears when grouping tones together. Together, this suggests deficits later in the auditory processing hierarchy in Sz. Here, MMN and ASP were elicited by deviations from a complex zig‐zag pitch pattern that cannot be predicted by simple linear rules. Twenty‐seven SZ and 26 matched healthy controls (HC) participated. Frequent groups of patterns contained eight tones that zig‐zagged in a two‐up one‐down pitch‐based paradigm. There were two deviant patterns: the final tone was either higher in pitch than expected (creating a jump in pitch) or was repeated. Simple MMN to pitch‐deviants among repetitive tones was measured for comparison. Sz exhibited a smaller pitch MMN compared to HC as expected. HC produced a late MMN in response to the repeat and jump‐deviant and a larger ASP to the standard group of tones, all of which were significantly blunted in SZ. In Sz, the amplitude of the late complex MMN was related to neuropsychological functioning, whereas ASP was not. ASP and late MMN did not significantly correlate in HC or in Sz, suggesting that they are not dependent on one another and may originate within distinct processing streams. Together, this suggests multiple deficits later in the auditory sensory‐perceptual hierarchy in Sz, with impairments evident in both segmentation and deviance detection abilities.     

The right profile: mismatch negativity in schizophrenia with and without auditory hallucinations as measured by a multi-feature paradigm.

ObjectiveTo examine pre-attentive acoustic change detection in schizophrenia patients with and without auditory hallucinations via mismatch negativity (MMN) extracted from a multi-feature paradigm.MethodsThis study examined the electroencephalograph (EEG)-derived MMN, recorded across 32 sites, in 12 hallucinating patients (HPs) with schizophrenia, 12 non-hallucinating patients (NPs) with schizophrenia and 12 healthy controls (HCs). MMN was recorded in response to a multi-feature MMN paradigm [Näätänen, R., et al., 2004. The mismatch negativity (MMN): towards the optimal paradigm. Clin. Neurophys. 115, 140–144] which employs frequency, duration, intensity, location and gap deviants. Differences in source localization were probed using standardized low resolution brain electromagnetic tomography (sLORETA).ResultsHPs showed significantly smaller MMNs to duration deviants compared to HCs and NPs, as well as smaller MMNs to intensity deviants compared to HCs. Regionalized differences between HCs and each of the patient groups were observed in response to frequency deviants. There were no significant group effects for location or gap deviants, or for MMN latency. Source localization using sLORETA showed no significant differences in MMN generator location across groups for any of the deviant stimuli.ConclusionsThe often-reported robust MMN deficit to duration deviants may be specific to schizophrenia patients afflicted with auditory hallucinations. Furthermore, by using symptom-specific groups, novel deficits of pre-attentive auditory processing, such as that observed to intensity deviants in HPs, may be revealed.SignificanceThe differential responding observed between both groups of patients with schizophrenia has implications for automatic processing within the auditory cortex of hallucinating patients and suggests that care must be taken when recruiting participants in studies involving schizophrenia to ensure consistent, replicable results.     

Impaired mismatch negativity generation in prodromal subjects and patients with schizophrenia

BACKGROUND: Mismatch negativity (MMN) specifically the response to tone duration deviants has consistently been shown to be reduced in schizophrenia suggesting dysfunction in auditory sensory memory. As part of a multidimensional approach to the early recognition of psychosis, MMN was investigated as a possible risk factor for later development of psychosis in subjects with a prodromal syndrome. Forty-three prodromal subjects, 31 neuroleptic-free inpatients with schizophrenia and 33 healthy controls were studied. A prodromal state was defined by a cluster 'Cognitive Disturbances' as defined by the 'Bonn Scale for the Assessment of Basic Symptoms' (BSABS), which was found highly predictive of first-episode schizophrenia. To elicit MMN, a three-tone auditory oddball paradigm with 10% 'duration deviants' and 10% 'frequency deviants' was used. RESULTS: MMN amplitudes to tone duration deviants were significantly reduced in the patients with schizophrenia compared to controls. The putatively prodromal subjects also showed a slight, though non-significant reduction of the MMN amplitude that was intermediate between normal controls and patients with schizophrenia, and with a larger within-group variance. CONCLUSION: These results support the view that abnormalities in temporal processing are particularly pronounced in patients with schizophrenia. Prodromal subjects are a heterogeneous group with regard to outcome and time until transition to a first psychotic episode. Follow-up of these putatively prodromal subjects will show whether MMN amplitudes further reduce over time in those developing psychosis and if a reduction is state-dependent.     

Duration mismatch negativity in biological relatives of patients with schizophrenia spectrum disorders.

BACKGROUND: One of the most consistent findings in schizophrenia research over the past decade is a reduction in the amplitude of an auditory event-related brain potential known as mismatch negativity (MMN), which is generated whenever a deviant sound occurs in a background of repetitive auditory stimulation. The reduced amplitude of MMN in schizophrenia was first observed for deviant sounds that differ in duration relative to background standard sounds, and similar findings have been observed for sounds that are deviant in frequency. The aim of this study was to determine whether first-degree relatives of schizophrenia patients show a similar reduction in MMN amplitude to duration deviants. METHODS: We measured MMN to duration increments (deviants 100 msec vs. standards 50 msec) in 22 medicated patients with a diagnosis in the schizophrenia spectrum, 17 individuals who were first-degree unaffected relatives of patients, and 21 healthy control subjects. RESULTS: Mismatch negativity amplitude was reduced in patients and relatives compared with control subjects. There were no significant differences between patients and relatives. In contrast, the subsequent positive component, P3a, was larger in relatives compared with patients. CONCLUSIONS: These findings suggest that a reduced MMN amplitude may be an endophenotype marker of the predisposition to schizophrenia.     

MMN responsivity to manipulations of frequency and duration deviants in chronic, clozapine-treated schizophrenia patients

Event-related potential (ERP) probing of abnormal sensory processes in schizophrenia with the mismatch negativity (MMN) has shown impairments in auditory change detection, but knowledge of the acoustic features leading to this deficit is incomplete. Changes in the duration and frequency properties of sound stimuli result in diminished MMNs in schizophrenia but it is unclear as to whether this reduced responsiveness is seen with more subtle changes in sound frequency. In a sample of 19 healthy controls and 21 patients with chronic schizophrenia treated with clozapine, MMN was assessed in response to tone frequency changes of 5%, 10% and 20%, and to tone duration changes. Patients exhibited reduced amplitudes and shorter latencies than controls to all frequency changes, and attenuated amplitudes to tone duration increments and decrements. Clozapine dose was related to MMN, with increasing dose being positively associated with frequency-MMN amplitudes (10% ?f, 20% ?f) and negatively associated with the amplitude and latency of duration-MMNs. These data support the well-established findings of auditory sensory abnormality in schizophrenia and underscore the sensitivity of MMN to relatively small auditory change detection deficits that may appear to characterize chronic schizophrenia.     

Auditory lateralization in schizophrenia--mismatch negativity and behavioral evidence of a selective impairment in encoding interaural time cues.

OBJECTIVE: Behavioural evidence suggests that individuals with schizophrenia may exhibit impairment in the encoding of cues to sound location. There are three primary cues used by the auditory system to locate the position of a sound in space: interaural differences in the arrival-time (ITD), phase (IPD), and the loudness (ILD) of the sound at the two ears. The goal in this study was to obtain an electrophysiological index of preattentive detection of change in sound lateralization created by these cues. METHODS: The amplitude of mismatch negativity (MMN) was measured in 18 individuals with schizophrenia and 19 healthy comparison subjects to changes in sound lateralization produced by interaural temporal cues (ITD and IPD) and interaural loudness cues (ILD). Performance was also investigated on a target detection task, where targets were defined by ITD, IPD, or ILD cues. RESULTS: Individuals with schizophrenia had reduced MMN amplitudes and decreased hit rates when deviants were created by interaural temporal cues, but not when loudness cues were used. CONCLUSIONS: Results from both the MMN and behavioural task revealed a selective impairment in the use of temporal cues to sound lateralization in individuals with schizophrenia. SIGNIFICANCE: This finding supports previous research that suggests impairment in the encoding of the temporal information in schizophrenia.     

Duration and frequency mismatch negativity in schizophrenia.

OBJECTIVES: The aim of the present study was to elucidate the reasons for apparent inconsistencies in the schizophrenia literature with respect to the mismatch negativity (MMN) waveform of the event-related potential (ERP). While most previous research has shown that MMN is reduced in schizophrenia, there are a small number of studies reporting that frequency MMN is not reduced. METHODS: We recorded ERPs to auditory stimuli with different frequencies and durations from patients with schizophrenia (N = 14) and control subjects (N = 17) of similar age and sex. MMNs to small but discriminable frequency deviants were contrasted with large frequency deviants and duration deviants. RESULTS: Only the MMN to duration deviants was significantly reduced in patients, although there was evidence of a similar trend for large frequency deviants. CONCLUSIONS: The results together with a review of the frequency MMN literature suggest that there are 3 variables which are important in determining whether patients exhibit a reduced MMN to frequency deviants: deviant probability, degree of deviance and interstimulus interval. The results also indicated that patients with schizophrenia may have particular deficits in processing the temporal properties of auditory stimuli. This finding has implications for the pathophysiology of the disorder as time-dependent processing is reliant on the integrity of an extensive network of brain areas consisting of auditory cortex, areas of pre-frontal cortex, the basal ganglia and cerebellum.     

Mismatch negativity predicts psychotic experiences induced by NMDA receptor antagonist in healthy volunteers.

BACKGROUND: Previous studies indicate that mismatch negativity (MMN)-a preattentive auditory event-related potential (ERP)-depends on NMDA receptor (NMDAR) functioning. To explore if the strength of MMN generation reflects the functional condition of the NMDAR system in healthy volunteers, we analyzed correlations between MMN recorded before drug administration and subsequent responses to the NMDAR antagonist ketamine or the 5-HT2a agonist psilocybin. METHODS: In two separate studies, MMN was recorded to both frequency and duration deviants prior to administration of ketamine or psilocybin. Behavioral and subjective effects of ketamine and psilocybin were assessed with the Brief Psychiatric Rating Scale and the OAV Scale-a rating scale developed to measure altered states of consciousness. Correlations between ERP amplitudes (MMN, N1, and P2) and drug-induced effects were calculated in each study group and compared between them. RESULTS: Smaller MMN to both pitch and duration deviants was significantly correlated to stronger effects during ketamine, but not psilocybin administration. No significant correlations were observed for N1 and P2. CONCLUSIONS: Smaller MMN indicates a NMDAR system that is more vulnerable to disruption by the NMDAR antagonist ketamine. MMN generation appears to index the functional state of NMDAR-mediated neurotransmission even in subjects who do not demonstrate any psychopathology.     

Changes in the duration and frequency of deviant stimuli engender different mismatch negativity patterns in temporal lobe epilepsy

Mismatch negativity (MMN) is an event-related potential (ERP) component that reflects preattentive sensory memory functions. Previous research revealed that MMN is generated by distinct sources in the frontal and temporal lobes. Event-related potential abnormalities have been shown in the vicinity of seizure foci in epilepsy. Additionally, no published study has investigated the MMN in response to variations in both frequency and duration deviants in patients with temporal lobe epilepsy (TLE). The aims of this study were to compare MMN changes between the frontocentral sites and the mastoid sites and to compare MMNs related to deviant stimuli with different durations and frequencies in patients with TLE. We recorded MMNs elicited by duration and frequency changes of deviant stimuli from 15 patients with TLE and 15 healthy control subjects. We found that mean MMN amplitudes related to duration deviants were lower in patients with TLE at the mastoid sites relative to controls, whereas the MMN amplitudes at the frontocentral sites did not differ between the two groups. There were no MMN differences related to frequency deviants between TLE subjects and controls at the frontocentral sites or the mastoid sites. Mismatch negativity parameters related to duration deviants did not correlate with those related to deviant frequencies in the group with TLE. The present findings suggest selective impairments among multiple mismatch generators in TLE and suggest that processing of temporal information of auditory stimuli is selectively disturbed in TLE. Changes in MMN amplitudes related to duration deviants at the mastoid sites may represent deficits in time-dependent processing in TLE.     

Emotional MMN: Anxiety and heart rate correlate with the ERP signature for auditory change detection

ObjectivePrevious work established the mismatch negativity (MMN) as a correlate of pre-attentive auditory change detection. The present study aimed at investigating the relationship between the MMN and emotional processes associated with the detection of change.MethodsTo this end, we assessed state anxiety with a questionnaire and subsequently recorded the electroencephalogram (EEG) and heart rate while participants watched a silent movie and listened to a task-irrelevant auditory oddball sequence. The oddball sequence comprised meaningless syllables of which some were deviants spoken with an angry or neutral voice.ResultsThe MMN to angry voice deviants was larger than that to neutral deviants and correlated positively with ensuing heart rate acceleration. Additionally, both the MMN and heart rate acceleration to angry voice deviants were increased with increasing state anxiety. A similar effect for neutral voice deviants was non-significant.ConclusionTaken together, these results suggest that the pre-attentive processing of threat, as reflected by the MMN, is linked to an activation of the sympathetic nervous system. Moreover, this link is more strongly activated in individuals with high state anxiety.SignificanceThus, the MMN may be used as a marker for an individual’s state dependent sensitivity to unattended, emotionally relevant change.     

Auditory verbal hallucinations in schizophrenia correlate with P50 gating

ObjectiveWhile auditory verbal hallucinations (AVHs) are a common symptom of schizophrenia, the underlying mechanisms behind these perceptual anomalies and their effects on auditory processing are not fully understood. Patients suffering from schizophrenia have been shown to exhibit impaired sensory gating of acoustic stimuli, evidenced by a failure to inhibit the auditory P50 scalp recorded middle latency evoked potential response to the second of two paired auditory “clicks” (S1–S2).MethodsBecause abnormal activation of auditory pathways is associated with a general AVH trait of schizophrenia patients, this study correlated the hallucinatory trait subscale of the Psychotic Symptoms Ratings Scale (PSYRATS) scores of 16 actively hallucinating patients with their P50 responses to S1 and S2 as well as sensory gating indices. P50 gating in patients was also compared to twenty one healthy controls.ResultsControl S1 amplitudes were significantly greater than those of patients. There was a negative correlation between PSYRATS scores and gating difference score as well as with S1 amplitude, and a positive correlation with gating ratio, indicating the global trait of hallucinating schizophrenia patients may be associated with deficiencies in the processing of auditory stimuli. No significant correlation was found when the same analysis was applied to a state-dependent hallucination ratings scale.SignificanceResults suggest the relationship between auditory hallucinations and auditory processing dysfunction measured by P50 response is more trait than state dependent in schizophrenia.     

How specific are deficits in mismatch negativity generation to schizophrenia?

BACKGROUND: Mismatch negativity (MMN) is an auditory event-related potential that provides an index of auditory sensory memory. Deficits in MMN generation have been repeatedly demonstrated in chronic schizophrenia. Their specificity to schizophrenia has not been established. METHODS: Mismatch negativity to both duration and frequency deviants was investigated in gender- and age-matched patients with schizophrenia or schizoaffective disorder (n = 26), bipolar disorder (n = 16), or major depression (n = 22) and healthy control subjects (n = 25). RESULTS: Only patients with schizophrenia demonstrated significantly smaller mean MMN than did healthy control subjects. Detailed analyses showed significantly smaller MMN to both duration and frequency deviants in patients with schizophrenia than in healthy control subjects; however, the reduction of frequency MMN in patients with schizophrenia was not significant in the comparison across all groups. Mismatch negativity topography did not differ among groups. No consistent correlations with clinical, psychopathologic, or treatment variables were observed. CONCLUSIONS: Mismatch negativity deficits, and by extension deficits in early cortical auditory information processing, appear to be specific to schizophrenia. Animal and human studies implicate dysfunctional N-methyl-D-aspartate receptor functioning in MMN deficits. Thus MMN deficits may become a useful endophenotype to investigate the genetic underpinnings of schizophrenia, particularly with regard to the N-methyl-D-aspartate receptor.     

Cortical interactions during the experience of auditory verbal hallucinations

Auditory verbal hallucinations (AVHs), the perception of voices in the absence of auditory stimuli, are common and distressing symptoms reported by 50%-80% of patients with schizophrenia. However, the results in a number of imaging and electrophysiological studies on the origins of AVH are not consistent, and the underlying pathophysiology remains unclear. The authors enrolled a group of schizophrenia patients and normal-control subjects, age 18-45 years. Two patient groups participated in the study; 1) a group of 8 patients with drug-resistant spontaneous AVHs; and 2) a group of 7 patients whose AVHs were successfully controlled with neuroleptic medication; along with 16 normal-control subjects. The entire sample had EEG recording done, with the AVH group told to press a button when they experienced a hallucination, and the other two groups randomly told when to press the button. In the AVH group, hallucinations were longer in the "eyes-closed" than "eyes-open" condition. There was spreading phase-coupling in the AVH group, intra- and inter-hemispherically, at left and right frontal and temporal areas, under both eyes-closed and eyes-open condition, during the experience of AVH. There was a statistically significant increase of α-band frequency-specific synchrony maximum values in the AVH group. AVHs are considered to be complex features, and, as such, they reflect abnormal functional connectivity in multiple related regions in both intra- and inter-hemispherical brain sites, primarily defined by phase-integration.     

Domain-specific suppression of auditory mismatch negativity with transcranial direct current stimulation

ObjectiveTo evaluate the influence of frontal transcranial direct current stimulation (tDCS) on auditory mismatch negativity (MMN).MethodsMMN is an event related potential calculated by subtracting the amplitude of the evoked potentials in response to a “standard” stimulus from the evoked potentials produced by a rare “oddball” stimulus. Here we assessed the influence of anodal tDCS, cathodal tDCS or sham stimulation delivered over the right inferior frontal cortex on MMN in response to duration and frequency auditory deviants in 10 healthy subjects.ResultsMMN to frequency deviants was significantly reduced after anodal tDCS compared with sham or cathodal stimulation which did not change MMN to frequency deviants. Neither anodal nor cathodal tDCS had any effect on MMN to duration deviants.ConclusionsNon-invasive brain stimulation with tDCS can influence MMN. The differing networks known to be activated by duration and frequency deviants could account for the differential effect of tDCS on duration and frequency MMN.SignificanceNon-invasive brain stimulation could be a useful method to manipulate MMN for experimental purposes.     

Cerebral activity associated with auditory verbal hallucinations: a functional magnetic resonance imaging case study

Among the many theories that have been advanced to explain the mechanism by which auditory verbal hallucinations (AVH) arise, 2 that have received a degree of empirical support are: the hypothesis that AVHs arise from misinterpreted inner speech and the proposal that they arise from aberrant activation of the primary auditory cortex. To test these hypotheses, we were fortunate to be able to study the interesting and rare case of a woman with schizophrenia who experienced continuous AVH which disappeared when she listened to loud external speech. Functional magnetic resonance imaging (fMRI) was used to measure the patient's brain activity in the temporal and inferior frontal regions during the AVHs and while the she was listening to external speech. The brain activity of a matched control subject was also recorded under the same experimental conditions. AVHs were associated with increased metabolic activity in the left primary auditory cortex and the right middle temporal gyrus. Our results suggest a possible interaction between these areas during AVHs and also that the hypotheses of defective internal monitoring and aberrant activation are not mutually exclusive. Potential limitations to the generalization of our results are discussed.     

Mismatch negativity in schizophrenia: a meta-analysis

BACKGROUND: Mismatch negativity (MMN) is an auditory event-related potential that provides an index of automatic context-dependent information processing and auditory sensory memory. Many studies have reported abnormalities in the generation of MMN in schizophrenia. The objective of this study was to assess the magnitude of this deficit and associated factors. METHOD: Studies of MMN in schizophrenia were identified and included in a meta-analysis to estimate the mean effect size. Effects of duration of illness, gender ratio, age of patients, type of MMN (duration versus frequency MMN) and characteristics of the test paradigms (deviant probability, magnitude of standard-deviant difference) on effect size were assessed. RESULTS: Of 62 identified studies 32 met our inclusion criteria. The mean effect size was 0.99 (95% confidence intervals: 0.79, 1.29). Overall, no specific factor was significantly associated with MMN deficits, although MMN to stimuli differing in duration appeared more impaired in schizophrenia than MMN to frequency deviants. In addition, effect sizes of frequency MMN were significantly correlated with duration of illness. CONCLUSIONS: MMN deficits are a robust feature in chronic schizophrenia and indicate abnormalities in automatic context-dependent auditory information processing and auditory sensory memory in these patients. Reports of normal MMN in first-episode schizophrenia and the association of deficits in frequency MMN with illness duration suggest that MMN may index ongoing neuropathological changes in the auditory cortex in schizophrenia.     

Intermodal selective attention. I. Effects on event-related potentials to lateralized auditory and visual stimuli.

The effects of intermodal selective attention on event-related brain potentials (ERPs) were examined in 2 experiments. In experiment 1, auditory ERPs were compared (1) when subjects responded to easy and difficult-to-detect target tones in sequences of tone bursts; and (2) when they ignored the same auditory sequences and played a demanding video game. In experiment 2, auditory ERPs to tone bursts and visual ERPs to vertical line gratings were compared as subjects responded to difficult-to-detect targets in one modality or the other. Attention to auditory stimuli resulted in biphasic enhancements in auditory ERPs, the Nda (negative auditory difference wave, latency 120-160 msec) and the Pda (positive auditory difference wave, latency 200-240 msec) waves. These had longer latencies and somewhat different scalp distributions than N1 and P2 components evoked by non-attended tones. The Nda and Pda could be contrasted with the monophasic processing negativities typically found in dichotic selective attention tasks. Nda amplitudes were larger for difficult-to-detect targets (closely resembling standards) than for standards themselves, but no Ndas were recorded to highly deviant targets. Deviant auditory stimuli evoked mismatch negativities (MMNs) that persisted during visual attention. MMN amplitudes to difficult-to-detect deviants were enlarged with attention, but no change was found in MMN amplitudes to easy-to-detect deviants. In experiment 2 intermodal attention was associated with biphasic changes in visual ERPs over the posterior scalp: the occipital Pdv (100-130 msec), and contralateral-temporal Ndv (120-320 msec) deflections. Deviant visual stimuli also elicited mismatch negativity/N2b components, largest over the inferotemporal cortex contralateral to the stimulated visual field. Like the auditory MMN, the MMN increased in amplitude with attention, but it was also evident during attend auditory conditions. The results suggest that sustained, intermodal attention depends primarily in processing modulations in modality-specific cortex. We found no evidence of the participation of modality non-specific cortex. This excludes the possibility that intermodal attention depends on a single, supramodal attention system. The relatively long latency of intermodal effects suggests that they may depend on the reafferent (top down) modulation, and do not index "template matching" operations.     

Discrimination of auditory motion patterns: The mismatch negativity study

The aim of the present study is to test whether mismatch negativity (MMN) response can be elicited by changes in auditory motion dynamics. The discrimination of auditory motion patterns was investigated using psychophysical and electrophysiological methods in the same group of subjects. Auditory event-related potentials (ERP) were recorded for stationary midline noises and moving noises shifting to the left/right from the head midline. Two patterns of auditory motion were used with gradual (Motion) and stepwise (Step) movements which started and ended at the same loci. Auditory motion was produced by linear and abrupt changes of interaural time differences (ITD) in binaurally presented stimuli. In Experiment 1, ERPs were recorded for stationary midline standards and for Motion and Step deviants. It was found that Step deviants result in larger MMN amplitudes than Motion deviants with the same distance travelled, which implies that information contained in the stimulus midportion could be involved in the processing of the auditory motion. The threshold ITD values for the detection of Step and Motion stimuli displacement obtained during psychoacoustic tests were greater than the minimal ITD changes which elicited significant MMN. Experiment 2 demonstrated that Step deviants elicited significant MMNs in the context of Motion standards, although these stimuli could not be discriminated behaviourally. MMNs elicited by Step deviants in different acoustic contexts are discussed from the viewpoint of different brain processes underlying the discrimination of the abrupt ITD change. These results suggest that the early cortical mechanism of auditory motion processing reflected by MMN could not be considered as a spatial discriminator of the onset/offset stimulus positions, that is, a simple onset-offset detector. Combining psychoacoustic data with MMN results we may conclude that motion discrimination in auditory system might be better at the preattentive level.     

Hallucination‐ and speech‐specific hypercoupling in frontotemporal auditory and language networks in schizophrenia using combined task‐based fMRI data: An fBIRN study

Hypercoupling of activity in speech‐perception‐specific brain networks has been proposed to play a role in the generation of auditory‐verbal hallucinations (AVHs) in schizophrenia; however, it is unclear whether this hypercoupling extends to nonverbal auditory perception. We investigated this by comparing schizophrenia patients with and without AVHs, and healthy controls, on task‐based functional magnetic resonance imaging (fMRI) data combining verbal speech perception (SP), inner verbal thought generation (VTG), and nonverbal auditory oddball detection (AO). Data from two previously published fMRI studies were simultaneously analyzed using group constrained principal component analysis for fMRI (group fMRI‐CPCA), which allowed for comparison of task‐related functional brain networks across groups and tasks while holding the brain networks under study constant, leading to determination of the degree to which networks are common to verbal and nonverbal perception conditions, and which show coordinated hyperactivity in hallucinations. Three functional brain networks emerged: (a) auditory‐motor, (b) language processing, and (c) default‐mode (DMN) networks. Combining the AO and sentence tasks allowed the auditory‐motor and language networks to separately emerge, whereas they were aggregated when individual tasks were analyzed. AVH patients showed greater coordinated activity (deactivity for DMN regions) than non‐AVH patients during SP in all networks, but this did not extend to VTG or AO. This suggests that the hypercoupling in AVH patients in speech‐perception‐related brain networks is specific to perceived speech, and does not extend to perceived nonspeech or inner verbal thought generation.