Deviance-elicited changes in event-related potentials are attenuated by ketamine in mice

BACKGROUND: People with schizophrenia exhibit reduced ability to detect change in the auditory environment, which has been linked to abnormalities in N-methyl-D-aspartate (NMDA) receptor-mediated glutamate neurotransmission. This ability to detect changes in stimulus qualities can be measured with electroencephalography using auditory event-related potentials (ERPs). For example, reductions in the N100 and mismatch negativity (MMN), in response to pitch deviance, have been proposed as endophenotypes of schizophrenia. This study examines a novel rodent model of impaired pitch deviance detection in mice using the NMDA receptor antagonist ketamine. METHODS: ERPs were recorded from unanesthetized mice during a pitch deviance paradigm prior to and following ketamine administration. First, N40 amplitude was evaluated using stimuli between 4 and 10 kHz to assess the amplitude of responses across the frequency range used. The amplitude and latency of the N40 were analyzed following standard (7 kHz) and deviant (5-9 kHz) stimuli. Additionally, we examined which portions of the ERP are selectively altered by pitch deviance to define possible regions for the mouse MMN. RESULTS: Mice displayed increased N40 amplitude that was followed by a later negative component between 50 and 75 msec in response to deviant stimuli. Both the increased N40 and the late N40 negativity were attenuated by ketamine. Ketamine increased N40 latency for both standard and deviant stimuli alike. CONCLUSIONS: The mouse N40 and a subsequent temporal region have deviance response properties similar to the human N100 and, possibly, MMN. Deviance responses were abolished by ketamine, suggesting that ketamine-induced changes in mice mimic deviance detection deficits in schizophrenia.     

Intracranial identification of an electric frontal-cortex response to auditory stimulus change: a case study

The aim of the present study was to clarify whether ERPs recorded directly from the human frontal cortex contributed to the auditory N1 and mismatch negativity (MMN) elicited by changes in non-phonetic and phonetic sounds. We examined the role of prefrontal cortex in the processing of stimulus repetition and change in a 6-year-old child undergoing presurgical evaluation for epilepsy. EEG was recorded from three bilateral sub-dural electrode strips located over lateral prefrontal areas during unattended auditory stimulation. EEG epochs were averaged to obtain event-related potentials (ERPs) to repeating (standard) tones and to infrequent (deviant) shorter duration tones and complex sounds (telephone buzz). In another condition, ERPs were recorded to standard and deviant syllables, /ba/ and /da/, respectively. ERPs to vibration stimuli delivered to the fingertips were not observed at any of the sub-dural electrodes, confirming modality specificity of the auditory responses. Focal auditory ERPs consisting of P100 and N150 deflections were recorded to both tones and phonemes over the right lateral prefrontal cortex. These responses were insensitive to the serial position of the repeating sound in the stimulus train. Deviant tones evoked an MMN peaking at around 128 ms. Deviant complex sounds evoked ERPs with a similar onset latency and morphology but with an approximately two-fold increase in peak-to-peak amplitude. We conclude that right lateral prefrontal cortex (Brodmann's area 45) is involved in early stages of processing repeating sounds and sound changes.     

The mismatch negativity and the P3a components of the auditory event-related potentials in autistic low-functioning subjects.

OBJECTIVE: In order to understand better the psychophysiological basis of auditory processing abnormalities in autism, we decided to study two automatic components of the auditory event-related potentials (ERPs): the mismatch negativity (MMN)--a component of the ERP which is recorded when, during repetitive auditory stimulation, rare changes are introduced--and the novelty-related P3a which is recorded as a response to unexpected novel events occurring in a sequence of repetitive stimuli. METHODS: Ten male subjects, mean age 12.3 years (SD 4.95), affected by autism and mental retardation were admitted to this study. All patients were also mentally retarded. Ten normal male subjects, mean age 12.2 years (SD 3.94), were used as controls. Auditory evoked potentials were recorded from 19 scalp electrodes (10-20 system), and stimuli were presented in sequences consisting of 2000 tones (70 dB, ISI=800 ms). Three types of stimuli were presented: (1) standard stimuli (1000 Hz tones, 80% of total stimuli), (2) deviant stimuli (1300 Hz tones, 10% of total stimuli), and (3) novel stimuli (complex and non-monotonal, 10% of total stimuli). To quantify the MMN, the evoked response to the standard tones was subtracted from the corresponding deviant stimulus response and its amplitude and latency at peak were measured over Fz, Cz and Pz; similarly, the P3a component of the ERP was obtained by subtracting the response to the standard tone from that to the novel stimuli and its amplitude and latency at peak were measured over Fz, Cz and Pz. Also, the amplitude and latency at peak for the N1 component of the auditory evoked potential obtained with the standard stimuli were measured over Fz, Cz and Pz. The correlation between age and MMN and P3a amplitude was also analyzed. RESULTS: N1 showed significantly shorter latencies in the autistic groups. MMN elicited by deviant stimuli, but not that elicited by novel stimuli, was found to be significantly larger in autistic children than in normal controls. P3a showed higher amplitude in autistic subjects than in normal controls during childhood; the opposite was observed during young adulthood. DISCUSSION: Our findings indicate that significant changes in ERPs can also be seen in non-cooperative individuals with autism and mental retardation, which might be different from the changes already reported for high-functioning autistic subjects and deserve further insight. These changes show developmental modifications that should be taken into consideration when analyzing data from autistic subjects.     

Functional dissociation between regularity encoding and deviance detection along the auditory hierarchy

Auditory deviance detection based on regularity encoding appears as one of the basic functional properties of the auditory system. It has traditionally been assessed with the mismatch negativity (MMN) long‐latency component of the auditory evoked potential (AEP). Recent studies have found earlier correlates of deviance detection based on regularity encoding. They occur in humans in the first 50 ms after sound onset, at the level of the middle‐latency response of the AEP, and parallel findings of stimulus‐specific adaptation observed in animal studies. However, the functional relationship between these different levels of regularity encoding and deviance detection along the auditory hierarchy has not yet been clarified. Here we addressed this issue by examining deviant‐related responses at different levels of the auditory hierarchy to stimulus changes varying in their degree of deviation regarding the spatial location of a repeated standard stimulus. Auditory stimuli were presented randomly from five loudspeakers at azimuthal angles of 0°, 12°, 24°, 36° and 48° during oddball and reversed‐oddball conditions. Middle‐latency responses and MMN were measured. Our results revealed that middle‐latency responses were sensitive to deviance but not the degree of deviation, whereas the MMN amplitude increased as a function of deviance magnitude. These findings indicated that acoustic regularity can be encoded at the level of the middle‐latency response but that it takes a higher step in the auditory hierarchy for deviance magnitude to be encoded, thus providing a functional dissociation between regularity encoding and deviance detection along the auditory hierarchy.     

The mismatch negativity to frequency deviant stimuli during natural sleep

Eight subjects spent a single night in the sleep laboratory. Event-related potentials (ERPs) were recorded during the presentation of two auditory ‘oddball’ stimulus conditions in which tonal frequency was manipulated. In the first condition, 1000 Hz ‘standard’ and 2000 Hz ‘deviant’ tones were presented. In the second condition, the deviant tone was reduced to 1050 Hz. In both conditions, deviant probability was 0.2. Stimuli were presented every 600 ms during wakefulness and stages 2, 4, and REM of sleep. A distinctive N1 wave was visible in both stimulus conditions when the subject was awake. The deviant stimuli elicited a ‘mismatch negativity’ (MMN) that inverted in polarity at the mastoid. In REM sleep, an N1 and a MMN were also elicited in both conditions. In the large deviance condition, the MMN had a slightly attenuated amplitude and was shorter in duration while in the small deviant condition, its peak latency was unusually early. Neither the N1 nor the MMN could be recorded in non-REM sleep.     

Abnormal mismatch negativity in women with sexual assault-related posttraumatic stress disorder.

BACKGROUND: Disturbances in sensory processing have been hypothesized in individuals with posttraumatic stress disorder (PTSD). The authors investigated this possibility by using mismatch negativity (MMN), an event-related potential (ERP) that reflects the operation of a preconscious cortical detector of stimulus change. METHODS: Thirteen medication-free women with sexual assault-related PTSD were compared with 16 age-matched, healthy comparison women without PTSD. ERPs were elicited by regularly presented "standard" auditory stimuli and by infrequently occurring "deviant" auditory stimuli, which differed slightly in frequency. The MMN was identified in the subtraction waveforms as the difference between ERPs elicited by the deviant and standard stimuli. Group comparisons of P50, N1, P2, and N2 to the standard and to the deviant stimuli, and of the MMN in the subtraction waveform were performed. RESULTS: The amplitude of the MMN was significantly greater in the PTSD compared to the non-PTSD women. MMN was significantly correlated with the total Mississippi PTSD Symptom Scale score in the PTSD group. No significant group differences were noted in P50, N1, or P2 responding. Significant group differences in N2 were due to the increased MMN in PTSD subjects. CONCLUSIONS: The data provide evidence for abnormalities in preconscious auditory sensory memory in PTSD, whereas earlier studies have reported abnormalities in conscious processing. These data suggest an increased sensitivity to stimulus changes in PTSD and implicate the auditory cortex in the pathophysiology of the disorder.     

Do tone duration changes that elicit the mismatch negativity also affect the preceding middle latency responses?

The human brain can automatically detect sound changes. Previous studies have reported that rare sounds presented within a sequence of repetitive sounds elicit the mismatch negativity (MMN) in the absence of attention in the latency range of 100–250 ms. On the other hand, a previous study discovered that occasional changes in sound location enhance the middle latency response (MLR) elicited in the latency range of 10–50 ms. Several studies have reported an increase in the amplitude of the MLR within the frame of oddball paradigms such as frequency and location changes. However, few studies have been conducted on paradigms employing a duration change. The purpose of the present study was to examine whether the peak amplitudes of the MLR components are enhanced by a change in duration. Twenty healthy Japanese men (age: 23.9 ± 2.9 years) participated in the present study. We used an oddball paradigm that contained standard stimuli with a duration of 10 ms and deviant stimuli with a duration of 5 ms. The peak amplitudes of the MLR for the deviant stimuli were then compared with those for the standard stimuli. No changes were observed in the peak amplitude of the MLR resulting from a duration change, whereas a definite MMN was elicited. The amplitude of the MLR was increased within the frame of oddball paradigms such as frequency and location changes. By contrast, the amplitude of the MLR was not changed within the duration change oddball paradigm that elicited the MMN.     

Mismatch negativity of the color modality during a selective attention task to auditory stimuli in children with mental retardation

Event-related potentials (ERPs) in response to a stimulus change in the visual color modality were recorded in normal subjects and children with mental retardation (MR) under selective attention conditions with auditory stimuli. The paradigm included the presentation of a standard (blue color screen, B) or deviant (red, R, or greenish blue color screen, GB) visual stimulus, and a target or non-target tone burst stimulus. In Experiment 1, negativity of the subtracted waveform in response to visual stimuli with a latency of 250-280 ms was clearly observed in the ERPs of normal adults. These potentials prominently appeared at posterior sites in one condition, for which the deviant was GB, but were frontal site-dominant for the other condition. A P300 response to visual deviance was not observed in the GB-B paradigm and the subtracted negativity for this paradigm seemed to be more evident than that for the R-B paradigm. The subtracted negativities could be detected in the range of 180-400 ms after the stimulus onset in control children for the GB-B paradigm. The grand average waves of subtracted ERPs in normal children showed a similar distribution to that in normal adults. Similar subtracted potentials could be recorded with the same paradigm in children with MR, however, the negativities were different in waveform and spatial distribution than in controls. Therefore, the subtracted negativity of the present visual modality represented the analogue of the auditory mismatch negativity (MMN), and so-called 'visual MMN' was detectable in children and even in MR patients when the selective attention was directed to other stimuli.     

Independent component analysis on the mismatch negativity in an uninterrupted sound paradigm

We compared the efficiency of the independent component analysis (ICA) decomposition procedure against the difference wave (DW) and optimal digital filtering (ODF) procedures in the analysis of the mismatch negativity (MMN). The comparison was made in a group of 54 children aged 8-16 years. The MMN was elicited in a passive oddball protocol presenting uninterrupted auditory stimulation consisting of two frequent alternating tones (600 and 800 Hz) of 100 ms duration each. Infrequently, one of the 600 Hz tones was shortened to 50 or 30 ms. The event related potentials (ERPs) were decomposed into the MMN-like and non-MMN-like independent components (ICs) through the FastICA algorithm. The ICA decomposition procedure extracted a cleaner MMN compared to the ODF or DW procedures. It extracted the MMN, whose characteristics concurred with the substantial number of publications demonstrating a significantly larger peak amplitude and shorter latency of the MMN in response to the more deviant stimulus (30 ms) compared to the less deviant stimulus (50 ms). The MMN to these two deviant stimuli did not differ in the peak amplitude or latency when it was extracted through the other two procedures. The ICA decomposition and ODF procedures, similarly, significantly improved the single trial signal-to-noise ratio (SNR) of the MMN compared to the DW procedure. Due to this improvement, the proposed ICA decomposition procedure might allow shortening of the recording session and could be used to study the MMN in paradigms similar to this with small modifications.     

Functional characterization of mismatch negativity to a visual stimulus.

OBJECTIVE: To record mismatch negativity (MMN) to a visual stimulus fulfilling similar criteria to those of auditory MMN (A-MMN). METHODS: Twelve normal adults were instructed to simultaneously listen to a story and to pay attention to a visual target. Three windmill patterns that differed in the number of vanes (standard, deviant, or target) were used as visual stimuli, and were randomly presented. To ensure endogeneity, standard and deviant stimuli were alternated. To vary differences between frequent (standard) and infrequent (deviant) stimuli, deviants were changed by modulating the number of vanes. To examine effects of physical features of the target stimulus on changes in detection, two target conditions were used. The deviant-related component (DRC) was obtained by subtracting event-related potentials (ERPs) to the deviant stimulus from those to the standard stimulus. RESULTS: Seven subjects completed all phases of the experiment. Behavioral performances indicated that subjects' attention was directed by auditory context and identification of the target stimulus. Visual DRC appeared 150-300 ms after stimulus onset, and consisted of an early (DRN1) and a late (DRN2) component. Magnitude of deviancy from standard stimulus significantly influenced latency of DRN2 but not its magnitude, while changes in target stimulus affected latencies of both DRN1 and DRN2. CONCLUSIONS: Our DRCs satisfied criteria for A-MMN. In contrast to A-MMN, only latency of the DRC was associated with visual sensory discrimination and attentional reorienting. SIGNIFICANCE: It is possible to record valid MMN to a visual stimulus, which allows the study of preattentive visual information processing.     

Memory trace dependence on number of stimuli in magnetic mismatch negativity

Mismatch negativity (MMN) reflects a comparison process between a deviant stimulus and the memory trace of standard stimuli. Although this memory mechanism has been investigated by many research studies, the development of memory representation still remains unclear. In this study, we focused on the development of sound trace underlying the MMN response. We measured the magnetic counterpart of MMN (MMNm) in detail, when the neural trace of the standard sound was developed in accordance with the number of standard stimuli. When the number of standard stimuli increased, MMNm latency significantly shortened and the MMNm amplitude showed no significant change. Thus, the developmental effects on memory trace may differ between MMNm amplitude and MMNm latency.     

Modulation of mismatch negativity by stimulus deviance and modality of attention

We studied the effect of attention on the processing of auditory sensory inputs by means of the mismatch negativity (MMN) potential, which can be derived from event-related EEG. A series of frequent standard and rare deviant auditory stimuli were presented to 20 healthy subjects in two recording sessions about five weeks apart. Deviant stimuli were either low or highly deviant as compared to the standard stimulus. While MMN was recorded, subjects were performing a visual and, subsequently, an auditory discrimination task. Directing attention towards the auditory task was associated with increased MMN amplitude only in response to low deviant stimuli and only in the first recording session. No change of MMN amplitude was found when directing attention towards the visual task or when MMN was recorded in response to highly deviant auditory stimuli. The latter may trigger an involuntary switch of attention, thereby overwriting the effect of task-directed attention. Conversely, the effects of attention on the processing of low deviant stimuli appear to be fragile and diminish with increasing automaticity of task execution.     

Event-related potential indices of auditory vowel processing in 3-year-old children

Objective: To determine the ERP characteristics and ERP indices of central speech sound encoding and discrimination in young children.Methods: Auditory sensory event-related potentials (ERPs) and the ERP index of auditory sensory discrimination (the mismatch negativity, MMN) were elicited by vowel stimuli in 3-year-old children. In an oddball paradigm, the standard stimulus was vowel /a/, one deviant stimulus was vowel /o/ (the across-category change), and the other was nasalized vowel /a/ (within-category change). In addition, the ERP changes occurring during the 14 min uninterrupted recording were examined.Results: As indexed by the sensory P1, N2, and N4 peaks, the 3-year-old children's transient neural encoding of vowels was comparable to that earlier registered in 1-year-old children but also showed vowel-specific characteristics observed in school-age children. The 3-year-old's MMN was comparable in amplitude to the school-age children's MMN and appeared to be sensitive to the across-category aspects of vowel changes. However, its latency was longer in the 3-year-olds than in school-age children. Among the sensory ERPs, only the N4 peak showed significant diminution during the experiment. The across-category change MMN diminished after 10 min of the recording, however, over the frontal areas only.Conclusions: In the 3-year-old children, the sensory processing of vowels exhibited transitional characteristics between those observed in infants and school-age children. The auditory sensory discrimination in the 3-year-olds appeared to be sensitive to the phonemic aspects of stimulus change. The frontally-predominant MMN diminution during the experiment might indicate the greater refractoriness of its frontal-lobe generators. In general, the auditory sensory ERPs show distinct maturational profiles from that of the MMN.     

The mismatch negativity and reaction time as indices of the perceptual distance between the corresponding vowels of two related languages

Two experiments were conducted to determine whether vowel familiarity affects automatic and conscious vowel discrimination. Familiar (Finnish) and unfamiliar (Komi) vowels were presented to Finnish subjects. The good representatives of Finnish and Komi mid vowels were grouped into three pairs: front /e- epsilon /, central /?-oe/, and back /o-o/. The acoustic difference for /e- epsilon / and /o-o/ was smaller than that for /?-oe/. For /e- epsilon /, the Komi vowel / epsilon / was at the boundary between the Finnish /e/ and /ae/. The stimuli were presented in an oddball paradigm. In three different blocks, each Komi vowel in turn served as the standard (probability 0.86) and the corresponding Finnish vowel as the deviant stimulus (probability 0.14), and vice versa. In Experiment 1, subjects were instructed to press a button as soon as they detected a deviant stimulus. In Experiment 2, event-related potentials (ERPs) were recorded to these stimuli in order to use the mismatch negativity (MMN) as an index of the perceptual distance between the members of each vowel pair, while subjects did not attend to the stimuli. There were similar effects of the acoustic distance within a vowel pair for both the reaction time (RT) and the MMN amplitude; the RT decreased and the MMN amplitude increased when the acoustic difference between the stimuli increased. However, the RT was longer when the Komi / epsilon / was the standard and the Finnish /e/ was the deviant than vice versa. No such pattern was found for the MMN. Thus, the phonemic status of the standard stimulus seems to play a role at the attentive but not at the pre-attentive level.     

Maturation of cortical mismatch responses to occasional pitch change in early infancy: effects of presentation rate and magnitude of change

Previous studies have reported two types of event-related potential (ERP) mismatch responses in infants to infrequent auditory changes: a broad discriminative positivity in younger infants and a negativity resembling adult mismatch negativity (MMN) in older infants. In the present study, we investigated whether the positive discriminative slow wave and the adult-like MMN are functionally distinct by examining how they are affected by presentation rate and magnitude of change. We measured ERPs from adults, 2-month-olds, and 4-month-olds to a repeating piano tone (standard) that occasionally changed in pitch (deviant). The pitch changes between standards and deviants were either small (1/12 octave) or large (1/2 octave) in magnitude, and the stimulus presentation rate was either slow (800 ms SOA) or fast (400 ms SOA). As the presentation rate increased, both adults and 4-month-olds showed an MMN response that decreased in latency, but was unaffected in amplitude. As the magnitude of the pitch change increased, MMN increased in amplitude. On the other hand, only a broad positive mismatch response was seen in 2-month-olds. As the presentation rate increased, 2-month-olds’ responses to standard tones decreased in amplitude while their responses to deviant tones were unaffected. The magnitude of the pitch change did not affect 2-month-olds’ responses. These results suggest that pitch is processed differently in auditory cortex by 2-month-olds and 4-month-olds, and that a cortical change-detection mechanism for pitch discrimination similar to that of adults emerges between 2 and 4 months of age.     

Automatic discriminative sensitivity inside temporal window of sensory memory as a function of time

Neural representation of preceding sound-patterns stored in the human brain, as reflected by mismatch negativity (MMN) related to the automatic discriminative process, is restricted to a duration of 160-170 ms due to the short form of auditory sensory memory termed the temporal window of integration (TWI). To examine the temporal uniformity of deviation-sensitivity inside TWI of sensory memory, magnetic MMN (MMNm) responses were measured with a dual 37-channel magnetometer for complex sounds of 170 ms duration containing an omitted (silent) segment. Frequent standard stimuli (probability of 80%) consisted of five tone segments. Deviant stimuli were different from standard stimuli in that one of four segments was occasionally (probability of 5%) omitted and replaced by a silent segment. The stimulus duration of 170 ms was intended to correspond to the postulated duration of TWI. When the silent segment occurred later in deviant stimulus, the MMNm peak amplitude was attenuated and MMNm peak latency, measured from the onset of each silent segment, was delayed. Thus, automatic deviation-detection sensitivity declines nonlinearly toward the end of TWI in auditory sensory memory. In the second experiment, two types of deviant stimuli, which differed from each other only in the period after the occurrence of the silent segment, elicited MMNm with the same peak latency but with a different peak amplitude. Thus, mismatch process is triggered at the moment of change but still lasts after the detection of deviation. In other words, both standard and deviant stimuli are treated as a unitary event within a TWI.     

The individual replicability of mismatch negativity at short and long inter-stimulus intervals.

OBJECTIVES: The individual replicability of the mismatch negativity (MMN) event-related brain potential (ERP) was studied at two different inter-stimulus intervals (ISIs), to establish its potential value for routine clinical evaluation of sound discrimination and auditory sensory memory. METHODS: Ten healthy young subjects were presented sequences of 3 stimulus trains, in two recording sessions approximately 1 month apart. The stimuli in the trains were delivered at an ISI of 300 ms, whereas the inter-train intervals (ITIs) were 0.4 s and 4.0 s in different blocks. ERPs were averaged to standard (75 ms) and deviant (25 ms) tones started equiprobably the stimulus trains. RESULTS: Significant Pearson product-moment correlations coefficients were found between sessions at all scalp locations for the short ITI, when the MMN was quantified as the mean amplitude in the 100-200 ms latency window around its peak. However, none of the correlations reached significance for the longer ITI. CONCLUSIONS: MMN appears to be a reliable measure for single-case assessment and follow-ups when obtained at short ISIs and quantified as an integrated window of neuroelectric activation over a temporal span.     

Mismatch negativity to inclusions of noise within complex spectrotemporal sound patterns.

Event-related potentials to complex spectrotemporal sound patterns were recorded during non-attend conditions. A high-intensity noise deviant elicited a large negative wave. This is probably a combined mismatch negativity (MMN) and N2b since it was followed by a large amplitude frontal positive wave (P3a). When the noise intensity was reduced, a smaller amplitude negative wave was elicited. This probably corresponds to a true MMN since it was not followed by the positive wave. These findings are consistent with previous research in which N2b is elicited in non-attend conditions when the deviant stimulus was particularly difficult to ignore. These findings demonstrate that complex spectrotemporal sound patterns are represented in auditory memory and that inclusions of noise within these complex stimuli can be passively discriminated.     

Parameter-specific modulation of the mismatch negativity to duration decrement and increment: Evidence for asymmetric processes

ObjectiveThe mismatch negativity (MMN) component of event-related potentials (ERPs) reflects a change-detection process in the brain. The present study investigated whether stimulus parameters (sound type and duration) exert a differential influence on the MMN for a duration decrement and increment of an equal magnitude. Some asymmetries were reported in the previous studies; yet no systematical study has been conducted.MethodsERPs were recorded from 16 healthy adults presented with repetitive standard sounds interspersed with duration changes (deviant sounds). In separate sequences, stimuli were vowels, music chord, sinusoid, or band-pass filtered white noise. The stimulus durations (standard/deviant) were either 200/120 ms or 400/240 ms for decrements, and vice versa for increments.ResultsThe MMN for the increments was abolished in the 400/240 ms condition, whereas the MMN for decrements was significant irrespective of the sound duration. The amplitude of the increment MMN paralleled with the spectral complexity of the stimulus sound, whereas that of the decrement MMN was larger for natural sounds than artificial sounds.ConclusionsThe observed interactions demonstrated asymmetries in the MMN for duration increment and decrement.SignificanceThe present findings suggest that the effects of stimulus parameters should be taken into account when comparing different studies, especially where clinical populations are involved, with one another.     

The mismatch negativity (MMN) with no standard stimulus

ObjectiveThe recent fast multi-feature mismatch negativity (MMN) paradigms rest on the assumption that the deviant stimuli, alternating with the standard tone, strengthen the memory trace of the standard in respect to those attributes they have in common. In the present study, we tested whether the MMN can be recorded even without the standard stimulus, with the invariant properties of the deviant stimuli serving as a standard against which to detect the sound changes.MethodsMMN was recorded for changes in sound duration, frequency, intensity, location, gap, brightness, density, and noise level in a new multi-feature paradigm where no standard stimuli were used. In addition, these MMNs were compared with those recorded in the conventional multi-feature paradigm.ResultsAll sound changes elicited significant MMN responses that were highly similar between paradigms.ConclusionsThe MMN can be recorded even without the standard stimulus, as an accurate memory trace is constructed for the invariant features of the auditory input.SignificanceOmitting the standard stimuli results in almost 50% shorter recording time and the larger selection of deviant types with the newly introduced brightness, density, and noise-level changes provides even more information on the individual perceptual profiles than conventional multi-feature paradigms.