Fast parametric evaluation of central speech-sound processing with mismatch negativity (MMN)

Investigating the neurocognitive background of speech perception with a fast multi-feature MMN paradigm

The speech multi-feature MMN (Mismatch Negativity) offers a means to explore the neurocognitive background of the processing of multiple speech features in a short time, by capturing the time-locked electrophysiological activity of the brain known as event-related brain potentials (ERPs). Originating from Näätänen et al. (Clin Neurophysiol 115:140-144, 2004) pioneering work, this paradigm introduces several infrequent deviant stimuli alongside standard ones, each differing in various speech features. In this study, we aimed to refine the multi-feature MMN paradigm used previously to encompass both segmental and suprasegmental (prosodic) features of speech. In the experiment, a two-syllable long pseudoword was presented as a standard, and the deviant stimuli included alterations in consonants (deviation by place or place and mode of articulation), vowels (deviation by place or mode of articulation), and stress pattern in the first syllable of the pseudoword. Results indicated the emergence of MMN components across all segmental and prosodic contrasts, with the expected fronto-central amplitude distribution. Subsequent analyses revealed subtle differences in MMN responses to the deviants, suggesting varying sensitivity to phonetic contrasts. Furthermore, individual differences in MMN amplitudes were noted, partially attributable to participants' musical and language backgrounds. These findings underscore the utility of the multi-feature MMN paradigm for rapid and efficient investigation of the neurocognitive mechanisms underlying speech processing. Moreover, the paradigm demonstrated the potential to be used in further research to study the speech processing abilities in various populations.

Discriminatory Brain Processes of Native and Foreign Language in Children with and without Reading Difficulties

The association between impaired speech perception and reading difficulty has been well established in native language processing, as can be observed from brain activity. However, there has been scarce investigation of whether this association extends to brain activity during foreign language processing. The relationship between reading skills and neuronal speech representation of foreign language remains unclear. In the present study, we used event-related potentials (ERPs) with high-density EEG to investigate this question. Eleven- to 13-year-old children typically developed (CTR) or with reading difficulties (RD) were tested via a passive auditory oddball paradigm containing native (Finnish) and foreign (English) speech items. The change-detection-related ERP responses, the mismatch response (MMR), and the late discriminative negativity (LDN) were studied. The cluster-based permutation tests within and between groups were performed. The results showed an apparent language effect. In the CTR group, we found an atypical MMR in the foreign language processing and a larger LDN response for speech items containing a diphthong in both languages. In the RD group, we found unstable MMR with lower amplitude and a nonsignificant LDN response. A deficit in the LDN response in both languages was found within the RD group analysis. Moreover, we observed larger brain responses in the RD group and a hemispheric polarity reversal compared to the CTR group responses. Our results provide new evidence that language processing differed between the CTR and RD groups in early and late discriminatory responses and that language processing is linked to reading skills in both native and foreign language contexts.

The Neural Representation of a Repeated Standard Stimulus in Dyslexia

The neural representation of a repeated stimulus is the standard against which a deviant stimulus is measured in the brain, giving rise to the well-known mismatch response. It has been suggested that individuals with dyslexia have poor implicit memory for recently repeated stimuli, such as the train of standards in an oddball paradigm. Here, we examined how the neural representation of a standard emerges over repetitions, asking whether there is less sensitivity to repetition and/or less accrual of "standardness" over successive repetitions in dyslexia. We recorded magnetoencephalography (MEG) as adults with and without dyslexia were passively exposed to speech syllables in a roving-oddball design. We performed time-resolved multivariate decoding of the MEG sensor data to identify the neural signature of standard vs. deviant trials, independent of stimulus differences. This "multivariate mismatch" was equally robust and had a similar time course in the two groups. In both groups, standards generated by as few as two repetitions were distinct from deviants, indicating normal sensitivity to repetition in dyslexia. However, only in the control group did standards become increasingly different from deviants with repetition. These results suggest that many of the mechanisms that give rise to neural adaptation as well as mismatch responses are intact in dyslexia, with the possible exception of a putatively predictive mechanism that successively integrates recent sensory information into feedforward processing.

Verbal and Nonverbal Mismatch Negativity in Children with Typical Development: Variables Analysis

Introduction  Mismatch negativity (MMN) is a promising instrument for the investigation of different auditory disorders, as it does not need behavioral responses. Objective  To analyze the influence of the ear, gender and age variables in the MMN in children with typical development; and to compare the different measures of this potential, using verbal and nonverbal stimuli in the sample studied, providing reference values. Methods  Observational, descriptive, cross-sectional, quantitative study, with 23 children, aged from 5 to 11 years and 11 months old, divided by age group. Mismatch negativity was performed using verbal and nonverbal stimuli, and the data was analyzed by means of the statistical Student t -test. Results  No significant differences were noted for the ear, gender and age variables in the MMN with both stimuli. There were significant differences for the latency, duration and area variables when the stimuli were compared. The reference values established for nonverbal stimuli were: latency 249.8 milliseconds, amplitude 2.28 µv, duration 82.97 milliseconds, and area 137.3 microvolt x microseconds (μVx μs); as for the verbal stimuli, they were: latency 265.3 milliseconds, amplitude - 2.82 µv, duration 110.5 milliseconds, and area 225.5 microvolt x microseconds (μVx μs). Conclusion  The variables studied did not influence the recordings of the MMN. Latency, duration and area of the MMN with verbal stimuli were higher. It was possible to furnish reference values for children with typical development in the age group studied.

Asymmetries in Accessing Vowel Representations Are Driven by Phonological and Acoustic Properties: Neural and Behavioral Evidence From Natural German Minimal Pairs

In vowel discrimination, commonly found discrimination patterns are directional asymmetries where discrimination is faster (or easier) if differing vowels are presented in a certain sequence compared to the reversed sequence. Different models of speech sound processing try to account for these asymmetries based on either phonetic or phonological properties. In this study, we tested and compared two of those often-discussed models, namely the Featurally Underspecified Lexicon (FUL) model (Lahiri and Reetz, 2002) and the Natural Referent Vowel (NRV) framework (Polka and Bohn, 2011). While most studies presented isolated vowels, we investigated a large stimulus set of German vowels in a more naturalistic setting within minimal pairs. We conducted an mismatch negativity (MMN) study in a passive and a reaction time study in an active oddball paradigm. In both data sets, we found directional asymmetries that can be explained by either phonological or phonetic theories. While behaviorally, the vowel discrimination was based on phonological properties, both tested models failed to explain the found neural patterns comprehensively. Therefore, we additionally examined the influence of a variety of articulatory, acoustical, and lexical factors (e.g., formant structure, intensity, duration, and frequency of occurrence) but also the influence of factors beyond the well-known (perceived loudness of vowels, degree of openness) in depth via multiple regression analyses. The analyses revealed that the perceptual factor of perceived loudness has a greater impact than considered in the literature and should be taken stronger into consideration when analyzing preattentive natural vowel processing.

Mismatch Negativity Elicited by Verbal and Nonverbal Stimuli: Comparison with Potential N1

Introduction  Mismatch negativity (MMN) is a long latency auditory evoked potential, represented by a negative wave, generated after the potential N1 and visualized in a resulting wave. Objective  To identify the time of occurrence of MMN after N1, elicited with verbal and nonverbal stimuli. Methods  Ninety individuals aged between 18 and 56 years old participated in the study, 39 of whom were male and 51 female, with normal auditory thresholds, at least 8 years of schooling, and who did not present auditory processing complaints. All of them underwent audiologic anamnesis, visual inspection of external auditory meatus, pure tone audiometry, speech audiometry, acoustic immittance measures and the dichotic sentence identification test as a screening for alterations in auditory processing, a requirement to participate in the sample. The MMN was applied with two different stimuli, with these being da/ta (verbal) and 750 Hz and 1,000 Hz (nonverbal). Results  There was a statistically significant difference between the latency values of the N1 potential and the MMN with the two stimuli, as well as between the MMN with verbal and nonverbal stimuli, and the latency of the MMN elicited with da/ta being greater than that elicited with 750 Hz and 1,000 Hz, which facilitated its visualization. Conclusion  The time of occurrence of MMN after the N1 elicited with verbal stimuli was 100.4 ms and with nonverbal stimuli 85.5 ms. Thus, the marking of the MMN with verbal stimuli proved to be more distant from N1 compared with the nonverbal stimuli.

Mismatch Negativity Occurrence with Verbal and Nonverbal Stimuli in Normal-Hearing Adults

Introduction  The mismatch negativity (MMN) is a long-latency auditory evoked potential related to a passive elicited auditory event.

Objective  To verify the occurrence of MMN with different stimuli, to describe reference values in normal-hearing adults with verbal and nonverbal stimuli and to compare them with each other, besides analyzing the latency, area, and amplitude regarding gender and between the ears.

Method  Normal-hearing individuals, aged between 18 and 59 years old, participated in the study. As inclusion criterion in the study, all of them underwent tone threshold audiometry, logoaudiometry, tympanometry, and the Dichotic Sentence Identification (DSI) test, and later the MMN with 4 different stimuli, being 2 verbal (da/ta and ba/di) and 2 nonverbal stimuli (750/1,000Hz and 750/4,000Hz), which are considered stimuli with low and high contrast.

Results  A total of 90 individuals composed the sample, being 39 males and 51 females, with an average age of 26.9 years old. In the analysis of the latency, amplitude, and area of the four stimuli between the ears, they were not considered statistically different. There was a significant difference between all of the stimuli in terms of latency, amplitude and area, with the highest latency found in da/ta, and the greatest amplitude and area in ba/di. Regarding gender, there was only difference in the latency of the da/ta stimulus.

Conclusion  The da/ta and 750/1,000Hz stimuli elicited the most MMN in the population of normal-hearing adults. Among the genders, there was difference only regarding the latency of the verbal stimulus da/ta, and there was no difference between the ears.

Using rotated speech to approximate the acoustic mismatch negativity response to speech

The mismatch negativity (MMN) response is influenced by the magnitude of the acoustic difference between standard and deviant, and the response is typically larger to linguistically relevant changes than to linguistically irrelevant changes. Linguistically relevant changes between standard and deviant typically co-occur with differences between the two acoustic signals. It is therefore not straightforward to determine the contribution of each of those two factors to the MMN response. This study investigated whether spectrally rotated speech can be used to determine the impact of the acoustic difference on the MMN response to a combined linguistic and acoustic change between standard and deviant. Changes between rotated vowels elicited an MMN of comparable amplitude to the one elicited by a within-category vowel change, whereas the between-category vowel change resulted in an MMN amplitude of greater magnitude. A change between rotated vowels resulted in an MMN ampltude more similar to that of a within-vowel change than a complex tone change did. This suggests that the MMN amplitude reflecting the acoustic difference between two speech sounds can be well approximated by the MMN amplitude elicited in response to their rotated counterparts, in turn making it possible to estimate the part of the response specific to the linguistic difference.

Electrophysiological and phonological change detection measures of auditory word processing in normal Persian-speaking children

OBJECTIVE

Auditory phoneme discrimination is a basic and important prerequisite for acquiring speech, reading, and spelling skills. Children, who are unable to perceive auditory phoneme discrimination, cannot develop phonemic representations. Therefore, the early identification of these deficits and application of effective therapeutic approaches is a necessity. We need to assess appropriately word or sound discrimination in normal populations using an objective passive task such as mismatch negativity (MMN). Therefore, the aim of the present study was to investigate MMN responses using speech stimuli (words) in 6-7 year-old normal Persian-speaking children.

METHODS

Ten right-handed Persian-speaking children with normal visual and auditory acuity, aged from 6 to 7 years, participated in the study. Recording of electroencephalography (EEG) was done by 64 A g/AgCl electrodes. A new auditory paradigm was used with three deviant stimuli (/gam/,/jam/, and/tam/) which differed in the first consonant from a repeated standard word (/dam/). A total of 1500 stimuli, 750 standards and 750 deviants (250 each deviant), were presented by Cogent 2000 running in MATLAB software using two loud speakers.

RESULTS

MMN peaked over the fronto-central sites at around 380-424 ms after the onset of the stimulus. The comparison of the MMN amplitudes elicited by three deviants revealed a significant "initial phoneme type" effect in Fz and Cz (p < 0.05). This negativity was found to be larger for manner and voicing deviants compared with that of the place of articulation (p < 0.001) on midline scalps. The comparison of the MMN latencies revealed no significant main effect of all variables (p > 0.05). Also, the results revealed that only the MMN amplitude for the/gam/deviant correlated with the percentage of correct responses (R = -0.86, p < 0.01).

CONCLUSION

The current study showed that words can elicit MMN responses in ∼200 ms after the onset of changes. We can objectively evaluate children's neural speech sound discrimination using the developed paradigm in a natural word context. This paradigm can be useful objectively for investigating distinctive features of sounds and phonological discrimination development in normal children.

Neural indices of phonemic discrimination and sentence-level speech intelligibility in quiet and noise: A mismatch negativity study

Successful speech communication requires the extraction of important acoustic cues from irrelevant background noise. In order to better understand this process, this study examined the effects of background noise on mismatch negativity (MMN) latency, amplitude, and spectral power measures as well as behavioral speech intelligibility tasks. Auditory event-related potentials (AERPs) were obtained from 15 normal-hearing participants to determine whether pre-attentive MMN measures recorded in response to a consonant (from /ba/ to /bu/) and vowel change (from /ba/ to /da/) in a double-oddball paradigm can predict sentence-level speech perception. The results showed that background noise increased MMN latencies and decreased MMN amplitudes with a reduction in the theta frequency band power. Differential noise-induced effects were observed for the pre-attentive processing of consonant and vowel changes due to different degrees of signal degradation by noise. Linear mixed-effects models further revealed significant correlations between the MMN measures and speech intelligibility scores across conditions and stimuli. These results confirm the utility of MMN as an objective neural marker for understanding noise-induced variations as well as individual differences in speech perception, which has important implications for potential clinical applications.

The effects of stimulus complexity on the preattentive processing of self-generated and nonself voices: An ERP study

The ability to differentiate one's own voice from the voice of somebody else plays a critical role in successful verbal self-monitoring processes and in communication. However, most of the existing studies have only focused on the sensory correlates of self-generated voice processing, whereas the effects of attentional demands and stimulus complexity on self-generated voice processing remain largely unknown. In this study, we investigated the effects of stimulus complexity on the preattentive processing of self and nonself voice stimuli. Event-related potentials (ERPs) were recorded from 17 healthy males who watched a silent movie while ignoring prerecorded self-generated (SGV) and nonself (NSV) voice stimuli, consisting of a vocalization (vocalization category condition: VCC) or of a disyllabic word (word category condition: WCC). All voice stimuli were presented as standard and deviant events in four distinct oddball sequences. The mismatch negativity (MMN) ERP component peaked earlier for NSV than for SGV stimuli. Moreover, when compared with SGV stimuli, the P3a amplitude was increased for NSV stimuli in the VCC only, whereas in the WCC no significant differences were found between the two voice types. These findings suggest differences in the time course of automatic detection of a change in voice identity. In addition, they suggest that stimulus complexity modulates the magnitude of the orienting response to SGV and NSV stimuli, extending previous findings on self-voice processing.

Mismatch negativity in children with specific language impairment and auditory processing disorder

Introduction

Mismatch negativity, an electrophysiological measure, evaluates the brain's capacity to discriminate sounds, regardless of attentional and behavioral capacity. Thus, this auditory event-related potential is promising in the study of the neurophysiological basis underlying auditory processing.

Objective

To investigate complex acoustic signals (speech) encoded in the auditory nervous system of children with specific language impairment and compare with children with auditory processing disorders and typical development through the mismatch negativity paradigm.

Methods

It was a prospective study. 75 children (6–12 years) participated in this study: 25 children with specific language impairment, 25 with auditory processing disorders, and 25 with typical development. Mismatch negativity was obtained by subtracting from the waves obtained by the stimuli /ga/ (frequent) and /da/ (rare). Measures of mismatch negativity latency and two amplitude measures were analyzed.

Results

It was possible to verify an absence of mismatch negativity in 16% children with specific language impairment and 24% children with auditory processing disorders. In the comparative analysis, auditory processing disorders and specific language impairment showed higher latency values and lower amplitude values compared to typical development.

Conclusion

These data demonstrate changes in the automatic discrimination of crucial acoustic components of speech sounds in children with specific language impairment and auditory processing disorders. It could indicate problems in physiological processes responsible for ensuring the discrimination of acoustic contrasts in pre-attentional and pre-conscious levels, contributing to poor perception.

Middle latency response correlates of single and double deviant stimuli in a multi-feature paradigm

OBJECTIVE

This study aimed to test single and double deviance-related modulations of the middle latency response (MLR) and the applicability of the optimum-2 multi-feature paradigm.

METHODS

The MLR and the MMN to frequency, intensity and double-feature deviants of an optimum-2 multi-feature paradigm and the MMN to double-feature deviants of an oddball paradigm were recorded in young adults.

RESULTS

Double deviants elicited significant enhancements of the Nb and Pb MLR waves compared with the waves elicited by standard stimuli. These enhancements equalled approximately the sum of the numerical amplitude differences elicited by the single deviants. In contrast, the MMN to double deviants did not show such additivity. MMNs elicited by double deviants of the multi-feature and the oddball paradigm showed no significant difference in amplitude or latency.

CONCLUSIONS

The optimum-2 multi-feature paradigm is suitable for recording double deviance-related modulations of the MLR. Interspersed intensity and frequency deviants in the standard trace of the optimum-2 condition multi-feature paradigm did not weaken the double MMN.

SIGNIFICANCE

The optimum-2 multi-feature paradigm could be especially beneficial for clinical studies on early deviance-related modulations in the MLR, due to its optimized utilization of the recording time.

The neural basis of sublexical speech and corresponding nonspeech processing: a combined EEG-MEG study

We addressed the neural organization of speech versus nonspeech sound processing by investigating preattentive cortical auditory processing of changes in five features of a consonant-vowel syllable (consonant, vowel, sound duration, frequency, and intensity) and their acoustically matched nonspeech counterparts in a simultaneous EEG-MEG recording of mismatch negativity (MMN/MMNm). Overall, speech-sound processing was enhanced compared to nonspeech sound processing. This effect was strongest for changes which affect word meaning (consonant, vowel, and vowel duration) in the left and for the vowel identity change in the right hemisphere also. Furthermore, in the right hemisphere, speech-sound frequency and intensity changes were processed faster than their nonspeech counterparts, and there was a trend for speech-enhancement in frequency processing. In summary, the results support the proposed existence of long-term memory traces for speech sounds in the auditory cortices, and indicate at least partly distinct neural substrates for speech and nonspeech sound processing.