The impact of spectral resolution on the mismatch response to Mandarin Chinese tones: An ERP study of cochlear implant simulations

ObjectiveThis study examined the impact of spectral resolution on the processing of lexical tones and the number of frequency channels required for a cochlear implant (CI) to transmit Chinese tonal information to the brain.MethodsERPs were recorded in an auditory oddball task. Normal-hearing participants listened to speech sounds of two tones and their CI simulations in 1, 4, 8, or 32 channels. The mismatch response elicited by speech sounds and CI simulations in different numbers of channels were compared.ResultsThe mismatch negativity (MMN) was observed for speech sounds. For the 1-channel CI simulations, deviants elicited a more positive waveform than standard stimuli. No MMN response was observed with the 4-channel simulations. A reliable MMN response was observed for the 8- and 32-channel simulations. The MMN responses elicited by the 8- and 32-channel simulations were equivalent in magnitudes and smaller than that elicited by speech sounds.ConclusionsMore than eight frequency channels are required for a CI to transmit Chinese tonal information. The presence of both positive and negative mismatch responses suggests multiple mechanisms underlying auditory mismatch responses.SignificanceThe current findings of spectral resolution constraints on the transmission of tonal information should be taken into account in the design of the CI devices.     

Mismatch negativity and frequency representational width in children with specific language impairment

The aim of this study was to compare the degree of frequency separation that is required between tones to generate mismatch negativity (MMN) in a group of children with specific language impairment (SLI) and a comparison group, who had their temporal processing abilities assessed in a previous experiment. Using a 1000Hz standard (85%) and 1020, 1050, and 1100Hz deviant tones presented at inter-stimulus intervals (ISIs) of 200 and 400ms, MMN was compared in 19 children with SLI (13 males, six females, age range 7y 4mo-11y 10mo, mean age 9y 7mo [SD 1y 2mo]), and 19 comparison children (13 males, six females, age range 7y 3mo-11y 4mo, mean age 9y 5mo [SD 1y 3mo]). Temporal processing ability was assessed by the Auditory Fusion Test-Revised. Children with SLI who had poor temporal processing abilities generated a positive mismatch response (P-MMR) for 2% tone contrasts at 400ms ISI but MMN with larger contrasts. These children also generated stronger MMN than the comparison group at 200ms ISI for 2% contrasts. Children with SLI who had good temporal processing abilities generated only P-MMR in response to contrasts up to 10% for both ISIs. Some children with SLI show an inverse relationship between frequency discrimination and temporal processing. Furthermore, certain stimulus-related and biological criteria may need to be met for P-MMR to switch to MMN.     

Neurophysiological evidence of memory traces for words in the human brain

Mismatch negativity (MMN), an index of experience-dependent memory traces, was used to investigate the processing of lexical contrasts in the human brain. The MMN was elicited either by rare words presented among repetitive words or pseudowords, or by pseudowords presented among words. Phonetic and phonological contrasts were identical in all conditions. MMNs elicited by both word deviants were larger than that elicited by the deviant pseudoword. The presence of lexical contrast did not significantly alter the word-elicited MMNs, which were, however, distinct in amplitude and topography from the MMN evoked by pseudowords. Thus, our results indicate the existence of word-related MMN enhancement largely independent of the lexical status of the standard stimulus. This enhancement may reflect the presence of a long-term memory trace for a spoken word.     

Mismatch negativity to pitch contours is influenced by language experience

A cross-language study utilizing the mismatch negativity (MMN) evoked response was conducted to explore the influence of language experience on the preattentive cortical processing of linguistically relevant pitch contours. Chinese and English subjects were presented with Mandarin Chinese tones while the mismatch negativity (MMN) response was elicited using a passive oddball paradigm. Two oddball conditions were constructed with a common deviant, a low falling rising contour tone (T3). One condition consisted of two tones that are acoustically similar to one another (T2/T3: T2, high rising contour=standard). The other condition consisted of two tones that are acoustically dissimilar to one another (T1/T3: T1, high level=standard). These tonal pairs enabled us to assess whether different degrees of similarity between pitch movements exert a differential influence on preattentive pitch processing. Results showed that the mean MMN amplitude of the Chinese group was larger than that of the English group for the T1/T3 condition. No group differences were found for the T2/T3 condition. The mean MMN amplitude was larger for the T1/T3 relative to the T2/T3 condition for the Chinese group only. By virtue of these language group differences, we infer that early cortical processing of pitch contours may be shaped by the relative saliency of acoustic dimensions underlying the pitch patterns of a particular language.     

Finding the right control: The mismatch negativity under investigation

ObjectiveWhen investigating auditory perceptual regularity processing, mismatch negativity (MMN) is commonly used. MMN is computed as a difference signal between the event-related potentials (ERPs) elicited by repeated standard tones and rarely occurring deviant tones. This procedure leads to an underestimation of the N1 component elicited by standards compared to the N1 to deviants which might affect the MMN. Consequently, a random control design was previously introduced. This design, however, overestimates the N1 to the deviant. Here, we developed a new paradigm that avoids previous drawbacks.MethodsWe designed a regular cascadic sequence as a control to the deviant. ERPs were measured while presenting conventional oddball blocks (standards, deviants), random control blocks and a cascadic control block.ResultsMMN was observed in each difference signal. Regarding the N1, standards elicited smallest amplitudes. The N1 for the deviant and the cascadic control was comparable. The largest N1 was elicited by the random control.ConclusionStandards underestimate N1 refractoriness effects in the responses to deviants, while random control tones overestimate. Cascadic control tones, however, provide a reasonable estimation for the N1.SignificanceThe new cascadic control design is suitable to investigate auditory perceptual regularity processes while controlling for N1 refractoriness effects.     

Developmental changes in brain response to speech perception in late-talking children: A longitudinal MMR study

This study used a longitudinal design to examine the development of mismatch responses (MMRs) to Mandarin lexical tones, an index of neural speech discriminative responses, in late talkers and typical controls at 3, 5, and 6 years of age. Lexical tones are phonetic suprasegments that distinguish the lexical meanings of syllables in tonal languages. The 2 year-old late talkers were later divided into persistent language delay and late bloomer groups according to their performance on standardized language tests at 4 years. Results showed that children with persistent language delay demonstrated more positive mismatch responses than the typical controls at 3 years of age. At the age of 5, no group difference were found in the amplitude of MMRs, but the maturation of MMRs could be observed in the change of topography, with more prominent negative response in the frontal sites only in the typical group. Correlations were found between the index of MMRs at 3 years and children’s language performance outcome at 6 years. Our results indicate that the development of fine-grained tone representations is delayed in late-talking children between 3 and 5 years and may be one of the underlying mechanisms which associated with later language performance.     

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.     

Are different kinds of acoustic features processed differently for speech and non-speech sounds?

This study examined how changes in different types of acoustic features are processed in the brain for both speech and non-speech sounds. Event-related potentials (ERPs) were recorded in native Finnish speakers presented with sequences of repetitive vowels (/e/) or complex harmonical tones interspersed with infrequent changes in duration, frequency and either a vowel change (/o/ for vowel sequences) or a double deviant (frequency+duration change for tone sequences). The stimuli were presented monaurally in separate blocks to either the left or right ear. The results showed that speech stimuli were more efficiently processed than harmonical tones as reflected by an enhanced mismatch negativity (MMN) and P3a ERP components. In addition, the duration change in vowels elicited a larger MMN component than the equivalent change in tones. This result might reflect enhanced processing of duration features in the Finnish language in which phoneme duration plays a critical role.     

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.     

Electrophysiological evidence of categorical perception of Chinese lexical tones in attentive condition

Previous electrophysiological evidence supports categorical perception of Chinese lexical tones at the preattentive stage (Xi and colleagues). In this study, we examined participants' attentive responses to tonal continua in an event-related potential experiment that recorded their N2b and P3b oddball responses. We found that for both the N2b and the P3b component, the responses elicited by the within-category deviants were similar in the left and the right recording sites. However, the across-category deviants elicited larger responses in the left recording sites than in the right sites, reflecting conscious phonological processing of lexical tones. These results provide electrophysiological correlates of categorical perception of Chinese lexical tones in later stages associated with controlled processes.     

Evidence that the mismatch negativity system works on the basis of objects

The purpose of this study was to determine whether the system that underlies the mismatch negativity (MMN) of event-related potentials would operate on the basis of objects if stimuli were delivered in such a way as to create the impression of two objects. To this end, tones were alternated between ears with one combination of features for each ear. Deviant tones, which differed from the standard tones of both ears, were delivered separately to each ear. The deviants elicited MMNs only with respect to the standards of the ear to which they were delivered. The data indicate that the MMN system operated on the basis of objects and that the integration of objects occurs preattentively in the auditory system.     

Preattentive discrimination of across-category and within-category change in consonant-vowel syllable

Event-related potentials to infrequently presented spoken deviant syllables /pi/ and /po/ among repetitive standard [see text] syllables were recorded in Thai study participants who ignored these stimuli while reading books of their choices. The vowel across-category and within-category changes elicited a change-specific mismatch negativity response. The across-category and within-category change discrimination of vowels in consonant-vowel syllable was also assessed using the low-resolution electromagnetic tomography. The results of low-resolution electromagnetic tomography mismatch negativity generator analysis suggest that the within-category change perception of vowels is analyzed as the change in physical features of the stimuli, thus predominantly activating the right temporal cortex. In contrast, the left temporal cortex is predominantly activated in the across-category change perception of vowels, emphasizing the role of the left hemisphere in speech processing already at a preattentive processing level also in consonant-vowel syllables. The results support the hypothesis that a part of the superior temporal gyrus contains neurons specialized for speech perception.     

Early integration of vowel and pitch processing: A mismatch negativity study

ObjectiveSeveral studies have explored the processing specificity of music and speech, but only a few have addressed the processing autonomy of their fundamental components: pitch and phonemes. Here, we examined the additivity of the mismatch negativity (MMN) indexing the early interactions between vowels and pitch when sung.MethodsEvent-related potentials (ERPs) were recorded while participants heard frequent sung vowels and rare stimuli deviating in pitch only, in vowel only, or in both pitch and vowel. The task was to watch a silent movie while ignoring the sounds.ResultsAll three types of deviants elicited both an MMN and a P3a ERP component. The observed MMNs were of similar amplitude for the three types of deviants and the P3a was larger for double deviants. The MMNs to deviance in vowel and deviance in pitch were not additive.ConclusionsThe underadditivity of the MMN responses suggests that vowel and pitch differences are processed by interacting neural networks.SignificanceThe results indicate that vowel and pitch are processed as integrated units, even at a pre-attentive level. Music-processing specificity thus rests on more complex dimensions of music and speech.     

Mismatch negativity to pitch pattern deviants in schizophrenia

Simple mismatch negativity (MMN) to infrequent pitch deviants is impaired in individuals with long‐term schizophrenia (Sz). The complex MMN elicited by pattern deviance often manifes is cut from here]‐>ts later after deviant onset than simple MMN and can ascertain deficits in abstracting relationships between stimuli. Sz exhibit reduced complex MMN, but so far this has only been measured when deviance detection relies on a grouping rule. We measured MMN to deviants in pitch‐based rules to see whether MMN is also abnormal in Sz under these conditions. Three experiments were conducted. Twenty‐seven Sz and 28 healthy matched controls (HC) participated in Experiments 1 and 2, and 24 Sz and 26 HC participated in Experiment 3. Experiment 1 was a standard pitch MMN task, and Sz showed the expected MMN reduction (~ 115 ms) in the simple pitch deviant compared to HC. Experiment 2 comprised standard groups of six tones that ascended in pitch, and deviant groups where the last tone descended in pitch. Complex MMN was late (~ 510 ms) and significantly blunted in Sz. Experiment 3 comprised standard groups of 12 tones (six tones ascending in pitch followed by six tones descending in pitch, like a scale), and deviant groups containing two repetitions of six ascending tones (the scale restarted midstream). Complex MMN was also late (~ 460 ms) and significantly blunted in Sz. These results identify a late pitch pattern deviance‐related MMN that is deficient in schizophrenia. This suggests specific deficits in later more complex deviance detection in schizophrenia for abstract patterns.     

Mismatch negativity evoked by the McGurk-MacDonald effect: a phonetic representation within short-term memory.

OBJECTIVES: The McGurk-MacDonald illusory percept is obtained by dubbing an incongruent articulatory movement on an auditory phoneme. This type of audiovisual speech perception contributes to the assessment of theories of speech perception. The mismatch negativity (MMN) reflects the detection of a deviant stimulus within the auditory short-term memory and besides an acoustic component, possesses, under certain conditions, a phonetic one. The present study assessed the existence of an MMN evoked by McGurk-MacDonald percepts elicited by audiovisual stimuli with constant auditory components. METHODS: Cortical evoked potentials were recorded using the oddball paradigm on 8 adults in 3 experimental conditions: auditory alone, visual alone and audiovisual stimulation. Obtaining illusory percepts was confirmed in an additional psychophysical condition. RESULTS: The auditory deviant syllables and the audiovisual incongruent syllables elicited a significant MMN at Fz. In the visual condition, no negativity was observed either at Fz, or at O(z). CONCLUSIONS: An MMN can be evoked by visual articulatory deviants, provided they are presented in a suitable auditory context leading to a phonetically significant interaction. The recording of an MMN elicited by illusory McGurk percepts suggests that audiovisual integration mechanisms in speech take place rather early during the perceptual processes.     

Optical imaging of temporal integration in human auditory cortex

Behavioral and physiological studies have indicated the existence of a temporal window of auditory integration (TWI), within which similar sounds are perceptually grouped. The current study exploits the combined temporal and spatial resolution of fast optical imaging (the event-related optical signal, EROS) to show that brain activity elicited by sounds within and outside the TWI differs in location and latency. In a previous event-related brain potential (ERP) study [Sable, Gratton, and Fabiani (2003) European Journal of Neuroscience, 17, 2492-2496], we found that the mismatch negativity (MMN; a brain response to acoustic irregularities) elicited by deviations in stimulus onset asynchronies (SOAs) had a unique shape when the deviant SOA was within the TWI. In the present study, we extended these ERP results using EROS. Participants heard trains of five tones. The first four tones had SOAs of 96, 192, 288 or 384 ms. The SOA of the fourth and fifth tones was either the same (standard) or one of the other three (deviant) SOAs. With a deviant SOA of 96 ms, the cortical response was approximately 2 cm anterior to responses to longer SOA deviants, and was followed by a later response that was absent in the other conditions. Similarly to the electrical MMN, the optical mismatch response amplitudes were proportional to the magnitude of interval deviance. These results, in combination with our previous findings, indicate that the temporal integration of sounds is reflected in cortical mismatch responses that differ from the typical response to interval deviance.     

Left hemispheric dipole locations of the neuromagnetic mismatch negativity to frequency,intensity and duration deviants

The aim of the current study was to differentiate the sources of neuromagnetic mismatch negativity (MMNm) to deviants of different features. For this purpose, the MMNm of twenty-one healthy subjects (seven males) were recorded left-hemispherically. Subjects were stimulated monaurally in an oddball paradigm with standard tones of 1000 Hz and three different kinds of mismatch tones (frequency, duration and intensity deviants). Data analysis revealed mean MMNm dipole locations anterior, inferior and more medial than the N100m dipoles. The mean difference between the N100m and MMNm dipoles was in the range of up to 6 mm in one dimension. The dipole locations of all three kinds of deviants differed significantly from each other. The MMNm dipoles of both frequency and duration deviants were found to be significantly inferior to the corresponding source of intensity deviants, while the MMNm dipoles of duration and frequency deviants significantly differed in anterior-posterior direction. This differentiation between sources emphasizes the importance of feature analysis in MMN(m) generation.     

Enhanced passive and active processing of syllables in musician children

The aim of this study was to examine the influence of musical expertise in 9-year-old children on passive (as reflected by MMN) and active (as reflected by discrimination accuracy) processing of speech sounds. Musician and nonmusician children were presented with a sequence of syllables that included standards and deviants in vowel frequency, vowel duration, and VOT. Both the passive and the active processing of duration and VOT deviants were enhanced in musician compared with nonmusician children. Moreover, although no effect was found on the passive processing of frequency, active frequency discrimination was enhanced in musician children. These findings are discussed in terms of common processing of acoustic features in music and speech and of positive transfer of training from music to the more abstract phonological representations of speech units (syllables).     

Delayed mismatch field for speech and non-speech sounds in children with autism

This study investigated the magnetic mismatch field elicited by changes in streams of vowels or spectrally matched tones in children with autism spectrum disorder (ASD) relative to children with typical development to explore whether impaired sound discrimination may contribute to language impairments in autism spectrum disorder. Using magnetoencephalography, we recorded evoked neural activity to 300-Hz and 700-Hz tones (and /u/ and /a/ vowels) presented in an oddball paradigm with deviant stimuli (15%) occurring within a train of standards (85%). The magnetic mismatch field was robustly observed in both groups, but children with autism spectrum disorder demonstrated a significantly delayed magnetic mismatch field compared with typically developing peers. Difficulty parsing transient differences in sounds may lead to impaired acoustic or phonological representations and subsequent language impairment in autism spectrum disorder.