Magnetic Mismatch Field Research Articles

A Minimum Temporal Window for Direction Detection of Frequency-Modulated Sweeps: A Magnetoencephalography Study.

The ability to rapidly encode the direction of frequency contour contained in frequency-modulated (FM) sweeps is essential for speech processing, music appreciation, and conspecific communications. Psychophysical evidence points to a common temporal window threshold for human listeners in processing rapid changes in frequency glides. No neural evidence has been provided for the existence of a cortical temporal window threshold underlying the encoding of rapid transitions in frequency glides. The present magnetoencephalography study used the cortical mismatch negativity activity (MMNm) to investigate the minimum temporal window required for detecting different magnitudes of directional changes in frequency-modulated sweeps. A deviant oddball paradigm was used in which directional upward or downward frequency sweep serves as the standard and the same type of sweep with the opposite direction serves as its deviant. Stimuli consisted of unidirectional linear frequency-sweep complexes that swept across speech-relevant frequency bands in durations of 10, 20, 40, 80, 160, and 320 ms (with corresponding rates of 50, 25, 12.5, 6.2, 3.1, 1.5 oct/s). The data revealed significant magnetic mismatch field responses across all sweep durations, with slower-rate sweeps eliciting larger MMNm responses. A greater temporally related enhancement in MMNm response was obtained for rising but not falling frequency sweep contours. A hemispheric asymmetry in the MMNm response pattern was observed corresponding to the directionality of frequency sweeps. Contrary to psychophysical findings, we report a temporal window as short as 10 ms sufficient to elicit a robust MMNm response to a directional change in speech-relevant frequency contours. The results suggest that auditory cortex requires extremely brief temporal window to implicitly differentiate a dynamic change in frequency of linguistically relevant pitch contours. That the brain is extremely sensitive to fine spectral changes contained in speech-relevant glides provides cortical evidence for the ecological importance of FM sweeps in speech processing.

Abnormal Auditory Mismatch Fields in Children and Adolescents With 16p11.2 Deletion and 16p11.2 Duplication

BackgroundIndividuals with either deletion or duplication of the BP4–BP5 segment of chromosome 16p11.2 have varied behavioral phenotypes that may include autistic features, mild to moderate intellectual disability, and/or language impairment. However, the neurophysiological correlates of auditory language discrimination processing in individuals with 16p11.2 deletion and 16p11.2 duplication have not been investigated. MethodsMagnetoencephalography was used to measure magnetic mismatch fields (MMFs) arising from the left and right superior temporal gyrus during an auditory oddball paradigm with vowel stimuli (/a/ and /u/) in children and adolescents with 16p11.2 deletion or 16p11.2 duplication and in typically developing peers. One hundred twenty-eight participants ranging from 7 to 17 years of age were included in the final analysis (typically developing: n = 61, 12.08 ± 2.50 years of age; 16p11.2 deletion: n = 45, 11.28 ± 2.51 years of age; and 16p11.2 duplication: n = 22, 10.73 ± 2.49 years of age). ResultsDelayed MMF latencies were found in both 16p11.2 deletion and 16p11.2 duplication groups compared with typically developing subjects. In addition, these delayed MMF latencies were associated with language and cognitive ability, with prolonged latency predicting greater impairment. ConclusionsOur findings suggest that auditory MMF response delays are associated with clinical severity of language and cognitive impairment in individuals with either 16p11.2 deletion or 16p11.2 duplication, indicating a correlate of their shared/overlapping behavioral phenotype (and not a correlate of gene dosage).

Lack of correlation between phonetic magnetic mismatch field and plasma d-serine levels in humans

ObjectiveUncovering molecular bases for auditory language processing in the human brain is a fundamental scientific challenge. The power and latency of the magnetic mismatch field (MMF) elicited by phoneme change, which are magnetoencephalographic indices of language function in its early stage of information processing, are theoretically thought to be modulated by N-methyl-d-aspartate-type glutamate receptor (NMDAR) function, but no study has yet assessed this possibility. We have thus sought to demonstrate an association between phonetic MMF power/latency and levels of plasma d-serine, an intrinsic co-agonist of glycine binding sites on NMDAR, in adults. MethodsThe MMF response to phoneme changes was recorded using 204-channel magnetoencephalography in 61 healthy, right-handed, Japanese adults. Plasma levels of d- and l-serine were measured for each participant. ResultsWe did not find a significant correlation between MMF power/latency and plasma serine levels. ConclusionsDespite a sufficient sample size, we failed to find an association between the physiological markers of the early stage of information processing of language in the auditory cortex and biomarkers indexing glutamatergic function. SignificanceOur study did not indicate that a molecular index of glutamatergic function could be a surrogate marker for the early stage of information processing of language in humans.

Altered human voice processing in the frontal cortex and a developmental language delay in 3- to 5-year-old children with autism spectrum disorder

The inferior frontal and superior temporal areas in the left hemisphere are crucial for human language processing. In the present study, we investigated the magnetic mismatch field (MMF) evoked by voice stimuli in 3- to 5-year-old typically developing (TD) children and children with autism spectrum disorder (ASD) using child-customized magnetoencephalography (MEG). The children with ASD exhibited significantly decreased activation in the left superior temporal gyrus compared with the TD children for the MMF amplitude. If we classified the children with ASD according to the presence of a speech onset delay (ASD - SOD and ASD - NoSOD, respectively) and compared them with the TD children, both ASD groups exhibited decreased activation in the left superior temporal gyrus compared with the TD children. In contrast, the ASD - SOD group exhibited increased activity in the left frontal cortex (i.e., pars orbitalis) compared with the other groups. For all children with ASD, there was a significant negative correlation between the MMF amplitude in the left pars orbitalis and language performance. This investigation is the first to show a significant difference in two distinct MMF regions in ASD – SOD children compared with TD children.

Learning transforms functional organization for Mandarin lexical tone discrimination in the brain: Evidence from a MEG experiment on second language learning

Abstract Brain neuroplasticity refers to anatomical changes and functional reorganization in the brain as the results of daily experience and new learning, and thus, should have profound implications for the changes in brain processing during and after bilingual learning. By using a MEG experiment of magnetic mismatch negativity (MMN)/magnetic mismatch field (MMNm) paradigm, the present study examined the brain wave patterns of beginning learners of learning Chinese as a second language (CSL), who enrolled in a short term digital learning program, and were found to have improved sensitivity in discrimination for lexical tones by developing a left lateralized dominance for processing Chinese lexical tones, just like native Mandarin speakers. In the experiment, the measurements of MMNm, with the contrast between large deviant T3/T1 and between small deviant T3/T2, were computed to index the changed patterns of brain processing before and after learning. Results of the MMNm data indicated that activation for large deviant contrast T3/T1 elicited earlier and significantly larger MMN than that of the small deviant contrast T3/T2, which is in line with previous studies done on native Chinese speakers. More importantly, in the comparison of pre-test and post-test time course, the amplitude of MMNm showed a significant increase in the left hemisphere after learning. The evidence indicated clearly a learning effect in the perception of linguistic features and a left lateralized neural network of processing Mandarin lexical tones. Moreover, in the source analysis, the left lateralized patterns of prefrontal generator (i.e., insula) and generator of auditory cortex (i.e., Heschl's Gyrus) changed after learning, which is also consistent with the native Mandarin speaker's response patterns. In sum, the present study provides neural evidence for a functional reorganization in the brains of second language learners, transforming the CSL learners to behave like native speakers in the perception of lexical tones even after just a short-term and non-specific training program.

The neural generators of the mismatch responses to Mandarin lexical tones: An MEG study

The present magnetoencephalography study used the cortically constrained minimum-norm estimates of human brain activity to elucidate functional roles of neural generators for detecting different magnitudes of lexical tones changes. A multiple-deviant oddball paradigm was used in which the syllable “yi” with a low-dipping tone (T3) was the common standard sound and the same syllable with a high-level tone (T1) or a high-rising tone (T2) were the large and small deviant sounds, respectively. The data revealed a larger magnetic mismatch field (MMNm) for large deviant in the left hemisphere. The source analysis also confirmed that the MMNm to lexical tone changes was generated in bilateral superior temporal gyri and only the large deviant revealed left lateralization. A set of frontal generators was activated at a later time and revealed differential sensitivities to the degree of deviance. The left anterior insula, the right anterior cingulate cortex, and the right ventral orbital frontal cortex were activated when detecting a large deviant, whereas the right frontal-opercular region was sensitive to the small deviant. These frontal generators were thought to be associated with various top-down mechanisms for attentional modulation. The time frequency (TF) analysis showed that large deviants yielded large theta band (5–7Hz) activity over the left anterior scalp and the left central scalp, while small deviants yielded large alpha band activity (9–11Hz) over the posterior scalp. The results of TF analyses implied that mechanisms of working memory and functional inhibition involved in the processes of acoustic change detection.

Effects of Metabotropic Glutamate Receptor 3 Genotype on Phonetic Mismatch Negativity

BackgroundThe genetic and molecular basis of glutamatergic dysfunction is one key to understand schizophrenia, with the identification of an intermediate phenotype being an essential step. Mismatch negativity (MMN) or its magnetic counterpart, magnetic mismatch field (MMF) is an index of preattentive change detection processes in the auditory cortex and is generated through glutamatergic neurotransmission. We have previously shown that MMN/MMF in response to phoneme change is markedly reduced in schizophrenia. Variations in metabotropic glutamate receptor (GRM3) may be associated with schizophrenia, and has been shown to affect cortical function. Here we investigated the effect of GRM3 genotypes on phonetic MMF in healthy men.MethodsMMF in response to phoneme change was recorded using magnetoencephalography in 41 right-handed healthy Japanese men. Based on previous genetic association studies in schizophrenia, 4 candidate SNPs (rs6465084, rs2299225, rs1468412, rs274622) were genotyped.Results GRM3 rs274622 genotype variations significantly predicted MMF strengths (p = 0.009), with C carriers exhibiting significantly larger MMF strengths in both hemispheres compared to the TT subjects.ConclusionsThese results suggest that variations in GRM3 genotype modulate the auditory cortical response to phoneme change in humans. MMN/MMF, particularly those in response to speech sounds, may be a promising and sensitive intermediate phenotype for clarifying glutamatergic dysfunction in schizophrenia.

Auditory Magnetic Mismatch Field Latency: A Biomarker for Language Impairment in Autism

Auditory processing abnormalities are frequently observed in autism spectrum disorders (ASD), and these abnormalities may have sequelae in terms of clinical language impairment (LI). The present study assessed associations between language impairment and the amplitude and latency of the superior temporal gyrus magnetic mismatch field (MMF) in response to changes in an auditory stream of tones or vowels. Fifty-one children with ASD, and 27 neurotypical control subjects, all aged 6 to 15 years, underwent neuropsychological evaluation, including tests of language function, as well as magnetoencephalographic recording during presentation of tones and vowels. The MMF was identified in the difference waveform obtained from subtraction of responses to standard from deviant stimuli. Magnetic mismatch field latency was significantly prolonged (p < .001) in children with ASD, compared with neurotypical control subjects. Furthermore, this delay was most pronounced (∼50 msec) in children with concomitant LI, with significant differences in latency between children with ASD with LI and those without (p < .01). Receiver operator characteristic analysis indicated a sensitivity of 82.4% and specificity of 71.2% for diagnosing LI based on MMF latency. Neural correlates of auditory change detection (the MMF) are significantly delayed in children with ASD, and especially those with concomitant LI, suggesting a neurobiological basis as well as a clinical biomarker for LI in ASD.

Magnetic Mismatch Field Latency Response as a Neuromagnetic Biomarker of Language Impairment in Autism Spectrum Disorder

Magnetic Mismatch Field Latency Response as a Neuromagnetic Biomarker of Language Impairment in Autism Spectrum Disorder

A magnetoencephalographic study on auditory processing of native and nonnative fricative contrasts in Polish and German listeners

Linguistic experience shapes auditory processing of speech sounds as indicated by the mismatch negativity (MMN). In the current study, magnetic mismatch fields (MMNm) in response to native and nonnative fricative-vowel syllables were recorded, using whole-head magnetoencephalography (MEG). Earlier difference waves were enhanced in the left hemisphere in native listeners for fricatives with rather subtle acoustic differences in frication and pronounced acoustic differences in the transition to the vowel. For nonnative subjects, difference waves were at first stronger in the right hemisphere for these contrasts. Left hemispheric MMNms only occurred later in nonnative participants. The results are discussed in relation to previous studies suggesting lateralization of speech sound processing.

Objective examination for two-point stimulation using a somatosensory oddball paradigm: An MEG study

ObjectiveTo establish an objective two-point discrimination test using magnetoencephalography (MEG). MethodsFirst, we determined the discrimination threshold (DT) of the two-points. In the first experiment, we applied 0.9DT as standard stimuli, and 0.8DT, 1.1DT and 2DT as deviant stimuli in Conditions 1, 2 and 3, respectively. In the second experiment, we used 2DT and 0.9DT as the standard and deviant stimuli, respectively, in Condition 1. We applied two-stimuli that subjects felt as definitely one point or two-points in Condition 2 and 3, respectively. ResultsIn the first experiment, the components peaking around 30–70 and 150–250ms following deviant stimuli were significantly larger than those following standard stimuli. Considering the peak latency, these components seem consistent with the magnetic mismatch field (MMF). In the second experiment, the MMF was recorded only in Condition 1. Therefore, it is considered that the MMF was recorded only when subjects automatically discriminate one point from two-points stimuli. ConclusionsThis novel method can be used in neurophysiological two-point discrimination tests without the need to rely on the examiners’ skills and subjects’ reactions. SignificanceWe confirmed that our new method could be used for the objective examination of two-point spatial discrimination.

Delayed automatic detection of change in speech sounds in adults with autism: A magnetoencephalographic study

Objective Autism is a form of pervasive developmental disorder in which dysfunction in interpersonal relationships and communication is fundamental. This study evaluated neurophysiological abnormalities at the basic level of language processing, i.e. automatic change detection of speech and non-speech sounds, using magnetoencephalographic recording of mismatch response elicited by change in vowels and tones. Methods The auditory magnetic mismatch field (MMF) was evaluated in 9 adults with autism and 19 control subjects using whole-head magnetoencephalography. The MMF in response to the duration change of a pure tone or vowel /a/ and that in response to across-phoneme change between vowels /a/ and /o/, were recorded. Results The groups were not significantly different in MMF power under any conditions. However, the autism group showed a left-biased latency prolongation of the MMF particularly under the across-phoneme change condition, and this latency delay was significantly associated with greater symptom severity. Conclusions These results suggest that adults with autism are associated with delayed processing for automatic change detection of speech sounds. These electrophysiological abnormalities at the earliest level of information processing may contribute to the basis for language deficits observed in autism. Significance These results provide the first evidence for delayed latency of phonetic MMF in adults with autism.

Comparison between mismatch negativity amplitude and magnetic mismatch field strength in normal adults

The auditory mismatch negativity (MMN) or its magnetic counterpart (magnetic mismatch field, MMF) has been widely used to assess the ability of stimulus-driven change detection process in humans. The authors evaluated the similarity of inter-individual variation of the response strength between MMN and MMF recordings. Three types of MMN or MMF were recorded in ten healthy subjects: change in duration of pure-tone stimuli, change in duration of the Japanese vowel /a/, and difference between the Japanese vowels /a/ and /o/. There was no significant correlation between MMN amplitude and MMF strength under any condition and in either hemisphere. These results suggest that widely used indices of MMN in the two technologies, i.e., EEG-amplitude and MEG–ECD may not be proportional in an individual. To further clarify the differential significance of recording MMN/MMF may be important to establish MMN/MMF as clinical indices of individual ability of preattentive stage of auditory processing.

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.

Structural and functional abnormalities of the auditory cortex in schizophrenia

We used the combination of magnetic resonance imaging (MRI), event-related potentials (ERPs), and magnetoencephalography (MEG) to track structural and functional abnormalities of the superior temporal gyrus (STG) and its subdivisions of Heschl's gyrus (HG; primary auditory cortex) and planum temporale (PT; language-related association cortex) in schizophrenia. We found a significantly progressive decrease of left posterior STG gray matter volume at 1.5-year follow-up in first-episode patients with schizophrenia. When STG was divided into HG and PT, both showed a similar degree of volume reduction over time in patients with schizophrenia. Structural abnormalities of HG at the first-hospitalization and their progression were tightly coupled with the amplitude of mismatch negativity (MMN) elicited by tones, an ERP index of auditory sensory memory with the major generator in HG, in patients with schizophrenia. Moreover, in independent samples of schizophrenia, we showed that patients were associated with pronounced reduction of MMN amplitude elicited by speech sounds and its MEG counterpart (magnetic mismatch field, MMF). Finally, we found a significant correlation between MMF powers elicited by speech sounds and gray matter volumes of PT in patients with schizophrenia but not in control subjects. These converging results suggest a presence of progressive process in the structure and function of the auditory cortex in schizophrenia.

Human auditory evoked mismatch field amplitudes vary as a function of vowel duration in healthy first-language speakers

Previous auditory studies demonstrated that vowel shortening elicited a more prominent mismatch component than its lengthening in event-related potentials (ERP) and magnetoencephalography (MEG). Based on these findings, the current study investigated whether the magnetic mismatch field (MMF) component would be generated by vowel shortening of various degrees to determine a neuronal response threshold of pre-attentive deviation detection. Behavioral pre-test data revealed that while listening to Japanese short-duration (100%: reference), long-duration (180%), and other in-between duration-synthesized types, healthy native speakers of Japanese failed to clearly categorize 140–124% durations as either short or long words, while categorizing 108–116% durations as short words and 148–172% durations as long. Following these results, MEG responses were recorded with a whole-head 148-channel magnetometer, as subjects listened to 100% standard and five deviant durations (124, 132, 140, 148, 180%). MEG results showed that the above-32% duration decrements (180→100%, 148→100%) elicited a more prominent MMF than the others, the MMF amplitudes increasing linearly to the degree of duration deviance, and that neuronal responses correlated with behavioral word-categorization accuracy.

Abnormal association between reduced magnetic mismatch field to speech sounds and smaller left planum temporale volume in schizophrenia

Schizophrenia is associated with language-related dysfunction. A previous study [Schizophr. Res. 59 (2003c) 159] has shown that this abnormality is present at the level of automatic discrimination of change in speech sounds, as revealed by magnetoencephalographic recording of auditory mismatch field in response to across-category change in vowels. Here, we investigated the neuroanatomical substrate for this physiological abnormality. Thirteen patients with schizophrenia and 19 matched control subjects were examined using magnetoencephalography (MEG) and high-resolution magnetic resonance imaging (MRI) to evaluate both mismatch field strengths in response to change between vowel /a/ and /o/, and gray matter volumes of Heschl's gyrus (HG) and planum temporale (PT). The magnetic global field power of mismatch response to change in phonemes showed a bilateral reduction in patients with schizophrenia. The gray matter volume of left planum temporale, but not right planum temporale or bilateral Heschl's gyrus, was significantly smaller in patients with schizophrenia compared with that in control subjects. Furthermore, the phonetic mismatch strength in the left hemisphere was significantly correlated with left planum temporale gray matter volume in patients with schizophrenia only. These results suggest that structural abnormalities of the planum temporale may underlie the functional abnormalities of fundamental language-related processing in schizophrenia.

Magnetic mismatch fields elicited by vowel duration and pitch changes in Japanese words in humans: comparison between native- and non-speakers of Japanese

Previous event-related brain potential research showed that mismatch negativity was elicited by phoneme contrasts in fluent second language (L2) learners, but not in non-speakers of L2. The present study tested whether the magnetic mismatch field (MMF) would be elicited in response to temporal and spectral changes in three Japanese synthesized words for both native- and non-speakers of Japanese. Magnetoencephalography responses were recorded with a dual 37-channel gradiometer. Unlike short-to-long vowel duration and falling-to-level pitch changes, long-to-short duration and level-to-falling pitch changes elicited a prominent MMF bilaterally for both groups, peaking at around 100 ms after change onset for duration and 200 ms for pitch. The MMF component is sensitive to vowel shortening rather than lengthening and to pitch falling rather than leveling. Automatic detection of changes in vowel shortening and pitch falling is a useful index of language-non-specific auditory memory traces.

Diminished auditory mismatch fields in dyslexic adults.

Electroencephalographic studies have demonstrated smaller auditory responses to infrequent deviances of speech and nonspeech sounds in dyslexic than normal-reading subjects. We used a whole-scalp neuromagnetometer to study selectively reactivity of the auditory cortices to sound deviances in 8 dyslexic and 11 normal-reading adults. Within a monotonous sequence of 50-millisecond 1000 Hz binaural tones, tones of 920 and 1080 Hz occurred with 7% probability each. Magnetic mismatch fields, elicited by the stimulus deviances, were diminished in the left hemisphere of the dyslexic subjects. The results indicate deficient change detection in the left auditory cortex of right-handed dyslexic adults.

Processing of dynamic aspects of speech and non-speech stimuli: a whole-head magnetoencephalography study

Clinical and experimental data indicate higher proficiency of the left hemisphere in encoding dynamic acoustic events such as rapid formant transitions (30–40 ms) that distinguish consonant–vowel syllables such as /ba/ or /da/. In order to further elucidate the underlying neurophysiological mechanisms, discrimination of /bi/-like formant transitions of variable duration (18, 36, 54, or 72 ms) from a steady-state /i/-like vowel was investigated by means of whole-head magnetoencephalography (MEG) both during visual distraction and selective attention. Voiced speech-like as well as unvoiced non-speech stimuli, matched for spectral envelope, served as test materials. Based on an oddball design, magnetic mismatch fields (MMF) were determined during an early (170–210 ms) and a late (230–290 ms) time window. Selective attention toward the deviant events resulted in enhanced MMFs particularly within the left hemisphere, indicating attention-dependent left-lateralized processing of dynamic auditory events across both the speech and non-speech domains. Perceptual discrimination improved along with transient lengthening. Accordingly, early MMF was, as a rule, enlarged in case of longer as compared to shorter transients. The 36-ms transitions yielded attention- and voicing-dependent deviations from the linear regression of MMF strength on transition duration. Considering the predominance of 30- to 40-ms formant transients across the world’s languages, these findings indicate an adaptation or predisposition of the human perceptual system to the spectral/temporal characteristics of prototypical speech sounds. Signal voicing had no significant main effect on MMF strength despite superior perceptual performance in case of voiced as compared to voiceless target stimuli.