Change and novelty detection in speech and non-speech sound streams

Cortical Generators and Connections Underlying Phoneme Perception: A Mismatch Negativity and P300 Investigation

The cortical generators of the pure tone MMN and P300 have been thoroughly studied. Their nature and interaction with respect to phoneme perception, however, is poorly understood. Accordingly, the cortical sources and functional connections that underlie the MMN and P300 in relation to passive and active speech sound perception were identified. An inattentive and attentive phonemic oddball paradigm, eliciting a MMN and P300 respectively, were administered in 60 healthy adults during simultaneous high-density EEG recording. For both the MMN and P300, eLORETA source reconstruction was performed. The maximal cross-correlation was calculated between ROI-pairs to investigate inter-regional functional connectivity specific to passive and active deviant processing. MMN activation clusters were identified in the temporal (insula, superior temporal gyrus and temporal pole), frontal (rostral middle frontal and pars opercularis) and parietal (postcentral and supramarginal gyrus) cortex. Passive discrimination of deviant phonemes was aided by a network connecting right temporoparietal cortices to left frontal areas. For the P300, clusters with significantly higher activity were found in the frontal (caudal middle frontal and precentral), parietal (precuneus) and cingulate (posterior and isthmus) cortex. Significant intra- and interhemispheric connections between parietal, cingulate and occipital regions constituted the network governing active phonemic target detection. A predominantly bilateral network was found to underly both the MMN and P300. While passive phoneme discrimination is aided by a fronto-temporo-parietal network, active categorization calls on a network entailing fronto-parieto-cingulate cortices. Neural processing of phonemic contrasts, as reflected by the MMN and P300, does not appear to show pronounced lateralization to the language-dominant hemisphere.

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.

Characteristics of different Mandarin pronunciation element perception: evidence based on a multifeature paradigm for recording MMN and P3a components of phonemic changes in speech sounds

Background

As a tonal language, Mandarin Chinese has the following pronunciation elements for each syllable: the vowel, consonant, tone, duration, and intensity. Revealing the characteristics of auditory-related cortical processing of these different pronunciation elements is interesting.

Methods

A Mandarin pronunciation multifeature paradigm was designed, during which a standard stimulus and five different phonemic deviant stimuli were presented. The electroencephalogram (EEG) data were recorded with 256-electrode high-density EEG equipment. Time-domain and source localization analyses were conducted to demonstrate waveform characteristics and locate the sources of the cortical processing of mismatch negativity (MMN) and P3a components following different stimuli.

Results

Vowel and consonant differences elicited distinct MMN and P3a components, but tone and duration differences did not. Intensity differences elicited distinct MMN components but not P3a components. For MMN and P3a components, the activated cortical areas were mainly in the frontal-temporal lobe. However, the regions and intensities of the cortical activation were significantly different among the components for the various deviant stimuli. The activated cortical areas of the MMN and P3a components elicited by vowels and consonants seemed to be larger and show more intense activation.

Conclusion

The auditory processing centers use different auditory-related cognitive resources when processing different Mandarin pronunciation elements. Vowels and consonants carry more information for speech comprehension; moreover, more neurons in the cortex may be involved in the recognition and cognitive processing of these elements.

Beneficial effects of a music listening intervention on neural speech processing in 0-28-month-old children at risk for dyslexia

Familial risk for developmental dyslexia can compromise auditory and speech processing and subsequent language and literacy development. According to the phonological deficit theory, supporting phonological development during the sensitive infancy period could prevent or ameliorate future dyslexic symptoms. Music is an established method for supporting auditory and speech processing and even language and literacy, but no previous studies have investigated its benefits for infants at risk for developmental language and reading disorders. We pseudo-randomized N∼150 infants at risk for dyslexia to vocal or instrumental music listening interventions at 0-6 months, or to a no-intervention control group. Music listening was used as an easy-to-administer, cost-effective intervention in early infancy. Mismatch responses (MMRs) elicited by speech-sound changes were recorded with electroencephalogram (EEG) before (at birth) and after (at 6 months) the intervention and at a 28 months follow-up. We expected particularly the vocal intervention to promote phonological development, evidenced by enhanced speech-sound MMRs and their fast maturation. We found enhanced positive MMR amplitudes in the vocal music listening intervention group after but not prior to the intervention. Other music activities reported by parents did not differ between the three groups, indicating that the group effects were attributable to the intervention. The results speak for the use of vocal music in early infancy to support speech processing and subsequent language development in infants at developmental risk. RESEARCH HIGHLIGHTS: Dyslexia-risk infants were pseudo-randomly assigned to a vocal or instrumental music listening intervention at home from birth to 6 months of age. Neural mismatch responses (MMRs) to speech-sound changes were enhanced in the vocal music intervention group after but not prior to the intervention. Even passive vocal music listening in early infancy can support phonological development known to be deficient in dyslexia-risk.

Neural phoneme discrimination in variable speech in newborns - Associations with dyslexia risk and later language skills

A crucial skill in infant language acquisition is learning of the native language phonemes. This requires the ability to group complex sounds into distinct auditory categories based on their shared features. Problems in phonetic learning have been suggested to underlie language learning difficulties in dyslexia, a developmental reading-skill deficit. We investigated auditory abilities important for language acquisition in newborns with or without a familial risk for dyslexia with electrophysiological mismatch responses (MMRs). We presented vowel changes in a sequence of acoustically varying vowels, requiring grouping of the stimuli to two phoneme categories. The vowel changes elicited an MMR which was significantly diminished in infants whose parents had the most severe dyslexia in our sample. Phoneme-MMR amplitude and its hemispheric lateralization were associated with language test outcomes assessed at 28 months, an age at which it becomes possible to behaviourally test children and several standardized tests are available. In addition, statistically significant MMRs to violations of a complex sound-order rule were only found in infants without dyslexia risk, but these results are very preliminary due to small sample size. The results demonstrate the relevance of the newborn infants' readiness for phonetic learning for their emerging language skills. Phoneme extraction difficulties in infants at familial risk may contribute to the phonological deficits observed in dyslexia.

English and Mandarin native speakers' cue-weighting of lexical stress: Results from MMN and LDN

Past research on how listeners weight stress cues such as pitch, duration and intensity has reported two inconsistent patternss: listeners' weighting conforms to 1) their native language experience (e.g., language rhythmicity, lexical tone), and 2) a general "iambic-trochaic law" (ITL), favouring innate sound groupings in cue perception. This study aims to tease apart the above effects by investigating the weighting of pitch, duration and intensity cues in stress-timed (Australian English) and non-stress-timed and tonal (Taiwan Mandarin) language speaking adults using a mismatch negativity (MMN) multi-feature paradigm. Results show effects that can be explained by language-specific rhythmic influence, but only partially by the ITL. Moreover, these findings revealed cross-linguistic differences indexed by both MMN and late discriminative negativity (LDN) responses at cue and syllable position levels, and thus call for more sophisticated perspectives for existing cue-weighting models.

Developmental organization of neural dynamics supporting auditory perception

Purpose:

A prominent view of language acquisition involves learning to ignore irrelevant auditory signals through functional reorganization, enabling more efficient processing of relevant information. Yet, few studies have characterized the neural spatiotemporal dynamics supporting rapid detection and subsequent disregard of irrelevant auditory information, in the developing brain. To address this unknown, the present study modeled the developmental acquisition of cost-efficient neural dynamics for auditory processing, using intracranial electrocorticographic responses measured in individuals receiving standard-of-care treatment for drug-resistant, focal epilepsy. We also provided evidence demonstrating the maturation of an anterior-to-posterior functional division within the superior-temporal gyrus (STG), which is known to exist in the adult STG.

Methods:

We studied 32 patients undergoing extraoperative electrocorticography (age range: eight months to 28 years) and analyzed 2,039 intracranial electrode sites outside the seizure onset zone, interictal spike-generating areas, and MRI lesions. Patients were given forward (normal) speech sounds, backward-played speech sounds, and signal-correlated noises during a task-free condition. We then quantified sound processing-related neural costs at given time windows using high-gamma amplitude at 70–110 Hz and animated the group-level high-gamma dynamics on a spatially normalized three-dimensional brain surface. Finally, we determined if age independently contributed to high-gamma dynamics across brain regions and time windows.

Results:

Group-level analysis of noise-related neural costs in the STG revealed developmental enhancement of early high-gamma augmentation and diminution of delayed augmentation. Analysis of speech-related high-gamma activity demonstrated an anterior-to-posterior functional parcellation in the STG. The left anterior STG showed sustained augmentation throughout stimulus presentation, whereas the left posterior STG showed transient augmentation after stimulus onset. We found a double dissociation between the locations and developmental changes in speech sound-related high-gamma dynamics. Early left anterior STG high-gamma augmentation (i.e., within 200 ms post-stimulus onset) showed developmental enhancement, whereas delayed left posterior STG high-gamma augmentation declined with development.

Conclusions:

Our observations support the model that, with age, the human STG refines neural dynamics to rapidly detect and subsequently disregard uninformative acoustic noises. Our study also supports the notion that the anterior-to-posterior functional division within the left STG is gradually strengthened for efficient speech sound perception after birth.

Auditory event-related potentials index faster processing of natural speech but not synthetic speech over nonspeech analogs in children

Given the crucial role of speech sounds in human language, it may be beneficial for speech to be supported by more efficient auditory and attentional neural processing mechanisms compared to nonspeech sounds. However, previous event-related potential (ERP) studies have found either no differences or slower auditory processing of speech than nonspeech, as well as inconsistent attentional processing. We hypothesized that this may be due to the use of synthetic stimuli in past experiments. The present study measured ERP responses during passive listening to both synthetic and natural speech and complexity-matched nonspeech analog sounds in 22 8-11-year-old children. We found that although children were more likely to show immature auditory ERP responses to the more complex natural stimuli, ERP latencies were significantly faster to natural speech compared to cow vocalizations, but were significantly slower to synthetic speech compared to tones. The attentional results indicated a P3a orienting response only to the cow sound, and we discuss potential methodological reasons for this. We conclude that our results support more efficient auditory processing of natural speech sounds in children, though more research with a wider array of stimuli will be necessary to confirm these results. Our results also highlight the importance of using natural stimuli in research investigating the neurobiology of language.

Brain responses to change in phonological structures of varying complexity in children and adults

Language-related change-detection processes are often investigated using syllables that are very simple in terms of phonological structure. However, phonological complexity is known to be challenging for young typically developing children and pathological populations. We investigated brain correlates of phonological processing and their age-related changes with a passive change-detection protocol including stimuli of varying phonological complexity, which allowed comparing responses to simple and complex phonological deviancies. Mismatch Negativity (MMN) and Late Discriminative Negativity (LDN) responses were recorded in both school-age children (n = 22) and adults (n = 24). MMN was similar for simple and complex phonological deviancy in both groups, whereas LDN appeared to be modulated by phonological complexity, albeit with different patterns according to age. In response to complex phonological change, children displayed a larger LDN response with a typical fronto-central scalp distribution, while adults showed an additional right-posterior activity but no larger amplitude than for simple change. Thus, LDN appears to be a good electrophysiological index of phonological complexity processing. This study validated the use of the LDN through this protocol for the investigation of phonological complexity processing throughout the development.

P300 indicates context-dependent change in speech quality beyond phonological change

OBJECTIVE

Non-invasive physiological methods like electroencephalography (EEG) are increasingly employed to assess human information processing during exposure to multimedia signals. In the quality engineering field, previous research has promoted the utility of the P300 event-related brain potential (ERP) component for indicating variation in quality perception. The present study provides a starting point to test whether the P300 and its two subcomponents, P3a and P3b, are truly reflective of changes in the perceived quality of transmitted speech signals given the presence of other, quality-unrelated changes in acoustic stimulation.

APPROACH

High-quality and degraded variants of spoken words were presented in a two-feature oddball task, which required participants to actively respond to rarely occurring 'target' stimuli within a series of frequent 'standard' stimuli, thereby eliciting ERP waveforms. Target presentations involved either single quality changes or concurrent double changes in quality and the initial phoneme.

MAIN RESULTS

In case additional phonological change was present, only varying quality of standard stimuli caused significant modulations in P3a and P3b characteristics (N  =  32). Thus, the formation of different short-term quality references exerted a persisting influence on the auditory processing of transmitted speech.

SIGNIFICANCE

The obtained results elucidate the importance of contextual and content-related influencing factors for proving the validity of the P300 as a psychophysiological indicator of speech quality change. Associated questions regarding the transfer of ERP-based quality assessment into more practically relevant measurement contexts are discussed.

Emotional speech processing deficits in bipolar disorder: The role of mismatch negativity and P3a

BACKGROUND

Deficits in emotional prosody processing have been observed in bipolar disorder (BD). While recent neural studies have explored impaired processing of facial expressions, little is known about deficits in emotional speech processing, or the specific stages of processing at which they occur. This study examined if pre-attentive detection and attention to emotional speech is impaired in BD, relative to healthy individuals.

METHODS

The EEG data was collected from 14 individuals with BD and 14 healthy control (HC) participants while the auditory stimuli was presented via a passive three-stimulus oddball sequence which included emotionally (neutral, happy, sad) spoken syllables and acoustically matched nonvocal tones. Event-related potentials (ERPs) were evaluated in terms of Mismatch Negativity (MMN) and P3a (event-related potentials signals).

RESULTS

Individuals with BD showed normal MMN amplitude, but significantly delayed MMN latency and reduced P3a amplitude in response to the emotional syllables compared to HC.

LIMITATIONS

Small sample size, lack of control of psychopharmacological intervention and no inclusion of an affective prosody-labelling task.

CONCLUSIONS

The finding that changes in emotional speech prosody in the pre-attentive stages of processing (MMN) were unimpaired in individuals with BD; while automatic orientation towards emotionally salient speech (P3a) was reduced compared to HC, suggests that vocal emotional cues may not be recognised as salient by individuals with BD, resulting in fewer attentional resources allocation to further processing. This may lead to poorer integration of auditory emotional cues and other sensory information and negatively impact interpersonal and psychosocial functions.

Understanding developmental language disorder - the Helsinki longitudinal SLI study (HelSLI): a study protocol

BACKGROUND

Developmental language disorder (DLD, also called specific language impairment, SLI) is a common developmental disorder comprising the largest disability group in pre-school-aged children. Approximately 7% of the population is expected to have developmental language difficulties. However, the specific etiological factors leading to DLD are not yet known and even the typical linguistic features appear to vary by language. We present here a project that investigates DLD at multiple levels of analysis and aims to make the reliable prediction and early identification of the difficulties possible. Following the multiple deficit model of developmental disorders, we investigate the DLD phenomenon at the etiological, neural, cognitive, behavioral, and psychosocial levels, in a longitudinal study of preschool children.

METHODS

In January 2013, we launched the Helsinki Longitudinal SLI study (HelSLI) at the Helsinki University Hospital ( http://tiny.cc/HelSLI ). We will study 227 children aged 3-6 years with suspected DLD and their 160 typically developing peers. Five subprojects will determine how the child's psychological characteristics and environment correlate with DLD and how the child's well-being relates to DLD, the characteristics of DLD in monolingual versus bilingual children, nonlinguistic cognitive correlates of DLD, electrophysiological underpinnings of DLD, and the role of genetic risk factors. Methods include saliva samples, EEG, computerized cognitive tasks, neuropsychological and speech and language assessments, video-observations, and questionnaires.

DISCUSSION

The project aims to increase our understanding of the multiple interactive risk and protective factors that affect the developing heterogeneous cognitive and behavioral profile of DLD, including factors affecting literacy development. This accumulated knowledge will form a heuristic basis for the development of new interventions targeting linguistic and non-linguistic aspects of DLD.

Music-induced positive mood broadens the scope of auditory attention

Previous studies indicate that positive mood broadens the scope of visual attention, which can manifest as heightened distractibility. We used event-related potentials (ERP) to investigate whether music-induced positive mood has comparable effects on selective attention in the auditory domain. Subjects listened to experimenter-selected happy, neutral or sad instrumental music and afterwards participated in a dichotic listening task. Distractor sounds in the unattended channel elicited responses related to early sound encoding (N1/MMN) and bottom-up attention capture (P3a) while target sounds in the attended channel elicited a response related to top-down-controlled processing of task-relevant stimuli (P3b). For the subjects in a happy mood, the N1/MMN responses to the distractor sounds were enlarged while the P3b elicited by the target sounds was diminished. Behaviorally, these subjects tended to show heightened error rates on target trials following the distractor sounds. Thus, the ERP and behavioral results indicate that the subjects in a happy mood allocated their attentional resources more diffusely across the attended and the to-be-ignored channels. Therefore, the current study extends previous research on the effects of mood on visual attention and indicates that even unfamiliar instrumental music can broaden the scope of auditory attention via its effects on mood.

Vowel-speech versus pure-tone processing in healthy subjects

To investigate the characteristics of speech perception, we evaluated the differences in mismatch negativity (MMN) between vowel change and frequency change. Additionally, we examined the effects of gender, age, and educational length on MMN. Forty healthy adults (21 females), who were native Japanese speakers, participated in the study. A Japanese vowel-speech pair (standard/a/vs. deviant/o/) and a pure-tone pair (standard 1000 Hz vs. deviant 1050 Hz) were constructed. MMN elicited by vowel-speech sounds was larger and earlier compared with pure-tone sounds. Larger and earlier MMNs for vowel-speech sounds than for pure-tone sounds suggest different processing of linguistically relevant information at the early stage in the auditory cortex. In conclusion, the factors influencing on MMN are different between vowel-speech sounds and pure-tone sounds.

Background Suppression and its Relation to Foreground Processing of Speech Versus Non-speech Streams

Since sound perception takes place against a background with a certain amount of noise, both speech and non-speech processing involve extraction of target signals and suppression of background noise. Previous works on early processing of speech phonemes largely neglected how background noise is encoded and suppressed. This study aimed to fill in this gap. We adopted an oddball paradigm where speech (vowels) or non-speech stimuli (complex tones) were presented with or without a background of amplitude-modulated noise and analyzed cortical responses related to foreground stimulus processing, including mismatch negativity (MMN), N2b, and P300, as well as neural representations of the background noise, that is, auditory steady-state response (ASSR). We found that speech deviants elicited later and weaker MMN, later N2b, and later P300 than non-speech ones, but N2b and P300 had similar strength, suggesting more complex processing of certain acoustic features in speech. Only for vowels, background noise enhanced N2b strength relative to silence, suggesting an attention-related speech-specific process to improve perception of foreground targets. In addition, noise suppression in speech contexts, quantified by ASSR amplitude reduction after stimulus onset, was lateralized towards the left hemisphere. The left-lateralized suppression following N2b was associated with the N2b enhancement in noise for speech, indicating that foreground processing may interact with background suppression, particularly during speech processing. Together, our findings indicate that the differences between perception of speech and non-speech sounds involve not only the processing of target information in the foreground but also the suppression of irrelevant aspects in the background.

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.

Noise Equally Degrades Central Auditory Processing in 2- and 4-Year-Old Children

PURPOSE

The aim of this study was to investigate developmental and noise-induced changes in central auditory processing indexed by event-related potentials in typically developing children.

METHOD

P1, N2, and N4 responses as well as mismatch negativities (MMNs) were recorded for standard syllables and consonants, frequency, intensity, vowel, and vowel duration changes in silent and noisy conditions in the same 14 children at the ages of 2 and 4 years.

RESULTS

The P1 and N2 latencies decreased and the N2, N4, and MMN amplitudes increased with development of the children. The amplitude changes were strongest at frontal electrodes. At both ages, background noise decreased the P1 amplitude, increased the N2 amplitude, and shortened the N4 latency. The noise-induced amplitude changes of P1, N2, and N4 were strongest frontally. Furthermore, background noise degraded the MMN. At both ages, MMN was significantly elicited only by the consonant change, and at the age of 4 years, also by the vowel duration change during noise.

CONCLUSIONS

Developmental changes indexing maturation of central auditory processing were found from every response studied. Noise degraded sound encoding and echoic memory and impaired auditory discrimination at both ages. The older children were as vulnerable to the impact of noise as the younger children.

SUPPLEMENTAL MATERIALS

https://doi.org/10.23641/asha.5233939.

Can an auditory multi-feature optimal paradigm be used for the study of processes associated with attention capture in passive listeners?

OBJECTIVE

A rarely occurring and highly relevant auditory stimulus occurring outside of the current focus of attention can cause a switching of attention. Such attention capture is often studied in oddball paradigms consisting of a frequently occurring "standard" stimulus which is changed at odd times to form a "deviant". The deviant may result in the capturing of attention. An auditory ERP, the P3a, is often associated with this process. To collect a sufficient amount of data is however very time-consuming. A more multi-feature "optimal" paradigm has been proposed but it is not known if it is appropriate for the study of attention capture.

METHODS

An optimal paradigm was run in which 6 different rare deviants (p=.08) were separated by a standard stimulus (p=.50) and compared to results when 4 oddball paradigms were also run.

RESULTS

A large P3a was elicited by some of the deviants in the optimal paradigm but not by others. However, very similar results were observed when separate oddball paradigms were run.

CONCLUSIONS & SIGNIFICANCE

The present study indicates that the optimal paradigm provides a very time-saving method to study attention capture and the P3a.

Auditory evoked potentials to speech and nonspeech stimuli are associated with verbal skills in preschoolers

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ERPs to speech and matched nonspeech sounds were recorded in 63 preschoolers.

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P1 and N2 were larger for nonspeech than speech sounds, the opposite being true for N4.

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Differences between speech and nonspeech ERPs were associated with verbal skills.

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ERP lateralization was associated with phonological and naming abilities.

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The results suggest that ERPs are useful measures of children’s cortical functioning.

Children’s obligatory auditory event-related potentials (ERPs) to speech and nonspeech sounds have been shown to associate with reading performance in children at risk or with dyslexia and their controls. However, very little is known of the cognitive processes these responses reflect. To investigate this question, we recorded ERPs to semisynthetic syllables and their acoustically matched nonspeech counterparts in 63 typically developed preschoolers, and assessed their verbal skills with an extensive set of neurocognitive tests. P1 and N2 amplitudes were larger for nonspeech than speech stimuli, whereas the opposite was true for N4. Furthermore, left-lateralized P1s were associated with better phonological and prereading skills, and larger P1s to nonspeech than speech stimuli with poorer verbal reasoning performance. Moreover, left-lateralized N2s, and equal-sized N4s to both speech and nonspeech stimuli were associated with slower naming. In contrast, children with equal-sized N2 amplitudes at left and right scalp locations, and larger N4s for speech than nonspeech stimuli, performed fastest. We discuss the possibility that children’s ERPs reflect not only neural encoding of sounds, but also sound quality processing, memory-trace construction, and lexical access. The results also corroborate previous findings that speech and nonspeech sounds are processed by at least partially distinct neural substrates.

Long-term influence of recurrent acute otitis media on neural involuntary attention switching in 2-year-old children

BACKGROUND

A large group of young children are exposed to repetitive middle ear infections but the effects of the fluctuating hearing sensations on immature central auditory system are not fully understood. The present study investigated the consequences of early childhood recurrent acute otitis media (RAOM) on involuntary auditory attention switching.

METHODS

By utilizing auditory event-related potentials, neural mechanisms of involuntary attention were studied in 22-26 month-old children (N = 18) who had had an early childhood RAOM and healthy controls (N = 19). The earlier and later phase of the P3a (eP3a and lP3a) and the late negativity (LN) were measured for embedded novel sounds in the passive multi-feature paradigm with repeating standard and deviant syllable stimuli. The children with RAOM had tympanostomy tubes inserted and all the children in both study groups had to have clinically healthy ears at the time of the measurement assessed by an otolaryngologist.

RESULTS

The results showed that lP3a amplitude diminished less from frontal to central and parietal areas in the children with RAOM than the controls. This might reflect an immature control of involuntary attention switch. Furthermore, the LN latency was longer in children with RAOM than in the controls, which suggests delayed reorientation of attention in RAOM.

CONCLUSIONS

The lP3a and LN responses are affected in toddlers who have had a RAOM even when their ears are healthy. This suggests detrimental long-term effects of RAOM on the neural mechanisms of involuntary attention.

Modulation of pre-attentive spectro-temporal feature processing in the human auditory system by HD-tDCS

The present study examined the functional lateralization of the human auditory cortex (AC) for pre-attentive spectro-temporal feature processing. By using high-definition transcranial direct current stimulation (HD-tDCS), we systematically modulated neuronal activity of the bilateral AC. We assessed the influence of anodal and cathodal HD-tDCS delivered over the left or right AC on auditory mismatch negativity (MMN) in response to temporal as well as spectral deviants in 12 healthy subjects. The results showed that MMN to temporal deviants was significantly enhanced by anodal HD-tDCS applied over the left AC only. Our data indicate a left hemispheric dominance for the pre-attentive processing of low-level temporal information.

Differences in sensory processing of German vowels and physically matched non-speech sounds as revealed by the mismatch negativity (MMN) of the human event-related brain potential (ERP)

We compared processing of speech and non-speech by means of the mismatch negativity (MMN). For this purpose, the MMN elicited by vowels was compared to those elicited by two non-speech stimulus types: spectrally rotated vowels, having the same stimulus complexity as the speech stimuli, and sounds based on the bands of formants of the vowels, representing non-speech stimuli of lower complexity as compared to the other stimulus types. This design allows controlling for effects of stimulus complexity when comparing neural correlates of processing speech to non-speech. Deviants within a modified multi-feature design differed either in duration or spectral property. Moreover, the difficulty to discriminate between the standard and the two deviants was controlled for each stimulus type by means of an additional active discrimination task. Vowels elicited a larger MMN compared to both non-speech stimulus types, supporting the concept of language-specific phoneme representations and the role of the participants' prior experience.

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.

The five myths of MMN: redefining how to use MMN in basic and clinical research

The goal of this review article is to redefine what the mismatch negativity (MMN) component of event-related potentials reflects in auditory scene analysis, and to provide an overview of how the MMN serves as a valuable tool in Cognitive Neuroscience research. In doing so, some of the old beliefs (five common 'myths') about MMN will be dispelled, such as the notion that MMN is a simple feature discriminator and that attention itself modulates MMN elicitation. A revised description of what MMN truly reflects will be provided, which includes a principal focus onto the highly context-dependent nature of MMN elicitation and new terminology to discuss MMN and attention. This revised framework will help clarify what has been a long line of seemingly contradictory results from studies in which behavioral ability to hear differences between sounds and passive elicitation of MMN have been inconsistent. Understanding what MMN is will also benefit clinical research efforts by providing a new picture of how to design appropriate paradigms suited to various clinical populations.

Hearing an illusory vowel in noise: suppression of auditory cortical activity

Human hearing is constructive. For example, when a voice is partially replaced by an extraneous sound (e.g., on the telephone due to a transmission problem), the auditory system may restore the missing portion so that the voice can be perceived as continuous (Miller and Licklider, 1950; for review, see Bregman, 1990; Warren, 1999). The neural mechanisms underlying this continuity illusion have been studied mostly with schematic stimuli (e.g., simple tones) and are still a matter of debate (for review, see Petkov and Sutter, 2011). The goal of the present study was to elucidate how these mechanisms operate under more natural conditions. Using psychophysics and electroencephalography (EEG), we assessed simultaneously the perceived continuity of a human vowel sound through interrupting noise and the concurrent neural activity. We found that vowel continuity illusions were accompanied by a suppression of the 4 Hz EEG power in auditory cortex (AC) that was evoked by the vowel interruption. This suppression was stronger than the suppression accompanying continuity illusions of a simple tone. Finally, continuity perception and 4 Hz power depended on the intactness of the sound that preceded the vowel (i.e., the auditory context). These findings show that a natural sound may be restored during noise due to the suppression of 4 Hz AC activity evoked early during the noise. This mechanism may attenuate sudden pitch changes, adapt the resistance of the auditory system to extraneous sounds across auditory scenes, and provide a useful model for assisted hearing devices.

Effects of diet on early stage cortical perception and discrimination of syllables differing in voice-onset time: a longitudinal ERP study in 3 and 6 month old infants

The influence of diet on cortical processing of syllables was examined at 3 and 6 months in 239 infants who were breastfed or fed milk or soy-based formula. Event-related potentials to syllables differing in voice-onset-time were recorded from placements overlying brain areas specialized for language processing. P1 component amplitude and latency measures indicated that at both ages infants in all groups could extract and discriminate categorical information from syllables. Between-syllable amplitude differences-present across groups-were generally greater for SF infants. Responses peaked earlier over left hemisphere speech-perception than speech-production areas. Encoding was faster in BF than formula-fed infants. The results show that in preverbal infants: (1) discrimination of phonetic information occurs in early stages of cortical processing; (2) areas overlying brain regions of speech perception are activated earlier than those involved in speech production; and (3) these processes are differentially modulated by infant diet and environmental factors.

The mismatch negativity (MMN)--a unique window to disturbed central auditory processing in ageing and different clinical conditions

In this article, we review clinical research using the mismatch negativity (MMN), a change-detection response of the brain elicited even in the absence of attention or behavioural task. In these studies, the MMN was usually elicited by employing occasional frequency, duration or speech-sound changes in repetitive background stimulation while the patient was reading or watching videos. It was found that in a large number of different neuropsychiatric, neurological and neurodevelopmental disorders, as well as in normal ageing, the MMN amplitude was attenuated and peak latency prolonged. Besides indexing decreased discrimination accuracy, these effects may also reflect, depending on the specific stimulus paradigm used, decreased sensory-memory duration, abnormal perception or attention control or, most importantly, cognitive decline. In fact, MMN deficiency appears to index cognitive decline irrespective of the specific symptomatologies and aetiologies of the different disorders involved.

Linguistic multifeature MMN paradigm for extensive recording of auditory discrimination profiles

We studied whether a multifeature mismatch negativity (MMN) paradigm using naturally produced speech stimuli is feasible for studies of auditory discrimination accuracy of adult participants. A naturally produced trisyllabic pseudoword was used in the paradigm, and MMNs were recorded to changes that were acoustic (changes in fundamental frequency or intensity) or potentially phonological (changes in vowel identity or vowel duration). All the different changes were presented in three different word segments (initial, middle, or final syllable). All changes elicited an MMN response, but the vowel duration change elicited a different response pattern than the other deviant types. Changes in vowel duration and identity also had an effect on MMN lateralization. Our results show that assessing speech sound discrimination of several features in word context is possible in a short recording time (30 min) with the multifeature paradigm.

Left posterior temporal regions are sensitive to auditory categorization

Recent studies suggest that the left superior temporal gyrus and sulcus (LSTG/S) play a role in speech perception, although the precise function of these areas remains unclear. Here, we test the hypothesis that regions in the LSTG/S play a role in the categorization of speech phonemes, irrespective of the acoustic properties of the sounds and prior experience of the listener with them. We examined changes in functional magnetic resonance imaging brain activation related to a perceptual shift from nonphonetic to phonetic analysis of sine-wave speech analogs. Subjects performed an identification task before scanning and a discrimination task during scanning with phonetic (P) and nonphonetic (N) sine-wave sounds, both before (Pre) and after (Post) being exposed to the phonetic properties of the P sounds. Behaviorally, experience with the P sounds induced categorical identification of these sounds. In the PostP > PreP and PostP > PostN contrasts, an area in the posterior LSTG/S was activated. For both P and N sounds, the activation in this region was correlated with the degree of categorical identification in individual subjects. The results suggest that these areas in the posterior LSTG/S are sensitive neither to the acoustic properties of speech nor merely to the presence of phonetic information, but rather to the listener's awareness of category representations for auditory inputs.