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

Twenty-month-olds categorically discriminate similar sounding vowels regardless of vocabulary level, an event related potentials (ERP) study

The current study investigated whether vocabulary relates to phonetic categorization at neural level in early childhood. Electoencephalogram (EEG) responses were collected from 53 Dutch 20-month-old children in a passive oddball paradigm, in which they were presented with two nonwords "giep" [ɣip] and "gip" [ɣɪp] that were contrasted solely by the vowel. In the multiple-speaker condition, both nonwords were produced by twelve different speakers; while, in the single-speaker condition, one single token of each word was used as stimuli. Infant positive mismatch responses (p-MMR) were elicited in both conditions without significant amplitude differences. When the infants were median split based on vocabulary level, the large and small vocabulary groups showed comparable p-MMR amplitudes yet different scalp distribution in both conditions. These results suggest successful phonetic categorization of native similar sounding vowels at 20 months, and a close relationship between speech categorization and vocabulary development.

"Neural Noise" in Auditory Responses in Young Autistic and Neurotypical Children

Elevated "neural noise" has been advanced as an explanation of autism and autistic sensory experiences. However, functional neuroimaging measures of neural noise may be vulnerable to contamination by recording noise. This study explored variability of electrophysiological responses to tones of different intensities in 127 autistic and 79 typically-developing children aged 2-5 years old. A rigorous data processing pipeline, including advanced visualizations of different signal sources that were maximally independent across different time lags, was used to identify and eliminate putative recording noise. Inter-trial variability was measured using median absolute deviations (MADs) of EEG amplitudes across trials and inter-trial phase coherence (ITPC). ITPC was elevated in autism in the 50 and 60 dB intensity conditions, suggesting diminished (rather than elevated) neural noise in autism, although reduced ITPC to soft 50 dB sounds was associated with increased loudness discomfort. Autistic and non-autistic participants did not differ in MADs, and indeed, the vast majority of the statistical tests examined in this study yielded no significant effects. These results appear inconsistent with the neural noise account.

Mismatch Responses to Speech Contrasts in Preschoolers with and without Developmental Language Disorder

This study compared cortical responses to speech in preschoolers with typical language development (TLD) and with Developmental Language Disorder (DLD). We investigated whether top-down language effects modulate speech perception in young children in an adult-like manner. We compared cortical mismatch responses (MMRs) during the passive perception of speech contrasts in three groups of participants: preschoolers with TLD (n = 11), preschoolers with DLD (n = 16), and adults (n = 20). We also measured children's phonological skills and investigated whether they are associated with the cortical discrimination of phonemic changes involving different linguistic complexities. The results indicated top-down language effects in adults, with enhanced cortical discrimination of lexical stimuli but not of non-words. In preschoolers, the TLD and DLD groups did not differ in the MMR measures, and no top-down effects were detected. Moreover, we found no association between MMRs and phonological skills, even though the DLD group's phonological skills were significantly lower. Our findings suggest that top-down language modulations in speech discrimination may not be present during early childhood, and that children with DLD may not exhibit cortical speech perception deficits. The lack of association between phonological and MMR measures indicates that further research is needed to understand the link between language skills and cortical activity in preschoolers.

Habituation of auditory responses in young autistic and neurotypical children

Prior studies suggest that habituation of sensory responses is reduced in autism and that diminished habituation could be related to atypical autistic sensory experiences, for example, by causing brain responses to aversive stimuli to remain strong over time instead of being suppressed. While many prior studies exploring habituation in autism have repeatedly presented identical stimuli, other studies suggest group differences can still be observed in habituation to intermittent stimuli. The present study explored habituation of electrophysiological responses to auditory complex tones of varying intensities (50-80 dB SPL), presented passively in an interleaved manner, in a well-characterized sample of 127 autistic (MDQ  = 65.41, SD = 20.54) and 79 typically developing (MDQ  = 106.02, SD = 11.50) children between 2 and 5 years old. Habituation was quantified as changes in the amplitudes of single-trial responses to tones of each intensity over the course of the experiment. Habituation of the auditory N2 response was substantially reduced in autistic participants as compared to typically developing controls, although diagnostic groups did not clearly differ in habituation of the P1 response. Interestingly, the P1 habituated less to loud 80 dB sounds than softer sounds, whereas the N2 habituated less to soft 50 dB sounds than louder sounds. No associations were found between electrophysiological habituation and cognitive ability or participants' caregiver-reported sound tolerance (Sensory Profile Hyperacusis Index). The results present study results extend prior research suggesting habituation of certain sensory responses is reduced in autism; however, they also suggest that habituation differences observed using this study's paradigm might not be a primary driver of autistic participants' real-world sound intolerance.

Event-Related Potentials to Speech Relate to Speech Sound Production and Language in Young Children

This research was funded through the American Speech and Hearing Foundation's 2012 StudentResearch Grant in Early Childhood Language Development awarded to Vanessa Harwood as well as an anonymous generous donation to Haskins Laboratories. Electrophysiological measures of language within early childhood provide important information about neurolinguistic development. We investigated associations between amplitude and latency of the P1 and N2 event-related potential components in response to spoken pseudowords, and clinical measures of language performance within a sample of 58 typically developing children between 24 and 48 months. N2 amplitude differences between repeated and new tokens were correlated with measures of expressive and receptive language and speech sound production. Phonemic sensitivity measured by the N2 component may reflect the integrity of neural networks that are important for speech perception and production in young children.

Using Clustering to Examine Inter-individual Variability in Topography of Auditory Event-Related Potentials in Autism and Typical Development

Although prior studies have compared sensory event-related potential (ERP) responses between groups of autistic and typically-developing participants, it is unclear how heterogeneity contributes to the results of these studies. The present study used examined individual differences in these responses. 130 autistic children and 81 typically-developing children, aged between 2 and 5 years, listened to tones at four identity levels while 61-channel electroencephalography was recorded. Hierarchical clustering was used to group participants based on rescaled ERP topographies between 51 and 350 ms. The hierarchical clustering analysis revealed substantial heterogeneity. Some of the seven clusters defined in this analysis were characterized by prolonged fronto-central positivities and/or weak or absent N2 negativities. However, many other participants fell into clusters in which N2 responses were present at varying latencies. Atypical response morphologies such as absent N2 responses and/or prolonged positive-going responses found in some autistic participants may account for prior research findings of attenuated N2 amplitudes in autism. However, there was also considerable overlap between groups, with participants of both groups appearing in all clusters. These results emphasize the utility of using clustering to explore individual differences in brain responses, which can expand on and clarify the results of analyses of group mean differences.

Auditory Discrimination in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is increasingly common with 1 in 59 children in the United States currently meeting the diagnostic criteria. Altered sensory processing is typical in ASD, with auditory sensitivities being especially common; in particular, people with ASD frequently show heightened sensitivity to environmental sounds and a poor ability to tolerate loud sounds. These sensitivities may contribute to impairments in language comprehension and to a worsened ability to distinguish relevant sounds from background noise. Event-related potential tests have found that individuals with ASD show altered cortical activity to both simple and speech-like sounds, which likely contribute to the observed processing impairments. Our goal in this review is to provide a description of ASD-related changes to the auditory system and how those changes contribute to the impairments seen in sound discrimination, sound-in-noise performance, and language processing. In particular, we emphasize how differences in the degree of cortical activation and in temporal processing may contribute to errors in sound discrimination.

Effects of age on loudness-dependent auditory ERPs in young autistic and typically-developing children

Limited research has investigated the development of auditory ERPs in young children, and particularly how stimulus intensity may affect these auditory ERPs. Previous research has also yielded inconsistent findings regarding differences in the development of auditory ERPs in autism and typical development. Furthermore, stimulus intensity may be of particular interest in autism insofar as autistic people may have atypical experiences of sound intensity (e.g., hyperacusis). Therefore, the present study examined associations between age and ERPs evoked by tones of differing intensities (50, 60, 70, and 80 dB SPL) in a large sample of young children (2-5 years) with and without an autism diagnosis. Correlations between age and P1 latencies were examined, while cluster-based permutation testing was used to examine associations between age and neural response amplitudes, as well as group differences in amplitude, over all electrode sites in the longer time window of 1-350 ms. Older autistic participants had faster P1 latencies, but these effects only attained significance over the right hemisphere in response to soft 50 dB sounds. Autistic participants had slower P1 responses to 80 dB sounds over the right hemisphere. Over the scalp regions associated with the later N2 response, more negative response amplitudes (that is, larger N2 responses) were observed in typically-developing than autistic participants. Furthermore, continuous associations between response amplitudes and age suggested that older typically-developing participants exhibited stronger N2 responses to all intensities, though this effect may have at least in part reflected the absence of small positive voltage deflections in the N2 latency window. Age was associated with amplitudes of responses to 50 dB through 70 dB sounds in autism, but in contrast to Typical Development (TD), little evidence of relationships between age and amplitudes in the N2 latency window was found in autism in the 80 dB condition. Although caution should be exercised in interpretation due to the cross-sectional nature of this study, these findings suggest that developmental changes in auditory responses may differ across diagnostic groups in a manner that depends on perceived loudness and/or stimulus intensity.

Maturation of Speech-Sound ERPs in 5-6-Year-Old Children: A Longitudinal Study

The maturation of 5-6-year-old children's auditory discrimination - indicated by the development of the auditory event-related-potentials (ERPs) - has not been previously studied in longitudinal settings. For the first time, we present here the results based on extensive dataset collected from 75 children. We followed the 5- to 6-year-olds for 20 months and measured their ERPs four times with the same multifeature paradigm with phonemic stimuli. The amplitude of the mismatch negativity (MMN) response increased during this time for vowel, vowel duration and frequency changes. Furthermore, the P3a component started to mature toward adult-like positivity for the vowel, intensity and frequency deviants and the late discriminative negativity (LDN) component decreased with age for vowel and intensity deviants. All the changes in the components seemed to happen during the second follow-up year, when Finnish children are taught letter symbols and other preliminary academic skills before going to school at the age of seven. Therefore, further studies are needed to clarify if these changes in the auditory discrimination are purely age-related or due to increasing linguistic knowledge of the children.

Cortical maturation of long latency auditory evoked potentials in hearing children: the complex P1-N1-P2-N2

Purpose

The purpose of this study was to monitor the emergence and changes to the components of the Long Latency Auditory Evoked Potentials (LLAEP) in normal hearing children.

Methods

This longitudinal study included children of both genders: seven aged between 10 and 35 months, and eight children between 37 and 63 months. The electrophysiological hearing evaluation consisted of analysis of LLAEP obtained in a sound field generated with loudspeakers positioned at an azimuth of 90°, through which the syllable /ba/ was played at an intensity of 70 dB HL. Each child underwent an initial evaluation followed by two re-evaluations three and nine months later.

Results

The emergence of LLAEP components across the nine-month follow-up period was observed. P1 and N2 were the most common components in children of this age range. There was no statistically significant difference regarding the occurrence of P1, N1, P2, and N2 components amongst younger and older children. Regarding latency values, the greatest changes overtime were observed in the P1 component for younger children and in the N2 component for older children. Only the P1 component significantly differed between the groups, with the highest latency values observed in younger children.

Conclusion

LLAEP maturation occurs gradually and the emergence of complex components appears to be related more to the maturation of the central auditory nervous system than to chronological age.

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.

Auditory Discrimination Between Function Words in Children and Adults: A Mismatch Negativity Study

Previous behavioral studies showed that it is not until around the age of seven that German children reliably use case markers for the interpretation of complex sentences. Some explanations of this late development suggested that children might have difficulties in perceptual differentiation between function words that carry case information. We tested this hypothesis by using the neurophysiological index of pre-attentive discrimination, the mismatch negativity (MMN). Our data showed that children at the age of 3 years are able to automatically discriminate between the two determiner forms der and den when presented out of sentential context. The determiner form der elicited a more mature MMN response in children than the form den. In adults, the MMN pattern also differed with der showing an earlier peak than den. These findings indicate that der is easier to process than den, which in turn is related to the occurrence frequency of the determiner forms in language.

The maturation of auditory responses in infants and young children: a cross-sectional study from 6 to 59 months

Background: An understanding of the maturation of auditory cortex responses in typically developing infants and toddlers is needed to later identify auditory processing abnormalities in infants at risk for neurodevelopmental disorders. The availability of infant and young child magnetoencephalography (MEG) systems may now provide near optimal assessment of left and right hemisphere auditory neuromagnetic responses in young populations. To assess the performance of a novel whole-head infant MEG system, a cross-sectional study examined the maturation of left and right auditory cortex responses in children 6- to 59-months of age.

Methods: Blocks of 1000 Hz (1st and 3rd blocks) and 500 Hz tones (2nd block) were presented while MEG data were recorded using an infant/young child biomagnetometer (Artemis 123). Data were obtained from 29 children (11 males; 6- to 59-months). Latency measures were obtained for the first positive-to-negative evoked response waveform complex in each hemisphere. Latency and age associations as well as frequency and hemisphere latency differences were examined. For the 1000 Hz tone, measures of reliability were computed.

Results: For the first response—a response with a “P2m” topography—latencies decreased as a function of age. For the second response—a response with a “N2m” topography—no N2m latency and age relationships were observed. A main effect of tone frequency showed earlier P2m responses for 1st 1000 Hz (150 ms) and 2nd 1000 Hz (148 ms) vs. 500 Hz tones (162 ms). A significant main effect of hemisphere showed earlier N2m responses for 2nd 1000 Hz (226 ms) vs. 1st 1000 Hz (241 ms) vs. 500 Hz tones (265 ms). P2m and N2m interclass correlation coefficient latency findings were as follows: left P2m (0.72, p < 0.001), right P2m (0.84, p < 0.001), left N2m (0.77, p < 0.001), and right N2m (0.77,p < 0.01).

Conclusions: Findings of strong age and latency associations, sensitivity to tone frequency, and good test-retest reliability support the viability of longitudinal infant MEG studies that include younger as well as older participants as well as studies examining auditory processing abnormalities in infants at risk for neurodevelopmental disorders.

Auditory stream segregation using bandpass noises: evidence from event-related potentials

The current study measured neural responses to investigate auditory stream segregation of noise stimuli with or without clear spectral contrast. Sequences of alternating A and B noise bursts were presented to elicit stream segregation in normal-hearing listeners. The successive B bursts in each sequence maintained an equal amount of temporal separation with manipulations introduced on the last stimulus. The last B burst was either delayed for 50% of the sequences or not delayed for the other 50%. The A bursts were jittered in between every two adjacent B bursts. To study the effects of spectral separation on streaming, the A and B bursts were further manipulated by using either bandpass-filtered noises widely spaced in center frequency or broadband noises. Event-related potentials (ERPs) to the last B bursts were analyzed to compare the neural responses to the delay vs. no-delay trials in both passive and attentive listening conditions. In the passive listening condition, a trend for a possible late mismatch negativity (MMN) or late discriminative negativity (LDN) response was observed only when the A and B bursts were spectrally separate, suggesting that spectral separation in the A and B burst sequences could be conducive to stream segregation at the pre-attentive level. In the attentive condition, a P300 response was consistently elicited regardless of whether there was spectral separation between the A and B bursts, indicating the facilitative role of voluntary attention in stream segregation. The results suggest that reliable ERP measures can be used as indirect indicators for auditory stream segregation in conditions of weak spectral contrast. These findings have important implications for cochlear implant (CI) studies-as spectral information available through a CI device or simulation is substantially degraded, it may require more attention to achieve stream segregation.

Developmental changes in mismatch responses to mandarin consonants and lexical tones from early to middle childhood

The purpose of this study was to use mismatch responses (MMRs) to explore the dynamic changes of Mandarin speech perception abilities from early to middle childhood. Twenty preschoolers, 18 school-aged children, and 26 adults participated in this study. Two sets of synthesized speech stimuli varying in Mandarin consonant (alveolo-palatal affricate vs. fricative) and lexical tone features (rising vs. contour tone) were used to examine the developmental course of speech perception abilities. The results indicated that only the adult group demonstrated typical early mismatch negativity (MMN) responses, suggesting that the ability to discriminate specific speech cues in Mandarin consonant and lexical tone is a continuing process in preschool- and school-aged children. Additionally, distinct MMR patterns provided evidence indicating diverse developmental courses to different speech characteristics. By incorporating data from the two speech conditions, we propose using MMR profiles consisting of mismatch negativity (MMN), positive mismatch response (p-MMR), and late discriminative negativity (LDN) as possible brain indices to investigate speech perception development.

Normative topographic ERP analyses of speed of speech processing and grammar before and after grammatical treatment

Typically developing (TD) preschoolers and age-matched preschoolers with specific language impairment (SLI) received event-related potentials (ERPs) to four monosyllabic speech sounds prior to treatment and, in the SLI group, after 6 months of grammatical treatment. Before treatment, the TD group processed speech sounds faster than the SLI group. The SLI group increased the speed of their speech processing after treatment. Posttreatment speed of speech processing predicted later impairment in comprehending phrase elaboration in the SLI group. During the treatment phase, change in speed of speech processing predicted growth rate of grammar in the SLI group.

The Acoustic Change Complex in Young Children with Hearing Loss: A Preliminary Study

The acoustic change complex (ACC) is a cortical auditory evoked potential elicited in response to a change in an ongoing sound. The ACC may have promise for assessing speech perception in infants and toddlers. In this preliminary study, the ACC was elicited in adults and young children in response to changes in speech stimuli representing vowel height /u/-/a/ and vowel place /u/-/i/ contrasts. The participants were adults with normal hearing (n = 3), children with normal hearing (n = 5), and children with mild to moderately severe bilateral sensorineural hearing loss (n = 5). The children with hearing loss were hearing aid users. The ages ranged from 2 years 3 months to 6 years 3months for the children and 44 to 55 years for the adults. Robust P1-N1-P2 responses were present for the adults and P1-N2 responses were present for all but the youngest child with hearing loss. The ACC response for the vowel place contrast was less robust than that for the vowel height contrast in one child with substantial hearing loss. The findings from this preliminary study support the conclusion that the ACC can be used successfully to assess auditory resolution in most young children.

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.

Time course of ERP generators to syllables in infants: a source localization study using age-appropriate brain templates

Event-related potentials (ERPs) have become an important tool in the quest to understand how infants process perceptual information. Identification of the activation loci of the ERP generators is a technique that provides an opportunity to explore the neural substrates that underlie auditory processing. Nevertheless, as infant brain templates from healthy, non-clinical samples have not been available, the majority of source localization studies in infants have used non-realistic head models, or brain templates derived from older children or adults. Given the dramatic structural changes seen across infancy, all of which profoundly affect the electrical fields measured with EEG, it is important to use individual MRIs or age-appropriate brain templates and parameters to explore the localization and time course of auditory ERP sources. In this study 6-month-old infants were presented with a passive oddball paradigm using consonant-vowel (CV) syllables that differed in voice onset time. Dense-array EEG/ERPs were collected while the infants were awake and alert. In addition, MRIs were acquired during natural non-sedated sleep for a subset of the sample. Discrete dipole and distributed source models were mapped onto individual and averaged infant MRIs. The CV syllables elicited a positive deflection at about 200 ms followed by a negative deflection that peaked around 400 ms. The source models generated placed the dipoles at temporal areas close to auditory cortex for both positive and negative responses. Notably, an additional dipole for the positive peak was localized at the frontal area, at the anterior cingulate cortex (ACC) level. ACC activation has been reported in adults, but has not, to date, been reported in infants during processing of speech-related signals. The frontal ACC activation was earlier but smaller in amplitude than the left and right auditory temporal activations. These results demonstrate that in infancy the ERP generators to CV syllables are localized in cortical areas similar to that reported in adults, but exhibit a notably different temporal course. Specifically, ACC activation in infants significantly precedes auditory temporal activation, whereas in adults ACC activation follows that of temporal cortex. We suggest that these timing differences could be related to current maturational changes, to the ongoing construction of language-specific phonetic maps, and/or to more sensitive attentional switching as a response to speech signals in infancy.

Cortical responses to speech sounds in 3- and 6-month-old infants fed breast milk, milk formula, or soy formula

Controversy exists about the safety of soy formula, with the main concern relating to potential estrogenic effects of soy protein. Since estrogens influence early brain development, we compared behavioral development and cortical responses (event-related potentials; ERPs) to speech sounds in infants fed either breast milk or formula (milk- or soy-based). Across-groups ERP measures were generally similar and behavioral measures were within normal ranges, suggesting no important influences of soy formula on behavioral development and brain function during the study period. Analyses relating ERP and behavioral measures revealed diet- and gender-specific emphases that may reflect differences in developmental trajectories of brain-behavior relationships.

Maturation of speech discrimination in 4- to 7-yr-old children as indexed by event-related potential mismatch responses

OBJECTIVES

This study examined maturation of mismatch responses (MMRs) to an English vowel contrast (/I/ versus /ε/) in 4- to 7-yr-old children.

DESIGN

Event-related potentials were recorded to a standard [ε] and deviant [I] vowel presented in trains of 10 stimuli at a rate of 1/650 msecs and with an intertrain interval of 1.5 secs. Each train contained two deviant vowels. Averaged responses were calculated for the infrequent (deviant) and the frequent (standard) trials for each child and compared across age groups.

RESULTS

Significantly greater negativity, consistent with the adult mismatch negativity (MMN), was observed to the deviants between 300 and 400 msecs for both younger (4- and 5-yr-old) and older (6- and 7-yr-old) children. This MMN-like negativity shifted earlier in latency by 25 msecs/yr with increasing age. Most of the children younger than 5.5 yrs and some of the older children also showed a positive MMR (p-MMR) peaking between 100 and 300 msecs. The p-MMR diminished in amplitude with increasing age.

CONCLUSIONS

Maturation of speech discrimination, as indexed by MMN, occurs more rapidly between 4 and 7 yrs of age for vowels than for tones. A p-MMR preceding the MMN also reflects discrimination in younger children and declines in amplitude with age.

Maturation of auditory evoked potentials from 6 to 48 months: prediction to 3 and 4 year language and cognitive abilities

OBJECTIVE

To investigate the maturation of long-latency auditory evoked potentials (LLAEP) from 6 to 48 months in infants with a family history of language impairment (FH+) and control infants (FH-).

METHODS

LLAEPs of seventeen FH+ infants were compared to 28 FH- infants at 6, 9, 12, 16, 24, 36 and 48 months. Participants received a passive oddball paradigm using fast- and slow-rate non-linguistic auditory stimuli and at 36 and 48 months completed a battery of standardized language and cognitive tests.

RESULTS

Overall, the morphology of LLAEP responses differed for fast- versus slow-rate stimuli. Significant age-related changes in latency and amplitude were observed. Group differences, favoring FH- infants, in the rate of maturation of LLAEPs were found. Responses to fast-rate stimuli predicted language abilities at 36 and 48 months of age.

CONCLUSIONS

The development of LLAEP in FH+ children is modulated by differences in the rate of maturation as well as variations in temporal processing abilities.

SIGNIFICANCE

These findings provide evidence for the role of non-linguistic auditory processes in early language development and illustrate the utility of using a perceptual-processing skills model to further our understanding of the precursors of language development and impairment.

Diet and gender influences on processing and discrimination of speech sounds in 3- and 6-month-old infants: a developmental ERP study

Early post-natal nutrition influences later development, but there are no studies comparing brain function in healthy infants as a function of dietary intake even though the major infant diets differ significantly in nutrient composition. We studied brain responses (event-related potentials; ERPs) to speech sounds for infants who were fed either breast milk (BF), milk-based formula (MF), or soy formula (SF) during the first 6 months of life. Two syllables presented in an oddball paradigm elicited a late positive wave (P350) from temporal and frontal brain regions involved in language processes. All groups showed significantly greater response amplitudes to the infrequent syllable across sites at 3 months and frontally at 6 months, but significant discrimination at temporal sites was only observed at 6 months in BF infants. Decreases in response amplitudes from 3 to 6 months were greater for the frequently presented syllable, most prominent in BF infants, and greater in females than males. The results indicate greater syllable discrimination in BF than formula-fed infants, but whether this can be attributed to dietary influences alone remains unclear. Feeding method and background factor differences between breastfed and formula-fed infants may also contribute to the observed differences. The general absence of differences between formula-fed groups is notable and suggests that milk-based formula and soy formula equally support brain development and function during the first post-natal 6 months. Finally, the results indicate gender differences in the development of neural and temporal processes involved in sensory discrimination, and suggest that at 6 months these processes are better developed in females.

Visual influences on speech perception in children with autism

The bimodal perception of speech sounds was examined in children with autism as compared to mental age-matched typically developing (TD) children. A computer task was employed wherein only the mouth region of the face was displayed and children reported what they heard or saw when presented with consonant-vowel sounds in unimodal auditory condition, unimodal visual condition, and a bimodal condition. Children with autism showed less visual influence and more auditory influence on their bimodal speech perception as compared to their TD peers, largely due to significantly worse performance in the unimodal visual condition (lip reading). Children with autism may not benefit to the same extent as TD children from visual cues such as lip reading that typically support the processing of speech sounds. The disadvantage in lip reading may be detrimental when auditory input is degraded, for example in school settings, whereby speakers are communicating in frequently noisy environments.

Speech-and-gesture integration in high functioning autism

This study examined iconic gesture comprehension in autism, with the goal of assessing whether cross-modal processing difficulties impede speech-and-gesture integration. Participants were 19 adolescents with high functioning autism (HFA) and 20 typical controls matched on age, gender, verbal IQ, and socio-economic status (SES). Gesture comprehension was assessed via quantitative analyses of visual fixations during a video-based task, using the visual world paradigm. Participants' eye movements were recorded while they watched videos of a person describing one of four shapes shown on a computer screen, using speech-and-gesture or speech-only descriptions. Participants clicked on the shape that the speaker described. Since gesture naturally precedes speech, earlier visual fixations to the target shape during speech-and-gesture compared to speech-only trials, would suggest immediate integration of auditory and visual information. Analyses of eye movements supported this pattern in control participants but not in individuals with autism: iconic gestures facilitated comprehension in typical individuals, while it hindered comprehension in those with autism. Cross-modal processing difficulties in autism were not accounted for by impaired unimodal speech or gesture processing. The results have important implications for the treatment of children and adults with this disorder.

Differences in AERP responses and atypical hemispheric specialization in 17-month-old children at risk of dyslexia

To determine the auditory event-related potential (AERP) correlates of phoneme perception in 17-month-old children at risk of dyslexia and controls, AERPs were elicited by standard (/bAk/) and deviant (/dAk/) word stimuli presented in an oddball paradigm. The at-risk children tended to show delayed P1 and P2 peaks for standard stimuli. Hemispheric group differences were observed for N2 amplitude and P1 latency, suggesting atypical processing of spoken words in at-risk children. Larger P2 and to a lesser extent P1 amplitudes following deviant words occurred in the control but not in the at-risk group, this may signal poorer phoneme discrimination in at-risk children. The present AERP results offer clues to where to look for a marker to identify children at high risk of reading and writing problems at an early age to facilitate early intervention.

Electrophysiological correlates of selective attention: a lifespan comparison

Background

To study how event-related brain potentials (ERPs) and underlying cortical mechanisms of selective attention change from childhood to old age, we investigated lifespan age differences in ERPs during an auditory oddball task in four age groups including 24 younger children (9–10 years), 28 older children (11–12 years), 31 younger adults (18–25), and 28 older adults (63–74 years). In the Unattend condition, participants were asked to simply listen to the tones. In the Attend condition, participants were asked to count the deviant stimuli. Five primary ERP components (N1, P2, N2, P3 and N3) were extracted for deviant stimuli under Attend conditions for lifespan comparison. Furthermore, Mismatch Negativity (MMN) and Late Discriminative Negativity (LDN) were computed as difference waves between deviant and standard tones, whereas Early and Late Processing Negativity (EPN and LPN) were calculated as difference waves between tones processed under Attend and Unattend conditions. These four secondary ERP-derived measures were taken as indicators for change detection (MMN and LDN) and selective attention (EPN and LPN), respectively. To examine lifespan age differences, the derived difference-wave components for attended (MMN and LDN) and deviant (EPN and LPN) stimuli were specifically compared across the four age groups.

Results

Both primary and secondary ERP components showed age-related differences in peak amplitude, peak latency, and topological distribution. The P2 amplitude was higher in adults compared to children, whereas N2 showed the opposite effect. P3 peak amplitude was higher in older children and younger adults than in older adults. The amplitudes of N3, LDN, and LPN were higher in older children compared with both of the adult groups. In addition, both P3 and N3 peak latencies were significantly longer in older than in younger adults. Interestingly, in the young adult sample P3 peak amplitude correlated positively and P3 peak latency correlated negatively with performance in the Identical Picture test, a marker measure of fluid intelligence.

Conclusion

The present findings suggest that patterns of event-related brain potentials are highly malleable within individuals and undergo profound reorganization from childhood to adulthood and old age.

MEG detects neural consequences of anomalous nasalization in vowel–consonant pairs

This study identifies a delay in the neuromagnetic activity evoked by passive auditory presentation of anomalous speech sound combinations. Vowel-consonant-vowel (VCV) stimuli were constructed to manipulate vowel nasalization in violation of the patterns of English, in which vowel nasalization ordinarily arises as a predictable coarticulatory effect of anticipatory velum lowering for production of a following nasal consonant. For anomalous stimuli with V1 and C mismatched in nasalization, the neural response to C was delayed relative to congruent control stimuli with V1 and C matched for nasalization. As both anomalous and control stimuli represent linguistically possible speech sound sequences, the temporal disparity in evoked neuromagnetic activity in English speakers reflects a role for language-specific phonological knowledge at the earliest stages of auditory processing.

Extracting rules: early and late mismatch negativity to tone patterns

The auditory processing of physical stimulus features can be measured by the mismatch negativity. Past studies have shown that higher-order stimulus features also elicit a mismatch negativity. In some studies, a second component, termed late mismatch negativity, has been observed; yet the functional significance of this component remains unclear. We tested two-tone-pattern stimuli following an abstract rule in healthy adults. As expected, the tone pattern elicited a significant mismatch negativity peaking at 146 ms but a significant late mismatch negativity at around 340 ms was also observed. These findings show that the violation of an abstract rule elicits an early and late mismatch negativity. The late mismatch negativity might be triggered on the basis of auditory rule extraction processes and reflect a transfer of rules to the long-term memory.

Maturation of the cortical auditory evoked potential in infants and young children

The aim of this study was to evaluate the maturation of the cortical auditory evoked potential (CAEP) in humans. The participants in this experiment were 10 newborns (<7 days), 19 toddlers (13-41 months), 20 children (4-6 years) and 9 adults (18-45 years). CAEPs were obtained in response to low (400 Hz) and high (3000 Hz) tones and to the word token /baed/, all presented at 60 dB HL, at a rate of 0.22 Hz. Latency and amplitude measures were made for CAEP components P1, N1, P2 and N2 as a function of participant age, stimulus type and electrode montage. CAEP component latencies were relatively stable from birth to 6 years, but adults demonstrated significantly shorter latencies compared to infants and children. Components P1 and N2 decreased in amplitude, while components N1 and P2 increased in amplitude from birth to adulthood. Words evoked significantly larger CAEPs in newborns compared to responses evoked by tones, but in other age groups the effects of stimulus type on component amplitudes and latencies were less consistent. There was evidence of immature tonotopic organisation of the generators of N1 when responses from infants and young children were compared to those of adults. The scalp distribution of components N1 and P2 was clearly different in newborns and toddlers compared to children and adults. In the younger groups, both N1 and P2 were uniformly distributed across the scalp but in children and adults these components showed more focal distributions, with evidence of response laterality increasing with maturity. The results of the present study describe, for the first time, CAEPs recorded from multiple scalp electrodes, for tones and speech stimuli, in infants and children from birth to 6 years of age. Frequency-related differences in component amplitude were apparent at all ages reflecting development of tonotopic organisation of the CAEP neural generators.

Maturation of CAEP in infants and children: A review

This paper reviews our current understanding of the development of the obligatory cortical auditory evoked potential (CAEP) components P1, N1, P2, and N2. Firstly, the adult CAEP is briefly reviewed with respect to its morphology, neural generators and stimulus-dependence. Secondly, age-related changes occurring from the newborn period through childhood and adolescence are reviewed. The focus is on the maturation of CAEP morphology, changes in the scalp topography of the various components, changes in their amplitude and latency and in their stimulus-dependence. This review identifies periods of development in which we have only limited understanding of cortical auditory processing, as revealed by evoked potentials.

Auditory event-related potential indices of increased distractibility in children with major depression

OBJECTIVE

Children with major depression (MD) exhibit short-term memory and concentration deficits. Using auditory event-related potentials (ERPs), we aimed to determine whether these problems could be caused by a dysfunction in auditory sensory memory, attentional orienting, or both.

METHODS

The subjects were 10 treatment-naïve children with MD and 10 controls. Sound sequences, consisting of frequent stimuli (syllable /ka/, P = 0.08), infrequent deviant stimuli (/ta/, P = 0.01 ), and novel sounds ( P = 0.01 ) were played through loudspeakers while the children watched silent videos and ignored the sound stimuli. Auditory sensory memory was studied by eliciting the ERPs mismatch negativity (MMN) and late discriminative negativity (LDN), and the P3a was used as an index of involuntary attention switch.

RESULTS

The children with MD had shorter MMN and LDN latencies than the controls. The late component of the P3a (lP3a) was enhanced in amplitude in the patients as compared with that in the controls.

CONCLUSIONS

Auditory sensory memory appears to function normally in children with MD. However, the ERP findings indicated enhanced sensory sensitivity and attentional distractibility in these children. This increased distractibility might underlie the concentration difficulties that compromise school performance in children with MD.

Event-related potentials associated with sound discrimination versus novelty detection in children

In children, deviant sounds in an oddball paradigm elicit a mismatch negativity (MMN) indexing discrimination of sound change and late difference negativity (LDN) with unknown functional significance. Salient sounds elicit an ERP index if orienting, P3a, and a late negative component, Nc. We compared children's responses elicited by moderate sound changes and novel sounds to examine the relationships between MMN and LDN, and LDN and Nc. Two components of the Nc, the Nc1 and Nc2, were identified. The scalp topography of LDN differed from those of the MMN and Nc1. Children's early P3a appeared mature but late P3a lacked frontal predominance. The findings suggested that LDN is not linked with either the sensory or attentional processing. It might reflect cognitive, albeit preattentive, processing of sound change. The Nc1 appears to reflect cognitive attentive processing of salient stimuli and the Nc2 might reflect reorienting after distraction.

Deficient speech-sound processing, as shown by the electrophysiologic brain mismatch negativity response, and naming ability in prematurely born children

Very low birth weight (VLBW, <1500 g) preterm birth has been associated with anatomic abnormalities in brain development and cognitive and language disorders. We examined object naming ability, and an electrophysiologic index of auditory sensory discrimination of speech sounds (the mismatch negativity, MMN) in 4-year-old VLBW prematurely born children. We found that half of the VLBW children were inferior to their controls in the object naming ability. Also the MMN amplitudes were smaller in the preterm group as compared with the controls. Further, the MMN amplitude varied as a function of children's performance on object naming, such that the weaker object-naming performance of the preterm group was paralleled by the diminished MMN amplitudes. Therefore, difficulties in auditory discrimination seem to be implicated in language difficulties encountered in VLBW prematurely born children.