Event-related potential features indexing central auditory discrimination by newborns

Probing Beat Perception with Event-Related Potentials (ERPs) in Human Adults, Newborns, and Nonhuman Primates

The aim of this chapter is to give an overview of how the perception of rhythmic temporal regularity such as a regular beat in music can be studied in human adults, human newborns, and nonhuman primates using event-related brain potentials (ERPs). First, we discuss different aspects of temporal structure in general, and musical rhythm in particular, and we discuss the possible mechanisms underlying the perception of regularity (e.g., a beat) in rhythm. Additionally, we highlight the importance of dissociating beat perception from the perception of other types of structure in rhythm, such as predictable sequences of temporal intervals, ordinal structure, and rhythmic grouping. In the second section of the chapter, we start with a discussion of auditory ERPs elicited by infrequent and frequent sounds: ERP responses to regularity violations, such as mismatch negativity (MMN), N2b, and P3, as well as early sensory responses to sounds, such as P1 and N1, have been shown to be instrumental in probing beat perception. Subsequently, we discuss how beat perception can be probed by comparing ERP responses to sounds in regular and irregular sequences, and by comparing ERP responses to sounds in different metrical positions in a rhythm, such as on and off the beat or on strong and weak beats. Finally, we will discuss previous research that has used the aforementioned ERPs and paradigms to study beat perception in human adults, human newborns, and nonhuman primates. In doing so, we consider the possible pitfalls and prospects of the technique, as well as future perspectives.

Early maturation of sound duration processing in the infant's brain

The ability to process sound duration is crucial already at a very early age for laying the foundation for the main functions of auditory perception, such as object perception and music and language acquisition. With the availability of age-appropriate structural anatomical templates, we can reconstruct EEG source activity with much-improved reliability. The current study capitalized on this possibility by reconstructing the sources of event-related potential (ERP) waveforms sensitive to sound duration in 4- and 9-month-old infants. Infants were presented with short (200 ms) and long (300 ms) sounds equiprobable delivered in random order. Two temporally separate ERP waveforms were found to be modulated by sound duration. Generators of these waveforms were mainly located in the primary and secondary auditory areas and other language-related regions. The results show marked developmental changes between 4 and 9 months, partly reflected by scalp-recorded ERPs, but appearing in the underlying generators in a far more nuanced way. The results also confirm the feasibility of the application of anatomical templates in developmental populations.

Challenges and new perspectives of developmental cognitive EEG studies

Despite shared procedures with adults, electroencephalography (EEG) in early development presents many specificities that need to be considered for good quality data collection. In this paper, we provide an overview of the most representative early cognitive developmental EEG studies focusing on the specificities of this neuroimaging technique in young participants, such as attrition and artifacts. We also summarize the most representative results in developmental EEG research obtained in the time and time-frequency domains and use more advanced signal processing methods. Finally, we briefly introduce three recent standardized pipelines that will help promote replicability and comparability across experiments and ages. While this paper does not claim to be exhaustive, it aims to give a sufficiently large overview of the challenges and solutions available to conduct robust cognitive developmental EEG studies.

Relevance to the higher order structure may govern auditory statistical learning in neonates

Hearing is one of the earliest senses to develop and is quite mature by birth. Contemporary theories assume that regularities in sound are exploited by the brain to create internal models of the environment. Through statistical learning, internal models extrapolate from patterns to predictions about subsequent experience. In adults, altered brain responses to sound enable us to infer the existence and properties of these models. In this study, brain potentials were used to determine whether newborns exhibit context-dependent modulations of a brain response that can be used to infer the existence and properties of internal models. Results are indicative of significant context-dependence in the responsivity to sound in newborns. When common and rare sounds continue in stable probabilities over a very long period, neonates respond to all sounds equivalently (no differentiation). However, when the same common and rare sounds at the same probabilities alternate over time, the neonate responses show clear differentiations. The context-dependence is consistent with the possibility that the neonate brain produces more precise internal models that discriminate between contexts when there is an emergent structure to be discovered but appears to adopt broader models when discrimination delivers little or no additional information about the environment.

Cortical auditory evoked potentials in 1-month-old infants predict language outcomes at 12 months

The neurophysiological assessment of infants in their first developmental year can provide important information about the functional changes of the brain and supports the study of behavioral and developmental characteristics. Infants' cortical auditory evoked potentials (CAEPs) reflect cortical maturation and appear to predict subsequent language abilities. This study aimed to identify CAEP components to two auditory stimulus intensities in 1-month-old infants and to understand how these are associated with social interactive and self-regulatory behaviors. In addition, it examined whether CAEPs predicted developmental outcomes when infants were assessed at 12 months of age. At 1 month, P2 and N2 components were present for both auditory stimulus intensities, with an increased P2 amplitude being observed for the higher-intensity stimuli. We also observed that an increased P2 amplitude in the lower intensity predicted receptive and expressive language competencies at 12 months. These results are consistent with previous findings indicating an association between auditory processing and developmental outcomes in infants. This study suggests that specific auditory neurophysiological markers are associated with developmental outcomes in the first developmental year.

The prenatal brain readiness for speech processing: A review on foetal development of auditory and primordial language networks

Despite consolidated evidence for the prenatal ability to elaborate and respond to sounds and speech stimuli, the ontogenetic functional brain maturation of language responsiveness in the foetus is still poorly understood. Recent advances in in-vivo foetal neuroimaging have contributed to a finely detailed picture of the anatomo-functional hallmarks that define the prenatal neurodevelopment of auditory and language-related networks. Here, we first outline available evidence for the prenatal development of auditory and language-related brain structures and of their anatomical connections. Second, we focus on functional connectivity data showing the emergence of auditory and primordial language networks in the foetal brain. Third, we recapitulate functional neuroimaging studies assessing the prenatal readiness for sound processing, as a crucial prerequisite for the foetus to experientially respond to spoken language. In conclusion, we suggest that the state of the art has reached sufficient maturity to directly assess the neural mechanisms underlying the prenatal readiness for speech processing and to evaluate whether foetal neuromarkers can predict the postnatal development of language acquisition abilities and disabilities.

Neural and psychophysiological correlates of social communication development: Evidence from sensory processing, motor, cognitive, language and emotional behavioral milestones across infancy

This article presents a literature review focusing on the neural and psychophysiological correlates associated with social communication development in infancy. Studies presenting evidence on infants' brain activity and developments in infant sensory processing, motor, cognitive, language, and emotional abilities are described in regard to the neuropsychophysiological processes underlying the emergence of these specific behavioral milestones and their associations with social communication development. Studies that consider specific age-related characteristics across the infancy period are presented. Evidence suggests that specific neural and physiological signatures accompany age-related social communication development during the first 18 months of life.

Dynamic effects of habituation and novelty detection on newborn event-related potentials

Newborns habituate to repeated auditory stimuli, and discriminate syllables, generating opportunities for early language learning. This study investigated trial-by-trial changes in newborn electrophysiological responses to auditory speech syllables as an index of habituation and novelty detection. Auditory event-related potentials (ERPs) were recorded from 16 term newborn infants, aged 1-3 days, in response to monosyllabic speech syllables presented during habituation and novelty detection tasks. Multilevel models demonstrated that newborns habituated to repeated auditory syllables, as ERP amplitude attenuated for a late-latency component over successive trials. Subsequently, during the novelty detection task, early- and late-latency component amplitudes decreased over successive trials for novel syllables only, indicating encoding of the novel speech syllable. We conclude that newborns dynamically encoded novel syllables over relatively short time periods, as indicated by a systematic change in response patterns with increased exposure. These results have important implications for understanding early precursors of learning and memory in newborns.

Musical playschool activities are linked to faster auditory development during preschool-age: a longitudinal ERP study

The influence of musical experience on brain development has been mostly studied in school-aged children with formal musical training while little is known about the possible effects of less formal musical activities typical for preschool-aged children (e.g., before the age of seven). In the current study, we investigated whether the amount of musical group activities is reflected in the maturation of neural sound discrimination from toddler to preschool-age. Specifically, we recorded event-related potentials longitudinally (84 recordings from 33 children) in a mismatch negativity (MMN) paradigm to different musically relevant sound changes at ages 2–3, 4–5 and 6–7 years from children who attended a musical playschool throughout the follow-up period and children with shorter attendance to the same playschool. In the first group, we found a gradual positive to negative shift in the polarities of the mismatch responses while the latter group showed little evidence of age-related changes in neural sound discrimination. The current study indicates that the maturation of sound encoding indexed by the MMN may be more protracted than once thought and provides first longitudinal evidence that even quite informal musical group activities facilitate the development of neural sound discrimination during early childhood.

Healthy full-term infants' brain responses to emotionally and linguistically relevant sounds using a multi-feature mismatch negativity (MMN) paradigm

We evaluated the feasibility of a multi-feature mismatch negativity (MMN) paradigm in studying auditory processing of healthy newborns. The aim was to examine the automatic change-detection and processing of semantic and emotional information in speech in newborns. Brain responses of 202 healthy newborns were recorded with a multi-feature paradigm including a Finnish bi-syllabic pseudo-word/ta-ta/as a standard stimulus, six linguistically relevant deviant stimuli and three emotionally relevant stimuli (happy, sad, angry). Clear responses to emotional sounds were found already at the early latency window 100-200 ms, whereas responses to linguistically relevant minor changes and emotional stimuli at the later latency window 300-500 ms did not reach significance. Moreover, significant interaction between gender and emotional stimuli was found in the early latency window. Further studies on using multi-feature paradigms with linguistic and emotional stimuli in newborns are needed, especially those containing of follow-ups, enabling the assessment of the predictive value of early variations between subjects.

Cortical responses to tone and phoneme mismatch as a predictor of dyslexia? A systematic review

Evidence from event-related-potential (ERP) studies has repeatedly shown differences in the perception and processing of auditory stimuli in children with dyslexia compared to control children. The mismatch negativity (MMN) - an ERP component reflecting passive auditory change detection ability - has been found to be reduced, not only in children with a diagnosis of dyslexia, but also in infants and preschool children at risk of developing dyslexia. However, the results are controversial due to the different methods, age of the children and stimuli used. The aim of the present review is to summarize and evaluate the MMN research about at-risk children in order to identify risk factors that discriminate between children with and without dyslexia risk and to analyze if the MMR (the abbreviation refers to positive and negative mismatch responses) correlates with later reading and spelling ability. A literature search yielded 17 studies reporting MMR to speech or non-speech stimuli in children at risk of dyslexia. The results of the studies were inconsistent. Studies measuring speech MMR often found attenuated amplitudes in the at-risk group, but mainly in very young children. The results for older children (6-7years) and for non-speech stimuli are more heterogeneous. A moderate positive correlation of MMR amplitude size with later reading and spelling abilities was consistently found. Overall, the findings of this review indicate that the MMR can be a valuable part of early dyslexia identification, which can enable efficient support and intervention for a child before the first problems appear.

Habituation as Parameter for Prediction of Mental Development in Healthy Preterm Infants: An Electrophysiological Pilot Study

The aim of this prospective pilot study was to evaluate the predictive value of discrimination and habituation, which was measured by mismatch negativity in 17 healthy very preterm (mean gestational age 27.4 weeks; range 25.0-31.3) and 16 term (mean gestational age 40.3 weeks; range 37.9-41.7) born infants at term equivalent age. Developmental outcome was measured by Bayley Scales of Infant Development-I in 13 preterm and 13 term-born children at a mean age of 21.7 months (±2.18) and 18.5 months (±1.9), respectively. No differences in amplitude and latency of the mismatch negativity were found between both groups at term equivalent age. Within the preterm group habituation capacity was positively correlated with the Mental Developmental Index (r = .654, P = .008) and Performance Developmental Index (r = .482, P = .048) at 21 months. Early learning capability, as measured by habituation, may be associated with a better prognosis for early mental development in healthy preterm infants.

Pre-attentive auditory discrimination skill in Indian classical vocal musicians and non-musicians

Objective

To test for pre-attentive auditory discrimination skills in Indian classical vocal musicians and non-musicians.

Design

Mismatch negativity (MMN) was recorded to test for pre-attentive auditory discrimination skills with a pair of stimuli of /1000 Hz/ and /1100 Hz/, with /1000 Hz/ as the frequent stimulus and /1100 Hz/ as the infrequent stimulus. Onset, offset and peak latencies were the considered latency parameters, whereas peak amplitude and area under the curve were considered for amplitude analysis.

Study sample

Exactly 50 participants, out of which the experimental group had 25 adult Indian classical vocal musicians and 25 age-matched non-musicians served as the control group, were included in the study. Experimental group participants had a minimum professional music experience in Indian classic vocal music of 10 years. However, control group participants did not have any formal training in music.

Results

Descriptive statistics showed better waveform morphology in the experimental group as compared to the control. MANOVA showed significantly better onset latency, peak amplitude and area under the curve in the experimental group but no significant difference in the offset and peak latencies between the two groups.

Conclusion

The present study probably points towards the enhancement of pre-attentive auditory discrimination skills in Indian classical vocal musicians compared to non-musicians. It indicates that Indian classical musical training enhances pre-attentive auditory discrimination skills in musicians, leading to higher peak amplitude and a greater area under the curve compared to non-musicians.

Enhanced auditory evoked potentials in musicians: A review of recent findings

Auditory evoked potentials serve as an objective mode for assessment to check the functioning of the auditory system and neuroplasticity. Literature has reported enhanced electrophysiological responses in musicians, which shows neuroplasticity in musicians. Various databases including PubMed, Google, Google Scholar and Medline were searched for references related to auditory evoked potentials in musicians from 1994 till date. Different auditory evoked potentials in musicians have been summarized in the present article. The findings of various studies may support as evidences for music-induced neuroplasticity which can be used for the treatment of various clinical disorders. The search results showed enhanced auditory evoked potentials in musicians compared to non-musicians from brainstem to cortical levels. Also, the present review showed enhanced attentive and pre-attentive skills in musicians compared to non-musicians.

Comparison of Pre-Attentive Auditory Discrimination at Gross and Fine Difference between Auditory Stimuli

Introduction Mismatch Negativity is a negative component of the event-related potential (ERP) elicited by any discriminable changes in auditory stimulation.

Objective The present study aimed to assess pre-attentive auditory discrimination skill with fine and gross difference between auditory stimuli.

Method Seventeen normal hearing individual participated in the study. To assess pre-attentive auditory discrimination skill with fine difference between auditory stimuli, we recorded mismatch negativity (MMN) with pair of stimuli (pure tones), using /1000 Hz/ and /1010 Hz/ with /1000 Hz/ as frequent stimulus and /1010 Hz/ as infrequent stimulus. Similarly, we used /1000 Hz/ and /1100 Hz/ with /1000 Hz/ as frequent stimulus and /1100 Hz/ as infrequent stimulus to assess pre-attentive auditory discrimination skill with gross difference between auditory stimuli. The study included 17 subjects with informed consent. We analyzed MMN for onset latency, offset latency, peak latency, peak amplitude, and area under the curve parameters.

Result Results revealed that MMN was present only in 64% of the individuals in both conditions. Further Multivariate Analysis of Variance (MANOVA) showed no significant difference in all measures of MMN (onset latency, offset latency, peak latency, peak amplitude, and area under the curve) in both conditions.

Conclusion The present study showed similar pre-attentive skills for both conditions: fine (1000 Hz and 1010 Hz) and gross (1000 Hz and 1100 Hz) difference in auditory stimuli at a higher level (endogenous) of the auditory system.

Present and past: Can writing abilities in school children be associated with their auditory discrimination capacities in infancy?

Literacy acquisition is highly associated with auditory processing abilities, such as auditory discrimination. The event-related potential Mismatch Response (MMR) is an indicator for cortical auditory discrimination abilities and it has been found to be reduced in individuals with reading and writing impairments and also in infants at risk for these impairments. The goal of the present study was to analyze the relationship between auditory speech discrimination in infancy and writing abilities at school age within subjects, and to determine when auditory speech discrimination differences, relevant for later writing abilities, start to develop. We analyzed the MMR registered in response to natural syllables in German children with and without writing problems at two points during development, that is, at school age and at infancy, namely at age 1 month and 5 months. We observed MMR related auditory discrimination differences between infants with and without later writing problems, starting to develop at age 5 months-an age when infants begin to establish language-specific phoneme representations. At school age, these children with and without writing problems also showed auditory discrimination differences, reflected in the MMR, confirming a relationship between writing and auditory speech processing skills. Thus, writing problems at school age are, at least, partly grounded in auditory discrimination problems developing already during the first months of life.

The Basis for Language Acquisition: Congenitally Deaf Infants Discriminate Vowel Length in the First Months after Cochlear Implantation

One main incentive for supplying hearing impaired children with a cochlear implant is the prospect of oral language acquisition. Only scarce knowledge exists, however, of what congenitally deaf children actually perceive when receiving their first auditory input, and specifically what speech-relevant features they are able to extract from the new modality. We therefore presented congenitally deaf infants and young children implanted before the age of 4 years with an oddball paradigm of long and short vowel variants of the syllable /ba/. We measured the EEG in regular intervals to study their discriminative ability starting with the first activation of the implant up to 8 months later. We were thus able to time-track the emerging ability to differentiate one of the most basic linguistic features that bears semantic differentiation and helps in word segmentation, namely, vowel length. Results show that already 2 months after the first auditory input, but not directly after implant activation, these early implanted children differentiate between long and short syllables. Surprisingly, after only 4 months of hearing experience, the ERPs have reached the same properties as those of the normal hearing control group, demonstrating the plasticity of the brain with respect to the new modality. We thus show that a simple but linguistically highly relevant feature such as vowel length reaches age-appropriate electrophysiological levels as fast as 4 months after the first acoustic stimulation, providing an important basis for further language acquisition.

Development of subcortical speech representation in human infants

Previous studies have evaluated representation of the fundamental frequency (F0) in the frequency following response (FFR) of infants, but the development of other aspects of the FFR, such as timing and harmonics, has not yet been examined. Here, FFRs were recorded to a speech syllable in 28 infants, ages three to ten months. The F0 amplitude of the response was variable among individuals but was strongly represented in some infants as young as three months of age. The harmonics, however, showed a systematic increase in amplitude with age. In the time domain, onset, offset, and inter-peak latencies decreased with age. These results are consistent with neurophysiological studies indicating that (1) phase locking to lower frequency sounds emerges earlier in life than phase locking to higher frequency sounds and (2) myelination continues to increase in the first year of life. Early representation of low frequencies may reflect greater exposure to low frequency stimulation in utero. The improvement in temporal precision likely parallels an increase in the efficiency of neural transmission accompanied by exposure to speech during the first year of life.

Effects of caffeine treatment for apnea of prematurity on cortical speech-sound differentiation in preterm infants

Caffeine, standard treatment for apnea of prematurity, improves brainstem auditory processing. We hypothesized that caffeine also improves cortical differentiation of complex speech sounds. We used event-related potential methodology to measure responses to speech-sound contrasts in 45 intensive care neonates, stratified by cumulative exposure as no-, low-, and high-caffeine groups. Sound differentiation in the low-caffeine group and near-term no-caffeine infants was similar with repeated measures analysis of variance controlling for gestational and postnatal age. However, a generalized estimating equation approach demonstrated that, at equivalent postnatal age, differentiation was reduced in the high-caffeine (gestational age 25 weeks) compared to the low-caffeine group (gestational age 28 weeks), reflecting the importance of maturity at birth (Z = 2.77, P < .006). We conclude that caffeine improves measures of auditory processing associated with improved neurodevelopmental outcomes in preterm infants. However, current usage of caffeine for apnea of prematurity cannot fully compensate for the effects of brain immaturity on speech sound processing.

Auditory evoked potential response and hearing loss: a review

Hypoacusis is the most prevalent sensory disability in the world and consequently, it can lead to impede speech in human beings. One best approach to tackle this issue is to conduct early and effective hearing screening test using Electroencephalogram (EEG). EEG based hearing threshold level determination is most suitable for persons who lack verbal communication and behavioral response to sound stimulation. Auditory evoked potential (AEP) is a type of EEG signal emanated from the brain scalp by an acoustical stimulus. The goal of this review is to assess the current state of knowledge in estimating the hearing threshold levels based on AEP response. AEP response reflects the auditory ability level of an individual. An intelligent hearing perception level system enables to examine and determine the functional integrity of the auditory system. Systematic evaluation of EEG based hearing perception level system predicting the hearing loss in newborns, infants and multiple handicaps will be a priority of interest for future research.

Detecting the temporal structure of sound sequences in newborn infants

Most high-level auditory functions require one to detect the onset and offset of sound sequences as well as registering the rate at which sounds are presented within the sound trains. By recording event-related brain potentials to onsets and offsets of tone trains as well as to changes in the presentation rate, we tested whether these fundamental auditory capabilities are functional at birth. Each of these events elicited significant event-related potential components in sleeping healthy neonates. The data thus demonstrate that the newborn brain is sensitive to these acoustic features suggesting that infants are geared towards the temporal aspects of segregating sound sources, speech and music perception already at birth.

Stability of P50 auditory sensory gating during sleep from infancy to 4 years of age

The stability of cerebral inhibition was assessed across early childhood using a paired-click auditory sensory gating paradigm. The P50 ERP was measured during REM (or its infant analogue, active sleep) and NREM sleep in 14 children at approximately 3 months of age and again at approximately 4 years of age. Evoked response amplitudes, latencies, and the S2/S1 ratio of the amplitudes of the evoked responses were compared between the two visits. Significant reliability was found for the S2/S1 ratio (r = .73, p = .003) during REM but not non REM sleep (r = -.05, p = .88). A significant stimulus number by sleep stage interaction (F(1,12) = 17.1, p = .001) demonstrated that the response to the second stimulus decreased during REM but not NREM sleep. These findings suggest that this measure is stable during REM sleep across early childhood, is not affected by age, and is sleep-state dependent. P50 sensory gating is a biomarker which, if used properly, may provide a mechanism to further explore changes in the developing brain or may help with early screening for psychiatric illness vulnerability.

Perceiving temporal regularity in music: the role of auditory event-related potentials (ERPs) in probing beat perception

The aim of this chapter is to give an overview of how the perception of a regular beat in music can be studied in humans adults, human newborns, and nonhuman primates using event-related brain potentials (ERPs). Next to a review of the recent literature on the perception of temporal regularity in music, we will discuss in how far ERPs, and especially the component called mismatch negativity (MMN), can be instrumental in probing beat perception. We conclude with a discussion on the pitfalls and prospects of using ERPs to probe the perception of a regular beat, in which we present possible constraints on stimulus design and discuss future perspectives.

Separating acoustic deviance from novelty during the first year of life: a review of event-related potential evidence

Orienting to salient events in the environment is a first step in the development of attention in young infants. Electrophysiological studies have indicated that in newborns and young infants, sounds with widely distributed spectral energy, such as noise and various environmental sounds, as well as sounds widely deviating from their context elicit an event-related potential (ERP) similar to the adult P3a response. We discuss how the maturation of event-related potentials parallels the process of the development of passive auditory attention during the first year of life. Behavioral studies have indicated that the neonatal orientation to high-energy stimuli gradually changes to attending to genuine novelty and other significant events by approximately 9 months of age. In accordance with these changes, in newborns, the ERP response to large acoustic deviance is dramatically larger than that to small and moderate deviations. This ERP difference, however, rapidly decreases within first months of life and the differentiation of the ERP response to genuine novelty from that to spectrally rich but repeatedly presented sounds commences during the same period. The relative decrease of the response amplitudes elicited by high-energy stimuli may reflect development of an inhibitory brain network suppressing the processing of uninformative stimuli. Based on data obtained from healthy full-term and pre-term infants as well as from infants at risk for various developmental problems, we suggest that the electrophysiological indices of the processing of acoustic and contextual deviance may be indicative of the functioning of auditory attention, a crucial prerequisite of learning and language development.

Infants' brain responses for speech sound changes in fast multifeature MMN paradigm

OBJECTIVE

We investigated whether newborn speech-sound discrimination can be studied in 40 min using fast multifeature mismatch negativity (MMN) paradigm and do the results differ from those obtained with the traditional oddball paradigm.

METHODS

Newborns' MMN responses to five types of changes (consonant identity, F0, intensity, vowel duration and vowel identity) were recorded in the multifeature group (N=15) and vowel duration and vowel identity changes in the oddball group (N=13), after which the MMNs from both groups were compared with each others.

RESULTS

Statistically significant MMNs in the 190-600 ms time range from the stimulus onset were found for most change types in both paradigms. Newborn MMN responses were predominantly positive but a small number of participants elicited negative MMNs instead. MMN amplitudes did not differ between the multifeature and oddball groups.

CONCLUSIONS

Newborn speech-sound discrimination can be assessed in a short recording time using the fast multifeature paradigm.

SIGNIFICANCE

The paradigm presented here can be used to record extensive auditory discrimination profiles in newborns and assess development of speech-sound discrimination and its difficulties.

Auditory perception at the root of language learning

Learning a spoken language presupposes efficient auditory functions. In the present event-related potential study, we tested whether and how basic auditory processes are related to online learning of a linguistic rule in infants and adults. Participants listened to frequent standard stimuli, which were interspersed with infrequent pitch deviants and rule deviants, violating a nonadjacent dependency between two syllables. Only infants who showed the more mature mismatch response for the pitch deviants (i.e., a negativity) showed a mismatch response to the rule deviants. Concordantly, the small group of adults who showed evidence of rule learning showed larger mismatch effects for pitch processing. We conclude that the ability to extract linguistic rules develops in early infancy and is tightly linked to functional aspects of basic auditory mechanisms.

Recording infant ERP data for cognitive research

Researchers from different backgrounds have an increasing interest in investigating infant cognitive development using electroencephalogram (EEG) recordings. Although EEG measurements are suitable for infants, the method poses several challenges including setting up an infant-friendly, but interference-free lab environment and designing age-appropriate stimuli and paradigms. Certain specifics of infant EEG data have to be considered when deriving event-related potentials (ERPs) to investigate cognitive processes in the developing brain. The present article summarizes the practical aspects of conducting ERP research with infants and describes how researchers typically deal with the specific challenges entailed in this work.

Voice and Emotion Processing in the Human Neonatal Brain

Although the voice-sensitive neural system emerges very early in development, it has yet to be demonstrated whether the neonatal brain is sensitive to voice perception. We measured the EEG mismatch response (MMR) elicited by emotionally spoken syllables “dada” along with correspondingly synthesized nonvocal sounds, whose fundamental frequency contours were matched, in 98 full-term newborns aged 1–5 days. In Experiment 1, happy syllables relative to nonvocal sounds elicited an MMR lateralized to the right hemisphere. In Experiment 2, fearful syllables elicited stronger amplitudes than happy or neutral syllables, and this response had no sex differences. In Experiment 3, angry versus happy syllables elicited an MMR, although their corresponding nonvocal sounds did not. Here, we show that affective discrimination is selectively driven by voice processing per se rather than low-level acoustical features and that the cerebral specialization for human voice and emotion processing emerges over the right hemisphere during the first days of life.

Fast measurement of auditory event-related potential profiles in 2-3-year-olds

Auditory discrimination, memory, and attention-related functions were investigated in healthy 2-3-year-olds by recording event-related potentials (ERPs) to changes in five auditory features and two types of novel sounds using the fast multifeature paradigm (MFP). ERP profiles consisting of the mismatch negativity (MMN), P3a, and prominent late discriminative negativities (LDN) were obtained, for the first time, from this age group in a considerably shorter time compared to the traditional paradigms. Statistically significant responses from individual children were obtained mainly for the novel sounds. Thus, the MFP shows promise as a time-efficient paradigm for investigating central auditory functions in toddlers.

The effects of exercise during pregnancy on the newborn's brain: study protocol for a randomized controlled trial

BACKGROUND

It is generally accepted that an active lifestyle is beneficial for cognition in children, adults and the elderly. Recently, studies using the rat animal model found that the pups of mothers who exercised during pregnancy had increased hippocampal neurogenesis and better memory and learning abilities. The aim of this report is to present the experimental protocol of a study that is designed to verify if an active lifestyle during pregnancy in humans has an impact on the newborn's brain.

METHODS

60 pregnant women will be included in a randomized controlled study. The experimental group will be asked to exercise a minimum of 20 minutes three times per week, at a minimal intensity of 55% of their maximal aerobic capacity. The control group will not be exercising. The effect of exercise during pregnancy on the newborn's brain will be investigated 8 to 12 days postpartum by means of the mismatch negativity, a neurophysiological brain potential that is associated to auditory sensory memory. We hypothesize that children born to mothers who exercised during their pregnancy will present shorter latencies and larger mismatch negativity amplitudes, indicating more efficient auditory memory processes.

DISCUSSION

As of September 2011, 17 women have joined the study. Preliminary results show that the experimental group are active 3.1 ± 0.9 days per week while the control group only exercise 0.8 ± 0.6 days per week. The results of this study will present insight on fetal neuroplasticity and will be a valuable tool for health professionals who wish to encourage pregnant women to exercise.

TRIAL REGISTRATION

ClinicalTrials.gov registration: NTC01220778.

Influence of gestational age and postnatal age on speech sound processing in NICU infants

The study examined the effect of gestational (GA) and postnatal (PNA) age on speech sound perception in infants. Auditory event-related potentials (ERPs) were recorded in response to speech sounds (syllables) in 50 infant NICU patients (born at 24-40 weeks gestation) prior to discharge. Efficiency of speech perception was quantified as absolute difference in mean amplitudes of ERPs in response to vowel (/a/-/u/) and consonant (/b/-/g/, /d/-/g/) contrasts within 150-250, 250-400, 400-700 ms after stimulus onset. Results indicated that both GA and PNA affected speech sound processing. These effects were more pronounced for consonant than vowel contrasts. Increasing PNA was associated with greater sound discrimination in infants born at or after 30 weeks GA, while minimal PNA-related changes were observed for infants with GA less than 30 weeks. Our findings suggest that a certain level of brain maturity at birth is necessary to benefit from postnatal experience in the first 4 months of life, and both gestational and postnatal ages need to be considered when evaluating infant brain responses.

Toward an electrocortical biomarker of cognition for newborn infants

The event-related potential (ERP) effect of mismatch negativity (MMN) was the first electrophysiological probe to evaluate cognitive processing (change detection) in newborn infants. Initial studies of MMN predicted clinical utility for this measure in identification of infants at risk for developmental cognitive deficits. These predictions have not been realized. We hypothesized that in sleeping newborn infants, measures derived from wavelet assessment of power in the MMN paradigm would be more robust markers of the brain's response to stimulus change than the ERP-derived MMN. Consistent with this premise, we found increased power in response to unpredictable and infrequent tones compared to frequent tones. These increases were present at multiple locations on the scalp over a range of latencies and frequencies and occurred even in the absence of an ERP-derived MMN. There were two predominant effects. First, theta band power was elevated at middle and late latencies (200 to 600 ms), suggesting that neocortical theta rhythms that subserve working memory in adults are present at birth. Second, late latency (500 ms) increased power to the unpredictable and infrequent tones was observed in the beta and gamma bands, suggesting that oscillations involved in adult cognition are also present in the neonate. These findings support the expectation that frequency dependent measures, such as wavelet power, will improve the prospects for a clinically useful test of cortical function early in the postnatal period.

Perceptual anchoring in preschool children: not adultlike, but there

BACKGROUND

Recent studies suggest that human auditory perception follows a prolonged developmental trajectory, sometimes continuing well into adolescence. Whereas both sensory and cognitive accounts have been proposed, the development of the ability to base current perceptual decisions on prior information, an ability that strongly benefits adult perception, has not been directly explored. Here we ask whether the auditory frequency discrimination of preschool children also improves when given the opportunity to use previously presented standard stimuli as perceptual anchors, and whether the magnitude of this anchoring effect undergoes developmental changes.

METHODOLOGY/PRINCIPAL FINDINGS

Frequency discrimination was tested using two adaptive same/different protocols. In one protocol (with-reference), a repeated 1-kHz standard tone was presented repeatedly across trials. In the other (no-reference), no such repetitions occurred. Verbal memory and early reading skills were also evaluated to determine if the pattern of correlations between frequency discrimination, memory and literacy is similar to that previously reported in older children and adults. Preschool children were significantly more sensitive in the with-reference than in the no-reference condition, but the magnitude of this anchoring effect was smaller than that observed in adults. The pattern of correlations among discrimination thresholds, memory and literacy replicated previous reports in older children.

CONCLUSIONS/SIGNIFICANCE

The processes allowing the use of context to form perceptual anchors are already functional among preschool children, albeit to a lesser extent than in adults. Nevertheless, immature anchoring cannot fully account for the poorer frequency discrimination abilities of young children. That anchoring is present among the majority of typically developing preschool children suggests that the anchoring deficits observed among individuals with dyslexia represent a true deficit rather than a developmental delay.

Cortical plasticity in 4-month-old infants: specific effects of experience with musical timbres

Animal models suggest that the brain is particularly neuroplastic early in development, but previous studies have not systematically controlled the auditory environment in human infants and observed the effects on auditory cortical representations. We exposed 4-month-old infants to melodies in either guitar or marimba timbre (infants were randomly assigned to exposure group) for a total of ~160 min over the course of a week, after which we measured electroencephalogram (EEG) responses to guitar and marimba tones at pitches not previously heard during the exposure phase. A frontally negative response with a topography consistent with generation in auditory areas, peaking around 450 ms, was significantly larger for guitar than marimba tones in the guitar-exposed group but significantly larger for marimba than guitar tones in the marimba-exposed group. This indicates that experience with tones in a particular timbre affects representations for that timbre, and that this effect generalizes to tones not previously experienced during exposure. Furthermore, mismatch responses to occasional small 3% changes in pitch were larger for tones in guitar than marimba timbre only for infants exposed to guitar tones. Together these results indicate that a relatively small amount of passive exposure to a particular timbre in infancy enhances representations of that timbre and leads to more precise pitch processing for that timbre.

Source localization of event-related potentials to pitch change mapped onto age-appropriate MRIs at 6 months of age

Auditory event-related potentials (ERPs) have been used to understand how the brain processes auditory input, and to track developmental change in sensory systems. Localizing ERP generators can provide invaluable insights into how and where auditory information is processed. However, age-appropriate infant brain templates have not been available to aid such developmental mapping. In this study, auditory change detection responses of brain ERPs were examined in 6-month-old infants using discrete and distributed source localization methods mapped onto age-appropriate magnetic resonance images. Infants received a passive oddball paradigm using fast-rate non-linguistic auditory stimuli (tone doublets) with the deviant incorporating a pitch change for the second tone. Data was processed using two different high-pass filters. When a 0.5 Hz filter was used, the response to the pitch change was a large frontocentral positive component. When a 3 Hz filter was applied, two temporally consecutive components associated with change detection were seen: one with negative voltage, and another with positive voltage over frontocentral areas. Both components were localized close to the auditory cortex with an additional source near to the anterior cingulate cortex. The sources for the negative response had a more tangential orientation relative to the supratemporal plane compared to the positive response, which showed a more lateral, oblique orientation. The results described here suggest that at 6 months of age infants generate similar response patterns and use analogous cortical areas to that of adults to detect changes in the auditory environment. Moreover, the source locations and orientations, together with waveform topography and morphology provide evidence in infants for feature-specific change detection followed by involuntary switching of attention.

Event-related potentials in clinical research: guidelines for eliciting, recording, and quantifying mismatch negativity, P300, and N400

This paper describes recommended methods for the use of event-related brain potentials (ERPs) in clinical research and reviews applications to a variety of psychiatric and neurological disorders. Techniques are presented for eliciting, recording, and quantifying three major cognitive components with confirmed clinical utility: mismatch negativity (MMN), P300, and N400. Also highlighted are applications of each of the components as methods of investigating central nervous system pathology. The guidelines are intended to assist investigators who use ERPs in clinical research, in an effort to provide clear and concise recommendations and thereby to standardize methodology and facilitate comparability of data across laboratories.

Spectral vs. temporal auditory processing in specific language impairment: a developmental ERP study

Pre-linguistic sensory deficits, especially in "temporal" processing, have been implicated in developmental language impairment (LI). However, recent evidence has been equivocal with data suggesting problems in the spectral domain. The present study examined event-related potential (ERP) measures of auditory sensory temporal and spectral processing, and their interaction, in typical children and those with LI (7-17 years; n=25 per group). The stimuli were three CV syllables and three consonant-to-vowel transitions (spectral sweeps) isolated from the syllables. Each of these six stimuli appeared in three durations (transitions: 20, 50, and 80 ms; syllables: 120, 150, and 180 ms). Behaviorally, the group with LIs showed inferior syllable discrimination both with long and short stimuli. In ERPs, trends were observed in the group with LI for diminished long-latency negativities (the N2-N4 peaks) and a developmentally transient enhancement of the P2 peak. Some, but not all, ERP indices of spectral processing also showed trends to be diminished in the group with LI specifically in responses to syllables. Importantly, measures of the transition N2-N4 peaks correlated with expressive language abilities in the LI children. None of the group differences depended on stimulus duration. Therefore, sound brevity did not account for the diminished spectral resolution in these LI children. Rather, the results suggest a deficit in acoustic feature integration at higher levels of auditory sensory processing. The observed maturational trajectory suggests a non-linear developmental deviance rather than simple delay.

Finding the pitch of the missing fundamental in infants

Pitch perception is critical for the perception of speech and music, for object identification, and for auditory scene analysis, whereby representations are derived for each sounding object in the environment from the complex sound wave that reaches the ears. The perceived pitch of a complex sound corresponds to its fundamental frequency. However, removal of energy at the fundamental does not alter the pitch because adults use the harmonics to derive the pitch (Bendor and Wang, 2005; Trainor, 2008). Although sound frequency is represented subcortically, the integration of harmonics into a representation of pitch does not occur until auditory cortex (Bendor and Wang, 2005). Given that auditory cortex is immature in young infants, we examined the development of cortical representations for pitch by measuring electrophysiological (EEG) responses to pitch changes that required processing the pitch of the missing fundamental. Adults and infants 4 months and older showed a mismatch negativity response to these pitch changes, but 3-month-old infants did not. Thus, cortical representations of the pitch of the missing fundamental emerge between 3 and 4 months of age, indicating that there is a profound change in auditory perception for pitch in early infancy.