The importance of rapid auditory processing abilities to early language development: evidence from converging methodologies

Early neural disruption and auditory processing outcomes in rodent models: implications for developmental language disability

Most researchers in the field of neural plasticity are familiar with the "Kennard Principle," which purports a positive relationship between age at brain injury and severity of subsequent deficits (plateauing in adulthood). As an example, a child with left hemispherectomy can recover seemingly normal language, while an adult with focal injury to sub-regions of left temporal and/or frontal cortex can suffer dramatic and permanent language loss. Here we present data regarding the impact of early brain injury in rat models as a function of type and timing, measuring long-term behavioral outcomes via auditory discrimination tasks varying in temporal demand. These tasks were created to model (in rodents) aspects of human sensory processing that may correlate-both developmentally and functionally-with typical and atypical language. We found that bilateral focal lesions to the cortical plate in rats during active neuronal migration led to worse auditory outcomes than comparable lesions induced after cortical migration was complete. Conversely, unilateral hypoxic-ischemic (HI) injuries (similar to those seen in premature infants and term infants with birth complications) led to permanent auditory processing deficits when induced at a neurodevelopmental point comparable to human "term," but only transient deficits (undetectable in adulthood) when induced in a "preterm" window. Convergent evidence suggests that regardless of when or how disruption of early neural development occurs, the consequences may be particularly deleterious to rapid auditory processing (RAP) outcomes when they trigger developmental alterations that extend into subcortical structures (i.e., lower sensory processing stations). Collective findings hold implications for the study of behavioral outcomes following early brain injury as well as genetic/environmental disruption, and are relevant to our understanding of the neurologic risk factors underlying developmental language disability in human populations.

Word stress processing in specific language impairment: auditory or representational deficits?

Word stress processing has repeatedly been reported to be affected in specific language impairment (SLI) with potential consequences for various aspects of language development. However, it still remains unresolved whether word stress impairments in SLI are due to deficits in basic auditory processing or to a degraded phonological representation or both. We addressed this question examining an unselected sample of 10 children with SLI and 11 typically developing (TD) children, aged about 8 years, with respect to their basic auditory processing (duration and skewness discrimination) and phonological representation of prosodic (word stress) and segmental (consonant) contrasts. Our results show lower performance of the SLI group compared to the TD group in all tasks. Crucially, two subgroups of children with SLI emerged from our analyses: While one group was impaired in basic auditory perception, particularly affecting duration discrimination, the other showed no significant auditory processing deficits but a representational impairment.

Early gamma oscillations during rapid auditory processing in children with a language-learning impairment: changes in neural mass activity after training

Children with language-learning impairment (LLI) have consistently shown difficulty with tasks requiring precise, rapid auditory processing. Remediation based on neural plasticity assumes that the temporal precision of neural coding can be improved by intensive training protocols. Here, we examined the extent to which early oscillatory responses in auditory cortex change after audio-visual training, using combined source modeling and time-frequency analysis of the human electroencephalogram (EEG). Twenty-one elementary school students diagnosed with LLI underwent the intervention for an average of 32 days. Pre- and post-training assessments included standardized language/literacy tests and EEG recordings in response to fast-rate tone doublets. Twelve children with typical language development were also tested twice, with no intervention given. Behaviorally, improvements on measures of language were observed in the LLI group following completion of training. During the first EEG assessment, we found reduced amplitude and phase-locking of early (45-75 ms) oscillations in the gamma-band range (29-52 Hz), specifically in the LLI group, for the second stimulus of the tone doublet. Amplitude reduction for the second tone was no longer evident for the LLI children post-intervention, although these children still exhibited attenuated phase-locking. Our findings suggest that specific aspects of inefficient sensory cortical processing in LLI are ameliorated after training.

Developmental trends in auditory processing can provide early predictions of language acquisition in young infants

Auditory processing capabilities at the subcortical level have been hypothesized to impact an individual's development of both language and reading abilities. The present study examined whether auditory processing capabilities relate to language development in healthy 9-month-old infants. Participants were 71 infants (31 boys and 40 girls) with both Auditory Brainstem Response (ABR) and language assessments. At 6 weeks and/or 9 months of age, the infants underwent ABR testing using both a standard hearing screening protocol with 30 dB clicks and a second protocol using click pairs separated by 8, 16, and 64-ms intervals presented at 80 dB. We evaluated the effects of interval duration on ABR latency and amplitude elicited by the second click. At 9 months, language development was assessed via parent report on the Chinese Communicative Development Inventory - Putonghua version (CCDI-P). Wave V latency z-scores of the 64-ms condition at 6 weeks showed strong direct relationships with Wave V latency in the same condition at 9 months. More importantly, shorter Wave V latencies at 9 months showed strong relationships with the CCDI-P composite consisting of phrases understood, gestures, and words produced. Likewise, infants who had greater decreases in Wave V latencies from 6 weeks to 9 months had higher CCDI-P composite scores. Females had higher language development scores and shorter Wave V latencies at both ages than males. Interestingly, when the ABR Wave V latencies at both ages were taken into account, the direct effects of gender on language disappeared. In conclusion, these results support the importance of low-level auditory processing capabilities for early language acquisition in a population of typically developing young infants. Moreover, the auditory brainstem response in this paradigm shows promise as an electrophysiological marker to predict individual differences in language development in young children.

Assistive listening devices drive neuroplasticity in children with dyslexia

Children with dyslexia often exhibit increased variability in sensory and cognitive aspects of hearing relative to typically developing peers. Assistive listening devices (classroom FM systems) may reduce auditory processing variability by enhancing acoustic clarity and attention. We assessed the impact of classroom FM system use for 1 year on auditory neurophysiology and reading skills in children with dyslexia. FM system use reduced the variability of subcortical responses to sound, and this improvement was linked to concomitant increases in reading and phonological awareness. Moreover, response consistency before FM system use predicted gains in phonological awareness. A matched control group of children with dyslexia attending the same schools who did not use the FM system did not show these effects. Assistive listening devices can improve the neural representation of speech and impact reading-related skills by enhancing acoustic clarity and attention, reducing variability in auditory processing.

Contribution of temporal processing skills to reading comprehension in 8-year-olds: evidence for a mediation effect of phonological awareness

This study tested whether the association between temporal processing (TP) and reading is mediated by phonological awareness (PA) in a normative sample of 615 eight-year-olds. TP was measured with auditory and bimodal (visual-auditory) temporal order judgment tasks and PA with a phoneme deletion task. PA partially mediated the association between both auditory and bimodal TP and reading, above nonverbal abilities, vocabulary, and processing speed. PA explained a larger proportion of the association between auditory TP and reading (56% vs. 39% for bimodal TP), and most of the association between bimodal TP and reading was direct. This finding is consistent with a dual-phonological and visual-pathway model of the association between TP and reading in normative reading skills.

Electrophysiological evidence for attenuated auditory recovery cycles in children with specific language impairment

Previous research indicates that at least some children with specific language impairment (SLI) show a reduced neural response when non-linguistic tones were presented at rapid rates. However, this past research has examined older children, and it is unclear whether such deficits emerge earlier in development. It is also unclear whether atypical refractory effects differ for linguistic versus non-linguistic stimuli or can be explained by deficits in selective auditory attention reported among children with SLI. In the present study, auditory refractory periods were compared in a group of 24 young children with SLI (age 3-8 years) and 24 matched control children. Event-related brain potentials (ERPs) were recorded and compared to 100 ms linguistic and non-linguistic probe stimuli presented at inter-stimulus intervals (ISIs) of 200, 500, or 1000 ms. These probes were superimposed on story narratives when attended and ignored, permitting an experimental manipulation of selective attention within the same paradigm. Across participants, clear refractory effects were observed with this paradigm, evidenced as a reduced amplitude response from 100 to 200 ms at shorter ISIs. Children with SLI showed reduced amplitude ERPs relative to the typically-developing group at only the shortest, 200 ms, ISI and this difference was over the left-hemisphere for linguistic probes and over the right-hemisphere for non-linguistic probes. None of these effects was influenced by the direction of selective attention. Taken together, these findings suggest that deficits in the neural representation of rapidly presented auditory stimuli may be one risk factor for atypical language development.

Inhibition of X-linked inhibitor of apoptosis with embelin differentially affects male versus female behavioral outcome following neonatal hypoxia-ischemia in rats

Hypoxia-ischemia (HI; concurrent oxygen/blood deficiency) and associated encephalopathy represent a common cause of neurological injury in premature/low-birth-weight infants and term infants with birth complications. Resulting behavioral impairments include cognitive and/or sensory processing deficits, as well as language disabilities, and clinical evidence shows that male infants with HI exhibit more severe cognitive deficits compared to females with equivalent injury. Evidence also demonstrates activation of sex-dependent apoptotic pathways following HI events, with males preferentially activating a caspase-independent cascade of cell death and females preferentially activating a caspase-dependent cascade following neonatal hypoxic and/or ischemic insults. Based on these combined data, the 'female protection' following HI injury may reflect the endogenous X-linked inhibitor of apoptosis (XIAP), which effectively binds effector caspases and halts downstream cleavage of effector caspases (thus reducing cell death). To test this theory, the current study utilized neonatal injections of vehicle or embelin (a small molecule inhibitor of XIAP) in male and female rats with or without induced HI injury on postnatal day 7 (P7). Subsequent behavioral testing using a clinically relevant task revealed that the inhibition of XIAP exacerbated HI-induced persistent behavioral deficits in females, with no effect on HI males. These results support sex differences in mechanisms of cell death following early HI injuries, and suggest a potential clinical benefit from the development of sex-specific neuroprotectants for the treatment of HI.

Reprint of "Early testosterone modulated sex differences in behavioral outcome following neonatal hypoxia ischemia in rats"

Hypoxia ischemia (HI; reduced blood oxygenation and/or flow to the brain) represents one of the most common injuries for both term and preterm/very low birth weight (VLBW) infants. These children experience elevated incidence of cognitive and/or sensory processing disabilities, including language based learning disabilities. Clinical data also indicate more substantial long-term deficits for HI injured male babies as compared to HI injured females. Previously, we reported significant deficits in rapid auditory processing and spatial learning in male rats with postnatal day 1 (P1), P7, or P10 HI injury. We also showed sex differences in HI injured animals, with more severe deficits in males as compared to females. Given these findings, combined with extant clinical data, the current study sought to assess a putative role for perinatal testosterone in modulating behavioral outcome following early hypoxic-ischemic injury in rats. Male, female, and testosterone-propionate (TP) treated females were subjected to P7 HI or sham surgery, and subsequently (P30+) underwent a battery of auditory testing and water maze assessment. Results confirm previous reports of sex differences following HI, and add new findings of significantly worse performance in TP-treated HI females compared to vehicle treated HI females. Post mortem anatomic analyses showed consistent effects, with significant brain weight decreases seen in HI male and TP-treated HI females but not female HI or sham groups. Further neuromorphometric analysis of brain structures showed that HI male animals exhibited increased pathology relative to HI females as reflected in ventricular enlargement. Findings suggest that neonatal testosterone may act to enhance the deleterious consequences of early HI brain injury, as measured by both neuropathology and behavior.

Effects of acoustic complexity on processing sound intensity in 10- to 11-year-old children: evidence from cortical auditory evoked potentials

OBJECTIVES/HYPOTHESIS

The environmental complexity that sounds are presented in, as well as the stimulus presentation rate, influences how sound intensity is centrally encoded with differences between children and adults.

STUDY DESIGN

Cortical auditory evoked potential (CAEP) comparison study in children and adults examining two stimulus rates and three different stimulus contexts.

METHODS

Twelve 10 and 11 year olds and 11 adults were studied in two experiments examining the CAEP to a 1-KHz, 50-ms tone. A Slow-Rate experiment at 750-ms stimulus onset asynchrony (SOA) compared the CAEPs of 78 dB to 86 dB SPL in 2 complexity conditions. A Fast-Rate experiment was performed at 125 ms SOA with the same conditions plus an additional complexity condition. Repeated measures and mixed-model analysis of variance (ANOVA) was used to examine the latency and amplitude of the CAEP components.

RESULTS

CAEP amplitudes and latencies were significantly affected by rate, intensity, and age with complexity interacting in multiple mixed-mode ANOVAs. P1 was the only CAEP component present at the Fast Rate. There were main effects of rate, age, and stimulus intensity level on the CAEP amplitudes and latencies. Maturational differences were seen in the interactions of intensity with complexity for the different CAEP components.

CONCLUSIONS

Complexity of the sound environment was reflected in the relative amplitude of the CAEPs evoked by sound intensity. The effect of stimulus intensity depended on the complexity of the surrounding environment. Effects of the surrounding sounds were different in children than in adults.

Infant brain responses associated with reading-related skills before school and at school age

INTRODUCTION

In Jyväskylä Longitudinal Study of Dyslexia, we have investigated neurocognitive processes related to phonology and other risk factors of later reading problems. Here we review studies in which we have investigated whether dyslexic children with familial risk background would show atypical auditory/speech processing at birth, at six months and later before school and at school age as measured by brain event-related potentials (ERPs), and how infant ERPs are related to later pre-reading cognitive skills and literacy outcome.

PATIENTS AND METHODS

One half of the children came from families with at least one dyslexic parent (the at-risk group), while the other half belonged to the control group without any familial background of dyslexia.

RESULTS

Early ERPs were correlated to kindergarten age phonological processing and letter-naming skills as well as phoneme duration perception, reading and writing skills at school age. The correlations were, in general, more consistent among at-risk children. Those at-risk children who became poor readers also differed from typical readers in the infant ERP measures at the group level. ERPs measured before school and at the 3rd grade also differed between dyslexic and typical readers. Further, speech perception at behavioural level differed between dyslexic and typical readers, but not in all dyslexic readers.

CONCLUSIONS

These findings suggest persisting developmental differences in the organization of the neural networks sub-serving auditory and speech perception, with cascading effects on later reading related skills, in children with familial background for dyslexia. However, atypical auditory/speech processing is not likely a sufficient reason by itself for dyslexia but rather one endophenotype or risk factor.

Reduced Sensory Oscillatory Activity during Rapid Auditory Processing as a Correlate of Language-Learning Impairment

Successful language acquisition has been hypothesized to involve the ability to integrate rapidly presented, brief acoustic cues in sensory cortex. A body of work has suggested that this ability is compromised in language-learning impairment (LLI). The present research aimed to examine sensory integration during rapid auditory processing by means of electrophysiological measures of oscillatory brain activity using data from a larger longitudinal study. Twenty-nine children with LLI and control participants with typical language development (n=18) listened to tone doublets presented at a temporal interval that is essential for accurate speech processing (70-ms interstimulus interval). The children performed a deviant (pitch change of second tone) detection task, or listened passively. The electroencephalogram was recorded from 64 electrodes. Data were source-projected to the auditory cortices and submitted to wavelet analysis, resulting in time-frequency representations of electrocortical activity. Results show significantly reduced amplitude and phase-locking of early (45-75 ms) oscillations in the gamma-band range (29-52 Hz), specifically in the LLI group, for the second stimulus of the tone doublet. This suggests altered temporal organization of sensory oscillatory activity in LLI when processing rapid sequences.

Early testosterone modulated sex differences in behavioral outcome following neonatal hypoxia ischemia in rats

Hypoxia ischemia (HI; reduced blood oxygenation and/or flow to the brain) represents one of the most common injuries for both term and preterm/very low birth weight (VLBW) infants. These children experience elevated incidence of cognitive and/or sensory processing disabilities, including language based learning disabilities. Clinical data also indicate more substantial long-term deficits for HI injured male babies as compared to HI injured females. Previously, we reported significant deficits in rapid auditory processing and spatial learning in male rats with postnatal day 1 (P1), P7, or P10 HI injury. We also showed sex differences in HI injured animals, with more severe deficits in males as compared to females. Given these findings, combined with extant clinical data, the current study sought to assess a putative role for perinatal testosterone in modulating behavioral outcome following early hypoxic-ischemic injury in rats. Male, female, and testosterone-propionate (TP) treated females were subjected to P7 HI or sham surgery, and subsequently (P30+) underwent a battery of auditory testing and water maze assessment. Results confirm previous reports of sex differences following HI, and add new findings of significantly worse performance in TP-treated HI females compared to vehicle treated HI females. Post mortem anatomic analyses showed consistent effects, with significant brain weight decreases seen in HI male and TP-treated HI females but not female HI or sham groups. Further neuromorphometric analysis of brain structures showed that HI male animals exhibited increased pathology relative to HI females as reflected in ventricular enlargement. Findings suggest that neonatal testosterone may act to enhance the deleterious consequences of early HI brain injury, as measured by both neuropathology and behavior.

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.

Environmental noise affects auditory temporal processing development and NMDA-2B receptor expression in auditory cortex

Auditory temporal processing is essential for sound discrimination and speech comprehension. Under normal developmental conditions, temporal processing acuity improves with age. As recent animal studies have shown that the functional development of the auditory cortex (AC) is impaired by early life exposure to environmental noise (i.e., continuous, moderate-level, white noise), here we investigated whether the normal age-related improvement in temporal processing acuity is sensitive to delayed development of the AC. We used a behavioral paradigm, the gap-induced prepulse inhibition of the acoustic startle reflex, to assess the gap detection threshold, and provide a comparison of temporal processing acuity between environmental noise-reared rats and age-matched controls. Moreover, because age-related changes normally occur in the relative expression of different N-methyl-D-aspartate (NMDA) receptor subunits, we assessed the level of protein expression of NMDA-2A and 2B receptors (NR2A and NR2B respectively) in the AC after environmental noise-rearing. As hypothesized, rats reared in environmental noise showed (1) poor temporal processing acuity as adults (i.e., gap detection threshold remained elevated at a juvenile-like level), and (2) an increased level of NR2B protein expression compared to age-matched controls. This poor temporal processing acuity represented delayed development rather than permanent impairment, as moving these environmental noise-reared rats to normal acoustic conditions improved their gap detection threshold to an age-appropriate level. Furthermore, housing normally reared, adult rats in environmental noise for two months did not affect their already-mature gap detection threshold. Thus, masking normal sound inputs with environmental noise during early life, but not adulthood, impairs temporal processing acuity as assessed with the gap detection threshold.

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.

Newborn event-related potentials predict poorer pre-reading skills in children at risk for dyslexia

Earlier results from the Jyväskylä Longitudinal Study of Dyslexia showed that newborn event-related potentials (ERPs) of children with and without familial risk for dyslexia were associated with receptive language and verbal memory skills between 2.5 and 5 years of age. We further examined whether these ERPs (responses to synthetic consonant-vowel syllables /ba/, /da/, /ga/; presented equiprobably with 3,910-7,285 ms interstimulus intervals) predict later pre-reading skills measured before the onset of school (6.5 years of age). In line with our earlier results, the at-risk children (N = 11) with atypical speech processing in the right hemisphere (a slower shift in polarity from positivity to negativity in responses to /ga/ at 540-630 ms) scored significantly lower in phonological skills, rapid naming, and letter knowledge than the control children (N = 10) without enhanced right hemispheric speech processing. These results further extend our earlier findings of newborn ERPs in predicting poorer language skills. These consistent differences in ERPs to speech sounds may have applications in the future for the early identification of children at risk for developmental language problems. This would facilitate well-directed intervention even before reading problems are typically diagnosed.

Early development of brain responses to rapidly presented auditory stimulation: a magnetoencephalographic study

BACKGROUND

The processing of rapidly presented stimuli has been shown to be a precursor for the perception of speech in infants, long before they learn to speak. However, the onset and early development of rapid temporal processing (RTP) skills is not yet well understood. The main goal of this study was to assess the development of RTP skills during the prenatal and early postnatal stages of life.

METHODOLOGY

Tone pairs were presented in two difficulties (long and short) and event-related magnetic fields were recorded using MEG. Pregnant women (22) (gestational ages between 29 and 38 weeks') participated in the fetal study and 15 returned for a neonatal follow-up study between 2 and 38 days after delivery or 38 and 44 weeks gestational age (GA).

RESULTS

In the postnatal follow-up study, a trend towards two peaks with increasing chronological and gestational age was observed in the longer tone pair. However, no such trend was evident in neonatal responses to the short tone pairs or in fetal recordings.

CONCLUSIONS

Neonates showed a gradual trend to successful processing of the longer tone pair with increasing age. By 22 days of chronological age, the infants processed this tone pair successfully, as indicated by two-peak waveforms. Therefore, the first 3 weeks of life could be critical for the development of RTP.

SIGNIFICANCE

This study is a first approach towards the assessment of early RTP development. The results provide promising indications for future studies, which might lead to an early detection of deficits in speech perception and therefore prevent further language impairments.

From acoustic segmentation to language processing: evidence from optical imaging

During language acquisition in infancy and when learning a foreign language, the segmentation of the auditory stream into words and phrases is a complex process. Intuitively, learners use “anchors” to segment the acoustic speech stream into meaningful units like words and phrases. Regularities on a segmental (e.g., phonological) or suprasegmental (e.g., prosodic) level can provide such anchors. Regarding the neuronal processing of these two kinds of linguistic cues a left-hemispheric dominance for segmental and a right-hemispheric bias for suprasegmental information has been reported in adults. Though lateralization is common in a number of higher cognitive functions, its prominence in language may also be a key to understanding the rapid emergence of the language network in infants and the ease at which we master our language in adulthood. One question here is whether the hemispheric lateralization is driven by linguistic input per se or whether non-linguistic, especially acoustic factors, “guide” the lateralization process. Methodologically, functional magnetic resonance imaging provides unsurpassed anatomical detail for such an enquiry. However, instrumental noise, experimental constraints and interference with EEG assessment limit its applicability, pointedly in infants and also when investigating the link between auditory and linguistic processing. Optical methods have the potential to fill this gap. Here we review a number of recent studies using optical imaging to investigate hemispheric differences during segmentation and basic auditory feature analysis in language development.

A locus for an auditory processing deficit and language impairment in an extended pedigree maps to 12p13.31-q14.3

Despite the apparent robustness of language learning in humans, a large number of children still fail to develop appropriate language skills despite adequate means and opportunity. Most cases of language impairment have a complex etiology, with genetic and environmental influences. In contrast, we describe a three-generation German family who present with an apparently simple segregation of language impairment. Investigations of the family indicate auditory processing difficulties as a core deficit. Affected members performed poorly on a nonword repetition task and present with communication impairments. The brain activation pattern for syllable duration as measured by event-related brain potentials showed clear differences between affected family members and controls, with only affected members displaying a late discrimination negativity. In conjunction with psychoacoustic data showing deficiencies in auditory duration discrimination, the present results indicate increased processing demands in discriminating syllables of different duration. This, we argue, forms the cognitive basis of the observed language impairment in this family. Genome-wide linkage analysis showed a haplotype in the central region of chromosome 12 which reaches the maximum possible logarithm of odds ratio (LOD) score and fully co-segregates with the language impairment, consistent with an autosomal dominant, fully penetrant mode of inheritance. Whole genome analysis yielded no novel inherited copy number variants strengthening the case for a simple inheritance pattern. Several genes in this region of chromosome 12 which are potentially implicated in language impairment did not contain polymorphisms likely to be the causative mutation, which is as yet unknown.

The contribution of processing impairments to SLI: insights from attention-deficit/hyperactivity disorder

Slowed speed of processing and impaired rapid temporal processing (RTP) have been proposed to underlie specific language impairment (SLI), but it is not clear that these dysfunctions are unique to SLI. We considered the contribution of attention-deficit/hyperactivity disorder (ADHD), which frequently co-occurs with language impairments, to performances on processing tasks. School-aged children who had SLI without concurrent ADHD (n=14), ADHD without concurrent SLI (n=14), and typical development (TD, n=28) performed two nonverbal speeded tasks and one auditory RTP task. RTP impairments were found in many children with SLI and ADHD, and some children with TD. Children with ADHD demonstrated slower processing speed than children with SLI or TD. Overall, findings questioned the uniqueness of these processing dysfunctions to language impairments and the validity of the behavioural paradigms traditionally used to estimate processing dysfunctions. Accounts of SLI should be further scrutinized by considering the influence of other disorders.

LEARNING OUTCOMES

Readers will (1) become familiar with areas of overlap between SLI and ADHD, (2) understand some of the confounds associated with behavioural measures of processing speed in children, and (3) recognize the value in testing models of language disorders by including participants with other types of disorders.

Fetal Magnetoencephalography - Achievements and Challenges in the Study of Prenatal and Early Postnatal Brain Responses: A Review

Fetal magnetoencephalography (fMEG) is the only non-invasive method for investigating evoked brain responses and spontaneous brain activity generated by the fetus in utero. Fetal auditory as well as visual evoked fields have been successfully recorded in basic stimulus-response studies. Moreover, paradigms investigating precursors for cognitive development, such as habituation and mismatch response have been applied successfully with fMEG. These and other studies have shown that the prenatal stage of life could be an important indicator for later cognitive development. This review addresses the achievements of fMEG and constructively discusses its challenges. It concludes with proposals for future studies as well as with designated new applications. Fetal MEG is a promising, and to date it is the only non-invasive approach for the prenatal assessment of precursors for cognitive development. Future fMEG studies might even enable the diagnosis of developmental delays. Furthermore, fMEG could be critical for the implementation and evaluation of fetal intervention programs in at-risk populations.

Testing auditory processing skills and their associations with language in 4-5-year-olds

Infants' auditory processing abilities have been shown to predict subsequent language development. In addition, poor auditory processing skills have been shown for some individuals with specific language impairment. Methods used in infant studies are not appropriate for use with young children, and neither are methods typically used to test auditory processing skills in specific language language impairment (SLI). The objective in this study was to develop an appropriate way of testing auditory processing skills in children in the 4-5 year age range. We report data from 49 children aged 4-5 years (mean age 58.57 months) tested on five tasks with tones and synthesized syllables. Frequencies and inter-stimulus intervals were varied in the tone tasks; the second formant transitions between consonant and vowel were varied in the syllable tasks. Consistent with past research, variability was found in children's auditory processing abilities. Significant correlations in discrimination thresholds for the tasks were found. The results from two regression analyses showed that the children's auditory processing abilities predicted significant amounts of variance for receptive and expressive language.

Subcortical differentiation of stop consonants relates to reading and speech-in-noise perception

Children with reading impairments have deficits in phonological awareness, phonemic categorization, speech-in-noise perception, and psychophysical tasks such as frequency and temporal discrimination. Many of these children also exhibit abnormal encoding of speech stimuli in the auditory brainstem, even though responses to click stimuli are normal. In typically developing children the auditory brainstem response reflects acoustic differences between contrastive stop consonants. The current study investigated whether this subcortical differentiation of stop consonants was related to reading ability and speech-in-noise performance. Across a group of children with a wide range of reading ability, the subcortical differentiation of 3 speech stimuli ([ba], [da], [ga]) was found to be correlated with phonological awareness, reading, and speech-in-noise perception, with better performers exhibiting greater differences among responses to the 3 syllables. When subjects were categorized into terciles based on phonological awareness and speech-in-noise performance, the top-performing third in each grouping had greater subcortical differentiation than the bottom third. These results are consistent with the view that the neural processes underlying phonological awareness and speech-in-noise perception depend on reciprocal interactions between cognitive and perceptual processes.

Comorbidity of auditory processing, language, and reading disorders

PURPOSE

The authors assessed comorbidity of auditory processing disorder (APD), language impairment (LI), and reading disorder (RD) in school-age children.

METHOD

Children (N = 68) with suspected APD and nonverbal IQ standard scores of 80 or more were assessed using auditory, language, reading, attention, and memory measures. Auditory processing tests included the Frequency Pattern Test (FPT; F. E. Musiek, 1994; D. Noffsinger, R. H. Wilson, & F. E. Musiek, 1994); the Dichotic Digit Test Version 2 (DDT; F. E. Musiek, 1983); the Random Gap Detection Test (R. W. Keith, 2000); the 500-Hz tone Masking Level Difference (V. Aithal, A. Yonovitz, & S. Aithal, 2006); and a monaural low-redundancy speech test (compressed and reverberant words; A. Boothroyd & S. Nittrouer, 1988). The Clinical Evaluation of Language Fundamentals, Fourth Edition (E. Semel, E. Wiig, & W. Secord, 2003) was used to assess language abilities (including auditory memory). Reading accuracy and fluency and phonological awareness abilities were assessed using the Wheldall Assessment of Reading Passages (A. Madelaine & K. Wheldall, 2002) and the Queensland University Inventory of Literacy (B. Dodd, A. Holm, M. Orelemans, & M. McCormick, 1996). Attention was measured using the Integrated Visual and Auditory Continuous Performance Test (J. A. Sandford & A. Turner, 1995).

RESULTS

Of the children, 72% had APD on the basis of these test results. Most of these children (25%) had difficulty with the FPT bilaterally. A further 22% had difficulty with the FPT bilaterally and had right ear deficits for the DDT. About half of the children (47%) had problems in all 3 areas (APD, LI, and RD); these children had the poorest FPT scores. More had APD-RD, or APD-LI, than APD, RD, or LI alone. There were modest correlations between FPT scores and attention and memory, and between DDT scores and memory.

CONCLUSIONS

LI and RD commonly co-occur with APD. Attention and memory are linked to performance on some auditory processing tasks but only explain a small amount of the variance in scores. Comprehensive assessment across a range of areas is required to characterize the difficulties experienced by children with APD.

Dynamic links between emerging cognitive skills and brain processes

The goal of the present study was to investigate whether advanced cognitive skills in one domain impact the neural processing of unrelated skills in a different cognitive domain. This question is related to the broader issue of how cognitive-neurodevelopment proceeds as different skills are mastered. To address this goal, event-related brain potentials (ERPs) were used to assess linkages between cognitive skills of preschool children as reflected in their performance on a pre-reading screening test (Get Ready To Read) and their neural responses while engaged in a geometric shape matching task. Sixteen children (10 males) participated in this study. The children ranged from 46 to 60 months (SD = 4.36 months). ERPs were recorded using a 128-electrode high-density array while children attended to presentations of matched and mismatched shapes (triangles, circles, or squares). ERPs indicated that children with more advanced pre-reading skills discriminated between matched and mismatched shapes earlier than children with poorer pre-readings skills. The earlier discrimination effect observed in the advanced group was localized over the occipital electrode sites whereas in the Low Group such effects were present over frontal, parietal, and occipital sites. Modeled magnetic resonance images (MRIs) of the ERP component sources identified differences in neural generators between the two groups. Both sets of findings support the hypothesis that processing in a poorer-performing group is more distributed temporally and spatially across the scalp, and reflects the engagement of more distributed brain regions. These findings are seen as support for a theory of neural-cognitive development that is advanced in the present article.

Stimulus, task, and learning effects on measures of temporal resolution: implications for predictors of language outcome

PURPOSE

Some studies find that temporal processing ability predicts language outcome whereas other studies do not. Resolution of this debate is hindered by the variety of temporal measures used, nonsensory loading of the tasks, and differential amounts of practice across studies. The goal of this study was to examine the effects of stimulus properties, experimental task, and perceptual learning on listeners' gap detection performance.

METHOD

Gap detection thresholds were obtained from adults with normal hearing and language ability. The effects of marker frequency similarity and marker duration on thresholds were examined in yes-no, two-interval forced-choice (2IFC), and dual-pair comparison tasks (which vary in nonsensory loading) over 4 days of testing.

RESULTS

Thresholds were highest for gaps defined by markers with disparate frequencies (1000 and 4000 Hz; i.e., between-channel gap detection), and with longer (300 ms) trailing markers, obtained using yes-no and 2IFC tasks. However, these effects were attenuated with training or the initial use of the dual-pair comparison task.

CONCLUSIONS

These results suggest that gap detection thresholds reflect a variety of sensory and nonsensory factors. Understanding these underlying factors is critical to any evaluation of the relation between temporal processing and language outcome.

Processing intensity at rapid rates: evidence from auditory evoked potentials in 9-11-year-old children

OBJECTIVE

The ability to understand speech requires processing of rapidly changing acoustic information. Much more is known about processing the rapid spectro-temporal properties of speech than is known about processing of intensity, even though intensity is a fundamental cue for accurate speech perception. The purpose for the current study was to characterize, in 9-11-year-old typically language-developing children, the auditory event-related brain potentials elicited by different tone intensities when presented in complex environments (i.e., varying in frequency and intensity) at rapid rates.

METHODS

Pure tones of four different intensity levels (66, 74, 78, and 86dB SPL) and five different stimulus frequencies were presented at a stimulus rate of 10Hz. The latency and amplitude of the auditory event-related brain potentials were measured.

RESULTS

At this fast rate, a positive (P1) followed by a negative component was elicited. The lowest intensity sound elicited the lowest P1 amplitude and the highest intensity sound elicited the highest P1 amplitude. The P1 elicited by the two middle tone intensities had amplitudes that fell between the lowest and highest amplitudes but they were not significantly different from each other. The negative component following the P1 was unaffected by intensity variation.

CONCLUSIONS

Intensity variation of sounds presented in a complex environment at a rapid rate modulated only the amplitude of the earliest obligatory auditory component (P1), consistent with our previous studies in which only the P1 could follow the rapid stimulation rate. P1 amplitude changes reflected the relative differences among the sounds, not the absolute differences in loudness among the sounds presented together in the sequence. The results suggest that the environment, or context, within which rapid sounds occur, influences the relative amplitude of the P1 in children.

Understanding language and cognitive deficits in very low birth weight children

Very-low-birth-weight infants are at much higher risk for cognitive and language delays but the nature of such deficits is not clearly understood. Given increasing rates of prematurity and infants born very-low-birth-weight, examination of mechanisms that underlie poorer developmental outcome is essential. We investigated language and cognitive abilities in very-low and normal birth-weight infants to determine whether performance differences were due to poorer global cognitive performance or to deficits in specific processing abilities. Thirty-two very-low and 32 normal birth-weight infants received visual and auditory-visual habituation recognition-memory tasks, and standardized language and cognitive assessments. Very-low-birth-weight infants performed more poorly on visual and auditory-visual habituation tasks and scored lower than controls on cognitive and language measures. These findings suggest that differences in language abilities in very-low-birth-weight children may be part of a global deficit that impacts many areas of cognitive functioning rather than a specific impairment in rapid auditory processing.

The maturation of human evoked brain potentials to sounds presented at different stimulus rates

The current study assessed the normal development of cortical auditory evoked potentials (CAEPs) in humans presented with pure tone stimuli at relatively fast stimulus rates. Traditionally, maturation of sound processing indexed by CAEPs has been studied in paradigms using inter-stimulus intervals (ISIs) generally slower than 1 Hz. While long ISIs may enhance the amplitude of CAEP components, speech information generally occurs at more rapid rates. These slower rates of sound presentation may not accurately assess auditory cortical functions in more realistic sound environments. We examined the effect of temporal rate on the elicitation of the P1-N1-P2-N2 components to unattended sounds at four levels of stimulus onset asynchrony (SOA, onset to onset, 200, 400, 600, and 800 ms) in children grouped separately by year (ages 8, 9, 10, 11 years), in adolescents (age 16 years) and in one group of young adults (ages 22-40 years). We found that both age and stimulus rate produced profound changes in CAEP morphology. Between the ages of 8-11 years, the P1 and N2 components dominated the ERP waveform at all stimulus rates. N1, the dominant CAEP component in adults, appeared as a bifurcation in a broad positive peak at earlier ages, and did not emerge as a separate component until adolescence. While the P1-N1-P2 components are more "adult-like" than "child-like" in the adolescent subjects, the N2 component, a hallmark of the child obligatory response, was still present. Faster rates resulted in the suppression of discrete components such that by 200 ms, only P1 in the adults and adolescents, and both P1 and N2 in the youngest children were discernable. We conclude that both age and ISI are important variables in the assessment of auditory cortex function and maturation. The presence of N2 in adolescents indicates that auditory cortical maturation persists into teen years.

Growth-related neural reorganization and the autism phenotype: a test of the hypothesis that altered brain growth leads to altered connectivity

Theoretical considerations, and findings from computational modeling, comparative neuroanatomy and developmental neuroscience, motivate the hypothesis that a deviant brain growth trajectory will lead to deviant patterns of change in cortico-cortical connectivity. Differences in brain size during development will alter the relative cost and effectiveness of short- and long-distance connections, and should thus impact the growth and retention of connections. Reduced brain size should favor long-distance connectivity; brain overgrowth should favor short-distance connectivity; and inconsistent deviations from the normal growth trajectory - as occurs in autism - should result in potentially disruptive changes to established patterns of functional and physical connectivity during development. To explore this hypothesis, neural networks which modeled inter-hemispheric interaction were grown at the rate of either typically developing children or children with autism. The influence of the length of the inter-hemispheric connections was analyzed at multiple developmental time-points. The networks that modeled autistic growth were less affected by removal of the inter-hemispheric connections than those that modeled normal growth - indicating a reduced reliance on long-distance connections - for short response times, and this difference increased substantially at approximately 24 simulated months of age. The performance of the networks showed a corresponding decline during development. And direct analysis of the connection weights showed a parallel reduction in connectivity. These modeling results support the hypothesis that the deviant growth trajectory in autism spectrum disorders may lead to a disruption of established patterns of functional connectivity during development, with potentially negative behavioral consequences, and a subsequent reduction in physical connectivity. The results are discussed in relation to the growing body of evidence of reduced functional and structural connectivity in autism, and in relation to the behavioral phenotype, particularly the developmental aspects.

Infant information processing and family history of specific language impairment: converging evidence for RAP deficits from two paradigms

An infant's ability to process auditory signals presented in rapid succession (i.e. rapid auditory processing abilities [RAP]) has been shown to predict differences in language outcomes in toddlers and preschool children. Early deficits in RAP abilities may serve as a behavioral marker for language-based learning disabilities. The purpose of this study is to determine if performance on infant information processing measures designed to tap RAP and global processing skills differ as a function of family history of specific language impairment (SLI) and/or the particular demand characteristics of the paradigm used. Seventeen 6- to 9-month-old infants from families with a history of specific language impairment (FH+) and 29 control infants (FH-) participated in this study. Infants' performance on two different RAP paradigms (head-turn procedure [HT] and auditory-visual habituation/recognition memory [AVH/RM]) and on a global processing task (visual habituation/recognition memory [VH/RM]) was assessed at 6 and 9 months. Toddler language and cognitive skills were evaluated at 12 and 16 months. A number of significant group differences were seen: FH+ infants showed significantly poorer discrimination of fast rate stimuli on both RAP tasks, took longer to habituate on both habituation/recognition memory measures, and had lower novelty preference scores on the visual habituation/recognition memory task. Infants' performance on the two RAP measures provided independent but converging contributions to outcome. Thus, different mechanisms appear to underlie performance on operantly conditioned tasks as compared to habituation/recognition memory paradigms. Further, infant RAP processing abilities predicted to 12- and 16-month language scores above and beyond family history of SLI. The results of this study provide additional support for the validity of infant RAP abilities as a behavioral marker for later language outcome. Finally, this is the first study to use a battery of infant tasks to demonstrate multi-modal processing deficits in infants at risk for SLI.

Fine grain temporal analysis in aphasia: Evidence from auditory gap detection

Auditory temporal processing was investigated in individuals with acquired aphasia using a task in which they were asked to detect brief silent gaps inserted between noise segments modeled after formants in speech. To examine within-channel gap detection, gaps of 10, 20, 40, and 80ms duration were inserted between an initial segment (IS) and a trailing segment (TS) centered at the same frequency (1kHz). In a between-channel gap detection condition, gaps of 20, 40, 80, and 100ms duration were inserted between an IS that differed in frequency (4kHz) from the TS (1kHz). The effect of gap onset timing was examined in both conditions by systematically varying the duration of the IS by 10, 20, or 40ms. A combined analysis revealed that for both conditions and all gap and IS durations, individuals with aphasia produced fewer correct responses than age-matched neurologically intact controls. Separate condition analyses revealed that when noise segments were centered at the same frequency, individuals with aphasia demonstrated poorer accuracy in detecting 40 and 80ms gaps relative to normal controls (p<0.001). When gaps were inserted between noise segments differing in frequency, on average, aphasic subjects performed less accurately at durations of 40, 80 and 100ms (p<0.025). Detection in both groups decreased with smaller IS durations. The difficulties with gap detection observed in the aphasic group suggest the existence of fundamental problems in processing the temporal form or microstructure of sounds characterized by rapidly changing onset dynamics.

Magnetoencephalography of the newborn brain

This paper reviews the use of event-related magnetic fields (ERFs) in infants; ERFs can be derived from magnetoencephalography by means of averaging. Basic perceptive skills are important prerequisites for the infant's later development. The automatic cortical processes related to processing auditory, somatosensory and visual stimuli can be addressed by using responses recorded directly from the brain. The traditional method, the event-related potential (ERP), has recently been accompanied by ERFs. Similarly to ERPs, higher processes related to short-term memory, stimulus comparisons, and attention allocation can also be studied with ERFs. Further, since addressing the neonatal higher cognitive and social capabilities is challenging using only behavioural means, ERFs provide information on these important functions at a very early stage immediately after birth or in some cases even before birth. The main advantage of ERFs, compared to ERPs, is detection of the signals with high accuracy both with respect to the noise level and estimation of the spatial location.

Early N400 development and later language acquisition

Recent developmental research on word processing has shown that mechanisms of lexical priming are already present in 12-month-olds whereas mechanisms of semantic integration indexed by the N400 mature a few months later. In a longitudinal setting we investigated whether the occurrence of an N400 at 19 months is associated with the children's language skills later on. To this end children were retrospectively grouped according to their verbal performance in a language test at 30 months. Children with later age-adequate expressive language skills already displayed an N400 at 19 months. In contrast, children with later poor expressive language skills who have an enhanced risk for the development of specific language impairment (SLI) did not show an early N400. The results imply that children who have deficits in their expressive language at the age of 30 months are already impaired in their semantic development about one year earlier.

Developmental timeframes for induction of microgyria and rapid auditory processing deficits in the rat

Induction of a focal freeze lesion to the skullcap of a 1-day-old rat pup leads to the formation of microgyria similar to those identified postmortem in human dyslexics. Rats with microgyria exhibit rapid auditory processing deficits similar to those seen in language-impaired (LI) children, and infants at risk for LI and these effects are particularly marked in juvenile as compared to adult subjects. In the current study, a startle response paradigm was used to investigate gap detection in juvenile and adult rats that received bilateral freezing lesions or sham surgery on postnatal day (P) 1, 3 or 5. Microgyria were confirmed in P1 and 3 lesion rats, but not in the P5 lesion group. We found a significant reduction in brain weight and neocortical volume in P1 and 3 lesioned brains relative to shams. Juvenile (P27-39) behavioral data indicated significant rapid auditory processing deficits in all three lesion groups as compared to sham subjects, while adult (P60+) data revealed a persistent disparity only between P1-lesioned rats and shams. Combined results suggest that generalized pathology affecting neocortical development is responsible for the presence of rapid auditory processing deficits, rather than factors specific to the formation of microgyria per se. Finally, results show that the window for the induction of rapid auditory processing deficits through disruption of neurodevelopment appears to extend beyond the endpoint for cortical neuronal migration, although, the persistent deficits exhibited by P1 lesion subjects suggest a secondary neurodevelopmental window at the time of cortical neuromigration representing a peak period of vulnerability.

Development of structure and function in the infant brain: implications for cognition, language and social behaviour

Recent advances in cognitive neuroscience have allowed us to begin investigating the development of both structure and function in the infant brain. However, despite the rapid evolution of technology, surprisingly few studies have examined the intersection between brain and behaviour over the first years of life. Even fewer have done so in the context of a particular research question. This paper aims to provide an overview of four domains that have been studied using techniques amenable to elucidating the brain/behaviour interface: language, face processing, object permanence, and joint attention, with particular emphasis on studies focusing on early development. The importance of the unique role of development and the interplay between structure and function is stressed throughout. It is hoped that this review will serve as a catalyst for further thinking about the substantial gaps in our understanding of the relationship between brain and behaviour across development. Further, our aim is to provide ideas about candidate brain areas that are likely to be implicated in particular behaviours or cognitive domains.

Infants' early ability to segment the conversational speech signal predicts later language development: A retrospective analysis

Two studies examined relationships between infants' early speech processing performance and later language and cognitive outcomes. Study 1 found that performance on speech segmentation tasks before 12 months of age related to expressive vocabulary at 24 months. However, performance on other tasks was not related to 2-year vocabulary. Study 2 assessed linguistic and cognitive skills at 4-6 years of age for children who had participated in segmentation studies as infants. Children who had been able to segment words from fluent speech scored higher on language measures, but not general IQ, as preschoolers. Results suggest that speech segmentation ability is an important prerequisite for successful language development, and they offer potential for developing measures to detect language impairment at an earlier age.

Similarities in the phenotype of the auditory neural substrate in children with Asperger syndrome and their parents

Asperger syndrome (AS) is a developmental disorder of brain function characterized by deficits in social interaction including difficulties in understanding emotional expressions. Children with AS share some of the behavioural characteristics with their parents and AS seems to run particularly in the male members of the same families. The aim of the present study was to determine whether similarities could be found between children with AS and their parents at central auditory processing. It was found that in children with AS the sound encoding, as reflected by the exogenous components of event-related potentials, was similarly abnormal as in both their mothers and fathers. However, their abnormal cortical auditory discrimination, as indexed by the prolonged latency of the mismatch negativity, resembled that of their fathers but not that of their mothers. The present results suggest that complex genetic mechanisms may contribute to auditory abnormalities encountered in children with AS.

Reduced stress pattern discrimination in 5-month-olds as a marker of risk for later language impairment: Neurophysiologial evidence

The study at hand investigates prosodic abilities of infants as early predictors of Specific Language Impairment (SLI), which is commonly diagnosed at a later age. The study is based on the hypothesis that the prosodic abilities of infants at risk for SLI are less elaborated than those of controls due to less efficient processing of the relevant acoustic cues. One of the most critical prosodic cues for word segmentation is stress pattern. In German as well as in English, the most frequent stress pattern of bisyllabics is the trochee, in which stress is placed on the first syllable. Using a passive oddball design, German 5-month-olds were examined with respect to their ability to discriminate different stress patterns of bisyllabics. Infants were grouped retrospectively based on their production performance at the ages of 12 and 24 months. In contrast to matched controls, infants with very low word production displayed event-related brain potentials with a significantly reduced amplitude of the discrimination response, i.e. a Mismatch Negativity (MMN), to the trochaic stress pattern. This amplitude difference indicates impaired prosodic processing of word stress during early development and may thus be taken as an early marker of risk for SLI.

The infant as a prelinguistic model for language learning impairments: predicting from event-related potentials to behavior

Associations between efficient processing of brief, rapidly presented, successive stimuli and language learning impairments (LLI) in older children and adults have been well documented. In this paper we examine the role that impaired rapid auditory processing (RAP) might play during early language acquisition. Using behavioral measures we have demonstrated that RAP abilities in infancy are critically linked to later language abilities for both non-speech and speech stimuli. Variance in infant RAP thresholds reliably predict language outcome at 3 years-of-age for infants at risk for LLI and control infants. We present data here describing patterns of electrocortical (EEG/ERP) activation at 6 month-of-age to the same non-verbal stimuli used in our behavioral studies. Well-defined differences were seen between infants from families with a history of LLI (FH+) and FH- controls in the amplitude of the mismatch response (MMR) as well as the latency of the N250 component in the 70 ms ISI condition only. Smaller mismatch responses and delayed onsets of the N250 component were seen in the FH+ group. The latency differences in the N250 component, but not the MMR amplitude variation, were significantly related to 24-month language outcome. Such converging tasks provide the opportunity to examine early precursors of LLI and allow the opportunity for earlier identification and intervention.

Timing errors in auditory event-related potentials

Electronic problems of electroencephalographic (EEG) system may occur in even the best-managed laboratories. Timing error may happen in the coupling of computers from various manufactures, resulting in the misalignment of event markers that signal the onset of stimuli. In one system, an impedance check desynchronized a computer and thus caused misalignment of events in EEG signals. Thus, the aim of this study was to develop a method to identify and correct such timing errors that contaminated 114 raw data of EEG/auditory event-related potentials (ERPs) recorded in one of our longitudinal studies. A two-step procedure was introduced in the correction of timing errors. First, the time delay was roughly estimated by identifying a P150 component in two ERP blocks. Second, a small phase-locked positive wave was identified for fine estimation. Reliability within and among evaluators was examined using ERP data with simulated timing errors. Concordant results were obtained in 104 (91.2%) of the 114 raw EEG/ERP data sets. Our results showed that the method presented here is reliable and can be used for correcting timing errors without introduction of experimenter bias.