Evidence of deficient central speech processing in children with specific language impairment: The T-complex
These results suggest that poor auditory processing, as measured by the T-complex, is a marker for LI and that multiple deficits serve to mark LI.
The T-complex measures, indexing secondary auditory cortex, reflect an important aspect of processing in speech and language development.
Objective: There is interest in using cortical auditory evoked potentials (CAEPs) to evaluate hearing aid fittings and experience-related plasticity associated with amplification; however, little is known about hearing aid signal processing effects on these responses. The purpose of this study was to determine the effect of clinically relevant hearing aid gain settings, and the resulting in-the-canal signal-to-noise ratios (SNRs), on the latency and amplitude of P1, N1, and P2 waves. Design & Sample: Evoked potentials and in-the-canal acoustic measures were recorded in nine normal-hearing adults in unaided and aided conditions. In the aided condition, a 40-dB signal was delivered to a hearing aid programmed to provide four levels of gain (0, 10, 20, and 30 dB). As a control, unaided stimulus levels were matched to aided condition outputs (i.e. 40, 50, 60, and 70 dB) for comparison purposes. Results: When signal levels are defined in terms of output level, aided CAEPs were surprisingly smaller and delayed relative to unaided CAEPs, probably resulting from increases to noise levels caused by the hearing aid. Discussion: These results reinforce the notion that hearing aids modify stimulus characteristics such as SNR, which in turn affects the CAEP in a way that does not reliably reflect hearing aid gain.
from the International Journal of Audiology
Lexical prosody plays an important role in speech comprehension. However, the electrophysiological nature and time course of processing lexical prosody in mora-timed languages are rarely known in contrast to the wealth of knowledge in stress-timed languages and syllable-timed languages like German and French. In the present study, lexical pitch-accent processing in Japanese is investigated using event-related potentials. Participants listened to sentences with verbs either correct or incorrect with respect to pitch-accent (phonological condition), word meaning (semantic condition) or sentence type (syntactic condition). When the brain potentials of correct and incorrect sentences were compared within conditions, the phonological and semantic conditions showed a negativity and positivity (P600), while the syntactic condition displayed a P600. Furthermore, the negativity in response to pitch-accent violations (pitch-accent negativity) appeared approximately 60 ms earlier than the response to semantic violations (N400), while no significant topographical distributions were found between the two components. These results suggest that the pitch-accent negativity reflects initial phonological processing followed by lexical access and word recognition. Moreover, the P600 displayed in all conditions was interpreted as a general integration process that is common across the three domains.
from Brain Research
Effects of non-native language exposure on the semantic processing of native language in preschool children
We investigated the effects of non-native language (English) exposure on event-related potentials (ERPs) in first- and second-year (four- and five-year-old) preschool Japanese native speakers while they listened to semantically congruent and incongruent Japanese sentences. The children were divided into a non-native language exposed group (exposed group) and a group without such experiences (control group) on the basis of their exposure to non-native language. We compared the ERPs recorded from the two groups in each of the two preschool years. N400 was observed both in the first- and second-year preschoolers. Differences owing to exposure to non-native language appeared in the second-year preschoolers but not in the first-year preschoolers. In the second-year preschoolers, the N400 onset in the exposed group was shorter than that in the control group, but there was no difference in the N400 offset between the exposed and control groups. Furthermore, the scalp distribution of the N400 in the exposed group was broader than that in the control group. These results indicate that the time course and scalp distribution of semantic processing for native language sentences in young children fluctuated depending on exposure to non-native language.
Previous research into the cognitive processes involved in reading Chinese and developmental dyslexia in Chinese, revealed that the single most important factor appears to be orthographic processing skills rather than phonological skills. Also some studies have indicated that even in alphabetic languages some dyslexic individuals reveal deficits in orthographic processing skills, which are linked to a deficit in the visual magnocellular pathway. The current study therefore employed a visual psychophysical experiment together with visual and auditory event-related potential (ERP) experiments eliciting mismatch negativity (MMN) to investigate the link between visual magnocellular functional abnormalities and developmental dyslexia in Chinese. The performance levels of Chinese children with developmental dyslexia (DD) from the behavioural and electrophysiological experiments were compared to those of the chronological age-matched (CA) children and those of the reading level matched (RL) younger children. Both the behavioural and electrophysiological results suggest that the orthographic processing skills were compromised in the Chinese developmental dyslexics, which in turn is linked to a deficit in the visual magnocellular system.
A variant of the Reicher-Wheeler task was used to determine when in the event-related potential (ERP) waveform indices of word and pseudoword superiority effects might be present, and whether ERP measures of superiority effects correlated with standardized behavioral measures of orthographic fluency and single word reading. ERPs were recorded to briefly presented, masked letter strings that included real words (DARK/PARK), pseudowords (DARL/PARL), nonwords (RDKA/RPKA), and letter-in-xs (DXXX, PXXX) stimuli. Participants decided which of two letters occurred at a given position in the string (here, forced-choice alternatives D and P). Behaviorally, both word (more accurate choices for letters in words than in baseline nonwords or letter-in-xs) and pseudoword (more accurate choices for letters in pseudowords than in baseline conditions) superiority effects were observed. Electrophysiologically, effects of orthographic regularity and familiarity were apparent as early as the P150 time window (100-160 ms), an effect of lexicality was observed as early as the N200 time window (160-200 ms), and peak amplitude of the N300 and N400 also differentiated word and pseudoword as compared to baseline stimuli. Further, the size of the P150 and N400 ERP word superiority effects was related to standardized behavioral measures of fluency and reading. Results suggest that orthographic fluency is reflected in both lower-level, sublexical, perceptual processing and higher-level, lexical processing in fluently reading adults.
from Brain Research
Behavioral and electrophysiological measures of auditory change detection in children following late cochlear implantation: A preliminary study
There is evidence of utilization of usual auditory processing pathways in the AEPs of some children who receive cochlear implants late in their childhood. Some plasticity in the auditory cortical pathways may be present despite prolonged auditory deprivation in school-aged children who are late-implanted cochlear implant recipients.
The purpose of this study was to determine the effect of signal level and signal-to-noise ratio (SNR) on the latency and amplitude of evoked cortical activity to further our understanding of how the human central auditory system encodes signals in noise. Cortical auditory evoked potentials (CAEPs) were recorded from 15 young normal-hearing adults in response to a 1000 Hz tone presented at two tone levels in quiet and while continuous background noise levels were varied in five equivalent SNR steps. These 12 conditions were used to determine the effects of signal level and SNR level on CAEP components P1, N1, P2, and N2. Based on prior signal-in-noise experiments conducted in animals, we hypothesized that SNR, would be a key contributor to human CAEP characteristics. As hypothesized, amplitude increased and latency decreased with increasing SNR; in addition, there was no main effect of tone level across the two signal levels tested (60 and 75 dB SPL). Morphology of the P1-N1-P2 complex was driven primarily by SNR, highlighting the importance of noise when recording CAEPs. Results are discussed in terms of the current interest in recording CAEPs in hearing aid users.
from Hearing Research
ERP correlates of processing native and non-native language word stress in infants with different language outcomes
The early acquisition of native language prosody is assumed to ease infants’ language development. In a longitudinal setting we investigated whether the early processing of native and non-native language word stress patterns is associated with children’s subsequent language skills. ERP data of 71 four- and five-month-old infants were retrospectively grouped according to children’s verbal performance in a language test at 2.5 years. Children who displayed age-adequate expressive language skills later in development showed both an early and a late negative mismatch response (MMR) when processing the native language stress pattern as deviant in a passive oddball design. Children with poor language skills later in development did not show these negativities. Both groups displayed an infant-specific positive MMR to the non-native language deviant. This positivity was enhanced and prolonged in children who showed poor language skills later in development as compared to children who showed normal language skills. The results indicate that variability in expressive language development has precursors in infants’ ERP correlates of word stress processing.
Musical training facilitates detection of auditory patterns, allowing the ability to automatically recognize sequential sound patterns over longer time periods than non-musical counterparts.