Brain-based individual difference measures of reading skill in deaf and hearing adults.

Most deaf children and adults struggle to read, but some deaf individuals do become highly proficient readers. There is disagreement about the specific causes of reading difficulty in the deaf population, and consequently, disagreement about the effectiveness of different strategies for teaching reading to deaf children. Much of the disagreement surrounds the question of whether deaf children read in similar or different ways as hearing children. In this study, we begin to answer this question by using real-time measures of neural language processing to assess if deaf and hearing adults read proficiently in similar or different ways. Hearing and deaf adults read English sentences with semantic, grammatical, and simultaneous semantic/grammatical errors while event-related potentials (ERPs) were recorded. The magnitude of individuals' ERP responses was compared to their standardized reading comprehension test scores, and potentially confounding variables like years of education, speechreading skill, and language background of deaf participants were controlled for. The best deaf readers had the largest N400 responses to semantic errors in sentences, while the best hearing readers had the largest P600 responses to grammatical errors in sentences. These results indicate that equally proficient hearing and deaf adults process written language in different ways, suggesting there is little reason to assume that literacy education should necessarily be the same for hearing and deaf children. The results also show that the most successful deaf readers focus on semantic information while reading, which suggests aspects of education that may promote improved literacy in the deaf population.

Principal component analyses and scalp distribution of the auditory P150-250 and N250-550 to speech contrasts in Mexican and American infants.

We report a Principal Component Analysis (PCA) and the scalp distribution of the normalized peak amplitude values for speech-related auditory Event-related Potentials (ERP) P150-250 and N250-550 in 7-, 11-, and 20-month-old American infants learning English and in 10-13-month-old Mexican infants learning Spanish. After assessing the infant auditory ERP P-N complex using PCA, we evaluated the topographic distribution of each of the discriminatory phases to native and non-native CV-syllabic contrasts used in Spanish and English. We found that the first two Principal Components for each contrast type across ages showing a maximization of differences between the P150-250 and the N250-550 waves, explain more than 70% of the variance. The scalp distributions of the P150-250 and N250-550 components also differed, the P150-250 showing a frontal and anterior temporal distribution, and the N250-550 a more posterior distribution. The older infants showed a broader distribution of responses, particularly for the N250-550. There were no differences in the topographies of the components between same-aged Mexican and American infants. We discuss the perceptual/linguistic functions that each component may reflect during development and across the two cultures.

Grammatical processing without semantics? An event-related brain potential study of preschoolers using jabberwocky sentences.

Behavioral studies have demonstrated that children develop a nearly adult-like grammar between 36 and 42 months, but few studies have addressed how the child's brain processes semantic versus syntactic information. In previous research, Silva-Pereyra and colleagues showed that distinct event-related potentials (ERPs) are elicited by semantic and syntactic violations in sentences in children as young as 30, 36, and 48 months, following the patterns displayed by adults. In the current study, we examined ERPs to syntactic phrase structure violations in real and jabberwocky sentences in 36-month-old children. Jabberwocky sentences are sentences in which content (open-class) words are replaced by pseudowords while function (closed-class) words are retained. Results showed that syntactically anomalous real sentences elicited two positive ERP effects: left-distributed effects from 500 to 750 msec and 1050 to 1300 msec, whereas syntactically anomalous jabberwocky sentences elicited two negative ERP effects: a left-distributed effect from 750 to 900 msec and a later broadly distributed effect from 950 to 1150 msec. The results indicate that when preschoolers process real English sentences, ERPs resembling the positive effects previously reported for adults are noted, although at longer latencies and with broader scalp distributions. However, when preschoolers process jabberwocky sentences with altered lexical-semantic content, a negative-going ERP component similar to one typically associated with the extraction of meaning is noted.

Sentence processing in 30-month-old children: an event-related potential study.

In a previous event-related brain potential study, we provided evidence that preschoolers display different brain electrical patterns to semantic content and syntactic structure processing. In the present study, we aimed to determine the time-course of these event-related potential effects in 30-month-old children, using the same syntactically anomalous, semantically anomalous and control sentences that we used in our previous study. The results show that semantic violations elicit a frontal negativity peaking around 600 ms, whereas the morphosyntactic violations elicit a slow positive shift peaking around 800 ms with a frontocentral distribution. Our findings replicate the event-related potential patterns previously observed in young children and indicate that the neural signatures of sentence processing can be observed at an early point in development.

Neural patterns to speech and vocabulary growth in American infants.

We report infant auditory event-related potentials to native and foreign contrasts. Foreign contrasts are discriminated at 11 months of age, showing significant differences between the standard and deviant over the positive (P150-250), or over the negative (N250-550) part of the waveform. The amplitudes of these deflections have different amplitude scalp distributions. Infants were followed up longitudinally at 18, 22, 25, 27 and 30 months for word production. The infant speech discriminatory P150-250 and N250-550 are different components with different implications for later language development.

Dynamics of Word Comprehension in Infancy: Developments in Timing, Accuracy, and Resistance to Acoustic Degradation.

Online comprehension of naturally spoken and perceptually degraded words was assessed in 95 children ages 12 to 31 months. The time course of word recognition was measured by monitoring eye movements as children looked at pictures while listening to familiar target words presented in unaltered, time-compressed, and low-pass-filtered forms. Success in word recognition varied with age and level of vocabulary development, and with the perceptual integrity of the word. Recognition was best overall for unaltered words, lower for time-compressed words, and significantly lower in low-pass-filtered words. Reaction times were fastest in compressed, followed by unaltered and filtered words. Results showed that children were able to recognize familiar words in challenging conditions and that productive vocabulary size was more sensitive than chronological age as a predictor of children's accuracy and speed in word recognition.