Maritza Rivera-Gaxiola

Bilingual language learning: An ERP study relating early brain responses to speech, language input, and later word production

Research on the development of speech processing in bilingual children has typically implemented a cross-sectional design and relied on behavioral measures. The present study is the first to explore brain measures within a longitudinal study of this population. We report results from the first phase of data analysis in a longitudinal study exploring Spanish-English bilingual children and the relationships among (a) early brain measures of phonetic discrimination in both languages, (b) degree of exposure to each language in the home, and (c) children’s later bilingual word production abilities. Speech discrimination was assessed with event-related brain potentials (ERPs). A bilingual questionnaire was used to quantify the amount of language exposure from all adult speakers in the household, and subsequent word production was evaluated in both languages. Our results suggest that bilingual infants’ brain responses to speech differ from the pattern shown by monolingual infants. Bilingual infants did not show neural discrimination of either the Spanish or English contrast at 6–9 months. By 10–12 months of age, neural discrimination was observed for both contrasts. Bilingual infants showed continuous improvement in neural discrimination of the phonetic units from both languages with increasing age. Group differences in bilingual infants’ speech discrimination abilities are related to the amount of exposure to each of their native languages in the home. Finally, we show that infants’ later word production measures are significantly related to both their early neural discrimination skills and the amount exposure to the two languages early 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.

N400 during lexical decision tasks: a current source localization study

OBJECTIVE Our primary aim in the present study was to establish the anatomic and psychophysiological correlates of automatic and controlled semantic priming. METHODS Current sources were calculated on N400 component data from a previous study on lexical decision tasks [Clin Neurophysiol 1999;110:813] using the variable resolution electromagnetic tomography method (VARETA). In this study, two experiments were carried out, one using directly related pairs and the other one using mediated related pairs. Each experiment consisted of 3 tasks that required different levels of contribution from controlled processes. RESULTS Average source localization images showed the brain structures involved in lexical decision tasks. The automatic component of the N400 effect was related to activation of occipitotemporal and parahippocampal gyri and anterior temporal lobes bilaterally. The expectancy strategy was related to activation of the right posterior temporal and right frontal areas. The postlexical strategy was associated with activation of right frontal, anterior cingulate and bilateral superior parietal areas. CONCLUSIONS The findings indicated that the current sources of the N400 varied according to the relative contributions of automatic and controlled mechanisms. Moreover, the sources of the N400 effect depended on the type of strategy used.

Are poor readers semantically challenged? An event-related brain potential assessment

This study explores visual event-related potentials components in a group of poor readers (PRs) and control children who carried out figure and word categorization tasks. In both tasks, every child had to categorize between animal and non-animal stimuli in an odd-ball GO-GO paradigm. During the word categorization task, PRs presented longer reaction times, a poorer performance, longer and larger P2 amplitudes, and smaller amplitudes and longer P300 latencies than controls. There were no differences in the N400 component between groups. These results suggest that semantic processing underachievement in PRs may not be a semantic deficit per se, but the late reflection of an early word codification problem, deficient use of attentional resources and lack of target identification during reading.

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.

Event-related potentials to an english/spanish syllabic contrast in mexican 10-13-month-old infants.

We report brain electrophysiological responses from 10- to 13-month-old Mexican infants while listening to native and foreign CV-syllable contrasts differing in Voice Onset Time (VOT). All infants showed normal auditory event-related potential (ERP) components. Our analyses showed ERP evidence that Mexican infants are capable of discriminating their native sounds as well as the acoustically salient (aspiration) foreign contrast. The study showed that experience with native language influences VOT perception in Spanish learning infants. The acoustic salience of aspiration is perceived by both Spanish and English learning infants, but exposure provides additional phonetic status to this native-language feature for English learning infants. The effects of early experience and neural commitment as well as the impact of acoustic salience are further discussed.

Speech and non-speech processing in hemispherectomised children: an event-related potential study

Although hemispherectomy is now used as a radical treatment for intractable seizures in a number of centres, there have been limited electrophysiological studies investigating post-procedure auditory-speech processing and recovery or reorganisation. We therefore recorded auditory event-related potentials (ERPs) evoked by pure tones and syllables employing a 51-channel electrode array concentrated over the functional hemisphere in 17 patients (nine males, mean age 14.2 years) who had undergone hemispherectomy for intractable seizures; eight of the patients had congenital brain damage and nine had sustained their initial insult at an age of 1 year or older. For comparison, recordings were made from 10 controls (five males, mean age 13.5 years). Responses from patients consisted of five small amplitude components restricted to the functional hemisphere whose scalp polarity was opposite to the ERPs observed in control subjects. The topography of the auditory ERPs in the patients was localised to the centro-temporal regions of the functional hemisphere in comparison to the midline distribution observed in control subjects. As in the control subjects, the latencies of the components evoked by tones were shorter than those evoked by syllables in both left and right hemispherectomised children. In addition, further analysis of the N1 and P2 component revealed increased syllable latencies in left hemispherectomised children only. The results of this study suggest that the left hemisphere alone may be more efficient at processing both pure tones and syllables compared to the right or both together.

The bilingual brain: A comparison of native and non‐native speech perception in monolingual and bilingual infants

Infants raised in monolingual families are equally good at native and non‐native speech discrimination early in life. By 12 months, performance on native speech has significantly improved while non‐native performance declines. We tested bilingual American infants at 7 and 11 months of age on native (/ta‐pa/) and non‐native (Mandarin affricate‐fricative) contrasts used in the monolingual tests. Phonetic discrimination was assessed using behavioral (conditioned head‐turn) and brain (event‐related potential) measures. The MacArthur Communicative Development Inventory estimated infants developing language skills at 14, 18, 24, and 30 months of age. The monolingual data [Kuhl et al., Language Learning and Development (2005)] demonstrated that at 7 months of age, infants native and non‐native speech perception skills predicted their later language development, but differentially. Better native phonetic perception predicted more rapid language development between 14 and 30 months, whereas better non‐native phone...

Brain potentials in response to native and non‐native speech contrasts in 11‐month‐old American infants

Behavioral studies show that 6‐ to 8‐month‐old infants discriminate both native and non‐native phonetic differences, but that by 10–12 months of age, infants’ perceptual sensitivities decline to many non‐native contrasts. Kuhl et al. (1997) and Tsao et al. (2000) have also shown an enhancement in sensitivity to native contrasts, which was also shown by Cheour et al. (1998) using electrophysiological methods. Using both behavior and ERPs, Rivera‐Gaxiola et al. (2000) reported MMNs in native English speaking adults for a non‐native contrast that the same adults did not overtly discriminate. We here report auditory ERPs to native and non‐native VOT contrasts in 11‐month‐old monolingual American infants (N=16). Stimuli were presented as a double‐oddball paradigm. Continuous EEG was recorded using electrocaps. ERPs were obtained off‐line using standard methods. The results show that 11‐month‐olds display differential brain activity for native and non‐native contrasts. A clear, widely distributed phonetic MMN c...

Brain, behavioral, and sociocultural factors in bilingual language learning.

Previous behavioral studies have shown improved sensitivity to native‐language contrasts and reduced sensitivity to non‐native phonetic contrasts when comparing 6–8‐ and 10–12‐month‐old monolingual infants. It has been argued that exposure to language dedicates neural networks to the acoustic properties of native‐language speech, and that, in adulthood, this commitment interferes with nonnative speech processing [native language neural commitment or (NLNC)]. There are very few studies on how early speech perception in bilinguals relates to future language advancement. Recently it has been shown that infants’ early native‐language speech perception skill predicts their later success at language acquisition. In the present investigation, we examined how brain measures of speech perception in bilingual infants and socio‐cultural factors of their environment predict later vocabulary growth. Our results showed excellent neural discrimination of both English and Spanish phonetic contrasts in 12‐month‐old infant...