Adrian Garcia-Sierra

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.

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.

Differences by Sex, Ear, and Sexual Orientation in the Time Intervals between Successive Peaks in Auditory Evoked Potentials

Auditory evoked potential (AEP) data from two studies originally designed for other purposes were reanalyzed. The auditory brainstem response (ABR), middle-latency response (MLR), and long-latency response (LLR) were measured. The latencies to each of several peaks were measured for each subject for each ear of click presentation, and the time intervals between successive peaks were calculated. Of interest were differences in interpeak intervals between the sexes, between people of differing sexual orientations, and between the two ears of stimulation. Most of the differences obtained were small. The largest sex differences were for interval I → V in the ABR and interval N1 → N2 of the LLR (effect sizes > 0.6). The largest differences between heterosexuals and nonheterosexuals were for the latency to Wave I in both sexes, for the interval Na → Nb in females, and for intervals V → Na and Nb → N1 in males (effect sizes > 0.3). The largest difference for ear stimulated was for interval N1 → N2 in heterosexual females (effect size ∼0.5). No substantial differences were found in the AEP intervals between women using, and not using, oral contraceptives. Left/right correlations for the interpeak intervals were mostly between about 0.4 and 0.6. Correlations between the ipsilateral intervals were small; i.e., interval length early in the AEP series was not highly predictive of interval length later in the series. Interpeak intervals appear generally less informative than raw latencies about differences by sex and by sexual orientation.

Relationships between quantity of language input and brain responses in bilingual and monolingual infants.

The present investigation explored the relation between the amount of language input and neural responses in English monolingual (N=18) and Spanish-English bilingual (N=19) infants. We examined the mismatch negativity (MMN); both the positive mismatch response (pMMR) and the negative mismatch response (nMMR), and identify a relationship between amount of language input and brain measures of speech discrimination for native and non-native speech sounds (i.e., Spanish, English and Chinese). Brain responses differed as a function of language input for native speech sounds in both monolinguals and bilinguals. Monolingual infants with high language input showed nMMRs to their native English contrast. Bilingual infants with high language input in Spanish and English showed pMMRs to both their native contrasts. The non-native speech contrast showed different patterns of brain activation for monolinguals and bilinguals regardless of amount of language input. Our results indicate that phonological representations of non-native speech sounds in bilingual infants are dependent on the phonetic similarities between their native languages.

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.

Relationships between otoacoustic emissions and a proxy measure of cochlear length derived from the auditory brainstem response.

Brief tones of 1.0 and 8.0 kHz were used to evoke auditory brainstem responses (ABRs), and the differences between the wave-V latencies for those two frequencies were used as a proxy for cochlear length. The tone bursts (8 ms in duration including 2-ms rise/fall times, and 82 dB in level) were, or were not, accompanied by a continuous, moderately intense noise band, highpass filtered immediately above the tone. The proxy values for length were compared with various measures of otoacoustic emissions (OAEs) obtained from the same ears. All the correlations were low, suggesting that cochlear length, as measured by this proxy at least, is not strongly related to the various group and individual differences that exist in OAEs. Female latencies did not differ across the menstrual cycle, and the proxy length measure exhibited no sex difference (either for menses females vs. males or midluteal females vs. males) when the highpass noises were used. However, when the subjects were partitioned into Whites and Non-Whites, a substantial sex difference in cochlear length did emerge for the White group, although the correlations with OAEs remained low. Head size was not highly correlated with any of the ABR measures.

Infant-directed speech in English and Spanish: Assessments of monolingual and bilingual caregiver VOT

Abstract It has been shown that monolingual caregivers exaggerate acoustic speech cues in infant-directed speech (IDS), but less is known about the characteristics of IDS in late second-language (L2) bilingual caregivers. Furthermore, there is inconsistency in the literature regarding voice onset time (VOT) of stop consonants in IDS. The present study explores VOT of English and Spanish stops in English monolingual and Spanish-dominant bilingual caregivers, in infant- versus adult-directed speech registers. Both monolinguals and bilinguals exaggerate VOT in IDS; however, different patterns are noted across consonant type and language context. Also, bilinguals produced English stops with Spanish-like and English-like properties, depending upon their L2-proficiency. The characteristics of late-L2 Spanish–English bilingual IDS may create a complex phonetic environment for infants, which may in turn affect the perception and later production of stop consonants in dual language-learning infants.

Look Who?s Talking NOW! Parentese Speech, Social Context, and Language Development Across Time

In previous studies, we found that the social interactions infants experience in their everyday lives at 11- and 14-months of age affect language ability at 24 months of age. These studies investigated relationships between the speech style (i.e., parentese speech vs. standard speech) and social context [i.e., one-on-one (1:1) vs. group] of language input in infancy and later speech development (i.e., at 24 months of age), controlling for socioeconomic status (SES). Results showed that the amount of exposure to parentese speech-1:1 in infancy was related to productive vocabulary at 24 months. The general goal of the present study was to investigate changes in (1) the pattern of social interactions between caregivers and their children from infancy to childhood and (2) relationships among speech style, social context, and language learning across time. Our study sample consisted of 30 participants from the previously published infant studies, evaluated at 33 months of age. Social interactions were assessed at home using digital first-person perspective recordings of the auditory environment. We found that caregivers use less parentese speech-1:1, and more standard speech-1:1, as their children get older. Furthermore, we found that the effects of parentese speech-1:1 in infancy on later language development at 24 months persist at 33 months of age. Finally, we found that exposure to standard speech-1:1 in childhood was the only social interaction that related to concurrent word production/use. Mediation analyses showed that standard speech-1:1 in childhood fully mediated the effects of parentese speech-1:1 in infancy on language development in childhood, controlling for SES. This study demonstrates that engaging in one-on-one interactions in infancy and later in life has important implications for language development.

Naturalistic social communication and speech development in monolingual and bilingual infants.

This investigation explores how everyday social communication between parents and infants relates to speech development. This goal is accomplished by using the digital recorder LENA that monolingual (N=11) and Spanish‐English bilingual (N=10) 14‐month‐old infants wore for 4 days. Infants’ sample files (i.e., 160, 30‐s intervals per infant) were coded according to the social communication coding inventory, which includes categories such as “babbling” (e.g., canonical versus variegated babbling), “social interactions” (e.g., baby was with one other person or with a group of people), “how adults are talking” (e.g., “motherese” versus adult talk), and “activities” (e.g., adult is reading and/or teaching). The results showed that babbling relates to relevant social communication categories in both groups. For example, the percentage of time “motherese” is used relates positively to babbling, but adult directed speech relates negatively to babbling. Interestingly, the amount of time monolingual parents spend te...