Arturo E. Hernandez

Language switching and language representation in Spanish-English bilinguals: An fMRI study

The current experiment was designed to investigate the nature of cognitive control in within- and between-language switching in bilingual participants. To examine the neural substrate of language switching we used functional magnetic resonance imaging (fMRI) as subjects named pictures in one language only or switched between languages. Participants were also asked to name (only in English) a separate set of pictures as either the actions or the objects depicted or to switch between these two types of responses on each subsequent picture. Picture naming compared to rest revealed activation in the dorsolateral prefrontal cortex, which extended down into Broca’s area in the left hemisphere. There were no differences in the activation pattern for each language. English and Spanish both activated overlapping areas of the brain. Similarly, there was no difference in activation for naming actions or objects in English. However, there was increased intensity of activation in the dorsolateral prefrontal cortex for switching between languages relative to no-switching, an effect which was not observed for naming of actions or objects in English. We suggest that the dorsolateral prefrontal cortex serves to attenuate interference that results from having to actively enhance and suppress two languages in alternation. These results are consistent with the view that switching between languages involves increased general executive processing. Finally, our results are consistent with the view that different languages are represented in overlapping areas of the brain in early bilinguals.

Age of Acquisition: Its Neural and Computational Mechanisms.

The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects.

Impact of language proficiency and orthographic transparency on bilingual word reading: An fMRI investigation

The purpose of the present functional magnetic resonance imaging (fMRI) investigation was to examine how language proficiency and orthographic transparency (letter-sound mapping consistency) modulate neural activity during bilingual single word reading. Spanish-English bilingual participants, more fluent in their second language (L2; English) than their native language (L1; Spanish), were asked to read words in the two languages. Behavioral results showed that participants were significantly slower in reading words in their less proficient language (Spanish) than in their more proficient language (English). fMRI results also revealed that reading words in the less proficient language yielded greater activity in the articulatory motor system, consisting of supplementary motor area/cingulate, insula, and putamen. Together, the behavioral and fMRI results suggest that the less practiced, hence less proficient, language requires greater articulatory motor effort, which results in slower reading rates. Moreover, we found that orthographic transparency also played a neuromodulatory role. More transparent Spanish words yielded greater activity in superior temporal gyrus (STG; BA 22), a region implicated in phonological processing, and orthographically opaque English words yielded greater activity in visual processing and word recoding regions, such as the occipito-parietal border and inferior parietal lobe (IPL; BA 40). Overall, our fMRI results suggest that the articulatory motor system is more plastic, hence, more amenable to change because of greater exposure to the L2. By contrast, we propose that our orthography effect is less plastic, hence, less influenced by frequency of exposure to a language system.

Distinct brain representations for early and late learned words.

Recently there has been a renewed interest in cognitive psychology on the effects of the age of word acquisition (AoA) on lexical processing. In particular, it is currently unclear whether AoA or word frequency are better predictors of word recognition. To date no study has investigated the neural bases of the AoA effect or attempted to dissociate it from word frequency. We report a visual and an auditory event-related fMRI experiment investigating the influence of AoA and word frequency on neural activity, and show that AoA modulates brain areas that are not influenced by word frequency. The precuneus was activated for early learned words across auditory and visual presentation modalities. Additional activity in the auditory cortex was observed specifically for the reading of early acquired words. Late learned words, in contrast, led to a selective activation increase in lateral inferior frontal areas. These findings support models that suggest that early and late learned words are represented differently in the brain. They further allow to specify the nature of the representational differences, namely that early learned words are represented in the brain in a more sensory manner than late learned words.

Processing across the language boundary: a cross-modal priming study of Spanish-English bilinguals

A cross-modal naming paradigm was used to assess within- and between-language sentential priming in Spanish-English bilinguals. The paradigm used single-language auditory texts with visual target words under normal, visually degraded, speeded, and delayed naming conditions. Cross-language priming was always observed when the target language was predictable (in the blocked condition), even under speeded conditions. When the target language was unpredictable (in the mixed condition), cross-language priming was observed only when response was delayed (delayed naming) and under a subset of conditions when word recognition was delayed (visual degradation). Results are compatible with the idea that cross-language priming in a sentence context is more likely to involve the use of expectations, strategic processes, or both that allow bilinguals to tune themselves to external conditions. There are enough exceptions to the general rule, however, to warrant a reconsideration of the lexical-postlexical dichotomy. Implication for modular versus interactive models of lexical access are discussed.

Is Native-Language Decoding Skill Related to Second-Language Learning?.

The authors investigated the mechanisms through which native-language word decoding ability predicted individual differences in nativeand second-language learning. First, native-language decoding skill predicted college-age adults’ native-language competency. However, this direct relationship was mediated by native-language vocabulary skill. Second, native-language decoding skill also predicted secondlanguage competency. Furthermore, this relationship was mediated by participants’ second-language word decoding ability. Third, native-language decoding was also an important predictor of course grade in the 1st quarter of Introductory Spanish. These results are consistent with the hypothesis that second-language learning is founded on native-language phonological–orthographic ability among college-age adults, especially during the early stages of second-language learning.

Age of acquisition modulates neural activity for both regular and irregular syntactic functions.

Studies have found that neural activity is greater for irregular grammatical items than regular items. Findings with monolingual Spanish speakers have revealed a similar effect when making gender decisions for visually presented nouns. The current study extended previous studies by looking at the role of regularity in modulating differences in groups that differ in the age of acquisition of a language. Early and late learners of Spanish matched on measures of language proficiency were asked to make gender decisions to regular (-o for masculine and -a for feminine) and irregular items (which can end in e, l, n, r, s, t and z). Results revealed increased activity in left BA 44 for irregular compared to regular items in separate comparisons for both early and late learners. In addition, within-group comparisons revealed that neural activity for irregulars extended into left BA 47 for late learners and into left BA 6 for early learners. Direct comparisons between groups revealed increased activity in left BA 44/45 for irregular items indicating the need for more extensive syntactic processing in late learners. The results revealed that processing of irregular grammatical gender leads to increased activity in left BA 44 and adjacent areas in the left IFG regardless of when a language is learned. Furthermore, these findings suggest differential recruitment of brain areas associated with grammatical processing in late learners. The results are discussed with regard to a model which considers L2 learning as emerging from the competitive interplay between two languages.

Executive function is necessary to enhance lexical processing in a less proficient L2: Evidence from fMRI during picture naming

Recent work in the bilingual literature suggests that naming pictures in a second language (L2) differs from naming pictures in the first language (L1) because of effortful lexical retrieval. This finding has received some support in the neuroimaging literature (De Blesser et al., 2003). In the current study, twelve Spanish-English bilinguals, who had learned English later in early adulthood, were asked to name pictures covertly in either Spanish or English while being scanned with functional Magnetic Resonance Imaging (fMRI). Picture naming in the second language (L2) relative to the native language (L1) revealed increased activity in the right insula, anterior cingulate gyrus and dorsolateral prefrontal cortex (DLPFC) and the left fusiform gyrus. These results are consistent with the view that picture naming in a less proficient L2 requires increased effort to establish links between motor codes and visual forms.

Within- and Between-Language Priming Differ: Evidence from Repetition of Pictures in Spanish-English Bilinguals

In the current study, the authors used an immediate repetition paradigm with pictures to observe whether repetition enhances word production in bilinguals. In Experiment 1, participants were asked to name pictures that were named previously in the same language (Spanish-Spanish or English-English) or in the opposite language (Spanish-English or English-Spanish). Results revealed a repetition effect both within languages and between languages. Furthermore, there was an asymmetry within language, with repetition priming being larger in Spanish than in English. Experiments 2 and 3 revealed that lag interacted with language for both within- and between-language priming. However, lag resulted in a decrease in the asymmetry for within- but not between-language priming. The results are consistent with the view that within- and between-language repetition priming are mediated by different mechanisms.

The brain bases of reading late learned words: Evidence from functional MRI

Age of acquisition (AoA) effects for reading have been documented in the literature. Recent studies have suggested that more effortful phonological retrieval is involved in picture naming for late learned words. Here we use functional magnetic resonance imaging to determine the neuroanatomical correlates of AoA effects in reading, and to explore whether AoA effects in the brain modulate activity in areas devoted to phonological processing. Participants were asked to covertly name blocks of early and late learned words while being scanned with functional MRI. Results revealed a relative increase in neural activity for late learned words in a set of brain areas involved in auditory-phonological processing (the planum temporale of the posterior-superior left temporal lobe) and articulatory motor planning (BA 44, putamen, and globus pallidus). These findings support the view that late learned words involve more effortful phonological retrieval, but in addition point to a second locus of the AoA effect in the articulatory component of the reading system.