Maya Misra

Language selection in bilingual speech : Evidence for inhibitory processes

Although bilinguals rarely make random errors of language when they speak, research on spoken production provides compelling evidence to suggest that both languages are active when only one language is spoken (e.g., [Poulisse, N. (1999). Slips of the tongue: Speech errors in first and second language production. Amsterdam/Philadelphia: John Benjamins]). Moreover, the parallel activation of the two languages appears to characterize the planning of speech for highly proficient bilinguals as well as second language learners. In this paper, we first review the evidence for cross-language activity during single word production and then consider the two major alternative models of how the intended language is eventually selected. According to language-specific selection models, both languages may be active but bilinguals develop the ability to selectively attend to candidates in the intended language. The alternative model, that candidates from both languages compete for selection, requires that cross-language activity be modulated to allow selection to occur. On the latter view, the selection mechanism may require that candidates in the nontarget language be inhibited. We consider the evidence for such an inhibitory mechanism in a series of recent behavioral and neuroimaging studies.

Local and global inhibition in bilingual word production: fMRI evidence from Chinese-English bilinguals

The current study examined the neural correlates associated with local and global inhibitory processes used by bilinguals to resolve interference between competing responses. Two groups of participants completed both blocked and mixed picture naming tasks while undergoing functional magnetic resonance imaging (fMRI). One group first named a set of pictures in L1, and then named the same pictures in L2. The other group first named pictures in L2, and then in L1. After the blocked naming tasks, both groups performed a mixed language naming task (i.e., naming pictures in either language according to a cue). The comparison between the blocked and mixed naming tasks, collapsed across groups, was defined as the local switching effect, while the comparison between blocked naming in each language was defined as the global switching effect. Distinct patterns of neural activation were found for local inhibition as compared to global inhibition in bilingual word production. Specifically, the results suggest that the dorsal anterior cingulate cortex (ACC) and the supplementary motor area (SMA) play important roles in local inhibition, while the dorsal left frontal gyrus and parietal cortex are important for global inhibition.

When bilinguals choose a single word to speak: Electrophysiological evidence for inhibition of the native language

Behavioral and event-related potential (ERP) measures are reported for a study in which relatively proficient Chinese-English bilinguals named identical pictures in each of their two languages. Production occurred only in Chinese (the first language, L1) or only in English (the second language, L2) in a given block with the order counterbalanced across participants. The repetition of pictures across blocks was expected to produce facilitation in the form of faster responses and more positive ERPs. However, we hypothesized that if both languages are activated when naming one language alone, there might be evidence of inhibition of the stronger L1 to enable naming in the weaker L2. Behavioral data revealed the dominance of Chinese relative to English, with overall faster and more accurate naming performance in L1 than L2. However, reaction times for naming in L1 after naming in L2 showed no repetition advantage and the ERP data showed greater negativity when pictures were named in L1 following L2. This greater negativity for repeated items suggests the presence of inhibition rather than facilitation alone. Critically, the asymmetric negativity associated with the L1 when it followed the L2 endured beyond the immediate switch of language, implying long-lasting inhibition of the L1. In contrast, when L2 naming followed L1, both behavioral and ERP evidence produced a facilitatory pattern, consistent with repetition priming. Taken together, the results support a model of bilingual lexical production in which candidates in both languages compete for selection, with inhibition of the more dominant L1 when planning speech in the less dominant L2. We discuss the implications for modeling the scope and time course of inhibitory processes.

Event–related potential indices of masked repetition priming

Two experiments sought to identify event-related potential (ERP) correlates of masked repetition priming of words in lists and to verify that such effects are not due to brief prime durations. In Experiment 1, prime stimuli were masked and their durations were individually titrated for each participant. Targets that were immediate or delayed repetitions of masked primes resulted in attenuation of the N400, with little or no enhancement of a late positive component (LPC). Delayed, in-the-clear repetitions of unmasked targets led to attenuation of the N400 and enhancement of the LPC. Experiment 2 used similar stimulus timing parameters, but primes were unmasked. More typical unmasked repetition effects were observed for immediate repetitions including a larger attenuation of the N400 and enhancement of the LPC. These findings are discussed within current notions of the functional significance of the N400 and LPC.

Neural Systems for Rapid Automatized Naming in Skilled Readers: Unraveling the RAN-Reading Relationship

The majority of children and adults with reading disabilities exhibit pronounced difficulties on naming-speed measures such as tests of rapid automatized naming (RAN). RAN tasks require speeded naming of serially presented stimuli and share key characteristics with reading, but different versions of the RAN task vary in their sensitivity: The RAN letters task successfully predicts reading ability, whereas the RAN objects task does not reliably predict reading after kindergarten. In this study we used functional magnetic resonance imaging to evaluate the neural substrates that may underlie performance on these tasks. In two scans during the same test session, adult, average readers covertly rapidly named objects or letters or passively viewed a fixation matrix of plus signs. For both rapid naming tasks compared with fixation, activation was found in neural areas associated with eye movement control and attention as well as in a network of structures previously implicated in reading tasks. This reading network included inferior frontal cortex, temporo-parietal areas, and the ventral visual stream. Whereas the inferior frontal areas of the network were similarly activated for both letters and objects, activation in the posterior areas varied by task. The letters task caused greater activation in the angular gyrus, superior parietal lobule, and medial extrastriate areas, whereas object naming only preferentially activated an area of the fusiform gyrus. These results confirm that RAN tasks recruit a network of neural structures also involved in more complex reading tasks and suggest that the RAN letters task specifically pinpoints key components of this network.

Imaging phonology without print: Assessing the neural correlates of phonemic awareness using fMRI

Acquisition of phonological processing skills, such as the ability to segment words into corresponding speech sounds, is critical to the development of efficient reading. Prior neuroimaging studies of phonological processing have often relied on auditory stimuli or print-mediated tasks that may be problematic for various theoretical and empirical reasons. For the current study, we developed a task to evaluate phonological processing that used visual stimuli but did not require interpretation of orthographic forms. This task requires the subject to retrieve the names of objects and to compare their first sounds; then, the subject must indicate if the initial sounds of the names of the pictures are the same. The phonological analysis task was compared to both a baseline matching task and a more complex control condition in which the participants evaluated two different pictures and indicated whether they represented the same object. The complex picture-matching condition controls for the visual complexity of the stimuli but does not require phonological analysis of the names of the objects. While both frontal and ventral posterior areas were activated in response to phonological analysis of the names of pictures, only inferior and superior frontal gyrus exhibited differential sensitivity to the phonological comparison task as compared to the complex picture-matching control task. These findings suggest that phonological processing that is not mediated by print relies primarily on frontal language processing areas among skilled readers.

On the time course of accessing meaning in a second language: an electrophysiological and behavioral investigation of translation recognition.

In 2 experiments, relatively proficient Chinese-English bilinguals decided whether Chinese words were the correct translations of English words. Critical trials were those on which incorrect translations were related in lexical form or meaning to the correct translation. In Experiment 1, behavioral interference was revealed for both distractor types, but event-related potentials (ERPs) revealed a different time course for the 2 conditions. Semantic distractors elicited effects primarily on the N400 and late positive component (LPC), with a smaller N400 and a smaller LPC over the posterior scalp but a larger LPC over the anterior scalp relative to unrelated controls. In contrast, translation form distractors elicited a larger P200 and a larger LPC than did unrelated controls. To determine whether the translation form effects were enabled by the relatively long, 750-ms stimulus onset asynchrony (SOA) between words, a 2nd ERP experiment was conducted using a shorter, 300-ms, SOA. The behavioral results revealed interference for both types of distractors, but the ERPs again revealed different loci for the 2 effects. Taken together, the data suggest that proficient bilinguals activate 1st-language translations of words in the 2nd language after they have accessed the meaning of those words. The implications of this pattern for claims about the nature of cross-language activation when bilinguals read in 1 or both languages are discussed.

Effects of children's working memory capacity and processing speed on their sentence imitation performance

BACKGROUND More limited working memory capacity and slower processing for language and cognitive tasks are characteristics of many children with language difficulties. Individual differences in processing speed have not consistently been found to predict language ability or severity of language impairment. There are conflicting views on whether working memory and processing speed are integrated or separable abilities. AIMS To evaluate four models for the relations of individual differences in childrens processing speed and working memory capacity in sentence imitation. The models considered whether working memory and processing speed are integrated or separable, as well as the effect of the number of operations required per sentence. The role of working memory as a mediator of the effect of processing speed on sentence imitation was also evaluated. METHODS & PROCEDURES Forty-six children with varied language and reading abilities imitated sentences. Working memory was measured with the Competing Language Processing Task (CLPT), and processing speed was measured with a composite of truth-value judgment and rapid automatized naming tasks. Mixed-effects ordinal regression models evaluated the CLPT and processing speed as predictors of sentence imitation item scores. A single mediator model evaluated working memory as a mediator of the effect of processing speed on sentence imitation total scores. OUTCOMES & RESULTS Working memory was a reliable predictor of sentence imitation accuracy, but processing speed predicted sentence imitation only as a component of a processing speed by number of operations interaction. Processing speed predicted working memory capacity, and there was evidence that working memory acted as a mediator of the effect of processing speed on sentence imitation accuracy. CONCLUSIONS & IMPLICATIONS The findings support a refined view of working memory and processing speed as separable factors in childrens sentence imitation performance. Processing speed does not independently explain sentence imitation accuracy for all sentence types, but contributes when the task requires more mental operations. Processing speed also has an indirect effect on sentence imitation by contributing to working memory capacity.

An event-related potential study of visual rhyming effects in native and non-native English speakers.

English monolinguals and highly proficient, but first language (L1)-dominant, Spanish–English and Chinese–English bilinguals made rhyme judgments of visually presented English word pairs while behavioral and EEG measures were being recorded. Two types of conditions were considered: rhyming and nonrhyming pairs that were orthographically dissimilar (e.g. white–fight, child–cough) and those that were orthographically similar (e.g. right–fight, dough–cough). Both native and non-native English speakers were faster and more accurate in responding to nonrhyming than rhyming targets under orthographically dissimilar conditions, although the response times of Chinese–English bilinguals differed from those of the other groups. All groups were slower and less accurate in responding to nonrhyming targets under orthographically similar conditions, with the response times and accuracy rates of Spanish–English bilinguals differing from those of the other groups. All participant groups showed more negative N450 mean amplitudes to nonrhyming compared with rhyming targets, regardless of orthographic similarity, and this rhyming effect did not differ across groups under the orthographically similar conditions. However, under orthographically dissimilar conditions, the rhyming effect was less robust in non-native speakers, being modulated by English proficiency.