A longitudinal investigation of structural brain changes during second language learning.

Few studies have examined the time course of second language (L2) induced neuroplasticity or how individual differences may be associated with brain changes. The current longitudinal structural magnetic resonance imaging study examined changes in cortical thickness (CT) and gray matter volume (GMV) across two semesters of L2 Spanish classroom learning. Learners' lexical processing was assessed via a language decision task containing English and Spanish words. Our findings indicated that (1) CT increased in the left anterior cingulate cortex (ACC) and right middle temporal gyrus (MTG) after L2 learning, (2) CT in the right MTG increased in individuals who were better able to discriminate between native language and L2 words, and (3) CT in the left ACC was correlated with functional connectivity between the ACC and MTG. These findings indicate that L2 lexical development is associated with functional and structural changes in brain regions important for cognitive control and semantic processing.

Structural brain changes as a function of second language vocabulary training: Effects of learning context.

Recent research indicates that learning a second language (L2) results in both functional and structural brain changes. However, few studies have examined whether structural brain changes vary as a function of the context in which L2 learning takes place. The current study examines changes in cortical thickness (CT) and gray matter volume (GMV) in response to short-term L2 vocabulary learning. In particular, we compared structural changes for learning with paired picture-word (PW) association versus learning within virtual environments (VE) and non-trained controls. Both L2 training groups learned the same 90 Mandarin Chinese nouns across 7 training sessions over approximately 20 days. Our results show (a) CT and GMV increased in regions implicated in a language control network for both L2 training groups, and (b) participants in different learning contexts may rely on different structures within this language control network. In particular, CT in the right IFG was associated with L2 training performance for the PW group, whereas CT in the right IPL showed a positive correlation with L2 training performance for the VE group. Our findings indicate that short-term L2 training leads to changes in brain structure, which vary based on L2 learning contexts and individual differences in cognitive ability.

Cross-modal working memory binding and L1-L2 word learning.

The ability to create temporary binding representations of information from different sources in working memory has recently been found to relate to the development of monolingual word recognition in children. The current study explored this possible relationship in an adult word-learning context. We assessed whether the relationship between cross-modal working memory binding and lexical development would be observed in the learning of associations between unfamiliar spoken words and their semantic referents, and whether it would vary across experimental conditions in first- and second-language word learning. A group of English monolinguals were recruited to learn 24 spoken disyllable Mandarin Chinese words in association with either familiar or novel objects as semantic referents. They also took a working memory task in which their ability to temporarily bind auditory-verbal and visual information was measured. Participants' performance on this task was uniquely linked to their learning and retention of words for both novel objects and for familiar objects. This suggests that, at least for spoken language, cross-modal working memory binding might play a similar role in second language-like (i.e., learning new words for familiar objects) and in more native-like situations (i.e., learning new words for novel objects). Our findings provide new evidence for the role of cross-modal working memory binding in L1 word learning and further indicate that early stages of picture-based word learning in L2 might rely on similar cognitive processes as in L1.

Bilingual Object Naming: A Connectionist Model.

Patterns of object naming often differ between languages, but bilingual speakers develop convergent naming patterns in their two languages that are distinct from those of monolingual speakers of each language. This convergence appears to reflect interactions between lexical representations for the two languages. In this study, we developed a self-organizing connectionist model to simulate semantic convergence in the bilingual lexicon and investigate the mechanisms underlying this semantic convergence. We examined the similarity of patterns in the simulated data to empirical data from past research, and we identified how semantic convergence was manifested in the simulated bilingual lexical knowledge. Furthermore, we created impaired models in which components of the network were removed so as to examine the importance of the relevant components on bilingual object naming. Our results demonstrate that connections between two languages' lexicons can be established through the simultaneous activations of related words in the two languages. These connections between languages allow the outputs of their lexicons to become more similar, that is, to converge. Our model provides a basis for future computational studies of how various input variables may affect bilingual naming patterns.

Second language lexical development and cognitive control: A longitudinal fMRI study.

In this paper we report a longitudinal functional magnetic resonance imaging (fMRI) study that tested contrasting predictions about the time course of cognitive control in second language (L2) acquisition. We examined the neural correlates of lexical processing in L2 learners twice over the course of one academic year. Specifically, while in the scanner, participants were asked to judge the language membership of unambiguous first and second language words, as well as interlingual homographs. Our ROI and connectivity analyses reveal that with increased exposure to the L2, overall activation in control areas such as the anterior cingulate cortex decrease while connectivity with semantic processing regions such as the middle temporal gyrus increase. These results suggest that cognitive control is more important initially in L2 acquisition, and have significant implications for understanding developmental and neurocognitive models of second language lexical processing.

Attentional but not pre-attentive neural measures of auditory discrimination are atypical in children with developmental language disorder.

We examined neural indices of pre-attentive phonological and attentional auditory discrimination in children with developmental language disorder (DLD, n = 23) and typically developing (n = 16) peers from a geographically isolated Russian-speaking population with an elevated prevalence of DLD. Pre-attentive phonological MMN components were robust and did not differ in two groups. Children with DLD showed attenuated P3 and atypically distributed P2 components in the attentional auditory discrimination task; P2 and P3 amplitudes were linked to working memory capacity, development of complex syntax, and vocabulary. The results corroborate findings of reduced processing capacity in DLD and support a multifactorial view of the disorder.

Neural division of labor in reading is constrained by culture: a training study of reading Chinese characters.

Word reading in alphabetic language involves a cortical system with multiple components whose division of labor depends on the transparency of the writing system. To gain insight about the neural division of labor between phonology and semantics subserving word reading in Chinese, a deep non-alphabetic writing system, functional magnetic resonance imaging (fMRI) was used to investigate the effects of phonological and semantic training on the cortical circuitry for oral naming of Chinese characters. In a training study, we examined whether a training task that differentially focused readers' attention on the phonological or semantic properties of a Chinese character changes the patterns of cortical activation that was evoked by that character in a subsequent naming task. Our imaging results corroborate that the cortical regions underlying reading in Chinese largely overlap the left-hemisphere reading system responsible for reading in alphabetic languages, with some cortical regions in the left-hemisphere uniquely recruited for reading in Chinese. However, in contrast to findings from studies of English word naming, we observed considerable overlap in the neural activation patterns associated with phonological and semantic training on naming Chinese characters, which we suggest may reflect a balanced neural division of labor between phonology and semantics in Chinese character reading. The equitable division of labor for Chinese reading might be driven by the special statistical structure of the writing system, which includes equally systematic mappings in the correspondences between written forms and their pronunciations and meanings.

The time course of anticipatory constraint integration.

Several studies have demonstrated that as listeners hear sentences describing events in a scene, their eye movements anticipate upcoming linguistic items predicted by the unfolding relationship between scene and sentence. While this may reflect active prediction based on structural or contextual expectations, the influence of local thematic priming between words has not been fully examined. In Experiment 1, we presented verbs (e.g., arrest) in active (Subject-Verb-Object) sentences with displays containing verb-related patients (e.g., crook) and agents (e.g., policeman). We examined patient and agent fixations following the verb, after the agent role had been filled by another entity, but prior to bottom-up specification of the object. Participants were nearly as likely to fixate agents "anticipatorily" as patients, even though the agent role was already filled. However, the patient advantage suggested simultaneous influences of both local priming and active prediction. In Experiment 2, using passive sentences (Object-Verb-Subject), we found stronger, but still graded influences of role prediction when more time elapsed between verb and target, and more syntactic cues were available. We interpret anticipatory fixations as emerging from constraint-based processes that involve both non-predictive thematic priming and active prediction.

Involvement of the left inferior frontal gyrus in predictive inference making.

Although predictive inference in reading has been extensively investigated with behavioral paradigms, little is known about its neural substrates. Manipulating the likelihood that a particular event can be predicted from the content of a preceding three-sentence story, the present functional MRI study showed that the left inferior frontal gyrus (LIFG) and the right lingual gyrus were involved in predictive inference generation. It is suggested that the LIFG was responsible for the construction of predictive inference and the right lingual gyrus for integrating the constructed inference into a coherent text representation. Combined with previous research, the results provide brain imaging evidence consistent with predictions from the Schmalhofer et al. model (Discourse Processes, 33, 105-13, 2002) which intends to unify predictive inference and bridging inference in a single theoretical framework.

Functional MRI of conventional and anomalous metaphors in Mandarin Chinese.

This study looks at whether conventional and anomalous metaphors are processed in different locations in the brain while being read when compared with a literal condition in Mandarin Chinese. We find that conventional metaphors differ from the literal condition with a slight amount of increased activation in the right inferior temporal gyrus. In addition, when the anomalous metaphor condition is compared with the literal condition, increased activation occurs bilaterally in the frontal and temporal gyri. Lastly, the comparison between the anomalous and conventional metaphor conditions shows bilateral activation in the middle frontal gyrus and the precentral gyrus, and right-hemisphere activation in the superior frontal gyrus. Left hemisphere activation is found in the inferior frontal gyrus and fusiform gyrus. The left hemisphere activation in the frontal and temporal gyri point to the recruitment of traditional language-based areas for anomalous metaphor sentences, while the right-hemisphere activation found suggests that remote associations are being formed. In short, our study supports the idea that metaphors are not a homogenous type of figurative language and that distinguishing between different types of metaphors will advance theories of language comprehension.

Correlation between temporal response of fMRI and fast reaction time in a language task.

Correlation between behavioral parameters and fMRI responses can provide an advanced understanding of the neuronal processes. A lexical decision task was employed to examine the correlation between the reaction time (RT) and the temporal parameters in event-related BOLD responses. Word frequency was manipulated in the experiment. RTs for high-frequency, low-frequency and pseudowords were measured during fMRI (417 +/- 9 ms, 631 +/- 22 ms and 658 +/- 15 ms, respectively). For high-frequency words, RTs were significantly shorter than that for low-frequency and pseudowords (p < 0.0005). In the left inferior frontal region, the FWHM of the fMRI responses was significantly correlated with RT (p < 0.001), which may correspond to areas with sustained activation during the whole processing.

Blood oxygenation level-dependent MRI of cerebral gliomas during breath holding.

PURPOSE: To assess the cerebrovascular responses to short breath holding of cerebral gliomas using blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI). MATERIALS AND METHODS: Six patients with a low-grade glioma and one patient with a high-grade glioma were studied using T2*-weighted echo planar imaging (EPI) during repeated periods of 15-second or 20-second breath-holding. Tumor vascularity was evaluated using dynamic susceptibility contrast perfusion MRI. RESULTS: Increases in BOLD signal intensity during repeated breath-holding were consistently identified in patients' normal appearing gray matter, comparable with those in healthy adults. Absence of significant BOLD signal enhancement was noted both in low-grade and high-grade gliomas, which is either due to overwhelming hypoxia in a tumor, inadequacy or absence of hypercapnia-induced vasodilatation of tumor vessels, or both. Breath-hold regulated decreases in BOLD signals occurred only in the high-grade glioma, which is most likely due to the hypercapnia-induced steal effect that redistributes blood flow from tumor regions with unresponsive neovasculature to surrounding normal tissue. CONCLUSION: BOLD MRI during short breath holding can disclose differential cerebrovascular response between normal tissue and cerebral glioma.