@article {205, title = {Age-related changes in tissue signal properties within cortical areas important for word understanding in 12- to 19-month-old infants.}, journal = {Cereb Cortex}, volume = {24}, year = {2014}, month = {2014 Jul}, pages = {1948-55}, abstract = {

Recently, our laboratory has shown that the neural mechanisms for encoding lexico-semantic information in adults operate functionally by 12-18 months of age within left frontotemporal cortices (Travis et al., 2011. Spatiotemporal neural dynamics of word understanding in 12- to 18-month-old-infants. Cereb Cortex. 8:1832-1839). However, there is minimal knowledge of the structural changes that occur within these and other cortical regions important for language development. To identify regional structural changes taking place during this important period in infant development, we examined age-related changes in tissue signal properties of gray matter (GM) and white matter (WM) intensity and contrast. T1-weighted surface-based measures were acquired from 12- to 19-month-old infants and analyzed using a general linear model. Significant age effects were observed for GM and WM intensity and contrast within bilateral inferior lateral and anterovental temporal regions, dorsomedial frontal, and superior parietal cortices. Region of interest (ROI) analyses revealed that GM and WM intensity and contrast significantly increased with age within the same left lateral temporal regions shown to generate lexico-semantic activity in infants and adults. These findings suggest that neurophysiological processes supporting linguistic and cognitive behaviors may develop before cellular and structural maturation is complete within associative cortices. These results have important implications for understanding the neurobiological mechanisms relating structural to functional brain development.

}, keywords = {Aging, Brain Mapping, Cerebral Cortex, Comprehension, Female, Humans, Image Processing, Computer-Assisted, Infant, Language Development, Magnetic Resonance Imaging, Male, Vocabulary}, issn = {1460-2199}, doi = {10.1093/cercor/bht052}, author = {Travis, Katherine E and Curran, Megan M and Torres, Christina and Leonard, Matthew K and Brown, Timothy T and Dale, Anders M and Elman, Jeffrey L and Halgren, Eric} } @article {185, title = {Neural language processing in adolescent first-language learners.}, journal = {Cereb Cortex}, volume = {24}, year = {2014}, month = {2014 Oct}, pages = {2772-83}, abstract = {

The relation between the timing of language input and development of neural organization for language processing in adulthood has been difficult to tease apart because language is ubiquitous in the environment of nearly all infants. However, within the congenitally deaf population are individuals who do not experience language until after early childhood. Here, we investigated the neural underpinnings of American Sign Language (ASL) in 2 adolescents who had no sustained language input until they were approximately 14 years old. Using anatomically constrained magnetoencephalography, we found that recently learned signed words mainly activated right superior parietal, anterior occipital, and dorsolateral prefrontal areas in these 2 individuals. This spatiotemporal activity pattern was significantly different from the left fronto-temporal pattern observed in young deaf adults who acquired ASL from birth, and from that of hearing young adults learning ASL as a second language for a similar length of time as the cases. These results provide direct evidence that the timing of language experience over human development affects the organization of neural language processing.

}, keywords = {Adolescent, Adult, Age Factors, Cerebral Cortex, Critical Period (Psychology), Deafness, Female, Functional Laterality, Humans, Language Development, Learning, Magnetoencephalography, Male, Semantics, Sign Language, Young Adult}, issn = {1460-2199}, doi = {10.1093/cercor/bht137}, author = {Ferjan Ramirez, Naja and Leonard, Matthew K and Torres, Christina and Hatrak, Marla and Halgren, Eric and Mayberry, Rachel I} } @article {192, title = {Language proficiency modulates the recruitment of non-classical language areas in bilinguals.}, journal = {PLoS One}, volume = {6}, year = {2011}, month = {2011}, pages = {e18240}, abstract = {

Bilingualism provides a unique opportunity for understanding the relative roles of proficiency and order of acquisition in determining how the brain represents language. In a previous study, we combined magnetoencephalography (MEG) and magnetic resonance imaging (MRI) to examine the spatiotemporal dynamics of word processing in a group of Spanish-English bilinguals who were more proficient in their native language. We found that from the earliest stages of lexical processing, words in the second language evoke greater activity in bilateral posterior visual regions, while activity to the native language is largely confined to classical left hemisphere fronto-temporal areas. In the present study, we sought to examine whether these effects relate to language proficiency or order of language acquisition by testing Spanish-English bilingual subjects who had become dominant in their second language. Additionally, we wanted to determine whether activity in bilateral visual regions was related to the presentation of written words in our previous study, so we presented subjects with both written and auditory words. We found greater activity for the less proficient native language in bilateral posterior visual regions for both the visual and auditory modalities, which started during the earliest word encoding stages and continued through lexico-semantic processing. In classical left fronto-temporal regions, the two languages evoked similar activity. Therefore, it is the lack of proficiency rather than secondary acquisition order that determines the recruitment of non-classical areas for word processing.

}, keywords = {Adult, Brain Mapping, Female, Humans, Language, Language Development, Magnetic Resonance Imaging, Magnetoencephalography, Male, Multilingualism, Young Adult}, issn = {1932-6203}, doi = {10.1371/journal.pone.0018240}, author = {Leonard, Matthew K and Torres, Christina and Travis, Katherine E and Brown, Timothy T and Hagler, Donald J and Dale, Anders M and Elman, Jeffrey L and Halgren, Eric} }