@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 {190, title = {Signed words in the congenitally deaf evoke typical late lexicosemantic responses with no early visual responses in left superior temporal cortex.}, journal = {J Neurosci}, volume = {32}, year = {2012}, month = {2012 Jul 11}, pages = {9700-5}, abstract = {

Congenitally deaf individuals receive little or no auditory input, and when raised by deaf parents, they acquire sign as their native and primary language. We asked two questions regarding how the deaf brain in humans adapts to sensory deprivation: (1) is meaning extracted and integrated from signs using the same classical left hemisphere frontotemporal network used for speech in hearing individuals, and (2) in deafness, is superior temporal cortex encompassing primary and secondary auditory regions reorganized to receive and process visual sensory information at short latencies? Using MEG constrained by individual cortical anatomy obtained with MRI, we examined an early time window associated with sensory processing and a late time window associated with lexicosemantic integration. We found that sign in deaf individuals and speech in hearing individuals activate a highly similar left frontotemporal network (including superior temporal regions surrounding auditory cortex) during lexicosemantic processing, but only speech in hearing individuals activates auditory regions during sensory processing. Thus, neural systems dedicated to processing high-level linguistic information are used for processing language regardless of modality or hearing status, and we do not find evidence for rewiring of afferent connections from visual systems to auditory cortex.

}, keywords = {Adolescent, Adult, Brain Mapping, Deafness, Evoked Potentials, Female, Functional Laterality, Humans, Magnetic Fields, Magnetic Resonance Imaging, Magnetoencephalography, Male, Photic Stimulation, Semantics, Sign Language, Temporal Lobe, Time Factors, Young Adult}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.1002-12.2012}, author = {Leonard, Matthew K and Ferjan Ramirez, Naja and Torres, Christina and Travis, Katherine E and Hatrak, Marla and Mayberry, Rachel I and Halgren, Eric} } @article {191, title = {Spatiotemporal dynamics of bilingual word processing.}, journal = {Neuroimage}, volume = {49}, year = {2010}, month = {2010 Feb 15}, pages = {3286-94}, abstract = {

Studies with monolingual adults have identified successive stages occurring in different brain regions for processing single written words. We combined magnetoencephalography and magnetic resonance imaging to compare these stages between the first (L1) and second (L2) languages in bilingual adults. L1 words in a size judgment task evoked a typical left-lateralized sequence of activity first in ventral occipitotemporal cortex (VOT: previously associated with visual word-form encoding) and then ventral frontotemporal regions (associated with lexico-semantic processing). Compared to L1, words in L2 activated right VOT more strongly from approximately 135 ms; this activation was attenuated when words became highly familiar with repetition. At approximately 400 ms, L2 responses were generally later than L1, more bilateral, and included the same lateral occipitotemporal areas as were activated by pictures. We propose that acquiring a language involves the recruitment of right hemisphere and posterior visual areas that are not necessary once fluency is achieved.

}, keywords = {Adolescent, Adult, Brain, Brain Mapping, Female, Functional Laterality, Humans, Magnetoencephalography, Male, Multilingualism, Nerve Net, Pattern Recognition, Visual, Reading, Semantics, Young Adult}, issn = {1095-9572}, doi = {10.1016/j.neuroimage.2009.12.009}, author = {Leonard, Matthew K and Brown, Timothy T and Travis, Katherine E and Gharapetian, Lusineh and Hagler, Donald J and Dale, Anders M and Elman, Jeffrey L and Halgren, Eric} }