The long-term objective of the proposed research is to understand the biological mechanisms underlying individual differences in cerebral lateralization for language. Understanding the factors that determine the variability inherent in normal brain organization is essential in order to effectively treat individuals with unilateral brain injuries. It is proposed that individuals vary both in the degree and consistency of left hemisphere predominance and that these variations have behavioral significance for language processing. A large sample of normal persons will be tested in a series of linguistic tasks in which stimuli are presented to the left and right hemispheres. The tasks measure both basic word recognition, and semantic retrieval, processes. Structural magnetic resonance imaging (MRI) will be performed to assess asymmetries in posterior (planum temporale, planum parietale, Heschl's gyrus) and anterior (pars triangulars, cingulate and paracingulate sulcus) brain regions. It is hypothesized that (1) individuals differ in the extent to which critical cortical regions are asymmetrical and that this structural variability is linked to the inter-hemispheric organization of language function; (2) individuals differ in the consistency of their asymmetries such that some have a consistent pattern of moderate asymmetries across tasks and brain regions, while others show behavioral and anatomical asymmetries that depart from the population mean randomly; and (3) individuals with consistent, typical asymmetries will demonstrate greater speed and accuracy across a variety of nonlateralized lexical tasks. Although treatment for developmental and acquired brain dysfunction is administered individually, the understanding of normal function is based primarily on group averages. Hence, the study of individual differences in uninjured populations can provide a critical bridge between the basic science of cerebral lateralization and its clinical application.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
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Cognitive Neuroscience Study Section (COG)
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Cooper, Judith
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University of California Riverside
Schools of Arts and Sciences
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Felton, Adam; Vazquez, David; Ramos-Nunez, Aurora I et al. (2017) Bilingualism Influences Structural Indices of Interhemispheric Organization. J Neurolinguistics 42:1-11
Chiarello, Christine; Vazquez, David; Felton, Adam et al. (2016) Structural asymmetry of the human cerebral cortex: Regional and between-subject variability of surface area, cortical thickness, and local gyrification. Neuropsychologia 93:365-379
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Welcome, Suzanne E; Chiarello, Christine; Thompson, Paul M et al. (2011) Reading skill is related to individual differences in brain structure in college students. Hum Brain Mapp 32:1194-205
Welcome, Suzanne E; Leonard, Christiana M; Chiarello, Christine (2010) Alternate reading strategies and variable asymmetry of the planum temporale in adult resilient readers. Brain Lang 113:73-83

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