Additional asymmetries in gray matter volume have been observed within nodes of the default mode network. A diffusion tensor study of a predefined brain parcellation using graph-theoretical methods showed increased efficiency and connectedness within the right hemisphere, but with regions of greatest network centrality in the left hemisphere. It has been well documented that small structural asymmetries consisting of a frontal (right>left) and occipital (left>right) shear effect are present in most individuals, in addition to asymmetries of the planum temporale, angular gyrus, caudate, and insula. Previous studies of brain laterality are largely limited to regional assessment of specialized functions and differences in structural lateralization. Atypical lateralization in brain structure and function is associated with neuropsychiatric disorders such as autism spectrum disorders and schizophrenia –, although there is considerable variation within typically developing individuals in the strength to which specific functions such as language are lateralized to the canonical side, particularly for left-handed and ambidextrous individuals. In most right-handed individuals, paying attention to stimuli involving language elicits brain activity lateralized to the left hemisphere, whereas paying attention to stimuli involving visuospatial processing elicits brain activity lateralized to the right hemisphere –. Lateralized brain regions direct functions such as language and visuospatial processing. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: The project described was supported by NIH grant numbers T32DC008553 (JAN), NIMH K08MH092697 (JSA), and NIMH RO1MH080826 (JEL), the Flamm Family Foundation, the Morrell Family Foundation, the Primary Children’s Medical Center Foundation, and by the Ben B. Received: MaAccepted: JPublished: August 14, 2013Ĭopyright: © 2013 Nielsen et al. PLoS ONE 8(8):Įditor: Yong He, Beijing Normal University, China Right-Brain Hypothesis with Resting State Functional Connectivity Magnetic Resonance Imaging. Small increases in lateralization with age were seen, but no differences in gender were observed.Ĭitation: Nielsen JA, Zielinski BA, Ferguson MA, Lainhart JE, Anderson JS (2013) An Evaluation of the Left-Brain vs. Lateralization of brain connections appears to be a local rather than global property of brain networks, and our data are not consistent with a whole-brain phenotype of greater “left-brained” or greater “right-brained” network strength across individuals. Connections involving only left- or only right-lateralized hubs showed positive correlation across subjects, but only for connections sharing a node. Left- and right-lateralized hubs formed two separable networks of mutually lateralized regions. The left-lateralized hubs included regions from the default mode network (medial prefrontal cortex, posterior cingulate cortex, and temporoparietal junction) and language regions (e.g., Broca Area and Wernicke Area), whereas the right-lateralized hubs included regions from the attention control network (e.g., lateral intraparietal sulcus, anterior insula, area MT, and frontal eye fields). Nine left- and 11 right-lateralized hubs were identified as peaks in the degree map from the graph of significantly lateralized connections. The difference in gray matter density between homotopic coordinates was used as a regressor to reduce the effect of structural asymmetries on functional lateralization. For each subject, functional lateralization was measured for each pair of 7266 regions covering the gray matter at 5-mm resolution as a difference in correlation before and after inverting images across the midsagittal plane. Data were analyzed from publicly available resting state scans for 1011 individuals between the ages of 7 and 29. We evaluated whether strongly lateralized connections covaried within the same individuals. It has been conjectured that individuals may be left-brain dominant or right-brain dominant based on personality and cognitive style, but neuroimaging data has not provided clear evidence whether such phenotypic differences in the strength of left-dominant or right-dominant networks exist. Lateralized brain regions subserve functions such as language and visuospatial processing.