Abstracts

Rationale: Cognitive activities, such as language, require coordinated processing across separate areas of the brain. We examined two fMRI methods of assessing functional connectivity within the language network: ROI-based linear correlation coefficients and individual seed region-based fcMRI analyses. Methods: 58 typically developing, right-handed children ages 4-12 years (28 boys; mean age=8.8 2.6 yr; mean FSIQ=116 14) underwent 3T EPI BOLD fMRI with an auditory description decision task. Data was analyzed in SPM2 using a region of interest (ROI) approach. Regional laterality indices (LI) for Wernicke s area (WA), inferior frontal gyrus (IFG), and middle frontal gyrus (MFG) were calculated using LI toolbox bootstrap method. Categorical language dominance and mean LI were analyzed; left language dominance for each region was defined as LI?0.20. For Method 1, individual linear correlation coefficients were computed between pairs of time course signals extracted from the ROIs to determine the degree to which those brain regions fluctuate synchronously during the task. For Method 2, individual variability in functional activation was accounted for by extracting the time series from the subject s peak voxel coordinates within the ROIs to add as regressors in the general linear model task design matrix. Results: Method 1: Functional connectivity between inter- and intra-hemispheric pairs of language regions was strong did not differ by age (p>.05). Age and task accuracy were correlated (r=0.36, p<.01); controlling for overall accuracy, Left IFG ? Right IFG connectivity was negatively correlated with age (r=-.27, p<.05). Connectivity between left and right WA was correlated with regional LI in temporal (WA: r=-.42, p=.001) and frontal regions (IFG: r=-.34, p<.01; MFG: r=-.34, p<.01); whereas frontal homologue (IFG, MFG) connectivity correlated only with LI in frontal regions (p<.05). Method 2: A priori assumptions of temporally synchronous areas were not required. Areas of activation for all three seed regions included left inferior and middle temporal gyri, left IFG/MFG, and right cerebellum for subjects of all ages. In SPM ANOVAs by age group, the 4-6 year olds showed greater connectivity than the 7-12 year olds with posterior cingulate cortex, right angular gyrus, and left MFG/SFG areas from all three seed regions.