Abstracts

Rationale: A distributed network exists in the dominant frontal lobe for the fluent production of speech. This network includes medial frontal pre-motor areas (SMA/pre-SMA), the lateral premotor cortex and the posterior inferior frontal gyrus (Broca’s area). The rapid generation of articulatory code suggests that direct connections exist between these regions. Here we evaluate the relative strength of the connections of Brocas area or its homolog with ipsilateral medial premotor region as a measure of language laterality.Methods: Functional MR images were collected in 13 humans (8 normals, 5 patients w/refractory epilepsy) during multiple language tasks (visual confrontation naming of actions, common and proper nouns, auditory naming and auditory comprehension). Hi-res anatomical and diffusion-weighted images were also collected. For each subject, areas with significant BOLD activation were identified in the fMRI data, across all the language tasks, using AFNI. Language laterality was determined in all 13 subjects using supra-threshold voxels (p<0.0001) in BA44 and BA45, considered together as Broca’s area (L-R/L+R). All 5 patients underwent Wada testing. Structural, fMRI and diffusion weighed images (during application of 32 diffusion-sensitizing gradients) were spatially normalized to the ICBM452 atlas. DTIQuery software was used to compute tensors, and tensor eigenvalues were used to compute fractional anisotropy (FA) maps. In voxels where FA>