Comparison Of MR Spectroscopy and Functional MRI during Language Processing in Children.

Abstract:
The present investigation compares MR Spectroscopy (MRS) to functional MRI (fMRI) during language processing in children. MRS measures changes in the intracellular metabolism of the brain, while fMRI measures changes in blood oxygenation. Proton spectra were acquired using Proton Echo-Planar Spectroscopic Imaging (PEPSI), which allows fast spectroscopic imaging. A 20mm axial slice along the Sylvian (lateral) fissure was selected for spectroscopic imaging (TR/TE 4000/272, 256x32x32 matrix). Eight 7mm axial slices parallel to the anterior-posterior commissure line were selected for fMRI imaging (TR/TE 3000/40, 64x64 matrix, 90 degree flip angle). Fifteen young males (ages 8-13) participated in PEPSI and fMRI sessions that required rhyme and semantic judgments to aurally presented stimuli. We have previously demonstrated differences in lactate levels during PEPSI with these stimuli and found increased lactate responses in anterior quadrants bilaterally for rhyme judgments and right posterior regions for semantic judgments. A quadrant-based analysis technique is used here to examine and compare activation patterns between the 20 mm slice acquired with PEPSI and four corresponding slices acquired with fMRI in perisylvian language areas. Premlinary results indicate correspondence between metabolic measures within quadrants and across imaging modalities during language tasks.