DIFFERENTIAL DISTRIBUTION OF NAA AND NAAG IN HUMAN BRAIN AS DETERMINED BY QUANTITATIVE LOCALIZED PROTEIN MRS

Quantitative proton magnetic resonance spectroscopy was performed in f rontal, parietal and occipital white and gray matter of young adults w ith use of a fully relaxed, short-echo time stimulated echo acquisitio n mode localization sequence at 2.0 T. Separate concentrations of the neuronal compounds N-acetylaspartate (NAA) and N-acetylaspartylglutama te (NAAG) were obtained by user-independent spectral analysis (LCModel ), Except for occipital gray matter in which an NAA concentration of 1 0.1+/-1.0 mM correlated with enhanced neuronal density in visual corte x, NAA was found to be homogeneously distributed throughout cortical w hite and gray matter at a concentration of 8.0-8.9 mM, NAAG concentrat ions of 1.5-2.7 mM were higher in white matter than levels of 0.6-1.5 mM found in gray matter, contributing up to 25% of total N-acetyl-cont aining compounds, The frontal to parieto occipital increase of both gr ay and white matter NAAG levels is also reflected in the distribution of total NAA, (C) 1997 by John Wiley & Sons, Ltd.