Chemical heterogeneity of the living human brain: A proton MR spectroscopystudy on the effects of sex, age, and brain region

Brain chemistry was compared between 19 male and female normal volunteers i n the age group 19-31 years, across six brain regions and nine metabolites using in vivo proton magnetic resonance spectroscopy. The relative concentr ations of N-acetyl aspartate, choline, glutamate, glutamine, GABA, inositol , glucose, and lactate were measured relative to creatine within 8 cm(3) br ain voxels. These measurements were performed in six brain regions: thalamu s and cingulate, insula, sensorimotor, dorsolateral prefrontal, and orbital frontal cortices in the left hemisphere, Total metabolite concentration wa s highest in prefrontal regions (28% higher in orbital frontal cortex and 1 8.7% higher in dorsolateral prefrontal cortex compared with insula and thal amus, P < 10(-7)). Subjects 25-31 years of age demonstrated a significant i ncrease in total metabolite concentration in the orbital frontal cortex (35 %, P < 10(-7)) and sensorimotor cortex (16.7%, P < 10(-5)) compared to thos e 19-20 years of age. These two brain regions also showed gender dependence , with women demonstrating increased metabolite concentrations compared to men (9% increase in sensorimotor cortex, P < 0.002, and 2.1% in orbital fro ntal cortex). Most other brain regions showed no gender- or age-dependent d ifferences. The results indicate that the living human brain is chemically heterogeneous. The chemical heterogeneity is sex and age dependent and spec ific for brain region. (C) 2000 Academic Press.