Human brain: biochemical lateralization in normal subjects

Chemical asymmetries in normal human brain were studied using the non-invasive technique of volume localized proton magnetic resonance spectroscopy (MRS). The technique of STEAM was used to acquire water-suppressed proton spectra from 8 ml voxels placed in bilaterally symmetrical positions in the two hemispheres of the brain. One hundred and sixty eight right-handed male volunteers were studied for six different regions in the brain (n=28, for each region). Parietal, occipital, temporal, frontal, thalamus and cerebellum regions were studied. The focus was on metabolites such as N-acetyl aspartate (NAA), creatine/phosphocreatine (Cr/PCr) and choline (Cho) containing compounds. Ratios of the peak areas were calculated for them. Quantitation of the metabolites were carried for data on 18 volunteers. Significant interhemispheric differences in the distribution of metabolites were observed for all the regions studied. There were statistically significant differences on right and left side for the metabolite ratios in all the regions studied. The study has shown the existence of significant lateralization in the distribution of proton MR visible metabolites for all the regions studied.