Functional investigation of bilateral posterior cingulate gyri using multivoxel MR spectroscopy

The exact functional correlation of each hemisphere's posterior cingulate gyrus with the symptoms of Alzheimer's disease (AD) remains unknown. We attempted to evaluate the relationship between metabolite ratios in each hemisphere's posterior cingulate gyrus and cognitive deficits, using multivoxel magnetic resonance spectroscopy (MRS). We recruited 23 patients with AD, 16 patients with amnestic mild cognitive impairment and 22 cognitively normal subjects. All patients underwent multivoxel MRS in the bilateral posterior cingulate gyri. We statistically analyzed correlations between the N-acetylaspartate/creatine ratio (NAA/Cr) in each posterior cingulate gyrus and patients' raw scores on neuropsychological tests. The NAA/Cr of each posterior cingulate gyrus correlated well with the verbal learning test scores on immediate recall and delayed recall tasks. We found that the only cognitive domain to correlate with the NAA/Cr of each posterior cingulate gyrus was verbal memory. Our results did not show any significant functional difference between right and left posterior cingulate gyri.