No association between dorsolateral prefrontal gray matter deficit and N-acetyl aspartate ratios in schizophrenia

The cellular substrates of cortical volume deficit in schizophrenia are unclear. We may hypothesize that, if that deficit was related to a decrease in the amount in neuronal tissue, it should correlate with N-acetyl aspartate levels. We studied a group of 34 schizophrenia patients (of them, 17 first episodes) with both structural and spectroscopic magnetic resonance (MR). Using the data of 50 controls, we were able to calculate for each case residuals of gray matter and cortical cerebrospinal fluid (CSF) in the dorsolateral prefrontal (DLPF) region, representing the deviation from the expected values in normals, given individual intracranial volume and age. Although our patients showed a significant deficit in gray matter and excess in cortical CSF in the DLPF region, that deficit was unrelated to N-acetyl aspartate levels. This was also true for the chronic and first episode groups analyzed separately. These results do not support a neuronal tissue deficit as contributing to the cortical volume deficit in schizophrenia, at least in the DLPF region.