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Magnetic Resonance Spectroscopy

Magnetic resonance spectroscopy (MRS), a technique analogous to MRI and fMRI, reveals information about the brain’s use of energy, cell formation and neuronal activity. Using the same principles as MRI, MRS detect molecules that behave like magnets in a magnetic field. In addition to tracking hydrogen in the brain, MRS has particular potential because it can also track other particles such as phosphorus and carbon.

Unlike MRI and fMRI, MRS does not give striking pictures of the brain, but instead, more complex graphs called spectra are produced. As with MRI, radiowaves at a specific frequency called the resonant frequency, allow particles to be deflected in a magnetic field. This resonant frequency is different for different particles, but the specific resonant frequency of one particle, changes depending on its environment e.g. hydrogen attached to a carbon molecule in glucose will have a different resonant frequency compared with hydrogen attached to carbon in a fat molecule.

MRS measurements have been particularly useful in schizophrenia research. While structural brain analyses show that areas of the brain in schizophrenia are smaller than in controls, MRS can give an indication of whether these size differences correlate with changes in cell metabolism, energy use and neuronal number. For example, SCP is using hydrogen MRS to investigate neuronal numbers in the study of first episode psychosis.

Recent uses of MRS in schizophrenia:

  • N-acetyl residues such as N-acetyl aspartate (NAA) show up on 1-H MRS. NAA is thought to reflect the number of neurons present but its exact role in the brain is not clear. In schizophrenia magnetic resonance spectroscopy has shown abnormal levels of NAA in the hippocampal area and dorsolateral prefrontal cortex of patients with schizophrenia.
  • Phospholipids are associated with cell synthesis and breakdown. While the phosphomonoester (PME) is associated with cell membrane formation, the phosphodiester (PDE) is a product of membrane breakdown. Phosphorus MRS detects the presence and amount of both these compounds. In schizophrenia, studies of PDE/PME ratios have not so far produced conclusive results.