Magnetic resonance spectroscopy (MRS) is a powerful noninvasive approach for the identification, visualization, and quantification of specific brain biochemicals (metabolites and neurotransmitters), thus enabling the direct assessment of the neurochemical status of discrete brain structures. Whereas MRI detects the spatial distribution and tissue density of hydrogen nuclei (1H) in water and fat, MRS measures 1H of typically carbon-containing compounds that are in sufficiently high concentrations to be detected (van der Graaf, 2010). A predominant MRS signal in the healthy human brain is N-acetylaspartate (NAA), found almost exclusively in neurons (Urenjak et al., 1993; Petroff et al., 1995) and thus considered a marker of neuronal integrity. Choline-containing (Cho) compounds, including free Cho, phosphocholine, and glycerophosphocholine, are associated with cell membrane synthesis, turnover, and metabolism (Stoll et al., 1995). The signal from total creatine (tCr), often used as a referent for other metabolites, is influenced by the state of high-energy phosphate metabolism (Tedeschi et al., 1995).
