A single volume proton (1H) MR spectroscopy study with chronic smokers (36 ± 11 years of age) observed lower N-acetylaspartate (NAA) concentration (surrogate marker of neuronal integrity [94,95]), in the left hippocampus relative to NSC. No group differences were observed for NAA in the anterior cingulate cortex (ACC), but choline-containing compound (Cho) levels (a marker of cell membrane turnover/synthesis [94,96]) were positively related to greater pack years in this region [97]. A single voxel 1H spectroscopy study of glutamate levels in the left hippocampus and ACC observed no differences among current smokers (35 ± 10 years of age), former smokers (42 ± 10 years of age) abstinent for 17 ± 3 years and NSC (33 ± 10 years of age) [98]. In the sole 1H spectroscopy study investigating gamma aminobutyric acid levels (GABA; neuromodulator involved in the development and maintenance of substance use disorders [99–101]) in chronic smokers, cortical GABA concentrations were lower in female smokers (and modulated by menstrual cycle phase), but GABA levels were not different between male smokers and NSC [102].
