Abstract
Background: Magnetic resonance spectroscopy (MRS) studies have consistently demonstrated reduced cortical γ-aminobutyric acid (GABA) concentrations in individuals with major depression. However, evidence for a persistent deficit during remission, which would suggest that GABA dysfunction is a possible trait marker of depression, is equivocal. Although MRS measures total concentration of GABA, magneto-encephalography provides direct measures of neural activity, with cortical γ oscillations shaped by the activity of GABAergic inhibitory interneurons. In this study we investigated whether γ oscillations and GABA concentrations would differ in individuals with remitted depression (RD) compared with never depressed control subjects (ND). Methods: Thirty-seven healthy, unmedicated female volunteers (n = 19 RD, and n = 18 ND) were recruited. The γ oscillation frequencies and amplitudes in the visual cortex, induced by simple grating stimuli, were quantified with time-frequency analyses. Distinct GABA/glutamate + glutamine MRS peaks were resolved from MEGA-PRESS difference spectra in prefrontal, occipital, and subcortical volumes. Results: The RD and ND individuals did not differ in the frequency of subclinical depressive symptoms. The ND were slightly older (mean = 23 years vs. 21 years), but age did not correlate with dependent measures. There were no group differences in GABA levels or induced cortical γ measures, but RD individuals had markedly reduced M80 (C1) components of the pattern-onset evoked response (46% reduction, Cohen's d = 1.01, p =.006). Conclusions: Both MRS and magneto-encephalography measures of the GABA system are normal in RD. However, the early visual evoked response is a potential trait marker of the disorder.
Original language | English (US) |
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Pages (from-to) | 691-698 |
Number of pages | 8 |
Journal | Biological psychiatry |
Volume | 73 |
Issue number | 7 |
DOIs | |
State | Published - Apr 1 2013 |
Keywords
- Biomarker
- C1
- GABA
- MEG
- MRS
- depression
- neuroimaging
- trait
- visual evoked response
- γ
ASJC Scopus subject areas
- Biological Psychiatry