Marked reductions in visual evoked responses but not γ-aminobutyric acid concentrations or γ-band measures in remitted depression

Biol Psychiatry. 2013 Apr 1;73(7):691-8. doi: 10.1016/j.biopsych.2012.09.032. Epub 2012 Nov 28.


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.

MeSH terms

  • Adolescent
  • Adult
  • Brain / metabolism
  • Brain / physiology
  • Brain Waves / physiology*
  • Case-Control Studies
  • Depression / diagnosis
  • Depression / metabolism*
  • Depression / physiopathology*
  • Evoked Potentials, Visual / physiology*
  • Female
  • Functional Neuroimaging / psychology
  • Glutamic Acid / metabolism
  • Glutamine / metabolism
  • Humans
  • Visual Cortex / physiology*
  • gamma-Aminobutyric Acid / metabolism*


  • Glutamine
  • Glutamic Acid
  • gamma-Aminobutyric Acid