Glutamatergic deficit and schizophrenia-like negative symptoms: new evidence from ketamine-induced mismatch negativity alterations in healthy male humans

Mean values of the 5 dimensions of the Altered State of Consciousness (5D-ASC) questionnaire subscores, with error bars representing ± 1 standard error of the mean. AUA = auditory alterations; DED = dread of ego dissolution; OBN = oceanic boundlessness; VIR = vigilance reduction; VRS = visionary restructuralization. *p < 0.05, ***p < 0.001, Bonferroni-corrected for multiple comparisons.

Grand averages (n = 24) of mismatch negativity (MMN) difference waves under ketamine administration (dashed lines) and placebo administration (solid lines). (A) Difference between standard and duration-deviant trials. (B) Difference between standard and frequency-deviant trials. A reduction of MMN peak amplitudes under ketamine administration at the frontal electrode Fz can be observed between 80 ms and 200 ms. *p < 0.05, **p < 0.01.

Topographic maps (n = 24) derived from the mismatch negativity (MMN) difference waves of (A) the duration deviant and (B) the frequency deviant for the timeframe 148–168 ms after stimulus onset.

Significant multivariate analysis of variance results, with (A) mismatch negativity (MMN) amplitude of the duration deviant and (B) MMN amplitude of the frequency deviant as dependent variables and the Positive and Negative Syndrome Scale (PANSS) negative factor as a predictor.