Ketamine, which blocks the NMDA receptor and temporarily mimics schizophrenia-like symptoms, primarily disrupts how the brain processes distracting stimuli rather than targets or rewards. In a visual attention task with reward-related distractors, healthy volunteers given a subclinical dose of ketamine showed increased gamma band power compared to placebo, especially during salient distractor trials. These effects were linked to the occurrence of negative symptoms. The findings highlight the glutamate system's role in dysfunctional gamma oscillations, early salience processing alterations, and negative symptoms in schizophrenia.
A reduction in the early auditory evoked gamma-band response (aeGBR), a type of brain wave, is seen in both schizophrenia patients and healthy people given ketamine, which mimics the brain's excitation/inhibition imbalance thought to underlie the disorder. This change in brain activity is linked to negative symptoms. In a study of 24 healthy men, ketamine alone reduced the aeGBR amplitude and increased negative symptoms as measured by the PANSS scale. Pretreatment with the amino acid glycine lessened both the brain-wave alteration and the symptom increase in those who responded to glycine. The aeGBR may serve as a biomarker to identify schizophrenia patients with negative symptoms who could benefit from glutamatergic treatments.