title: Gamma and delta neural oscillations and association with clinical symptoms under subanesthetic ketamine.
abstract: Several electrical neural oscillatory abnormalities have been associated with schizophrenia, although the underlying mechanisms of these oscillatory problems are unclear. Animal studies suggest that one of the key mechanisms of neural oscillations is through glutamatergic regulation; therefore, neural oscillations may provide a valuable animal-clinical interface on studying glutamatergic dysfunction in schizophrenia. To identify glutamatergic control of neural oscillation relevant to human subjects, we studied the effects of ketamine, an N-methyl-D-aspartate antagonist that can mimic some clinical aspects of schizophrenia, on auditory-evoked neural oscillations using a paired-click paradigm. This was a double-blind, placebo-controlled, crossover study of ketamine vs saline infusion on 10 healthy subjects. Clinically, infusion of ketamine in subanesthetic dose significantly increased thought disorder, withdrawal-retardation, and dissociative symptoms. Ketamine significantly augmented high-frequency oscillations (gamma band at 40-85 Hz, p=0.006) and reduced low-frequency oscillations (delta band at 1-5 Hz, p<0.001) compared with placebo. Importantly, the combined effect of increased gamma and reduced delta frequency oscillations was significantly associated with more withdrawal-retardation symptoms experienced during ketamine administration (p=0.02). Ketamine also reduced gating of the theta-alpha (5-12 Hz) range oscillation, an effect that mimics previously described deficits in schizophrenia patients and their first-degree relatives. In conclusion, acute ketamine appeared to mimic some aspects of neural oscillatory deficits in schizophrenia, and showed an opposite effect on scalp-recorded gamma vs low-frequency oscillations. These electrical oscillatory indexes of subanesthetic ketamine can be potentially used to cross-examine glutamatergic pharmacological effects in translational animal and human studies.
authors.affiliation: Department of Psychiatry, Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD 21228, USA. ehong@mprc.umaryland.edu
authors.forename: L Elliot
authors.initials: LE
authors.lastname: Hong
authors.forename: Ann
authors.initials: A
authors.lastname: Summerfelt
authors.forename: Robert W
authors.initials: RW
authors.lastname: Buchanan
authors.forename: Patricio
authors.initials: P
authors.lastname: O'Donnell
authors.forename: Gunvant K
authors.initials: GK
authors.lastname: Thaker
authors.forename: Martin A
authors.initials: MA
authors.lastname: Weiler
authors.forename: Adrienne C
authors.initials: AC
authors.lastname: Lahti
mesh_terms: D000328:Adult; D000778:Anesthetics, Dissociative / Q000008:administration & dosage* / Q000009:adverse effects; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D018592:Cross-Over Studies; D003700:Delta Rhythm / Q000187:drug effects*; D004213:Dissociative Disorders / Q000139:chemically induced / Q000503:physiopathology*; D004311:Double-Blind Method; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D055815:Young Adult
chemical_list: D000778:Anesthetics, Dissociative; D007649:Ketamine