The effect of repetitive transcranial magnetic stimulation on gamma oscillatory activity in schizophrenia

• Published in: PloS one 2011-07, Vol.6 (7), p.e22627-e22627
• Main Authors: Barr, Mera S, Farzan, Faranak, Arenovich, Tamara, Chen, Robert, Fitzgerald, Paul B, Daskalakis, Zafiris J
• Format: Article
• Language: English
• Subjects: Addictions; Adult; Antipsychotic Agents - pharmacology; Antipsychotic Agents - therapeutic use; Antipsychotics; Behavior - drug effects; Biology; Brain; Case-Control Studies; Cognition; Cognitive ability; Cortex (frontal); Cortex (occipital); Demography; Dopamine; Electroencephalography; Evoked Potentials - drug effects; Female; Homeostatic plasticity; Human subjects; Humans; Load; Magnetic fields; Male; Medicine; Memory; Memory, Short-Term - drug effects; Memory, Short-Term - physiology; Mental disorders; Mental health; Middle Aged; Neuropsychological Tests; Oscillations; Parkinson's disease; Parkinsons disease; Patients; Potentiation; Prefrontal cortex; Prefrontal Cortex - drug effects; Prefrontal Cortex - physiopathology; Psychiatry; Psychopathology; Psychopharmacology; Psychotropic drugs; Schizophrenia; Schizophrenia - drug therapy; Schizophrenia - physiopathology; Short term memory; Stimulation; Studies; Transcranial Magnetic Stimulation; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0022627

Gamma (γ) oscillations (30-50 Hz) have been shown to be excessive in patients with schizophrenia (SCZ) during working memory (WM). WM is a cognitive process that involves the online maintenance and manipulation of information that is mediated largely by the dorsolateral prefrontal cortex (DLPFC). Repetitive transcranial magnetic stimulation (rTMS) represents a non-invasive method to stimulate the cortex that has been shown to enhance cognition and γ oscillatory activity during WM. We examined the effect of 20 Hz rTMS over the DLPFC on γ oscillatory activity elicited during the N-back task in 24 patients with SCZ compared to 22 healthy subjects. Prior to rTMS, patients with SCZ elicited excessive γ oscillatory activity compared to healthy subjects across WM load. Active rTMS resulted in the reduction of frontal γ oscillatory activity in patients with SCZ, while potentiating activity in healthy subjects in the 3-back, the most difficult condition. Further, these effects on γ oscillatory activity were found to be specific to the frontal brain region and were absent in the parieto-occipital brain region. We suggest that this opposing effect of rTMS on γ oscillatory activity in patients with SCZ versus healthy subjects may be related to homeostatic plasticity leading to differential effects of rTMS on γ oscillatory activity depending on baseline differences. These findings provide important insights into the neurophysiological mechanisms underlying WM deficits in SCZ and demonstrated that rTMS can modulate γ oscillatory activity that may be a possible avenue for cognitive potentiation in this disorder.