Impaired theta-gamma coupling during working memory performance in schizophrenia.
Working memory deficits represent a core feature of schizophrenia. These deficits have been associated with dysfunctional dorsolateral prefrontal cortex (DLPFC) cortical oscillations. Theta-gamma coupling describes the modulation of gamma oscillations by theta phasic activity that has been directly associated with the ordering of information during working memory performance. Evaluating theta-gamma coupling may provide greater insight into the neural mechanisms mediating working memory deficits in this disorder.



Thirty-eight patients diagnosed with schizophrenia or schizoaffective disorder and 38 healthy controls performed the verbal N-Back task administered at 4 levels, while EEG was recorded. Theta (4-7Hz)-gamma (30-50Hz) coupling was calculated for target and non-target correct trials for each working memory load. The relationship between theta-gamma coupling and accuracy was determined.



Theta-gamma coupling was significantly and selectively impaired during correct responses to target letters among schizophrenia patients compared to healthy controls. A significant and positive relationship was found between theta-gamma coupling and 3-Back accuracy in controls, while this relationship was not observed in patients.



These findings suggest that impaired theta-gamma coupling contribute to working memory dysfunction in schizophrenia. Future work is needed to evaluate the predictive utility of theta-gamma coupling as a neurophysiological marker for functional outcomes in this disorder.
Biobehavioural Addictions and Concurrent Disorders Laboratory (BACDRL), Addictions Division, Canada; Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division, Canada; Department of Psychiatry, Division of Brain and Therapeutics, University of Toronto, Toronto, Canada.
Mera S
MS
Barr
Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division, Canada; Geriatric Psychiatry Division, Centre for Addiction and Mental Health, Canada.
Tarek K
TK
Rajji
Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division, Canada.
Reza
R
Zomorrodi
Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division, Canada.
Natasha
N
Radhu
Biobehavioural Addictions and Concurrent Disorders Laboratory (BACDRL), Addictions Division, Canada; Department of Psychiatry, Division of Brain and Therapeutics, University of Toronto, Toronto, Canada.
Tony P
TP
George
Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division, Canada; Geriatric Psychiatry Division, Centre for Addiction and Mental Health, Canada.
Daniel M
DM
Blumberger
Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division, Canada; Department of Psychiatry, Division of Brain and Therapeutics, University of Toronto, Toronto, Canada. Electronic address: Jeff.Daskalakis@camh.ca.
Zafiris J
ZJ
Daskalakis
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D004569:Electroencephalography; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time / Q000502:physiology; D012559:Schizophrenia / Q000150:complications*; D013826:Theta Rhythm / Q000502:physiology*
DLPFC; Schizophrenia; Theta-gamma coupling; Working memory