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Hum Brain Mapp. 2016 May;37(5):1941-52. doi: 10.1002/hbm.23148. Epub 2016 Feb 25.

Ketamine administration reduces amygdalo-hippocampal reactivity to emotional stimulation.

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Department of Psychiatry, Psychotherapy and Psychosomatics, Zürich University Hospital for Psychiatry, Switzerland.
Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.
Clinical Affective Neuroimaging Laboratory, Leibniz Institute for Neurobiology, Otto-von-Guericke University, Magdeburg, Germany.
Neuropsychopharmacology and Brain Imaging & Heffter Research Center, Department of Psychiatry Psychotherapy and Psychosomatics, Zürich University Hospital for Psychiatry, Switzerland.
Department of Psychiatry, Charité, CBF, Berlin, Germany.


Increased amygdala reactivity might lead to negative bias during emotional processing that can be reversed by antidepressant drug treatment. However, little is known on how N-methyl-d-aspartate (NMDA) receptor antagonism with ketamine as a novel antidepressant drug target might modulate amygdala reactivity to emotional stimulation. Using functional magnetic resonance imaging (fMRI) and resting-state fMRI (rsfMRI), we assessed amygdalo-hippocampal reactivity at baseline and during pharmacological stimulation with ketamine (intravenous bolus of 0.12 mg/kg, followed by a continuous infusion of 0.25 mg/kg/h) in 23 healthy subjects that were presented with stimuli from the International Affective Picture System (IAPS). We found that ketamine reduced neural reactivity in the bilateral amygdalo-hippocampal complex during emotional stimulation. Reduced amygdala reactivity to negative pictures was correlated to resting-state connectivity to the pregenual anterior cingulate cortex. Interestingly, subjects experienced intensity of psychedelic alterations of consciousness during ketamine infusion predicted the reduction in neural responsivity to negative but not to positive or neutral stimuli. Our findings suggest that the pharmacological modulation of glutamate-responsive cerebral circuits, which is associated with a shift in emotional bias and a reduction of amygdalo-hippocampal reactivity to emotional stimuli, represents an early biomechanism to restore parts of the disrupted neurobehavioral homeostasis in MDD patients. Hum Brain Mapp 37:1941-1952, 2016.


antidepressants; depression; emotional processing; fMRI; glutamate; ketamine

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