PLoS ONE
September 24, 2012
Milan Scheidegger, Martin Walter, Mick Lehmann et al.
282 citations
Ketamine, an NMDA receptor antagonist that modulates glutamate signaling, rapidly reduces functional connectivity between the default mode network (DMN) and the dorsal nexus, a dorsal medial prefrontal cortex region linked to depression. In a randomized, placebo-controlled, double-blind, crossover resting-state fMRI study in healthy subjects, ketamine decreased connectivity from the DMN's posterior cingulate cortex hub to the dorsal nexus, pregenual anterior cingulate, and medioprefrontal cortex. This subacute modulation at 24 hours overlaps with ketamine's peak antidepressant efficacy in treatment-resistant depression, suggesting that targeting glutamatergic system-driven network dysconnectivity may underlie successful depression treatment.
Human Brain Mapping
February 25, 2016
Milan Scheidegger, A Henning, Martin Walter et al.
78 citations
Ketamine, an NMDA receptor antagonist, reduced neural reactivity in the bilateral amygdalo-hippocampal complex during emotional stimulation in 23 healthy subjects. Reduced amygdala reactivity to negative pictures correlated with resting-state connectivity to the pregenual anterior cingulate cortex. The intensity of psychedelic alterations of consciousness during ketamine infusion predicted the reduction in neural responsivity to negative but not to positive or neutral stimuli. These findings suggest that modulation of glutamate-responsive circuits, associated with a shift in emotional bias and reduced amygdalo-hippocampal reactivity, may represent an early mechanism to restore disrupted neurobehavioral homeostasis in major depressive disorder.
Social Cognitive and Affective Neuroscience
April 13, 2016
Mick Lehmann, Erich Seifritz, A Henning et al.
58 citations
Distraction and rumination are distinct ways people respond to negative thoughts and feelings. Rumination involves elevated self-focus, linked to increased resting state functional connectivity and decreased reactivity within the default mode network. The NMDA receptor antagonist ketamine reduces functional connectivity in this network, but its effects on brain responses during stimulus perception were unknown. In healthy subjects given a single ketamine dose, blood oxygenation level-dependent (BOLD) reactivity to negative emotional pictures increased specifically in the pregenual anterior cingulate cortex, not in a posterior control region. The increase was greater in subjects with low ability to use distraction during negative experiences. Ketamine may attenuate pathological increased self-focus during negative experiences.
European Archives of Psychiatry and Clinical Neuroscience
January 12, 2022
Matti Gärtner, Anne Weigand, Milan Scheidegger et al.
13 citations
Ketamine's rapid antidepressant effects involve the glutamatergic system. A multimodal imaging study of 23 healthy volunteers used resting state fMRI and proton magnetic resonance spectroscopy to examine links between metabolic and functional brain changes during intravenous ketamine infusion. The pregenual anterior cingulate cortex (pgACC) was the focus. Functional connectivity changed from the pgACC to the right frontal pole and anterior mid cingulate cortex (aMCC). Absolute glutamate and glutamine concentrations in the pgACC did not differ significantly from baseline. Stronger pgACC activation during ketamine was linked to lower glutamine concentration, and reduced connectivity between pgACC and aMCC was related to increased pgACC activation and reduced glutamine.