T139. Ketamine and Attentional Bias to Threat: MEG Correlates of Stimulus-Evoked Gamma-Band Response
Section snippets
Background
The glutamatergic modulator ketamine has rapid antidepressant effects in individuals with major depressive disorder (MDD). Thus, modulating glutamatergic transmission may be crucial to effectively treating depression, though the mechanisms by which this occurs are not fully understood. Recent findings suggest that AMPA-mediated glutamatergic neurotransmission following synaptic potentiation leads to increased stimulus-evoked gamma-band responses, which could provide one explanation for how
Methods
Sixteen drug-free patients with MDD participated in a double-blind crossover, placebo-controlled experiment where an intravenous subanesthetic dose of ketamine hydrochloride (0.5 mg/kg) was compared to a placebo-saline infusion scan. Magnetoencephalographic recordings were collected approximately 6.5 hours following both ketamine and placebo infusions. During scanning, the brain correlates underlying facial processing and attentional bias were examined using a dot probe task with emotional face
Results
A network of regions showed enhanced stimulus-evoked gamma-band responses to angry congruent compared with angry incongruent faces, including bilateral superior parietal lobule, bilateral middle temporal gyrus, bilateral middle frontal gyrus, left superior temporal gyrus, left superior frontal gyrus, and left amygdala. In contrast, no regions showed significantly enhanced gamma-band responses to happy congruent compared with happy incongruent faces.
Conclusions
These findings add to a growing literature showing that attentional bias to threat recruits a network of brain regions. It also adds to a growing literature on stimulus-evoked gamma-band responses following ketamine administration. Ongoing work will model ketamine-mediated fronto-amygdala connectivity.
Supported By
NIMH Intramural Research Program
Keywords
Magnetoencephalography, Major Depressive Disorder (MDD), Ketamine, Gamma