Functional connectivity alterations of the pregenual anterior cingulate cortex by ketamine and the modulation by lamotrigine

Background: Neuroimaging studies have linked the beneficial effects of subanaesthetic ketamine doses in psychiatric conditions characterized by chronic stress pathology (CSP) to altered functional connectivity (FC) within the pregenual anterior cingulate cortex (pgACC). Previous research indicates a potential role of glutamate concentration in FC changes; however, the precise relationship between glutamate release and increased FC remains unclear. Lamotrigine, a glutamate-release inhibitor, allows deeper exploration of this relationship. Additionally, CSP and treatment efficacy are closely associated with alterations in working memory (WM), necessitating the examination of FC during resting state and WM tasks. Aims: This study aimed to investigate the acute and sustained effects of altered glutamate transmission induced by ketamine and lamotrigine on pgACC FC during rest and WM. Methods: In this double-blind, placebo-controlled, randomized, single-dose, parallel-group study, resting-state and task-related functional Magnetic Resonance Imaging (fMRI) data were collected at baseline, during and 24 h after ketamine administration in 75 healthy participants. Participants were randomized to receive ketamine, ketamine with lamotrigine pretreatment or placebo. FC analyses utilized pgACC masks derived from the Julich Brain Atlas. Results: Ketamine infusion significantly enhanced FC between the pgACC and dorsomedial prefrontal cortex during the WM task, and increased resting-state FC between the pgACC and left insula. These effects were absent following lamotrigine pretreatment. Conclusions: The findings support the hypothesis that ketamine’s favourable effects, reflected by enhanced FC within key neural networks, may be attributable to glutamate release.