TMS-EEG Shows Mindfulness Meditation Is Associated With a Different Excitation/Inhibition Balance in the Dorsolateral Prefrontal Cortex

Objectives: Mindfulness meditation is associated with functional brain changes in regions subserving higher order cognitive processes such as attention. However, no research to date has probed these areas in meditators using combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG). This study aimed to investigate whether cortical reactivity to TMS differs in a community sample of experienced mindfulness meditators when compared to matched controls. 

Method: TMS was applied to the left and right dorsolateral prefrontal cortices (DLPFC) of 19 controls and 15 meditators while brain responses were measured using EEG. TMS-evoked potentials (P60 and N100) were compared between the groups using repeated measures ANOVAs and Mann–Whitney U tests where appropriate, and exploratory analyses using the whole EEG scalp field were performed to test whether TMS-evoked global neural response strength or the distribution of neural activity differed between groups. 

Results: Meditators were found to have statistically larger P60/N100 ratios in response to both left and right hemisphere DLPFC stimulation compared to controls (both left and right p_FDR < 0.01, BF₁₀ > 39). No differences were observed in P60 or N100 amplitudes when examined independently. We also found preliminary evidence for differences in the spatial distribution of neural activity 269–332 ms post stimulation. 

Conclusions: These differences in the distribution of neural activity around 300 ms after stimulation suggest that meditators may have differences in connectivity between cortical and subcortical brain regions, potentially reflecting greater inhibitory activity in frontal regions. This research contributes to our current understanding of the neurophysiology of mindfulness and highlights opportunities for further exploration into the mechanisms underpinning the benefits of mindfulness meditation.