Neurofeedback of meditation states to close the loop between subjective experience and brain activity: Evaluating four neural markers

Abstract

A central challenge in neuroscience is to establish meaningful links between subjective experience and brain activity. Neurofeedback of meditation states has been proposed as a way to address this challenge by creating a real-time loop between neural signals and first-person experience. Here, the introspective and self-regulation capacities of experienced meditators are harnessed to dynamically alter consciousness while exploring relationships with a feedback signal. Previous work using visual feedback of posterior cingulate gamma activity demonstrated a negative relationship with moment-to-moment experience in effortless awareness. In a first confirmatory study we replicate this neuro-experiential correspondance and ask whether it generalizes to auditory feedback, whether neurofeedback supports regulation beyond meditation alone, and to what extent observed effects reflect neural rather than non-neural sources. In a second exploratory study, we evaluate the feasibility of regulating and establishing neuro-experiential correspondances for three additional neural markers (source localized alpha, beta and theta power). Across 17 (study 1) and 12 (study 2) high-density EEG sessions, experienced meditators (n=9 study 1 and n=4 study 2) received visual and auditory feedback (study 1) or only auditory feedback (study 2) of source-localized brain activity. Participants were blind to which signal direction corresponded to deeper meditation, which was randomly flipped across 12 repeated trials. In each trial they identified the direction by comparing their meditation experience to the feedback. Gamma feedback (study 1) showed significantly above-chance accuracy for identifying the expected feedback direction, both for auditory and visual feedback. Feedback based on alpha, beta and theta power (study 2) did not yield significant effects. Across studies, phenomenological interviews revealed differential patterns of enacted meditative gestures, with “letting go of effort and control” dominant in the gamma condition, consistent with the previous characterization of effortless awareness. For the gamma condition, follow-up whole-brain source localization showed that the posterior cingulate cortex contributed only marginally to the effect and additional control analyses suggested potential muscular confounds. We thus replicate the correspondence between effortless awareness and posterior cingulate gamma activity, but also highlight the risk that our own and previous findings are driven by muscle activity. The absence of reliable neuro-experiential associations for other frequency bands less prone to muscle contamination further strengthens these concerns and highlights the intricacies in establishing real-time correspondences between brain activity and subjective experience.