Nonlinear EEG signatures of mind wandering during breath focus meditation

Summary

During breath focus meditation, novice practitioners often experience mind wandering. Previous EEG studies using linear metrics have produced inconsistent results. This study assessed whether nonlinear EEG signatures could characterize mind wandering. Twenty-five participants were interrupted during meditation to report whether they were focusing on the breath or thinking about something else. EEG complexity was measured using three algorithms: Higuchi’s fractal dimension, Lempel-Ziv complexity, and sample entropy. EEG complexity was generally reduced during mind wandering compared to breath focus states. The authors conclude that EEG complexity metrics can distinguish mind wandering from breath focus in novice practitioners and could be used in future EEG neurofeedback protocols.

Study at a glance

Abstract

In meditation practices that involve focused attention to a specific object, novice practitioners often experience moments of distraction (i.e., mind wandering). Previous studies have investigated the neural correlates of mind wandering during meditation practice through Electroencephalography (EEG) using linear metrics (e.g., oscillatory power). However, their results are not fully consistent. Since the brain is known to be a chaotic/nonlinear system, it is possible that linear metrics cannot fully capture complex dynamics present in the EEG signal. In this study, we assess whether nonlinear EEG signatures can be used to characterize mind wandering during breath focus meditation in novice practitioners. For that purpose, we adopted an experience sampling paradigm in which 25 participants were iteratively interrupted during meditation practice to report whether they were focusing on the breath or thinking about something else. We compared the complexity of EEG signals during mind wandering and breath focus states using three different algorithms: Higuchi’s fractal dimension (HFD), Lempel-Ziv complexity (LZC), and Sample entropy (SampEn). Our results showed that EEG complexity was generally reduced during mind wandering relative to breath focus states. We conclude that EEG complexity metrics are appropriate to disentangle mind wandering from breath focus states in novice meditation practitioners, and therefore, they could be used in future EEG neurofeedback protocols to facilitate meditation practice.