Decreased electrophysiological activity represents the conscious state of emptiness in meditation

Thilo Hinterberger,Tsutomu Kamei,Stephanie Schmidt,Harald Walach

doi:10.3389/fpsyg.2014.00099

Thilo Hinterberger, Tsutomu Kamei + Show 2 more

Open Access

https://doi.org/10.3389/fpsyg.2014.00099

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Abstract

Many neuroscientific theories explain consciousness with higher order information processing corresponding to an activation of specific brain areas and processes. In contrast, most forms of meditation ask for a down-regulation of certain mental processing activities while remaining fully conscious. To identify the physiological properties of conscious states with decreased mental and cognitive processing, the electrical brain activity (64 channels of EEG) of 50 participants of various meditation proficiencies was measured during distinct and idiosyncratic meditative tasks. The tasks comprised a wakeful “thoughtless emptiness (TE),” a “focused attention,” and an “open monitoring” task asking for mindful presence in the moment and in the environment without attachment to distracting thoughts. Our analysis mainly focused on 30 highly experienced meditators with at least 5 years and 1000 h of meditation experience. Spectral EEG power comparisons of the TE state with the resting state or other forms of meditation showed decreased activities in specific frequency bands. In contrast to a focused attention task the TE task showed significant central and parietal gamma decreases (p < 0.05). Compared to open monitoring TE expressed decreased alpha and beta amplitudes, mainly in parietal areas (p < 0.01). TE presented significantly less delta (p < 0.001) and theta (p < 0.05) waves than a wakeful closed eyes resting condition. A group of participants with none or little meditation practice did not present those differences significantly. Our findings indicate that a conscious state of TE reached by experienced meditators is characterized by reduced high-frequency brain processing with simultaneous reduction of the low frequencies. This suggests that such a state of meditative conscious awareness might be different from higher cognitive and mentally focused states but also from states of sleep and drowsiness.

Highlights

Meditation practices include a variety of different mental states or states of consciousness which are expressed through diverse EEG patterns, largely influenced by individual situational factors, observed meditation style and previous meditation experience
Theta increases were associated with arousal and attention (O’Keefe, 1993; Klimesch, 1999), decreases in theta power have been found in motor tasks or imagined motor tasks, or more generally tasks requiring no input from the environment (Autret et al, 1985; Hansen et al, 1993; Weiss et al, 1995)
A very similar picture could be seen for experienced meditators who were asked to enter a state of thoughtless emptiness (TE)

Summary

Introduction

Meditation practices include a variety of different mental states or states of consciousness which are expressed through diverse EEG (electroencephalography) patterns, largely influenced by individual situational factors, observed meditation style and previous meditation experience. Lutz et al distinguished between two modes of meditation, the focused attention, and open monitoring (Lutz et al, 2008). They later described the practice of non-referential compassion as related to open monitoring but different with regard to the mental content, possibly representing a third category (Lutz et al, 2007). All those concepts regard meditation as an engaged process requiring specific mental processes to be highly active. Taking a look at common instructions for entering meditation we find that

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