The Impact of Meditation on Body Awareness: Prestimulus Alpha Activity
Modulates Response Bias in a Somatosensory Signal Detection Task
The effects of mindfulness on body awareness and interoception have been proposed as potential mechanisms for its salutary effects. However, research investigating the relationship between mindfulness and body awareness using psychophysical measures is limited. In this study, we compared 31 expert meditators with 33 matched controls on somatosensory accuracy using a somatosensory signal detection task (SSDT) alongside interoception self-report instruments. Our main hypothesis was that meditators would show increased accuracy within the SSDT, indicating higher somatosensory accuracy (body awareness) and that this would be accompanied by neural correlates of increased alpha modulation over the somatosensory cortex as measured through EEG. Participants were asked to detect a near-threshold tactile sensation, which was combined with a non-informative light in 50% of the cases. Associations between prestimulus alpha activity and responses were analysed on a trial-by-trial basis. Contrary to our expectation, instead of an increase in accuracy, we observed a decrease in the decision threshold in meditators, while we found a decrease in prestimulus alpha power in meditators. A trial-by-trial analysis revealed a negative relationship between prestimulus alpha activity and the report of touch. Meditators self-reported higher interoceptive abilities compared to readers. These findings suggest that lower prestimulus alpha activity may have increased the probability of reporting touch within the SSDT, providing a potential mechanism for the increase in response rate in meditators. Our study indicates that meditation practice alters body awareness as shown by modulated prestimulus alpha activity, potentially decreasing the filter function over the somatosensory cortex.