Mindfulness meditation practitioners often report an increased  awareness of body sensations. Some neuroimaging studies support this claim, revealing that meditators, compared to non-meditators, tend to have denser and more active anterior insulas--a brain region involved in body awareness. This enhanced body awareness linked with meditation may play a significant role in improving emotional self-regulation and stress management.

Humans can be sensitive to sensations arising both spontaneously from within the body and those generated externally, such as being touched. Signal detection theory claims that people differ not only in their sensitivity to touch but also in the strictness of the criteria they use to decide whether they have been touched. Sensitive individuals are better at accurately detecting faint touch stimuli, while those with more lax criteria are more likely to incorrectly report being touched when no stimulus is present.

Prior research shows that meditators exhibit reduced EEG alpha power after being cued to begin a signal detection trial, compared to non-meditators. This reduction likely reflects attentional preparation to receive a stimulus. Lower alpha power during this period has been linked to better performance on signal detection tasks. However, it remains unclear whether this improvement is due to increased sensitivity or more lax reporting criteria.

Mylius et al [Psychophysiology] contrasted the ability of meditators and non-meditators to detect very faint tactile sensations during a signal detection task. They also examined whether variations in electroencephalogram (EEG) alpha wave modulation could account for differences in signal detection accuracy between the two groups.

The researchers compared 31 German expert meditators (average age = 35 years; 61% male; average lifetime meditation hours = 2,628 hours) to 33 German non-meditator controls (average age = 32 years; 67% male). Meditators had a history of meditating ≥ 5 hours per week for at least two years, while controls reported reading books for ≥5 hours per week for at least two years. Participants completed on-line self-report survey of mindfulness (Mindful Attention Awareness Scale or MAAS), body sensory awareness (Multidimensional Assessment of Interoceptive Awareness or MAIA-2), and emotion regulation. 

Participants then completed an in-person laboratory task to determine their threshold for mild electrical stimulation--the intensity accurately detected 50% of the time. They subsequently engaged in a signal detection task. At the start of each trial, a gray disc appeared on a computer screen, serving as a cue that the trial was about to begin. Half the time, the cue was followed by threshold level electrical stimulation delivered to the left index finger; the other half, no stimulation occurred. At the end of each trial, participants indicated whether they perceived a tactile stimulation. Throughout the task, EEG recorded participants’ brain alpha power.

Results indicated that the meditator group scored significantly higher than controls on seven of the eight MAIA-2 subscales (Cohen’s d range = 0.90 to 1.52), indicating greater body awareness. The meditator group also reported significantly less expressive suppression (d = 0.94) and less difficulty describing their feelings (d =.64). MAAS scores did not differ by group. The meditator group was not significantly more sensitive to the tactile stimulus but employed significantly laxer criteria when determining whether a stimulus had occurred (η2 = 0.56).

The meditator group also had lower EEG-based alpha power levels at baseline and a greater drop-off of alpha power after task cueing than controls. Lower alpha power after task cueing was associated with a greater likelihood of reporting a stimulus, whether or not it had occurred. 

The investigators found that while meditators self-reported significantly greater body awareness, they were not more sensitive to faint external tactile stimulation compared to non-meditators. However, meditators exhibited significant differences in baseline and post-cueing alpha power during the signal detection task.

Meditators employed laxer criteria in determining whether a tactile stimulus had occurred. What might “laxer criteria” involve? Perhaps the greater attentional readiness associated with lowered alpha power by cueing led to heightened awareness of tiny spontaneous finger sensations, which were misperceived as the touch stimulus.

Reference:

Mylius, M., Guendelman, S., Iliopoulos, F., Gallese, V., & Kaltwasser, L. (2024). Meditation expertise influences response bias and prestimulus alpha activity in the somatosensory signal detection task. Psychophysiology.

Link to study