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Long-term Vipassana meditators sat in meditation vs. a control (instructed mind wandering) states for 25 min, electroencephalography (EEG) was recorded and condition order counterbalanced. For the last 4 min, a three-stimulus auditory oddball series was presented during both meditation and control periods through headphones and no task imposed. Time-frequency analysis demonstrated that meditation relative to the control condition evinced decreased evoked delta (2–4 Hz) power to distracter stimuli concomitantly with a greater event-related reduction of late (500–900 ms) alpha-1 (8–10 Hz) activity, which indexed altered dynamics of attentional engagement to distracters. Additionally, standard stimuli were associated with increased early event-related alpha phase synchrony (inter-trial coherence) and evoked theta (4–8 Hz) phase synchrony, suggesting enhanced processing of the habituated standard background stimuli. Finally, during meditation, there was a greater differential early-evoked gamma power to the different stimulus classes. Correlation analysis indicated that this effect stemmed from a meditation state-related increase in early distracter-evoked gamma power and phase synchrony specific to longer-term expert practitioners. The findings suggest that Vipassana meditation evokes a brain state of enhanced perceptual clarity and decreased automated reactivity.
Practitioners understand “meditation,” or mental training, to be a process of familiarization with one's own mental life leading to long-lasting changes in cognition and emotion. Little is known about this process and its impact on the brain. Here we find that long-term Buddhist practitioners self-induce sustained electroencephalographic high-amplitude gamma-band oscillations and phase-synchrony during meditation. These electroencephalogram patterns differ from those of controls, in particular over lateral frontoparietal electrodes. In addition, the ratio of gamma-band activity (25-42 Hz) to slow oscillatory activity (4-13 Hz) is initially higher in the resting baseline before meditation for the practitioners than the controls over medial frontoparietal electrodes. This difference increases sharply during meditation over most of the scalp electrodes and remains higher than the initial baseline in the postmeditation baseline. These data suggest that mental training involves temporal integrative mechanisms and may induce short-term and long-term neural changes.
Transcendental Meditation (TM®) is derived from ancient yogic teachings. Both short- and long-term physiological correlates of TM® practice have been studied. EEG effects include increased alpha, theta, and gamma frequencies and increased coherence and synchrony. Neuronal hypersynchrony is also a cardinal feature of epilepsy, and subjective psychic symptoms, apnea, and myoclonic jerking are characteristic of both epileptic seizures and meditative states. Clinical vignettes have highlighted the potential risk of human kindling from repetitive meditation in persons practicing TM®, but clinical studies of similar techniques suggest that meditation may also be a potential antiepileptic therapy. Future clinical studies of meditating subjects using video/EEG monitoring are warranted to determine whether behavioral phenomena have an underlying epileptic basis, and prospective clinical trials of TM® in subjects with well-delineated epilepsy syndromes are necessary to establish the safety of this technique and its potential efficacy for seizure reduction and improvement of quality of life.