Traditional Buddhist meditations reduce mismatch negativity in experienced monk- practitioners.

Thousand-year-old Buddhist traditions have developed a wide range of methods for the subjective exploration of consciousness through meditation. Combining their subjective research with the possibilities of modern neuroscience can help us better understand the physiological mechanisms of consciousness. Therefore, we have been guided by specifically Buddhist explanations when studying the physiological mechanisms of altered states of consciousness during Buddhist meditations. In Buddhism, meditations are generally divided into two large categories: (1) one-pointed concentration and (2) analytical meditation. Maintaining both one-pointed concentration and analytical meditation on 'bodhicitta' ("the thought of awakening") and 'emptiness' is a necessary condition for transitioning into tantric practices. Tantric practices involve sophisticated visualizations of Buddhist deities, the 'energy structure' of the human body, and the visualization of the stage-by-stage process of dying accompanied with the dissolution of body elements. According to Buddhism, these meditations are characterized by the gradual withdrawal from "gross levels" of consciousness associated with the five senses. From a psychophysiological perspective, this withdrawal of sensory consciousness can be considered as the decrease of sensory stimuli recognition and attentional disengagement from the external world. We concentrated on how considered meditations affect sensory and cognitive processing of external stimuli. Auditory event-related potentials (ERPs) in the passive oddball paradigm were studied both during meditations and in a controlled state of relaxed wakefulness. It was shown with a group of 115 Buddhist monks that during meditation, mismatch negativity amplitudes, amplitudes of N1 and P2 components of ERPs to deviant stimuli, and the amplitudes of the P3a component to novel stimuli all decrease. These outcomes suggest that the considered Buddhist meditations, compared to the control state of relaxed wakefulness, are accompanied by a decrease in physiological processes responsible for maintaining attention on the outside world and recognizing changes in the stream of sensory stimuli.

A nonparametric method for the segmentation of the EEG.

A new method for segmentation of the EEG, based on a nonparametric statistical analysis, is proposed. A nonparametric approach was chosen because it minimises the need for a priori information about a signal. The method provides detection of change-points (quasi-stationary segments' boundaries) in almost any EEG characteristic for a given level of false alarm probability. The method was applied to 8-channels spontaneous EEG recordings obtained from 12 subjects in eyes closed and eyes open conditions to detect rapid fluctuations of the alpha rhythm power. After preliminary adjustment of false alarm probability values all the recordings were analysed in unsupervised regime with the same parameters. From 15 to 119 change-points were found per minute and EEG channel. Automatically detected change-points were in good correspondence with visual estimation of the instants of change in alpha activity.