Title : An ERP study during meditation
Over the past 10-15 years, a huge amount of works on the study of meditation has been accumulated. A number of scientists acknowledge that voluntary control of attention plays a key role in meditation practices. And this "high-level" voluntary attention processes during meditation can affect on early, involuntary "low-level" processes of attention (e.g., awareness of an external world) (Biedermann et al., 2016). We explore these processes for Buddhist meditation practices (Analytical and Single-pointed meditations). The study involved 81 right-handed subjects (monks from Buddhist monasteries). The registration of an electroencephalogram (EEG) was performed with 19 head electrodes, two electrodes were placed on mastoids (M1, M2), and a reference electrode was placed on the tip of the nose. The recording was carried out by Mitsar-EEG computer electroencephalograph monopolarly, a sampling frequency - 500 Hz. Monks performed a three-stimulus test in a passive oddball paradigm during meditation and in a control state - relaxed wakefulness. Three types of auditory stimuli were presented: standard stimulus - 1000 Hz, probability of presenting - 0.8, deviant stimulus - 1300Hz, probability of presenting - 0.1, new complex stimulus - a sequence of tones with frequency of 500, 1000, 1500, 2000, 2500 Hz, probability of presenting - 0.1. A total of 2000 stimulus were presented. In order to correct cardiogram artifacts, blinking, and eye movement in raw EEG records the Independent Component Method (ICA) was used. Statistical analysis of Anova was used with the factors: State (meditation/control), Zone (6 EEG electrodes - F3, Fz, F4, C3, Cz, C4). Differences were considered significant at a probability level of p <0.05.
Comparison of the ERP during meditation and in a control state demonstrated that the amplitude of the N1 component decreased in response to a deviant stimulus during meditation. During meditation the amplitude of mismatch negativity (MMN) was also decreased. Our data are partially agreed with literature data. For example, a similar decrease in the amplitude of N1 component in response to a deviant stimulus was shown during meditation (Biedermann et al., 2016). At the same time, there are basically reported an increase of MMN amplitude during meditation in literature (Srinivasan, Baijal 2007, Braboszcz 2012, Biedermann et al., 2016, Fucci et al., 2018). But the experimental conditions in these studies have a number of significant differences from our studies (other control state, other types of meditation, studies only after, but not during meditation). Therefore, our MMN-results are not fully comparable with the literature. N1 component reflects the early processing of the acoustic characteristics of the stimulus (Näätänen & Picton, 1987). Mismatch negativity (MMN) is assumed to reflect a deviation of stimulus characteristics from those which are recorded in auditory memory (Näätänen et al., 1978). So, our data may indicate that voluntary immersion in a state of Buddhist meditations was accompanied by a decrease in the automatic discriminating abilities of the auditory cortex.