Changes in cortical activity during altered state of consciousness: study of meditation by high resolution EEG

Abstract

The specific features of the topology of spectral powers and coherent interregional interrelation- ships in the narrow, individually determined δ -, θ -, α 1 -, α 2 - , and α 3 -frequency bands were studied by means of high-resolution EEG (62 channels) in novice and experienced meditators (NMs and EMs) at rest and under the conditions of generation of an altered state of consciousness characterized by inactivation of cognitive activity and the occurrence of a positive emotional experience of happiness. EMs in the meditation-free state were found to be characterized by a shift in the values of the individual α frequency to a lower-frequency region of the spectrum, along with higher, compared to NMs, θ -, α 1 -, α 2 - , and α 3 -band power values, which probably reflects the cumulative character of the influence of long-term meditative practice. The effective achievement of altered states of consciousness in EMs was associated with an increase in the local θ - and α 1 powers in the anterior cortical areas, as well as long-distance coherence between the prefrontal and posterior associative cor- tex with the formation of a center of gravity in the left prefrontal region (lead AF 3 ). According to the data of the correlation analysis of the EEG power values and the data of subjective scaling of the meditation state, the θ - power values were positively associated with positive emotional experiences and negatively associated with the level of mental activity. The results of this study are consistent with current concepts that the θ and α activities in narrow frequency bands reflect the activity of multifunctional neuronal networks selectively associated with processes of cognitive and affective activity.