Increased Entropy of Gamma Oscillations in the Frontal Region during Meditation G. Pradeep Kumar, Member, IEEE, Kanishka Sharma, A. G. Ramakrishnan, Senior Member, IEEE and A. Adarsh Abstract— Meditation practices are considered mental train- ing and have increasingly received attention from the scientific community due to their potential psychological and physical health benefits. We compared the EEG data recorded from long-term rajayoga practitioners during different meditative and non-meditative periods. Minimum variance modified fuzzy entropy (MVMFE) is computed for each EEG band for all channels of a given lobe. The means across all the channel entropy values were obtained and compared during meditative and non-meditative states. Meditators showed higher frontal en- tropy in the lower gamma band (25-45Hz) during the meditative states. Independent component analysis was applied to ensure that muscle or eye artifacts did not contribute to the gamma activity. Our results extend previous findings on the changes in entropy observed in long-term meditators during rajayoga practice. Gamma band in EEG is implicated in cognitive processes requiring high-level processing such as attention, learning, memory control, and retrieval. Gamma activity is also suggested as a potential biomarker for therapeutic progress in patients with clinical depression. Based on our findings, there is an excellent possibility to utilize the practice of meditation as a training tool to strengthen the neural circuits, where age-related degeneration is making its pathological impact. I. I NTRODUCTION Over the last decade, the volume of scientific publications on studies related to meditation has dramatically increased [1]. Neuroscientists are investigating the changes in emotion regulation and cognition due to mental practices like medi- tation. Psychotherapists are also interested in improvements in interpersonal relationships, and personal development [2]. The entropic brain hypothesis proposes that the level of conscious states can be indexed with entropy, with increased entropy of brain activity relating to the psychedelic state [3]. High entropy is associated with uncertainty leading to low predictability, which is a result of subjective experiences during meditation, which is beyond the scope of ordinary conscious wakefulness [4], [5]. The hypothesis supports the increase in the entropy during meditation that the long- term practice of meditation is associated with an increased repertoire of experiences which are subjective [6], [7]. Consistent differences were found in the prefrontal cortex and regions involved in body awareness in meditators as compared to controls [8]. Permutation entropy and fractal All the authors are with the MILE Laboratory, Department of Electrical Engineering, Indian Institute of Science, Bangalore 560012, India, pradeepkg@iisc.ac.in, kanishkas@iisc.ac.in, agr@iisc.ac.in, adarsha@iisc.ac.in dimension were used to analyze two types of meditation, and it was found that permutation entropy was advantageous over fractal dimension [9]. Decrease of non-linear dimen- sional complexity in midline frontal and central regions was observed during Sahaja yoga meditation as compared to rest condition [10]. Neuroimaging study on rajayoga practitioners has shown enhanced white matter integrity in corpus callosum segments as compared to controls [11]. Frequency components around ’40 Hz’ termed as gamma band are considered to be a vital characteristic of the brain activation during meditation [12]. It has been hypothesized that the role of gamma-band is prominent in the ’binding problem’ defined as the binding of independent neural assem- blies resulting in the integration of information processing for unified conscious experience [13]. A study of advanced meditators on four different meditations revealed that the source of gamma-band activity was in the anterior regions of the brain during meditation [14]. Another study of advanced practitioners has indicated an increase in the gamma band activity supporting the higher attentional capacities [15]. The objective of this study is to examine whether there exists a consistent difference in entropy in the EEG activ- ity of rajayoga practitioners between meditative and non- meditative states. It has been observed that the increase in entropy during meditation was significant in frontal and centroparietal regions [16]. This analysis is now extended to bandwise computation in the present work. A. Rajayoga practice and present study Rajayoga meditation is a practice reported to be based on contemplation on the supreme soul and thus may in- volve more metaphysical components. The present study investigates entropy changes during the following two types of rajayoga practices: peaceful soul consciousness medita- tion(PM) and angelic meditation (AM). II. EXPERIMENTAL PROCEDURE This work is a continuation of the analysis reported in our previous publication [16]. A. Participants Fourteen long-term meditators (one female) with mean age and standard deviation of 42 ± 5 years, with an average experience and standard deviation of 23 ± 5 years, were recruited for the study. The experiments were carried out at the Brahma Kumaris headquarters, Mount Abu, India. 2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) Oct 31 - Nov 4, 2021. Virtual Conference 978-1-7281-1178-0/21/$31.00 ©2021 IEEE 787