Any Freudian puns about the unconscious mind aside, the need to find the boundary between consciousness and unconsciousness can be made eminently clear when one considers the possibility of undergoing surgery while not fully unconscious. Such prospect may indeed sound like the stuff of horror movies, but physicians estimate that 1 in 1,000 patients have memories even while under general anesthesia. Some have even reported full awareness of the pain and terror.

As shown by any other advancements in medical technology, it is insufficient to merely depend on the experiences and expertise of doctors if they are not accompanied by accurate and precise measuring and analyzing techniques. To solve not only the problem of intraoperative awareness but also broaden the understanding of the mind, a quantifiable marker regarding the boundaries of consciousness needs to be identified.

In response, collaborative research conducted by Professors Seunghwan Kim and Woo-Sung Jung from the Department of Physics at Pohang University of Science and Technology et al. has successfully quantified the neuroscience mechanism of loss and recovery of consciousness during general anesthesia by analyzing the interaction of multichannel electroencephalography (EEG). This remarkable achievement has been published in the world-renowned Human Brain Mapping.

The team introduced phase-lag entropy (PLE), a measure of the diversity of temporal patterns in the phase relationship between two signals, to quantify the phase change between EEG channels on 96 patients and found that the patients’ EEG decreased markedly with the entropy indicator after anesthesia. By analyzing the various rhythms of EEG in patients under general anesthesia, the team was able to successfully quantify the depth and level of consciousness during the process of recovery from anesthesia. Doing so, the team discovered that the connection from conventional methodology of brain research to anesthesia depth shows that consciousness disappears after anesthesia more accurately than the first known indicator.

Professor Kim commented on this achievement by saying that “from basic research to application development and clinical development, we opened a new medical market with domestic equipment based on our technology. We will continue to challenge the mysteries of the brain through subsequent research.”