The main purpose of the research outlined here was to develop a tool for monitoring brain state changes during EEG recording sessions- a state monitoring device (SMD). A major success of this project was the development of an online device (SMD) that allows monitoring of brain state changes during EEG recording sessions. In future, this tool will serve as an instrument for detecting events of state changes immediately after their occurrence in a recording session and thus will enable the researcher to associate those events with the subjective experience.
For the first time, we are able to follow internal states of consciousness in people who are in altered states or higher states of consciousness, in experienced and also novice meditators during their spiritual practice.
Summary of Methods:
The visibility of such state changes during meditation sessions has been shown in an offline analysis with more than 30 experienced meditators from different eastern and western traditions. During the first half of the project neurophysiological data from 33 experienced meditators was analyzed in order to find parameters that tracked appropriate meaningful state changes in meditators.
After the overall analysis a time resolved visualization of all those parameter was programmed in order to provide an as good as possible inspection of the state changes during the sessions.
The button presses of the meditators and their subjective reports were then correlated with the visualized parameters during the 10-30 seconds before the button press. The final aim of the project was to be able to view and realize such a state change already during the meditation session and immediately ask the meditator about his or her experience.
In this study, 33 experienced spiritual practitioners aged 26-65 years (mean 46 years, 7 female, 19 male) from various spiritual backgrounds were measured with EEG and peripheral measures. The inclusion criteria were that they should carry out a meditative spiritual practice on a regular basis and/or should be used to the practice of meditation. 9/26 of them were meditating every day, 11 of them more than once a week and 7 of them only one a week or less. The participants reported to spend between 15 and 120 minutes for each meditation session. They had between 2 and 35 years of meditation experience (mean 15 years). With this information we could calculate the total experience in meditation which was between 12 and 13697 hours (mean 3357 hours). The participants also were inhomogeneously associated to different kinds of spiritual traditions such as Zen-Buddhism (10), Qi-Gong (4), western contemplative methods (7), and spiritists or mediumistic practitioners (5). Some of them were also into spiritual healing and Shamanism. Six participants were professional Buddhist monks in Japan.
A meta-analytical approach of merging the t-values of all subjects showed a highly significant decrease of frontal and prefrontal Beta and Gamma activity while the oscillatory Gamma was highly significantly increased with up to three times its resting state power amplitude (see Figure 1).
Figure 1. Band power analysis of the meditation session referenced to the corresponding individual resting condition (eyes open or eyes closed).
Notice the large increase in Gamma activity over central/frontal areas.
We identified the following parameters that reveal state transitions of the brain during meditation:
(1) Decrease in Delta (1-3.5 Hz) and Theta (4-7.5 Hz) activity in central, parietal, and occipital areas of the brain.
(2) Significant increase in Gamma band activity in frontal brain areas.
(3) Slight decrease in low-Gamma (25.5-47 Hz) coherence in frontal-parietal areas.
(4) Shift of occipital Theta activity towards the left hemisphere.
(5) Gamma activity was highly increased up to three times its resting state power amplitude.
(6) Gamma band power and oscillatory Gamma seem to be completely decoupled during meditation.
(7) Beta and Gamma activity shift to the right hemisphere in central and temporal regions.
Our explorative studies led to us devloping a list of definitions of the most common meaningful EEG events, in order to allow for our state monitoring device to differentiate between the differing types of neural responses, or states of consciousness (SOC). These event are described in table below.
Brain-Computer Interfaces and State Tracking:
In recent years, the field of brain-computer interfaces (BCIs) has grown rapidly Essentially, a BCI can be thought of as a neurofeedback system that does not only provide information about a certain parameter of the brain but additionally translates the neuronal signal into an output signal that allows for control of a neuroprosthesis, a spelling interface, etc.. Therefore, a BCI is an enhanced neurofeedback system. Similarly, for tracking of state changes in the brain it is not sufficient to feed back or monitor a certain brain parameter, only. State tracking requires a concerted display of all relevant brain parameters because a brain state in our terms requires as much information as possible to be discriminable from other states.
Visualizing specific neural events:
The first challenge in detecting brain state changes during a meditation session was to be able to view the entire session in one graph. This means, a visualization technique had to be found that allows for displaying most of the parameters and their changes over time at once. One solution is a colour graph as shown below. Figure 3 displays examples of specific events, some where marked by the practitioner with a button press and later associated with the subjective experience reported after the session.
Figure 3. Changes in oscillatory Gamma band activity during a meditation session
in which the practitioner reported of different levels of higher states of consciousness
The Real-time State Monitoring Device:
With the knowledge about the nature of the state changes occurring during meditative states in electrophysiological recordings a Real-time State Monitoring Device (SMD) could be programmed. The system is based on the technology of a brain-computer interface (BCI) as normally BCIs allow for data acquisition, data processing and feedback or display of processing results in real-time. For this project the existing brain-computer interface Thought-Translation-Device (TTD) (Birbaumer et al., 1999; Hinterberger et al., 2003; 2005) was modified for use during meditation.
Figure 4. Displays the real-time state monitoring window which is produced by the State Monitoring Device in the TTD. Seven frequency bands are displayed namely delta, theta, alpha, beta1, beta2, gamma1, and gamma2 from bottom to top. The topographic views on the left show the current spatial distribution of the corresponding normalized band power and is updated every 0.5 seconds. Each of the color maps on the right contains the 64 channels of EEG in the vertical dimension while in the horizontal dimension the user can overlook a time span of about 10 minutes in this setting. Blue areas indicate a decreased activity while yellow/red indicates an increase.
This figure shows a screen of the State Monitoring Device showing the data of the first meditation session. At around 8:25 min the meditator decided to release thinking and enter the state of pure being which was visible in an immediate increase of gamma activity.
This research has shown that, in 33 highly experienced meditators, the state monitoring device was successful in identifying various state changes in the physiology associated with changes in experience. With further work this may be used to allow experienced meditators to intensify their experiences by giving real-time neural feedback, or allow novice meditators to develop there skills at a more rapid pace. This will allow therapists and teachers in meditation and clinical hypnosis to trace states of consciousness in order to guide their clients in the process. The aim of future research using the techniques outlined above is to use the system to drive a feedback environment that reacts to changes in brain states to further assist in altering states of consciousness.