Inner body experience
12 September 2006
The neuroscientific foundation of the hitherto largely neglected phenomena of out-of-body experiences.
Embodiment, the sense of being localized within one’s physical body, is a fundamental aspect of the self. What we take for granted in our day-to-day lives as our identity/self located within our bodies is actually an ability that appears to require active cerebral mediation . Our development of self is linked to our identification of our internal bodies against other bodies and the outside world. For some individuals this unity can become violated, and they transiently experience a reduplication of the self (autoscopy). One such form of autoscopy is the out-of-body experience, during which the self is detached from the physical body, and the world and own body is seen from a commonly elevated spatial position.
Rather than treating out-of-body experiences from a mystical or supernatural perspective, Dr Mohr and her colleagues show in their experiments that two distinct areas towards the rear of the brain might control the ability to both locate oneself within the body (embodied self location) and project oneself mentally to another body position in space (disembodied self location). The latter condition resembles phenomenologically the out-of-body experience. Simply speaking, participants are shown front-facing and back-facing figures of a human figure on a computer screen. Participants are required to take mentally the position of the depicted figure.
The neuroscientific foundation of out-of body experiences
In what is called an own-body transformation task (OBT-task), participants imagine themselves in the position and orientation of the human figures, and thus took a disembodied spatial position. In the mirror task (MIR-task), on the other hand, the participants imagine that that the human figure is a self-reflection of themselves in a mirror, and thus, imagine to remain in their own physical body boundaries (embodied spatial position).
While participants performed this behavioural task, brain activity was recorded in the millisecond range using Electroencephalography (EEG) recording. Electrodes are placed on the scalp of the participants, and task-related brain activity can be measured as the voltage difference between task conditions over time. The research group was thus able to determine when and which parts of the brain distinguish between the two tasks.
The results indicated that two distinct time periods between 250 ms and 450 ms after stimulus presentation were related to the two tasks. The earlier time period related to the MIR task, and the brain activation was localized to the left extrastriate body area (EBA). The later time period related to the OBT task, and the brain activation was localized to the right temporo-parietal junction (TBJ), and the left EBA. All brain areas lie towards the posterior part of the brain. In their second experiment, the same tasks were performed, but participants performed the OBT and MIR task in a sitting and lying body position. Apart from the replication of the results obtained from the first study, the study group also found that body position modulated the brain activity of the early time period dedicated to the MIR task This specific brain activity lasted longer when participants were in the sitting than supine position.
The left EBA could be the area which enables humans to locate the self within the body
To summarize, the left EBA could be the area which enables humans to locate the self within the body, while disembodied self-location – the mental projection of the self to another spatial position – activates both the right section of the EBA and the TBJ. This suggests that these two areas are working in tandem in order to allow us to both think of ourselves as inside our bodies and to imagine ourselves as outside our bodies. For example, such brain activities might enable a young boy to imagine himself as England’s football captain, scoring the winning goal. Also, a disproportionate amount of activity from the right TBJ may facilitate out-of-body experiences. These areas of the brain not only enable us to embody the self, but they work together for imagining and coding our bodies in a more general way. Presumably, we would find simple tasks such as performing new motor skills very difficult if we could not firstly imagine ourselves performing it, and also to take the position of another person required for social skills such as empathy. .
Research into the inner workings of the brain is still in its relative infancy, with it proving to be far more complex than any computer. Dr Mohr’s research can go a long way towards understanding both how the individual self is constructed through our bodies inside our brains and the neural processes which allow it to remain there.