Out of body experience v. depersonalization

Ridder DD, Laere KV, Dupont P, et al. Visualizing out-of-body experience in the brain. NEJM 2007; 357:1829-33.

Glossary
autoscopy- the impression of seeing one's own body from an elevated and distanced visuospatial persepctive.

depersonalization-- the subjective experience of unreality and detachment from the self

disembodiment-- an experience in which the self is perceived as being outside the body

out of body experience-- a brief subjective episode of disembodiment, with or without autoscopy.

Out of body experience was repeatedly elicited with stimulation of the posterior STG on the RIGHT in a subject in whom electrodes had been placed to suppress tinnitus. Brain activation on PET scanning occurred on the right at the junction of the SMG and the angular gyrus and the STG gyrus /sulcus on the right. There also was activation in the right precuneus and posterior thalamus extending into the superior vermis.

Such patients may have a transient inability to integrate the visual, tactile, proprioceptive and vestibular information that converges at the site. These events occur in near death experiences, in epilepsy, migraine, and by electrical stimulation of the temperoparietal junction on the right side in epileptics.

The authors note the right SMG processes vestibular information for head and body orientation in space. The area may embody an internal map of self-perception.

In contrast, during depersonalization and derealization, metabolic activity occurs in the inferior parietal cortex (area 7B) so that mislocalization in space is a slightly more dorsal lesion. The anterior cingulum usually coactivates with the angular gyrus, and precuneus during reflective self-awareness (Cavanna AE and Trimble MR. The precuneus: a review of its functional analtomy and behavioral correlates. Brain 2006; 129:564-583). Penfield found patients with floating feelings with stimulation of the right temporoparietal junction, and Blanke et al (Nature 2002; 419:269-270) found the stimulation target for autoscopy was more posterior at the occipital side of the angular gyrus. Caloric stimulation can also produce a feeling of detachment from the suroundings in healthy subjects and those with vestibular disorders (Sang FY et al. 2006; JNNP;77:760-766).
Th authors bring up that epileptics with atrophy might have altered brain connections or coactivation of two areas that are normally not coactivated.

This article concludes with a hypothesis that disembodiment is mediated by the coactivation of the small area at the junction of the angular and SMG and STG/sulcus. Activation of the posterior part of the superior temporal cortex with its map of self perception, results in altered self-perception. They aren't sure if this is what happens in near death experiences.