Tópico: Visualizando o cérebro nas situações de saída do corpo

[Luiz Souto]

Brief Report: Visualizing Out-of-Body Experience in the Brain
[Original Articles]
De Ridder, Dirk; Van Laere, Koen; Dupont, Patrick; Menovsky, Tomas; Van de Heyning, Paul.

From the Department of Neurosurgery and Ear, Nose, and Throat, University Hospital Antwerp, Antwerp University, Antwerp, Belgium (D.D.R., T.M., P.V.H.); and the Department of Nuclear Medicine, University Hospital Leuven, Leuven, Belgium (K.V.L., P.D.). Address reprint requests to Dr. De Ridder at the Department of Neurosurgery, University Hospital Antwerp, Wilrijkstraat 10, 2650 Edegem, Belgium, or at dirk.de.ridder@neurosurgery.be.

SummaryAn out-of-body experience was repeatedly elicited during stimulation of the posterior part of the superior temporal gyrus on the right side in a patient in whom electrodes had been implanted to suppress tinnitus. Positron-emission tomographic scanning showed brain activation at the temporoparietal junction - more specifically, at the angular-supramarginal gyrus junction and the superior temporal gyrus-sulcus on the right side. Activation was also noted at the right precuneus and posterior thalamus, extending into the superior vermis. We suggest that activation of these regions is the neural correlate of the disembodiment that is part of the out-of-body experience.

An out-of-body experience is a brief subjective episode in which the self is perceived as being outside the body (disembodiment), with or without the impression of seeing the body from an elevated and distanced visuospatial perspective (autoscopy) [1] (see Glossary). Disembodiment refers to a disrupted sense of spatial unity between self and body, because the self is not experienced as residing within the limits of the body. [2] Thus, disembodiment refers to an abnormal self-location.

Out-of-body experiences differ from depersonalization, in which a subjective experience of unreality and detachment from the self is experienced. Depersonalization is often accompanied by derealization, in which the external world appears strange or unreal. In depersonalization and derealization, a feeling of detachment or separation from surroundings is often noted, but not a feeling of disembodiment or autoscopy. [3]

It has been suggested that out-of-body experiences are the result of a transient failure to integrate the visual, tactile, proprioceptive, and vestibular information that converges at the temporoparietal junction, especially on the right side of the brain. [1] Out-of-body experiences have attracted the most interest when reported by people who have had near-death experiences, but they have also been reported to occur spontaneously in patients with epilepsy or migraine [1] and have been induced by electrical stimulation of the temporoparietal junction on the right side in patients with epilepsy. [4,5]

Case Report
We report the case of a 63-year-old man in whom stimulation with implanted electrodes overlying the temporoparietal junction on the right side as a means of suppressing intractable tinnitus [6] consistently induced out-of-body experiences without autoscopy. Only certain stimulation parameters induced the experiences, which lasted long enough (17 seconds on average) to allow us to conduct a placebo-controlled series of stimulations while positron-emission tomography (PET) was performed. PET data suggested that activation of a small area at the junction of the angular-supramarginal gyrus (a cortical region associated with multisensory integration [1]), combined with activation of a second area in the posterior part of the superior temporal cortex (a region associated with self-perception [7]), elicited the feeling of disembodiment without autoscopy.
(...)

Conclusions regarding the anatomical origins of spontaneous and electrically elicited out-of-body experiences in patients with epilepsy have been questioned because cortical reorganization is known to take place in some of these patients. It has also been suggested that both tinnitus and epilepsy are the result of dysrhythmic thalamocortical oscillations. [14] A subgroup of people with epilepsy undergo progressive brain atrophy accompanied by functional decline, both of which worsen with the duration of epilepsy. [15] For these reasons, it is not clear whether out-of-body experiences might be a normal consequence of coactivation of two areas that do not usually function together or whether they arise only in the presence of pathological brain states such as epilepsy or tinnitus. Studies of depersonalization and derealization have demonstrated that caloric stimulation can induce a feeling of detachment or separation from surroundings both in healthy subjects and in patients with vestibular disorders. [3] However, the symptoms occur spontaneously only in patients with vestibular disorders. [3] It could be hypothesized that a similar mechanism is at work in out-of-body experiences - that is, they may occur spontaneously only in pathologic brains but can be induced in nonpathologic brains.

Our PET data suggest that the experience of disembodiment is mediated by coactivation of a small area at the junction of the angular and supramarginal gyrus and the superior temporal gyrus-sulcus. Activation of the angular and supramarginal gyrus junction alters vestibular-somatosensory integration of body orientation in space. Coactivation of the posterior part of the superior temporal cortex, with its internal map of self-perception, results in altered spatial self-perception. Whether these regions are activated in patients who report disembodiment as part of a near-death experience - and if so, how - is a provocative but unresolved issue.

No potential conflict of interest relevant to this article was reported.

We thank Jay Gunkelman for reviewing an earlier version of the manuscript, and Tim Vancamp for his support..

Glossary

Autoscopy: The impression of seeing one's own body from an elevated and distanced visuospatial perspective.

Depersonalization: The subjective experience of unreality and detachment from the self.

Derealization: The experience of the external world as strange or unreal.

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.

DeRider,Dick; Brief Report: Visualizing Out-of-Body Experience in the Brain
New England Journal of Medicine , Volume 357(18) , November 1, 2007

Um interessante artigo sobre um possível mecanismo para as experiências de "saída do corpo" ; é um relato comum nas situações de quase-morte e os pesquisadores , embora cautelosos em estender o achado para este caso específico, apontam como uma possível explicação para o fenômeno.
Não pude infelizmente traduzir o artigo , e os negritos são meus.