Dying to know the truth: visions of a dying brain, or false memories?
The nature ofmind-brain relationships and the possibility of life-after-death are some of the most profound issues relating to mankind’s place in the universe. Thereport in today’s Lancet by Pim van Lommel and colleagues of near-deathexperiences (NDEs) in survivors of a cardiac arrest provides intriguing datathat are relevant to these issues. Theirs is the second prospective study ofthis type, the first being a smaller-scale study done in Southampton by Parniaand colleagues.1 Both groups of researchers think that theirfindings indicate a need for radical revision of current assumptions about therelationship between consciousness and brain function.
The nature of mind-brain relationships and the possibility of life-after-death are some of the most profound issues relating to mankind’s place in the universe. The report in today’s Lancet by Pim van Lommel and colleagues of near-death experiences (NDEs) in survivors of a cardiac arrest provides intriguing data that are relevant to these issues. Theirs is the second prospective study of this type, the first being a smaller-scale study done in Southampton by Parnia and colleagues.1 Both groups of researchers think that their findings indicate a need for radical revision of current assumptions about the relationship between consciousness and brain function. van Lommel and colleagues ask, “How could a clear consciousness outside one’s body be experienced at the moment that the brain no longer functions during a period of clinical death with flat EEG?”. But the truth is that nobody knows when the NDEs reported by these patients actually occurred. Was it really during the period of flat EEG or might they have occurred as the patients rapidly entered or gradually recovered from that state?
Elsewhere, Parnia and Fenwick have reviewed NDEs during cardiac arrest and have considered the latter possibility.2 They think that such an explanation is unlikely, mainly because of anecdotal reports of patients accurately recalling events that took place during the actual cardiac arrest, apparently during the out-of-body experience (OBE) phase of the NDE. An OBE can be defined as an experience in which a person seems to perceive the world from a location outside the physical body. One such anecdote was reported to van Lommel and colleagues during the pilot phase of their study by a coronary-care-unit nurse. Unfortunately, they do not report whether any attempt was made to corroborate details with the patient. On many previous occasions such attempts at corroboration have revealed that the evidence was not as impressive as it initially seemed.3 Blackmore4 lists several alternative non-paranormal explanations as to why people may sometimes seem to accurately describe events occurring during their NDEs. These include “information available at the time, prior knowledge, fantasy or dreams, lucky guesses, and information from the remaining senses. Then there is selective memory for correct details, incorporation of details learned between the NDE and giving an account of it, and the tendency to tell a good story”.
Having said that, the OBE component of the NDE offers probably the best hope of launching any kind of serious attack on current concepts of the relationship between consciousness and brain function. Parnia and colleagues1 had hidden targets on boards suspended from the ceiling of the wards used in their study, in the hope that if any patient reported an OBE during their cardiac arrest, they would subsequently be able to identify the targets. Unfortunately, none of the four patients who experienced an NDE in the study experienced an OBE as part of the NDE. However, if reports of veridical perception during OBEs were to be forthcoming in future studies, they would represent a very strong challenge to any non-paranormal explanation of the NDE.
van Lommel and colleagues’ report raises the possibility of a new potential artefact in such studies. It seems that at least some NDEs may be the result of false memories, of the mind trying to retrospectively “fill in the gap” after a period of cortical inactivity. The investigators report that, at the 2-year follow-up, four of 37 patients contacted to act as controls (ie, people who had not initially reported an NDE) reported that they had had one. Although these patients represent fewer than 1% of the total sample, they represent over 10% of the 37 patients interviewed with a view to acting as controls. If this subsample is at all representative, it implies that around 30 patients from the sample of 282 who initially denied an NDE would, if they had survived for another 2 years, be claiming that they had had one. van Lommel and colleagues suggest that these patients may have been unwilling or unable to describe their NDEs in the first interview, but no attempt seems to have been made to corroborate these possibilities with the patients themselves. It seems likely that at least some patients, on hearing about other survivors’ NDEs, would start to imagine what it would have been like if they had had the same experience. Recent psychological studies have shown conclusively that simply imagining that one has had experiences that had in fact never been encountered will lead to the development of false memories for those experiences.5, 6, 7 Interestingly, susceptibility to false memories correlates with tendency to dissociate,8, 9 which in turn correlates with the tendency to report NDEs.
Perhaps the switching of classification of patients represents nothing more than changes in definition of NDE at different stages of the study. This possibility may receive some support from the fact that, at the 2-year follow-up, over a third of the 17 patients who had originally reported superficial NDEs were then deemed to not have had NDEs at all. Another possibility is ordinary forgetting. Such problems must be rectified in future studies because their overall effect would be to blur the distinction between NDE and non-NDE-patients. This overlap would make it much more difficult to identify possible physiological and psychological differences between the groups. Nevertheless, the prospective nature of the studies by van Lommel and colleagues and Parnia and colleagues is to be welcomed as a major advance over previous retrospective approaches.
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References
- Parnia, S, Waller, DG, Yeates, R, and Fenwick, P. A qualitative and quantitative study of the incidence, features and aetiology of near death experiences in cardiac arrest survivors. Resuscitation. 2001; 48: 149–156
- Parnia S, Fenwick P. Near death experiences in cardiac arrest: visions of a dying brain or visions of a new science of consciousness? Resuscitation (in press).
- Blackmore, S. Dying to live: science and the near-death experience. Grafton, London; 1993
- Blackmore, S. Out-of-body experiences. in: G Stein (Ed.) The encyclopedia of the paranormal. Prometheus, Amherst, NY; 1996: 480
- Garry, M, Manning, CG, Loftus, EF, and Sherman, SJ. Imagination inflation: imagining a childhood event inflates confidence that it occurred. Psychonomic Bull Rev. 1996; 3: 208–214
- Goff, LM and Roediger, HLM. Imagination inflation: the effects of number of imaginings on recognition and source monitoring. Memory Cognition. 1998; 26: 20–33
- Loftus, EF. Imagining the past. Psychologist. 2001; 14: 584–587
- Heaps, C and Nash, M. Individual differences in imagination inflation. Psychonomic Bull Rev. 1999; 6: 313–318
- Hyman, IE Jr and Billings, FJ. Individual differences and the creation of false childhood memories. Memory. 1999; 6: 1–20
Энергопотребление головного мозга
Головной мозг, составляет около 5% массы тела, потребляет при этом 20% всей производимой энергии. При этом энергопотребление остается практически постоянным независимо от того, чем занят человек, отдыхает он или же решает задачи, требующие серъёзной концентрации внимания.
Вероятнее всего, энергия расходуется на поддержание [энерго-]информационной связи с нашим энтропийным телом.