Decapitation in Rats: Latency to Unconsciousness and the ‘Wave of Death’
Clementina M. van. Rijn mail, et al.
PLOS ONE. January 27, 2011
In awake rats it lasts takes about 17 seconds before the power of the EEG is iso-electric.
Since it is not known how the power of the EEG correlates with the level of consciousness, in drug free subjects, iso-electricity forms a solid base to regard the animal as completely unconscious.
However, the question arises whether the degree of consciousness at an earlier time is already so low that perception of pain and distress is already totally eliminated.
the power in the cognitive band (13–100 Hz) of the sleep state is still 78%, (SEM 4.4%) of that during waking.
Since sleep is not deeply unconscious, it seems save to take a lower value, thus to assume that the animals are unconscious at a power decrease of the cognitive band of 50%.
This point is reached in 3.7 seconds.
The EEG of an anesthetized subject is very different from that of an unmedicated state.
Therefore it is quite surprising that the post-decapitation EEG, and its power, of the anesthetized group are almost the same as that of the awake group.
One interpretation is that the resulting power of the EEG in the awake animals is not well indicative of consciousness and distress, since the same activity is present in the EEG of non-conscious anesthetized animals.
On the other hand, the resemblance of the power of the post decapitation EEG in both groups might also imply that the animal’s consciousness is briefly enhanced immediately after the neck cut.
The interpretation might be that the cut is such a powerful arousal stimulus, that even anesthetized animals regain consciousness.
A relatively long time after cutting the neck, when iso-electricity is already present in the EEG for a considerable time, a large amplitude positive-negative-positive wave follows at approximately 50 seconds after decapitation of rats of the awake group.
In the anesthetized rats this wave is also present but comes later, at about 80 seconds after the neck cut.
it seems that it takes nearly one minute for neurons to loose their membrane potentials.
this paper is cited by:
Death rattle of a decapitated brain
09 February 2011
New Scientist, issue 2799, pp: 8-9
NewScientist also cites:
Surges of electroencephalogram activity at the time of death: a case series.
J Palliat Med. 2009 Dec;12(12):1095-100.
increase in electrical activity occurred when there was no discernible blood pressure
Successful resuscitation after prolonged periods of cardiac arrest: A new field in cardiac surgery
The Journal of Thoracic and Cardiovascular Surgery. 139(5):1325–1332.e2, May 2010
Reply to Chawla and Seneff: Near-death electrical brain activity in humans and animals requires additional studies
Jimo Borjigin, et al.
PNAS. October 29, 2013, vol. 110 no. 44
the details of the algorithm used to generate Bispectral Index (BIS) values are proprietary, and therefore it is currently impossible to make a direct comparison of our study with those using the BIS monitor.