X-Message-Number: 19324 From: "Ben Best" <> Subject: Brain electrical activity and personal identity Date: Fri, 21 Jun 2002 03:35:47 -0700 "Toby Christensen" <> wrote: > As you are well aware, when a person dies the electrical > activity in their brain ceases. What method do you see as > being able to "start up" a person's brain once their > freezing/mortal wounds etc. have been fixed? Other have commented on this point, but I want to add my two cents -- some repetition but some forceful addition, I hope. I have already addressed the question in my essay "Cryonics: The Issues", which is on my website at: http://www.benbest.com/cryonics/cryiss.html There I say: > Some people worry that the cessation of electrical > activity during cryopreservation would mean a loss > of personal identity & memory. Although immediate >(short-term) memories would probably be lost, there is > ample reason to believe that identity & long-term > memory is encoded in synapses and in the connections > between neurons -- which would be cryopreserved. Dogs > have been cooled to low temperature in a bloodless > state with no evident electrical activity, yet > have demonstrated memory upon recovery. Similarly, > humans reduced to a state of no detectable electrical > activity by drugs have demonstrated recovery of > memory & identity. Someone has criticized my view by questioning the experimental evidence in saying that just because no electrical activity has been detected does not mean that no electrical activity existed. This person clearly believes that identity and memory lies in the electical activity itself -- as if the electricity itself is a kind of "life". But if you light a candle, the nature of the flame is a product of the nature of the wax and the wick -- snuff the candle. Re-light the candle and the flame will be the same. Similarly, if the heart stops and is restarted (and has not been damaged) the heart will resume operation, contracting in response to the waves of electrical impulses in precisely the same manner as it did before and producing the exact same result because the patterns of electrical activity and the effects of electrical activity are entirely determined by the structure of the fibers carrying the electrical impulses and their connections. Likewise, if the axons, dendrites and synapses -- including the strength of synaptic connections -- in the brain are not destroyed, then memory and personal identity should be maintained. There is ample evidence that memory is encoded by modification of synaptic strengths -- although the physical connections by the cables (axons and dendrites) are obviously an important part of this. Thus, re-starting the electical signals should re-activate our memories. Obviously we do are not remembering every piece of knowledge in our brains at every moment of our lives. What we are remembering at any particular moment is a function of which neurons & synapses are being activated at that moment. During non-REM (non-dreaming) portions of our sleep-cycle there is diminished electrical activity of the brain due to reduced input from the reticular activating system (RAS). The RAS is analogous to the pacemaker of the heart --generating electrical signals to activate brain function, just as the heart pacemaker generates electrical signals to activate heart function. To repeat, what those functions are depend upon the connections in the heart & brain, not the instigation of signals. The RAS is even less active in unconsciousness and coma -- and if coma is deep enough there may not even be enough electrical activity in the medulla to keep the heart functioning, much less the brain, and death will ensue. To imagine that the RAS is a source of identity is to confuse the nature of consciousness with the distinction between being conscious or unconsious. It is a property of the cells in the pacemaker of the heart that they initiate electrical depolarizations at regular intervals. I believe that the cells in the RAS have a similar inherent tendency to self-initiated electrical depolarization. Thus, restoring the health and functionality of RAS cells should restore the electrical activity of the brain. And restoring the neurons, synapses, axons, dendrites and the supporting glia in the cerebral cortex, basal ganglia, etc., should restore the critical features of consciousness -- memory and personal identity. -- Ben Best Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=19324