How many neurons need to survive for cryonics to work?
On this page a calculation is attempted to determine how many neurons need to survive for cryonics to work. The flaw in this approach should be obvious when the author writes :
According to The Stroke Association, a stroke is a brain injury with effects which may include difficulty thinking, learning, concentrating, remembering, making decisions, reasoning and planning. Rehabilitation consists of relearning skills, not having your brain recover naturally.
So a reasonable position is that the cryonic chilling process should cause less damage to the brain than a stroke
The debilitating effects of a stroke are the result of the (delayed) neuronal death that follows an ischemic insult to the brain. In cryonics, biochemical or freezing damage to cells does not necessarily produce irreversible cell death because damaged cells are stabilized by cold temperatures. As such, morphological preservation of brain cells can co-exist with loss of viability. Therefore, securing viability of brain cells is a sufficient but not a necessary condition for resuscitation of cryonics patients. Future cell repair technologies are assumed to infer the original viable state of the cells from their morphological properties.
This does not mean that conventional stroke research does not have any relevance for evaluating the technical feasibility of cryonics. Extensive delays between the pronouncement of legal death and the start of cryonics procedures could alter the structural properties of cells to such a degree that meaningful resuscitation is even problematic with advanced nanomedical cell repair technologies. This is one of the reasons why Alcor complements the cryopreservation process with stabilization procedures to secure viability of the brain after pronouncement of legal death.