Greetings, I was wondering how long a human brain can retain its information after death. If an individual dies, by the definition of brain death, how long can the cells retain most information before they begin to deteriorate. If the brain is preserved in embalming fluid, can it still retain the same synaptic connections and memories? 

If in the future, we posses the technology to completely rebuild bodies or rejuvenate dead cells, even ones that have been preserved, I was curious if the same information stored in the brain could also be brought back. Do the preservatives used now cause cellular damage and information loss?

Thank You,

Ethan Nino

Interesting question! I'm not sure about the workings of preservatives (I'm sure there would be some kind of tissue damage that would be significant), but assuming the brain cells and their connections were perfectly preserved, it depends on how the brain stores information when it's alive. It's a bit more complicated than juststoring information in connections between cells - there's a lot of stuff going on chemically that you may never be able to retrieve even if you did manage to keep the cells and their connections structurally intact. So my personal view would be that it will always be too difficult, given that the preservatives affect the chemistry of the brain in their act of preserving.

Anyone else have any thoughts?

When an individual's heart stops then the lack of perfusion (nutrients ie glucose) and oxygen to the brain and the removal of toxic wastes, cause death of brain cells that is irrevocable within 2-3 minutes at room temperature. Massive damage will have occurred within 10-15 minutes that will cause cell death of the vast majority of neurons in the brain. As Richard said information is encoded and stored in cell bodies as well as axons and synapses, so global cell death will effectively wipe out everything and that will be irretrievable as far as we know. That said it is important to emphasis how very little we know about the encoding and storage of information and memories, anatomically and neurochemically.

Now onto fixation. Fixatives work by cross-linking cell surface and intracellular proteins - there is no better way of killing cells stone dead! So the above information equally applies if not more so!

As far as I was aware, fixatives such as the aldehydes (formaldehyde, glutaraldehyde) work by cross-linking proteins but other fixatives like the alcohols (e.g., methanol) precipitate and aggregate proteins. In any event you end up with a 'dead' cell! Some preservatives such as glycerol and dimethyl sulfoxide have completely different modes of actions, at certain concentrations reducing water crystal formation in cells during freezing and allowing recovery upon thawing, depending on the nature of the cell.

P.S. there is often a distinction between fixing tissues, which tends to be aldehyde-based, and fixing cells (e.g., growing in culture) which can be alcohol-based to 'preserve' many different, often structural proteins like those associated with the cell cytoskeleton.

Last edited by Steve Lolait (17th Jun 2011 22:12:30)