# According to doctors, how feasible is preserving the dying for future revival?

Whenever I give a public talk - after I’ve finished explaining how neuroscientists can now selectively manipulate or erase a mouse’s memories, or how patients sometimes have their heart and brain activity entirely stopped during surgery by cooling them below 20°C - and I’ve finished making the case for preserving the brains of dying people so as to give them a chance of future revival, I’m inevitably asked the following question during Q&A:

“OK, but what do your colleagues think?”

It’s a good question.

When I say ‘brain preservation may be able to stop people from dying’, I’m making a weird, bold claim. Weird, bold claims are mostly wrong. Still, if the claim is being espoused by a community of relevant experts - rather than just a few enthusiastic advocates - it’s much more likely to be worth taking seriously.

Of course, in an ideal world, I wouldn’t need to cite expert opinion at all; I’d just be able to show you unambiguous evidence of the procedure working, from preservation through to revival. I dream of the day when the first revived laboratory mouse - revived from cryogenic temperatures, or uploaded into a robotic murine body - runs through a maze just as it did before it was preserved. (Perhaps perversely, I would even appreciate some definitive proof that preservation *cannot* work - at least then we’d know this avenue was closed, and could turn our efforts elsewhere.)

But preservation is a two-part technology. The preservation half happens now; the revival half happens (maybe) in the future. We can’t run the full experiment just yet. For now, we’re stuck doing what we do for any consequential question where we can’t just wait and see (as with climate change projections or assessing the trajectory of AI development): we gather the best available evidence, and we ask the people most qualified to interpret it.

So, to return to my perennial audience question then, what do my scientific and medical colleagues think of the prospects of preservation?

Last year, Andrew McKenzie, Emil Kendziorra, and I surveyed 312 neuroscientists about the neurophysiological foundations of memory and whether preservation could enable indefinite memory retention. We found the typical respondent believed there’s a 40% probability that a well-preserved brain retains its long-term memories and could eventually be uploaded[1](https://preservinghope.substack.com/p/according-to-doctors-how-feasible#footnote-1-180478161) ([publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0326920), [blog post](https://neurobiology.substack.com/p/how-likely-is-brain-preservation), [news article](https://www.thetimes.com/uk/science/article/should-you-freeze-your-brain-these-scientists-think-its-worth-a-shot-2tlr6sd7r)).

This year, we turned to the medical community. Using Sermo, an online survey platform for healthcare workers in the US, we asked 334 doctors how likely preservation is to work, whether they’d endorse medical interventions that could improve preservation outcomes, and what they thought about the ethics of the whole enterprise.

If you’re a nerd, here’s the [preprint](https://www.medrxiv.org/content/10.64898/2025.12.03.25341583v1), the [survey](https://osf.io/awgk7/files/jn27a), and the [raw data](https://osf.io/awgk7/files/hrm76). Otherwise, read on for a summary.

### Feasibility

Our central question was how likely doctors thought preservation was to actually work. To assess this, we presented them with an idealised scenario: an elderly patient who wanted preservation, who suffered a cardiac arrest, and who was preserved within minutes. Follow-up imaging and biopsies confirmed intact brain structure down to the synaptic level. Given all that, how probable did they think it was that this patient could eventually be revived?

The median response was 25%.

[![](https://substackcdn.com/image/fetch/$s_!8nua!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F586c5fc8-ed64-455b-9a73-23e9ad4fa8c9_1600x984.png)](https://substackcdn.com/image/fetch/$s_!8nua!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F586c5fc8-ed64-455b-9a73-23e9ad4fa8c9_1600x984.png)

> ‘During end-of-life planning discussions, an elderly, cognitively-intact patient expressed a desire for preservation. Imagine that later they suffer a cardiac arrest and are successfully preserved within minutes of the event. Follow-up imaging and brain biopsies show intact brain structure down to the synaptic level, including the spatial distribution of key biomolecules. How probable do you think it is that a significant amount of the neurally-encoded information required for long-term memory and personality is still preserved in their brain, such that it may be technologically possible to revive this patient, even in the distant future?’

We also asked the question more qualitatively: “How plausible do you find the idea that preservation could potentially allow for some form of revival in the future?” Here, 27.9% of respondents found it somewhat or very plausible, while 47% found it somewhat or very implausible. The remaining quarter were neutral - which, given the uncertainty involved, seems fair enough.

When we broke the probability estimates down by specialty, nothing dramatic emerged. Neurosurgeons were slightly more optimistic, palliative care doctors slightly more pessimistic, but medians hovered between 20-30% across the board. (We weren’t really powered to detect subtle specialty differences anyway, so I wouldn’t read too much into the variation.)

### Interventions...

\[See the rest at the link above\]