As promised, here’s the first-ever official Connectome Q&A! We’ve been getting lots of incoming questions on our Facebook and Twitter pages – some of them on the technical side; others of the more “general interest” variety. Most of these questions require pretty involved answers – and it’s important to me that each of them gets the full treatment it deserves.
So for today’s Q&A, I’ve decided to focus on just one question. That doesn’t mean we’ve forgotten the others, though – we keep everything archived, and we’ll be doing plenty more Q&As in the future. So keep sending those neuroscience queries and article requests our way.
And now, let’s get into today’s question! —Ben
Q. “What is the best current method to preserve a connectome or whole brain – cryonics, vitrification, chemical brain preservation or something else?” —Ivan Smirnov, via Facebook
A. There are actually two different questions here: 1) “What’s the best way to preserve a brain?” and 2) “What’s the best way to preserve all the information in a brain?” There’s also a third question that’s sorta implied by the first two: “Is it possible to preserve a person’s ‘self’ by preserving that person’s connectome?” Let’s take these questions one-by-one.
When it comes to preserving brain tissue, the most successful and widely used technique available today is cryopreservation: cooling a brain to sub-zero temperatures, which stops all biological processes. Techniques like slow programmable freezing (SPF), along with cryoprotectant chemicals, can protect cells from being damaged by freezing. In fact, laboratories around the world use CPF and cryoprotectants to preserve living cells and organs – and even whole animals – for later resurrection.
A technique that shows some promise for the near future is neurovitrification, which transforms the water in living neural issue into a glass-like solid, allowing cells to be frozen with minimal damage. Though vitrification preserves many organs quite well, we’re still years away from being able to freeze and resurrect a mammalian brain – let alone a human one. In theory, a perfected neurovitrification technique would preserve living neurons right down to the molecular level, locking every atom of every synapse in place.
That kind of lockdown would be crucial for preserving and resurrecting a brain, because most information in the brain is stored not in physical connections, but in electrochemical communication networks that shift and morph from moment to moment. Keeping those synaptic molecules in place would be the only way to resurrect a brain without “wiping its hard drive.” For the same reason, it’d be vital (no pun intended) to preserve a brain before its owner had died; once those neurons have stopped firing, most of the brain’s stored information is lost forever.
This brings us to another approach: preserving the information encoded in a brain’s connectome. The idea here is that if we can understand precisely how the brain encodes various kinds of information, we could record and save a digital “copy” of its connectome – perhaps without having to map the location of every molecule in every synapse – and, helpfully, without having to freeze a living person (possibly ending his/her life and thus defeating the whole point).
To understand how a connectome does what it does, efforts like the Human Connectome Project, the Whole Brain Catalog and the Open Connectome Project aim to produce functional simulations of brain activity at all scales. Before we can build a digital copy of a connectome, we need to understand exactly what needs to be copied, and how it’s supposed to work.
Connectome naysayers claim that even this won’t be enough. They draw comparisons between the Human Connectome Project and its earlier cousin, the Human Genome Project (HGP). Although the HGP has led to plenty of breakthroughs, we’re still a long way from understanding what most of our genes actually do. And whereas a human genome has about 3,000,000,000 (3 billion) base pairs, a human connectome may involve as many as 100,000,000,000,000 (one hundred trillion) synaptic connections – all of them constantly transforming and exchanging information with their neighbors. At the very least, we’re going to need some major innovations in computing power, and a vastly expanded program of data-gathering, before we can simulate an entire human connectome at the synaptic level.
Of course, none of this tells us anything about whether preserving a person’s connectome or brain – even flawlessly – will preserve that person’s mind/self/individuality. Sebastian Seung, one of the big brains behind the Human Connectome Project, has called the question of immortality “the only truly interesting problem in science and technology.”
We know that some animals, such as frogs and salamanders, can be frozen for long periods, thawed, and awakened to keep going about their amphibian business. So far, though, no one’s been able to do this with a mammal – so it’s unclear whether it’d be possible to resurrect your dog or cat, spunky personality and all. (Unsurprisingly, that hasn’t stopped wealthy pet owners from putting Rover on ice just in case.)
As with the connectome mapping projects, the problem with preserving a personality is that no one knows exactly what needs to be preserved: living nerve cells, positions of neurotransmitter molecules, and/or certain kinds of neurochemically encoded data might all be necessary pieces of the puzzle.
In other words, what works for frogs and salamanders may or may not work for mammals like us. It’s unclear whether what we call a “self” is correlated with stable body temperature, or even with a cerebral cortex – for example, there’s some evidence that octopi may have a form of self-awareness, and they’re ectothermic and have very different neural wiring from vertebrates.
It’s also very unlikely that one day in vertebrate evolution, the “self” just popped into being – more likely, self-awareness arose gradually out of the interactions among many self-referential circuits of brain activity; the same goes for personalities, emotions, hopes, fears, and all the other vaguely defined ghosts that haunt our machinery.
What this implies is that the processes of understanding, disassembling and reverse-engineering the “self” are going to be very gradual ones. It’s likely that we’ll spend decades studying correlations between neural activity and subjective experience before we understand exactly how they correlate – which means that for the foreseeable future, the only one who’ll know for certain whether a resurrected brain contains “the true-blue you” will be …well… you.