We often imagine that human consciousness is as simple as input and output
of electrical signals within a network of processing units - therefore
comparable to a computer. Reality, however, is much more complicated. For
starters, we don't actually know how much information the human brain can
hold.
Two years ago, a team at the Allen Institute for Brain Science in Seattle,
US, mapped the 3D structure of all the neurons (brain cells) comprised in
one cubic millimetre of the brain of a mouse - a milestone considered
extraordinary.
Within this minuscule cube of brain tissue, the size of a grain of sand, the
researchers counted more than 100,000 neurons and more than a billion
connections between them. They managed to record the corresponding
information on computers, including the shape and configuration of each
neuron and connection, which required two petabytes, or two million
gigabytes of storage. And to do this, their automated microscopes had to
collect 100 million images of 25,000 slices of the minuscule sample
continuously over several months.
Now if this is what it takes to store the full physical information of
neurons and their connections in one cubic millimetre of mouse brain, you
can perhaps imagine that the collection of this information from the human
brain is not going to be a walk in the park.
Data extraction and storage, however, is not the only challenge. For a
computer to resemble the brain's mode of operation, it would need to access
any and all the stored information in a very short amount of time: the
information would need to be stored in its random access memory (RAM),
rather than on traditional hard disks. But if we tried to store the amount
of data the researchers gathered in a computer's RAM, it would occupy 12.5
times the capacity of the largest single-memory computer (a computer that is
built around memory, rather than processing) ever built.
The human brain contains about 100 billion neurons (as many stars as could
be counted in the Milky way) - one million times those contained in our
cubic millimetre of mouse brain. And the estimated number of connections is
a staggering ten to the power of 15. That is ten followed by 15 zeroes - a
number comparable to the individual grains contained in a two meter thick
layer of sand on a 1km-long beach.
A question of space
If we don't even know how much information storage a human brain can hold,
you can imagine how hard it would be to transfer it into a computer. You'd
have to first translate the information into a code that the computer can
read and use once it is stored. Any error in doing so would probably prove
fatal.
A simple rule of information storage is that you need to make sure you have
enough space to store all the information you need to transfer before you
start. If not, you would have to know exactly the order of importance of the
information you are storing and how it is organised, which is far from being
the case for brain data.
If you don't know how much information you need to store when you start, you
may run out of space before the transfer is complete, which could mean that
the information string may be corrupt or impossible for a computer to use.
Also, all data would have to be stored in at least two (if not three)
copies, to prevent the disastrous consequences of potential data loss.
This is only one problem. If you were paying attention when I described the
extraordinary achievement of researchers who managed to fully store the 3D
structure of the network of neurons in a tiny bit of mouse brain, you will
know that this was done from 25,000 (extremely thin) slices of tissue.
The same technique would have to be applied to your brain, because only very
coarse information can be retrieved from brain scans. Information in the
brain is stored in every detail of its physical structure of the connections
between neurons: their size and shape, as well as the number and location of
connections between them. But would you consent to your brain being sliced
in that way?
Even if would agree that we slice your brain into extremely thin slices, it
is highly unlikely that the full volume of your brain could ever be cut with
enough precision and be correctly "reassembled". The brain of a man has a
volume of about 1.26 million cubic millimetres.
If I haven't already dissuaded you from trying the procedure, consider what
happens when taking time into account.
A question of time
After we die, our brains quickly undergo major changes that are both
chemical and structural. When neurons die they soon lose their ability to
communicate, and their structural and functional properties are quickly
modified - meaning that they no longer display the properties that they
exhibit when we are alive. But even more problematic is the fact that our
brain ages.
From the age of 20, we lose 85,000 neurons a day. But don't worry (too
much), we mostly lose neurons that have not found their use, they have not
been solicited to get involved in any information processing. This triggers
a programme to self-destruction (called apoptosis). In other words, several
tens of thousands of our neurons kill themselves every day. Other neurons
die because of exhaustion or infection.
This isn't too much of an issue, though, because we have almost 100 billion
neurons at the age of 20, and with such an attrition rate, we have merely
lost 2-3% of our neurons by the age of 80. And provided we don't contract a
neurodegenerative disease, our brains can still represent our lifelong
thinking style at that age. But what would be the right age to stop, scan
and store?
Would you rather store an 80-year-old mind or a 20-year-old one? Attempting
the storage of your mind too early would miss a lot of memories and
experiences that would have defined you later. But then, attempting the
transfer to a computer too late would run the risk of storing a mind with
dementia, one that doesn't quite "work" as well.
So, given that we don't know how much storage is required, that we cannot
hope to find enough time and resources to entirely map the 3D structure of a
whole human brain, that we would need to cut you into zillions of minuscule
cubes and slices, and that it is essentially impossible to decide when to
undertake the transfer, I hope that you are now convinced that it is
probably not going to be possible for a good while, if ever. And if it were,
you probably would not want to venture in that direction. But in case you're
still tempted, I'll continue.
A question of how
Perhaps the biggest problem we have is that even if we could realise the
impossible and jump the many hurdles discussed, we still know very little
about underlying mechanisms. Imagine that we have managed to reconstruct the
complete structure of the hundred billion neurons in Richard Dixon's brain
along with every one of the connections between them, and have been able to
store and transfer this astronomical quantity of data into a computer in
three copies. Even if we could access this information on demand and
instantaneously, we would still face a great unknown: how does it work?
After the "what" question (what information is there?), and the "when"
question (when would be the right time to transfer?), the toughest is the
"how" question. Let's not be too radical. We do know some things. We know
that neurons communicate with one another based on local electrical changes,
which travel down their main extensions (dendrites and axons). These can
transfer from one neuron to another directly or via exchange surfaces call
synapses.
At the synapse, electrical signals are converted to chemical signals, which
can activate or deactivate the next neuron in line, depending on the kind of
molecule (called neuromediators) involved. We understand a great deal of the
principles governing such transfers of information, but we can't decipher it
from looking at the structure of neurons and their connections.
To know which types of connection apply between two neurons, we need to
apply molecular techniques and genetic tests. This means again fixating and
cutting the tissue in thin slices. It also often involves dying techniques,
and the cutting needs to be compatible with those. But this is not
necessarily compatible with the cutting needed to reconstruct the 3D
structure.
So now you are faced with a choice even more daunting than determining when
is the best time in your life to forego existence, you have to chose between
structure and function - the three-dimensional architecture of your brain
versus how it operates at a cellular level. That's because there is no known
method for collecting both types of information at the same time. And by the
way, not that I would like to inflate an already serious drama, but how
neurons communicate is yet another layer of information, meaning that we
need much more memory than the incalculable quantity previously envisaged.
So the possibility of uploading the information contained in brains to
computers is utterly remote and might forever be out of reach. Perhaps, I
should stop there, but I won't. Because there is more to say. Allow me to
ask you a question in return, Richard: why would you want to put your brain
into a computer?
Are our minds more than the sum of their (biological) parts?
I may have a useful, albeit unexpected, answer to give you after all. I
shall assume that you would want to transfer your mind to a computer in the
hope of existing beyond your lifespan, that you'd like to continue existing
inside a machine once your body can no longer implement your mind in your
living brain.
If this hypothesis is correct, however, I must object. Imagining that all
the impossible things listed above were one day resolved and your brain
could literally be "copied" into a computer - allowing a complete simulation
of the functioning of your brain - at the moment you decide to transfer,
Richard Dixon would have ceased to exist. The mind image transferred to the
computer would therefore not be any more alive than the computer hosting it.
That's because living things such as humans and animals exist because they
are alive. You may think that I just stated something utterly trivial,
verging on stupidity, but if you think about it there is more to it than
meets the eye. A living mind receives input from the world through the
senses. It is attached to a body that feels based on physical sensations.
This results in physical manifestations such as changes in heart rate,
breathing and sweating, which in turn can be felt and contribute to the
inner experience. How would this work for a computer without a body?
All such input and output isn't likely to be easy to model, especially if
the copied mind is isolated and there is no system to sense the environment
and act in response to input. The brain seamlessly and constantly integrates
signals from all the senses to produce internal representations, makes
predictions about these representations, and ultimately creates conscious
awareness (our feeling of being alive and being ourselves) in a way that is
still a total mystery to us.
Without interaction with the world, however subtle and unconscious, how
could the mind function even for a minute? And how could it evolve and
change? If the mind, artificial or not, has no input or output, then it is
devoid of life, just like a dead brain.
In other words, having made all the sacrifices discussed earlier,
transferring your brain to a computer would have completely failed to keep
your mind alive. You may reply that you would then request an upgrade and
ask for your mind to be transferred into a sophisticated robot equipped with
an array of sensors capable to seeing, hearing, touching, and even smelling
and tasting the world (why not?) and that this robot would be able to act
and move, and speak (why not?).
But even then, it is theoretically and practically impossible that the
required sensors and motor systems would provide sensations and produce
actions that are identical or even comparable to those provided and produced
by your current biological body. Eyes are not simple cameras, ears aren't
just microphones and touch is not only about pressure estimation. For
instance, eyes don't only convey light contrasts and colours, the
information from them is combined soon after it reaches the brain in order
to encode depth (distance between objects) - and we don't yet know how.
And so it follows that your transferred mind would not have the possibility
to relate to the world as your current living mind does. And how would we
even go about connecting artificial sensors to the digital copy of your
(living) mind? What about the danger of hacking? Or hardware failure?
So no, no and no. I have tried to give you my (scientifically grounded) take
on your question and even though it is a definite no from me, I hope to have
helped alleviate your desire to ever have your brain put into a computer.
I wish you a long and healthy life, Richard, because that definitely is
where your mind will exist and thrive for as long as it is implemented by
your brain. May it bring you joy and dreams - something androids will never
have.
This article by Guillaume Thierry, Professor of Cognitive Neuroscience, Bangor
University, is republished from The Conversation under a Creative Commons
license. Read the
original article.