[ExI] worlds first brain prosthesis
max at maxmore.com
Tue Jun 23 23:09:56 UTC 2009
Rich Strongitharm wrote:
>The worlds first brain prosthesis an
>artificial hippocampus is about to be tested
>in California. Unlike devices like cochlear
>implants, which merely stimulate brain activity,
>this silicon chip implant will perform the same
>processes as the damaged part of the brain it is replacing.
It's nice to see this. Ted Berger was one of
several researchers at the USC Hedco
Neurosciences department that I interviewed back
in 1995 for a feature in Extropy #15. The text of
those issues is not online (yet), but I dug it
out of my own archive. Here it is:
Professor of Biomedical Engineering and
Neurobiology. Hedco Neurosciences and Engineering.
berger at bmsrs.usc.edu
What area of neuroscience do you work in?
I work on the neurobiological basis of memory and
learning: How the brain stores information, how
we acquire new associations. Traditionally this
problem has been approached by recording from
single cells in the brain and seeing how their
activity changes during the course of learning.
One particular part of the brain is essential for
forming memoriesthe hippocampus. In many well
documented cases where patients have suffered
damage to the hippocampus, we find they still
retain old memories but lose the ability to lay
down new memories. This doesnt affect learning
of abilities, only learning of fact-based
information and associations. People have tried
to find out what kinds of neural representations
exist, what does that activity correlate with,
and then how does that change. The problem is
there are five to ten million neurons in the
hippocampus. So how do you learn how a system
like that works by looking at the individual
elements? There are too many cells. It would be
like going into a computer and looking at the
voltage at a point on the chip and then trying to
figure out how the computer does its job. We just cant do that.
I did that kind of work for 5 or 6 years and
pushed it as far as possible. It isnt enough to
understand the processes at the system level and
how cell activity relates to the memory process
itself. Whats needed is two things: You really
need a mathematical model of individual elements
and the whole system, so you can take the data
about individual neurons and try to relate that
to some structure. Secondly, youve got to have
the kind of technology that will allow you to
record from many neurons at the same time, and to
be able to mimic the computational
characteristics of the brain system when its
fully operational. You can describe it as what
seems to be a series of parallel circuits. The
hippocampus seems to function as a parallel
processor. Parallel processors are not the kind
of computers that we have on the desktop, so the
computational basis for this is not easily available.
So I moved slowly from the area of neurobiology
into the areas of engineering and mathematics and
begin to collaborate with engineers who had
developed modeling methods that were particularly
good for capturing the dynamic properties of
single cells and the collective dynamics of
neural networks. Ive also begun to collaborate
with other engineers who are capable of designing
computer chips that are used as a series of
detectors, and we use those as electrodes to
implant them into the brain to record many
different neurons simultaneously so we can get
the same population activity, the same population
dynamics that these brain cells exhibit.
These are analog devices in the sense that you
use conductive points on the chip as a basis for
recording analog signals from the brain and then
take those off the chip and analyze them in a
computer. Assuming we continue to be successful
in being able to record the activity of many
cells simultaneously, then theres the issue of
how do you take that information then mimic the
computational characteristics of some part of the
brain? So weve been working with some other
colleagues to develop analog VLSI chips that have
the characteristics of the brain cells that weve
studied. We study a single cell and model the
properties of that cell, then construct a circuit
on the analog VLSI chip that will mimic the
properties of that cell. And weve constructed
the circuits for many cells and put them all onto
one analog VLSI chip. Now we have a chip which
essentially has the same characteristics the
small population of neurons that weve looked at.
These chips have the exact characteristics of the
cells they are learning. Such a chip will allow
you to predict the activity of the neurons.
Having developed an analog VLSI chip that
essentially has on it a small population of
neurons, thats essentially equivalent to
creating a hardware model of a slice through a
3-dimensional structure. They have so far created
a population of nine neurons and have designed
one for 100. Weve essentially modeled a 2-D
plane of a 3-D structure. If you want to mimic
how the whole system works you need to do this in
three dimensions. So were also working with a
colleague in photonics where they use light
signals to connect analog VLSI devices. Theyve
developed a brand new technology that will allow
you to stack analog VLSI chips together and
sandwiched in between them is the photonic
technology for connecting those VLSI chips. Were
going to apply this technology to try to create a
3 dimensional structure which has the same
properties of at least part of the brain system.
There will be 100 neurons in each of the planes.
As many of those as we can stack together. Then
we can have the 3-dimensional characteristics of
part of the brain system. That allows you to
study the parallel processing capabilities of a
brain in a way which you cant on the kinds of
computers that you use right now. We know the
properties of those cells have the same
properties as parts of the brain. We can begin to
ask what are the dynamics of this brain system,
and how is it that a network of this kind can be
trained to learn something new.
What are your objectives with this research?
There are several objectives to this project. One
is to understand how brain systems work. What are
the computational characteristics and
computational limits of different brain systems?
We really need to have the three dimensional
structure of that brain system in a model to be
able to answer those kinds of questions. There is
a second objective: We want to create a hardware
device which will function like the parts of the
brain. There are three major advantages to a
hardware device. One is you can incorporate true
parallel processing. The second is speed: you can
do very rapid processing. The third is size. So
the second objective relates to those three advantages.
If we can mimic the computational characteristics
of the brain at a reduced scale using a hardware
device then theres no reason why we cant begin
to contemplate replacing parts of the brain that
are damaged, with computer chips that have the
same properties and can be connected to the rest
of the brain through the specially designed
interface electrodes. We can sense the activity
within the brain and we can send out signals into
the brain. These kinds of sensing probes or
signaling probes could be sandwiched on the end
of a 3-dimensional structure that could perform
the same function as the part of the brain that
we want to replace. The replacement parts would
be of a similar volume of the parts of the brain they are replacing.
The third major objective is to understand enough
about how the brain works to be able to build
devices to solve problems in the real world that
take advantage of the things the brain does
really well. One of the things the brain does
really well is to associate arbitrary kinds of
objects. There are some real world problems the
brain is very good at and does better than any
other kind of device. If we can understand what
those principles are, then we can build devices
that will solve problems in the real world. Weve
designed a device that could function as a
wireless duplication receiver based on some of
the first principles that weve understood about
the hippocampus. That may have an application in cellular phone technology.
How far off do you think any kind of neuroprosthesis will be?
It actually depends on the parts of the brain
were talking about. There may be lower level
functionsspinal cord functions, motor systems
that control the limbsthat may be possible
within ten years. For replacing the kind of
higher cognitive functions that involve learning
and memory, that would be more like ten to twenty
year range. Replacing a damaged point in the
spinal cord may be possible in ten years. The
tissue above and below the point of damage is
functioning normally. If you can sense the
activity of all the cables that are on the brain
side, and you can drive the activity of all the
cables that are on the lower spinal cord side,
and you have a set of chips which performs the
correct connection and the correct
transformational activity from the brain to the spinal cord, then why not?
How do inorganic chips connect to biological neurons?
There has been a lot of research identifying the
kinds of conditions that will allow neurons to
attach to the electronic current sensing part of
the chip. Under the right conditions cells will
attach to the metal surface and stay attached.
Whenever the cell exhibits electrical activity
then the underlying circuit will detect that
activity and transmit it elsewhere. Or, in just
the reverse way, you could actually supply
current to the chip and that can drive the
activity within the cell. So theres a way of interfacing neurons and chips.
The additional problem is how to get the neurons
that are interfaced with the chips to connect
with the rest of the brain directly. Thats a
problem where there are a lot of unknowns. But we
do know two essential principles: One is, nerve
cells connect themselves up together. There are
growth factors and a lot of other things that
guide the connections from one neuron to another.
They may not find the right pairs, but they do
find each other. Secondly, it turns out that
during development these connections are formed
between cells that are active simultaneously. It
involves part of the same process thats used in
the brain of the adult animal to store
information. The strengths of connection between
neurons in the hippocampus and in other parts of
the brain changes as a function of activity. If
two cells are active at the same time then the
synaptic connection between them is strengthened.
There are other conditions under which those
connections can weaken. We now understand a great
deal about the principles for how connections
between neurons are strengthened, and its
primarily on the basis of activity. So if a cell
has been grown to the surface of a chip and we
put this chip into the brain, and we want to
connect up correctly the cells that are on the
interface one of the ways to do that is to drive
the activity of the cells. We can control that
and as a result control in part how these cells
wire themselves up to the rest of the brain.
Although that will be a very difficult problem we
can see the beginnings of how to approach the problem.
How does this approach differ from things like
NetTalk (a neural network for recognizing speech)?
Our objective is to create a hardware model of
the function of the hippocampus. Its situated in
a part of the brain where after the rest of the
sensory systems break down the incoming signal,
determine what the features are and integrate all
those features that identify a faceits that
information that goes into the hippocampus. All
the feature analysis has been completed. That
information is processed in some way, along with,
for example, the auditory sounds that the
creature made, so that the features (which have
already been identified as a face) and the
auditory signals which identify how your name
sounds, those two things get fed into the
hippocampus and theyre associated in some way
and then sent back to the cortical regions that
do the sensory analysis, and theyre stored
there. This signal transformation process and the
association process is done in some way that
allows this human to learn this new information
and to insert it into long term memory without
disrupting all the other long term memories. The
associations formed by the hippocampus allow each
of our databases to be updated without destroying
the existing databases and make retrieval of that
data optimal. Its that function that were
trying to emulate. Not just learning new
information or identifying speech patterns, but
how to take that new item thats learned and
insert it into a database so that it has the
correct associations with all the other things the person has learned.
This is a unique effort. People with very
different backgrounds have agreed to work
together. Im one of five people. Without the
different backgrounds the problems couldnt be
solved. The Hedco Neurosciences program is
unique. The purpose is to get neurobiologists,
biologists, computer scientists, engineers,
psychologists, all in the same building. All the
members of the team are willing to be members of
a team. It turns out that there are an awful lot
of problems that we have with the neurobiology
that there are already solutions for in the field
of engineering. We just dont know about them.
So breaking down the disciplinary areas is extremely important.
How long will it be until we have a real
artificial brain of human level intelligence?
Whats most important in answering that question
is that in the last couple of years we have
reached a point both in understanding the
neurobiology of the brain and understanding the
fundamental principles of engineering and
computer science where we can entertain that
question, wheres its actually reasonable to ask
how long do you think it will be. Just five or
ten years ago, that would be seen as a science
fiction question. But now it is feasible to start
thinking about things like that, just as its
feasible to start taking about replacing parts of
the brain. I dont have the faintest idea. I
could say 50 years from now. I dont think its
unreasonable to think in those terms.
Much of the population is uneasy with the idea of
replacing parts of the brain. They believe that
theres something up here thats outside physics
and chemistry. If we replace parts of the brain
with things weve built, then arent we just a
machine of some kind? How do feel about that and
how do you think people ought to feel about it?
Should we be losing a sense of being special, or
should we just realize that were the most magnificent machines around?
To understand how the brain works and to approach
the problem of understanding cognitive behavior
scientifically its imperative to treat the brain
as a kind of machine, that this system can be
reduced to a set of parts and they have relations
to one another. When those relations are allowed
to exist theres a dynamic that unfolds that
explains the global behavior of the system. When
youre trying to explain the complex thought
processes that we engage in, when you have many
elements and the dynamics of those elements are
complex, it becomes a much harder problem. But
nonetheless, the essential tenet of the
scientific approach is that everything can be
treated as a machine and broken down into its component parts.
People will become more comfortable with
thatwith the consequences of that approach, such
as with the consequence of putting computers into
the brain. Once they experience the benefits
Everyone has a problem with their mother having
Alzheimers disease or their child having
epilepsy. Any solution is a good solution to such
problems. We not talking about changing the
entire function of the individual but simply
replacing the part that used to be there,
replacing the function that used to be there.
Then I think a lot of that resistance will melt away.
What if we do start talking about altering and
enhancing our capabilities? Without having to sit
down out a computer, what if I can work out
complex equations and trajectories, what if I can
do all those things in my head? What if I can
work out complex strategies and patterns that
would normally have to do on a very powerful
computer do you think people will be more upset about those?
Yes, I think there are going to be great social
debates over whether we should enhance the
capabilities of the brain, and do anything other
than replace non-functioning parts of the brain.
As soon as the work began to move towards
enhancing function of the brain I think that
would cause a great deal of social debate.
Personally I think it would be extremely
interesting to find out how much we could enhance
human brain function. I think it should be tried.
Now were talking way downstream, but if we can
replace brain function, well why not try to find
out how well we can enhance brain function. I
think it would be incredibly interesting to try.
I would love to be able to remember things that I
forget. How many times has it been that you
wished you were in a certain cognitive or
emotional state, and you cant be in that state.
It would be an incredible advantage to be able to have that choice.
What do you think of the idea of uploading the
contents of a brain into a computer?
I think its far more likely that these
technological developments will allow the
uploading into the brain of information from the
computer. If we can understand how it is that
certain signals input into a system, how that
neural representation is transformed and how its
associated with other representations, then it
seems to me that we should be able to upload into
a human the correct series of input signals at
the right places at the right times; well be
able to build into the memory banks new
associations that we havent in fact experienced.
Thats because weve identified a very discrete
part of the brain thats important for laying
down new memories. But we dont know where the
memories are stored. We think we know. We think
theyre stored in the neocortexphylogenetically
the newest part of the brain. But exactly where
and how its stored no one really has much idea.
Do you personally look forward to having some
neurons replaced, some functions augmented?
I would love to. That would be extremely
interesting to me. Its a challenge in sense of
being an entirely different dimension of testing
how well youve understood the system. Replacing
functions is one thing, but when youre trying to
enhance brain function, thats potentially
different problem. We might not know how to
change properties of the brain so you enhance the
functions you wanted without disrupting other
functions. Thats a very hard problem and a very interesting one.
So it takes another 100 years or 150 years, would
you want to stick around for that?
Oh, you better believe it! Without a doubt. Id love to.
Max More, Ph.D.
Extropy Institute Founder
max at maxmore.com
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