Now on ScienceBlogs: Hell Yeah, Hubble!

Seed Media Group

The Week In ScienceBlogs: Sign up for our newsletter.

Search


Profile

me_w.jpg
I am a postgraduate student of neuroscience at UCL.
Contact me

rss2-1.png


Follow me on Twitter
Get e-mail updates

Recent Comments

Recent Posts

Selected posts

Books


wishlist.gif


My photos

www.flickr.com

Rotating blogroll

(Complete list/Shared items)

Archives

« Those clever corvids | Main

Connectome? Not so fast...

Category: Neuroscience
Posted on: August 11, 2009 8:30 AM, by Mo

AS Seed's Featured Blogger of the week, I have written a short article about the Human Connectome Project, in response to a news story on the magazine's website, called Mapping the brain's highways, by Azeen Ghorayshi.

Several weeks ago, the National Institutes of Health announced the Human Connectome Project, an ambitious $30 million five-year initiative, which aims to map the connectivity of the human brain.

Is this feasible? In short, the answer is no. The idea that a complete connectivity map of the whole brain can be achieved within five years is unrealistic, and producing a microscale map at the level of single neurons and synapses within that time frame is impossible.

To find out why I think a whole brain connectivity map won't be achieved within five years, continue reading at the Seed Magazine website. Any comments, about either of the articles or about the connectome project itself, should be posted here.

Trackbacks

Trackback URL for this entry: http://scienceblogs.com/mt/pings/116889

Comments (13)

1

Probably not in 5 years. But even if, it would only be a step. A big and worthwhile step, mind you, but look at the C. elegans and stomatogastric people: they've had their connectomes for quite some time now (1990s) and still don't fully understand how it all works.

Posted by: Björn Brembs | August 11, 2009 10:37 AM

2

Part of the problem is that there is no such thing as "the connectome". The STG that Bjorn mentions is a perfect example. Regardless of the anatomical connectivity--i.e., patterns of morphological synaptic connections--there is so much functional plasticity that the anatomical connectome tells you almost nothing of functional relevance.

Posted by: Comrade PhysioProf | August 11, 2009 1:43 PM

3

My friend just got a job in Germany trying to get this working for mice with this guy. I'd imagine that will be done in 5 years. Humans would probably be another 5 or 10 years after that, although it might take a ridiculous amount of storage, as my friend was already mentioning dealing with petabytes of data for mice.

Posted by: Kevin H | August 11, 2009 2:14 PM

4

Also, there's this in the article: "Undoubtedly, a whole-brain connectivity map will be useful to researchers once it is eventually completed. But what such a map can tell us about how the brain actually works is likely to be limited. This is because the connectome apparently ignores the phenomenon of neuroplasticity."

I just don't agree. Not about neuroplasticity not being important, but because the arguably most profound topic of neuroscience, consciousness, has not much to do with plasticity and everything to do with the connections in a brain. The secret to consciousness will be in that wiring diagram, although it make take use another decade to find it.

Posted by: Kevin H | August 11, 2009 2:45 PM

5

In the article, you write:

"Neurons can sprout new connections within minutes of a given stimulus..."

I found that interesting. I was under the impression that stimulus dependent plasticity is mainly the strengthening and weakening of synaptic connections as in Hebbian learning rules, since, afaik, we start of with more synapses than we need and gain function through the pruning of the ones not needed and the tuning of synaptic strength.

If neurons, throughout life, sprout new connections in response to stimuli, what guides the axons so as to facilitate optimal response to the kind of stimuli presented. I was under the impression that axonal guidance worked primarily through chemotaxis along glial structures in development. I guess my main questions is: How would new axons wire to increase functionality in light of the above?

On a side note - I completely agree with the points you make: Plasticity and glial contributions seem essential to understanding brain-function, and I can't see how we should have the technology to make a sufficiently detailed human connectome.

Also, I wonder what you make of these publications on connectomes:

* Hagmann P, Kurant M, Gigandet X, Thiran P, Wedeen VJ, Meuli R, Thiran JP (2007) Mapping human whole-brain structural networks with diffusion MRI. PLoS ONE 2, e597.

* Hagmann P, Cammoun L, Gigandet X, Meuli R, Honey CJ, Wedeen VJ, Sporns O (2008) Mapping the structural core of human cerebral cortex. PLoS Biology 6, e159.

* Izhikevich, EM, Edelman, GM (2008) Large-scale model of mammalian thalamocortical systems. PNAS 105, 3593-3598.

Posted by: MPhil | August 11, 2009 3:51 PM

6

Thanks for editing in the links... I forgot that... okay, to be honest, I was just lazy. Sorry.

Posted by: MPhil | August 11, 2009 6:07 PM

7

So, KevinH, you say 10-15 years for the connectome, and 10 years after that to solve the problem of consciousness?

Consciousness is far more complicated than the sum of connections in the brain, more like a continuous sequence of transient whole-brain connectivity configurations, each lasting just thousandths of a seconds.

I really doubt we'll find the secret to consciousness so quickly, but time will tell...

Posted by: Mo | August 11, 2009 6:14 PM

8

MPhil: Sprouting new connections doesn't involve axon guidance. It refers to the formation of dendritic spines, the tiny bulbous projections at which much synaptic signalling takes place. Pathways can become strengthened by the addition of new spines (increasing the number of synapses in the pathway), and weakened by their removal (which decreases the number of synapses).

Yes, it was very lazy indeed not to add links. I did so because all the papers are freely available - two in open access journals, and the third as a PDF. They're all key papers, I guess, in the emerging field of connectomics. There's also this 2005 paper by Sporns et al, in which the term "connectome" was first introduced (also open access), and here's an old post about a hi-res topological map of the human brain.

Posted by: Mo | August 11, 2009 6:47 PM

9

#4
the arguably most profound topic of neuroscience, consciousness, has not much to do with plasticity and everything to do with the connections in a brain. The secret to consciousness will be in that wiring diagram

How could you possibly know that?

#7
Consciousness is far more complicated than the sum of connections in the brain, more like a continuous sequence of transient whole-brain connectivity configurations, each lasting just thousandths of a seconds.

Or even that?

(Without knowing what consciousness is first, which, of course, we don't.)

Posted by: Nigel | August 12, 2009 2:48 AM

10

Nigel: Of course I don't know what consciousness is, but I think it's more likely to involve transient connectivity configurations than being merely the sum of connections.

Posted by: Mo | August 12, 2009 4:52 AM

11

Mo: regardless of what you "think" consciousness is what you lack for your assumptions is any definitive proof to support your bold claims. If consciousness were so easily explained as simply (which of course is nowhere near simple) transient connectivity configurations then permit me to ask a question or two.

1. If it does turn out to be transient connectivity configurations, which of those account for what is "essentially" consciousness? Can simple bio-electrical currents and neuro connectivity truthfully and honestly be shown as a picture or even interactive map shown in real time, and pointed at and said about with any real certainty "This is what human consciousness is"?

2. Is human consciousness reducible to any single set of connectivity configurations? Because saying that it is more than one set of connectivity configurations makes one wonder just exactly which of the many numerous configurations actually have to do with consciousness and which are simply reflexes, if it IS in fact a single set of them, then, you're looking at a set of connectivity functions that is impossibly complex and could never be mapped or discovered.

I think this article is an ambitious goal, but will ultimately be of limited use pertaining to actual consciousness. Even if the claim was made about it that "this represents the human consciousness" then there will always be skeptics like Nigel above who will always be able to ask "How could you possibly know that?" and they will be right for asking. Furthermore, there is no answer anyone could give that will satisfy the question. You couldn't know that. No matter how much "scientific" proof you give, consciousness will likely fall into those cracks between certainty and questioning. It very well MIGHT be as you say. But even if it IS as you say, you could never know with any real certainty if it was or not.

Posted by: Nathan | August 12, 2009 3:11 PM

12

Nate: I'm not the one making bold claims here. I'm not the one who believes that a complete complete connectome will lead to the secret of consciousness in 15 years' time.

I didn't mean that consciousness *is* a bunch of connectivity configurations. But it would certainly involve this, at the very least, because the activity patterns associated with that sequence of configurations are the neural correlates of consciousness.

I doubt we'll ever fully understand how consciousness emerges.

Posted by: Mo | August 12, 2009 3:30 PM

13

Mo:

"But it would certainly involve this, at the very least, because the activity patterns associated with that sequence of configurations are the neural correlates of consciousness."

This is an unprovable statement and so I find it hard to be as certain as you are about it. While I also agree that it is likely true, at least to a certain extent, there really isn't a way to dive into a persons "private subjectivity" to understand how their consciousness is reacting or interpreting or understanding, or feeling, or....ect. So even if it plays a role, what role, and how that role is even related to consciousness? I shall quote an intelligent source to respond to these questions.

"I doubt we'll ever fully understand how consciousness emerges." -Mo

In other words, I agree...and disagree at the same time, but not with your principle, more with your certainty about the principle.

Posted by: Nathan | August 12, 2009 4:12 PM

Post a Comment

(Email is required for authentication purposes only. On some blogs, comments are moderated for spam, so your comment may not appear immediately.)

ScienceBlogs

Search ScienceBlogs:

Go to:

Advertisement
Advertisement

© 2006-2009 Seed Media Group LLC. ScienceBlogs is a registered trademark of Seed Media Group. All rights reserved.

Sites by Seed Media Group: Seed Media Group | ScienceBlogs | SEEDMAGAZINE.COM