31 karma · joined December 18, 2008
http://www.idsia.ch/~juergen/rnn.html
http://www.lsm.tugraz.at/learning/framework.html
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.31.6...
The second link describing neurogenesis stimulation is more interesting due to the fact that they are tracking actual changes in the participants over the course of the study.
For the record, I do not doubt for a moment that exercise has numerous positive benefits, both physically and mentally.
In my opinion, rather than attempting to simulate progressively larger brains, we should instead focus on really nailing the details of smaller ones, perhaps starting with insects.
As an example, Portia jumping spiders display very complex hunting behaviors, including trial-and-error learning in novel circumstances. Even with tiny eyes, they have the visual acuity of a cat. However, unlike a cat, they are only able to see a small portion of the visual field at a time, and must therefore scan the environment, keeping the rest of what has been scanned in memory. Portia spiders are known to spend up to an hour "analyzing" their environment before deciding on a course of action! Their sharp eyesight allows them to recognize the species of the spider they are currently stalking. One common tactic is to pluck deceptively at the web of their victim in order to manipulate it into reacting and moving into a more favorable position before the attack. Different species of spiders will respond in different ways, and so the Portia learn to intelligently apply different patterns of plucking to fit the circumstances. When encountering an unknown type of spider, Portia will try various experimental plucking motions, the successful results of which will be remembered and reused correctly in future attacks.
This amazingly rich and adaptive behavior it somehow manages to produce with a mere 500k neurons; about 2000 times less than the number used by Blue Gene in the experiment.
there is no way to find out the relative significance of the input variables and how they affect the output response
Calculate partial derivatives of inputs w.r.t. outputs.
there isn't a way to cluster similar cases together to analyze what rules bind different decisions together
PCA analysis of activations of the hidden layer. Could also do k-means clustering of activations of hidden layer.
The random forest classifier looks interesting, I'll have to investigate that. Any suggestions for papers/tutorials?
Good luck - it might take awhile to get back to 'normal', but keep at it!
From their website FAQ:
Q: Do you believe a computer can ever be an exact simulation of the human brain?
A: This is neither likely nor necessary. It will be very difficult because, in the brain, every molecule is a powerful computer and we would need to simulate the structure and function of trillions upon trillions of molecules as well as all the rules that govern how they interact. You would literally need computers that are trillions of times bigger and faster than anything existing today.
Because this will only be an approximation, it means that certain hard-to-define grammatical properties of spike-trains (e.g. "neural codes" as opposed to "rate codes") may be completely lacking in the simulation. Do these "neural codes" exist? At this point we do not know.
If it turns out that the brain does utilize complex neural codes, and that they are not being accounted for in the simulation, then the simulation can be no more than gibberish which happens to share many low-order statistical features with the real thing.
To illustrate this point, here are some examples of pseudo-English sentences automatically generated by a purely statistical model (n-gram model where n=2):
Richard Beesemyers, formerly raised sagging candidate to the Friday officially forecast at the project.
A hearing appeals.
That bank handles most notable exceptions to buy time for reconsideration Wednesday in decades, is the B& Coopers, to discuss international theme for the violin away as the wages of the power plant near classic chemise.
It could have been observing the 65 to back Tuesday.
And fourth, there is a full report, Wagner said.