28 November 2009

Brain Reverse Engineering

... to fully realize the brain’s potential to teach us how to make machines learn and think, further advances are needed in the technology for understanding the brain in the first place. Modern noninvasive methods for simultaneously measuring the activity of many brain cells have provided a major boost in that direction, but details of the brain’s secret communication code remain to be deciphered. Nerve cells communicate by firing electrical pulses that release small molecules called neurotransmitters, chemical messengers that hop from one nerve cell to a neighbor, inducing the neighbor to fire a signal of its own (or, in some cases, inhibiting the neighbor from sending signals). Because each nerve cell receives messages from tens of thousands of others, and circuits of nerve cells link up in complex networks, it is extremely difficult to completely trace the signaling pathways.

Furthermore, the code itself is complex — nerve cells fire at different rates, depending on the sum of incoming messages. Sometimes the signaling is generated in rapid-fire bursts; sometimes it is more leisurely. And much of mental function seems based on the firing of multiple nerve cells around the brain in synchrony. _GrandEngineeringChallenge

Seedmagazine.com Seed Design Series
Respected Neuroscientist Henry Markram recently objected to claims for cat-scale "brain simulation" by an IBM team led by Dharmendra Modha. Markram stated that the IBM team's claims were a "hoax."

Modha's team nevertheless won the Gordon Bell prize for its efforts, and in computer science circles Modha's achievement was considered a respectable one.

The National Academy of Engineering considers the Reverse Engineering of the Brain to be a worthy project, as does DARPA -- which is helping to fund Modha's team.

It is important to understand the differences between Markram's and Modha's approaches to brain simulation, in order to make sense of the public disagreements. Markram -- an accomplished neuroscientist -- is attempting to simulate the brain down to the level of synapses and ion channels on individual neuronal processes (see video above). Modha is merely simulating "neurons" as points or nodes in an extensive network of nodes. Modha is a computer scientist and his simulation is just what you would expect from a computer scientist.

The two types of simulations are meant to serve completely different purposes. Markram intends for his simulation to teach neuroscientists how the brain works on a dynamic level never before approached by neuroscience. Modha wants to build a simulation that can bring human-level massively parallel computing to complex machine systems. Modha eventually wants to build thinking machines. Markram wants to open a window on real time brain function that will help neuroscientists solve the difficult problems of brain function and pathology.

What Modha is building has very little to do with a rat brain, a cat brain, a human brain, or even an insect brain. But if he and his team want to call their work a "brain simulation", no one but Markram has objected so far. Well, Markram and Al Fin. ;-)

There is room for dozens of approaches to reverse engineering the brain, or more. The only condition should be that researchers not mis-represent the nature of what they are doing.

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“During times of universal deceit, telling the truth becomes a revolutionary act” _George Orwell

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