Friday, June 13, 2008

Reverse engineeering the brain

Our brain is an extremely complex byproduct of evolution. After decades of research and centuries of thought(from Descartes to Pinker), a lot of questions about the brain still remain unanswered. Like - which is the best way to model a human brain ? Many attempts have been made to accomplish to task.

The brain is said to contain as many neurons as there are trees in the amazon and as many neural links as there are leaves on all those trees together! Simulating or creating a model of such a beast is, no wonder a Herculean task. Another big obstacle in doing that is - we still are not clear about exactly how some of the things work in our brain. A brain is often compared to a digital computer and the neurons to bits. But, the analogy is not quite exact. All the neurons are not at the same level of importance although functionally there are similar. Research shows that the neuron firings which earlier were thought to be strictly binary (on or off) can in fact be graded. The action potential can lie between the on and off voltage for some neurons for some time. This fact complicates matters, because now the neuron cannot be taken analogous to a binary digit while preparing the model. Apart from that, the firing depends on the inputs from hundreds or thousands of neurons connected to the firing neuron. The connections are not physical unlike in a digital computer. The connection is through a synapse, and the 'connector's are chemical rather than physical. A lot of complicated chemistry(and eventually physics) is involved in the whole process of making a neuron fire. Scientists say that, all that happens during this process cannot be explained by classical physics. Welcome quantum mechanics! If quantum mechanics comes into this picture, then naturally uncertainty and randomness are also in. It is indeed amazing that, with such a complex architecture inside, most of the brains continue to work well for decades! The brain (of course!) does what ever a turing machine can do. But, in addition to that it does what a classical turing machine cannot - generate new ideas! The quantum stochasticity in the brain is what is said to aid generation of 'new' ideas and that is why, in the big picture, the brain is a said to look like a quantum stochastic turing machine.

Simulating the brain by considering every neuron and every synapse is a work of a super computer, and a super computer indeed has been employed to do that work. A super comp based on the machine which beat the world chess champion - the Blue gene by IBM is being used to simulate the brain. The name of the project is Blue Brain. The project will take a decade to bear serious fruit. Nature took millions of years to build our brain, and we are trying to reverse engineer it in a few decades. Quite an ambition... :)

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Tanmay said...

This is really informative. Although it does not clear one thing -- How the human brain takes man towards its ultimate aim in life :)? Or does brain play any part regarding this?

Pranav said...

Hi Tany,
Actually, the brain has evolved just to take man towards his 'ultimate aim' in life. The sole function of the brain is to achieve that 'aim', so, whatever the brain does is just for that. :)