Wednesday, 29 August 2012

Why do we have a brain?


In the last two posts, we wrote about how closely related our brain and body functioning are. The relationship showed to be a very close one: impairments in cognitive functioning clearly were accompanied by impairments in body movements and speech. These results are not surprising when we listen to Daniel Wolpert from the University of Cambridge who holds the opinion that the only reason we have a brain for is movement. Nothing else.

He opens his TED Talk by asking the question: Why do we and other animals have brains? He explains that the only reason we have a brain for is to produce adaptable and complex movements. Moving (which happens by using our muscles) is the only way you have of interacting with the environment. Once you don’t need to move you don’t need a brain.


In his talk, Daniel Wolpert points out that computers are better at problem solving than humans because there is always an algorithm: look at all possible moves and choose the one that will make you win. But when we move, there is no such algorithm. The problem is that sensory feedback is noisy or corrupted, and so is the movement command. In order to perform precise movements, the noise needs to be minimised as far as possible. Moreover, the outside world is ambiguous and variable.

One way to deal with uncertainty is Bayesian Inference: data (e.g. sensory input) and prior knowledge (e.g. memory) are used to create certain beliefs, which we can then use as basis for making inferences about what is going to happen. This way, we can prepare our movements. Along with executing the movement, we predict its consequences in our system so that we can react to the outcome of the movement. This also gives us the opportunity to sort out which part of the movement we caused ourselves and which part of it was caused by the outside world. We do so by subtracting our predictions from the sensations or perceptions we have.

What makes movements, apart from the uncertainty of the outside world, so challenging is that there are so many options, so many ways of executing the movement. We choose the movement in such a way that it minimises negative consequences of noise. Therefore, we move in very stereotypic ways.

The key message of this talk is that moving our bodies is an immensely complex task, a task that really seems to require 100 billion neurons (some say even more) in our brains, all of them connected with many others in complex ways. The conclusion is simple: If you want to maintain something, use it for what it was made for. If you want to maintain your brain, use it for moving your body. Especially because some researchers seem to consider sitting a lethal activity, as outlined in an article in the New York Times. Exercise, play musical instruments, create pieces of art, talk to others, write. Do gardening, housework, whatever you like, but MOVE!

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