How does the brain interpret info?

20 January 2013



Kevin Hoover asked:

“How does the brain interpret all the information that’s coming in through its senses?”


Professor Simon Laughlin of Cambridge University tackles this...

Simon -   The reason that you're able to detect hot and cold, and touch and so on, and tell the difference between those different types of energy which are impinging on the surface of your body, is that in your skin, you have sensor receptor cells which are sensitive specifically to heating, specifically to cooling, to particular types of touch, fast, sharp, shocks, deep, stretches, and so on.

And so, those sensory receptors in the periphery already sort out the different types of stimulus that are impinging on your skin and each one of those sensory receptors sends an axon or wire to the brain and it sends it to a part of the brain that’s specifically concerned with hot or cold, or with different types of touch.

So, the information is being – what we call in neuroscience – "line labelled".  If you're sitting in the ground, you see an electrical signal coming along a particular line and you know that that line comes from a receptor which only responds when the temperature of the skin goes up then you know there's an increase in the signalling, electrical signals coming in means that that part of the skin is getting warmer.

So, how is this information encoded?  The answer is that it’s encoded by electronic pulses.  So they're very brief, rapid, up and down changes of electrical potential that lasts for 1/1000th of a second.  Now, it’s tempting to say that these are digital because a digital computer works by making electrical pulses which from being down, which is zero to up which is being 1.

But in fact, the brain is not a digital computer.  It’s not processing information using digital logic.  These pulses are coding the strength of the stimuli, how intense they are by the frequency with which they occur, i.e. how many pulses are there per second?  And when the rate of pulses per second goes up, the brain generally interprets this as the intensity of the stimulus becoming stronger.


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