Part of the show Probing Parkinson's
Kevin Hoover asked:
“How does the brain interpret all the information that’s coming in through its senses?”
Hannah - And this really leads us on to the final question. Kevin Hoover has been in touch, again via Facebook, saying,
“How does the brain interpret all the information that’s coming in through its senses?” So for example, tactile information transmitted from his extremities such as hot, cold, smooth, and course, etc., and he’s also asking, “Is the information encoded in some fashion, rooted to different places, depended on the sensation?”
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 called 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.
Hannah - That was Professor Simon Laughlin from Cambridge University, taking on your questions about energy in the brain.
And if you’ve got any burning questions about your brain and the nervous system, just email them to firstname.lastname@example.org. You can tweet @nakedneuroscience, or you can post on our Facebook page, and we’ll do our best to answer them for you.
But if the main difference between brain logic and digital logic is just that the brain identifies stimuli per second as intensity, it wouldn't be difficult to emulate this kind of signal interpretation in digital logic. I mean, If you could tap into the nerve receptors, duplicate the signal into a digital machine, you could easily program in a way that the rate of the signal is interpreted as intensity? Matthaeus, Sun, 10th Mar 2013