Do we only use 10% of our brains?

20 January 2013


A brain sparking with electricity.



Etienne Mustow via Facebook asked:

“Is it true that we only use 10% of our brains and if so, why? What happens to the remaining 90% of our brain?”


Professor Simon Laughlin from Cambridge University flexes his brain power to answer this...

Simon -   The answer to this question is really contained in the answer to the last question.  That your brain is ticking over all of the time and when you actually engage in a specific task, you do something specific, a small path of the brain that’s concerned with doing that task becomes more active, starts signalling more vigorously to process the information that’s needed to solve that problem or to stop you falling over or whatever.  And that is why that because it’s a small fraction that gets switched into action to do something specific, that’s why people could not measure a big change in energy consumption when the brain engaged actively in some specific mental work.

What this means is that there are large parts of your brain  which are just ticking over, and they're sitting there, ready to engage in something when they need to.  So, you might ask the question, “Well, could I in fact have more of these parts of the brain switched on and do incredible multitasking?”  And the answer is, no.  When these small regions of the brain become more active to do a specific piece of mental work, their signalling rates go up by a factor of about 10. 

And some work that David Attwell and I did a few years ago – Dave is Professor of Neuroscience at UCL in London – work that we did a few years ago shows that if you were to increase the activity of every neuron in the brain ten-fold, then your brain would be using more energy per second per gram of brain than an Olympic sprinter, making a world record attempt.

Hannah -   So, in that case, is it true that you can only use 10% of your brain by concentrating on one particular task any time or do you think you could recruit maybe 25, 50% of your brain to be much more energetically active and engaged in many different tasks or is your brain somehow got some capacity to stop that from happening?

Simon -   Well, it mainly comes from – the capacity is really in-built into the architecture of the brain.  The architecture of the brain is that it’s not a general purpose computer that uses a small set of circuits to do everything.  It’s a specialised computer which has a specific set of circuits for every task and because of that, when it’s able to deal with everything, but only a small fraction of the brain circuits will be engaged in that at any one time.


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