Science Questions

Where do decisions originate in the brain?

Tue, 12th Jan 2016

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Calvin Armstrong asked:

How are decisions made within the brain? With regards to movement, what's the processes that take place that causes the neurones to fire? How do they become excited and then cause movement?


Kat Arney put this question to Ginny Smith...blood brain barrier

Ginny - Well, as with many brain questions, the answer is we don't fully know yet.  There's a very famous experiment done by a guy called Libet, where he asked people while they were in a brain scanner to move their finger whenever they felt like it but remember the time, and they were looking at a clock face, that they decided to move.  And he found there was a 200 millisecond delay between them having the urge to move and the movement. But, 550 milliseconds before the urge, he could see a pattern of brainwaves that she called the 'readiness potential'.  So, effectively, these people's brains knew that they were going to move before they consciously made the decision, which has been used for a long time to sort of argue against the idea of free will.  Our brains are making these decisions and we, our kind of conscious selves, come afterwards.  But more recent experiments have shown that actually, this readiness potential is active whether you're deciding to do something or whether you're deciding not to do it.  And there was a new study out recently where they were scanning people's brains and when they saw this readiness potential, they then sent them a signal saying stop yourself from moving and, actually, they were able to stop themselves for quite a long time after this readiness potential was there.  So that pattern of brain waves itself isn't enough to actually make you make the movement, but it is sort of involved.

Kat - I mean, I guess, if you had to think about every single thing you're doing all the time, you'd just be freaking out.  You wouldn't be able to survive...

Ginny - Yes.  A lot of what we do is effectively on auto-pilot.  It's being controlled by our brains without any conscious intervention.


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