My own view would be that the nervous system suppresses the motor system when we actually go to sleep. This is why we don't end up acting out more of our dreams, because of this region in the brain stem that stops the motor pathways going through.  That will include some of the more complicated movements that make vocalisations happen, but you’re still, in your dream, going to be talking and things, aren’t you?  So, that’s why you would talk out loud sometimes - I guess there’d be a breakthrough of that suppression activity. 

We put this to Professor Jack Gallant and Professor Paul Fletcher...

Jack -   I think that’s definitely a myth.  We use a lot of our brains a lot of the time, and it switches back and forth all the time.  Which sub-systems of the brain are being used depends on the task and what you're trying to do, but the brain is there for a reason and you're using a lot of it most of the time.

Paul -   I was just thinking, the person who started that rumour was probably using 10% of their brain at the time, I think.

Chris -   Very good!  The point is, if you look at someone who’s had a stroke and they may have only lost a small amount of their brain, they nonetheless don't look normal or they may not behave entirely normally, indicating that you need all of your brain.  It’s just slightly less active at certain times.

Paul -   Yes.  I mean, one could add that people who’ve had a hemispherectomy – a whole half of their brain removed at an early age - actually go on to achieve great things intellectually.  So, if it happens early enough and the brain is sufficiently plastic, then actually you can do without a lot of the volume of the brain, but I think you would use what was there 100%.

We put this to Professor Paul Fletcher and Professor Jack Gallant...

Paul -   I don't know if that’s a great metaphysical question.  I mean, the brain scanner is looking at how the brain behaves when it is seeing something that isn’t there, so it’s not so much interested or able to see the content of that although as we’ve just heard from Jack actually, the possibility of seeing what the brain thinks is there is possibly something for the future.

Chris -   Any comment on that Jack?

Jack -   Yeah.  I think there’s growing evidence that when you have a visual hallucination, what’s actually happening is the visual areas of your brain are being activated, essentially top down from inside out and the visual experiences you have in the visual hallucination are –since the brain subsystems were being operated in those cases are visual, then you both experience visual events and you could decode visual events because you're decoding from the same parts of the brain that are encoding visual information normally.

Chris -   And hence, what you've got is this system where you think it’s real because it’s the same bit of the brain that would say, “Yup, I'm experiencing something” but it’s just being internally generated.

Jack -   Right.

We put this to Professor Jack Gallant...

Jack -   As far as anyone knows, there is no long term danger from MRI.  Magnetic Resonance Imaging involves putting someone in a very large stationary magnetic field.  As far as anyone knows, it has no influence on any systems of the body or any biological systems.

We put this question to Professor Paul Fletcher...

Paul -   You certainly can - you can get hallucinations in any sensory modality.  You can get hallucinations of taste, smell, touch, as well as visual and auditory.  In fact, in certain cases of mental illness, hallucinations of smell can be exceedingly unpleasant and people can have the belief that they're actually rotting from the inside.

Chris -   That’s not very pleasant.

Paul -   It sounds horrible.