Video transcript: How does the brain change with age? Part #3: MEG brain waves
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Professor Rik Henson, Cam-CAN Co-Investigator, MRC CBU, Cambridge
Ok, we have two main ways of looking at the brain. One is magnetic resonance imaging, or MRI, and another is magnetoencephalography, or MEG. In the first case, MRI allows us to look at the structure of the brain so we can measure how different tissue types in the brain are effected as we get older. We can also measure function of the brain during simple tasks. This is functional MRI. So we can see how blood flow changes in response to a particular task change as we get older. The other technique of MEG, magnetoencephalography, also allows us to look at the activity in the brain but at a much faster timescale. So we can trace our brain rhythms that occur several hundred cycles per second.
Video shows volunteer with sensors attached to head and putting on glasses
Lauren Bates, Cam-CAN Research Assistant, University of Cambridge
So next I am going to put on these glasses. These are basically just going to give a kind of starting point for when I digitalise your head shape. So if I start putting these on and then if you want to hold them to your face and just put them so they are comfortable and then I will just tighten them up. Is that ok?
They might be a little bit loose.
Professor Rik Henson
The main advantage of MEG is that we can look at communication between brain regions and that is vital for all these cognitive functions like memory, language, emotion, because if our communication between brain areas is slightly delayed, or made more variable, then our cognitive functions will suffer.
So the next thing I am going to do is digitalise your head shape. Basically going to be using this electronic pen on various points on your head. So you are going to see your head shape appear on this screen there and it's basically going to tell the MEG what your head shape is. And when you come back for your MRI scan we can overlay the two lots of images, so we can look at where all the activity is coming from and kind of superimpose it on your MRI scan. So it is really important for this bit once I start that you stay as still as you can.
Video shows Lauren Bates using electronic pen to mark points on volunteer's nose and cheeks
And I just need to go down your nose and across your cheeks. Excellent, good job at keeping still. You can relax now.
Professor Rik Henson
So one of the tasks that we do is a very simple task that involves pressing keys whenever you see a flash and hear a sound.
Video shows volunteer in MEG scanner
And this activates the primary sensory regions and the visual cortex, the auditory cortex and the primary motor regions in the motor cortex. And we know as people get older the activity as measured by fMRI in these regions tends to decrease. But what we are not sure about is whether that is a consequence of changes in the blood supply to the brain as we get older or actually changes in true neuro activity. And this is what the MEG scan can tell us. It can separate out what's a true change in your activity as you get older, in response to this simple reflex task, and what's the change in the brain's plumbing if you like. So the combination of MEG and fMRI is very helpful to separate out the neuro contribution from what we call the vascular contribution, or the contribution of the brain's blood supply.
Maarten van Casteren, MEG Operator, MRC CBU, Cambridge
That's the way it looks.
Wavy wavy lines.
Video zooms into computer screen to view the MEG brain scan
Maarten van Casteren
This just gives you electrical activity somewhere in the element with only after extensive data analysis.
That is why we do the MRI scan as well.
This video may be reproduced in its entirety with due credit to BBSRC.
All media (c) BBSRC unless otherwise stated.
Music 'Shipment' by Alex Arrowsmith from www.cinephonix.com
BBSRC wishes to thank cognition unit staff and Cam-CAN interviewers:
- Kim Norman (motor learning)
- Aldabra Stoddart (MRI imaging)
- Jessica Penrose (MEG imaging)