How do we know so much about the brain?
Magnets and the brain [Key Stages 2-4]
What do you think would happen if you placed a strong magnet next to a television?
How might we prove that the brain is using electricity?
Part 1: Hold a magnet up to the computer screen and show the audience how it disrupts the display. Alternatively, play this clip:
Q: What do you think would happen if you placed a strong magnet near a computer?
A: Placing a strong magnet by a computer can completely erase everything stored on it. This is because computers use electricity to work and to store information in memory.
Part 2: Now play the following clip. Explain that the Transmagnetic Stimulation (TMS) machine produces a very strong magnetic field. When the magnetic field is directed at a specific part of Vince Walsh’s head, it temporarily disrupts the electricity in that area so that he is unable to perform specific functions. It’s like switching parts of the brain off for a moment to see what they normally do.
In this video the magnet is placed first over the area that is used to produce speech and, in the second two trials, over the area used to produce motor action. As you will see, stimulating the area magnetically disrupts that activity. In the first Vince Walsh becomes unable to recite the nursery rhyme and in the second two he becomes unable to touch his nose or clap his hands.
Q: Why do you think the strong magnetic field disrupts Vince Walsh’s ability to speak and move?
A: Much like the magnet disrupted the electrical signal to the television, it also disrupts the electrical signals in Vince’s brain. Because messages in the brain are passed via electricity, this temporarily stops the electrical message getting from that part of the brain to Vince’s body and he becomes unable to perform the action.
Q1: What uses might this technology have in helping us understand the brain?
A1: The TMS targets a very small area of the brain, about 1 inch squared. By temporarily knocking out that part of the brain and examining what effect it has on people’s behaviour, researchers are able to better understand what each part of the brain is responsible for and how different parts of the brain are connected. This method is especially useful because it allows researchers to understand the brain of healthy, living people. In the past most brain research had to be done through surgery, when it is often difficult to examine normal behaviours because the patient is either unconscious or lying down. Alternatively, researchers have looked at patients with brain damage to find out what parts of the brain are used for different functions but this method is less directed as brain damage rarely occurs neatly in one small area of the brain so when patients suffer subsequent difficulties is hard to tell what part of the brain is responsible.
Q2: Why doesn’t holding a normal magnet up to your head disrupt your thinking?
A2: The TMS machine produces a very strong, moving magnetic field that is strong enough to penetrate the skull. It is the fact that it is a very fast moving field that allows it to disrupt the electrical impulses in the brain. By comparison, a normal magnet produces a static magnetic field that has no effect on the brain.
There does not seem to be any long-lasting damage to people’s brains from using TMS. On the contrary, an unexpected side-effect of TMS was that people often said they felt happier afterwards. TMS is now being used as a treatment for depression.
Functional Magnetic Resonance Imaging [Key Stages 2-4]
Why might it be useful to see the structure of people’s brains?
Why might it be useful to be able to see what parts of the brain are being used when different activities are being performed?
Explain to the audience that there is also another very valuable way we can use magnets to measure how the brain works when we are thinking. This works because brains use up energy when we think. Our brain uses energy in the form of oxygen that is carried around our bodies in our blood supply. The more active a part of the brain is, the more the neurons in that region are working and the more oxygen rich blood they require.
It turns out that as blood flows past a strong magnet, it produces tiny distortions in the magnetic field that we can measure with a computer. This produces a map of the brain where we can see which regions are more active than the others because they are using more blood supply. So we can see the brain thinking! Using this technique, scientists are able to see which parts of the brain perform different jobs.
Part 1: Play the video of the introduction to the fMRI machine. Note how strong the magnetic field is!
Part 2: Introduce the audience to the structural brain image below, showing them how the person goes in and explaining which is top, bottom, left and right. Below is an image of Bruce lying down to explain how to read the brain scan. The scan goes from the bottom to the top of the head and he is pointing to the left side of his brain which would also be the left side of the brain-scan. Generally the left half of the brain controls the right side of the body and right half of the brain controls the left side of the body so if there is activation in the left side of the brain it means that the right side of the body is doing something.
For instance, when the person is shown a visual image the blood goes to the visual area which is at the back of the brain where she is processing visual information.
Part 3: Ask the audience to look at the image. Explain that the area where the blobs are is the motor area that is responsible for movement. In this image, the participant is squeezing a walnut in one of her hands. Ask the audience to decide which hand she is holding the walnut in. (Hint: Remember that the each side of the brain controls the opposite side of the body).
See the screenshot of the motor area in brain scan below that shows activation in the right motor area.
ANSWER: Thalia was holding the walnut in her LEFT hand.
Q: Where does the blood in the brain go when someone is holding something in their hand?
A: The blood goes to the motor are in the opposite side of their brain.
Q1: Why might it be useful to see a person’s brain?
A1: Unlike the TMS, fMRI allows researchers to see each person’s brain individually. This is useful because although all brains share the same general architecture, there are individual differences in exactly where different parts are. Being able to see the brain also allows doctors to examine whether there is anything wrong, such as seeing if there is a tumour or blockage.
Q2: Can we really read people’s minds using technology like the fMRI machine?
A2: Although we can tell simple things about the person from their brain image, like what hand they are holding something in, most human thought is much more complicated than that and uses multiple parts and networks in the brain. Although our understanding of the brain is getting much better, thanks to technologies like TMS and fMRI, we still only understand how to read images like this in the simplest terms. This is an area that is likely to develop a great deal in the future.