Key Stage 4 Magnetic Resonance Imaging Watching the brain at work

If you wiggle your fingers… …there is more activity in these brain areas.

These areas of the brain need more oxygen… activation statebaseline More blood flow More oxygenated blood Less distortion of magnetic field More fMRI signal …which the blood delivers

An experiment rest move rest move rest move rest Task FMRI signal time These areas of the brain are active during movement, but not rest.

The FMRI scanner looks at one brain slice at a time…

You can locate an area of the brain using X, Y, and Z co-ordinates. The image is divided into voxels. Voxels are 3D pixels.

The trace shows that this voxel is relevant to the task.

Colour Vision FMRI does not give an absolute measure, so you need to look at signal change. To isolate one brain function, compare the condition you are investigating to a control condition.

The subtraction approach: vision View grey stimuli (control) View colour stimuli grey colour grey colour grey colour grey Task: fMRI signal time

The subtraction approach: vision - =