When a cortical area is active, what happens in that brain area to produce the observations that can be made...?
(a) the EEG method
(b) the MEG method
(c) the fMRI method.
- 1 month ago
I don't know about the MEG method, but EEG just picks up and amplifies electrical impulses under each area of skull. They literally take like twenty-five little electrodes the size of a pencil eraser, little copper disks with a little hole in the center, and part your hair, and squirt a half-a-pea sized blob of conductive gel onto your scalp that also holds the electrode in place. Then they sit back and observe the results and make notes about whether your eyes are open or not, your breathing etc. They may put you through some tests like flashing lights, word association tests, etc. Neurons fire off at regular intervals, usually several dozen times per second. The neuron has to build up to some potential before it can discharge neurotransmitter across the synapse. I guess the EEG is picking up on that buildup and release of electrical charge... The neurons don't really carry electricity like a copper wire, rather they have one charge on the inside of the nerve, and the opposite charge on the outside of the nerve, and that charge flips over like a row of dominoes falling. The nerve takes a fraction of a second to reset because little pumps pump the charge back to its original state. The functional MRI (I think) may use a radioisotope to show where the most oxygen is being used. High oxygen use=High brain activity. Oh, and it has a really fast refresh rate, so they can watch areas of your brain light up in response to questions or tasks. It really can see the difference between a bilingual person that learned both languages as a child, and another bilingual person that learned a language later in life like, in college.