Learning What The Whole Brain Does
|By placing electrodes in an orderly way, it is possible to know what areas of the cortex are being monitored by any given electrode. Pictured here is the standardized electrode placement system used in clinical medicine.|
A useful Web site that explains the EEG and how it changes in
different diseases is found by clicking
The EEG can be used to create a mapped image of the electrical activity over the surface of the brain. Other kinds of images allow scientists to see what is going on deep inside the brain, where the voltages are too small to be detected by electrodes at the surface.
These other techniques indirectly measure either blood flow or oxygen consumption at various brain areas.
|Example brain image, using the
so-called PET scan method. The more active an area is, the more
oxygen it consumes and the more blood flow it gets. These more
active areas show as bright red or orange colors in image maps.
A newer imaging technique is called MRI (magnetic resonance imaging), which is easier to perform and provides similar information about blood flow and oxygen consumption.
Imaging allows us to test such questions as: "Can you walk and chew gum at the same time?" Well of course you can, but the point is would you do things better if you did them one at a time. In one study, people were imaged while they performed two mental tasks, either separately or at the same time. The amount of brain activity devoted to each task was greater when the tasks were performed separately than when done at the same time. Common experience teaches this too. If you really want to "get into" a music recording, you close your eyes, right?
Imaging equipment can be tuned to detect metabolic
activity or volume of cells. Recent studies of brain volume shows a
marked maturation process in children in which cells die at a rate of
about 1% per year.
here to see images. This is a normal process of "pruning" away nerve
cells that are not useful. In children who develop schizophrenia, the
death rate is much faster and they don't have enough neurons left to
here for a short video on images in schizophrenia.
Click here for a complete middle-school level overview of all the methods used to learn about the nervous system.