Chapter three largely covers the biological and physical aspects of the brain's makeup. Among discussing various functions and chemicals involved, it also mentioned briefly the EEG. The EEG, or electroencephalograph, is a noninvasive, external test used to monitor brain activity. It is conducted by the connection of up to 200 some electrodes to scalp and face, and then recording the electrical activity generated by the brain. I had a prolonged EEG (overnight) conducted on me during my freshman year of high school to determine the cause of a series of unknown pseudo seizures I had been having. Because of the brain activity, the doctors were able to rule out true seizures, but due to the fact that EEGs do not show exactly where in the brain the activity occurs, little else was revealed.
This is an interesting link that shows how this technology could someday help "brain-dead" or comatose patients communicate with the outside world.
photo credit: depts.washington.edu