Cognitive neuropsychology
This way of looking at problems in the brain lead to studies of epileptic patients. An epileptic patient is a person that frequently suffers from seizures. These seizures were studied to learn more about how the brain sends electrical signals.  These electrical signals were then measured. It was found that each neuron can send a signal at certain speeds. These neurons were then dyed with a stain in order to be seen. At first it was thought that all nerves were connected like a web called a nerve net. However, with more complex stain it was found that each nerve is separate and can fire on their own.