Interest in the brain extends throughout history, though its function has been periodically debated. Archaeological evidence suggests that brain surgery was practiced as early as the Neotlithic period, and many texts describing the brain were composed by the ancient Greeks. The Greek physician Hippocrates, who is often referred to as the father of medicine, considered the brain as the seat of the senses and wisdom. Aristotle, however, whose philosophies were extremely influential on Western thought, believed that the soul, intelligence, and motor control sprung from the heart rather than the brain, which he considered to be an organ of minor importance (a similar view was held by the ancient Egyptians). Aristotle based part of his argument for this view on the fact that a chicken continues to move for a short time after it is decapitated and that lower organisms, such as worms, do not have brains that are visibly similar to those of humans, though their hearts are readily apparent.

This widefield fluorescence image of a rat brain tissue section was produced by probing the specimen with Alexa Fluor 488, Alexa Fluor 568, and Hoechst 33342. The two Alexa Fluor dyes were conjugated to secondary antibodies directed against primary mouse anti-NF-P antibodies and rabbit anti-GFAP antibodies in order to label phosphorylated neurofilaments expressed in neurons (Alexa Fluor 488) and glial fibrillary acidic protein in astrocytes and certain other astroglia (Alexa Fluor 568). The nuclear counterstain Hoechst 33342 was employed to visualize cell nuclei. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.