Neuroscience is the scientific study of the nervous system. The more neuroscientific research progresses, the more clearly it is established that human behavior and mental processes—the key interests for psychological study—are intimately intertwined with activity in the brain. It encompasses the branch of biology that deals with the anatomy, biochemistry, molecular biology, and physiology of neurons and neural circuits. It also encompasses cognition (thinking) and human behavior.

He became a man of bad and rude ways, disrespectful to colleagues, and unable to accept advice. His plans for the future were abandoned, and he acted without thinking about the consequences.

Surgical errors, extreme mistreatment, and tragic accidents are impactful events that can alter individuals significantly, providing unique opportunities to study the effects of experiences which can not be ethically studied experimentally.

In 1950, positron emission tomography (PET) scans were used to look at brain activity or communication in a living patient. Researchers were able to look at different parts of the brain in different situations. In other words, they could look at real time activity of the brain as the person laughed or was scared to see what ares of the brain lit up. This gave an indication of what areas of the brain maybe responsible for different emotions or behaviors.

This led to the formation of the neuron doctrine, the hypothesis that the functional unit of the brain is the neuron, also known as a nerve cell. Today, the field accepts neuronal theory which states that the nervous system is made up of individual nerve cells called neurons (Klein and Thorne, 2006).

In 1848, John Martyn Harlow treated Phineas Gage and documented his case. Gage, who was a railroad worker, had his frontal lobe pierced by an iron tamping rod in a blasting accident. He survived the trauma but suffered extensive damage to his left prefrontal cortex (Macmillan, 2001). Through Gage's case study, Harlow showed the connection between the prefrontal cortex damage, executive functioning, and personality changes.

Starting in early 1800's, a series of researchers began to catalog different brain parts and their presumed role in behavior.

Galenic view of anatomy (which emphasized three major systems--the heart, brain, and blood--and the importance of a balance between four bodily fluids--blood, phlegm, and black and yellow bile)

Early philosophers, such as Aristotle (384-322 B.C.E.), believed that one's mind resided in the heart. He believed that since our blood started from the heart, the soul also originated there. Plato (428-347 B.C.E.) argued that the executor of reason was the heart and our animalistic desires and emotions were controlled by the liver (Gross, 1987). Many ancient cultures, including the Chinese, Indian, and Egyptian also shared the same belief (Carlson, 2014). When the Egyptians embalmed a person, the heart was saved and buried with the individual but the brain was discarded (Klein and Thorne, 2006). However, there were early Greeks, such as Hippocrates (460-377 B.C.E.) , who believed that it was the brain and not the heart where the locus of the mind resided. He wrote: "It ought to be generally known that the source of our pleasure, merriment, laughter, and amusement, as of our grief, pain, anxiety, and tears is none other than the brain. It is specially the organ which enables us to think, see, and hear......It is the brain too which is the seat of madness and delirium, of the fears and frights which assail us" (Gross, 1987, p. 843-844).

Examining the history of biopsychology allows us to understand its development over time, highlighting instances where researchers were wrong about the nature of brain-behavior relationships and revealing what we have yet to explain (Saucier and Elias, 2006).

William James in his book, The Principles of Psychology (1890), argued that the scientific study of psychology should be grounded in an understanding of biology (Walinga, 2014). Like many early psychologists, James had extensive training in physiology.

The frequently repeated claim that humans use only 10% of their brains is false.

motivated behavior (such as hunger, thirst, and sex); control of movement; learning and memory; sleep and biological rhythms; and emotion