The brain has been misunderstood for millennia. It was not always believed to be the controller of our thoughts, emotions, and movements. In antiquity, the localization of the soul was thought to be one of the ventricles (a space in the brain containing cerebrospinal fluid), and not inside the brain itself! Many centuries later scholars proposed that the gray matter of the brain (brain tissue) actually produced the functions of the brain. Franz Gall (1758-1828) was one of the first to propose that brain functions were localized to certain areas of the brain. From dissections of cadavers' brains, surgical manipulation of brain tissue, brain lesions in living people, and functional brain imaging, we have a greater understanding of the brain and its functions. However, much about this complex organ remains to be discovered.

The brain is split into two hemispheres (right and left) with each having dominance over specific functions. They are connected by tracts of neurons (brain cells), allowing them to communicate and modify the brain's final output. The brainstem, cerebellum, and spinal cord comprise the other members of the central nervous system, which are interconnected and communicate with the cerebral hemispheres.

The cerebral hemispheres can be functionally split into 4 lobes on either side: the frontal lobes, the parietal lobes, the temporal lobes, and the occipital lobes. The frontal lobes modify higher order functions, such as, planning, reasoning, judgment, and impulse control. The temporal lobes help us hear, talk, and remember things. The parietal lobes process sensory information and provide spatial orientation. The occipital lobes give us vision. They all work together to integrate the information that each one receives and produces.

Although everyone's brain is set up in essentially the same fashion, we all have distinctive personalities and experiences. The difference must lie in the function and connection of the brain cells. The brain cells communicate with neurotransmitters, which are substances released by a brain cell when it is activated. If an imbalance (deficiency or excess) exists, brain functions will be altered.

Many neurologic and psychiatric disorders develop due to disconnection of parts of the brain due to disease or disarray of the neurotransmitter system. When large, confluent areas of the brain are damaged from stroke, neurodegeneration, tumor, or trauma, specific syndromes are produced, resulting in abnormal behaviors or motor dysfunction. Cerebrovascular accidents, Frontotemporal Lobar Degeneration, Glioblastoma multiforme tumors, and sequelae from closed head injuries are examples. Neurotransmitters that are not made in enough quantity, such as dopamine, acetylcholine, or serotonin, lead to diseases like Parkinson's disease, Alzheimer's disease, or depression. Excess dopamine is produced in the brains of persons with Schizophrenia.

Treatments for these diseases are becoming more specific and targeted due to our understanding of the functional anatomy and physiology of the brain and from the information learned through functional imaging of the brain in action. Newer technologies are allowing researchers to see how the neurons and the neurotransmitters actually function inside the living brain and how disease processes affect their function.