A Look at the Brain
On the cellular level, the human brain impresses even most neuro-biologists as a nearly inconceivably complex structure. Many key questions about its function remain unanswered and are likely to remain so for a long time. Neuroscientists, however, are making impressive progress in uncovering more and more details about the brain's structure and function every year. The payoff of this research has been incremental progress in uncovering clues to what causes schizophrenia.
Like all organs in the body, each of the parts of the brain is composed of cells. In the brain, the two main types of cells are neurons and glial cells. Neurons make up the brain's gray matter. People equate gray matter with intelligence, but the cells that make up gray matter also are responsible for all kinds functions of the brain. They regulate thinking, moving, and even involuntary actions such as breathing. The other type of brain cells, glial cells, are very active supporters of neurons. Among their many jobs is to act as insulation for nerve fibers that carry electrical and chemical messages between neurons.
The Brain from the Outside
The following description provides a quick tour of brain structure by pointing out major anatomical landmarks. Remember that in a structure as complex as the human brain, many structures have multiple roles in processing information and performing intellectual tasks. The structures of the brain interact with each other through nerve fibers, creating a network like an enormously complex electrical circuit. The left side and right side of the brain also have different specialized functions. An abnormality on one side can cause different problems than does an abnormality on the other. The description in this section includes major features that have been implicated in some of the proposed causes of schizophrenia.
The most obvious structure you see when you look at the brain is the cerebral cortex. Cortex is the Latin word for “bark,” as in the bark of a tree. The wrinkly cerebral cortex, between 3/32- and 3/16-inch thick, is wrapped around deeper and evolutionarily older brain structures.
The cerebral cortex is itself subdivided into four parts — the frontal cortex, the parietal cortex, the temporal cortex, and the occipital cortex. The frontal cortex is the outermost part of the frontal lobe. The frontal lobe is located above the eyes and immediately behind the forehead. It helps people see the consequences of their actions and to plan ahead. In most people the left side of the frontal lobe helps us form words, while the right side allows us to use gestures and intonations to reflect emotional expression. The frontal lobe works with other structures in the brain to motivate us and spark initiative, among other important intellectual tasks.
Two strips of brain tissue separate the frontal lobe from the parietal lobe. The first one is a strip of motor cortex, which controls voluntary movement. Next to it is a strip of sensory cortex, which recognizes and processes feelings of touch. The parietal lobe, located about three-quarters of the way toward the back of the brain, processes aspects of language, touch, and spatial orientation.
Researchers have discovered a link between reduced cortical thickness and the development of schizophrenia. This is apparently connected to cognitive problems that are related to schizophrenia, including attention deficits and impaired memory.
The temporal lobes lie under the skull opposite the temples and ears. They play an important role in memory, speech, and emotions. Parts of the temporal lobes are reported to be smaller in some patients with schizophrenia.
The occipital lobes at the very back of the brain process visual information. Tucked underneath the occipital lobe is the cerebellum, a structure that assists in controlling movements and carrying out tasks that depend on precise timing, as well as language and other intellectual functions.
The Brain from the Inside
Deeper layers below the cortex are descriptively called sub-cortical structures. These include the basal ganglia, which, among other functions, help regulate movement. The loss of certain neurons in part of the basal ganglia is the cause of Parkinson's disease. Another subcortical structure, the pons, has bundles of nerves that connect the cerebral cortex to the cerebellum and spinal cord. It plays a key role in arousal and in maintaining automatic nerve functions such as breathing and heartbeat. Each of the subcortical structures is made up of several smaller structures or groups of nerve cells that are essential for various functions involving emotions, emotional expression, language, intellect, motivation, and other aspects of behavior.
The limbic system is a part of the brain that is made of both cortical and subcortical structures. It is believed to be the site of abnormalities in several psychiatric disorders, including schizophrenia. Included in the limbic system are structures such as the hippocampus, amygdale, mammillary bodies, and thalamus, all of which are involved in functions like memory, motivation, emotional regulation, aggression, sexuality, and cognitive tasks.