UNIT OBJECTIVES
Become aware of the contributions of neuroscience to adolescent research.
Distinguish between various areas of the brain and their functions.
Understand the concept of Executive Function.
Recognize implications of brain plasticity research.
Identify contemporary methods of brain research.
Recognize present-day impediments to human neuroscience research.
It is perhaps the most complex structure in the known universe. Although it has been dissected for at least 2500 years of recorded history, most of its functioning remains a secret. It has only been recently that new techniques have been developed to directly study the brain.
We know that the brain communicates with itself and other parts of the body through neurons, which are special cells. These cells fire or are released by chemicals called neurotransmitters. This is how information is transmitted. We have about 87 billion neurons in our adult brain. The way that they could link up is uncountable.
Neurons tend to be specific. This means that a neuron fires for only one particular neurotransmitter. It will usually not fire when exposed to a different neurotransmitter. Some neurotransmitters act as helpers and speed up the firing process. Some act as gatekeepers and slow down or inhibit firing and transmission.
There are over 100 different neurotransmitters that have been identified. However, neuroscientists believe that there are likely many more. Some are very common and are located throughout the brain. Others have very specialized functioning.
Certain areas of the brain may be rich in specific receptors for certain types of neurotransmitters. For example, the frontal lobes, described later in this unit, are rich in norepinephrine receptors. Therefore, the neurons will fire only when they encounter norepinephrine and not other neurotransmitters.
Certain neurotransmitters are located throughout the brain. For example, GABA (abbreviated for Gamma-aminobutyric acid) is a neurotransmitter that inhibits or slows reactions. It is located in almost all brain areas. Glutamate is a neurotransmitter that speeds up reactions. It also is located across the brain in every area.
Some neurotransmitters have one function in one portion of the brain and a different one in another. Dopamine is associated with reward and motivation in the brain’s frontal areas and movement in the midbrain. These two tasks are entirely different and rely on different brain circuits. Dopamine neurons are also critical in the visual system, where they play a still different role.
Furthermore, neurons may have subtypes. GABA has at least six subtypes that have different roles. Dopamine has at least five subtypes. Often these work in coordination so that when one subtype of receptor fires, another is inhibited.
BRAIN ANATOMY
There are many ways to subdivide the brain. Many clinicians and researchers divide the brain into three essential parts: the brain stem, cerebellum, and cerebral hemispheres. Each piece has a spe