Limbic System and Emotions

The limbic system is the label that applies to regions of the diencephalon
such as the thalamus and hypothalamus that are associated with behaviors
such as emotions, learning, and sexual behavior. Stimulation of various areas
within the limbic system during surgery has resulted in the patient feeling
a variety of conflicting emotions, such as happiness and pleasure or fear
and depression, depending upon the area being tested.
Some of these emotions or behaviors are associated with survival. For example,
stimulation of certain areas results in feelings of rage or sexual excitement.
Such patterns of behavior, accompanied by increased heart rate
and blood pressure, have suggested that the limbic system plays a role in the
“fight or flight” phenomenon.
Neurotransmitters such as serotonin and dopamine are believed to play
roles in these behaviors. The effects of recreational drugs on behaviors and
emotions may in part be due to the similarity of action between these drugs
and neurotransmitters. For example, the high associated with amphetamine
use or abuse may result from stimulation of these neurotransmitters. Cocaine
blocks the movement of dopamine, resulting in the continual activation
of neurons which use dopamine as a neurotransmitter. The addiction
associated with cocaine results from alterations in the affected neurons, resulting
in an increase in need for stimulation by these pathways.
The disorder schizophrenia may also be the result of impaired transmission
of dopamine. The symptoms of schizophrenia—hallucinations or delusions—
may be decreased through the use of drugs which inhibit dopamine
release. Likewise, drugs which stimulate dopamine activity increase the severity
of symptoms.