242
Chapter 8
Emotional behavior can be studied more easily than
the anatomical systems or inner emotions because it includes
responses that can be measured externally (in terms of behav-
ior). For example, stimulation of certain regions of the lateral
hypothalamus causes an experimental animal to arch its back,
puff out the fur on its tail, hiss, snarl, bare its claws and teeth,
fl atten its ears, and strike. Simultaneously, its heart rate, blood
pressure, respiration, salivation, and concentrations of plasma
epinephrine and fatty acids all increase. Clearly, this behavior
typifi es that of an enraged or threatened animal. Moreover,
the animal’s behavior can be changed from savage to docile
and back again simply by activating different areas of the lim-
bic system, such as parts of the amygdala (
Figure 8–11
).
Emotional behavior includes such complex behaviors as
the passionate defense of a political ideology and such simple
actions as laughing, sweating, crying, or blushing. Emotional
behavior is achieved by the autonomic and somatic nervous
systems under the infl uence of integrating centers such as
those we just mentioned, and provides an outward sign that
the brain’s “emotion systems” are activated.
The cerebral cortex plays a major role in directing many
of the motor responses during emotional behavior (e.g., to
approach or avoid a situation). Moreover, forebrain structures,
including the cerebral cortex, account for the modulation, direc-
tion, understanding, or even inhibition of emotional behaviors.
Although limbic areas of the brain seem to handle inner
emotions, there is no single “emotional system.” The amyg-
dala, a cluster of nuclei deep in the tip of each temporal lobe
(see Figure 8–11), and the region of association cortex on
the lower surface of the frontal lobe, however, are central to
most emotional states (
Figure 8–12
). The amygdala inter-
acts with other parts of the brain via extensive reciprocal con-
nections that can infl uence emotions about external stimuli,
decision making, memory, attention, homeostatic processes,
and behavioral responses. For example, it sends output to the
hypothalamus, which is central to autonomic and hormonal
homeostatic processes.
The limbic areas have been stimulated in awake human
beings undergoing neurosurgery. These patients reported
vague feelings of fear or anxiety during periods of stimulation
to certain areas. Stimulation of other areas induced pleasur-
able sensations, which the subjects found hard to defi ne pre-
cisely. The cerebral cortex, however, elaborates the conscious
experience of inner emotion.
Altered States of Consciousness
States of consciousness may be different from the commonly
experienced ones like wakefulness and drowsiness. Other, more
bizarre sensations, such as those occurring with hypnosis,
mind-altering drugs, and certain diseases, are referred to as
altered states of consciousness.
These altered states are also
characteristic of psychiatric illnesses.
Schizophrenia
One of the diseases that induces altered states of consciousness
is
schizophrenia,
a disease in which information is not prop-
erly regulated in the brain. The amazingly diverse symptoms
Frontal lobe
Thalamus
Olfactory bulb
Region of
nucleus accumbens
Amygdala
Hippocampus
Septum
Figure 8–11
Brain structures involved in emotion, motivation, and the affective
disorders. The limbic system is shaded purple.
From:
Brain, Mind, and Behavior
by Floyd E. Bloom and Arlyne Lazerson. Copyright © 1985,
1988 by Educational Broadcasting Corporation. Reprinted by permission of W. H. Freeman and
Company.
Figure
8–11
physiological
inquiry
What may have favored the evolution of emotions?
Answer can be found at end of chapter.
Figure 8–12
Computer image showing areas of neural activity during a sad
thought.
Marcus E. Raichle, MD, Washington University School of Medicine.
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