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Module 1.4b

Paul Bucy surgically removed a rhesus monkey’s amygdala, turning the normally ill-tempered
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animal into the mellowest of creatures. So, too, with humans. People with amygdala lesions AP Science Practice
often display reduced arousal to fear- and anger-arousing stimuli (Berntson et al., 2011). Research
One woman with an amygdala lesion, patient S. M., has been called “the woman with no Notice the phrase, “other studies PRACTICE
fear,” even if being threatened with a gun (Feinstein et al., 2013). link criminal behavior with amygdala
What, then, might happen if we electrically stimulated the amygdala of a normally dysfunction.” Because researchers
placid domestic animal, such as a cat? Do so in one spot and the cat prepares to attack, hiss- cannot ethically manipulate the Research Methods & Design
ing with its back arched, its pupils dilated, its hair on end. Move the electrode only slightly variable of amygdala dysfunction, (SP 2)
they cannot draw causal conclu-
within the amygdala, cage the cat with a small mouse, and now it cowers in terror. sions. This is an important point in (10 minutes) Understanding that
These and other experiments have confirmed the amygdala’s role in fear and rage. psychology: Correlation does not
Monkeys and humans with amygdala damage become less fearful of strangers (Harrison equal causation. the correlational method does not
et al., 2015). Other studies link criminal behav- allow for a cause-effect conclusion
ior with amygdala dysfunction (Dotterer et al., is important for students. Take time
2017; Ermer et al., 2012a).
But we must be careful. The brain is not here to point that out. Ask students
neatly organized into structures that corre- what the researchers would need
spond to our behavior categories. The amyg- to do to infer causation. In this
dala is engaged with other mental phenomena
as well. And when we feel afraid or act aggres- case, they would need to utilize
sively, neural activity occurs in many areas the experimental method by
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
of our brain — not just the amygdala. If you GK Hart/Vikki Hart/Getty Images randomly assigning participants
destroy a car’s battery, the car won’t run. But
the battery is merely one link in an integrated to conditions of an independent
system. variable and then measuring the
Copyright © Bedford, Freeman & Worth Publishers.
dependent variable. Sometimes,
The Hypothalamus as is the case here, ethics would
Figure 1.4-10
Just below (hypo) the thalamus is the hypothal- The hypothalamus not allow them to do so.
amus (Figure 1.4-10), an important link in the This small but important
command chain governing bodily maintenance. structure, colored yellow/orange
Some neural clusters in the hypothalamus influ- in this MRI scan, helps keep the
ence hunger; others regulate thirst, body tem- body’s internal environment in a
perature, and sexual behavior. Together, they help steady state.
maintain a steady (homeostatic) internal state. CONNECT 1.4-6
To monitor your body state, the hypothal-
amus tunes into your blood chemistry and any Point out to students that the
incoming orders from other brain parts. For Diomedia amygdala and the frontal lobes
example, if it picks up signals from your brain’s work together to regulate emotional
cerebral cortex that you are thinking about sex,
your hypothalamus will secrete hormones. These hormones will, in turn, trigger the pitu- responses. The amygdala supplies the
itary, which controls your endocrine system (Figure 1.4-9) to influence your sex glands to emotional feelings, while the frontal
release their hormones. These hormones will intensify the thoughts of sex in your cerebral lobes (covered later in this module)
cortex. (Note the interplay between the nervous and endocrine systems: The brain influ-
ences the endocrine system, which in turn influences the brain.) make the judgment regarding the
A remarkable discovery about the hypothalamus illustrates how progress in science often hypothalamus [hi-po-THAL- appropriate expression of emotion. It’s
occurs — when curious, open-minded investigators make an unexpected observation. Two uh-muss] a limbic system neural the frontal lobes that help us regulate
young McGill University neuropsychologists, James Olds and Peter Milner (1954), were trying structure lying below (hypo)
to implant an electrode in a rat’s reticular formation when they made a magnificent mistake: the thalamus; it directs several the emotions from the amygdala.
They placed the electrode incorrectly (Olds, 1975). Strangely, as if seeking more stimulation, maintenance activities (eating,
drinking, body temperature), helps
the rat kept returning to the location where it had been stimulated by this misplaced electrode. govern the endocrine system, and
On discovering that they had actually placed the device in a region of the hypothalamus, Olds is linked to emotion and reward.
and Milner realized they had stumbled upon a brain center that provides pleasurable rewards. CONNECT 1.4-6
Explain to your students that
The Brain: Brain Regions and Structures Module 1.4b 67
studies on rats have shown that the
hypothalamus can be divided into two
sections: the lateral side (LH), which
controls hunger, and the ventromedial
03_myersAPpsychology4e_28116_ch01_002_163.indd 67 15/12/23 9:23 AM
side (VMH), which controls satiety.
In these studies, stimulation of the
LH produced behaviors that led to
seeking out food, whereas lesions to
the VMH caused rats to overeat to the
point of obesity. This role of the
hypothalamus in hunger motivation
is discussed in greater detail in
Module 4.7c.

The Brain: Brain Regions and Structures Module 1.4b 67

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