Invitation to Psychology

Chapter 4 Neurons, Hormones, and the Brain 135

The Hippocampus

The shape of the hippocampus must have re-

minded someone of a sea horse, for in Latin,

that is what its name means. This structure com-

pares sensory information with what the brain has

learned to expect about the world, and when a

match occurs, the hippocampus tells the reticular

activating system to “cool it.” There’s no need for

neural alarm bells to go off every time a car goes

by, a bird chirps, or you feel your saliva trickling

down the back of your throat.

The hippocampus has also been called the

“gateway to memory” because it is critical in

the formation of long-term memories for facts,

events, and spatial relationships. It enables us

to take in and combine different components

of an experience—sights, sounds, feelings—and

bind them together into one “memory,” even

though the individual components are ultimately

stored in the cerebral cortex, which we will

be discussing shortly. When you recall meet-

ing someone yesterday, various aspects of the

memory— information about the person’s greet-

ing, tone of voice, appearance, and location—are

probably stored in different locations in the

cortex. But without the hippocampus, the infor-

mation would never get to these destinations.

This structure is also involved in the retrieval of

information during recall.

The Cerebrum Lo 4.12, Lo 4.13

At this point in our tour, the largest part of the

brain still looms above us. It is the cauliflower-

like cerebrum, where the higher forms of thinking

take place. The complexity of the human brain’s

circuitry far exceeds that of any computer in ex-

istence, and much of its most complicated wiring

is packed into this structure. Compared to many

other creatures, we humans may be ungainly,

feeble, and thin-skinned, but our well-developed

cerebrum enables us to overcome these limita-

tions and creatively control our environment (and,

some would say, to mess it up).

The cerebrum is divided into two separate

halves, or cerebral hemispheres, connected by a

large band of fibers called the corpus callosum.

In general, the right hemisphere is in charge

of the left side of the body and the left hemi-

sphere is in charge of the right side of the body.

The two hemispheres also have somewhat dif-

ferent tasks and talents, a phenomenon known as

lateralization.

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hippocampus A brain

structure involved in the

storage of new informa-

tion in memory.

cerebrum [suh-ree-

brum] The largest brain

structure, consisting of

the upper part of the

brain; divided into two

hemispheres, it is in

charge of most sensory,

motor, and cognitive pro-

cesses; from the Latin for

“brain.”

cerebral hemispheres

The two halves of the

cerebrum.

corpus callosum

[Core-puhs cah-LoW-

suhm] The bundle of

nerve fibers connect-

ing the two cerebral

hemispheres.

lateralization

Specialization of the two

cerebral hemispheres for

particular operations.

The amygdala

The amygdala (from the ancient Greek word for
“almond”) is responsible for evaluating sensory
information, quickly determining its emotional
importance, and contributing to the initial deci-
sion to approach or withdraw from a person or
situation (see Chapter 13). Because it assesses
danger and threat, it has sometimes been called
the brain’s “fear center,” but it is more than that.
Your amygdala rapidly evaluates incoming stim-
uli for their fit with your current psychologi-
cal state and even your core personality traits,
responding to positive, negative, or even just
plain interesting stimuli accordingly. If you’re
extroverted, your amygdala might respond more
actively to photographs of happy people than it
would if you were shy; and when you’re hun-
gry, your amygdala is likely to respond to food
(Cunningham & Brosch, 2012). The amygdala
also plays a role in mediating anxiety and depres-
sion, and in forming and retrieving emotional
memories.

amygdala [uh-Mig-

dul-uh] A brain structure

involved in the arousal

and regulation of emotion

and the initial emotional

response to sensory

information.

Hypothalamus

Pituitary gland

Hippocampus

Amygdala