Psychology2016

76 CHAPTER 2

brain and spinal cord, we will focus on the subcortical structures that have been collec-

tively referred to as the limbic system. (See Figure 2.13.)

The limbic system (the word limbic means limbus or “margin,” referring to a bor-

der around something, and these structures are found between the upper brain and brain

stem) includes the thalamus, hypothalamus, hippocampus, amygdala, and the cingulate

cortex. In general, the limbic system is involved in emotions, motivation, memory, and

learning.

THALAMUS The thalamus (“inner chamber”) is in some ways similar to a triage* nurse.

This somewhat round structure in the center of the brain acts as a kind of relay station for

incoming sensory information. Like a nurse, the thalamus might perform some process-

ing of that sensory information before sending it on to the part of the cortex that deals

with that kind of sensation—hearing, sight, touch, or taste. Damage to the thalamus

might result in the loss or partial loss of any or all of those sensations. Recent research

has also suggested the thalamus may affect the functioning of task-specific regions of

the cortex. For example, a study of children with dyslexia found abnormal connections

between the thalamus and brain areas associated with reading behavior (Fan et al., 2014).

The sense of smell is unique in that signals from the neurons in the sinus cavity go

directly into special parts of the brain called olfactory bulbs, just under the front part of

the brain. Smell is the only sense that does not have to first pass through the thalamus.

HYPOTHALAMUS A very small but extremely powerful part of the brain is located just

below and in front of the thalamus (see Figure 2.13). The hypothalamus (“below the

inner chamber”) regulates body temperature, thirst, hunger, sleeping and waking, sexual

activity, and emotions. It sits right above the pituitary gland. The hypothalamus controls

the pituitary, so the ultimate regulation of hormones lies with the hypothalamus.

HIPPOCAMPUS Like many structures in the brain, the hippocampus was named

based on its appearance. Hippocampus is the Greek word for “seahorse,” and it was

limbic system
a group of several brain structures
located primarily under the cortex and
involved in learning, emotion, mem-
ory, and motivation.

thalamus
part of the limbic system located in
the center of the brain, this structure
relays sensory information from the
lower part of the brain to the proper
areas of the cortex and processes some
sensory information before sending it
to its proper area.

*triage: a process for sorting injured people into groups based on their need for, or likely ben-

efit from, immediate medical treatment.

hippocampus
curved structure located within each
temporal lobe, responsible for the forma-
tion of long-term declarative memories.

hypothalamus
small structure in the brain located
below the thalamus and directly above
the pituitary gland, responsible for
motivational behavior such as sleep,
hunger, thirst, and sex.

olfactory bulbs
two bulb-like projections of the brain
located just above the sinus cavity
and just below the frontal lobes that
receive information from the olfactory
receptor cells.

Figure 2.13 The Limbic System