74 CHAPTER 2
PONS The pons is the larger “swelling” just above the medulla. This term means
“bridge,” and the pons is indeed the bridge between the cerebellum and the upper
sections of the brain. As in the medulla, there is a crossover of nerves, but in this case it
is the motor nerves carrying messages from the brain to the body. This allows the pons
to coordinate the movements of the left and right sides of the body. (It will be useful
to remember these nerve crossovers when reading about the functions of the left and
right sides of the brain in a later part of this chapter.) The pons also influences sleep,
dreaming, and arousal. The role that the pons plays in sleep and dreams will be dis-
cussed in more detail in Chapter Four. to Learning Objective 4.7.
THE RETICULAR FORMATION The reticular formation (RF) is a network of neurons
running through the middle of the medulla and the pons and slightly beyond. These
neurons are responsible for people’s ability to generally attend to certain kinds of
information in their surroundings. Basically, the RF allows people to ignore constant,
unchanging information (such as the noise of an air conditioner) and become alert to
changes in information (for example, if the air conditioner stopped, most people would
notice immediately).
The reticular formation is also the part of the brain that helps keep people alert and
aroused. One part of the RF is called the reticular activating system (RAS), and it stimulates
the upper part of the brain, keeping people awake and alert. When a person is driving and
someone suddenly pulls out in front of the vehicle, it is the RAS that brings that driver
to full attention. It is also the system that lets a mother hear her baby cry in the night,
even though she might sleep through other noises. The RAS has also been suggested
by brain-scanning studies as a possible area involved in attention-deficit/ hyperactivitypons
the larger swelling above the medulla
that relays information from the cor-
tex to the cerebellum, and that plays a
part in sleep, dreaming, left-right body
coordination, and arousal.
reticular formation (RF)
an area of neurons running through
the middle of the medulla and the
pons and slightly beyond that is
responsible for general attention,
alertness, and arousal.
Figure 2.12 Major Structures of the Human Brain