Invitation to Psychology

Chapter 4 Neurons, Hormones, and the Brain 129

injury. Another is to stimulate the brains of patients

having brain surgery to try to identify the func-

tions of various areas. But both of these methods

are restricted to brains that have been damaged.

Fortunately, neuroscientists have a growing number

of other tools for studying healthy human brains.

One general approach is to do something

that affects specific brain areas and then observe

the consequences for behavior. This approach

includes these two methods:

•   Transcranial magnetic stimulation (TMS) is a rela-

tively new method that stimulates or temporar-

ily disrupts specific neural circuits by delivering

a large current through a wire coil placed on a

person’s head. The current produces a strong

magnetic field, which causes neurons under the

coil to fire. TMS can be used to produce motor

responses (say, a twitch in the thumb or a knee

jerk) but researchers also use it to briefly disrupt

neural circuits during specific tasks and study

the behavioral effects. The drawback of this

method is that when neurons fire, they cause

many other neurons to become active too, so it

can be hard to tell which neurons are critical for

a particular task. Still, TMS has been useful for

transcranial magnetic

stimulation (TMS)

A method of stimulat-

ing brain cells, using a

powerful magnetic field

produced by a wire coil

placed on a person’s

head; it can be used by

researchers to temporar-

ily disrupt neural circuits

during specific tasks.

You are about to learn...

• ways of peering inside the brain.

• what brain scans can tell us.

• the limitations of brain scans as a way of
understanding the brain.

Mapping the Brain Lo 4.8

We come now to the main room of the nervous
system “house”: the brain. A disembodied brain
stored in a formaldehyde-filled container is a
putty- colored, wrinkled glob of tissue that looks
a little like an oversized walnut. It takes an act
of imagination to envision this modest-looking
organ writing Hamlet, discovering radium, or in-
venting the paper clip.
When researchers work with animals, they
sometimes surgically remove or disable a brain
structure, and then observe the effects on behavior.
This approach is called the lesion method, but of
course it cannot be used in humans. In a living per-
son, the brain is encased in a thick protective vault
of bone. How, then, can scientists study it? One ap-
proach is to study patients who have had a part of
the brain damaged or removed because of disease or

Recite & Review

Recite: Fire up your neurons so you can say as much as possible about glia, neurons, nerves, neuro-

genesis, stem cells, synapses, neural impulses, neurotransmitters, hormones, and neuromodulators.

Review: Next, go back and reread this section. There was a lot in it; what did you miss?

Now get your glutamate going by taking this Quick Quiz:

A. Which word in parentheses better fits each of the following definitions?

1. Basic building blocks of the nervous system (nerves, neurons)


2. Cell parts that receive nerve impulses (axons, dendrites)


3. Site of communication between neurons (synapse, myelin sheath)


4. Opiatelike substance in the brain (dopamine, endorphin)


5. Chemicals that make it possible for neurons to communicate (neurotransmitters, hormones)


6. Hormone closely associated with emotional excitement (epinephrine, estrogen)
   B. Kristen is having a hard time in college and is feeling pretty depressed about it. She starts see-
   ing ads for a new drug that claims it changes the levels of several neurotransmitters thought
   to be involved in depression. Based on what you have learned, what questions should Kristen
   ask before deciding whether to ask her doctor to prescribe it for her?
   Answers:

Study and Review at mypsychlab

Kristen might want to ask, B. epinephrine6. neurotransmitters5. endorphin4. synapse3. dendrites2. neurons1. A.

among other things, about side effects (each neurotransmitter has several functions, all of which might be affected by the

drug); evidence that the drug not only works, but is also more effective than older drugs; whether there is any reason to believe

that her own neurotransmitter levels are abnormal; and whether she should consider ways of coping with her college problems

before trying any drug.