289

CHAPTER

19

Learning, Memory,

Language, & Speech

OBJECTIVES

After studying this chapter, you should be able to:

■

Describe the various types of long-term memory.

■

Define synaptic plasticity, long-term potentiation (LTP), long-term depression

(LTD), habituation, and sensitization, and their roles in learning and memory.

■

List the parts of the brain that appear to be involved in memory in mammals and

summarize the proposed role of each in memory processing and storage.

■

Describe the abnormalities of brain structure and function found in Alzheimer disease.

■

Define the terms categorical hemisphere and representational hemisphere and

summarize the difference between these hemispheres.

■

Summarize the differences between fluent and nonfluent aphasia, and explain

each type on the basis of its pathophysiology.

INTRODUCTION

A revolution in our understanding of brain function in

humans has been brought about by the development and

widespread availability of
positron emission tomographic

(PET) scanning, functional magnetic resonance imaging

(fMRI),
and related techniques. PET is often used to measure

local glucose metabolism, which is proportionate to neural

activity, and fMRI is used to measure local amounts of oxy-

genated blood. These techniques make it possible to deter-

mine the activity of the various parts of the brain in

completely intact normal humans and in humans with many

different diseases. They have been used to study not only sim-

ple responses but complex aspects of learning, memory, and

perception. An example of the use of PET scans to study the

functions of the cerebral cortex in processing words is shown

in Figure 19–1. Different portions of the cortex are activated

when hearing, seeing, speaking, or generating words.

Other techniques that have provided information on corti-

cal function include stimulation of the exposed cerebral cortex

in conscious humans undergoing neurosurgical procedures

and, in a few instances, studies with chronically implanted

electrodes. Valuable information has also been obtained from

investigations in laboratory primates, but it is worth remem-

bering that in addition to the difficulties in communicating

with them, the brain of the rhesus monkey is only one-fourth

the size of the brain of the chimpanzee, our nearest primate

relative, and the chimpanzee brain is in turn one-fourth the

size of the human brain.

LEARNING & MEMORY

A characteristic of animals and particularly of humans is
the ability to alter behavior on the basis of experience.

Learning

is acquisition of the information that makes this

possible and

memory

is the retention and storage of that

information. The two are obviously closely related and

should be considered together.