But according to equipotential theory, all areas
of the brain contribute equally to overall intellec-
tual functioning (Krech, 1962). Location of injury is
secondary to the amount of brain injury. Thus, all
injuries are alike except in degree. Equipotentialists
tend to emphasize deficits in abstract, symbolic abil-
ities, which are thought to accompany all forms of
brain damage and to produce rigid, concrete atti-
tudes toward problem solving (see K. Goldstein &
Scheerer, 1941). Such views have led to the devel-
opment of tests that attempt to identify the basic
deficit common to all cases of brain damage. Unfor-
tunately, such tests have not worked well enough
for everyday clinical use (Golden, 1981).
Many investigators have been unable to accept
either localization or equipotentiality completely.
Thus, alternatives such as the one proposed by
Hughlings Jackson (Luria, 1973) have become
prominent. Although, according to Jackson, very
basic skills can be localized, the observable behavior
is really a complex amalgamation of numerous basic
skills, so the brain as an integrated whole is
involved. This functional model of the brain sub-
sumes both localization and equipotential theory.
Further, according to Luria (1973), very complex
behaviors involve complex functional systems in
the brain that override any simple area locations.
Because our ability to abstract is a complex
intellectual skill, for example, it involves many sys-
tems of the brain.
Brain damage can have many effects, involving
visual perception, auditory perception, kinesthetic
perception, voluntary motor coordination and
functioning, memory, language, conceptual behav-
ior, attention, or emotional reactions. Often, clin-
icians are called upon to determine the presence of
intellectual deterioration. This goes beyond the
measurement of present functioning because it
involves an implicit or explicit comparison to a
prior level. Generally speaking, intellectual deterio-
ration may be of two broad types: (a) a decline
resulting from psychological factors (psychosis,
lack of motivation, emotional problems, the wish
to defraud an insurance company, etc.) and (b) a
decline stemming from brain injury. Of course,
assessment would be a good deal easier if the clini-
cian had available a series of tests taken by the
patient prior to injury or illness. Such premorbid
data would provide a kind of baseline against
which to compare present performance. Unfortu-
nately, clinical psychologists seldom have such data
on the patients they most need to diagnose. They
are left to infer patients’previous level of function-
ing from case history information on education,
occupation, and other variables. Over the years,
clinicians have used such signs of premorbidBOX18-2 Focus on Clinical Applications
Personality Changes Following Brain Injury: A Case ExampleA young Vietnam veteran lost the entire right frontal
portion of his brain in a land mine explosion. His
mother and wife described him as having been a qui-
etly pleasant, conscientious, and diligent sawmill
worker before entering the service. When he returned
home, all of his speech functions and most of his
thinking abilities were intact. He was completely free
of anxiety and thus without a worry in the world. He
had become very easygoing, self-indulgent, and lack-
ing in general drive and sensitivity to others. His wife
was unable to get him to share her concerns when the
baby had a fever or the rent was due. Not only did she
have to handle all the finances, carry all the family andhome responsibilities, and do all the planning but she
also had to see that her husband went to work on time
and that he didn’t drink up his paycheck or spend it in
a foolish spending spree before getting home on Fri-
day night. For several years, it was touch and go as to
whether the wife could stand the strain of a truly
carefree husband much longer. She finally left him
after he stopped working altogether and began a
pattern of monthly drinking binges that left little of his
rather considerable compensation checks.
SOURCE: FromNeuropsychological Assessment,4th ed., by Lezak, M. D.,
Howieson, D., & Loring, D., p. 38. Copyright © 2004 by Oxford University
Press, Inc. Reprinted by permission.522 CHAPTER 18