Studies in Age-Related Cognition

In examining cognitive changes in aging populations, aside from the theoretical
debates, researchers have reported that cognitive processes progressively
decline as chronological age advances. Studies have tended to describe
the cognitive declines as gradual and general, rather than being
attributable to discrete cognitive losses in specific areas of functioning.
Several studies have supported the existence of age-related cognitive decline,
while other studies dispute the severity of such declines. Research interest
is increasing in the areas of identifying factors related to cognitive decline
and interventions to abate them. Under the direction of Ronald C.
Petersen and Michael Grundman, the National Institute on Aging is studying
whether daily doses of vitamin E or donepezil can prevent those with
mild cognitive impairment from developing Alzheimer’s disease. Other
studies are investigating cholinesterase inhibitors and anti-inflammatory
agents as a means of slowing the progression of mild cognitive impairment.
Psychologists who studied memory change identified diminished memory
capacity in the elderly as attributable to a number of processes, such as
slowed semantic access and a reduced ability to make categorical judgments.
Other researchers concluded that older subjects were slower in mental operations
but were not less accurate. Some researchers hypothesized that
slower speed tied up processing functions, resulting in apparent memory
impairment. Still others hypothesized that older adults have more trouble
with active memory tasks because of increased competition for a share of
memory processing resources, whereas others linked the aged’s poor performance
on working memory tasks to an actual deficiency in processing resources.
Finally, some researchers concluded that older adults might simply
have less mental energy to perform memory tasks. These studies accept
gradual memory decline, or a slowing of processing, as a normal by-product
of aging.
There are some who believe that mild cognitive impairment is a neurological
disorder. This belief stems from the identification of atrophy of the
left medial lobe and small medial temporal lobe, low parietal/temporal perfusion,
and asymmetry of the brain as revealed by computed tomography.
One study identified those with small hippocampi as prone to developing
Alzheimer’s disease. Additionally, electroencephalogram tracings of the
brains of patients with mild cognitive impairment and patients with Alzheimer’s
disease showed similarities.
R. A. Hock, B. A. Futrell, and B. A. Grismer studied eighty-two elderly persons,
from sixty to ninety-nine years of age, who were living independently.
These normal adults were tested on a battery of eight tasks that were selected
to reflect cognitive functioning, particularly measuring primary and secondary memory, memory for nonverbal material, span of attention, the
capacity to divide attention among competing sources of stimulation, and
two motor tasks requiring psychomotor integrity. This study found a gradual,
progressive decline in cognitive functioning but found that the decline
did not reach statistically significant levels. The decline was general, suggesting
that it may have been a function of reduced attention rather than more
discrete losses. This finding appears to be consistent with the notion that
crystallized intellectual or abstract processes are well maintained across
time. There were suggestions that speed of information processing is a sensitive
measure of the aging process.
It is possible, however, that the tasks selected for this study did not discriminate
between younger and older aging adults because the tasks may be
more reliable for assessing brain injuries and psychologically impaired persons,
who were not included in the population studied. Consequently, further
studies on the same cognitive tasks with impaired aged adults would be
necessary to see if the same relationships and conclusions would apply. Individuals
with impaired cognitive functioning offer a unique opportunity to
determine if the brain continues to show the same propensity to function as
a unitary, global system as is observed with individuals who experience the
normal aging process.
Although the brain does exhibit localization of functions, with specialization
of certain brain cells for specific functions, its overall mode of operation
is as a total unit. The brain has an exceptional capacity to compensate
for the loss of some specific functions and continue the rest of its mental operations.
This capacity or flexibility in brain function has been termed
equipotentiation. Further studies of individuals with brain impairments will
help to show how the brain attempts to carry out its overall functions when
more specific impairments have been sustained. When cognitive disorders
result in faulty information processing, actual observable changes may occur
in a person’s daily behavior. The previously neat person, for example,
may neglect personal hygiene. The person who previously exhibited exceptional
verbal abilities may speak in a socially inappropriate manner. The
staid conservative businessperson may act impulsively or even make unreasonable
decisions about personal finances and may show impaired social
judgment.