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Cognitive Function

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					Enabling America: Assessing the
Role of Rehabilitation Science and
Engineering Institute of Medicine
             (1997)
Enabling America: Assessing the Role of Rehabilitation Science and Engineering
Institute of Medicine (1997)

Chapter 5
Functional Limitations Research in Rehabilitation Science and Engineering
Cognitive Function

Relationship of Impairment and Functional Limitation

The performance of everyday activities is supported by a number of physiological and
psychological processes. Cognition represents one of these processes that guides individuals
as they acquire and use information to support their actions. Cognition at the impairment
level involves the mechanisms of language comprehension and production, pattern
recognition, task organization, reasoning, attention, and memory (Duchek, 1991). When
these mechanisms are intact, they support the person in learning, communicating, moving,
and observing. When the mechanisms are deficient, they create functional limitations for
individuals who require rehabilitation services to learn strategies to bypass the deficit or
compensate for the loss, or both. They also create functional limitations for the families of
such individuals.

Cognitive problems are common following stroke or head injury in people with Parkinson's
and Alzheimer's disease and in some people with multiple sclerosis and other chronic
conditions. It is the beginning of a new era in the study of cognition as ''we understand how
experiences generate changes in the nervous system that shape our language, our visual
world, our coordinated movements, our cognition" (Merzenich et al., 1993, p. 17). It should
be the goal of rehabilitation to minimize the consequences of brain injury in the lives of
those who suddenly are impaired by difficulties in living, social interaction, family life, and
vocational and educational pursuits. The major cognitive deficits that create functional
limitations are described below.

Aphasia is the term attributed to difficulties with language comprehension and expression. It
is the absence or impairment of the ability to communicate through speech, writing, or
signing and may limit the person's ability to comprehend or express language making it very
difficult for the person to communicate wants, needs, and ideas to others.

Agnosia refers to problems with pattern recognition. Agnosia can impair the recognition of
objects, facial discrimination (Allender and Kaszniak, 1989), and the recognition of voice
tone (Eslinger and Damasio, 1986), making it very difficult to recognize familiar people and
voices and common objects such as a fork, toothbrush, or razor. Agnosia presents a difficult
challenge, requiring rehabilitation and education for the affected individual and the family.

Apraxia describes the deficit that occurs when an individual has difficulty in organizing and
executing purposeful movements. Functional limitations occur when the person cannot
perform tasks such as putting an arm in a sleeve, reaching for a glass to take a drink, or even
putting one leg in front of the other to take a step.
Deficits in reasoning and problem solving are frequently the result of frontal and temporal lobe
damage (Mayer et al., 1986; Sullivan et al., 1989). Functional limitations occur because a
person cannot put steps together in a sequence to accomplish a goal or may not be able to
choose the items or tools necessary to perform even a simple task such as putting on a robe.
Such a deficit makes tasks such as driving a car, paying bills, preparing food, and using the
telephone problematic without training in compensatory strategies and environmental
modifications.

Executive function comprises the mental capacities required to formulate goals, plan how to
achieve them, and carry out the task effectively (Stuss, 1992). A person with impaired executive
function has a functional limitation that results in difficulty beginning an activity, monitoring
his or her performance during an activity, inhibiting irrelevant information, and maintaining
attention. This configuration of cognitive problems makes independent living and
productive work a challenge for a person who has sustained an injury and for the
rehabilitation professional who needs to help the person and the family learn how to give the
cognitive support that will make performance possible.

Memory plays a very important role in everyday functioning. Different types of memory can
be impaired, depending on the location of the brain damage. Deficits in short-term memory,
which holds information for further processing, can make new learning difficult. Individuals
with memory loss often need rehabilitation to develop strategies to access long-term
memory for personal events and general knowledge, to remember future events, and to
support the procedures required to perform an activity. Cognitive deficits that impair
memory have a profound impact on the performance of people as they recover from
physical impairments and move on to try to reestablish independence following injury or
illness.

Cognitive Issues: Engineering and Technical Advancements

Few investigators have examined if or how technical devices might be helpful in cases in
which and individual is impaired because of the loss of cognitive ability. Nevertheless, it is
known that developments in this area will not occur de novo. Positive action needs to be
taken to investigate how assistive technical aids may be useful in this area. Action needs to
come through the interaction of scientists, clinicians, and engineers. Memory aids and the
use of step-by-step instructions are areas tailor-made for providing technical assistance, and
engineering may be able to help make significant advances in this area. However,
collaboration with families and caregivers, will be necessary for the problems to be
understood and for design iterations to be based on realistic clinical experiences.

Future Needs

Cognition plays a critical role in the performance of the tasks of living. When any of these
deficits occur (and many of these deficits occur simultaneously), the person is disabled until
environmental and compensatory strategies are put in place to support him or her. During
the past decade, the emphasis on biomedical science has generated new knowledge about
brain plasticity and brain structure-function relationships. As this emphasis expands to
include issues of functional limitation and disability, it should be possible to test the
application of these findings in clinical interventions to determine how individuals with brain
injuries can improve their performance of functional, real-world tasks (e.g., self-care, meal
preparation, parenting, and employment).

Most cognitive research has been performed at the impairment level and has involved the
administration of experimental and neuropsychological tests. As more clinical studies have
been funded, investigators have learned that patterns of behavior in the real-life context
differ from those that would have been predicted from neuropsychological tests (Prigatano
and Altman, 1990). When a cognitive deficit occurs, the person also experiences changes in
emotion, social interaction, and communication; these changes can range from subtle to
severe changes and can create complex difficulties for the individual and his or her family,
coworkers, and friends.

Rehabilitation strategies to overcome problems presented by aphasia, agnosia, and apraxia
require further development and testing and will be understood more fully when scientists
and engineers interact with clinicians and patients to understand the impact of these
conditions on people's lives.

The research needed to understand the impact of cognition on the individual and society and
the potential of environmental and learning strategies on recovery and functioning is yet to
be done. It will require research of issues beyond the current biomedical mechanisms that
exist today and involve interdisciplinary teams of professionals from fields that span
education, philosophy, cognitive psychology, and neuroscience, including neurobiology and
neuroradiology. The research must also include rehabilitation professionals such as
occupational therapists, speech language pathologists, physicians, and neuropsychologists.

Such teams working together may begin to obtain an understanding of the mechanisms that
underlie the recovery and preservation of cognitive functions after brain damage. It will be
important to determine if there are aspects of affective disorders that can be distinguished
from the cognitive sequelae of acquired brain injury and determine if the brain has different
processing pathways for different types of information after brain injury (Buckner et al.,
1996). For example, it would be possible to explore whether the cerebellum's contributions
to motor learning generalize beyond the purely motor domain and whether the preserved
function demonstrated by some people with disabling conditions is mediated by sparing of
critical tissue or by compensatory neural pathways. It would be important to know how a
deficit in inhibitory control affects everyday function; that is, can different aspects of
attentional processing (e.g., divided attention, visual search, and vigilance) predict everyday
functioning, including a complex task like driving or work.

Not all disability comes from within the individual. Each person needs a supportive
environment to perform at his or her best. A study of cognition prompts investigators to ask
new questions. How does cognitive activity relate to specific environmental contexts? What
is the role of mediated action in the actual performance of cognitive and functional tasks in
people with acquired brain injury and those with no cognitive loss? What role does the
environment play in the internal representation and processing of visual information? Also,
how is it possible to prepare spouses and families for the multitude of tasks required for life
with a person who is severely disabled because of an acquired head injury?
Such questions can only be addressed when there is a level of analysis and method of
measurement that allows for the description of cognitive deficits in real-life activities.
Functional means of measuring intellect, motivation, mood, judgment, visual perception,
auditory perception, motor control, visual attention, vigilance and arousal, working memory,
procedural memory, declarative memory, and motion in context must be developed. The
challenge of preventing disabilities in those with cognitive loss cannot be left at the level of
functional limitation. New means of addressing the cognitive needs of individuals must
come to the forefront in science to reduce the devastation of a cognitive impairment on the
lives of the people and their families who must live with the consequences of the functional
limitations brought on by injury and disease.

				
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