Cognitive Rehabilitation: An Impairment-Oriented Approach Embedded in a Holistic Perspective†
George P. Prigatano, PhD
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona
†Presented at the National Institutes of Health Consensus Development Conference on Rehabilition of Persons with Traumatic Brain Injury, October, 1998
Cognitive rehabilitation is an important component of holistic approaches to neuropsychological rehabilitation. This article outlines issues involved in assessing the efficacy of cognitive rehabilitation and suggests areas of future research.
Key Words: neuropsychology, rehabilitation
Holistic approaches to neuropsychological rehabilitation consist of five interrelated activities, one of which is cognitive rehabilitation. Cognitive rehabilitation aimed at direct remediation of an impaired brain function remains controversial. Ben-Yishay and Diller concluded that “It would be premature to draw definitive conclusions regarding its validity and use for rehabilitation purposes based on current evidence” (p. 294). In a review of cognitive remediation after cerebrovascular accidents, Pliskin et al. concluded that the overall scientific evidence is at best nonconclusive and at worst negative, despite reports of positive results.
Efforts to remediate cognitive impairments have included drill and practice exercises of the function that appears to be impaired, teaching strategies to circumvent a theoretically identified component to a cognitive process considered to produce the impairment, and a “broad-band” approach that attempts to stimulate a wide variety of theoretically defined brain functions (i.e., arousal, alertness, attention, memory, and mental energy) in an effort to facilitate either the rate of recovery or the overall level of recovery. After patients undergo direct retraining for a cognitive impairment, final analyses often show only modest improvements on certain psychometric tests or tasks. Clinically, the impact of an impairment-oriented approach on daily functioning appears minimal.
Problems with Impairment Approaches to Cognitive Rehabilitation
Four major problems must be addressed to determine if cognitive rehabilitation aimed at remediating an impairment will prove effective. First, the impaired function is seldom clearly defined. Because attention is reportedly affected negatively, Ponsford and Kinsella attempted to retrain this function directly in patients with traumatic brain injuries (TBIs). Their results proved discouraging. Later, however, they redefined the problem as reflecting a disorder of speed-of-information processing.
Second, the rules that govern normal higher cerebral functions and the relationships among them are still unknown. A function rule is defined as follows: “a function f is a correspondence or relationship that pairs each member of a given set with exactly one member of another set” (p. 16). A set can be defined as numbers, geometric configurations, or neural networks responsible for emergent complex psychological functions. It is probable that direct remediation of a cognitive impairment may prove most effective when an underlying “function rule” is only slightly disturbed or indirectly rendered inoperable. When damage to the brain substantially alters a functional relationship (i.e., function rule), adaptation rather than retraining may be the most useful therapeutic approach.
If an impaired function can be defined and the variables that contribute to its function rule clarified, two other problems still need to be addressed. Evidence is needed that a patient’s brain has the necessary cortical plasticity for the “function” that is being retrained. Finally, technology that delivers retraining activities in a cost-efficient and effective manner is needed. Merzenich et al. and Tallal et al. developed an interesting prototype of how technology can be used to train children with language-based learning impairments. They identified the function that seemed to be disturbed as the encoding of phonemic aspects of sound. The children were then delivered auditory stimuli in a manner that required finer and finer temporal discriminations. The children found the tasks engaging rather than frustrating. The interventions produced greater improvements in different speech and language functions than traditional speech and language therapies.
Quality of Available Data
Research studies on the effects of direct retraining of cognitive impairments can be categorized into three broad types. The first includes retrospective clinical assessments of primarily neuropsychological and personality test scores before and after holistic milieu-oriented rehabilitation programs.[14,16] These studies are not randomized prospective investigations, and positive findings can be interpreted only as suggestive (not definitive) of their effectiveness.
The second group of studies can be classified as primarily multiple individual case designs in which baseline, intervention, and postintervention assessments are made. Such studies often report modest improvements on certain target cognitive impairments.
The third type of study is the traditional randomized group design in which subjects receive a specific treatment, no treatment, or pseudotreatment and are compared to control subjects. These studies also tend to report modest improvements on complex tasks.
Studies, however, have shown that humans can be retrained in specific skills (e.g., learning to operate a computer, improving phonemic perceptions) after brain insults. The findings support the possibility of cortical plasticity throughout the life span for certain skills (not necessarily global functions).
Clinical and Research Perspectives
The nature of higher cerebral functions is not purely cognitive; they often seem to integrate both “thinking” and “feeling.” Remediation programs must be stimulating but not frustrating. They need to build on the natural interests and strengths of patients while attempting to remediate an underlying impairment. When emotional and motivational disturbances as well as cognitive impairments are the focus of rehabilitation, psychosocial outcomes improve.[2,3,14,16,18]
In the course of clinical practice, three broadly defined “higher cerebral functions” seem amenable to direct retraining albeit the functions are difficult to measure. The first category concerns patients’ overall energy to sustain mental effort on cognitive tasks. Patients engaged in day-treatment programs are able to improve their overall cognitive energy with such interventions. The measurement of this complicated function is worth further investigation. Second, a number of severe TBI patients lack insight into their neuropsychological impairments. These patients simply do not experience their impairments in a manner similar to those around them. Clinical efforts focused on improving self-awareness appear to have been effective in some patients. When this type of treatment is successful, patients often make more appropriate choices for themselves and avoid substantial psychosocial difficulties.
Finally, speed-of-information processing is often compromised after severe TBI. Cognitive remediation tasks that attempt to improve the processing speed associated with various functions may have important consequences. For example, speed of finger tapping is related to the achievement of rehabilitation goals not only for postacute TBI patients but for individuals who have suffered acute cerebrovascular accidents. Interestingly, within the first 6 to 8 weeks of a stroke, speed of finger tapping in the so-called unaffected hand (the hand ipsilateral to the lesion) strongly correlates with the achievement of rehabilitation goals. Further exploration of how to improve speed-of-information processing and speed of motor function may prove useful.
Research on the cognitive rehabilitation of impairments in higher cerebral functions should not be abandoned even though the present utility of such treatments appears minimal. Data on the acquisition of specific skills after brain injury are encouraging. Theoretically, direct retraining of impaired cognitive functions appears to be possible. If accomplished, such retraining would help patients substantially. When clinicians attempt to retrain an underlying cognitive impairment directly, they should recall that both cognitive and affective functions are intimately interconnected and must be addressed simultaneously to maximize their usefulness for patients. As Merzenich et al. recently observed, “Cognitive neuroscience studies also reveal the most effective strategies for driving brain change. The subject must be attentive and motivated. The training must be progressive and adapted to each training subject. The training schedule must be repetitious and the training schedule intense” (p. 5). Training must also help patients adjust to their permanent disabilities by providing appropriate cognitive and psychotherapeutic methods.
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