Rehabilitation of Memory Disorders
REHABILITATION OF MEMORY DISORDERS
Memory impairment is one of the most pervasive and debilitating consequences of a range of neurological conditions, including closed-head injury, aneurysm, stroke, encephalitis, tumor, anoxia, Korsakoff's syndrome, and dementia. This inability to remember recent experiences or to acquire any new long-term memories is frequently resistant to rehabilitation. Recent empirical and theoretical advances in psychology and neuroscience, however, have broadened understanding of the cognitive and neural mechanisms of memory and have provided a new perspective on memory rehabilitation. It is now apparent that memory is not a unitary entity; it can break down in a variety of ways, and although some aspects of memory are seriously compromised, others remain unaffected. For rehabilitation to be successful, it must take account of the spared as well as the impaired cognitive and neural processes. Finding ways to tap into intact processes to accomplish the kinds of memory tasks that are impaired, however, has not been easy, and so this approach to rehabilitation remains only one of several.
Approaches to rehabilitation fall into two broad categories: those that attempt to remediate the underlying impairment and achieve broad improvements in memory and those that intervene at a behavioral level and try to achieve specific functional outcomes. The second approach has been more fruitful: patients have been able to take advantage of ways to bypass or compensate for their deficits and thus attain some level of independence in their everyday lives. But general mnemonic improvements, which might apply broadly across a range of memory situations, have proved elusive.
Practice and Rehearsal Techniques
Extensive practice or rehearsal is essential for the acquisition and retention of information by memory-impaired individuals. The effects of practice, however, are highly specific and tend not to generalize beyond the trained materials. It is, therefore, important that practice be directed towards information that is useful in everyday life. Simple repetitive exercise or rote rehearsal, however, is unlikely to achieve long-term retention. Instead, short periods of distributed practice are more effective. One such method, spaced retrieval, involves repeated practice at retrieving tobe-learned information at gradually increasing retention intervals. This technique has been successful in teaching memory-impaired patients, including those with Alzheimer's disease, various kinds of information important in their daily lives, including name-face associations, locations of objects, and aspects of orientation (Camp and McKitrick, 1992). The method may rely on residual memory function or tap into other preserved memory processes.
Teaching a variety of mnemonic strategies, including visual imagery and verbal elaboration, has achieved only spotty success with neurologically impaired patients. For many patients, the techniques are too demanding and difficult. They are often effective, however, for individuals with unilateral lesions and material-specific deficits. People with left-hemisphere lesions and problems in verbal memory may benefit from visual-imagery strategies, whereas those with right-hemisphere lesions and difficulties in visuo-spatial memory may find verbal methods, such as first-letter cuing, more useful. Like rehearsal strategies, mnemonic techniques can be used to help people acquire specific pieces of new information important in their daily lives, but they do not provide broad-based memory improvements because of their lack of applicability to new materials and contexts. Because mnemonic strategies are useful only for mildly impaired patients, these strategies likely rely on residual memory function (Glisky and Glisky, 2002).
External Aids and Environmental Supports
Compensating for memory impairments has often involved providing external aids for remembering, such as notebooks and diaries; bell timers and alarm watches; environmental restructurings such as labels and directions; and, most recently, microcomputers, recorders, pagers, and electronic organizers. Although the simplest of these—labels and signage—can be used effectively by even the most severely impaired individuals, aids such as notebooks, computers, and electronic organizers require training and extensive practice and may be beneficial only for mildly impaired individuals; more severely impaired patients may be unable to learn how to use these devices. Barbara Wilson and her colleagues (2001) have reported considerable success with a simple paging device that requires little learning, can be used effectively by even very severely impaired patients, and can be programmed to meet the needs of individual patients. The device provides people with needed information at various times of the day, enabling them to perform important daily functions that they would otherwise be unable to remember.
The method of vanishing cues was developed expressly to take advantage of the implicit learning and memory abilities that are spared in amnesic patients in order to teach them useful information and skills. This technique, which involves the gradual withdrawal of cues across learning trials, was thought to capitalize on patients' preserved abilities to retrieve recently presented information in response to fragment cues. Using this method, Glisky and colleagues (1994) demonstrated that even people with serious memory impairments could acquire a variety of domain-specific skills and knowledge, including computer procedures, data entry, database management, and word-processing. Patients learned this information despite having little or no memory of the occasions of learning and were later able to use it in the workplace or in the home.
Wilson and colleagues (Evans et al., 2000) showed that preventing errors during learning facilitates the acquisition of new information in people with memory disorders. Errorless learning has been effective in teaching memory-impaired patients a range of useful information, including names, the use of a memory notebook and an electronic memory aid, and items of general knowledge. Other methods, such as vanishing cues and spaced retrieval in combination with errorless learning, may prove beneficial, particularly for very severely impaired patients, who have to rely on preserved implicit memory.
Current understanding of memory disorders favors a rehabilitation strategy that focuses on achieving improved functioning rather than on treating underlying impairment. Because the benefits are specific and limited, it is important to ensure that rehabilitation is directed towards solving real-world problems. The finding of preserved-memory abilities in amnesic patients suggests that there may be alternative routes to usable memory if ways could be found to recruit these intact cognitive and neural structures. Although relatively little is known about the reorganization of brain function after damage, recent neuroimaging studies have suggested that such reorganization is possible and may have functional consequences (Grady and Kapur, 1999). Finding ways to encourage reorganization and to tap into preserved functions will be important tasks for future research in memory rehabilitation.
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Grady, C. L., and Kapur, S. (1999). The use of neuroimaging in neurorehabilitative research. In D. T. Stuss, G. Winocur, and I. H. Robertson, eds., Cognitive Neurorehabilitation. Cambridge UK: Cambridge University Press.
Wilson, B. A., Emslie, H., Quirk, K., and Evans, J. (2001). Reducing everyday memory and planning problems by means of a paging system: A randomized control crossover study. Journal of Neurology, Neurosurgery, and Psychiatry 70, 477-482.