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to cope, to stay employed, and to carry out family responsibilities and enjoy life.140

Early writers on MS often commented on cognitive and emotional changes, but in the mid-twentieth century, a pattern of denial of these features developed in the medical literature.143 Just as clinicians passed off the frequent symptoms of pain and fatigue as features of the disease, they also ignored the often seen emotional and cognitive changes (Jock Murray, personal communication). Donald Paty (personal communication) noted that there was a negative reaction to his suggestions in the 1970s that cognitive dysfunction should be a focus of study by the National MS Society. At the time, it was estimated that only 5 percent of MS patients might incur cognitive change, and it was argued that cognitive change was relatively unimportant in MS.143 By the 1990s, those views had changed, and in 1992, the MS Society and the International Federation of Multiple Sclerosis Societies jointly held a symposium on “Neurobehavioral Disorders in MS: Diagnosis, Underlying Pathology, Natural History and Therapeutics.” Cognitive changes are now estimated to occur in about 43 percent of MS cases.54

The conviction that cognitive changes must be selectively analyzed and distinguished from other phenomena such as depression and fatigue has emerged only in the last few decades. Standard psychological tests, however, are not very effective in identifying the type of changes that occur in MS. Rao, LaRocca, Fischer, Peyser, and many others have recently made considerable progress in adapting tests that can detect the specific changes seen in this disease,54,57,130 yet much more remains to be done. Paradoxically, as we are learning to separate and more effectively measure the cognitive changes and the affective changes, this separation has made it possible to learn how they are so often linked (Jock Murray, personal communication).

Cognitive changes in MS generally are not global, but are most often circumscribed to specific processes. Learning, recall of new information, and speed of information processing are affected most often; deficits in visuospatial abilities and executive functions such as reasoning, problem solving, and planning are also common.54 Performance accuracy is less affected, but it appears affected if timed tests are used.41 Once cognitive impairment is present, it does not often remit (reviewed in 1999 by Fischer54).

Poor memory is a common complaint among MS patients.3 Depending on sample selection methods and criteria used to define impairment, approximately 20 to 42 percent of MS patients have some deficit in their free recall of recently learned verbal and visual material (reviewed in 1994 by Fischer et al.56). Although memory deficits are common, certain processes remain intact. For example, the rate of learning, the likelihood of remembering a specific item based on when it was presented, and the ability to detect semantic characteristics of the material to be learned are preserved in all but the most impaired MS patients. Implicit memory, or the ability to learn new information or skills without explicitly attending to it, is also preserved. Recognition of recently learned information

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