Cognitive dysfunction is common in patients with schizophrenia, with deficits reported in a range of functions including memory, attention, executive processes, language and motor skills. (Weinberger & Gallhofer p. 295-365; Rossell & David p. 26-9) The severity of cognitive dysfunction has been shown to be an important predictor of social and occupational outcome. (Breier et al p. 239-46; Browne et al p. 118-24; Brekke et al p. 19-28) Indeed, outcome measures have been found to correlate more closely with the extent of cognitive dysfunction than with the severity of psychotic symptoms. Improvement in cognitive functioning is increasingly acknowledged as an important treatment goal in the management of schizophrenia.
Besides cognitive dysfunction, the symptoms of schizophrenia include disorders of perception, thought, motivation and social behavior. This diversity of symptoms might be understood as the result of a disturbance in a single, fundamental cognitive process. A number of models have been developed, which explain the symptoms of schizophrenia as manifestations of an underlying problem in perceiving, evaluating and retaining information. Braff (p. 233-59) has suggested, based on both clinical and neurophysiological abnormalities, that patients with schizophrenia have difficulty with the allocation of attentional resources to relevant tasks.
Goldman-Rakic and Selemon (p. 437-58) have proposed that the fundamental disturbance in schizophrenia is a defect in working memory, such that the ability to hold and utilize internal representations of the external world is impaired. A failure of the processes of perception and memory is implicated in the hypothesis of Hemsley, (139-69) which proposes that schizophrenia results from a breakdown in the normal relationship between current sensory input and stored material, so that information from experience is not used effectively to understand the present environment. Andreasen et al (p. 9985-90) have suggested that impaired connectivity between frontal, thalamic and cerebellar regions produces “cognitive dysmetria,” which results in the person with schizophrenia not being able to coordinate functions such as the perception, encoding, retrieval and prioritization of experience and information.
Green and Nuechterlein (p. 309-18) have developed a model that links neurocognitive deficits in patients with schizophrenia with treatment interventions and functional outcome. The model describes the impact of treatment factors, including conventional and novel antipsychotic drugs, anticholinergic drugs and cognitive–behavioural interventions, on cognitive function in patients with schizophrenia. Some treatment interventions have been found to produce an improvement in performance on neuropsychological tests, and it is important to understand the processes by which these performance gains can be translated into long-term reduction in disability. Green and Nuechterlein (p. 309-18) suggest that social cognition, which includes emotional perception, insight and coping strategies, may be the mediator between basic neurocognition and functional outcome.
Non-pharmacologic Way for the Treatment of Cognitive Dysfunction
Approaches to cognitive remediation in patients with schizophrenia have ranged from teaching patients how to improve their performance on a single neuropsychological test (Goldberg et al p. 1008-14) to provision of a comprehensive, intensive remediation program. (Wykes et al p. 291-307) Computer programs as well as more traditional teaching methods have been used. (Medalia et al p. 147-52) The areas of cognitive function addressed with nonpharmacologic treatments include attention, cognitive flexibility, planning and memory. The simplest method of outcome evaluation is to measure changes in neuropsychological test performance, although more studies that are recent have investigated whether undertaking some form of cognitive remediation is associated with an improved level of social functioning. (Wykes et al p. 291-307)
More sophisticated methods of teaching the WCST have also been used. Scaffolding, a process whereby assistance is given for those aspects of the task not yet learnt and gradually removed in the areas that have been mastered, and a similar method, errorless learning, have been found to be effective, with improved performance persisting at 4 weeks’ follow-up. (Young & Freyslinger p. 199-207) Clinically, it is important to know whether better performance on a neuropsychological test such as the WCST generalizes to other situations. This is unclear, since the results of two studies evaluating whether training effects across similar problem-solving tasks are generalizable, were contradictory. (Bellack et al p. 257-74)
Wiedl (p. 1411-9) has used the ability to improve performance on the WCST as a predictor of rehabilitation readiness. He found that individuals with schizophrenia who were able to learn to improve their performance on the WCST and retain this information, gained more benefit from skills-training groups (teaching medication self-management techniques and problem-solving skills) than patients who could not learn to perform better on the WCST or could not retain this information.
Several recent studies have attempted to show the effects of cognitive remediation on measures of functional outcome. Corrigan et al (p. 257-65) evaluated a memory and vigilance training program for patients with schizophrenia. The memory training included semantic elaboration, where patients retold, in their own words, the story of a social situation presented to them. The training program produced an improvement in their ability to recognize social cues in a video of a social situation. Wykes et al (p. 291-307) used a more comprehensive measure of social function, the Social Behavior Schedule, to evaluate the effectiveness of a program specifically designed for remediation of frontal/executive impairments in patients with schizophrenia. (Delahunty A, Morice p. 760-7) Compared with patients receiving intensive occupational therapy, the group receiving cognitive remediation improved more on tests of cognitive flexibility and memory and gained in self-esteem. Although no group difference in social functioning was found, patients who reached a certain threshold of improvement in cognitive flexibility tasks showed improved social functioning.
In conclusion, much of the research into cognitive remediation in patients with schizophrenia has involved teaching patients to perform particular tests more effectively, and, generally, some improvement has been found. Further research is needed to develop maximally effective teaching methods. Recent work has focused on identifying the patients who will benefit most from cognitive remediation. (Wykes et al p. 291-307) Yet, limited information is available regarding the persistence and generalizability of gains made in cognitive remediation programs and this will be crucial in evaluating their clinical utility.
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