The relationship between intellectual functioning and memory impairment in schizophrenia. Soler, M.J.(1), Ruiz, J.C.(1), Tomás, P.(2), Fuentes, I.(1) & Dasí, C.(1) (1) School of Psychology. University of Valencia (Spain) (2) Center for Rehabilitation and Social Integration (CRIS) in Valencia (Spain) 26th International Congress of Applied Psychology. Athens, July 2006 INTRODUCTION Memory deficits have been considered a specific dysfunction in schizophrenia [1,2]. Most of the empirical evidence of such deficits comes from studies that use explicit verbal and non verbal recall and recognition, working memory, and semantic memory tasks. Their neural mechanisms have also been established [3]. However, literature has paid less attention to the study of everyday memory impairment and implicit memory deficits in these patients. According to McKenna et al. poor performance in some explicit memory tasks can reflect the tendency to general intellectual impairment in schizophrenic patients [4]. Intellectual deficit is often considered to characterize schizophrenia because numerous studies have reported that patients with schizophrenia have a lower IQ in comparison with normal controls; however, other studies have shown that intellectual decline after the onset of schizophrenia is not general, and a relevant proportion of patients have a normal IQ [5,6]. The variability observed in the general intellectual functioning of patients suggests that, establishing different subgroups of subjects using IQ level as criterion could help to understand the role that intellectual functioning plays in memory impairments [7]. If memory performance is related to IQ, then we can expect lower scores on memory tests in patients that have a low IQ than in patients with normal IQ. Studying these differences it may be possible to determine which memory aspects are jointly impaired and which are uniquely affected for each IQ group. In this study, we analyze the role of IQ in these deficits, assessing a wide range of memory areas: explicit tests on working memory capacity, executive functioning, attention and speed of information processing, recall and recognition tasks; implicit memory tests such as word fragment completion and word production from semantic categories; and finally a memory test to detect and monitor everyday memory problems. General intellectual functioning of patients was also measured using the Wechsler Adult Intelligence Scale (WAIS-III). The IQ scores were used to classify subjects in to two groups: patients who were intellectually intact by having IQs within 1 SD of the population mean (IQ scores of 85 or greater), and patients who were intellectually impaired by having IQs below 85. To determine the possible influence of IQ on memory performance, we compare the pattern of results of both patient groups on the different memory tests. METHOD Participants and Procedure Forty-four outpatients from the Centre for Rehabilitation and Social Integration at Valencia, Spain, participated in the study. They had been diagnosed with schizophrenia according to DSM-IV criteria. All the subjects provided written informed consent before participating in the study. All the patients were treated with typical or atypical antipsychotic medication (see Table 1). A short form of the Spanish version of the Wechsler Adult Intelligence Scale (WAIS-III) with documented psychometric properties was administered to estimate their current IQ level. All the participants completed a battery of neuropsychological tests (see Table 2) administered and scored by trained psychologists. RESULTS The two groups of schizophrenic patients showed significant differences in age ( t =2.79; p =0.008), level of education ( t =2.33; p =0.025) and intelligence ( t =8.80; p =0.001). There were no statistically significant differences between the two groups in the length of illness. Group comparisons. The two IQ groups were compared for the different measures using t -tests, or ANCOVAs when age and education level were correlated with the dependent measure considered (see Table 3). Correlations between IQ and cognitive measures. Pearson correlations were calculated between IQ and the cognitive measures. The results showed that IQ was related to these WCST scores: categories (R=0.47, p =0.002), number of trials (R=-0.63, p <0.001), total errors (R=-0.51, p =0.001), and perseverative errors (R=-0.47, p =0.001). IQ was also related to the following RBMT screening scores: delayed verbal recall (R=0.34, p =0.03) and orientation (R=0.34, p =0.03); and to the following RBMT profile scores: orientation (R=0.43, p =0.04) and total score (R=0.33, p =0.036). Finally, IQ was also correlated with non studied fragments in the word fragment completion test (R=0.55, p <0.001). CONCLUSIONS Despite the fact that schizophrenic patients have key cognitive deficits, their intellectual ability seems to be related to all of them but not globally to memory. Within the memory domain there are differences associated to the explicit – implicit dichotomy, and to the specific measure used to assess memory. High intellectually functioning patients (IQ above 85) perform significantly better than patients with an IQ below 85 in: executive function, attention, speed of information processing, working memory, episodic delayed verbal recall, and recall after a delayed time period, of learned semantic information. However, both groups had similar results in immediate verbal recall, immediate non-verbal recognition, and in everyday memory. In implicit memory, performance is worst in the lower IQ group than in the higher IQ group when it is assessed throw a word fragment completion test. In contrast, performance is the same in both groups when it is measured using the word production from semantic categories test. Dissociations between implicit memory tests can be accounted for by postulating a continuum of tests, from those requiring more perceptual information (data-driven tests) to those requiring knowledge of meaning (conceptually-driven tests) [8]. When attention capacity is considered the group with high IQ does not show any significant correlation between attention and the results in either of the two implicit memory tasks. However, the group with the lower IQ shows significant correlations between attention and performance in the word-fragment completion task. In summary, result indicates that IQ level is determinant in some memory deficits, and point to the idea that differences in memory performance depend more on the tasks demands of the test used to assess memory than on the IQ. REFERENCES [1] Aleman A, Hijman R, de Haan EHF, Kahn RS. 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