Archive of SID Iranian Red Crescent Medical Journal ORIGINAL ARTICLE
Memory Process in Demented and Non-Demented Elderly Patients A Mani1, 2*, T Hashemi1, H Haghshenas2, MT Garouci Farshi1, AH Shariat3 1
Department of Psychology, Tabriz University, Tabriz, 2Department of Psychiatry, 3Department of Neurology, Shiraz University of Medical Science, Shiraz, Iran Abstract Background: Dementia is characterized by progressive memory loss and other cognitive impairments. Memory impairments are apparent on tasks that require learning and retention of verbal or non-verbal information. Demented patients present severe impairments on recognition and recalling tasks. They have severe deficits in transferring information in to a long-term storage system. The present study investigated any difference between various memory processes in different reproduction phases contribute to discrimination between demented and non-demented elderly patients. Methods: Thirty one demented and 25 non-demented elderly patients were selected according to inclusion criteria; all of them were visited by a physician completing the Mini Mental Status Examination (MMSE) and California Verbal Learning Test-Persian version (CVLT-P). Results: Although demented and non-demented elderly subjects had no difference in relation to age and education, differences on clinical variables were significant and demented patients showed lower means than nondemented ones. A discriminate function analysis showed that CVLT-P had the ability to differentiate between demented and non-demented elderly patients and could correctly classify 94.3% of demented and non-demented older adults. Conclusion: Findings suggest that CVLT-P could discriminate satisfaction between these two groups and according to subscales, learning slope had the highest discrimination coefficient. So demented patients had more deficits in hippocampus causing failure of learning. Keywords: Neuropsychology; Memory; dementia; CVLT; Iran
Introduction Dementia is characterized by progressive memory loss and other cognitive impairments, e.g. aphasia, apraxia and personality changes. Despite the global nature of the cognitive dysfunction in dementia, memory disorder is clearly the most prevalent and prominent feature of early stages of disease.1 In the early stages of dementia, memory difficulties are apparent when dementia patients are confronted with everyday tasks requiring episodic memory.2 Memory impairments are apparent on tasks that *Correspondence: Arash Mani, PhD, Assistant Professor of Cognitive Neuroscience, Department of Psychiatry, Shiraz University of Medical Sciences, Shiraz, Iran. Tel: +98-711-6279319, Fax: +98711-6279319, e-mail:
[email protected] Received: November 10, 2009 Accepted: April 26, 2010
require learning and retention of verbal or non-verbal information. Demented patients present severe impairments on recognition and recall tasks. They have severe deficits in transferring information into a longterm storage system. Delis et al. (1991)3 reported that this anterograde amnesia is not primarily due to difficulties in retrieval mechanisms but instead that it reflects a defect at the level of consolidation.3 This defect may be mediated by damage to hippocampus4 and entorhinal cortex and by neurotransmitter changes in cholinergic system.5 Therefore, the differences in memory performance between dementia and nondemented elderly patients are frequently investigated. A review of experimental studies on the specific memory disorders in dementia (Alzheimer disease, in particular) shows that in addition to episodic memory problems, there are also major semantic memory
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dysfunctions.6 Alzheimer disease patients exhibit, relative to unimpaired elderly controls, poor semantic encoding of to be learned information.7 This will also affect episodic memory performance, especially with material that has an inherent semantic structure or in semantic cuing task: Alzheimer disease patient do not benefit from such cues, unlike unimpaired elderly controls.8 Alzheimer disease patients might not be able to discriminate between two related concepts, because the attribute knowledge that distinguish the two concepts has been lost.9 In addition, Alzheimer disease patients’ deficits are evident in recognition tasks, particularly when semantically related distracters are used- their responses contain many false-positive errors.10 Generally the memory may be subdivided and evaluated according to different demands on the reproduction process (free recall, cued recall, recognition), or the length of the interval between learning and reproduction phase (immediate, recall, delay recall).1 In the present study, we investigated whether the difference between various memory processes in different reproduction phases contribute to discrimination between demented and non-demented elderly.
Status Examination (MMSE)11 and DSM-IV-TR criteria by physicians and they confirmed their dementia (n=31) or non-dementia (n=25) cases. In this study, all subjects completed California Verbal Learning Test-Persian version-(CVLT-P),12 which was translated and validated for Iranian native language-Persian- by the kind permission of Delis, the author of original version. The test evaluated memory process in immediate and delay phases, besides for each subject learning rate which was calculated by using a special formula. Therefore, for each subject we had seven separate numbers,(i) Immediate Free Recall Total (IFRT); (ii) Short- Delay Free Recall (SDFR); (iii) Short Delay Cued Recall (SDCR); (iv) Long Delay Free Recall (LDFR); (v) Long Delay Cued Recall (LDCR); (vi) Long Delay Yes/No Recognition (LDR) and (vii) Learning Slope (LS). SPSS software was applied for statistical analysis. Statistical analysis of seven subscales of CVLT-P was performed by student’s t test, two tailed and discrimination analysis to evaluate how accurate CVLT-P can discriminate between demented and non-demented aged people. A p value less than 0.05 was considered significant.
Materials and Methods Results Our cross-sectional study was conducted at five elderly dwellings affiliated to Shiraz Welfare Organization and Geriatric Psychiatry and Neurology Clinic affiliated to Shiraz University of Medical Science, Shiraz, southern Iran during 2008-2009. The patients (n=56) were selected according to the following inclusion criteria (i) at least 65 years old; (ii) at least 6 years education, and (iii) fluent Persian speakers. Subjects were evaluated according to Mini Mental
Analyses of means differences (Independent sample t-test) were computed to assess groups’ differences on various demographic and clinical variables. Results indicated that though demented and non-demented elderly subjects had no differences in relation to age and education, but differences on clinical variables were significant and demented patients showed lower means than non-demented ones (Table 1).
Table 1: Demographic and clinical characteristics of demented and non-demented patients Demographic and clinical Demented Non-demented Characteristics (n=31) (n=25) Mean SD Mean SD Age 74.25 6.15 73.08 4.7 Education 2.25 1.71 2.76 0.97 MMSE 15.16 4.61 25.92 2.34 Immediate Free Recall Total 22.54 11.09 49.75 9.49 Short- Delay Free Recall 2.38 2.76 10.29 3.02 Short Delay Cued Recall 4.06 3.15 11.20 2.3 Long Delay Free Recall 2.62 2.80 10.83 3.04 Long Delay Cued Recall 3.64 3.27 11.54 2.08 Long Delay Yes/No Recognition 10.35 5.38 14.33 1.63 Learning Slope 0.645 0.61 1.47 0.49
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P value 0.058 0.197 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001
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Finally, a discriminate function analysis was conducted to determine if CVLT-P had the ability to differentiate between demented and non-demented elderly. CVLT-P correctly classified 94.3% of demented and non-demented older adults (Table 2), with 93% sensitivity and 95.8% specificity. We should note that 94% of total samples were correctly classified. Table 2: Classification Analysis for CVLT-P Predicted Non-demented Demented Actual No. % No. % Non-demented 23 95.8 1 4.2 Demented 2 6.9 27 93.1
Canonical discriminate function coefficients revealed that Short-Delay Free Recall (SDFR) and Learning Slope (LS) had higher coefficients rather than other subscales; accordingly the following equation could be helpful in discriminating demented and non-demented patient in clinic. D=-2.56+.009 IFRT+.114 SDFR - .29 SDCR+.10 LDFR+.149 LDCR -.038 LDR+.51 LS As the equation shows, Immediate Free Recall Total (IFRT) and Learning Slope (LS) were the least and the most discriminative variables respectively. Discussion The main finding of this study is that the seven subscales of CVLT-P did show significant evidence of memory reproduction deficits in dementia patients as compared to non-demented ones. In addition to memory reproduction deficit, learning slop was significantly lower in demented patients compared with non-demented group. In free recall reproduction in immediate phase though word list was repeated about five times, dementia patients performed less success rather than non-demented subjects. It means that these patients did not have any beneficial of the
repetitions and according to Delis et al. study, this anterograde amnesia is not primarily due to difficulties in retrieval mechanisms but instead that it reflects a defect at the level of consolidation,3 and also Hyman et al. declared that this defect may be mediated by the damage to hippocampus.4 So it is obvious that learning slope would not be constructed in these patients. In cue recall and recognition reproduction, demented subjects did less success in categorizing words in the correct category, than non-demented ones. These findings could be interpreted according to attribute erosion hypothesis,9 which suggests that it is the loss or deterioration of attributes or features of concepts that causes category impairments.13 An alternative explanation for the impairments in semantic knowledge associated with dementia proposes is that, rather than being lost or eroded, semantic attributes become increasingly disorganized as the disease progresses.14 According to this perspective, individuals with dementia should not be able to discriminate those attributes that are essential or more relevant for a specific concept from those that are peripheral or irrelevant. Sailor et al. countered this alternative proposal on grounds that attribute relevance is an important measure of semantic organization and, indeed, the concept of semantic relevance has gained renewed importance in very recent accounts.15 Finally, our findings suggest that CVLT-P could discriminate satisfaction between these two groups, and according to subscales, learning slope had the highest discrimination coefficient. So demented patients had more deficits in the hippocampus; and with learning failure. It is recommended that other researchers consider mild cognitive impairment and perform on different brain damage. Acknowledgement Special thanks are extended to Dr. A. Javadpour for kindly evaluating the patients. Conflict of interest: None declared.
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