ناتوانی در ادراک بیماری حافظه ای در بیماری آلزایمر: آزمایشی از اگنیو و موریس (1998)

Abstract Agnew and Morris [Agnew, S. K. & Morris, R. G. (1998). The heterogeneity of anosognosia for memory impairment in Alzheimer's disease: A review of the literature and a proposed model. Aging and Mental Health, 2, 9–15] model of awareness for memory functioning has attempted to account for the variance of anosognosia exhibited within the Alzheimer's disease (AD) population. There has been tentative evidence to suggest that the mnemonic anosognosia sub-type, proposed by this model, is common within the early stages of AD. However, this study is the first directly to test the model. Eighteen older adults with early AD and 18 healthy older adults were recruited. Awareness of memory functioning was monitored using patient-performance measures of “task specific” awareness; a measure of global memory awareness; and a patient-informant measure. The stability of participants’ awareness was measured across three word recall lists and after a 20-min delay. Results suggested that, whilst the participants with early AD were less aware of their memory ability than the healthy older adults, they were able to improve their awareness following exposure to a memory task. Furthermore, the improvements in awareness were largely retained after the delay period. These findings are discussed in relation to Agnew and Morris [Agnew, S. K. & Morris, R. G. (1998). The heterogeneity of anosognosia for memory impairment in Alzheimer's disease: A review of the literature and a proposed model. Aging and Mental Health, 2, 9–15] model of mnemonic anosognosia and to current thinking about autobiographical memory.

2. Results 2.1. Prediction accuracy Fig. 2 shows mean pre-study prediction, post-study prediction and actual recall over the three lists by group. Number of words predicted or recalled during pre-list, post-list and recall ... Fig. 2. Number of words predicted or recalled during pre-list, post-list and recall stages of the three lists and after the delay. Note. AD = Alzheimer's disease; HO = healthy older adults; Error bars represent standard errors. Figure options 2.1.1. Recall A repeated measures ANOVA of list order (first/second/third) by group (AD/HO) for the number of words recalled, revealed a significant group difference, F(1, 34) = 37.51, p < 0.01, with the AD group performing significantly worse than the HO group. There was also a significant effect of list order, F(2, 68) = 5.96, p < 0.01, and a significant interaction, F(2, 67) = 6.45, p < 0.01. However, a simple main effects analysis indicated that the list order effect was only significant for the HO, F(2, 34) = 11.10, p < 0.01, not the AD group, F < 1. Alpha adjusted paired samples t-tests for HO participants only revealed an initial decline in the mean number of words recalled from the first list to the following lists, first versus second, t(17) = 3.62, p < 0.01, second versus third, t(17) = 0.53, p = 0.60, first versus third, t(17) = 4.78, p < 0.01. This can clearly be seen in Fig. 2. As the lists were counterbalanced this finding may represent motivational effects caused by the repetition and simplicity of this task for the HO group. 2.1.2. Accuracy of predictions Given that over and under predictions may not represent equivalent forms of impaired awareness (Schwartz & Metcalfe, 1994), analysis of the actual accuracy scores was conducted. A three-way repeated measures ANOVA of group (AD/HO) by phase (pre-list/post-list) by list order (first/second/third) revealed a significant main effect of group, F(1, 34) = 15.11, p < 0.01 suggesting that participants with AD were less accurate overall. There was no main effect of list order, F < 1. However, there was a significant interaction, F(2, 68) = 5.65, p < 0.01. Simple main effects indicated a significant group difference in overall prediction accuracy for all three lists: first, F(1, 34) = 23.29, p < 0.01; second, F(1, 34) = 4.39, p = 0.04; third, F(1, 34) = 5.60, p = 0.02. For the first list, on average, HO participants underestimated their performance by less than one word (M = −0.61), whereas for all other lists they slightly overestimated their performance (second: M = 0.53; third: M = 0.36). AD participants, by contrast, overestimated their performance throughout (first: M = 2.75; second: M = 1.89; third: M = 1.83) and to a greater extent. In addition, there was a significant main effect of phase, F(2, 68) = 4.23, p = 0.048. Overall, the participants were more accurate post- than pre-list. However, neither the phase by group, F(2, 68) = 1.96, p = 0.17, nor the phase by list order, F(2, 68) = 1.94, p = 0.15, interactions were significant, suggesting no differences in the degree to which the groups improved their accuracy pre- and post-list, nor in the general pattern of improvement pre- to post-list across lists. Although there was a significant three-way interaction, F(2, 68) = 6.88, p < 0.01, analysis of the means revealed that both groups became more accurate in their predictions, both pre- and post-list, and over the three lists. However, the HO group initially slightly underestimated performance, both at pre- and post-list, and then slightly overestimated for the second and third lists. By contrast, the AD group overestimated throughout. These findings were consistent with the pattern revealed by the list order by group interaction. 2.1.3. Delay In order to explore the effect of a delay on prediction accuracy, comparisons were conducted between pre-list predictions for the first, third and for the delayed lists. In AD, a significant difference was found between first and third list pre-list predictions, z (N = 18) = −2.17, p = 0.03, suggesting that participants significantly revised their predictions downwards after exposure to the three lists. A trend was found for the difference between the first list pre-list and delayed list predictions, z (N = 18) = −1.94, p = 0.05. Finally, there was no significant difference between the third list pre-list and the delayed list predictions, z (N = 18) = −1.66, p = 0.10. Thus, whilst the predictions of those with AD after a delay period exhibited a moderate decline in accuracy, they did not reset to pre-task exposure levels, remaining broadly consistent with predictions made after exposure to all three lists. For the HO group, as anticipated, no significant differences were found; first and third list pre-list predictions, z (N = 18) = −1.90, p = 0.06, first pre-list and delayed list predictions, z (N = 18) = −1.90, p = 0.06, third list pre-list and delayed list predictions, z (N = 18) = 0.00, p = 1.00. 2.1.4. Explicit awareness—judgement scale AD participants’ explicit ratings of performance immediately after recall correlated significantly with post-list prediction accuracy; first list, rs(16) = 0.73, p < 0.01 and third list, rs(16) = 0.63, p = 0.01, but not second list, rs(16) = 0.25, p = 0.32. There were also significant correlations for the HO group for first list, rs(16) = 0.86, p < 0.01 and third list, rs(16) = 0.74, p < 0.01, but not second list, rs(16) = 0.22, p = 0.37. Thus, individuals who over-predicted their performance post-study, correctly rated their performance after recall as worse/much worse than expected. Fig. 3 shows post-study prediction accuracy for participants grouped by explicit judgement and list. Positive scores reflect over-prediction. Even for the second list, where correlations were low, both HO and most AD participants correctly judged that they had recalled fewer words than predicted. Participants’ prediction accuracy scores compared to their explicit judgments of ... Fig. 3. Participants’ prediction accuracy scores compared to their explicit judgments of performance. Figure options 2.1.5. Global awareness—AMIS Alpha adjusted paired t-tests were conducted to determine if individuals with AD exhibited increased global awareness after exposure to memory trials, but did not retain this awareness after a delay. A comparison of pre- and post-test AMIS scores indicated significant differences, t(17) = −2.67, p = 0.02. However, there was no significant difference between pre-test and the delay scores, t(17) = −0.89, p = 0.39, or between post-test and the delay scores, t(17) = 1.29, p = 0.22. No significant differences were found for the HO group, pre-post, t(17) = −1.00, p = 0.33, pre-delay, t(17) = −0.60, p = 0.53, or post-delay, t(17) = −0.56, p = 0.58. This suggests that the AD participants revised their global ratings after exposure to memory testing. However, whilst ratings declined after the delay interval, they did not return to pre-testing levels. Consistent with prediction accuracy data, the AD participants retained much of their general awareness gained by exposure to testing.