[Show abstract][Hide abstract] ABSTRACT: Although there are many opportunities to study memory in patients with Alzheimer's disease (AD) in the laboratory, there are few opportunities to study memory for real world events in these patients. The September 11, 2001 terrorist attacks provided one such opportunity. Patients with AD, patients with mild cognitive impairment (MCI), and healthy older adults were given a telephone questionnaire in the initial weeks after the event, again three to four months later, and finally one year afterwards to evaluate their memory for the September 11, 2001 terrorist attacks. We were particularly interested in using the attacks as an opportunity to examine the decline of episodic memory in patients with AD, patients with MCI, and older adult controls over a period of months. We found that compared to healthy older adults, patients with AD and MCI showed impaired memory at the initial time point, more rapid forgetting from the initial to the three-month time point, and very similar changes in memory from the three-month to the one-year time point. We speculated that these findings were consistent with patients with AD and MCI showing initial impaired encoding and a more rapid rate of forgetting compared with healthy older adults, but that once the memories had been consolidated, their decay rate became similar to that of healthy older adults. Lastly, although memory distortions were common among all groups, they were greatest in the patients with AD.
[Show abstract][Hide abstract] ABSTRACT: Patients with mild Alzheimer's disease (AD) and age-matched controls were compared on a series of tasks designed to measure errors of mis-attribution, the act of attributing a memory or idea to an incorrect source. Mis-attribution was indexed through the illusory truth effect, the tendency for participants to judge previously encountered information to be true. Cognitive theories have suggested that the illusory truth effect reflects the mis-attribution of experimentally produced familiarity (a nonspecific sense that an item has been previously encountered) to the veracity of previously encountered information. Consistent with earlier suggestions that AD impairs both familiarity and recollection (specific memory for contextual details of the study episode), AD patients demonstrated significantly fewer mis-attribution errors under conditions in which the illusory truth effect is thought to rely on relative familiarity (uncued condition), but more mis-attribution errors under conditions thought to rely on relative amounts of contextual recollection (cued condition). These results help further specify the precise nature of memory impairments in AD.
[Show abstract][Hide abstract] ABSTRACT: This study examined 2 factors contributing to false recognition of semantic associates: errors based on confusion of source and errors based on general similarity information or gist. The authors investigated these errors in patients with Alzheimer's disease (AD), age-matched control participants, and younger adults, focusing on each group's ability to use recollection of source information to suppress false recognition. The authors used a paradigm consisting of both deep and shallow incidental encoding tasks, followed by study of a series of categorized lists in which several typical exemplars were omitted. Results showed that healthy older adults were able to use recollection from the deep processing task to some extent but less than that used by younger adults. In contrast, false recognition in AD patients actually increased following the deep processing task, suggesting that they were unable to use recollection to oppose familiarity arising from incidental presentation.
[Show abstract][Hide abstract] ABSTRACT: Patients with mild Alzheimer's disease (AD) were compared with age-matched control subjects on an associative recognition task. Subjects studied pairs of unrelated words and were later asked to distinguish between these same studied pairs (intact) and new pairs that contained either rearranged studied words (rearranged) or non-studied words (non-studied). Studied pairs were presented either once or 3 times. Repetition increased hits to intact pairs in both groups, but repetition increased false alarms to rearranged pairs only in patients. This latter pattern indicates that repetition increased familiarity of the rearranged pairs, but only the control subjects were able to counter this familiarity by recalling the originally studied pairs (a recall-to-reject process). AD impaired this recall-to-reject process, leading to more familiarity based false alarms. These data support the idea that recollection-based monitoring processes are impaired in mild AD.
[Show abstract][Hide abstract] ABSTRACT: National traumatic events can produce extremely vivid memories. Using a questionnaire administered during telephone interviews, the authors investigated emotional responses to, and memory for. the September 11, 2001, terrorist attacks in patients with Alzheimer's disease (AD), patients with mild cognitive impairment (MCI), and healthy older adults in the initial weeks following the event and again 3-4 months later. There were several notable findings. First, patients with AD showed less memory than patients with MCI and older adults. Second, patients with AD, but not patients with MCI or older adults, appeared to retain more memory for personal versus factual information. Third, patients with AD and older adults did not differ in the intensity of their reported emotional responses to the attacks, whereas patients with MCI reported relatively less intense emotional responses. Last, distortions of memory for personal information were frequent for all participants but were more common in patients with AD.
[Show abstract][Hide abstract] ABSTRACT: Brain potentials associated with true and false recognition were recorded using a paradigm consisting of categorized color photographs. Two ERP components were identified. A parietal component was most positive for both true and false recognition, less positive for rejection of lures, and least positive for rejection of novel items. A later frontal component was more positive for false recognition, rejection of lures, and misses than for true recognition and rejection of novel items. The authors suggest that the parietal component may reflect the extent to which test items engender recollection of the gist representation of the study list, while the late frontal component may reflect the engagement of effortful post-retrieval processes.
[Show abstract][Hide abstract] ABSTRACT: Patients with Alzheimer's disease (AD) have been found to exhibit lower levels of false recognition of semantic associates compared with healthy older adults. Because these patients may show impaired performance of episodic and semantic memory tasks, this finding could be explained by deficits in episodic memory, semantic memory, or both. The authors adapted a paradigm for comparison of semantic versus phonological false recognition. They found that: (a) patients with AD exhibited lower levels of corrected false recognition of semantic, phonological, and hybrid (mixed semantic and phonological) lists than older adults, and (b) patients with AD showed very similar levels of false recognition for all list types. These results suggest that only episodic memory deficits are necessary to explain the lower level of false recognition of semantic associates observed in patients with AD when compared to older adults. Additionally, (c) older adults showed greater levels of semantic, phonological, and hybrid false recognition than younger adults, extending previous false recognition research of semantically related words and categorized colored photographs to phonologically related words.
Brain and Cognition 05/2003; 51(3):251-61. · 2.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To better understand memory distortions and false recognition in patients with Alzheimer disease (AD), using a paradigm of categorized color photographs.
Previous research has found that patients with AD and older adults showed similar levels of uncorrected false recognition of semantic associates and of perceptually related novel objects. In contrast to these results, using a paradigm in which semantically related words were accompanied by black and white line drawings, it was found that patients with AD showed a trend toward higher levels of uncorrected false recognition compared with older adults.
To explore this trend, 24 patients with AD and 24 older adults matched for age, education, and gender were examined using a false recognition paradigm consisting of categorized color photographs (e.g., flowers, motorcycles, cats).
Compared with older adults, patients with AD showed higher levels of uncorrected false recognition, but lower levels of corrected false recognition and lower levels of item-specific recollection.
The authors suggest that these results may be attributable to the poor ability of patients with AD to acquire both gist and item-specific information as well as these patients' inherent frontal lobe dysfunction leading to difficulty inhibiting responses on the basis of familiarity alone.
Cognitive and Behavioral Neurology 04/2003; 16(1):16-27. · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Previous research has shown that patients with Alzheimer's disease show increasing levels of false recognition across five repeated study-test trials of semantic associates. The present study tested the hypotheses that (i) the increasing false recognition was partly due to the frontal lobe dysfunction of patients with Alzheimer's disease, and (ii) a failure of source monitoring was the central mechanism by which frontal lobe dysfunction led to increasing false recognition across trials. In Experiment 1, patients with frontal lobe lesions and controls were examined in the same repeated trials paradigm as that used previously in patients with Alzheimer's disease. Although controls were able to reduce their false recognition across trials, the patients with frontal lobe lesions were not, and instead showed a constant level of elevated false recognition across the study-test trials. In Experiment 2, two groups of patients with Alzheimer's disease and healthy older adult controls were studied: the first group was given a single study session followed by a recognition test, the second group was given five study sessions followed by a single recognition test. Older adults who were exposed to five study lists demonstrated lower levels of false relative to true recognition, whereas patients with Alzheimer's disease in this condition exhibited levels of false recognition elevated to that of their true recognition, even with the source memory confusion of intervening tests eliminated. The authors suggest that impairment in aspects of frontal lobe function, such as verification-inhibition mechanisms, probably contributes to the inability of patients with Alzheimer's disease to suppress their false recognition across repeated trials. Lastly, it is speculated that one way in which the frontal lobes enable normal episodic memory function is by facilitating the suppression of false recognition and other distortions of memory.