The impact of time and repeated exposure on famous person knowledge in amnestic mild cognitive impairment and Alzheimer's disease.

OBJECTIVE: Famous people knowledge has been shown to be impaired early in Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI). However, the question of whether recently acquired knowledge is more impaired than remotely acquired knowledge remains a matter of debate. The aim of this study was to investigate the patterns of semantic memory impairment in aMCI and AD by investigating 2 factors that may influence the retrieval of such knowledge, namely remoteness and frequency of repetition of information over time. METHOD: Three groups (19 controls, 20 aMCI, and 20 AD patients) were compared on a test assessing general and specific biographical knowledge about famous people, where the period of acquired fame (remote vs. recent) and the type of fame (enduring vs. transient) were controlled for. RESULTS: Global performance of aMCI and AD patients was significantly poorer than that of controls. However, different patterns of recall were observed as a function of time and type of fame. A temporal gradient was found in both patient groups for enduring names but not for transient ones, whereby knowledge about remote enduring famous persons was better recalled. Patients were more impaired at questions assessing specific biographical knowledge (unique to an individual) than more general knowledge. CONCLUSIONS: Tests of famous people knowledge offer a unique opportunity to investigate semantic deficits in aMCI and AD, because they make it possible to estimate the time at which memories were acquired, as well as the type of fame. Results are discussed in light of memory consolidation models. (PsycINFO Database Record

Alzheimer's disease and memory strength: Gradual decline of memory traces as a function of their strength.

OBJECTIVE: Episodic memory impairment is at the core of amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). The origin of memory deficits may result either from an encoding deficit or from an accelerated decline of the memory trace. The present study explores these two hypotheses. METHOD: We used the delayed-matching-to sample 48 items (DMS-48) memory test in a group of controls, aMCI patients, and AD patients (n= 16 in each group). The DMS-48 offers an incidental learning phase followed by three forced-choice recognition tests at three-minute, one-hour, and one-week delays. Moreover, the forced-choice test distinguishes three kinds of couple items: abstract (meaningless), paired (two similar exemplars), and unique (two different objects) items. RESULTS: As predicted by the accelerated forgetting hypothesis, patients showed a decrease in recognition performance over time. Controls also exhibited a similar decline in performance. As predicted by the encoding deficit hypothesis, abstract items were the most poorly recognized in AD, at both the three-minute and the one-week delays. In AD, recognition of the paired items also dropped after the one-hour delay, followed by unique items after a one-week delay. Patients with aMCI exhibited a performance that was similar to controls, except for abstract items, which dropped at the one-week delay. CONCLUSIONS: These results are discussed in light of a third hypothesis, the memory strength hypothesis, in order to better account for the progressive decline in memory performance as a function of the item type in AD.

Memory for Public Events in Mild Cognitive Impairment and Alzheimer's Disease: The Importance of Rehearsal.

Ribot's law refers to the better preservation of remote memories compared with recent ones that presumably characterizes retrograde amnesia. Even if Ribot-type temporal gradient has been extensively studied in retrograde amnesia, particularly in Alzheimer's disease (AD), this pattern has not been consistently found. One explanation for these results may be that rehearsal frequency rather than remoteness accounts for the better preservation of these memories. Thus, the aim of present study was to address this question by studying retrograde semantic memory in subjects with amnestic mild cognitive impairment (aMCI) (n = 20), mild AD (n = 20) and in healthy older controls (HC; n = 19). In order to evaluate the impact of repetition as well as the impact of remoteness, we used a test assessing memory for enduring and transient public events that occurred in the recent and remote past. Results show no clear temporal gradient across time periods (1960-1975; 1976-1990; 1991-2005; 2006-2011), but a better performance was observed in all three groups for enduring compared with transient events. Moreover, although deficits were globally found in both patients groups compared with HC, more specific analyses revealed that aMCI patients were only impaired on transient events while AD patients were impaired on both transient and enduring events. Exploratory analyses also revealed a tendency suggesting preservation of remote transient events in aMCI. These findings are discussed with regards to memory consolidation models.

[The evaluation of the retrograde memory in the Quebec population aged: PUB-40 and PUB-12]. / L'évaluation de la mémoire rétrograde dans la population Québécoise âgée: Le PUB-40 et le PUB-12.

Memory assessment represents an important part of the clinical neuropsychologist's duties in a geriatric context. In fact, in Canada, about one-third of seniors report memory complaints, with different causes. Based on the underlying etiology, different components of memory may be affected in older adults. Nonautobiographical retrograde memory (public or semantic) is an important aspect of memory to assess; nevertheless, there is currently no reliable and standardized clinical tool to evaluate this aspect of memory in the elderly Quebecer population. The aims of this research were therefore: (1) to develop a protocol specifically aimed at assessing non-autobiographical retrograde memory in this population, the PUB-40; (2) to obtain reference data among 105 healthy subjects; and (3) to develop a short version based on the items which discriminated a group of 20 patients with amnestic Mild cognitive impairment (aMCI) from older healthy subjects.

The role of the left anterior temporal lobe in the semantic processing of famous faces.

Neuroimaging studies on healthy subjects have reported the involvement of the bilateral anterior temporal lobes (ATL) in recognizing known people. While the role of the right ATL in the semantic processing of known people is accepted, it is still matter of debate whether left ATL is implicated in the name retrieval or in the access to semantic information. In the present fMRI study, we modulated the level of specificity of the semantic categorization task of famous face stimuli in order to map the brain regions involved in the specific semantic processing controlling for automatic name access. Specifically, participants (n = 12, mean age = 23.0+/-1.7 years, F/M = 8/4) were asked to determine whether the stimulus photograph matched with the label of the profession category. Since the same set of stimuli was used for both specific and general conditions, contrasting these two conditions controlled for the activation due to the automatic access to the name of famous persons. Results showed that: 1) the right ATL was activated by a semantic categorization task of famous face stimuli at both general and specific level; 2) while controlling for the activation due to the automatic name retrieval, the left ATL showed increased activation during the specific categorization task; 3) the specificity of the semantic processing increased strength of connections towards the left ATL from the right lateral fusiform gyrus, devoted to the visual processing of faces, and from the right ATL. These findings support the idea of a crucial role of the left anterior temporal lobe in the processing of person-specific semantic information.