Episodic and semantic memory in mild cognitive impairment

Little is known about episodic and semantic memory in the early predementia stage of Alzheimer's disease (AD), which is referred to as mild cognitive impairment (MCI). To explore person knowledge, item recognition and spatial associative memory, we designed the Face Place Test (FPT). A total of 75 subjects participated: 22 patients with early AD, 24 with MCI and 29 matched controls. As predicted, AD patients showed significant deficits in person naming, item recognition and recall of spatial location (placing). Surprisingly, subjects with MCI were also impaired on all components. There was no significant difference between AD and MCI except on the placing component. Analysis of the relationship between semantic (naming) and episodic (recognition and placing) components of the FPT revealed a significant association between the two episodic tasks, but not between episodic and semantic performance. Patients with MCI show deficits of episodic and semantic memory. The extent of impairment suggests dysfunction beyond the medial temporal lobe. The FPT might form the basis of a sensitive early indicator of AD.     

The cognitive and neural expression of semantic memory impairment in mild cognitive impairment and early Alzheimer's disease

Semantic deficits in Alzheimer's disease have been widely documented, but little is known about the integrity of semantic memory in the prodromal stage of the illness. The aims of the present study were to: (i) investigate naming abilities and semantic memory in amnestic mild cognitive impairment (aMCI), early Alzheimer's disease (AD) compared to healthy older subjects; (ii) investigate the association between naming and semantic knowledge in aMCI and AD; (iii) examine if the semantic impairment was present in different modalities; and (iv) study the relationship between semantic performance and grey matter volume using voxel-based morphometry. Results indicate that both naming and semantic knowledge of objects and famous people were impaired in aMCI and early AD groups, when compared to healthy age- and education-matched controls. Item-by-item analyses showed that anomia in aMCI and early AD was significantly associated with underlying semantic knowledge of famous people but not with semantic knowledge of objects. Moreover, semantic knowledge of the same concepts was impaired in both the visual and the verbal modalities. Finally, voxel-based morphometry analyses revealed that semantic impairment in aMCI and AD was associated with cortical atrophy in the anterior temporal lobe (ATL) region as well as in the inferior prefrontal cortex (IPC), some of the key regions of the semantic cognition network. These findings suggest that the semantic impairment in aMCI may result from a breakdown of semantic knowledge of famous people and objects, combined with difficulties in the selection, manipulation and retrieval of this knowledge.     

Everyday memory impairment of patients with mild cognitive impairment

We evaluated everyday memory impairment in 24 patients with mild cognitive impairment (MCI) with the Rivermead Behavioral Memory Test (RBMT) and compared the scores with those of 48 age-, sex- and education-matched normal controls (NC) and 48 age-, sex- and education-matched Alzheimer disease (AD) patients. Overall everyday memory was impaired in MCI patients but the severity was milder than that in AD patients. The MCI patients showed impairment of everyday memory tasks requiring delayed recall. But they could normally perform tasks immediately after memorizing, except for recalling and retracing a simple new route. The total Profile score correctly classified 100% of the MCI patients and 91.7% of NC, thus demonstrating the usefulness of the RBMT for diagnosing MCI patients. Prospective memory tasks were not useful for detecting the patients with MCI.     

Episodic, but not semantic, autobiographical memory is reduced in amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) is characterized by decline in anterograde memory as measured by the ability to learn and remember new information. We investigated whether retrograde memory for autobiographical information was affected by aMCI. Eighteen control (age 66-84 years) and 17 aMCI (age 66-84 years) participants described a personal event from each of the five periods across the lifespan. These events were transcribed and scored according to procedures that separate episodic (specific happenings) from semantic (general knowledge) elements of autobiographical memory. Although both groups generated protocols of similar length, the composition of autobiographical recall differentiated the groups. The aMCI group protocols were characterized by reduced episodic and increased semantic information relative to the control group. Both groups showed a similar pattern of recall across time periods, with no evidence that the aMCI group had more difficulty recalling recent, rather than remote, life events. These results indicate that episodic and semantic autobiographical memories are differentially affected by the early brain changes associated with aMCI. Reduced autobiographical episodic memories in aMCI may be the result of medial temporal lobe dysfunction, consistent with multiple trace theory, or alternatively, could be related to dysfunction of a wider related network of neocortical structures. In contrast, the preservation of autobiographical semantic memories in aMCI suggests neural systems, such as lateral temporal cortex, that support these memories, may remain relatively intact.     

Impairment of episodic and semantic autobiographical memory in patients with mild cognitive impairment and early Alzheimer's disease

Autobiographical memory includes the retrieval of personal semantic data and the remembrance of incident or episodic memories. In retrograde amnesias, it has been observed that recall of autobiographical memories of recent events is poorer than recall of remote memories. Alzheimer's disease (AD) may also be associated with a temporal gradient (TG) in memory decline, though studies have yielded inconsistent results on this point. They have also yielded inconsistent results on whether AD might differentially affect semantic and episodic remembrance. Here, we compared autobiographical memory of childhood, early adulthood, and recent life among healthy control (HC) subjects, patients with early AD, and patients with amnesic mild cognitive impairment (aMCI). Both the aMCI and AD patients exhibited declines in recall of autobiographical incidents and semantic information. In AD patients, both components of autobiographical memory had a clear TG, with better preservation of memories of childhood than those of early adulthood and recent life. The TG of autobiographical memory decline in AD patients is more compatible with the Cortical Reallocation Theory than with the Multiple Trace Theory of memory consolidation. In contrast to AD patients, aMCI patients exhibited impaired recall of personal facts and autobiographical incidents relating only to recent life. The significant decline in autobiographical memory for recent life that occurred in aMCI patients suggests that deterioration of consolidation of personal facts and events begins with commencement of functional impairment in the hippocampus.     

Alteration of autobiographical memory in amnestic mild cognitive impairment

The concept of amnestic mild cognitive impairment (aMCI) concerns a population of older individuals at high risk of developing probable Alzheimer's disease. Although anterograde memory deficits have been largely documented in patients with aMCI, little is known about the integrity of their autobiographical memory (AuM). This study aimed at evaluating AuM in aMCI individuals and at investigating whether their ability to retrieve AuMs varied as a function of whether the tests used required recognition or effortful retrieval processes. Fourteen aMCI patients and 14 matched controls underwent a standard neuropsychological evaluation and an extensive autobiographical assessment. AuM was explored using verbal material, the Autobiographical Memory Interview, and a visual task of personal photographs. Together, these tests tapped the semantic and episodic components of AuM and different cognitive processes involved in retrieval (recall and recognition). Results indicate that AuM is altered in aMCI patients. This impairment affects both episodic and semantic components of AuM, and is characterized by a general difficulty in recollecting personal episodes covering the entire lifespan, along with a loss of recognition of recently experienced episodes. Furthermore, recollection of personal episodes was correlated with scores on tests requiring retrieval abilities, while recognition of familiar photographs was correlated with scores on tests assessing encoding/storage of new information. Results suggest that the AuM deficit in aMCI patients may result from the combination of two mechanisms, an anterograde memory impairment impeding the storage of newly experienced events, and a global alteration of recollection affecting the recall of AuM covering all periods of life. Alteration of these processes may possibly be related to the progression and distribution of the neuropathological lesions in medial temporal and frontal lobe structures found in Alzheimer's disease.     

Event-based prospective memory failure in amnestic mild cognitive impairment

Prospective memory (PM) deficits have recently been documented in individuals with amnestic mild cognitive impairment (aMCI). In this paper, we investigated whether these deficits are due to the failure of retrospective memory processes. We also examined the role played by attentional/executive processes in PM functioning.We enrolled 24 individuals with aMCI and 24 healthy controls (NCs). In the PM procedure, we manipulated both the memory load of the retrospective component of the PM task and the complexity of the ongoing task in a 2 × 2 experimental design. Sequences of four words were presented. Participants had to repeat the sequence in the same order (low attentional demand condition) or in the reverse order (high attentional demand condition). When a target word appeared in the sequence, participants had to press a button on the keyboard (PM task). Target words could be one (low memory load condition) or four (high memory load condition) in different blocks.MCI participants obtained lower PM scores than NCs in all four experimental conditions. However, they recalled the target words less accurately than NCs only in one four-word condition. Finally, the executive demand of the ongoing task did not significantly affect the PM performance of aMCI individuals.Our findings confirm that PM is severely impaired in individuals with aMCI. Moreover, a failure of retrospective memory processes does not seem to fully account for the poor PM performance in aMCI individuals. Finally, the finding that in these individuals, a deficit in executive control cannot be claimed as the main responsible for the observed PM impairment could suggest the involvement of automatic-reflexive processes.     

Profile of memory impairment and gray matter loss in amnestic mild cognitive impairment

The present study assessed the patterns of cortical gray matter (GM) loss in patients with amnestic mild cognitive impairment (aMCI) with distinct profiles of memory impairment, i.e. aMCI patients failing on both recall and recognition memory vs. aMCI patients showing impaired recall but preserved recognition memory. This distinction is usually not taken into account in studies on aMCI and the aim of the present study was to assess whether this distinction is useful. Twenty-eight aMCI patients and 28 matched controls subjects were included. All aMCI patients failed a recall memory task (inclusion criteria). All underwent a visual recognition memory task (DMS48). However, 12 succeeded on this task while 16 failed. Relative gray matter (GM) loss was measured using voxel-based morphometry. When comparing aMCI patients to controls regardless of the profile of memory impairment, GM loss was found in temporal, parietal and frontal areas. However, in aMCI patients with preserved recognition (but impaired recall), GM loss was confined to frontal areas. This contrasted with GM loss in the right medial temporal lobe and bilateral temporo-parietal regions in aMCI patients with impaired recall and recognition memory, a pattern of GM loss usually described in early AD. We conclude that different profiles of memory impairment in aMCI patients are associated with distinct patterns of GM loss.     

Correlates of recognition memory performance in amnestic mild cognitive impairment

Introduction: Determining whether the etiology of amnestic Mild Cognitive Impairment (aMCI) is Alzheimer’s disease (AD) is challenging. Recognition memory (RM) performance could be helpful in identifying individuals with cognitive patterns indicative of underlying AD. In order to better identify such patterns, we examined RM discriminability in aMCI and its associations with nonmemory cognitive domains impaired in AD.

Methods: Participants were 97 individuals diagnosed with aMCI (M_age = 74.48 years) who underwent comprehensive neuropsychological evaluation. Zero-order correlations and hierarchical linear regression analyses were conducted to determine associations between discriminability on the HVLT-R and specific tasks within the domains of executive function (EF) and language, controlling for age and education. Logistic regression was conducted to determine whether performance on individual tasks was predictive of group membership defined as impaired or unimpaired on RM performance.

Results: While 100% of the aMCI group showed impaired delayed recall on a word list, we found that 69% were impaired on RM discriminability, while 31% were not. Discriminability impairment groups did not differ on demographics or global cognition. For the entire aMCI group, performance in the language domain and, specifically, on a confrontation naming task significantly predicted RM discriminability. Confrontation naming was predictive of RM impairment group membership.

Conclusions: Our results demonstrate individuals with aMCI are heterogeneous and show variability in RM discriminability. RM performance was associated with measures of language, elucidating patterns of cognition potentially marking those more likely to progress to AD. Future studies need to address this finding in a longitudinal sample.     

Clinical measures of prospective memory in amnestic mild cognitive impairment

Recent research has established that individuals with amnestic mild cognitive impairment (aMCI) have impaired prospective memory (PM); however, findings regarding differential deficits on time-based versus event-based PM have been less clear. Furthermore, the diagnostic utility of PM measures has received scant attention. Healthy older adults (n = 84) and individuals with aMCI (n = 84) were compared on the Cambridge Prospective Memory Test (CAMPROMPT) and two single-trial event-based PM tasks. The aMCI participants showed global impairment on all PM measures. Measures of retrospective memory and complex attention predicted both time and event PM performance for the aMCI group. Each of the PM measures was useful for discriminating aMCI from healthy older adults and the time- and event-based scales of the CAMPROMPT were equivalent in their discriminative ability. Surprisingly, the brief PM tasks were as good as more comprehensive measures of PM (CAMPROMPT) at predicting aMCI. Results indicate that single-trial PM measures, easily integrated into clinical practice, may be useful screening tools for identifying aMCI. As PM requires retrospective memory skills along with complex attention and executive skills, the interaction between these skills may explain the global PM deficits in aMCI and the good discriminative ability of PM for diagnosing aMCI.     

Concurrent impairments in sleep and memory in amnestic mild cognitive impairment

Whereas patients with Alzheimer's disease (AD) experience difficulties forming and retrieving memories, their memory impairments may also partially reflect an unrecognized dysfunction in sleep-dependent consolidation that normally stabilizes declarative memory storage across cortical areas. Patients with amnestic mild cognitive impairment (aMCI) exhibit circumscribed declarative memory deficits, and many eventually progress to an AD diagnosis. Whether sleep is disrupted in aMCI and whether sleep disruptions contribute to memory impairment is unknown. We measured sleep physiology and memory for two nights and found that aMCI patients had fewer stage-2 spindles than age-matched healthy adults. Furthermore, aMCI patients spent less time in slow-wave sleep and showed lower delta and theta power during sleep compared to controls. Slow-wave and theta activity during sleep appear to reflect important aspects of memory processing, as evening-to-morning change in declarative memory correlated with delta and theta power during intervening sleep in both groups. These results suggest that sleep changes in aMCI patients contribute to memory impairments by interfering with sleep-dependent memory consolidation.     

Different mechanisms of episodic memory failure in mild cognitive impairment

Mild cognitive impairment (MCI), defined as episodic memory impairment beyond what is expected in normal aging, is often associated with hippocampal atrophy (HA) and may represent incipient Alzheimer's disease. However, recent studies suggest that MCI is very heterogeneous and multiple etiologies likely exist. One possibility is small vessel cerebrovascular disease (CVD). Specifically, we hypothesized that white matter hyperintensities (WMH), an MRI marker for CVD, would lead to impairments in executive control processes critical for working memory that may, in turn, result in episodic memory impairment. To test this hypothesis, we examined a group of subjects clinically diagnosed with MCI and used MRI to further subcategorize individuals as either MCI with severe white matter hyperintensities (MCI-WMH) or MCI with severe hippocampal atrophy (MCI-HA). MCI-WMH, MCI-HA, and matched control subjects each performed a battery of working memory and episodic memory tasks. Results showed that MCI-HA and MCI-WMH were equally impaired on the episodic memory task relative to controls, but MCI-WMH were additionally impaired on tests tapping verbal and spatial working memory abilities and attentional control processes. These results suggest that CVD and hippocampal dysfunction are associated with distinct neuropsychological profiles. Although both syndromes are associated with episodic memory deficits, CVD is additionally associated with working memory and executive control deficits.     

Group external memory aid treatment for mild cognitive impairment

Background: Although individuals with mild cognitive impairment (MCI) often live independently, instruction on compensatory strategies could assist individuals with complex daily tasks. External memory aids (EMA) are evidence-based compensatory strategies that support cognitive communication impairments. Often EMAs are included within multi-strategy-based interventions; however, limited research has examined solely training several EMAs to individuals with mild memory impairments and the long-lasting outcomes.

Aims: The aims of this study were to examine the effect of structured group EMA treatment for individuals with possible MCI on their: (1) functional use of EMAs to compensate for memory impairments compared to before treatment; (2) cognitive skills post-treatment; and (3) do these changes maintain for 6 weeks and 18 months following intervention.

Methods & Procedures: The researchers employed an experimental pre-/post-group treatment design and collected 6-week and 18-month follow-up data. Six participants were divided into two groups. Participants completed 6 weekly group treatment sessions training three categories of EMAs. Group 1 began treatment immediately and Group 2 started treatment following the conclusion of treatment for Group 1.

Outcomes and Results: Participants increased their functional EMA use following treatment on a Role Play Activity. Group mean scores on the Montreal Cognitive Assessment (Nasreddine et al., 2005) increased following treatment. Inconsistent retention of skills was documented for both functional EMA use and cognitive skills during follow-up assessment.

Conclusions: With treatment, individuals with possible MCI learned to use EMAs during functional activities. Mixed results related to retention of skills indicated the potential importance of booster treatment to reinforce EMA use. Future research should aim to investigate additional methods to measure functional EMA use prior to and following intervention.     

遗忘型轻度认知损害患者的前瞻性记忆障碍

目的 探讨遗忘型轻度认知损害(amnesia mild cognitive impairment,aMCI)患者前瞻性记忆(prospective memory,PM)改变的特征,初步了解基于事件的PM(event-based prospective memory,EBPM)和基于时间的PM(time-based prospective memory,TBPM)在aMCI患者中的损害情况.方法 建立PM的神经心理学测验方法,对30例aMCI患者以及年龄、受教育程度相匹配的30名健康老年人进行测试.结果 与健康对照组[EBPM:(2.33±0.66)分、TBPM:(4.90±1.03)分]相比,aMCI组的EBPM成绩[(0.90±1.09)分]和TBPM成绩[(4.23 ±1.14)分]差异均有统计学意义(t=-6.143,P<0.01;t=-2.383,P<0.05).结论 aMCI患者的记忆障碍不仅表现为回顾性记忆(retrospective memory,RM)损害,PM损害可能更为突出,且EBPM的损害程度大于TBPM和RM,提示EBPM的测查可能有利于aMCI的早期识别.     

Subtle memory decline over 12 months in mild cognitive impairment

OBJECTIVE: Screening of normal older persons for progressive memory decline is a worthwhile strategy in the pursuit of the earliest possible stages of pre-clinical Alzheimer's disease (AD) or mild cognitive impairment (MCI). Reliable tests are needed to both detect MCI and measure the natural history of decline over months rather than years. We aimed to detect memory decline over 1 year in a group of older individuals with well-characterised amnestic MCI. METHODS: The continuous learning task (CLT) from the CogState test battery was administered 8 times in 12 months to 15 individuals with MCI and 35 controls matched for age, education, IQ and gender. All subjects were recruited from an ongoing aging study. The rate of change in CLT performance over the year was compared between groups and also compared to that detected with a word list learning task and a computerised paired associate learning task. RESULTS: At baseline, memory performance in the amnestic MCI group was significantly worse than controls on all memory tests. However, at 12 months the magnitude of the difference between the groups had increased significantly on the CLT due to decline in memory accuracy in the MCI group. No decline over 12 months was detectable on the routine memory tests. CONCLUSIONS: Subtle memory decline is detectable in amnestic MCI using reliable and sensitive tests of memory. Such measures may assist in the early identification of AD and also in trials of putative disease-modifying therapies to be conducted over as little as 12 months.     

轻度认知障碍患者视空间工作记忆的变化

目的 探索轻度认知障碍(MCI)患者视空间工作记忆的广度和准确度的变化.方法 根据临床记忆检查和Blessed-Roth生活评定结果诊断的MCI患者20例和与之匹配的正常对照20例进行扫视记忆和重现数字位置的试验.结果 MCI组扫视记忆的正确率比对照组下降,差异有统计学意义(P<0.05).扫视的平均速度与对照组的差异无统计学意义(P>0.05).两组能正确记忆位置的数字个数差异无统计学意义(P>0.05),为达到最好的记忆效果,MCI组需要数字呈现的时间比对照组长,差异有统计学意义(P<0.05).结论 MCI患者视觉空间工作记忆的中央执行系统运转正常,视空间模板的存贮空间保留,视空间工作记忆的广度正常,而视空间初步加工系统中两种次级记忆的准确性下降,导致视空间工作记忆的准确度下降.