Can episodic memory tasks differentiate semantic dementia from Alzheimer's disease?

The performance of two groups of patients with semantic dementia (SD), with predominant right (SDR) and left temporal lobe atrophy (SDL), was contrasted with that of cases with probable Alzheimer's disease (AD) on a range of standard episodic memory tasks. While the SDL group achieved a good score on a composite visual, but not a verbal, episodic memory measure, the AD and SDR groups were equivalently impaired at visual and verbal memory. The SD, but not the AD, groups were, by definition, impaired on simple tests of semantic memory. Standard verbal episodic memory tests, therefore, failed to discriminate patients with SD from those with probable AD and even visual memory tests may result in misclassification of SDR cases.     

Perception, attention, and working memory are disproportionately impaired in dementia with Lewy bodies compared with Alzheimer's disease

OBJECTIVE: To test the hypotheses that visuoperceptual and attentional ability are disproportionately impaired in patients having dementia with Lewy Bodies (DLB) compared with Alzheimer's disease (AD). METHODS: A comprehensive battery of neuropsychological tasks designed to assess working, episodic, and semantic memory, and visuoperceptual and attentional functions was given to groups of patients with DLB (n=10) and AD (n=9), matched for age, education, and mini mental state examination (MMSE), and to normal controls (n=17). RESULTS: Both patient groups performed equally poorly on tests of episodic and semantic memory with the exception of immediate and delayed story recall, which was worse in the AD group. Digit span was by contrast spared in AD. The most striking differences were on tests of visuoperceptual/spatial ability and attention. Whereas patients with AD performed normally on several subtests of the visual object and space perception battery, the DLB group showed substantial impairments. In keeping with previous studies, the AD group showed deficits in selective attention and set shifting, but patients with DLB were more impaired on virtually every test of attention with deficits in sustained, selective, and divided attention. CONCLUSIONS: Patients with DLB have substantially greater impairment of attention, working memory, and visuoperceptual ability than patients with AD matched for overall dementia severity. Semantic memory seems to be equally affected in DLB and AD, unlike episodic memory, which is worse in AD. These findings may have relevance for our understanding of the genesis of visual hallucinations, and the differential diagnosis of AD and DLB.     

Patterns of impairment in autobiographical memory in the degenerative dementias constrain models of memory

Detailed study of the autobiographical memory (ABM) impairments seen in different forms of degenerative dementia, in particular Alzheimer's disease (AD) and semantic dementia (SD) can inform neuropsychological models of memory. A modified ABM questionnaire which allowed more detailed analysis of episodic and semantic ABM was used to study the pattern of deficits in patients with minimal to mild Alzheimer's disease (AD) and in two patients with mild and moderate semantic dementia (SD). The questionnaire tested both cued and free recall. A group of healthy elderly was also tested. AD patients differed from controls in all measures. There was no clear temporal gradient for episodic ABM, but a modest gradient was observed for semantic ABM. The mild SD patient performed at control level for episodic ABM but showed a deficit within the range of the AD patients for semantic ABM except for the most recent life period. In contrast the moderate SD patient was impaired within the range of the AD patients for both episodic and semantic ABM. The evidence for differential impairment of episodic and semantic ABM retrieval in AD and SD is interpreted as supporting the multiple trace model of memory.     

The nature and staging of attention dysfunction in early (minimal and mild) Alzheimer's disease: relationship to episodic and semantic memory impairment

The development of cholinergic therapies for Alzheimer's disease (AD) has highlighted the importance of understanding the role of attentional deficits and the relationship between attention and memory in the earliest stages of the disease. Variability in the tasks used to examine aspects of attention, and in the disease severity, between studies makes it difficult to determine which aspects of attention are affected earliest in AD, and how attentional impairment is related to other cognitive modules. We tested 27 patients in the early stages of the disease on the basis of the MMSE (minimal 24-30 corresponding to minimal cognitive impairment, very mild or possible AD in other classifications; and mild 18-23) on a battery of attentional tests aimed to assess sustained, divided, and selective attention, plus tests of episodic memory, semantic memory, visuoperceptual and visuospatial function, and verbal short-term memory. Although the mildly demented group were impaired on all attentional tests, the minimally impaired group showed a preserved ability to sustain attention, and to divide attention based on a dual-task paradigm. The minimally demented group had particular problems with response inhibition and speed of attentional switching. Examination of the relationship between attention and other cognitive domains showed impaired episodic memory in all patients. Deficits in attention were more prevalent than deficits in semantic memory suggesting that they occur at an earlier stage and the two were partially independent. Impairment in visuoperceptual and visuospatial functions and verbal short-term memory were the least common. Although attention is impaired early in AD, 40% of our patients showed deficits in episodic memory alone, confirming that amnesia may be the only cognitive deficit in the earliest stages of sporadic AD.     

Episodic and semantic memory in children with mesial temporal sclerosis

The aim of this study was to analyze semantic and episodic memory deficits in children with mesial temporal sclerosis (MTS) and their correlation with clinical epilepsy variables. For this purpose, 19 consecutive children and adolescents with MTS (8 to 16 years old) were evaluated and their performance on five episodic memory tests (short- and long-term memory and learning) and four semantic memory tests was compared with that of 28 healthy volunteers. Patients performed worse on tests of immediate and delayed verbal episodic memory, visual episodic memory, verbal and visual learning, mental scanning for semantic clues, object naming, word definition, and repetition of sentences. Clinical variables such as early age at seizure onset, severity of epilepsy, and polytherapy impaired distinct types of memory. These data confirm that children with MTS have episodic memory deficits and add new information on semantic memory. The data also demonstrate that clinical variables contribute differently to episodic and semantic memory performance.     

An fMRI study of verbal episodic memory encoding in amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) is a high-risk and often prodromal state for the development of Alzheimer's disease (AD) and is characterised by isolated episodic memory impairment. Functional neuroimaging studies in healthy subjects consistently report left prefrontal cortex (PFC) activation during verbal episodic memory encoding. The PFC activation at encoding is related to semantic processing which enhances memory. The purpose of this study was to ascertain whether impaired verbal episodic memory in aMCI is related to PFC dysfunction. Using functional magnetic resonance imaging (fMRI) we compared 10 aMCI patients with 10 elderly controls during verbal encoding. The encoding task was sensitive to the effects of semantic processing. Subsequent recognition was tested to measure encoding success. Behavioural results revealed impaired recognition and a lower false recognition rate for semantically related distracters (lures) in aMCI, which suggest impaired semantic processing at encoding. Both groups activated left hemispheric PFC, insula, premotor cortex and cerebellum, but group comparisons revealed decreased activation in left ventrolateral PFC in the aMCI group. The magnitude of activation in left ventrolateral PFC during encoding was positively correlated with recognition accuracy in the control group but not in the aMCI group. We propose that verbal episodic memory impairment in aMCI is related to PFC dysfunction which affects semantic processing at encoding.     

Episodic, semantic and procedural memory in a case of amnesia at an early age

The patient C.C. developed an amnesic syndrome at the age of 10 yr. Like adult amnesics, C.C. demonstrated impaired episodic memory for both verbal and visual materials although immediate memory span was spared. However, striking deficits were also observed on a wide variety of semantic memory tasks, including reading vocabulary and verbal fluency tests, semantic classification and lexical decision tasks and tests of verbal intelligence. On the other hand, C.C. showed normal learning and retention of two procedural tasks. It was argued that this evidence is inconsistent with the view that the amnesic syndrome represents a selective defect of episodic memory that leaves semantic memory relatively unaffected.     

Memory impairment differs in frontotemporal dementia and Alzheimer's disease

The aim of this study was to assess short-term and long-term explicit memory and implicit memory in frontotemporal dementia (FTD; frontal variant) and to compare FTD and Alzheimer's disease (AD) patients with similar severity of dementia. Fifteen FTD patients [mean age: 68 years; Mini-Mental State (MMS): 24], 30 probable AD patients (mean age: 72 years; MMS: 23) and 12 healthy subjects participated in the study. The three groups were comparable in terms of gender and educational level. Short-term memory was assessed with the digit span and Corsi block-tapping tests. Explicit verbal memory was assessed with the Grober and Buschke test, and implicit memory with a verbal priming task and a fragmented picture test. FTD patients demonstrated a genuine memory deficit with impaired digit span, encoding deficit and retrieval strategy difficulties, but preserved implicit verbal and visual priming. Memory patterns differed in AD and FTD: short-term memory and free recall were similarly decreased in FTD and AD but cues provided more benefit to FTD than to AD; encoding was more impaired and the forgetting rate was faster in AD than in FTD; priming was lower in AD than in FTD. AD patients with clinical and imaging frontal lobe dysfunction tended to have lower memory performance and to differ even more from FTD patients than AD patients without frontal lobe dysfunction.     

抑郁症和早期阿尔茨海默病的记忆和执行功能

目的 研究抑郁症和早期阿尔茨海默病(AD)的神经心理学特征,试图运用神经心理学评估对两者进行鉴别。方法 对32例单相抑郁症、38例早期AD和34例对照进行WHO-UCLA词语学习、词语流畅、复杂图形和逻辑记忆的评估。结果 早期AD组神经心理学测验得分最低,抑郁症组次之,对照组最高,3组之间有显著性差异(P<0.01);抑郁症组仅表现为词语学习和逻辑记忆的自由回忆以及语义流畅的损害(P<0.05),而早期AD组表现为全面的认知功能损害(P<0.01);逐步判别分析提示,复杂图形延迟自由回忆、词语学习长时延迟自由回忆和语义流畅是区分抑郁症组和早期AD组的重要指标。结论 抑郁症和早期AD认知功能损害的特征不同,长时延迟自由回忆、再认和语义流畅能够区分早期AD和抑郁症。     

Semantic memory in partial epilepsy: verbal and non-verbal deficits and neuroanatomical relationships

Semantic memory was evaluated in 124 epilepsy patients, including 84 with left (n=44) or right temporal lobe epilepsy (TLE) (n=40) and 40 with left (n=25) or right frontal lobe epilepsy (FLE) (n=15), in order to determine their verbal and visual deficits, and the neuroanatomical relationships between them. The controls were 35 healthy subjects. Semantic memory was assessed by means of Picture Naming, Picture Pointing, the verbal Pyramid and Palm Trees Test (PPTT), the visual PPTT, Object Decision Hard, and Drawing From Memory. Episodic memory was assessed by means of the Short Story, Rey's Complex Figure, the Verbal and Visual Selective Reminding Procedure and Brown-Peterson Procedure. Factor analysis of the epilepsy patients distinguished their semantic memory scores from other neuropsychological domains. The semantic memory factor was significantly related to the side of the epileptic region, with lower scores in the left hemisphere and left TLE patients. In comparison with the controls, the left TLE patients were significantly impaired on Picture Naming, Picture Pointing, and Object Decision Hard. Subsequent analyses showed that, in comparison with the controls and the right TLE patients, the left TLE patients with lateral temporal lobe lesions were impaired in Picture Naming whereas, in comparison with the controls, the left TLE patients with mesial temporal lobe lesions were impaired in Object Decision Hard. On the contrary, the episodic memory factor was not related to the side of the epileptic region, and a few material-specific tests revealed opposite impairments in the left and right hemisphere patients. These results show that left TLE may cause semantic memory deficits involving verbal and visual information. Unlike the material-specific pattern of episodic memory, this pattern of impairment is in line with the view of an amodal semantic store in which all of the information about a thing overlaps. The semantic memory impairment may reflect damage in the lateral and mesial temporal lobe regions that impair neocortical functions in storing and retrieving information or hippocampal functions in processing meaningful stimuli.     

Relationship of Age at Onset, Chronologic Age, and Adequacy of Preoperative Performance to Verbal Memory Change After Anterior Temporal Lobectomy

Summary We examined the relationship of age of onset of epilepsy, chronological age at time of operation, and adequacy of preoperative memory performance to pre- to postoperative verbal memory decline. Patients who underwent left (n = 50) or right (n = 51) anterior temporal lobectomy (ATL) were administered tests of verbal episodic (list learning, paragraph recall) and semantic memory (visual naming, vocabulary), both preoperatively and 6 months postoperatively. As a group, left ATL patients showed the classic selective decrease on measures of episodic but not semantic memory. However, examination of episodic memory outcome showed considerable individual variability. Stepwise regression analyses indicated that both later age at onset and older chronologic age were significant and selective predictors of episodic memory decrease for left ATL patients. Adequacy of preoperative memory performance was a nonspecific predictor, associated with decrease in postoperative memory performance for both left and right ATL patients and for multiple types of memory indices. The clinical and theoretical implications are discussed.     

Multidimensional measures of person knowledge and spatial associative learning: can these be applied to the differentiation of Alzheimer's disease from frontotemporal and vascular dementia?

Patients with early stage Alzheimer's disease (AD) show deficits in person knowledge and spatial associative memory. The current investigation examined the ability of impairment in these domains to differentiate AD from other overlapping conditions. In experiment 1, 14 AD patients, 21 vascular dementia (VaD) patients, 11 frontal variant frontotemporal dementia (fvFTD) patients and 41 controls were administered a graded faces test. VaD patients demonstrated a level of impairment comparable to the AD group on both the naming and person identification elements of the task. A mild naming deficit was revealed in the fvFTD group. In experiment 2, 22 AD patients, 23 patients with mild cognitive impairment (MCI), 11 fvFTD patients, 13 semantic dementia (SD) patients, and 23 elderly controls were administered the face-place test, a newly developed task that combines naming of famous faces, item recognition and spatial location. The naming component of the face-place test clearly differentiated SD patients from all dementia groups. All patient groups, except those with fvFTD, showed substantial deficits in the item recognition and spatial components. Consistency analyses indicated a fairly robust association between the two episodic components (item recognition and placing), but not between semantic and episodic elements of the FPT. Person knowledge deficits are, therefore, not specific to AD and the employment of face stimuli may influence the performance of SD patients on tasks of episodic memory.     

Naming of objects, faces and buildings in mild cognitive impairment

Accruing evidence suggests that the cognitive deficits in very early Alzheimer's Disease (AD) are not confined to episodic memory, with a number of studies documenting semantic memory deficits, especially for knowledge of people. To investigate whether this difficulty in naming famous people extends to other proper names based information, three naming tasks – the Graded Naming Test (GNT), which uses objects and animals, the Graded Faces Test (GFT) and the newly designed Graded Buildings Test (GBT) – were administered to 69 participants (32 patients in the early prodromal stage of AD, so-called Mild Cognitive Impairment (MCI), and 37 normal control participants). Patients were found to be impaired on all three tests compared to controls, although naming of objects was significantly better than naming of faces and buildings. Discriminant analysis successfully predicted group membership for 100% controls and 78.1% of patients. The results suggest that even in cases that do not yet fulfil criteria for AD naming of famous people and buildings is impaired, and that both these semantic domains show greater vulnerability than general semantic knowledge. A semantic deficit together with the hallmark episodic deficit may be common in MCI, and that the use of graded tasks tapping semantic memory may be useful for the early identification of patients with MCI.     

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.     

Memory failure has different mechanisms in subcortical stroke and Alzheimer's disease

Patients with extensive subcortical cerebrovascular disease may have impaired memory, often despite the absence of medial temporal or diencephalic strokes. In this group, episodic memory failure may arise from frontal lobe dysfunction based on disruption of frontosubcortical loops caused by lacunae. We tested this idea by studying cognitively impaired subcortical stroke (CIS) patients and Alzheimer's disease (AD) patients with [18F]-fluorodeoxyglucose positron emission tomography using a continuous verbal memory task during the period of tracer uptake. Patients were matched on severity of cognitive impairment and overall memory task performance. As hypothesized, we found a double dissociation in the relations between metabolism and memory in these groups, such that memory in CIS (but not in AD) correlates with prefrontal lobe metabolism, whereas in AD (but not in CIS), memory correlates with left hippocampal and temporal lobe metabolism. Analysis of memory subscores showed that CIS patients made more errors on short-delay trials, which is consistent with working memory failure. It seems that different pathogenic mechanisms underlie episodic memory failure in subcortical cerebrovascular disease and AD.     

Memory failure in binswanger's disease and alzheimer's disease

The heterogeneity within vascular dementia has made neuropsychological research in this area difficult to interpret. We studied a subtype of vascular dementia, Binswanger's disease (BD), diagnosed according to recently specified clinical and radiological criteria. Measures of episodic and semantic memory were administered to BD patients, patients with Alzheimer's disease (AD) comparable to the BD sample in dementia severity, age, and education, and normal controls. Episodic memory was more defective in AD than in BD; these patient groups were equally impaired on measures of semantic memory. The findings suggest that assessment of episodic memory may be useful in differentiating AD from BD.     

Memory Performances in Young,Elderly, and Very Old Healthy Individuals versus Patients with Alzheimer's Disease: Evidence for Discontinuity Between Normal and Pathological Aging

In this study we compared memory performances of 29 probable patients with AD (17 mildly and 12 moderately demented) with those of 39 healthy young subjects, 36 elderly subjects (matched with the AD group for age and years of schooling), and 19 healthy very old subjects. In most of the memory tasks used in the present study, a progressive decline in performance was observed passing from the Young to the Elderly to the Very Old to the AD group. However, patients with AD were selectively impaired in the backward reproduction of verbal and spatial span sequences and in the semantic encoding of verbal material. These data are consistent with the hypothesis of not only quantitative but also a qualitative discontinuity between the process of normal aging and the dementia syndrome.     

Differential neuropsychological patterns of frontal variant frontotemporal dementia and Alzheimer's disease in a study of diagnostic concordance

Although the pathological hallmarks of Alzheimer's disease (AD) and frontal variant frontotemporal dementia (fvFTD) predict different cognitive patterns, many comparative neuropsychological studies showed no difference in the expected cognitive domains. Inconsistencies in diagnostic criteria, small cohorts of patients, and neuropsychological assessment may account for such findings. Moreover, discrepancies in memory and executive dysfunctions that are expected to distinguish AD and fvFTD may reflect the basic brain organization. Adhering to a strict concordance of clinical and neuroradiological criteria, we compared many patients with AD and fvFTD using a large neuropsychological battery. One hundred and thirty-nine patients with AD (n = 89) or fvFTD (n = 50) were retrospectively considered in order to verify the diagnostic congruence of clinical and neuroradiological aspects. On this basis, 117 patients with AD (n = 77) or fvFTD (n = 40) with similar duration and severity of dementia were selected. Ninety-one healthy subjects were also controlled. Mean scores in tests for abstract reasoning, planning, set shifting, initiative, verbal fluency, immediate and episodic memory, constructive, ideomotor and orofacial praxis, selective and divided attention, visuomotor coordination, and visual perception were evaluated. Separate analyses of variance and post hoc Bonferroni tests showed that, with respect to controls, both patient groups were significantly impaired in all neuropsychological tests. Compared to fvFTD patients, AD patients were significantly impaired in episodic memory, selective attention, visual perception, visuomotor coordination, and constructive praxis, whereas no differences were found in executive, intellective, and linguistic abilities between the two patient groups. Logistic regression analyses revealed that episodic memory significantly predicted the diagnosis of AD while no executive deficit was able to predict the diagnosis of fvFTD. To conclude, memory, attention, and visuoconstructive deficits may distinguish AD with respect to fvFTD, in accordance with the severe temporo-parietal-occipital degeneration characterizing AD, but no executive impairment is consistently able to identify a relative compromise in fvFTD. Executive functions impairments possibly reflect the altered spatial–temporal integration of the frontal lobes with different brain areas, which prevents a clear-cut cognitive-brain correlation.     

Differential mechanisms of impairment of remote memory in Alzheimer's and frontotemporal dementia

This paper describes retrograde memory performances of 12 Alzheimer's disease (AD) patients and 12 frontotemporal dementia (FTD) patients. First of all, we observed that FTD and AD patients did not differ for language tests (verbal fluency tests and oral denomination 80), for semantic memory tests, for logical memory test and Benton visual memory test and differed for anterograde verbal memory and frontal tests. Concerning retrograde memory, there was no difference between AD and FTD patients in retrograde memory scores (autobiographical memory interview, Crovitz's task, French public events interview battery) and both FTD and AD patients exhibited a retrieval deficit in their remote memory. We observed that the mechanisms of remote memory deficit was different in FTD and in AD patients. We observed no classical paradigm of Ribot for FTD patient's remote informations, and they appeared to have lost of access to memories and executive difficulties. In AD, the results indicated these patients' ability to learn new information and to search semantic memory failed.     

Common and unique gray matter correlates of episodic memory dysfunction in frontotemporal dementia and alzheimer's disease

Conflicting evidence exists regarding the integrity of episodic memory in the behavioral variant of frontotemporal dementia (bvFTD). Recent converging evidence suggests that episodic memory in progressive cases of bvFTD is compromised to the same extent as in Alzheimer's disease (AD). The underlying neural substrates of these episodic memory deficits, however, likely differ contingent on dementia type. In this study we sought to elucidate the neural substrates of episodic memory performance, across recall and recognition tasks, in both patient groups using voxel‐based morphometry (VBM) analyses. We predicted that episodic memory dysfunction would be apparent in both patient groups but would relate to divergent patterns of neural atrophy specific to each dementia type. We assessed episodic memory, across verbal and visual domains, in 19 bvFTD, 18 AD patients, and 19 age‐ and education‐matched controls. Behaviorally, patient groups were indistinguishable for immediate and delayed recall, across verbal and visual domains. Whole‐brain VBM analyses revealed regions commonly implicated in episodic retrieval across groups, namely the right temporal pole, right frontal lobe, left paracingulate gyrus, and right anterior hippocampus. Divergent neural networks specific to each group were also identified. Whereas a widespread network including posterior regions such as the posterior cingulate cortex, parietal and occipital cortices was exclusively implicated in AD, the frontal and anterior temporal lobes underpinned the episodic memory deficits in bvFTD. Our results point to distinct neural changes underlying episodic memory decline specific to each dementia syndrome. Hum Brain Mapp 35:1422–1435, 2014. © 201 Wiley Periodicals, Inc.