Semantic fluency in Alzheimer's, Parkinson's, and Huntington's disease: Dissociation of storage and retrieval failures.

Patients with Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and normal controls were compared on 2 versions of a semantic fluency task: a standard, uncued version and a version in which Ss were cued with subordinate categories. All patients were impaired relative to controls on the standard version. On the cued version, PD and HD patients improved significantly, but AD patients did not. AD patients' fluency, but not PD or HD patients', correlated significantly with confrontation naming ability. Impairment exhibited by PD and HD patients on standard semantic fluency tasks may be due to a retrieval deficit, whereas that of AD patients may be due to degradation of semantic memory stores. In addition, the pattern of performance exhibited by a nonaphasic patient with bilateral frontal lobe lesions suggests that the retrieval functions involved may depend on integrity of the prefrontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory encoding and retrieval in frontotemporal dementia and Alzheimer's disease.

Memory encoding and retrieval strategies were assessed in patients with behavior-executive variant frontotemporal dementia (FTD), language variant FTD, and Alzheimer's disease (AD) using verbal and visuospatial supraspan learning tests. FTD patients obtained higher free recall, cued recall, and recognition scores than AD patients. Comparison of free recall scores with cued recall and recognition scores was similar in the 3 dementia groups. Groups did not differ in semantic clustering strategies during learning, but serial-order recall was more common in FTD patients. These data do not support the idea that FTD patients' poor memory is due to a selective retrieval disorder, though FTD patients may fail to implement sophisticated organizational strategies during learning. FTD patients' retained capacity for encoding new information into long-term declarative memory is likely due to relatively spared medial temporal lobe involvement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extent, pattern, and correlates of remote memory impairment in Alzheimer's disease and Parkinson's disease.

Content and contextual memory for remote public figures and events was assessed with a modified version of the Presidents Test in patients with Alzheimer's disease (AD) or Parkinson's disease (PD). Contributions of executive functioning, semantic memory, and explicit anterograde memory to remote memory abilities were also examined. The AD group had temporally extensive deficits in content and contextual remote memory not accountable for by dementia severity. The PD group did not differ from the control group in remote memory, despite anterograde memory impairment. These results support the position that different component processes characterize remote memory, various mnemonic and nonmnemonic cognitive processes contribute to remote memory performance, and anterograde and remote memory processes are dissociable and differentially disrupted by neurodegenerative disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition by familiarity is preserved in Parkinson's without dementia and Lewy-Body disease.

Objective: The retrieval deficit hypothesis states that the lack of deficit in recognition often observed in patients with Parkinson's disease is because of the low retrieval requirements of the task, given that these patients have retrieval and not encoding deficits. To test this hypothesis we investigated recognition memory by familiarity in Parkinson's patients and in patients with Lewy Bodies disease and Parkinson with dementia. Method: We analyzed to what extent the experimental groups were able to recognize by familiarity in a typical yes/no recognition memory task. The experimental groups were patients with early nondemented Parkinson's disease, advanced nondemented Parkinson's disease, demented Parkinson's patients, and patients with dementia with Lewy Bodies. We compared their performance with a group of young and another group of old healthy participants. The estimation of familiarity was made by analyzing recognition of word targets and distractors consisting of combinations of different letters in comparison with a condition in which targets and distractors were composed of similar letters, even though subjects were unaware of the independent variable. Results: The results indicate that familiarity was used at the same level by controls, patients with early Parkinson's disease and patients with dementia with Lewy Bodies. Although late Parkinson patients also used familiarity, its effect was only marginally significant. Patients with Parkinson's disease and dementia were not capable of using familiarity in recognition memory. Conclusions: Our results support the retrieval deficit hypothesis as Parkinson's patients without dementia show no deficit in a situation in which the retrieval requirements are minimal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic memory in Alzheimer's disease and the frontotemporal dementias: A longitudinal study of 236 patients.

Using semantic dementia (SD) as a reference point, the authors assessed semantic memory in four other neurodegenerative disorders: progressive nonfluent aphasia (PNFA), frontal variant frontotemporal dementia (fvFTD), Alzheimer's disease (AD), and posterior cortical atrophy (PCA). Individuals with SD were more impaired than other groups on semantic measures and showed a characteristic pattern across tasks: category fluency (CF) worse than letter fluency (LF), naming worse than comprehension, and visual and verbal comprehension equally affected, suggesting disruption to an amodal semantic system. Individuals with AD demonstrated a similar pattern to a milder degree. Although PNFA, fvFTD, and PCA groups had abnormal scores (relative to controls) on most semantic measures, their differing patterns across measures indicate that the apparent semantic impairment in these conditions is largely secondary to other factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological and neuroradiological distinctions between Alzheimer's and Huntington's diseases.

Examined neuropsychological and magnetic resonance imaging (MRI) differences among 23 Ss (mean age 70 yrs) with Alzheimer's disease (AD), 9 Ss (mean age 49.2 yrs) with Huntington's disease (HD), and 13 normal controls (mean age 71.7 yrs). Neuropsychological results show that HD Ss' episodic and semantic memory deficits were attributable to retrieval deficiencies, whereas AD Ss' impairments reflected a lack of storage and a breakdown in the structure of semantic knowledge. MRI results show that these cognitive changes were mirrored by significant group differences in striatal and cortical degeneration. AD Ss evidenced more widespread cortical damage, and HD Ss showed more striatal destruction. Both groups evidenced significant deterioration in medial temporal lobe and diencephalic structures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of neuropsychological functioning in Alzheimer's disease and frontotemporal dementia

Neuropsychological changes distinguishing mild Alzheimer's disease (AD) from frontotemporal dementia (FTD) have been described, but empirical verification of differential cognitive characteristics is lacking. Archival neuropsychological data on 15 FTD patients, 16 AD patients, and 16 controls were compared. Controls outperformed both patient groups on measures of verbal and nonverbal memory, executive ability, and constructional skill, with AD patients showing more widespread memory decline. No differences were found between the 3 groups in confrontation naming, recognition memory, or basic attention. Patient groups differed only in nonverbal memory, with FTD patients performing significantly better than AD patients. However, patient groups also differed in pattern of performance across executive and memory domains. Specifically, AD patients exhibited significantly greater impairment on memory than executive tasks, whereas the opposite pattern characterized the FTD group. These findings suggest that examination of relative rankings of scores across cognitive domains, in addition to interpretation of individual neuropsychological scores, may be useful in differential diagnosis of FTD versus AD.     

Naming in dementia secondary to Parkinson's, Huntington's, and Alzheimer's diseases

Confrontation naming problems have been found in patients with dementia secondary to Alzheimer's (AD), Huntington's (HD), and in a subset of Parkinson's disease (PD) patients with dementia. The source of the naming deficit has not been established. The "Perception" and the "Semantic Feature" theories have been proposed to explain this naming dysfunction. Subjects with dementia secondary to AD, HD, and PD were given three tasks to determine which theory best explained the source of confrontation naming problems. The three tasks including picture matching, visual recognition, and confrontation naming were given to 42 subjects with dementia secondary to AD, HD, and PD controlled for severity of dementia, and to age-matched controls. Subjects with dementia did not have significantly more difficulty matching pictures but did have more difficulty associating pictures through semantic features. Subjects with mild dementia secondary to AD and HD had significantly more confrontation naming errors than subjects with mild dementia secondary to PD and normal controls. All subjects with moderate dementia had significantly more confrontation naming errors than normal controls. Statistical power may have been limited due to the small number of subjects in each group. The source of the reduction in confrontation naming performance in subjects with dementia secondary to AD, HD, and PD originated in the deterioration of semantic fields. The perception theory was rejected as findings were consistent with the semantic feature theory.     

The disparate effects of Alzheimer's disease and Huntington's disease on semantic memory.

Alzheimer's disease (AD) and Huntington's disease (HD) impair performance on semantic memory tasks, but researchers disagree on whether AD and HD cause these impairments in the same manner. According to one view, AD disrupts the storage of semantic memories, whereas HD disrupts the retrieval of semantic memories. Dissenters argue that AD, like HD, disrupts retrieval. In this study, participants generated category exemplars (e.g., kinds of fruits) for 1 min, and response latencies were examined. Relative to healthy controls, the 12 AD patients produced a larger proportion of responses earlier in the recall period, consistent with the view that AD patients quickly exhaust their limited supply of items in storage. By contrast, the 12 HD patients produced a larger proportion of their responses late in the recall period, consistent with the view that HD slows retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory profiling with paired associate learning in Alzheimer's disease, mild cognitive impairment, and healthy aging.

Mild cognitive impairment (MCI) is associated with increased risk of developing Alzheimer's disease (AD), but up to 40% of cases do not develop AD. Examining a case's specific memory profile may help distinguish which MCI cases will progress to AD: An encoding profile is suggestive of incipient AD, whereas a retrieval profile suggests an alternative etiology. Paired associate learning (PAL) tasks are sensitive for preclinical and early detection of AD, but existing tasks do not enable memory profiling. We developed a novel PAL task enabling the differentiation of memory profiles in 19 people with AD, 17 people with amnestic MCI, and 33 normal elderly controls. Unexpectedly, the AD group demonstrated a retrieval profile for PAL using yes-no recognition, although an encoding profile was evident for forced-choice recognition and for the California Verbal Learning Test--Second Edition (Delis, Kramer, Kaplan, & Ober, 2000). There was considerable heterogeneity within the AD and MCI groups as well as intraindividual discordance for memory profiles. The findings challenge the clinical application of memory profiling in the differential diagnosis of AD, and, by extension, question its potential application in the assessment of MCI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Dementia Rating Scale in Alzheimer's disease, Huntington's disease and progressive supranuclear palsy

The Dementia Rating Scale (DRS) comprises a series of five subtests which assess attention, memory, initiation/preservation, construction, and conceptualisation. It can be delivered in full in approximately 30 min, making it a useful test for the detection and estimation of the overall level of dementia. We analysed the pattern of subscale test scores in patients with cortical and subcortical dementias, who were matched for their overall level of dementia on this scale. Patients with dementia of Alzheimer's type were more impaired than patients with Huntington's disease (HD) and progressive supranuclear palsy (PSP) on the memory subtest, whereas patients with HD and PSP were more impaired on the initiation/perseveration subtest. This is evidence in favour of the concept of cortical and subcortical dementias as separate, although overlapping, entities. Qualitative differences in the pattern of cognitive impairment in these disorders can be detected with a brief cognitive status examination.     

The differentiation of semantic dementia and frontal lobe dementia (temporal and frontal variants of frontotemporal dementia) from early Alzheimer's disease: A comparative neuropsychological study.

The authors compared age-matched groups of patients with the frontal and temporal lobe variants of frontotemporal dementia (FTD; dementia of frontal type [DFT] and semantic dementia), early Alzheimer's disease (AD), and normal controls (n?=?9 per group) on a comprehensive neuropsychological battery. A distinct profile emerged for each group: Those with AD showed a severe deficit in episodic memory with more subtle, but significant, impairments in semantic memory and visuospatial skills; patients with semantic dementia showed the previously documented picture of isolated, but profound, semantic memory breakdown with anomia and surface dyslexia but were indistinguishable from the AD group on a test of story recall; and the DFT group were the least impaired and showed mild deficits in episodic memory and verbal fluency but normal semantic memory. The frontal and temporal presentations of FTD are clearly separable from each other and from early AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological effects of closed head injury in older adults: A comparison with Alzheimer's disease.

In this study, neuropsychological profiles of 14 older adult patients with mild or moderate closed head injury (CHI). 14 patients with probable Alzheimer's disease (AD), and 14 community residing elderly controls were compared. The groups were similar in demographic features, and the CHI and AD patients had comparable Mini-Mental State Examination scores. Tests of verbal learning and memory, letter and category fluency, and naming were administered. Relative to the CHI group, AD patients exhibited more devastated memory and did not show a normal facilitation on the category retrieval task. The patient groups exhibited similar levels of categorical clustering and naming accuracy for both high- and low-frequency words. These results suggest that neuropsychological markers of memory and semantic processing may be useful in differentiating the cognitive effects from AD versus early recovery from CHI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are explicit memory disorders of progressive supranuclear palsy related to damage to striatofrontal circuits? Comparison with Alzheimer's, Parkinson's, and Huntington's diseases

To test the hypothesis that memory disorders of subcortico-frontal dementia result mainly from inefficiency of retrieval processes of stored information, we compared verbal learning in 15 patients with progressive supranuclear palsy, prototypical of "subcortical dementia," in free (California Verbal Learning Test) and controlled (Grober and Buschke's Test) encoding situations, with that of 19 controls, matched for age and level of education. The progressive supranuclear palsy patients showed memory deficits characterized by impaired immediate memory span, disturbed learning and consistency of recall, and abnormal number of false alarms at recognition, which were dramatically alleviated by controlled encoding associated with cued recall, using the same semantic cues. This memory profile was markedly different from that of patients with senile dementia of the Alzheimer type (n = 15), characterized by more rapid forgetting and less improvement in the controlled situation. Instead, it was similar to the memory pattern of patients with Parkinson's (n = 15) and Huntington's (n = 15) diseases. These results show a similar profile of memory disturbance in disorders involving damage to the striatofrontal system and suggest that the cortical and hippocampal lesions of PSP patients are insufficiently severe to interfere with the specific memory profile characteristic of the disease.     

Differentiating the roles of the hippocampus complex and the neocortex in long-term memory storage: Evidence from the study of semantic dementia and Alzheimer's disease.

Several computational models suggest that the hippocampal complex plays a key role in the establishment of new memories, but over time the storage of such memories becomes independent of this region. In support of such models, the authors demonstrate that patients with semantic dementia, who have relative sparing of the hippocampal complex, show a pattern of preserved recent memories and impaired distant memories. In a group study that used the Autobiographical Memory Interview, amnesic patients with Alzheimer's disease showed the more typical temporally graded loss (poor recall of recent memories), whereas patients with semantic dementia showed the reverse pattern. In a single-case study, using the Galton-Crovitz test, a patient with semantic dementia was significantly better at producing autobiographical memories from the most recent 5 years. By contrast, controls provided similarly detailed memories across all time periods back to childhood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Misattribution errors in Alzheimer's disease: The illusory truth effect.

Patients with mild Alzheimer's disease (AD) and age-matched controls were compared on a series of tasks designed to measure errors of misattribution, the act of attributing a memory or idea to an incorrect source. Misattribution 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 misattribution 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 misattribution errors under conditions in which the illusory truth effect is thought to rely on relative familiarity (uncued condition), but more misattribution 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Longitudinal deficits to attention, executive, and working memory in subtypes of mild cognitive impairment.

Objective: Mild cognitive impairment (MCI) has emerged as a classification for a prodromal phase of cognitive decline that may precede the emergence of Alzheimer's disease (AD). Recent research suggests that attention, executive, and working memory deficits may appear much earlier in the progression of AD than traditionally conceptualized, and may be more consistently associated with the later development of AD than memory processing deficits. The present study longitudinally tracked attention, executive and working memory functions in subtypes of MCI. Method: In a longitudinal study, 52 amnestic MCI (a-MCI), 29 nonamnestic MCI (na-MCI), and 25 age- and education-matched controls undertook neuropsychological assessment of visual and verbal memory, attentional processing, executive functioning, working memory capacity, and semantic language at 10 month intervals. Results: Analysis by repeated measures ANOVA indicate that the a-MCI and na-MCI groups displayed a decline in simple sustained attention (ηp2 = .054) with a significant decline on a task of divided attention (ηp2 = .053) being evident in the a-MCI group. Stable deficits were found on other measures of attention, working memory and executive function in the a-MCI and na-MCI groups. The a-MCI group displayed stable impairments to visual and verbal memory. Conclusions: The results indicate that a-MCI and na-MCI display a stable pattern of deficits to attention, working memory, and executive function. The decline in simple sustained attention in a-MCI and n-MCI groups and to divided attention in a-MCI may be early indicators of possible transition to dementia from MCI. However, further research is required to determine this. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Parkinson's dementia and Alzheimer's dementia: an evoked potential comparison

Auditory endogenous event-related potentials (ERPs) and flash visual evoked potentials (VEPs) were recorded in 26 elderly patients with idiopathic Parkinson's disease (PD), 14 with dementia and 12 non-demented, 16 elderly patients with Alzheimer dementia (AD) and 15 cognitively intact controls. ERP P3 and flash-VEP N2, P2 and delta (P2-P1) latency measures were significantly increased in the demented PD group compared with controls. The ERP P3 latency was also significantly delayed in the AD group compared with controls, but the differences in the flash-VEP measures from controls were not significant. No significant differences were noted between the PD groups, except for a significantly shorter flash-VEP N1 latency in the demented PD group; this was also the only significant evoked potential difference between the AD and PD dementia groups, which were otherwise electrophysiologically similar.     

Verbal memory in drug-naive, newly diagnosed Parkinson's disease. The retrieval deficit hypothesis revisited.

Objective: The retrieval deficit hypothesis on memory impairment in patients with Parkinson's disease (PD) implies a selective impairment in recall of learned material with normal encoding, retention, and recognition. This hypothesis has been challenged by new data. We have therefore investigated verbal memory and learning in a large sample of newly diagnosed, drug na?ve, non-demented patients with PD. Method: From a sample of patients with PD from the Norwegian ParkWest study, 133 PD patients and 133 controls matched on sex, age, and education were included. The California Verbal Learning Test-2 (CVLT-2) was used to assess verbal memory. Results: Patients performed significantly worse than controls on free and cued recall as well as on recognition memory. Patients used the semantic clustering learning strategy significantly less extensively than the controls and the learning slope of the PD patients was significantly less steep. There was no difference in retention when controlling for encoding. Patients did not perform better on the recognition measure or on cued recall (d-prime), as compared to free recall. Executive functions explained a substantial part of the memory deficits. Conclusions: This study suggests that memory impairment in drug na?ve early PD to a large degree is a deficit of learning/ encoding and not of retention or retrieval. An implication is that the retrieval deficit hypothesis should be moderated in its general form. Executive deficits and less extensive use of the efficient semantic clustering learning strategy had a strong impact on learning and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disparate letter and semantic category fluency deficits in autopsy-confirmed frontotemporal dementia and Alzheimer's disease.

Patients with autopsy-confirmed frontotemporal dementia (FTD; n = 16) and Alzheimer's disease (AD; n = 32) were compared on first-letter and semantic category fluency tasks. Despite being matched on age, education, and dementia severity, FTD patients performed worse overall and showed similar impairment in letter and semantic category fluency, whereas AD patients showed greater impairment in semantic category than letter fluency. A measure of the disparity between letter and semantic category fluency (the semantic index) was effective in differentiating FTD from AD patients, and this disparity increased with increasing severity of dementia. These unique patterns of letter and semantic category fluency deficits may be indicative of differences in the relative contribution of frontal-lobe-mediated retrieval deficits and temporal-lobe-mediated semantic deficits in FTD and AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)