Distinct profiles of brain and cognitive changes in the very old with Alzheimer disease

OBJECTIVE

To determine whether age-standardized brain morphometric and cognitive profiles differ in young-old (aged 60-75 years) and very-old (aged 80-91 years) patients with Alzheimer disease (AD).

METHODS

Using a case-control retrospective design, we compared hippocampal volume and cortical gray matter thickness in areas known to be affected by AD in 105 patients with AD and 125 healthy control (HC) participants divided into young-old and very-old subgroups. Brain morphometric and cognitive scores of the AD groups were standardized to their respective age-appropriate HC subgroup and then compared.

RESULTS

Several cognitive domains (executive function, immediate memory, and attention/processing speed) were less abnormal in the very old with AD than in the young old with AD. Similarly, the very old with AD showed less severe cortical thinning than the young old with AD in the left posterior cingulate cortex, right lateral temporal cortex, and bilateral parietal cortex and in overall cortical thickness. This effect is partially explained by an age-related decrease in cortical thickness in these brain regions in the HC participants.

CONCLUSIONS

The typical pattern of AD-related cognitive and morphometric changes seen in the young old appear to be less salient in the very old. Thus, mild cases of AD in the very old may go undetected if one expects to see the prototypical pattern and severity of cognitive or brain changes that occur in the young old with AD. These results underscore the importance of interpreting neuropsychological test performance and morphometric brain measures in reference to the individual's age.

Global clinical dementia rating of 0.5 in MCI masks variability related to level of function

OBJECTIVE

To evaluate whether ratings on Clinical Dementia Rating (CDR) items related to instrumental activities of daily living (IADL) are associated with cognitive or brain morphometric characteristics of participants with mild cognitive impairment (MCI) and global CDR scores of 0.5.

METHODS

Baseline cognitive and morphometric data were analyzed for 283 individuals with MCI who were divided into 2 groups (impaired and intact) based on their scores on the 3 CDR categories assessing IADL. Rates of progression to Alzheimer disease (AD) over 2 years were also compared in the 2 groups.

RESULTS

The impaired IADL MCI group showed a more widespread pattern of gray matter loss involving frontal and parietal regions, worse episodic memory and executive functions, and a higher percentage of individuals progressing to AD than the relatively intact IADL MCI group.

CONCLUSIONS

The results demonstrate the importance of considering functional information captured by the CDR when evaluating individuals with MCI, even though it is not given equal weight in the assignment of the global CDR score. Worse impairment on IADL items was associated with greater involvement of brain regions beyond the mesial temporal lobe. The conventional practice of relying on the global CDR score as currently computed underutilizes valuable IADL information available in the scale, and may delay identification of an important subset of individuals with MCI who are at higher risk of clinical decline.

Symmetry and transitivity of conditional relations in monkeys (Cebus apella) and pigeons (Columba livia)

In Experiment 1 six monkeys were tested with discriminative relations that were backward relative to their training in a 0-second conditional ("symbolic") matching procedure. Although there was some indication of backward associations, the evidence was generally weak, and statistical evaluations did not reach conventional significance levels. Unlike children, who show backward associations to the point of symmetry, monkeys and pigeons display at best only weak and transient backward associations. In Experiment 2 associative transitivity was assessed across two sets of conditional matching tasks. All four monkeys tested demonstrated strong transitivity. In contrast, in Experiment 3 there was no evidence of transitivity in three pigeons tested under conditions closely comparable to those of Experiment 2. These results may identify some key features of interspecies differences and contribute to analyses of serial learning in animals.

Decreased white matter integrity in late-myelinating fiber pathways in Alzheimer's disease supports retrogenesis

The retrogenesis model of Alzheimer's disease (AD) posits that white matter (WM) degeneration follows a pattern that is the reverse of myelogenesis. Using diffusion tensor imaging (DTI) to test this model, we predicted greater loss of microstructural integrity in late-myelinating WM fiber pathways in AD patients than in healthy older adults, whereas differences in early-myelinating WM fiber pathways were not expected. We compared 16 AD patients and 14 demographically-matched healthy older adults with a whole-brain approach via tract-based spatial statistics (TBSS), and a region of interest (ROI) approach targeting early-myelinating (posterior limb of internal capsule, cerebral peduncles) and late-myelinating (inferior longitudinal fasciculus [ILF], superior longitudinal fasciculus [SLF]) fiber pathways. Permutation-based voxelwise analysis supported the retrogenesis model. There was significantly lower fractional anisotropy (FA) in AD patients compared to healthy older adults in late-myelinating but not early-myelinating pathways. These group differences appeared to be driven by loss of myelin integrity based on our finding of greater radial diffusion in AD than in healthy elderly. ROI analyses were generally in agreement with whole-brain findings, with significantly lower FA and increased radial diffusion in the ILF in the AD group. Consistent with the retrogenesis model, AD patients showed demonstrable changes in late-myelinating WM fiber pathways. Given greater change in the ILF than the SLF, wallerian degeneration secondary to cortical atrophy may also be a contributing mechanism. Knowledge of the pattern of WM microstructural changes in AD and its underlying mechanisms may contribute to earlier detection and intervention in at-risk groups.

Multi-modal imaging predicts memory performance in normal aging and cognitive decline

This study (n=161) related morphometric MR imaging, FDG-PET and APOE genotype to memory scores in normal controls (NC), mild cognitive impairment (MCI) and Alzheimer's disease (AD). Stepwise regression analyses focused on morphometric and metabolic characteristics of the episodic memory network: hippocampus, entorhinal, parahippocampal, retrosplenial, posterior cingulate, precuneus, inferior parietal, and lateral orbitofrontal cortices. In NC, hippocampal metabolism predicted learning; entorhinal metabolism predicted recognition; and hippocampal metabolism predicted recall. In MCI, thickness of the entorhinal and precuneus cortices predicted learning, while parahippocampal metabolism predicted recognition. In AD, posterior cingulate cortical thickness predicted learning, while APOE genotype predicted recognition. In the total sample, hippocampal volume and metabolism, cortical thickness of the precuneus, and inferior parietal metabolism predicted learning; hippocampal volume and metabolism, parahippocampal thickness and APOE genotype predicted recognition. Imaging methods appear complementary and differentially sensitive to memory in health and disease. Medial temporal and parietal metabolism and morphometry best explained memory variance. Medial temporal characteristics were related to learning, recall and recognition, while parietal structures only predicted learning.

Patients with MCI and N400 or P600 abnormalities are at very high risk for conversion to dementia

OBJECTIVE

We sought cognitive event-related potential (ERP) biomarkers of disease progression and subsequent conversion to dementia in mild cognitive impairment (MCI).

BACKGROUND

Two ERP components, the P600 and N400, are sensitive to abnormal episodic/declarative memory and semantic processing. When congruous category-exemplars are repeated, smaller P600s (relative to initial presentation) are normally elicited. Repetitions of semantically incongruous words yield smaller N400 amplitude. In mild Alzheimer disease (AD), abnormalities of both the N400 and P600 repetition effects are present, suggesting a widespread failure of synaptic plasticity.

METHODS

Patients with amnestic MCI (n = 32) were longitudinally studied annually with an ERP paradigm in which semantically congruous (50%) and incongruous target words are repeated 10 to 140 seconds after initial presentation. ERP data were analyzed to contrast MCI-to-AD converters (within 3 years) vs nonconverters, using split-plot analyses of variance.

RESULTS

A statistically significant P600 congruous word repetition effect was found only in the nonconverter group (F = 9.9, p = 0.005 vs MCI converters). This effect correlated with verbal memory measures. Repetition of incongruous words produced a significant N400 amplitude attenuation (across right-hemisphere sites) in nonconverters, but not in converters. Patients with MCI with abnormal/reduced N400 or P600 word repetition effects had an 87 to 88% likelihood of dementia within 3 years while those with normal/spared N400 and P600 repetition effects had only an 11 to 27% likelihood.

CONCLUSIONS

Abnormalities of the P600 or N400 in mild cognitive impairment are associated with an increased risk of subsequent conversion to Alzheimer disease (AD). These event-related potential components may offer useful biomarkers for the detection and staging of very early AD.

Cycad exposure and risk of dementia, MCI, and PDC in the Chamorro population of Guam

OBJECTIVE

To study cycad-derived products as possible risk factors for dementia, mild cognitive impairment (MCI), and parkinsonism-dementia complex (PDC) on Guam.

METHODS

Complete risk factor data from in-person interviews of 166 cases of Guam dementia, 50 cases of amnestic MCI, and 21 cases of PDC were compared with 1,581 controls in the base population regarding exposure to cycad-derived products from a traditional food (fadang), consumption of fruit bats, and use of cycad-derived topical medicine.

RESULTS

Adjusted odds ratios (ORs) and 95% CIs for picking, processing, and eating fadang in young adulthood ranged from 1.42 (1.05 to 1.91) to 2.87 (1.48 to 5.56) and were consistently elevated and significant across all three diagnostic outcomes. Associations independent of exposure in young adulthood were for picking (OR 0.78, 95% CI 0.64 to 0.96) and processing (OR 0.77, 95% CI 0.63 to 0.94) fadang in childhood with Guam dementia. Men showed stronger and more consistent relations across exposure groups in young adulthood compared with women. No associations were found for consumption of fruit bats or exposure to cycad used as a topical medicine for any of the outcomes. Estimated adjusted population attributable risks suggest that exposure to eating fadang in young adulthood incurred the highest attributable risk percent.

CONCLUSIONS

Environmental lifestyle and diet may contribute to the etiology of neurodegenerative diseases in the native population of Guam.

Rate of progression differs in frontotemporal dementia and Alzheimer disease

OBJECTIVE

To compare survival and rates of cognitive and functional decline in patients with autopsy-confirmed frontotemporal dementia (FTD) and Alzheimer disease (AD) in a large multicenter study.

BACKGROUND

Despite advances in the clinical characterization of FTD, little is known about its rate of progression. Characterizing survival and rate of decline in FTD is important because it can provide prognostic guidelines and benchmarks to use in the evaluation of disease-modifying drugs.

METHODS

Seventy patients with FTD and 70 patients with AD who were followed by seven Alzheimer disease research centers until confirmation of diagnosis at autopsy were matched for overall age, education, and Mini-Mental State Examination (MMSE) score at initial evaluation. Survival and rates of cognitive and functional decline were compared.

RESULTS

Patients with FTD had significantly shorter survival from initial evaluation to death than patients with AD (FTD = 4.2 years, AD = 6.0 years; log-rank test = 5.17, p < 0.05), and they declined significantly faster over one year on the MMSE (mean annual rate of change: -6.7 points for FTD vs -2.3 points for AD). A significantly greater proportion of patients with FTD were impaired in basic activities of daily living (ADLs) at initial evaluation, and lost the capacity for independent or minimally-assisted ADLs over the subsequent year.

CONCLUSIONS

The results are consistent with shorter survival and faster rates of cognitive and functional decline in patients with frontotemporal dementia (FTD) compared to those with Alzheimer disease (AD). This suggests that FTD follows a more malignant disease course than AD once dementia is clinically recognized.

In vivo evidence of cerebellar atrophy and cerebral white matter loss in Huntington disease

OBJECTIVE

To investigate the regional pattern of white matter and cerebellar changes, as well as subcortical and cortical changes, in Huntington disease (HD) using morphometric analyses of structural MRI.

METHODS

Fifteen individuals with HD and 22 controls were studied; groups were similar in age and education. Primary analyses defined six subcortical regions, the gray and white matter of primary cortical lobes and cerebellum, and abnormal signal in the cerebral white matter.

RESULTS

As expected, basal ganglia and cerebral cortical gray matter volumes were significantly smaller in HD. The HD group also demonstrated significant cerebral white matter loss and an increase in the amount of abnormal signal in the white matter; occipital white matter appeared more affected than other cerebral white matter regions. Cortical gray and white matter measures were significantly related to caudate volume. Cerebellar gray and white matter volumes were both smaller in HD.

CONCLUSIONS

The cerebellum and the integrity of cerebral white matter may play a more significant role in the symptomatology of HD than previously thought. Furthermore, changes in cortical gray and cerebral white matter were related to caudate atrophy, supporting a similar mechanism of degeneration.

Alzheimer disease without neocortical neurofibrillary tangles: "a second look"

OBJECTIVE

To compare the clinical and pathologic features of plaque only Alzheimer disease (POAD) with plaque and tangle Alzheimer disease (PTAD).

METHODS

An autopsy series of 16 patients with POAD and 32 subjects with PTAD on whom extensive antemortem neuropsychological testing was available. Plaques, tangles, and cerebral amyloid angiopathy were examined in the neocortex and hippocampus using thioflavin S staining. In addition, immunocytochemical analysis with AT8 for phosphorylated tau was performed. Midfrontal (MF) synaptic density, MF choline acetyltransferase (ChAT) activity, and apolipoprotein E genotyping were also assessed.

RESULTS

Initial neuropsychological test scores and rates of cognitive decline on the Mini-Mental State Examination and Blessed Information-Memory-Concentration were similar between the two groups. However, compared to PTAD, POAD patients tended to deteriorate more slowly on the Mattis Dementia Rating Scale. Furthermore, they were somewhat less impaired on all these measures at last examination. There was an older age at onset and death, and a trend toward a shorter disease duration, in POAD compared to PTAD patients. POAD subjects, by definition, had no neocortical neurofibrillary tangles (NFT) (Braak stages IV or less). In addition, they also had fewer hippocampal NFT, fewer neuritic plaques, and higher mean MF ChAT activity than PTAD subjects. On the other hand, the two groups did not differ significantly in brain weight or MF synaptic density. Although lacking overt tangle formation, the POAD group displayed abnormal phosphorylated tau immunoreactivity in neocortical pyramidal neurons.

CONCLUSIONS

Dementing syndromes virtually indistinguishable from each other can, and do, develop in the presence or absence of neocortical NFT. Patients without neocortical NFT are, on average, older at disease onset and death, and show a trend toward a shorter disease duration with somewhat slower deterioration. Although neocortical NFT per se are not obligatory for the development of clinical dementia, more subtle neocortical cytoskeletal tau pathology may contribute to cognitive decline in these subjects.

Normal aging and forgetting rates on the Wechsler Memory Scale-Revised

The deleterious effects of aging on various cognitive abilities are widely recognized, yet little is known regarding what constitutes "normal" memory test performance in individuals over the age of 74. In this study, forgetting rates for verbal and nonverbal material from the Wechsler Memory Scale-Revised (WMS-R) were examined in groups of older healthy individuals, age 50-70 and 75-95. Despite equivalent scores on measures of global cognitive status and attention/ concentration, the older group demonstrated significantly more rapid forgetting rates on the Visual Reproduction, Verbal Paired Associates, and Visual Paired Associates subtests of the WMS-R. Although patients with Alzheimer's disease also evidence very rapid forgetting on some subtests, the severity and pattern of losses appears useful in differentiating "abnormal" forgetting from that exhibited by normal elderly subjects. Preliminary normative data for normal elderly subjects on the WMS-R are presented, and the need for appropriate norms for elderly individuals is discussed.

Neuromotor abnormalities and risk for psychosis in Alzheimer's disease

BACKGROUND

Cross-sectional studies in Alzheimer's disease (AD) show a strong relationship between extrapyramidal motor signs and presence of psychosis, yet it remains unclear whether neuromotor abnormalities precede and therefore can predict development of psychosis in AD.

OBJECTIVE

To identify cognitive and motor risk factors for the development of psychosis in patients with AD.

METHODS

Baseline clinical motor ratings and instrumental measures of neuromuscular function were obtained from 54 nonpsychotic patients with AD who were evaluated annually for 2 years for the development of psychosis. Survival analyses were performed to identify incidence and risks associated with psychosis.

RESULTS

The incidence of new onset psychosis in our sample was 32.5% in 2 years. Patients with abnormal agonist muscle burst amplitudes during rapid alternating movements of the hand were more likely to develop psychosis than those without (OR = 4.31; p = 0.007). Women with AD also had a higher risk of developing psychosis within 2 years than men (OR = 1.33; p = 0.01).

CONCLUSIONS

Using simple noninvasive instrumental procedures for assessing neuromotor function, it may be possible to identify an individual's level of risk for developing psychosis during the course of AD.

Behavioural abnormalities contribute to functional decline in Huntington's disease

The independent and relative contributions of motor, cognitive, and behavioural deficits to functional decline in patients with Huntington's disease are examined. Twenty two patients with Huntington's disease were assessed with rating scales for motor dysfunction, cognitive measures of executive functions, and behavioural measures of apathy, executive dysfunction, and disinhibition. Their functional status was assessed with informant based and clinician based ratings of activities of daily living (ADL). A composite apathy/executive dysfunction behavioural index was strongly related to decline in ADL independently and after controlling for motor and cognitive deficits. These results suggest that behavioural dysfunction contributes to functional decline in patients with Huntington's disease and may impede their ability to utilise motor or cognitive skills that remain available in the early stages of the disease.

Alzheimer's disease can be accurately diagnosed in very mildly impaired individuals

BACKGROUND

The growing propensity to diagnose AD in individuals with very mild cognitive impairment increases the danger of false-positive diagnostic errors. Unfortunately, there is little systematically acquired information about the accuracy of the AD diagnosis in very mildly impaired patients.

OBJECTIVE

To determine the accuracy of the diagnosis of AD in very mildly impaired patients and to identify objective measures that effectively distinguish these patients from elderly normal controls (NC).

METHODS

Consecutive patients with Mini-Mental State Examination scores of > or = 24 who received a clinical diagnosis of AD were evaluated annually for at least 3 years. The initial diagnosis was verified or refuted by autopsy or by information obtained in subsequent evaluations. Initial neuropsychological test scores of verified AD patients were compared with those of NC subjects to identify effective diagnostic measures.

RESULTS

The diagnosis of AD was confirmed in 98 of 110 (89%) very mildly impaired patients (33/36 by autopsy, 65/74 by disease progression). The diagnosis was inaccurate in 12 patients (11%): Seven were subsequently diagnosed with other neurologic disorders, and five were ultimately found to be normal. Neuropsychological measures of delayed recall, verbal fluency, and global cognitive status (i.e., Mattis Dementia Rating Scale) provided excellent sensitivity (> or = 96%) and specificity (> or = 93%) for differentiating between very mildly impaired AD patients and NC subjects.

CONCLUSIONS

When comprehensive assessment procedures are employed, AD can be diagnosed with reasonably high accuracy in very mildly impaired individuals. However, the dementia evaluation should be repeated after approximately 1 year to ensure the accuracy of the initial diagnosis.

Abnormal verbal event related potentials in mild cognitive impairment and incipient Alzheimer's disease

BACKGROUND

It has been reported that patients with amnesia have a reduced effect of word repetition upon the late positive component of the event related potential (ERP), which peaks at around 600 ms after word onset.

OBJECTIVE

To study a word repetition ERP paradigm in subjects with mild cognitive impairment.

SUBJECTS

14 patients with mild cognitive impairment (mean mini-mental state examination score = 27); 14 normal elderly controls.

METHODS

Auditory category statements were each followed by a single visual target word (50% "congruous" category exemplars, 50% "incongruous") while ERPs were recorded. N400 (an ERP component elicited by semantically "incongruous" words) and LPC amplitude data were submitted to analysis of variance.

RESULTS

The latency of the N400 was slower in mild cognitive impairment. In normal controls, the ERPs to "congruous" targets showed a late positive component to new words, which was greatly diminished with repetition. This repetition effect in normal subjects started before 300 ms at right frontal sites, and peaked at approximately 600 ms post-stimulus over posterior sites. In contrast, the group with mild cognitive impairment had a reduced repetition effect (p < 0.02), which started around 500 ms, with a more central distribution. Further comparisons within the cognitive impairment group showed no appreciable congruous word repetition effect among seven individuals who subsequently converted to probable Alzheimer's disease. The congruous word repetition effect in the group with mild cognitive impairment was almost entirely accounted for by the non-converters. The amplitude of the congruous late positive component word repetition effect was significantly correlated (0.38 < or = r < or = 0.73) with several verbal memory measures.

CONCLUSIONS

The congruous word repetition ERP effect appears sensitive to the memory impairment in mild cognitive impairment and could have value in predicting incipient Alzheimer's disease.

Cognitive profiles differ in autopsy-confirmed frontotemporal dementia and AD

BACKGROUND

Frontotemporal dementia (FTD) is currently distinguished from AD primarily on the basis of behavioral features because studies of cognition have shown negligible or inconsistent differences. However, the poor discriminability of cognitive measures may relate to reliance on imprecise clinically diagnosed groups. Therefore, a retrospective examination of neuropsychological test performance in autopsy-confirmed patients is warranted.

OBJECTIVE

To compare the pattern of cognitive deficits exhibited by patients with autopsy-confirmed FTD and AD.

METHODS

The profiles of cognitive deficits exhibited by patients with neuropathologic diagnosis of FTD (n = 14) or AD (n = 28) were compared. The Mattis Dementia Rating Scale (MDRS), letter and category fluency tests, Wechsler Intelligence Scale for Children-Revised block design test, Boston naming test, and clock drawing test were administered.

RESULTS

Multivariate analysis of covariance controlling for age, education, and level of dementia revealed that patients with FTD performed significantly worse than patients with AD on letter and category fluency tests but significantly better on the MDRS memory subscale, block design test, and clock drawing test. A logistic regression model, validated in an independent clinical sample, used letter fluency, MDRS memory, and block design scores to correctly classify 91% of AD patients and 77% of FTD patients.

CONCLUSIONS

A double dissociation in the pattern of cognitive deficits exhibited by FTD and AD patients was demonstrated. The FTD patients were more impaired than AD patients on word generation tasks (i.e., verbal fluency) that are sensitive to frontal lobe dysfunction but less impaired on tests of memory and visuospatial abilities sensitive to dysfunction of medial temporal and parietal association cortices.

Clinical features and changing patterns of neurodegenerative disorders on Guam, 1997-2000

BACKGROUND

In the 1950s, high-incidence ALS and Parkinson-dementia complex (PDC) were identified among Chamorros, the native inhabitants of Guam. Brains of patients with these syndromes showed widespread neurofibrillary tangles. Although ALS and PDC were reported to have dramatically declined in the 1980s, new cases are still encountered. Late-life dementia has received little study among Chamorros.

METHODS

From 1997 to 2000, the authors evaluated newly referred and previously identified patients. They screened first-degree relatives of previous registries, and subjects aged 60 or older. Subjects who scored below a cognitive test cutoff or had symptoms or signs consistent with parkinsonism or ALS underwent psychometric testing, assessment by a neurologist, and laboratory studies as appropriate. Consensus diagnoses were made.

RESULTS

The authors identified 194 Chamorros with ALS (n = 10), PD (n = 11), PDC (n = 90), or late-life dementia (n = 83). Mean ages at onset were 55 for ALS, 68 for PDC, 63 for PD, and 74 for dementia. Late-life dementia was more common in women, and met criteria for probable or possible AD. The APOE-epsilon 4 allele frequency was uniformly low regardless of neurologic diagnosis.

CONCLUSIONS

The rapid decline of high-incidence ALS on Guam over the past 40 years suggests the contribution of a modifiable environmental factor. PDC remains relatively common, with an unchanged clinical picture apart from later age at onset. Dementia among elderly Chamorros (termed "Mariana dementia") resembles AD. Autopsy studies will clarify whether this dementia is related to AD pathology or represents a late-life neurofibrillary tangle syndrome more closely allied to PDC.

The effects of age, education, and gender on the Mattis Dementia Rating Scale performance of elderly Chinese and American individuals

A Chinese version of the Mattis Dementia Rating Scale (DRS) was administered to elderly individuals in Hong Kong (n = 104), and their performance on the test was compared with that of elderly participants in San Diego (n = 150). Age and education, but not gender, were significantly related to DRS performance in both groups. The effect of education was greater in the Hong Kong than in the San Diego participants, but this difference was eliminated when individuals with no formal education were removed from the Hong Kong group. Age- and education-matched groups of Hong Kong and San Diego elderly individuals differed in the pattern of DRS subtest performance they produced, even when they did not differ in total DRS score. The Hong Kong participants scored significantly higher than the San Diego participants on the Construction subscale, whereas the opposite pattern was observed on the Initiation/Perseveration and Memory subscales. These results suggest that some DRS subscales or individual subscale items may be susceptible to cultural differences between elderly Chinese and American individuals.

Cognitive screening and neuropsychological assessment in early Alzheimer's disease

Cognitive screening and detailed neuropsychological assessment provide a reliable means of detecting dementia in its earliest stages, tracking the progression of cognitive decline over time, and aiding in the differential diagnosis of various dementing disorders. In addition, recent studies have shown that mild cognitive changes, and particularly declines in memory function, are evident in the "preclinical" phase of Alzheimer's disease and may help to identify elderly individuals who are likely to develop dementia in the near future. Until effective and easily obtainable biological markers for detecting the onset and progression of Alzheimer's disease are developed, neuropsychological assessment will continue to have an important role in the dementia evaluation.

Abnormal semantic network for "animals" but not "tools" in patients with Alzheimer's disease

The effects of Alzheimer's disease (AD) on the organization of semantic knowledge (i.e., the semantic network) for living (e.g., animals) and non-living (e.g., tools) categories was examined. Multidimensional scaling and Pathfinder analyses of data from triadic comparison tasks showed that the semantic network for "animals", but not the network for "tools", was abnormal in patients with AD. Specifically, patients with AD tended to use a different primary dimension than control subjects for categorizing animals and their network was characterized by atypical associations between concepts. The differences in the integrity of the AD patients' networks for "animals" and "tools" was not likely to be an artifact of differences in the difficulty in identifying the stimuli in the two categories as all stimuli were identified on simple naming or matching tasks. These findings support the results of previous studies that have shown the presence of category-specific semantic deficits in patients with AD.

Neurobehaviors and psychotic symptoms in Alzheimer's disease

Psychotic symptoms are common in Alzheimer's disease (AD) and clinicoanatomical and neuropsychological evidence indicate an association between these symptoms and frontal lobe dysfunction. Neuro-behaviors associated with frontal dysfunction were assessed in Alzheimer's disease (AD) patients with (n = 20) and without psychotic symptoms (n = 21) matched for mean age, education, gender, and dementia severity. The Frontal Lobe Personality Scale (FLOPs) was completed by patient caregivers to measure behaviors typically associated with frontal dysfunction. Findings indicated that AD patients with psychotic symptoms exhibited significantly greater neurobehavioral dysfunction (FLOPs M = 130.69, SD = 24.70) than AD patients without psychotic symptoms (FLOPs M = 111.10, SD = 25.83). Subscale analyses indicated that psychotic AD patients were more dis-inhibited (M = 28.28, SD = 7.54) than patients without psychotic symptoms (M = 20.92, SD = 4.9). Findings are consistent with and contribute to previous neuropsychological and clinicoanatomical research suggesting increased frontal dysfunction in AD with psychotic symptoms and lend additional empirical support to subtyping AD based on the presence of psychotic symptoms. Furthermore, findings provide preliminary evidence indicating which specific type of neurobehavioral abnormalities are related to the presence of distressing psychotic symptoms.

Word repetition in amnesia. Electrophysiological measures of impaired and spared memory

Amnesic patients often show improved performance when stimuli are repeated, even in the absence of conscious memory for those stimuli. Although these performance changes are typically attributed to perceptual or motor systems, in some cases they may be related to basic language processing. We examined two neurophysiological measures that vary with word repetition in 12 amnesic patients and 12 control subjects: (i) a late positive component of the event-related potential (ERP) linked to conscious memory and (ii) the N400 component that varies with language comprehension. In each trial, the subject heard a category name, then viewed a word, and then decided whether the word was semantically congruous or incongruous (e.g. 'yes' for 'baby animal: cub'; 'no' for 'water sport: kitchen'). Recall and recognition testing at the end of the experiment showed that control subjects had better memory for congruous than for incongruous words, as did the amnesic patients, who performed less well overall. In contrast, amnesic patients were unimpaired on the category decisions required in each trial and, like the control subjects, showed a large N400 for incongruous relative to congruous words. Similarly, when incongruous trials were repeated after 0-13 intervening trials, N400s were reduced in both groups. When congruous trials were repeated, a late positive repetition effect was observed, but only in the control group. Furthermore, the amplitude of the late positive repetition effect was highly correlated with later word recall in both patients and controls. In the patients, the correlation was also observed with memory scores from standardized neuropsychological tests. These data are consistent with a proposed link between the late positive repetition effect and conscious memory. On the other hand, the N400 repetition effect was not correlated with episodic memory abilities, but instead indexed an aspect of memory that was intact in the amnesic patients. The preserved N400 repetition effect is an example of preserved memory in amnesia that does not easily fit into the categories of low-level perceptual processing or of motor learning. Instead, the sensitivity of the N400 to both semantic context and repetition may reflect a short-term memory process that serves language comprehension in realtime.

Measuring cognitive change in a cohort of patients with Alzheimer's disease

Annualized rates of cognitive change in Alzheimer's disease (AD), an important index of disease progression, show marked variability. To determine factors leading to such variability, we computed rates of change in a cohort of patients with AD tested annually with the Mini Mental State Examination (MMSE) and the more detailed Dementia Rating Scale (DRS). Estimates of rates of change (slopes) and intercepts were calculated using least squares and best linear unbiased predictors (BLUPs). Potential predictors of rates of change were examined using multivariate linear regression analysis. We found that the MMSE had more noise than the DRS. For the MMSE, slopes showed a moderate floor effect and a slight ceiling, depending on initial MMSE scores. These effects were less prominent for the DRS, for which slopes increased as intercepts decreased. In analyses of predictors of change, the MMSE was less useful than the DRS. In multiple linear regression models using DRS data, predictors showed statistically stronger effects and explained a greater extent of variation of slopes than did similar models using MMSE data. For example, among patients who died and underwent brain examination at autopsy, neuropathology of Lewy bodies plus AD (Lewy Body variant; LBV) was associated with significantly faster rates of cognitive decline compared to pure AD in analyses that used the DRS, but only trends were identified with the MMSE. The metric properties and longitudinal characteristics of cognitive tests and the statistical methods used to calculate change are key factors in obtaining reliable estimates of change in studying cohorts of patients with AD.

Incidence of and risk factors for hallucinations and delusions in patients with probable AD

OBJECTIVE

To examine the incidence of and risk factors for hallucinations and delusions associated with patients clinically diagnosed with probable AD.

BACKGROUND

Estimates of the incidence of psychosis in AD range widely from 10% to 75%. The risk factors for psychosis of AD are not known, although multiple studies indicate that AD patients with psychosis demonstrate greater cognitive and functional impairment.

METHODS

The authors conducted psychiatric evaluations of 329 patients with probable AD from the University of California at San Diego Alzheimer's Disease Research Center to determine the incidence of hallucinations and delusions. They examined data from annual clinical and neuropsychological evaluations to determine whether there were specific risk factors for the development of hallucinations and delusions.

RESULTS

Using Cox survival analyses, the cumulative incidence of hallucinations and delusions was 20.1% at 1 year, 36.1% at 2, 49.5% at 3, and 51.3% at 4 years. Parkinsonian gait, bradyphrenia, exaggerated general cognitive decline, and exaggerated semantic memory decline were significant predictors. Age, education, and gender were not significant predictors.

CONCLUSIONS

The authors found a relatively high incidence of hallucinations and delusions in patients diagnosed with probable AD and suggest that specific neurologic signs, cognitive abilities, and accelerated decline may be predictive markers for their occurrence.

Comparison of the serial position effect in very mild Alzheimer's disease, mild Alzheimer's disease, and amnesia associated with electroconvulsive therapy

Individuals given a series of words to memorize normally show better immediate recall for items from the beginning and end of the list than for mid-list items. This phenomenon, known as the serial position effect, is thought to reflect the concurrent contributions of secondary and primary memory, respectively, to recall performance. The present study compared the serial position effects produced on Trial 1 of the California Verbal Learning Test (CVLT) in mildly demented (N = 25; M MMSE = 20.0) and very mildly demented (N = 25; M MMSE = 25.5) patients with Alzheimer's disease (AD), and age- and education-matched normal control (NC) participants (N = 50). In addition, the serial position effects of the very mildly demented AD patients were compared to those of patients with a transient, circumscribed amnesia arising from a prescribed series of electroconvulsive therapy (ECT) treatments for the relief of depressive illness (N = 11). While the NC group exhibited the typical serial position effect, AD patients recalled significantly fewer words than NC participants overall, and exhibited a significantly reduced primacy effect (i.e., recall of the first 2 list items) with a normal recency effect (i.e., recall of the last 2 list items). Patients with circumscribed amnesia due to ECT were as impaired as the very mildly demented AD patients on most standard CVLT measures of learning and memory, but exhibited primacy and recency effects, which were within normal limits. These results suggest that a reduction in the primacy effect, but not the recency effect, is an early and ubiquitous feature of the memory impairment of AD. It is not, however, a necessary feature of all causes of memory impairment.

Differential decline in word generation from phonemic and semantic categories during the course of Alzheimer's disease: implications for the integrity of semantic memory

The ability to generate words from phonemic (i.e., words beginning with 'F,' 'A,' and 'S') and semantic (i.e., animals, fruits, and vegetables) categories was assessed longitudinally in patients with Alzheimer's disease (AD; N = 59) and normal controls (NC; N = 59). Patients with AD performed worse than NC participants on both tasks at each of 4 annual evaluations and exhibited greater impairment relative to controls on the semantic-category task than on the phonemic-category task. In addition, the performance of the patients with AD declined over time on both tasks, but the rate of decline was faster on the semantic-category than on the phonemic-category task. Examination of individual responses across the annual evaluations revealed that patients with AD were more consistent than NC participants in failing to generate previously produced semantic-category, but not phonemic-category, items in all years following the 1st year in which the item was not produced. These results are consistent with the notion that patients with AD suffer a gradual deterioration of the organization and content of semantic memory as the disease progresses.

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.

Neuropsychological function and apolipoprotein E genotype in the preclinical detection of Alzheimer's disease

Nondemented older adults genotyped for the Apolipoprotein E (ApoE) epsilon4 allele (n = 43) were neuropsychologically compared to participants without a copy of the epsilon4 allele (n = 90). At baseline, the groups did not differ on age, education, gender, or global cognitive status. ApoE-epsilon4 participants demonstrated significantly poorer mean performances on delayed recall, but no significant group differences emerged on attention, language, constructional skills, psychomotor speed, or executive function. Significantly more ApoE-epsilon4 participants developed probable or questionable Alzheimer's disease (AD) compared with non-epsilon4 participants, suggesting that the group differences resulted from a preponderance of preclinical AD cases within the epsilon4 group and not from a direct influence of ApoE genotype on cognition. Cox proportional hazards analysis, adjusting for age, years of education, and global cognitive status, revealed that ApoE-epsilon4 allele status and measures of recall performance were significant and independent predictors of conversion to AD. Results support the importance of specific episodic memory changes and possession of the ApoE-epsilon4 allele in the preclinical detection of AD.

A normative study of Nelson's (1976) modified version of the Wisconsin Card Sorting Test in healthy older adults

A modified version of the Wisconsin Card Sorting Test (mWCST) proposed by Nelson (1976) was administered to 229 healthy community-dwelling older adults, composed of 97 men and 132 women, ages 45 to 91. Investigating the impact of demographic factors such as age, education, and gender on mWCST performance, results indicated that mWCST performance was significantly affected by both age and education. Unlike the standard WCST, however, gender did not significantly influence mWCST performance. Because demographic factors appear to exert a significant influence on mWCST performance of normal older adults, demographically-corrected norms were calculated according to the procedure described by Heaton, Grant, and Matthews (1991). In addition, longitudinal analysis of mWCST performance revealed that significantly fewer nonperseverative errors were committed at retest approximately one year later. Number of categories completed and perseverative errors did not appear to demonstrate significant practice effects in this sample. Accounting for demographic influences and the inspection of practice effects on serial administration of the mWCST may improve upon its sensitivity and specificity for use in the clinical assessment of executive function in older adults.

Regional cerebral volume loss associated with verbal learning and memory in dementia of the Alzheimer type

Twenty-seven research participants with dementia of the Alzheimer type were studied with the California Verbal Learning Test (D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 1987) and standardized volume measures of the mesial temporal cortical gray matter, neocortical gray matter, thalamus, and caudate nuclei, from magnetic resonance imaging. A pattern of atrophic brain changes in the mesial temporal lobes (MTL) and the thalamus, with relatively less severe atrophy in the neocortical gray matter, was associated with poorer learning of the word list. Similar patterns of brain atrophy were observed for measures of delayed recall and recognition hits. However, for delayed recall, neither contribution was statistically significant, and for recognition hits, MTL was only at the trend level for significance. These results provide evidence that the verbal memory deficit of Alzheimer's disease (AD) is associated not only with the mesial temporal limbic cortex, thought to be the site of earliest and most severe pathology in AD, but also with damage in the thalamus.

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.

Conceptual and perceptual contributions to the acquisition and retention of text-specific reading skill in Alzheimer's disease

In the first experiment, patients with Alzheimer's disease (AD) and normal control (NC) participants read each of two passages three times and then again after either a 1-min or 10-min delay interval. Reading time decreased with practice for both groups, and this facilitation was text-specific. Although both groups retained the facilitation in reading speed after 1 min, it was reduced only in the AD group after 10 min. In the second experiment, the same task was repeated with new passages that encouraged the use of either conceptual or perceptual processing during reading. Patients with AD acquired the facilitation in reading speed normally in both conditions, but were impaired in retaining it over a 10-min delay interval only in the conceptually-weighted condition

Neuropsychological function and apolipoprotein E genotype in the preclinical detection of Alzheimer's disease

Nondemented older adults genotyped for the Apolipoprotein E (ApoE) epsilon4 allele (n = 43) were neuropsychologically compared to participants without a copy of the epsilon4 allele (n = 90). At baseline, the groups did not differ on age, education, gender, or global cognitive status. ApoE-epsilon4 participants demonstrated significantly poorer mean performances on delayed recall, but no significant group differences emerged on attention, language, constructional skills, psychomotor speed, or executive function. Significantly more ApoE-epsilon4 participants developed probable or questionable Alzheimer's disease (AD) compared with non-epsilon4 participants, suggesting that the group differences resulted from a preponderance of preclinical AD cases within the epsilon4 group and not from a direct influence of ApoE genotype on cognition. Cox proportional hazards analysis, adjusting for age, years of education, and global cognitive status, revealed that ApoE-epsilon4 allele status and measures of recall performance were significant and independent predictors of conversion to AD. Results support the importance of specific episodic memory changes and possession of the ApoE-epsilon4 allele in the preclinical detection of AD.

Mini-Mental State Examination and Mattis Dementia Rating Scale performance differs in Hispanic and non-Hispanic Alzheimer's disease patients

Little information exists regarding the performance of Spanish-speaking versus English-speaking patients with Alzheimer's disease (AD) on the Mini-Mental State Examination and the Mattis Dementia Rating Scale. In an attempt to identify culturally biased MMSE items or DRS subscales, we matched Spanish-speaking Hispanic and English-speaking non-Hispanic White community-dwelling AD patients by their MMSE scores and examined specific items within each scale. Our findings indicate that Hispanic AD patients perform significantly worse than non-Hispanics in terms of total DRS score, scores on the DRS subscales for Conceptualization and Memory, and on serial subtraction (or backward spelling item) of the MMSE. While mildly to moderately demented Hispanic and non-Hispanic patients obtained comparable scores on the DRS, severely impaired Spanish-speaking participants obtained considerably lower DRS scores than their English-speaking counterparts. The discrepancy in the DRS scores of the severely impaired Hispanic and non-Hispanic examinees might reflect a cultural bias in the test or educational differences between the groups. Alternatively, the DRS may be more sensitive than the MMSE for detecting severe cognitive impairment in Hispanic patients.

Regional cerebral volume loss associated with verbal learning and memory in dementia of the Alzheimer type

Twenty-seven research participants with dementia of the Alzheimer type were studied with the California Verbal Learning Test (D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 1987) and standardized volume measures of the mesial temporal cortical gray matter, neocortical gray matter, thalamus, and caudate nuclei, from magnetic resonance imaging. A pattern of atrophic brain changes in the mesial temporal lobes (MTL) and the thalamus, with relatively less severe atrophy in the neocortical gray matter, was associated with poorer learning of the word list. Similar patterns of brain atrophy were observed for measures of delayed recall and recognition hits. However, for delayed recall, neither contribution was statistically significant, and for recognition hits, MTL was only at the trend level for significance. These results provide evidence that the verbal memory deficit of Alzheimer's disease (AD) is associated not only with the mesial temporal limbic cortex, thought to be the site of earliest and most severe pathology in AD, but also with damage in the thalamus.

The deterioration of semantic memory in Alzheimer's disease

Semantic memory impairment is a common feature of dementia of the Alzheimer type (DAT). Recent research has shown that patients with DAT are more impaired (relative to non-demented controls) in generating exemplars from a particular semantic category (e.g., animals) than words beginning with a particular letter, exhibit an altered temporal dynamic during the production of category exemplars, are impaired on confrontation naming tasks and make predominantly superordinate or semantically related errors, consistently misidentify the same objects across a variety of semantic tasks, and have alterations in multi-dimensional scaling models of their semantic network that are indicative of a loss of concepts and associations. These results are consistent with the view that Alzheimer's disease results in a breakdown in the organization and structure of semantic knowledge as neurodegeneration spreads to the association cortices that presumably store semantic representations.

Very early changes in olfactory functioning due to Alzheimer's disease and the role of apolipoprotein E in olfaction

Alzheimer's disease (AD) is a progressive neurodegenerative illness marked by memory loss and at least one other cognitive disturbance. Early diagnosis of the disease has proved difficult and has therefore been the focus of much research. Apolipoprotein E (ApoE), a protein manufactured and distributed throughout the body, has shown specificity of binding to the beta A4 peptide, the primary component in the senile plaques of AD. Furthermore, the ApoE, epsilon 4 (epsilon 4) allele, is overrepresented in AD. These two lines of evidence suggest that ApoE, specifically the epsilon 4 allele, plays an important role in the development of AD. Further support for this hypothesis appears in neuropsychological data showing cognitive decrements in ostensibly nondemented individuals with the epsilon 4 allele, compared to those without the allele. It is also well known that olfaction is compromised in AD. Thus, the purpose of this study was twofold: (1) to examine very early changes in olfactory functioning due to AD and (2) to examine the role of ApoE in olfactory functioning in people at risk for AD by virtue of early cognitive decline. Results demonstrated changes in olfactory threshold the year immediately preceding change in diagnosis from normal control to AD. Also, in individuals with mild cognitive impairment, those with the ApoE epsilon 4 allele show poorer thresholds than those without the epsilon 4 allele.

Apolipoprotein E status is associated with odor identification deficits in nondemented older persons

Alzheimer's disease (AD) patients with moderate dementia show losses in olfactory threshold, odor identification and odor memory. Sensitivity and specificity of olfactory testing is significant, with the greatest power of accurate diagnosis in the more cognitively loaded olfactory tasks. In patients with very mild AD or in patients at risk for the disease because of their mild cognitive impairment, losses are apparent for odor identification, odor recognition memory and odor threshold, with the best sensitivity in the identification task. Persons who are either heterozygous or homozygous for the epsilon 4 allele of apolipoprotein E (ApoE) have an increased risk of Alzheimer's disease, although they show no dementia in the preclinical period. Evidence of olfactory dysfunction in this population might be reflective of an incipient dementing process. We have recently examined olfactory function in a group of normal elderly persons who have undergone genetic testing for the Apoe4 allele. These individuals consisted of all normal control subjects at the University of California, San Diego (UCSD) Alzheimer's Disease Research Center (ADRC) who had undergone both the genetic testing and testing for olfactory function. All had been diagnosed as normal control participants by two different neurologists who applied the National Institute of Neurological Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINDS-ADRDA) criteria for dementia. Persons with a history of alcoholism, drug abuse, learning disability or neurologic or psychiatric illness (including depression) were excluded. In this population, persons with the Apoe4 allele showed significantly poorer odor identification than those without an epsilon 4 allele. Early appearance of olfactory deficits in the progression to AD in persons with the epsilon 4 allele suggests diagnostic utility in olfactory testing.

Cognitive decline is faster in Lewy body variant than in Alzheimer's disease

OBJECTIVES

To quantify the rate of cognitive decline on the Mini-Mental State Examination (MMSE) in autopsy-diagnosed Lewy body variant (LBV) of Alzheimer's disease (AD) cases. We hypothesized that LBV patients would have a faster cognitive decline and shorter survival compared with patients with pure AD.

BACKGROUND

Prior reports have shown extrapyramidal signs to be associated with a poorer prognosis in AD. It has been suggested that LBV is often characterized by a rapidly progressive course. Few data are available regarding the rate of cognitive decline in autopsy-confirmed LBV dementia cases.

METHODS

We searched the databases of the University of California-San Diego Alzheimer's Disease Research Center and the Consortium to Establish a Registry in Alzheimer's Disease (CERAD) for dementia cases with 1) an autopsy diagnosis of definite or probable AD (CERAD criteria) with concomitant Lewy bodies and 2) longitudinal MMSE assessments. This resulted in a series of 40 LBV cases and 148 AD cases without Lewy bodies, with comparable baseline MMSE scores, age, and education. The rate of cognitive decline was calculated as the baseline MMSE -- final MMSE. Methods were devised to reduce floor effects on the MMSE.

RESULTS

The average rate of cognitive decline was -5.8 +/- 4.5 points/y in LBV and -4.1 +/- 3.0 points/y in AD (t-test, p < 0.01). The LBV group declined a similar amount on the MMSE (means, -10.0 versus -9.6 points) over a significantly shorter time interval (1.9 versus 2.7 years; p = 0.005) than did AD patients. At baseline, the mean MMSE scores were nearly identical (18.2 in LBV; 17.8 in AD), but on follow-up examinations approximately 1, 2, and 3 years later, there were intergroup mean differences of 1.8 points (two-tailed p = 0.19), 4.2 points (p = 0.04), and 5.6 points (p = 0.03), respectively. The LBV cases had shorter survival time from the onset of cognitive symptoms (7.7 +/- 3.0 years versus 9.3 +/- 3.5 years; p = 0.007) and a shorter mean survival after entry/baseline, which was of marginal significance (3.6 versus 4.1 years; p = 0.11).

CONCLUSIONS

This study demonstrates that LBV is characterized by a faster cognitive decline and accelerated mortality compared with AD.

Cognitive profiles of autopsy-confirmed Lewy body variant vs pure Alzheimer disease

OBJECTIVE

To compare the cognitive profiles of patients with autopsy-confirmed Alzheimer disease (AD), with or without concomitant Lewy bodies, on 2 dementia screening measures.

METHODS

Profiles on subtests of the Mattis Dementia Rating Scale (range, 105-125) and of component items of the Mini-Mental State Examination were compared between 23 patients with uncomplicated AD and 23 patients with concomitant AD and Lewy body pathology (Lewy body variant [LBV]).

RESULTS

Although the groups did not differ significantly regarding age, years of education, total Mini-Mental State Examination score, or total Mattis Dementia Rating Scale score, the AD group performed significantly worse than the LBV group on the Mattis Dementia Rating Scale Memory subscale (P < .005). In contrast, the LBV group demonstrated poorer performance than the pure AD group on the Initiation/Perseveration subscale (P < .02). The groups did not differ significantly on the Attention, Construction, or Conceptualization subscales. The same overall pattern of results was obtained when subgroups with mild to moderate and moderate to severe dementia were examined separately, with the additional finding that in the mild-to-moderate range patients with dementia and LBV performed worse than patients with pure AD on the Construction subscale.

CONCLUSIONS

The difference in pattern of cognitive deficits among patients with pure AD vs those with AD and LBV is similar to that seen between AD and more subcortical/frontal dementias (eg, Huntington disease) This suggests that the concomitant Lewy body pathology significantly contributes to the presentation of the cognitive dysfunction in individuals with LBV.

Cortical and subcortical influences on clustering and switching in the performance of verbal fluency tasks

Impairments on lexical and semantic fluency tasks occur in both cortical and subcortical dementia. Recent reports that the average size of phonemic and semantic clusters is reduced in Alzheimer's disease (AD), but not in Parkinson's disease (PD) could support the hypothesis that in AD verbal fluency deficits arise from degraded memory storage while in PD the same impairments result from defective retrieval. In the present study, patients with AD, PD with dementia, or Huntington's disease produced fewer words, fewer switching responses and smaller semantic cluster sizes. Patients with multiple sclerosis, regardless of whether or not they were demented, produced fewer words and switching responses, but normal size clusters, and patients with PD without dementia performed normally on all fluency measures. These results indicate that reductions in cluster size on verbal fluency tests are best interpreted as changes in the efficiency of access to lexical and semantic memory stores. The findings are also consistent with the idea that patterns of cognitive impairment may differ among diseases that result in subcortical dementia.

Repetition priming with nonverbal stimuli in patients with dementia of the Alzheimer type

Perceptual repetition priming was examined in patients with dementia of the Alzheimer type (DAT) and normal control (NC) participants using a task involving the discrimination of geometric designs that had either a continuous ("closed") or discontinuous ("open") perimeter. With the open stimuli, the groups displayed significant and equivalent levels of priming after immediate repetition of the stimuli, whereas only the NC group primed significantly over a delay of three intervening items. Neither group demonstrated significant priming with the closed stimuli. Results indicate that under some conditions DAT patients can exhibit normal repetition priming with stimuli that do not have preexisting representations but that (due possibly to a deficiency in the level of steady-state cortical activation) this priming dissipates more rapidly in DAT patients than in NC participants.

Repetition priming with nonverbal stimuli in patients with dementia of the Alzheimer type

Perceptual repetition priming was examined in patients with dementia of the Alzheimer type (DAT) and normal control (NC) participants using a task involving the discrimination of geometric designs that had either a continuous ("closed") or discontinuous ("open") perimeter. With the open stimuli, the groups displayed significant and equivalent levels of priming after immediate repetition of the stimuli, whereas only the NC group primed significantly over a delay of three intervening items. Neither group demonstrated significant priming with the closed stimuli. Results indicate that under some conditions DAT patients can exhibit normal repetition priming with stimuli that do not have preexisting representations but that (due possibly to a deficiency in the level of steady-state cortical activation) this priming dissipates more rapidly in DAT patients than in NC participants.

Deterioration of generic knowledge in patients with Alzheimer's disease: evidence from the Number Information Test

Semantic memory for generic knowledge was assessed in patients with probable Alzheimer's disease (AD; n = 142) and elderly normal control (NC; n = 78) subjects using the Number Information Test (NIT), a test that consists of 24 general knowledge questions that require a single number for an answer (e.g., "How many days are in a year?"). The results showed that patients with AD were impaired, even in the mildest stage of dementia, and that this impairment grew as the severity of their dementia increased over time. In addition, patients with AD were highly consistent in the individual items they missed in subsequent test sessions conducted 1 or 2 years later. These results indicate that semantic memory for generic knowledge is impaired relatively early in AD, deteriorates throughout the course of the disease, and may be due to a loss of knowledge rather than to a retrieval deficit.

Non-associative lexical priming is impaired in Alzheimer's disease

A word-fragment completion task was used to assess long-term, non-associative lexical priming in patients with probable Alzheimer's disease (AD) and age- and education-matched elderly normal control (NC) subjects. Despite equivalent baseline performance, the AD patients exhibited less facilitation in their ability to complete word fragments from having previously read the intact words than did the NC subjects. The AD patients were also impaired relative to NC subjects on an explicit recognition memory task, but there was no relationship between explicit memory performance and priming for either group. These results are consistent with previous demonstrations of impaired semantically-based priming in patients with AD and extend the domain of their impairment to priming that is predominantly based on lexical activation.