Dementia Of Alzheimer Type Subjects Research Articles

Machine‐learning‐based Alzheimer's disease dementia score using structural MRI neurodegeneration patterns: Independent validation on ADNI, AIBL, OASIS and MIRIAD

AbstractBackgroundBiomarkers for dementia of Alzheimer's type (DAT) are sought to facilitate accurate prediction of the disease onset, ideally predating the onset of cognitive deterioration. T1‐weighted magnetic resonance imaging (MRI) is a commonly used neuroimaging modality for measuring brain structure in‐vivo, potentially providing information enabling the design of biomarkers for DAT.MethodWe propose a novel biomarker using structural MRI volume‐based features to compute a similarity score for the individual's structural patterns relative to those observed in the DAT group. We employed ensemble learning framework that combines structural features in most discriminative ROIs to create an aggregate measure of neurodegeneration in the brain. This classifier is trained on 423 stable normal control (NC) and 330 DAT subjects, where clinical diagnosis is likely to have the highest certainty, and then validated on several independent datasets for subjects at various stages along the longitudinal trajectory from NC to DAT.ResultIndependent validation on 8834 un‐seen images from ADNI, AIBL, OASIS, MIRIAD Alzheimer's disease (AD) databases showed promising potential to predict the development of DAT depending on the time‐to‐conversion (TTC). Classification performance on stable versus progressive mild cognitive impairment (MCI) groups achieved an AUC of 0.81 for TTC of 6 months, and 0.73 for TTC of up to 7 years, achieving the state‐of‐the‐art results.ConclusionWe propose and validate a novel ensemble‐learning based biomarker score based on 3D topographic patterns of MRI‐observed structural volumetric features. The output score, indicating similarity to patterns seen in DAT, provides an intuitive measure of how closely the individual's brain features resemble the DAT group. This score can be used for assessing the presence of AD structural atrophy patterns in normal aging and MCI stages, as well as monitoring the progression of the individual's brain along the disease course.

Using machine learning to quantify structural MRI neurodegeneration patterns of Alzheimer's disease into dementia score: Independent validation on 8,834 images from ADNI, AIBL, OASIS, and MIRIAD databases.

Biomarkers for dementia of Alzheimer's type (DAT) are sought to facilitate accurate prediction of the disease onset, ideally predating the onset of cognitive deterioration. T1‐weighted magnetic resonance imaging (MRI) is a commonly used neuroimaging modality for measuring brain structure in vivo, potentially providing information enabling the design of biomarkers for DAT. We propose a novel biomarker using structural MRI volume‐based features to compute a similarity score for the individual's structural patterns relative to those observed in the DAT group. We employed ensemble‐learning framework that combines structural features in most discriminative ROIs to create an aggregate measure of neurodegeneration in the brain. This classifier is trained on 423 stable normal control (NC) and 330 DAT subjects, where clinical diagnosis is likely to have the highest certainty. Independent validation on 8,834 unseen images from ADNI, AIBL, OASIS, and MIRIAD Alzheimer's disease (AD) databases showed promising potential to predict the development of DAT depending on the time‐to‐conversion (TTC). Classification performance on stable versus progressive mild cognitive impairment (MCI) groups achieved an AUC of 0.81 for TTC of 6 months and 0.73 for TTC of up to 7 years, achieving state‐of‐the‐art results. The output score, indicating similarity to patterns seen in DAT, provides an intuitive measure of how closely the individual's brain features resemble the DAT group. This score can be used for assessing the presence of AD structural atrophy patterns in normal aging and MCI stages, as well as monitoring the progression of the individual's brain along with the disease course.

Uncinate fasciculus disruption relates to poor recognition of negative facial emotions in Alzheimer's disease: a cross-sectional diffusion tensor imaging study.

Recognising facial emotions involves visual and emotional information processing. Patients with dementia, including dementia of Alzheimer's type (DAT), are known to poorly recognise facial emotions, especially negative facial emotions. In this study, we aimed to assess if DAT patients exhibit poor facial emotional recognition, and to identify a neural basis for how poor facial emotional recognition might occur. Magnetic resonance imaging and diffusion tensor imaging (DTI) analysis were conducted in 20 DAT patients and 15 cognitive normal (CN) subjects. The uncinate fasciculus (UF), inferior longitudinal fasciculus, and inferior fronto-occipital fasciculus were delineated by deterministic tractography. DTI parameters were calculated for each fibre. Facial emotion recognition was evaluated with the Facial Emotion Selection Test (FEST). The relationships between FEST scores and DTI parameters in each fibre were measured by partial correlation analyses with age, gender, and the Mini-Mental State Examination as covariates. Group-wise comparisons between DAT and CN subjects were performed for each DTI parameter in each fibre. DAT patients showed lower FEST negative emotion scores than CN subjects (P < 0.05). The score of negative emotion subscale was negatively correlated (r = -0.770, P < 0.001) to mean diffusivity of the left UF in DAT patients. There were no relationships between negative emotion subscale and the other fibre tracts. DAT patients showed no differences in the DTI parameters for each fibre compared to CN subjects. DAT-related prefrontal-limbic network dysfunction is associated with poor recognition of unpleasant emotions; consequently, worse facial recognition of negative emotion is observed in DAT patients.

Relevance of the serial position effect in the differential diagnosis of mild cognitive impairment, Alzheimer-type dementia, and normal ageing

Serial position effects are observed when a person memorises a series of words exceeding his or her attention span. Cognitively normal individuals recall words at the beginning and end of the list more frequently than those in the middle, which reflects the way that short- and long-term episodic memory works. ObjectiveTo study the serial position effect in patients with mild cognitive impairment (MCI) compared to subjects with Alzheimer-type dementia (AD) or normal ageing (NA). Methods30 AD, 25 MCI and 20 NA subjects underwent neurological and neuropsychological assessment. The Rey Auditory Verbal Learning Test (RAVLT) was used to study primacy, middle, and recency effects and delayed recall for each group. ResultsThe general memory pattern of MCI subjects was very similar to that of AD subjects, and was characterised by reduced learning capacity, rapid forgetfulness and clear recency effect in learning. With regard to delayed recall, however, there were differences in performance; MCI subjects’ ability to recall words at the beginning and middle of the list was similar to that of normal subjects, while their memory of words at the end of the list was poor, as in AD subjects. ConclusionsRAVLT is a tool permitting us to distinguish between MCI and NA subjects. The recency index for the delayed recall task is a valid indicator for distinguishing between MCI patients and patients with normal ageing.

Relevancia del efecto de posición serial en el diagnóstico diferencial entre el deterioro cognitivo leve, la demencia de tipo Alzheimer y el envejecimiento normal

Serial position effects are observed when a person memorises a series of words exceeding his or her attention span. Cognitively normal individuals recall words at the beginning and end of the list more frequently than those in the middle, which reflects the way that short- and long-term episodic memory works. ObjectiveTo study the serial position effect in patients with mild cognitive impairment (MCI) compared to subjects with Alzheimer-type dementia (AD) or normal ageing (NA). Methods30 AD, 25 MCI and 20 NA subjects underwent neurological and neuropsychological assessment. The Rey Auditory Verbal Learning Test (RAVLT) was used to study primacy, middle, and recency effects and delayed recall for each group. ResultsThe general memory pattern of MCI subjects was very similar to that of AD subjects, and was characterised by reduced learning capacity, rapid forgetfulness and clear recency effect in learning. With regard to delayed recall, however, there were differences in performance; MCI subjects’ ability to recall words at the beginning and middle of the list was similar to that of normal subjects, while their memory of words at the end of the list was poor, as in AD subjects. ConclusionsRAVLT is a tool permitting us to distinguish between MCI and NA subjects. The recency index for the delayed recall task is a valid indicator for distinguishing between MCI patients and patients with normal ageing.

Autobiographical memory in mild cognitive impairment and Alzheimer's disease: A comparison between the Levine and Kopelman interview methodologies

Previous studies have produced inconsistent results concerning the two components of autobiographical memory--personal semantic memory and episodic memory. Results in subjects with mild cognitive impairment (MCI) and dementia of Alzheimer's type (DAT) have varied concerning the existence of a temporal gradient in retrograde amnesia. These results have important theoretical implications regarding multiple trace theory versus standard consolidation models of long-term memory (LTM). We investigated whether this variability arises from differences in the methods used in assessing autobiographical memory. We examined patterns of memory impairment in 20 healthy elderly controls, 20 MCI subjects, and 10 DAT subjects using the Autobiographical Memory Interview (AMI) of Kopelman and the Autobiographical Interview (AI) of Levine. Both the AMI and AI were modified to allow for the test scores to be derived from a single interview without fatiguing the subjects. On the AMI, DAT subjects were significantly impaired on both components of autobiographical memory--episodic memory and personal semantics--with episodic memory showing a significant though gentle temporal gradient sparing childhood memories. Using the AI test, subjects with DAT showed impaired recall of episodic details (but not personal semantics), again with a gentle temporal gradient. Differences between the two interview methods (fewer epochs in the AMI; fewer memories per epoch in the AI) were found to have a significant impact on the pattern of findings; fewer epochs in the AMI brought out the temporal gradient, and fewer memories per epoch (in the AI) diminished it. These data show the importance of technical details of the different tests in favouring one versus another LTM theory. The data are not purely compatible with either theory.

Evoked and event related coherence of Alzheimer patients manifest differentiation of sensory–cognitive networks

In previous studies on Alzheimer's patients it was shown that, in frontal and parietal locations, delta and theta responses of AD patients were greatly reduced. The present study analyzed coherence functions in these highly affected frontal and parietal areas. Visual sensory and event related coherences of patients with Alzheimer type dementia (AD) were analyzed comparatively. A total of 38 mild, probable AD subjects (19 untreated, 19 treated with cholinesterase inhibitors) were compared with a group of 19 healthy controls. The sensory evoked coherence and event related target coherences were analyzed for delta (1–3.5 Hz), theta (4–7 Hz), alpha (8–13 Hz), beta (15–30 Hz) and gamma (28–48 Hz) frequency ranges for long-range intra-hemispheric (F 3–P 3, F 4–P 4, F 3–T 5, F 4–T 6, F 3–O 1, F 4–O 2) electrode pairs. The healthy control group showed significantly higher values of event related coherence in “ delta”, “ theta” and “ alpha” bands in comparison to the de novo and medicated AD groups (p < 0.01 for the delta, theta and alpha) upon application of a target stimuli. In contrast, almost no changes in event related coherences were observed in beta and gamma frequency bands. Furthermore, no differences were recorded between healthy and AD groups upon application of simple light stimuli. Besides this, coherence values upon application of target stimuli were higher than sensory evoked coherence in all groups and in all frequency bands (p < 0.01). The cognitive networks of AD patients were highly impaired in comparison to networks activated by sensory stimulation, thus showing separate activation of sensory and cognitive networks.

Increased frontal phase-locking of event-related theta oscillations in Alzheimer patients treated with cholinesterase inhibitors

This is a pilot study describing event-related oscillations in patients with Alzheimer-type dementia (AD). Theta responses of 22 mild probable AD subjects according to NINCDS-ADRDA criteria (11 non-treated, 11 treated by cholinesterase inhibitors), and 20 healthy elderly controls were analyzed by using the conventional visual oddball paradigm. We aimed to compare theta responses of the three groups in a range between 4–7 Hz at the frontal electrodes. At F 3 location, theta responses of healthy subjects were phase locked to stimulation and theta oscillatory responses of non-treated Alzheimer patients showed weaker phase-locking, i.e. average of Z-transformed means of correlation coefficients between single trials was closer to zero. In treated AD patients, phase-locking following target stimulation was two times higher in comparison to the responses of non-treated patients. The results indicate that the phase-locking of theta oscillations at F 3 in the treated patients is as strong as the control subjects. The F 4 theta responses were not statistically significant between the groups. Our findings imply that the theta responses at F 3 location are highly unstable in comparison to F 4 in non-treated mild AD patients and cholinergic agents may modulate event-related theta oscillatory activities in the frontal regions.

Association of depression with Alzheimer's disease and vascular dementia in an elderly Arab population of Wadi‐Ara, Israel

Because dementia and depression share common risk factors, we investigated risk factors for depression in Arab subjects with Alzheimer's disease (AD) and vascular dementia (VaD). In a cross-sectional population-based study, we conducted a door-to-door survey of all adults over age 60 in an Arab community of rural Israel. We conducted interviews, gave questionnaires, and collected DNA blood specimens for determination of ApoE genotype. Of the 823 individuals in this naturalistic sample, 168 had dementia of Alzheimer's type (DAT) and 49 had VaD. Vascular risk factors, including the ApoE-epsilon4 allele, were more prevalent among VaD than DAT subjects. Depressive symptoms were present in 57% of DAT patients and 86% of VaD patients. Depressed DAT individuals had a greater history of ischemic cardiovascular or cerebrovascular (CV/CBV) disease than non-depressed DAT subjects, but depressed DAT subjects were less likely to have the ApoE-epsilon4 allele. Within the VaD group, there was no difference in the distribution of cardiovascular risk factors in individuals with and without depressive symptoms, and ApoE-epsilon4 was more prevalent among subjects with depressive symptoms. Depressive symptomatology is prevalent among subjects with dementias in this Arab community. History of CV/CBV is associated with the presence of depressive symptoms in DAT. Further studies are needed to clarify the role of ApoE in depression onset in different ethnic groups with DAT.

Quantitative evaluation of the burden of those giving home care for senile dementia of Alzheimer type subjects using the burnout scale of pines

We quantitatively measured the physical and psychological burden of caregivers of 25 patients with senile dementia of Alzheimer type (SDAT). The Barthel Index (BADL, full score: 20 points) and the caregiver burden in terms of physical symptoms correlated well (r = -0.964, p < 0.001), as did the degree of abnormal behavior and caregiver burden in terms of psychological symptoms (r = 0.946, p < 0.001). The correlation with the burnout scale (BOS) of Pines was best when both factors of psychological and physical symptoms were included. The correlation between BOS and the caregiver burden in terms of both physical and psychological symptoms was r = 0.874, p < 0.001, and the correlation between BOS and "the degree of abnormal behavior" +(20- "BADL") was r = 0.853, p < 0.001. The burden in terms of physical symptoms increased as the BADL score decreased, but the burden in terms of psychological symptoms increased initially and decreased in the last phase of the disease. We conclude that the BOS score of SDAT caregivers was stable in the initial phase, then increased rapidly, thereafter preserved high, and dropped rapidly as the BADL score decreased.

Low plasma epinephrine in elderly female subjects of dementia of Alzheimer type

One of the robust features of brain pathologies of dementia of Alzheimer type (DAT) is the impairment of the hippocampus, especially the cholinergic system. Several animal studies have suggested that the cholinergic system in the hippocampus is involved in the control of the plasma level of catecholamines and glucose. The stimulation of the hippocampal cholinergic system has resulted in the elevation of plasma catecholamines and glucose in rats. In the present study, we measured the plasma level of epinephrine, norepinephrine, dopamine, glucose, and insulin during a fasting state in the morning in hospitalized DAT (n=66), vascular dementia (VD) (n=28), or non-demented (ND) (n=21) females (mean age DAT=82. 49+/-4.98, VD=82.86+/-5.86, ND=82.95+/-7.77, respectively). Statistical analysis showed that the plasma level of epinephrine during a fasting state in DAT subjects was significantly lower than that of ND subjects; however, in VD subjects the level of epinephrine was not different from that of ND subjects. Other values did not differ significantly among the groups.

Dissociation between I 2-imidazoline receptors and MAO-B activity in platelets of patients with Alzheimers type dementia

The I 2-imidazoline receptor is expressed in brain and platelets and could represent a new binding domain on MAO-B enzyme. Brain I 2-imidazoline receptors and MAO-B sites have been found to be increased in Alzheimer's disease. The study sought to evaluate I 2-imidazoline receptors and MAO-B activity in platelets from patients with Alzheimer's type dementia (ATD) and matched controls. Preliminary saturation experiments of [ 3H]idazoxan binding to platelet purified mitochondrial membranes were performed to determine the maximal number of binding sites (B max) and the apparent dissociation constant (K d). Afterwards, the I 2-imidazoline receptor density ([ 3]idazoxan at 8 and 20 nM in the presence of 210 -6M efaroxan) was evaluated in 20 patients with ATD and 17 controls. MAO-B activity was quantified by [14 C]PEA oxidation. All subjects were screened for cognitive evaluation by the Mini-Mental State Examination. The density of I 2-imidazoline receptors was similar in ATD patients (8.4 and 14.3 fmol/mg protein) and controls (8.3 and 14.0 fmol/mg protein). MAO-B activity was 22% higher in ATD subjects. Significant correlations between I 2-imidazoline receptors and MAO-B activity were observed. No relationships between I 2-imidazoline receptors or MAO-B activity and the cognitive score were observed. In conclusion, platelet I 2-imidazoline receptors do not show the increase of I 2-imidazoline receptors previously observed in brain of subjects with ATD. The dissociation between I 2-imidazoline receptors and MAO-B in platelets suggests that the enzyme contributes to but not exclusively represents the I 2-imidazoline receptor.

Ventricular dilatation and brain atrophy of normal elderly individuals and patients with Alzheimer‐type dementia: A retrospective longitudinal computed tomographic study of autopsy cases

A retrospective longitudinal study of autopsy cases was performed in order to investigate the time course of ventricular dilatation and brain atrophy in normal individuals and patients with Alzheimer‐type dementia (ATD) subjects over 70 years of age. The brains of eight non‐demented individuals with no neurological or psychiatric illness (normal subjects, aged between 73 and 91 years), and the brains of seven ATD subjects (aged 68–96 years) were studied. The clinical records, including computed tomographic (CT) films, and autopsy findings were examined to eliminate subjects with conditions other than ATD. The rate of ventricular dilatation and brain atrophy was determined by volumetric measurement using serial CT films. Alzheimer‐type dementia was diagnosed on the basis of clinical findings, the presence of laminar cortical degeneration of the medial temporal cortex, and the density of senile plaques and neurofibrillary tangles. Ventricular dilatation was not detected in the normal subjects but was detected in the ATD patients during the follow‐up period. Brain atrophy was detected in both groups of subjects. However, the mean rate of brain atrophy of the ATD subjects was four times greater than that in the normal subjects. In addition, brain atrophy was accompanied by ventricular dilatation in all of the ATD patients, but was not evident in six of the eight normal subjects. Thus, the rate of ventricular dilatation was correlated with that of brain atrophy in the ATD patients, but not in the normal subjects. These results show that after 70 years of age: (i) the ventricular dilatation in normal subjects probably does not progress; (ii) brain atrophy in most normal subjects may continue; and (iii) rapidly progressive brain atrophy with ventricular dilatation is probably a common characteristic of ATD patients.

Ideational and semantic contributions to narrative production in adults with dementia of the Alzheimer's type

The narrative production of adults with probable dementia of Alzheimer's type (DAT) was investigated to determine the extent to which cognitive or linguistic deficits might explain the breakdown of discourse production. The structure of narrative tasks was manipulated so that the relationships among task structure and language production corresponded to predictions about the suspected origin of deficit. Sixteen DAT and 16 normal control subjects were administered four narrative tasks that were controlled for the amount of content and picture format display. The DAT subjects exhibited reduced content in terms of propositions and lexical items, shorter sentence lengths with more sentence fragments and reference errors. The mode of picture display failed to influence the amount of target content, or the grammatical performance of subjects. However, when compared to the normal controls, the amount of information pictorially represented significantly influenced the content provided by the DAT subjects; they performed better when the message to be related contained relatively less information. These findings support the contributions of both semantic-lexical and ideational systems to narrative discourse production.

White Matter Hyperintensities in Dementia of Alzheimer's Type and in Healthy Subjects Without Cerebrovascular Risk Factors

T2-weighted (0.5 T) magnetic resonance images were used to study the prevalence of subcortical white matter hyperintensities (WMHIs) in 22 patients with dementia of Alzheimer's type (DAT), 20 age-matched older healthy control subjects, and 10 younger healthy control subjects. Exclusionary criteria for all groups included cerebrovascular risk factors. All subjects had Hachinski Ischemic Index scores of less than 2 and computed tomographic scans showing no infarct. The WMHIs were classified as periventricular WMHIs or deep WMHIs and graded 0 through 3 (0 indicated absent, and 3, severe). For the group with DAT and older control subjects, periventricular WMHIs and deep WMHIs were graded 2 or 3 in fewer than 17% and 27% of subjects, respectively, whereas in the younger control subjects, all ratings were grade 1 or less. Serum cholesterol and systolic blood pressure values, although within the normal range, were elevated significantly in older control subjects when compared with those in younger control subjects. No significant differences in WMHI ratings, blood pressure, cholesterol, or triglyceride levels were found between patients with DAT and age-matched control subjects. Systolic blood pressure levels correlated with the severity of periventricular WMHIs only in older control subjects. Age correlated with periventricular WMHIs and deep WMHIs within both the older control subjects and the patients with DAT. There was no significant correlation between WMHIs and the severity of dementia in the group with DAT. These results suggest that, in subjects screened for cerebrovascular risk factors, WMHIs are rare and occur with identical frequency in patients with DAT as in age-matched healthy control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Line orientation judgment in normal elderly and subjects with dementia of Alzheimer's type

Ninety-five normal controls divided into three subgroups (55-64 yrs, 65-74 yrs, and 75-84 yrs) and 11 subjects with early dementia of Alzheimer's type (DAT) were given a line orientation judgment task (Benton, Varney, & Hamsher, 1978). No difference appeared between the three control subgroups in global score but the difference between controls and DAT subjects was significant. However, some DAT subjects had a global score overlapping the scores of controls. Error types were also analyzed. Results of this analysis showed that some errors appeared in all subjects, normal and DAT, while others were specific to DAT subjects. It was speculated that these error types were a manifestation of a deeper visuospatial deficit, revealing a major problem of the DAT in spatial organization. Thus, this study suggests that an analysis of the error types observed in the line orientation judgment task may be helpful in differentiating normal elderly from early DAT.

Reduced Gastrointestinal Absorption of Calcium in Dementia

Several reports have suggested that the neurodegenerative change in Alzheimer-type dementia (ATD) may be related to alterations in calcium homoeostasis. The absorption of radiocalcium (45Ca) in 26 ATD subjects and 11 patients with multi-infarct dementia (MID) was compared to 24 normal age- and sex-matched controls. The absorption of radiocalcium was significantly lower in both ATD and MID when compared to controls. The reduced 45Ca absorption in ATD occurred in the presence of normal plasma concentrations of PTH and vitamin D metabolites and the serum concentrations of calcium and aluminium were in the normal range. The data suggest that the reduced uptake of radioactive calcium observed in ATD is a non-specific derangement.

Distinguishing normal and demented elderly with the selective reminding test.

The selective reminding (SR) procedure, a popular technique for the study of verbal memory, was used to investigate aspects of memory functioning in a large group of normal elderly and in a smaller group of elderly subjects with Alzheimer Type Dementia (ATD). One hundred thirty-four normal elderly (mean age = 79.53 years) subjects and 21 ATD subjects (mean age = 68.3 years) were administered four versions of the SR test as part of a longitudinal study of risk factors in the development of dementia. Normative data were obtained for multiple components of memory functioning within the elderly sample. Test-retest reliability was .84 for long-term retrieval (LTR), .89 for sum of recall, and .92 for consistent retrieval. Clinical validity studies revealed that the components of sum of recall, storage estimate, LTR, and consistent long-term storage (CLTS) were most valuable in distinguishing mild ATD from normal aging. Positive predictive values ranged from 86% for CLTS, 89% for LTR, 91% for sum of recall, and 100% for storage estimate. These findings suggest that the SR test has considerable clinical utility in differentiating normal aging from dementia, and has promise as a useful tool in the preclinical detection of ATA.

Diffuse type of senile plaques in the cerebellum of Alzheimer-type dementia demonstrated by? protein immunostain

We studied senile plaques (SP) in the cerebella of six autopsied subjects with Alzheimer-type dementia (ATD) and ten non-ATD autopsied subjects between the ages of 78 and 90. Neither SP nor amyloid angiopathy (AA) was observed in any of the non-ATD subjects. In the four of the six ATD subjects, diffuse plaques in the molecular layer were seen as ill-defined areas of fine fibrillar materials by beta protein immunostaining with formic acid pretreatment, the modified Bielschowsky stain, and periodic acid-methenamine silver (PAM) stain. The plaques were not visible with Bodian, Congo red, or periodic acid-Schiff stains. Compact plaques in the Purkinje cell or in the granular cell layers were found in three of the six subjects. Their amyloid core was often surrounded by areolar amyloid deposits. AA was observed in three of the six subjects. The argyrophilia of the diffuse and compact plaques, demonstrated by the modified Bielschowsky and PAM stains, became undetectable when the sections were first treated with formic acid. Such treatment made the plaques immunoreactive with beta protein antiserum. The findings suggested that cerebellar diffuse plaques and compact plaques consist mainly of an amyloid component, and are characteristic of ATD.

Processes of verbal memory failure in alzheimer-type dementia

Multiple aspects of verbal learning and memory performance in mild as compared to moderate Alzheimer-type dementia (ATD) were studied with the Buschke selective reminding paradigm. Results show that (1) both groups of ATD subjects depend less on long-term memory (LTM) and more on short-term memory (STM) relative to elderly control subjects, (2) mild ATD subjects show less LTM encoding than moderate ATD subjects, (3) moderate ATD subjects retrieve a smaller portion of the items presumed to be encoded into LTM than do mild ATD subjects, and (4) high-imagery words increase LTM encoding and retrieval as compared to low-imagery words for moderate ATD subjects only. These results are explained by the inability of ATD subjects to attend to more than one component of the list-learning task, in conjunction with differences in the deployment of attention between mild and moderate ATD subjects.