Event-related brain potential evidence of spared knowledge in Alzheimer's disease

The authors recorded event-related brain potentials (ERPs) to picture primes and word targets (picture-name verification task) in patients with Alzheimer's disease (AD) and in elderly and young participants. N400 was more negative to words that did not match pictures than to words that did match pictures in all groups: In the young, this effect was significant at all scalp sites; in the elderly, it was only at central-parietal sites; and in AD patients, it was limited to right central-parietal sites. Among AD patients pretested with a confrontation-naming task to identify pictures they could not name, neither the N400 priming effect nor its scalp distribution was affected by ability to name pictures correctly. This ERP evidence of spared knowledge of these items was complemented by 80% performance accuracy. Thus, although the name of an item may be inaccessible in confrontation naming, N400 shows that knowledge is intact enough to prime cortical responses.     

Preservation of categorical knowledge in Alzheimer's disease: A computational account

Abstract

The distinction between knowledge of specific exemplars and knowledge of their general categories is central to much theorising on the nature of semantic memory. The dissociation between exemplar and category knowledge observed in Alzheimer's Disease (AD) would appear to support this distinction, and to suggest that different neural systems are involved in the representation of exemplar and category knowledge. We review the evidence for preserved category knowledge in the semantic memory impairment of AD, and propose an alternative interpretation, according to which category and exemplar knowledge are both represented in the same distributed neural substrate. The relative preservation of category knowledge is a consequence of the greater frequency, and hence greater robustness, of the representation of attributes shared by all or most members of a category, compared to exemplar-unique attributes. We test and confirm the computational adequacy of this hypothesis in two computer simulations.     

Category knowledge in Alzheimer's disease: normal organization and a general retrieval deficit.

Three hypotheses that could account for deficits in the retrieval of category information in Alzheimer's disease (AD) were evaluated: abnormal organization, class- or category-specific vulnerability, and limitation by general factors, such as decreased processing speed. Relative to 18 elderly control subjects, 18 patients with AD produced fewer items in a category fluency task and had longer reaction times in a category decision task. The pattern of performance across categories on both tasks was normal in the AD group: The same categories elicited the most (or fastest) responses in both the control group and the AD group. AD patients showed normal performance in ranking of category exemplars by typicality. There was no evidence for differential accessibility by category or by class of information (animate vs. inanimate). The authors conclude that a general factor or factors limit(s) retrievability equally across all categories.     

The effect of knowledge of mathematics on gambling behaviours and erroneous perceptions

This study evaluates the effect of knowledge of mathematics as a protective factor against excessive gambling behaviours and erroneous beliefs. Two groups with different levels of knowledge of mathematics were compared as to their perceptions and behaviours before and during a gambling session. A total of 60 participants (30 men, 30 women) completed a questionnaire evaluating how they perceive the notion of chance and participated in two experimental tasks: the production of a random sequence of heads/tails, and a gambling session on a video lottery terminal. The results show that participants with knowledge of mathematics held more erroneous perceptions of gambling before the experiment whereas both groups showed an equal number of erroneous perceptions and behaviours during gambling. The importance of knowledge of mathematics as a protective factor against excessive gambling is questionable. The theoretical and practical implications of these results are discussed with regard to the prevention of excessive gambling.     

Aging persons' estimates of vehicular motion.

Estimated arrival times of moving autos were examined in relation to viewer age, gender, motion trajectory, and velocity. Direct push-button judgments were compared with verbal estimates derived from velocity and distance, which were based on assumptions that perceivers compute arrival time from perceived distance and velocity. Experiment 1 showed that direct estimates of younger Ss were most accurate. Older women made the shortest (highly cautious) estimates of when cars would arrive. Verbal estimates were much lower than direct estimates, with little correlation between them. Experiment 2 extended target distances and velocities of targets, with the results replicating the main findings of Experiment 1. Judgment accuracy increased with target velocity, and verbal estimates were again poorer estimates of arrival time than direct ones, with different patterns of findings. Using verbal estimates to approximate judgments in traffic situations appears questionable.     

Alzheimer's disease and the loss of self

This article focuses on the fact that persons (including the author) who are entering the later stages of life are confronted with the real possibility that they may become afflicted with Alzheimer's disease. It proposes an alternative to speculating about one's own chances of becoming afflicted, which is to enter imaginatively into the world of the Alzheimer's patient, and uses contemporary poems to assist in this regard. It notes that the author's attempt to "join the patient" led to the realization that Alzheimer's disease does not, as is commonly believed, completely obliterate the self. Recognizing the inevitable limits of one's ability to imagine what it is like to suffer from Alzheimer's disease, it advocates the embracing of forgetfulness as an integral part of the self.     

Singaporean education students' perceptions of knowledge and skills as important for teachers

This paper examined perceptions of knowledge and skills important for teachers of 353 Singaporean undergraduate students. They rated higher teaching and nurturing skills and gave moderate ratings to theoretical knowledge and research skills. There is a need to raise teachers' awareness of educational research and theoretical innovation for classroom practice.     

CT scan and neuropsychological correlates of Alzheimer's disease and Huntington's disease

"Cortical" and "subcortical" dementia syndromes differ in areas of primary neuropathology and clinical characteristics. Conventional CT scan interpretation, visual inspection of pictures, has not been useful in studying dementia. Recent studies of the digitally stored CT attenuation values have found systematic variations with normal aging and aphasia subtypes. In this study of numerical CT scan information in four Alzheimer's Disease and two Huntington's Disease patients, a double dissociation of frontal and temporal lobe density values was found, and a significant correlation was found between left temporal lobe density and verbal ability measures in the Alzheimer's Disease patients.     

Self-image bias and the perception of other persons' skills

Previous research on the Self-image bias' has demonstrated a defensive tendency to overestimate the importance of positive general self-attributes (e.g. warm, patient) when forming impressions of other people. The current research replicates and extends the self-image bias findings in an area of theoretical as well as applied relevance: The evaluation of other peoples specific skills, and resulting social preferences.     

Posture recognition in Alzheimer's disease

BACKGROUND: Apraxia is neurologically induced deficit in the ability perform purposeful skilled movements. One of the most common forms is ideomotor apraxia (IMA) where spatial and temporal production errors are most prevalent. IMA can be associated Alzheimer's disease (AD), even early in its course, but is often not identified possibly because the evaluation of IMA by inexperienced judges using performance tests is unreliable. The purpose of this study, therefore, is to learn if the Postural Knowledge Test (PKT), a praxis discrimination test that assesses knowledge of transitive (PKT-T subtest) and intransitive (PKT-I subtest) postures and does not require extensive training, is as sensitive and specific as the praxis performance tests. METHODS: We studied 15 subjects with probable AD as well as 18 age-matched controls by having them perform transitive and intransitive gestures to command and imitation, as well as having them discriminate between correct and incorrect transitive and intransitive postures. RESULTS: Overall on all tests, the control subjects performed better than those with AD. In addition all subjects had more trouble with transitive than intransitive gestures. Using a stepwise discriminative analysis, 81.8% of the subjects could be classified according to Group (94.4% of Controls, 66.7% of AD subjects). In this analysis, the PKT-T (transitive posture subtest) was the only measure that contributed to the discrimination of subjects. CONCLUSION: We found that having subjects select the correct transitive hand postures in this "booklet test" was more sensitive than grading their praxis performances even when using judges with extensive training. This suggests that this discrimination test might be an excellent means for diagnosing and screening patients for AD. The reason why recognition of transitive postures is relatively more difficult for our AD subjects is not known. Two possibilities are that the representations for intransitive movements are stronger than those for transitive movements, and hence, more resistant to degradation, or that intransitive acts are stored in parts of the brain not affected by AD.     

Confabulation in Alzheimer's disease.

Confabulation is present when memory is disturbed, but does it occur in Alzheimer's disease (AD) where memory abnormalities are often severe? In this study, confabulation was assessed prospectively in 26 AD patients and 15 normal elderly (NE) controls using a neuropsychological battery specifically designed to assess different types of memory errors. The results indicated that the AD group made significantly more verbal intrusions than the NE group. These findings provide evidence for the feasibility of eliciting confabulatory-type behavior during clinical assessment and support previous reports which have documented verbal intrusions as a common accompaniment of the memory impairment manifested by AD patients.     

Semantic memory in Alzheimer's disease

Patients with Alzheimer's disease have been suggested to have a semantic memory impairment not present in the normal old. This article reviews the performance of Alzheimer patients on tests of various aspects of semantic memory, including word finding, knowledge of the semantic attributes, and associates of concepts, as well as their category membership. The effect that semantic context has on cognitive processes such as lexical and semantic priming and memory encoding is also reviewed. Finally, the ability of theoretical constructs such as implicit memory and automaticity to explain intertask variability in Alzheimer patients' semantic performance is discussed.     

Maze learning in Alzheimer's disease

Alzheimer's disease (AD) patients and normal elderly controls performed a block of 10 trials on a finger maze, followed by a 45-min period during which verbal learning measures were administered. Subjects then performed an additional 10 trials on the original maze, followed by 10 trials on a new maze. The AD patients and a subset of control subjects decreased mean completion time across Blocks 1 and 2, suggesting skill acquisition. Mean time on Block 3 was significantly less than mean time on Block 1, suggesting skill generalization. A subset of controls did not show the above pattern. The results of this study suggest that AD patients are able to acquire and generalize a cognitively mediated perceptual-motor skill.     

Relation of occupational knowledge to career interests and competence perceptions in Italian children

The relations of differential occupational knowledge with interests and competence perceptions in children as well as how these relations were moderated by gender and grade were examined in this study using an Italian sample. Data were collected from samples of elementary school and middle school children (N = 539). The Inventory of Children's Activities—Revised (ICA-R; Tracey & Ward, 1998) was used to assess children's interest and competency perceptions in various activities associated with the Holland's RIASEC types. The Occupational Knowledge Scale (OKS) was created for this study, and consisted of a representative sampling of occupational titles to which children indicated their knowledge. Hierarchical regression results indicated a relationship between knowledge, interests, and competence perceptions in children. With regard to overall knowledge, no relationship was found between general knowledge and either grade or gender. More specific examination of the type of knowledge as it varied across the dimensions of People–Things, and Data–Ideas demonstrated that there appeared to be a specific pattern relating interest, gender, and grade to knowledge of occupations. For knowledge of people relative to things occupations, higher interest, higher grade level, and being female predicts stronger knowledge of people occupations. It was also found that interest in ideas predicts stronger knowledge of ideas occupations, and being male predicts stronger knowledge of high prestige occupations. Generally, competence perceptions did not have a unique relation with one's knowledge of People–Things, Ideas–Data, or Prestige; however, girls who reported higher competence had greater knowledge of ideas occupations.     

Relation of occupational knowledge to career interests and competence perceptions in Italian children

The relations of differential occupational knowledge with interests and competence perceptions in children as well as how these relations were moderated by gender and grade were examined in this study using an Italian sample. Data were collected from samples of elementary school and middle school children (N = 539). The Inventory of Children's Activities—Revised (ICA-R; Tracey & Ward, 1998) was used to assess children's interest and competency perceptions in various activities associated with the Holland's RIASEC types. The Occupational Knowledge Scale (OKS) was created for this study, and consisted of a representative sampling of occupational titles to which children indicated their knowledge. Hierarchical regression results indicated a relationship between knowledge, interests, and competence perceptions in children. With regard to overall knowledge, no relationship was found between general knowledge and either grade or gender. More specific examination of the type of knowledge as it varied across the dimensions of People–Things, and Data–Ideas demonstrated that there appeared to be a specific pattern relating interest, gender, and grade to knowledge of occupations. For knowledge of people relative to things occupations, higher interest, higher grade level, and being female predicts stronger knowledge of people occupations. It was also found that interest in ideas predicts stronger knowledge of ideas occupations, and being male predicts stronger knowledge of high prestige occupations. Generally, competence perceptions did not have a unique relation with one's knowledge of People–Things, Ideas–Data, or Prestige; however, girls who reported higher competence had greater knowledge of ideas occupations.