Early Stage Alzheimer's Disease Disrupts Encoding of Contextual Information

Two experiments examined whether impairments in recognition memory in early stage Alzheimer's disease (AD) were due to deficits in encoding contextual information. Normal elderly (NE) and patients diagnosed with mild stage AD learned one of two tasks. In Experiment 1 correct recognition memory required participants to remember not only what items they had experienced on a given trial but also when they had experienced them; Experiment 2 required that participants remember only what they had seen, not when they had seen it. Large recognition memory differences were found between the AD and NE groups in the experiment where time tagging was crucial for successful performance. An error analysis indicated that this was not due to the perseveration of previous learned responses. In Experiment 2, the only requisite for successful recognition was remembering what one had experienced; memory of the temporal record was not necessary for successful performance. In this instance, recognition memory for the NE and AD groups was identical. Taken together these results suggest that memory deficits found in early stage AD are partly due to impaired processing of contextual cues that provide crucial information about when events occur.     

Arithmetic difficulties in children with visuospatial learning disability (VLD).

Eighteen children with visuospatial learning disability (VLD) were compared to normal control children on a series of numerical and calculation tasks. Oral and written (dictated) calculation was assessed and operations differed not only in terms of the type of number processing requirements but also in terms of their visuospatial demand. The aim was to disentangle errors due to visuospatial processing failure from those deriving from incorrect knowledge of calculation procedures. Results showed that all children had relatively good knowledge of numerical facts and there was no statistical difference between the groups. No group difference was found in the overall performance in oral calculation, but a significant difference was present when the children were required to complete the operations in writing, with the VLD group achieving poorer performance than the controls. Furthermore, VLD children had greater difficulties when operations required borrowing or carrying; this was particularly problematic in subtractions. The results indicate that VLD children do not have a generalised problem with calculation per se or number manipulation in general. Rather their problems concern dealing with some processes that govern calculation especially those loading on visuospatial abilities.     

Intact Procedural Knowledge in Patients with Alzheimer's Disease: Evidence from Golf Putting

Can Alzheimer's disease (AD) patients efficiently learn to perform a complex motor skill when relying on procedural knowledge? To address this question, the authors compared the golf-putting performance of AD patients, older adults, and younger adults in 2 different learning situations: one that promotes high error rates (thus increasing the reliance on declarative knowledge) or one that promotes low error rates (thus increasing the reliance on procedural knowledge). Motor performance was poorer overall for AD patients and older adults relative to younger adults in the high-error condition but equivalent between similar groups in the low-error condition. Also, AD patients in the low-error condition had better performance at the final putting distance relative to those in the high-error condition. This performance facilitation for AD patients likely stems from intact procedural knowledge.     

Monitoring the Changing Status of Semantic Memory in Alzheimer's Disease: An Evaluation of Several Process Measures

The deficits in generating correct words on verbal fluency tasks exhibited by patients with Alzheimer's disease (AD) are accompanied by fewer switching responses, smaller phonemic and semantic cluster sizes, and greater than normal percentages of errors and category labels. On category fluency tasks, patients generate a greater proportion of words that are prototypical of their semantic class. To determine whether any of these supplementary measures of verbal fluency performance might be useful in revealing processes involved in the decline of semantic memory in AD, we studied 219 patients with AD and 115 elderly control participants longitudinally. Previously reported group differences between patients and controls were replicated, but changes in average cluster size, error rates, and prototypicality were not related to changes in overall severity of dementia and test-retest stability was only modest. The change in the percentage of labels generated on the Supermarket task was related to changes in dementia severity, but test-retest stability on this measure was quite low. All of these process measures appear to reflect only the current status of the patient's attention to the task and access to semantic knowledge, but they do not forecast future performance. The numbers of switching responses on the fluency tasks were sensitive to differences between clinically deteriorated and clinically stable patients and showed fairly high test-retest stability. However, the number of switching responses is so highly correlated with the number of correct words that it contributes little to the understanding of the processes involved in the progressive decline in performance on fluency tasks by patients with AD.     

知识整合的时间进程：ERP研究

本研究借助ERP技术,采用分离句子范式,考察了被试通过整合主干事实生成新知识的时间进程。结果发现：（1）知识整合事实相对于传递性推理事实和新颖事实诱发了更小的N400,与众所周知事实没有显著差异,表明通过整合生成的新信息已经快速纳入了语义知识库;（2）对比两次呈现,延迟性整合事实在第二次呈现的350ms之后波幅显著下降,与众所周知事实没有显著差异,表明知识经验影响了整合的时间进程,相较两个新信息之间的即时整合,新旧信息之间的延迟整合需要更多的时间。     

Social cognition and social functioning in patients with amnestic mild cognitive impairment or Alzheimer’s dementia

The aim of the present study was to examine social cognition and social functioning in a group of amnestic mild cognitive impairment (aMCI) and Alzheimer’s dementia (AD) patients. Thirty one people with aMCI, 29 individuals with AD, and 45 healthy older adults participated in the study. Facial expressions of happiness, anger, fear, disgust, and surprise presented in different intensities had to be labelled. Mentalizing was assessed using first-order belief theory of mind (ToM) stories and everyday social functioning by the Inventory of Interpersonal Situations (IIS), completed by an informant. aMCI patients were impaired in recognizing the emotions anger, disgust, and fear, while AD patients were impaired in recognizing the emotions anger, disgust, and surprise. More importantly, no significant differences between aMCI and AD patients were found on overall emotion recognition. Both the aMCI and AD patients were impaired on the ToM task, but no differences between the aMCI and AD patients were found. On everyday social functioning, only the AD patients showed impairments. No associations between the IIS and ToM were found, but the IIS and emotion perception were significantly correlated. Regression analysis taking all potentially confounding variables into account showed that only mood, but not the social-cognitive task performance or any other cognitive variable, predicted social functioning. aMCI and AD patients demonstrated impairments in mentalizing and facial emotion perception, and showed decrements in everyday social functioning. Informing caregivers about these deficits may help them to understand deficits in social cognition that may be present already in the MCI stage of Alzheimer’s disease.     

Learning of nondomain facts in high- and low-knowledge domains

Research on expertise has repeatedly documented that experts learn new information better than do novices, but only when the information is relevant to the expert's domain. It was found in Experiment 1 that participants showed superior learning and recall of a large quantity of new, non-domain-relevant facts about concepts within their domain of high knowledge than about concepts for which they had low domain knowledge. Experiment 2 investigated whether the participants' superior recall of new facts related to concepts within their domain of high knowledge was due to the number of prior facts associated with the concept or to the prior frequency of repetition of those concepts. It was found that participants' recall of new facts was better for concepts with 5 prior associated facts than for concepts with a single prior association but that the number of previous repetitions of each concept did not affect the level of recall for the new facts.     

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.     

Inductive Reasoning in Alzheimer''s Disease

We evaluated knowledge of basic level and superordinate semantic relations and the role of cognitive resources during inductive reasoning in probable Alzheimer's disease (AD). Nineteen mildly demented AD patients and 17 healthy control subjects judged the truthfulness of arguments with a premise and a conclusion that contain familiar concepts coupled with "blank" predicates, such as "Spiders contain phosphatidylcholine; therefore all insects contain phosphatidylcholine." Like healthy control subjects, AD patients were relatively insensitive to the typicality of the premise category when judging the strength of arguments with a conclusion containing a basic-level concept, but were relatively sensitive to typicality during judgments of arguments containing a superordinate in the conclusion. Moreover, AD patients resembled control subjects in judging arguments with an immediate superordinate in the conclusion compared to arguments with a distant superordinate. AD patients differed from control subjects because they could not take advantage of two premises in an argument containing basic-level concepts. We conclude that semantic knowledge is sufficiently preserved in AD to support inductive reasoning, but that limited cognitive resources may interfere with AD patients' ability to consider the entire spectrum of information available during semantic challenges.     

Visual Imagery Processing and Knowledge of Famous Names in Alzheimer's Disease and MCI

ABSTRACT

The study of memory for famous people and visual imagery retrieval was investigated in patients in the early stages of Alzheimer's disease (AD) and in the prodromal stage of AD, so-called Mild Cognitive Impairment (MCI). Fifteen patients with AD (MMSE ≥23), 15 patients with amnestic MCI (a-MCI) and 15 normal controls (NC) performed a famous names test designed to evaluate the semantic and distinctive physical features knowledge of famous persons. Results indicated that patients with AD and a-MCI generated significantly less physical features and semantic biographical knowledge about famous persons than did normal control participants. Additionally, significant differences were observed between a-MCI and AD patients in all tasks. The present findings confirm recent studies reporting semantic memory impairment in MCI. Moreover, the current findings show that mental imagery is lowered in a-MCI and AD and is likely related to the early semantic impairment.     

Developmental dissociation in the neural responses to simple multiplication and subtraction problems

Mastering single‐digit arithmetic during school years is commonly thought to depend upon an increasing reliance on verbally memorized facts. An alternative model, however, posits that fluency in single‐digit arithmetic might also be achieved via the increasing use of efficient calculation procedures. To test between these hypotheses, we used a cross‐sectional design to measure the neural activity associated with single‐digit subtraction and multiplication in 34 children from 2nd to 7th grade. The neural correlates of language and numerical processing were also identified in each child via localizer scans. Although multiplication and subtraction were undistinguishable in terms of behavior, we found a striking developmental dissociation in their neural correlates. First, we observed grade‐related increases of activity for multiplication, but not for subtraction, in a language‐related region of the left temporal cortex. Second, we found grade‐related increases of activity for subtraction, but not for multiplication, in a region of the right parietal cortex involved in the procedural manipulation of numerical quantities. The present results suggest that fluency in simple arithmetic in children may be achieved by both increasing reliance on verbal retrieval and by greater use of efficient quantity‐based procedures, depending on the operation.     

Prosaccade and Antisaccade Paradigms in Persons with Alzheimer’s Disease: A Meta-Analytic Review

Persons with Mild Cognitive Impairment (MCI) are at high Alzheimer’s Disease (AD) risk but the development of sensitive measures to assess subtle cognitive decline in this population poses a major challenge for clinicians and researchers. Eye movement monitoring is a non-invasive, sensitive way to assess subtle cognitive processes in clinical populations. We conducted a critical review and a meta-analysis of the literature on pro and antisaccade paradigm in AD/MCI. The meta-analysis included 20 studies, all of which used the prosaccade paradigm and 13 of which studied the antisaccade paradigm as well. Our meta-analysis showed that AD but not MCI patients showed longer prosaccade latencies when compared to controls. While antisaccade latencies did not differentiate between patients from controls, antisaccade error rate were significantly increased among patients in comparison to controls in over 87% of the studies. These findings highlight antisaccade error rate as a reliable tool to distinguish inhibition abilities between AD/MCI and healthy older persons.     

Use of the Hayling task to measure inhibition of prepotent responses in normal aging and Alzheimer's disease

This study measures the effect of Alzheimer's disease (AD) and normal aging on the inhibition of prepotent responses. AD patients, normal aged controls, and young subjects were tested with the Hayling task, which measures the ability to inhibit a semantically constrained response, and with the Stroop procedure. AD patients showed a severe deficit in both error rates and response time on the Hayling task. Inhibition was also impaired on the Stroop procedure, both when using raw performance and when using an inhibition score that controlled for reading and naming speed. Normal aged participants showed modest impairment relative to young controls on both tests. Examination of individual performance in AD patients indicated that the impairment was found in most patients on the Hayling test but in only a subgroup of patients on the Stroop test.     

Neuropsychological indicators of preclinical Alzheimer’s disease among depressed older adults

Older adults with major depressive disorder (MDD) may also have preclinical Alzheimer’s disease (AD). Differential diagnosis is quite challenging due to the overlapping symptoms of MDD and AD. In the current study, we predicted that impaired long-term memory (an area most affected in early AD), but not executive function (an area affected in MDD and AD), would distinguish older depressed patients who developed AD from those who did not. Patients (N = 120) assessed as having MDD but not dementia at baseline were administered tests of cognitive function and followed longitudinally for subsequent diagnosis of AD. Using structural equation modeling we found a latent construct of long-term memory to be associated with AD to a greater extent than executive functioning. Additional analyses to enhance clinical utility of findings indicated that individual tests of episodic memory were most predictive of AD status. Tests of long-term memory can be utilized by the clinician when assessing for preclinical AD among depressed elderly.     

Remote Odor Memory in Alzheimer's Disease: Deficits as Measured by Familiarity

Deficit in olfaction and remote nonolfactory memory in Alzheimer's disease (AD) motivated the present study of remote memory for odors and faces, operationally defined as rated familiarity, in patients with AD and controls. Uncommon engineering symbols were rated for familiarity to ensure task comprehension. Results showed that patients with AD rate odors, but not faces, as significantly less familiar than do controls, which is indicative of deficit in remote odor memory. Follow-up testing 1 year later again showed this result. Poor odor-detection sensitivity in patients, with AD, but lack of significant correspondence between sensitivity and familiarity, suggests an existing but limited effect of sensitivity on familiarity. The findings provide further evidence that olfaction may be a useful modality for early identification of AD.     

Articulatory rehearsal in Alzheimer type dementia

This study investigated the relationship between articulation rate and memory span in a sample of 21 patients with early Alzheimer type dementia (AD), comparing their performance with 21 matched controls. Memory span was measured using auditorily and visually presented digits. The AD patients were moderately impaired in both conditions. Articulation rate was measured either by requiring subjects to read lists of random digits or repeatedly count from 1 to 10. The AD patients were able to read the digits as fast as the controls but were slower in the counting task. The measures of memory span and articulation rate correlated significantly for the controls but not for the AD patients, indicating that the normal association between articulation and memory span is disrupted. These results are discussed in relation to previous results and suggest that articulatory rehearsal processes in primary memory are unimpaired at the early stages of AD.     

Representation-saving effects of prior knowledge in memory for simple technical prose

Prior knowledge of the content of a passage should reduce the effort required to encode the passage and facilitate its recall. This paper presents such effects of prior knowledge upon comprehension and memory of simple technical prose. The basic procedure was to collect ratings of the amount of prior knowledge for individual passage sentences and individual subjects, and then to determine whether these familiarity ratings predicted study time and recall. In order to validate the rating method, and also to obtain data on prior knowledge of individual facts, subjects also completed an objective test of prior knowledge of the passage facts. Three different encoding-task conditions were used: a self-paced study task, a forced-pace study task, and an incidental-learning task. A cued-recall test followed each condition. In the self-paced task, readers studied unfamiliar material longer than familiar material, but recalled at the same level regardless of familiarity. In contrast, familiarity did predict recall in the forced-pace and incidental tasks. This task specificity is explained in terms of the subjects’ encoding strategies. The basic effect of prior knowledge can be explained not only by the elaboration principle, but also by a representation-saving principle, which is presented in a simulation model that can account for the effects of familiarity on study time.     

Transcoding abilities in typical and atypical mathematics achievers: The role of working memory and procedural and lexical competencies

Transcoding between numerical systems is one of the most basic abilities acquired by children during their early school years. One important topic that requires further exploration is how mathematics proficiency can affect number transcoding. The aim of the current study was to investigate transcoding abilities (i.e., reading Arabic numerals and writing dictation) in Brazilian children with and without mathematics difficulties, focusing on different school grades. We observed that children with learning difficulties in mathematics demonstrated lower achievement in number transcoding in both early and middle elementary school. In early elementary school, difficulties were observed in both the basic numerical lexicon and the management of numerical syntax. In middle elementary school, difficulties appeared mainly in the transcoding of more complex numbers. An error analysis revealed that the children with mathematics difficulties struggled mainly with the acquisition of transcoding rules. Although we confirmed the previous evidence on the impact of working memory capacity on number transcoding, we found that it did not fully account for the observed group differences. The results are discussed in the context of a maturational lag in number transcoding ability in children with mathematics difficulties.     

Can cognitive and behavioural disorders differentiate frontal variant-frontotemporal dementia from Alzheimer's disease at early stages?

Frontal variant-Frontotemporal dementia (fvFTD) and Alzheimer's disease (AD) patients matched for severity of dementia at the Clinical Dementia Rating (CDR) received neuropsychological testing in order to explore if the dysexecutive disorder might characterise fvFTD at early stage, when AD is dominated by the episodic memory defect. We also determined if the behavioural syndrome was more severe in fvFTD than AD, and if specific patterns of behavioural symptoms could differentiate the two types of dementia, using the Neuropsychiatry Inventory (NPI). AD patients performed worse than fvFTD not only in memory but also in executive tasks. Apathy and eating disorders proved to be more severe or frequent in fvFTD even if the two groups did not differ in the total NPI score. CDR score significantly correlated with the NPI score in fvFTD and with the MMSE in AD. Our data confirm that the memory disorders may differentiate the two types of dementia; however, the dysexecutive syndrome is as severe, and even more severe in AD. The severity of the behavioural syndrome is comparable in the two groups but the nature of the behavioural disorders may vary to some extent. We conclude that AD dementia at early stage is a behavioural-cognitive syndrome, while in fvFTD the behavioural disorders appear when the cognitive deficit is still relatively mild.