Information content versus relational knowledge: Semantic deficits in patients with Alzheimer's disease

Olfactory function reflects episodic memory performance and atrophy in the medial temporal lobe in individuals at risk for Alzheimer's disease

We examined cognitive domains and brain regions associated with olfactory performance in cognitively unimpaired older adults (CU-OAs) and individuals with or at risk for Alzheimer's Disease (AD). We compared CU-OAs (N = 55), individuals with subjective cognitive decline (SCD, N = 55), mild cognitive impairment (MCI, N = 101), and AD (N = 45) on measures of olfactory function (Brief Smell Identification Test), cognition (episodic and semantic memory), and medial temporal lobe thickness and volume. Analyses controlled for age, sex, education, and total intracranial volume. Olfactory function decreased from SCD to MCI to AD. CU-OAs outperformed all groups except SCDs on tests of cognition and olfaction. Although these measures did not differ between the CU-OAs and SCDs, olfactory function correlated with episodic memory tests and with entorhinal cortex atrophy only in the SCD group. Olfactory function also correlated with hippocampal volume and right-hemisphere entorhinal cortex thickness in the MCI group. Olfactory dysfunction reflects medial temporal lobe integrity and memory performance in a group at risk for AD with normal cognition and olfaction.

Do Alzheimer's Disease Patients Benefit From Prior-Knowledge in Associative Recognition Memory?

OBJECTIVES

Although the influence of prior knowledge on associative memory in healthy aging has received great attention, it has never been studied in Alzheimer's disease (AD). This study aimed at assessing whether AD patients could benefit from prior knowledge in associative memory and whether such benefit would be related to the integrity of their semantic memory.

METHODS

Twenty-one AD patients and 21 healthy older adults took part in an associative memory task using semantically related and unrelated word pairs and were also submitted to an evaluation of their semantic memory.

RESULTS

While participants of both groups benefited from semantic relatedness in associative discrimination, related pairs recognition was significantly predicted by semantic memory integrity in healthy older adults only.

CONCLUSIONS

We suggest that patients benefitted from semantic knowledge to improve their performance in the associative memory task, but that such performance is not related to semantic knowledge integrity evaluation measures because the two tasks differ in the way semantic information is accessed: in an automatic manner for the associative memory task, with automatic processes thought to be relatively preserved in AD, and in a controlled manner for the semantic knowledge evaluation, with controlled processes thought to be impaired in AD. (JINS, 2019, 25, 443-452).

Alzheimer's Disease: Prototype of Cognitive Deterioration, Valuable Lessons to Understand Human Cognition

It is important for neurologists to become more familiar with neuropsychological evaluation for Alzheimer disease. The growth of this method in research, as an available, inexpensive, and noninvasive diagnostic approach, which can be administered even by non-specialist-trained examiners, makes this knowledge more necessary than ever. Such knowledge has a basic role in planning national programs in primary health care systems for prevention and early detection of Alzheimer disease. This is more crucial in developing countries, which have higher rates of dementia prevalence along with cardiovascular risk factors, lack of public knowledge about dementia, and limited social support. In addition compared to the neurological hard signs which are tangible and measurable, the concept of cognition seems to be more difficult for the neurologists to evaluate and for the students to understand. Dementia in general and Alzheimer's disease as the prototype of cognitive disorders specifically, play an important role to explore all domains of human cognition through its symptomatology and neuropsychological deficits.

The neural correlates of anomia in the conversion from mild cognitive impairment to Alzheimer's disease

INTRODUCTION

Language impairment is frequently observed in patients with Alzheimer's disease (AD): in this study, we investigated the extent and distribution of brain atrophy in subjects with conversion from mild cognitive impairment (MCI) to AD with and without naming difficulties.

METHODS

This study was approved by the institutional review board and was HIPAA compliant. All subjects or their legal representatives gave informed consent for participation. Ninety-one subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) with (N = 51) and without (N = 40) naming impairment as per the Boston Naming Test (BNT), underwent brain magnetic resonance (MR) imaging 12 months before, at AD diagnosis, and 12 months after. Structural MR images were processed using voxel-based morphometry. Cross-sectional comparisons and mixed ANOVA models for assessing regional gray matter (GM) volume differences were performed.

RESULTS

As from 12 months prior to AD diagnosis, patients with naming difficulties showed distinct areas of greater GM loss in the left fusiform gyrus (Brodmann area 20) than patients without naming difficulties. Differences in the GM atrophy extended to the left hemisphere in the subsequent 12 months.

CONCLUSION

This study provided evidence of distinct patterns and dynamics of brain atrophy in AD patients with naming difficulties when compared to those with intact language, as early as 12 months prior to AD diagnosis and in the subsequent 12 months.

Everyday-like memory for objects in ageing and Alzheimer's disease assessed in a visually complex environment: The role of executive functioning and episodic memory

To investigate everyday memory, more and more studies rely on virtual-reality applications to bridge the gap between in situ approaches and laboratory settings. In this vein, the present study was designed to assess everyday-like memory from the virtual reality-based Human Object Memory for Everyday Scenes (HOMES) test (Sauzéon et al., , Exp. Psychol., 59, 99) in ageing and in Alzheimer's disease (AD). Two aims motivated this study: the first was to assess multiple processes of episodic memory (EM) functioning embedded within contexts closely related to real life in ageing and AD using the multi-trial free-recall paradigm, and the second aim was to evaluate the mediating effects of executive functioning (EF), EM, and subjective memory complaints (SMCs) on age differences in the HOMES measures and in AD. To this end, the HOMES test and neurocognitive tests of EF and EM were administered to 23 younger adults, 23 older adults, and 16 patients with AD. The results were: firstly, compared to young adults, elderly adults presented only free-recall decline that almost disappeared in recognition condition whereas AD patients exhibited a poor clustering, learning, and recognition performance, and also a high amount of false recognition; secondly, age differences as well as AD related deficits on the HOMES test were mediated by both memory and EF measure while those observed on false memory indices were only mediated by EM measure; thirdly, the HOMES indices are related to SMCs even when episodic or EF measures are controlled. Overall, the results supported the fact that the VR-based memory test is an appropriate device to capture age-related differences as well as the AD effect with respect to both in situ and laboratory settings.

Language Disorders in Multilingual and Multicultural Populations

We review the characteristics of developmental language disorders (primary language impairment, reading disorders, autism, Down syndrome) and acquired language disorders (aphasia, dementia, traumatic brain injury) among multilingual and multicultural individuals. We highlight the unique assessment and treatment considerations pertinent to this population, including, for example, concerns of language choice and availability of measures and of normative data in multiple languages. A summary of relevant, recent research studies is provided for each of the language disorders selected.

Evaluating language comprehension in Alzheimer's disease: the use of the Token test

OBJECTIVE

To analyze the psychometric properties of the Token test (TT), a verbal comprehension test, and its applicability to the diagnosis of mild Alzheimer's disease (AD).

METHODS

One hundred and sixty participants (80 AD and 80 controls) performed the TT and a short battery of neuropsychological tests designed to evaluate general cognitive status, working memory and executive functions. Internal consistency, factor structure, correlation with other measures and group comparisons were evaluated.

RESULTS

The test evinced good internal consistency and a bi-factorial structure (related to comprehension and attention). Differences between AD and controls were significant, however the TT presented only moderate sensitivity and specificity for the AD diagnosis.

CONCLUSION

The TT showed evidence of good psychometric properties and adequacy for characterizing comprehension deficits in AD, but it was not an appropriate test for the AD detection and diagnosis.

The neuropsychological profile of Alzheimer disease

Neuropsychological assessment has featured prominently over the past 30 years in the characterization of dementia associated with Alzheimer disease (AD). Clinical neuropsychological methods have identified the earliest, most definitive cognitive and behavioral symptoms of illness, contributing to the identification, staging, and tracking of disease. With increasing public awareness of dementia, disease detection has moved to earlier stages of illness, at a time when deficits are both behaviorally and pathologically selective. For reasons that are not well understood, early AD pathology frequently targets large-scale neuroanatomical networks for episodic memory before other networks that subserve language, attention, executive functions, and visuospatial abilities. This chapter reviews the pathognomonic neuropsychological features of AD dementia and how these differ from "normal," age-related cognitive decline and from other neurodegenerative diseases that cause dementia, including cortical Lewy body disease, frontotemporal lobar degeneration, and cerebrovascular disease.

Altered brain response for semantic knowledge in Alzheimer's disease

Word retrieval deficits are common in Alzheimer's disease (AD) and are thought to reflect a degradation of semantic memory. Yet, the nature of semantic deterioration in AD and the underlying neural correlates of these semantic memory changes remain largely unknown. We examined the semantic memory impairment in AD by investigating the neural correlates of category knowledge (e.g., living vs. nonliving) and featural processing (global vs. local visual information). During event-related fMRI, 10 adults diagnosed with mild AD and 22 cognitively normal (CN) older adults named aloud items from three categories for which processing of specific visual features has previously been dissociated from categorical features. Results showed widespread group differences in the categorical representation of semantic knowledge in several language-related brain areas. For example, the right inferior frontal gyrus showed selective brain response for nonliving items in the CN group but living items in the AD group. Additionally, the AD group showed increased brain response for word retrieval irrespective of category in Broca's homologue in the right hemisphere and rostral cingulate cortex bilaterally, which suggests greater recruitment of frontally mediated neural compensatory mechanisms in the face of semantic alteration.

Size matters: a study on naming and size knowledge in dementia of the Alzheimer type

Category-specificity was longitudinally studied over a period of 12 months in seven Alzheimer disease patients, with two semantic tasks differing with respect to verbal processing demands: picture naming and a size ordering task. Items from each task were matched on all cognitive and psycholinguistic variables known to differ across domains (living-nonliving). Naming performance of patients was poorer than that of normal controls. Regarding category-specific effects, while naming performance of patients was parallel to that of normal controls, patients' performance with the size ordering task revealed a different scaling of living things while that of nonliving things mirrored performance of normal controls. This suggests that caution is needed when the picture naming task is exclusively used to document category-specific effects.

A common mechanism in verb and noun naming deficits in Alzheimer's patients

We tested the ability of Alzheimer's patients and elderly controls to name living and non-living nouns, and manner and instrument verbs. Patients' error patterns and relative performance with different categories showed evidence of graceful degradation for both nouns and verbs, with particular domain-specific impairments for living nouns and instrument verbs. Our results support feature-based, semantic representations for nouns and verbs and support the role of inter-correlated features in noun impairment, and the role of noun knowledge in instrument verb impairment.

Text comprehension products and processes in young, young-old, and old-old adults

Aging may be associated with an increase in generalized text processing, particularly in adults older than 75 years. The current study examined text comprehension in young, young-old, and old-old adults. Experiment 1 included a comprehension measure (product) and Experiment 2 examined inferences generated during reading (process). Comprehension scores were lowest in old-old adults. Generalized and elaborative inference scores were highest in old-old adults. Participants over 65 years with the lowest scores on cognitive integrity variables also had significantly lower comprehension scores, but there was no effect of cognitive integrity on inference scores. This dissociation suggests that inferential processes may be maintained even when cognitive integrity and comprehension declines are present. Relevance to cognitive aging theories addressing text processing and self-regulatory processes is addressed.

The impact of dementia, age and sex on category fluency: greater deficits in women with Alzheimer's disease

A category specific effect in naming tasks has been reported in patients with Alzheimer's dementia. Nonetheless, naming tasks are frequently affected by methodological problems, e.g., ceiling effects for controls and "nuisance variables" that may confound results. Semantic fluency tasks could help to address some of these methodological difficulties, because they are not prone to producing ceiling effects and are less influenced by nuisance variables. One hundred and thirty-three participants (61 patients with probable AD; and 72 controls: 36 young and 36 elderly) were evaluated with semantic fluency tasks in 14 semantic categories. Category fluency was affected both by dementia and by age: while in nonliving-thing categories there were differences among the three groups, in living thing categories larger lexical categories produced bigger differences among groups. Sex differences in fluency emerged, but these were moderated both by age and by pathology. In particular, fluency was smaller in female than male Alzheimer patients for almost every subcategory.

Language and Dementia: Neuropsychological Aspects

This article reviews recent evidence for the relationship between extralinguistic cognitive and language abilities in dementia. A survey of data from investigations of three dementia syndromes (Alzheimer's disease, semantic dementia and progressive nonfluent aphasia) reveals that, more often than not, deterioration of conceptual organization appears associated with lexical impairments, whereas impairments in executive function are associated with sentence- and discourse-level deficits. These connections between extralinguistic functions and language ability also emerge from the literature on cognitive reserve and bilingualism that investigates factors that delay the onset and possibly the progression of neuropsychological manifestation of dementia.