A longitudinal study of semantic memory impairment in patients with Alzheimer’s disease

Free-listing and Semantic Knowledge: A Tool for Detecting Alzheimer Disease?

BACKGROUND

Impairment in semantic knowledge contributes to Alzheimer disease (AD)-related decline. However, the particulars of the impact AD has on specific domains of knowledge remain debatable.

OBJECTIVE

To investigate the impact of AD on specific semantic categories that are integral to daily functions-living things and man-made objects.

METHOD

We administered a free-listing task (written version) to 19 individuals with AD and 15 cognitively normal older adults and assessed the task's relationship with other cognitive and functional tests in clinical use. We compared the contents of the lists of salient concepts generated by the AD and control groups.

RESULTS

Group membership (AD or control), after controlling for age, sex, formal education, and an estimate of premorbid intellectual ability, predicted the groups' performance on the free-listing task across two categories. Functional status was inversely related to performance on the free-listing task, holding demographic variables constant. Based on a comparison of the contents of the free lists that were generated by the two groups, it was possible to conclude that, in individuals with AD, conceptual knowledge central to the respective categories was well preserved, whereas the peripheral conceptual material showed evidence of degradation.

CONCLUSION

The free-listing task, which is an easy-to-administer and cost-effective tool, could aid in the preliminary detection of semantic knowledge dysfunction, revealing concepts that are better preserved and, possibly, the characterization of AD. Cognitive assessment tools that can be applied across cultures are needed, and the free-listing task has the potential to address this gap.

A network psychometric approach to neurocognition in early Alzheimer's disease

In a typical pattern of Alzheimer's disease onset, episodic memory decline is predominant while decline in other neurocognitive domains is subsidiary or absent. Such descriptions refer to relationships between neurocognitive domains as well as deficits within domains. However, the former relationships are rarely statistically modelled. This study used psychometric network analysis to model relationships between neurocognitive variables in cognitive normality (CN), amnestic mild cognitive impairment (aMCI), and early Alzheimer's disease (eAD). Gaussian graphical models with extended Bayesian information criterion graphical lasso model selection and regularisation were used to estimate network models of neurocognitive and demographic variables in CN (n = 229), aMCI (n = 395), and eAD (n = 191) groups. The edge density, network strength and structure, centrality, and individual links of the network models were explored. Results indicated that while global strength did not differ, network structures differed across CN and eAD and aMCI and eAD groups, suggesting neurocognitive reorganisation across the eAD continuum. Episodic memory variables were most central (i.e., influential) in the aMCI network model, whereas processing speed and fluency variables were most central in the eAD network model. Additionally, putative clusters of memory, language and semantic variables, and attention, processing speed and working memory variables arose in the models for the clinical groups. This exploratory study shows how psychometric network analysis can be used to model the relationships between neurocognitive variables across the eAD continuum and to generate hypotheses for future (dis)confirmatory research.

How do patients with Alzheimer's disease imagine their pain?

INTRODUCTION

Pain is underdiagnosed and undertreated in patients with Alzheimer's disease (AD). Pain management is of major importance in this population to limit behavioural and functional consequences. Our study aimed to assess the capacity of AD patients to represent pain using a questionnaire exploring daily painful situations and to determine the most appropriate pain scale assessment.

METHODS

Twenty-eight patients with mild AD, 21 with moderate AD and 28 matched controls underwent the Situation Pain Questionnaire (SP-Q) and assessed imaginary pain with four pain scales. Two scores were compared between the three groups: the P(A) discrimination score and the response bias β score. P(A) reflects the degree of discrimination between high-pain and low-pain events, whereas the β score means the degree to which situations are considered as painful.

RESULTS

Our results showed that AD patients hardly discriminated the high- from low-pain events. Compared to controls, the mean P(A) score was significantly lower for Mild AD (p < 0.03) and Moderate AD (p < 0.004). In addition, the β score indicated that the response bias is higher for AD patients (p < 0.01) in that they overestimated the level of pain.

CONCLUSION

The present results suggest that patients with Mild and Moderate AD are able to recognize and assess an imagined painful situation even though their pain tolerance is lower than that of controls. The pain scales used should be chosen according to the cognitive, sensorial and personal profiles of the patients.

SIGNIFICANCE

The present research is significant because it examines how patients with Alzheimer's disease understand and assess painful situations. Cognitive impairments can modify this ability. Pain is a sensory and subjective experience and to define its feeling can help us in our clinical practice.

Assessment of semantic memory in mild cognitive impairment: The psychometric properties of a novel semantic battery

Semantic memory is stable in healthy older adults but shows decline in mild cognitive impairment (MCI). Current measures of semantic function do not assess multiple aspects of semantic function and/or are time-consuming to administer. Here we report the psychometric properties of a battery to detect semantic impairment that we recently developed and published. Study 1 determined the face validity of the battery; interviews were conducted with five professionals with expertise in MCI and language. Face validity interviews suggested the battery appropriately assesses semantic impairments. Study 2 assessed convergent validity and reliability (inter-rater reliability, test-retest reliability, and internal consistency). Participants included 102 healthy older adults and 60 people with MCI who completed a four-task semantic battery. Results demonstrate that performance on the semantic battery correlates with traditional measures of semantic function, inter-rater reliability and internal consistency was high, and there was no significant change in mean scores between participants' first and second testing sessions. The present findings suggest that the semantic battery is a reliable and valid assessment of semantic function. It is currently recommended for research use only.

Alterations of Graphic Properties and Related Cognitive Functioning Changes in Mild Alzheimer's Disease Revealed by Individual Morphological Brain Network

Alzheimer’s disease (AD) is one of the most common forms of dementia that has slowly negative impacts on memory and cognition. With the assistance of multimodal brain networks and graph-based analysis approaches, AD-related network disruptions support the hypothesis that AD can be identified as a dysconnectivity syndrome. However, as the recent emerging of individual-based morphological network research of AD, the utilization of multiple morphometric features may provide a broader horizon for locating the lesions. Therefore, the present study applied the newly proposed individual morphological brain network with five commonly used morphometric features (cortical thickness, regional volume, surface area, mean curvature, and fold index) to explore the topological aberrations and their relationship with cognitive functioning alterations in the early stage of AD. A total of 40 right-handed participants were selected from Open Access Series of Imaging Studies Database with 20 AD patients (age ranged from 70 to 79, CDR = 0.5) and 20 age/gender-matched healthy controls. The significantly affected connections (p < 0.05 with FDR correction) were observed across multiple regions, both enhanced and attenuated correlations, primarily related to the left entorhinal cortex (ENT). In addition, profoundly changed Mini Mental State Examination (MMSE) score and global efficiency (p < 0.05) were noted in the AD patients, as well as the pronounced inter-group distinctions of betweenness centrality, global and local efficiency (p < 0.05) in the higher MMSE score zone (28–30), which indicating the potential role of graphic properties in determination of early-stage AD patients. Moreover, the reservations (regions in the occipital and frontal lobes) and alterations (regions in the right temporal lobe and cingulate cortex) of hubs were also detected in the AD patients. Overall, the findings further confirm the selective AD-related disruptions in morphological brain networks and also suggest the feasibility of applying the morphological graphic properties in the discrimination of early-stage AD patients.

Developing Cognitive Markers of Alzheimer's Disease for Primary Care: Implications for Behavioral and Global Prevention

A comprehensive approach to the prevention of Alzheimer's disease (AD) warrants a synergy across multiple domains and procedures. Whereas the study of biological markers has mobilized major activity in the field, the development of cognitive markers is largely ignored, despite the unique advantages they may offer. Cognitive markers essentially assess the core clinical feature that biological markers intend to predict. In this respect, cognitive markers expand the foundation of preclinical diagnostics and disease staging in a manner that integrates both physiological and psychological factors. In addition, the cost-effective implementation of cognitive markers makes them remarkably conducive to community-wide screenings, and thereby a vital component of any global blueprint for prevention. Specifically, in the primary care setting, cognitive markers may provide effective gate keeping for more invasive, labor intensive, and expensive procedures. From this perspective, cognitive markers may provide the first step for identifying preclinical treatment recipients in general public. Moreover, the detection of preclinical decline via cognitive markers can increase awareness of AD risk and the motivation for making protective lifestyle changes. The behavioral approach might be expedient for prevention in light of the compelling evidence of lifestyle amelioration of AD risk. In an integrative view, incorporating cognitive markers to primary care may facilitate a synergetic development in preventive interventions that carries epidemiological significance. This paper addresses the theoretical, methodological, and pragmatic aspects of this prospect.

Semantic memory and depressive symptoms in patients with subjective cognitive decline, mild cognitive impairment, and Alzheimer's disease

BACKGROUND

Semantic memory may be impaired in clinically recognized states of cognitive impairment. We investigated the relationship between semantic memory and depressive symptoms (DS) in patients with cognitive impairment.

METHODS

323 cognitively healthy controls and 848 patients with subjective cognitive decline (SCD), mild cognitive impairment (MCI), and Alzheimer's disease (AD) dementia were included. Semantic knowledge for famous faces, world capitals, and word vocabulary was investigated.

RESULTS

Compared to healthy controls, we found a statistically significant difference of semantic knowledge in the MCI groups and the AD group, respectively. Results of the SCD group were mixed. However, two of the three semantic memory measures (world capitals and word vocabulary) showed a significant association with DS.

CONCLUSIONS

We found a difference in semantic memory performance in MCI and AD as well as an association with DS. Results suggest that the difference in semantic memory is due to a storage loss rather than to a retrieval problem.

Apolipoprotein E (APOE) ε4 and episodic memory decline in Alzheimer's disease: A review

A growing body of research has examined the relationship between episodic memory decline, the cognitive hallmark of Alzheimer's disease (AD), and the presence of Apolipoprotein E ε4 (APOE ε4) allele, a major genetic risk factor for the disease. Our review attempts to summarize and critically evaluate this literature. We performed a systematic search for studies assessing episodic memory in AD patients who were genotyped for APOE ε4 and identified fourteen papers. Although most of these papers reported significant relationships between APOE ε4 and episodic memory decline in AD, some papers did not confirm this relationship. Our review links this controversy to the conflicting literature about the effects of APOE ε4 on general cognitive functioning in AD. We identify several shortcoming and limitations of the research on the relationship between APOE ε4 and episodic memory in AD, such as small sample sizes, non-representative populations, lack of comparison of early-onset vs. late-onset disease, and lack of comparison among different genotypes that include APOE ε4 (i.e., zero, one, or two ε4 alleles). Another major shortcoming of the reviewed literature was the lack of comprehensive evaluation of episodic memory decline, since episodic memory was solely evaluated with regard to encoding and retrieval, omitting evaluation of core episodic features that decline in AD, such as context recall (e.g., how, where, and when an episodic event has occurred) and subjective experience of remembering (e.g., reliving, emotion and feeling during episodic recollection). Future research taking these limitations into consideration could illuminate the nature of the relationship between APOE ε4 and episodic memory decline in AD.

Semantic Processing Impairment in Patients with Temporal Lobe Epilepsy

The impairment in episodic memory system is the best-known cognitive deficit in patients with temporal lobe epilepsy (TLE). Recent studies have shown evidence of semantic disorders, but they have been less studied than episodic memory. The semantic dysfunction in TLE has various cognitive manifestations, such as the presence of language disorders characterized by defects in naming, verbal fluency, or remote semantic information retrieval, which affects the ability of patients to interact with their surroundings. This paper is a review of recent research about the consequences of TLE on semantic processing, considering neuropsychological, electrophysiological, and neuroimaging findings, as well as the functional role of the hippocampus in semantic processing. The evidence from these studies shows disturbance of semantic memory in patients with TLE and supports the theory of declarative memory of the hippocampus. Functional neuroimaging studies show an inefficient compensatory functional reorganization of semantic networks and electrophysiological studies show a lack of N400 effect that could indicate that the deficit in semantic processing in patients with TLE could be due to a failure in the mechanisms of automatic access to lexicon.

The importance of being apt: metaphor comprehension in Alzheimer's disease

We investigated the effect of aptness in the comprehension of copular metaphors (e.g., Lawyers are sharks) by Alzheimer's Disease (AD) patients. Aptness is the extent to which the vehicle (e.g., shark) captures salient properties of the topic (e.g., lawyers). A group of AD patients provided interpretations for metaphors that varied both in aptness and familiarity. Compared to healthy controls, AD patients produced worse interpretations, but interpretation ability was related to a metaphor's aptness rather than to its familiarity level, and patients with superior abstraction ability produced better interpretations. Therefore, the ability to construct figurative interpretations for metaphors is not always diminished in AD patients nor is it dependent only on the novelty level of the expression. We show that Alzheimer's patients' capacity to build figurative interpretations for metaphors is related to both item variables, such as aptness, and participant variables, such as abstraction ability.

When pain memories are lost: a pilot study of semantic knowledge of pain in dementia

OBJECTIVE

It has been documented that pain in people with dementia is often under-reported and poorly detected. The reasons for this are not clearly defined. This project aimed to explore semantic concepts of pain in people with dementia and whether this is associated with clinical pain report.

DESIGN

Cohort study with nested cross-sectional analysis.

SETTING

Acute general hospital medical wards for older people.

SUBJECTS

People with dementia (N = 26) and control participants (N = 13).

METHODS

Two subtests of semantic memory for pain: (1) Identifying painful situations from a standardized range of pictures; (2) Describing the concept of pain. Participants also indicated whether they were in pain or not, were observed for pain (PAINAD scale) and completed the Wong-Baker FACES scale to indicate pain severity.

RESULTS

Compared with the control group, people with dementia were less able to identify painful situations and used fewer categories to define their concept of pain. In turn, the performance on these two measures was related to the reported presence and, albeit less strongly, to the reported severity of pain, indicating that a reduction in semantic memory for pain is associated with a decline in reported pain.

CONCLUSIONS

This study is the first to show that semantic memory for pain is diminished in dementia patients. When using clinical pain tools, clinicians should consider these effects which may bias clinical pain ratings when they evaluate and manage pain in these patients. This might improve the recognition and management of pain in people with dementia.

Aphasia(s) in Alzheimer

Language disorders of degenerative origin are frequently tied to Alzheimer disease (AD) the different variants of which can result in primary and secondary aphasia syndromes. More specifically, Alzheimer pathology can primarily erode frontal, temporal or parietal language cortices resulting in three genuine AD language variants which account for about 30% of primary degenerative aphasias. Likewise, it can spread from non-language to language cortices leading to secondary language disorders like in typical amnesic AD and in several atypical AD variants. This paper reviews the whole set of AD variants by characterising their impact on the neural language system and on linguistic functioning. It also provides cues for diagnostic strategies which are essential for linguistic, syndromic and nosological patient classification, for adequate clinical follow-up and for guiding language rehabilitation. Such diagnostic approaches, founded on detailed linguistic phenotyping while integrating anatomical and neuropathological findings, also represent a crucial issue for future drug trials targeting the physio-pathological processes in degenerative aphasias.