Conceptual apraxia and semantic memory deficit in Alzheimer's 
disease: Two sides of the same coin?

This study was designed to examine the patterns of apraxic disturbances and the relationships between action knowledge and other measures of semantic knowledge about objects in 10 well-characterized Alzheimer's disease (AD) patients. Five tasks were used to assess components of action knowledge (action–tool relationships, pantomime recognition, and sequential organization of action) and praxis execution (actual use, pantomiming) according to the cognitive model of praxis. Three tasks (verbal comprehension, naming, and a visual semantic matching task) were used to assess verbal–visual semantics. Considering patterns of apraxia first, conceptual apraxia was found in 9 out of the 10 AD patients, suggesting that it is a common feature even in the early stages of AD. Second, we found partly parallel deficits in tests of action-semantic and verbal–visual semantic knowledge in 9 AD patients. Impaired action knowledge was found only in patients with a semantic language deficit. These findings provide no evidence that “action semantics” may be separated from other semantic information. Our results support the view of a unitary semantic system, given that the representations of action-semantic and other semantic knowledge of objects are often simultaneously disrupted in AD. (JINS, 2000, 6, 693–703.)

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Anhedonia in Semantic Dementia—Exploring Right Hemispheric Contributions to the Loss of Pleasure

Brain Sciences ◽

10.3390/brainsci11080998 ◽

2021 ◽

Vol 11 (8) ◽

pp. 998

Author(s):

Siobhán R. Shaw ◽

Hashim El-Omar ◽

Siddharth Ramanan ◽

Olivier Piguet ◽

Rebekah M. Ahmed ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Temporal Lobe ◽

Rating Scale ◽

Right Hemisphere ◽

Semantic Knowledge ◽

Semantic Dementia ◽

Anterior Cingulate ◽

Functional Impairments ◽

Lobe Atrophy

Semantic dementia (SD) is a younger-onset neurodegenerative disease characterised by progressive deterioration of the semantic knowledge base in the context of predominantly left-lateralised anterior temporal lobe (ATL) atrophy. Mounting evidence indicates the emergence of florid socioemotional changes in SD as atrophy encroaches into right temporal regions. How lateralisation of temporal lobe pathology impacts the hedonic experience in SD remains largely unknown yet has important implications for understanding socioemotional and functional impairments in this syndrome. Here, we explored how lateralisation of temporal lobe atrophy impacts anhedonia severity on the Snaith–Hamilton Pleasure Scale in 28 SD patients presenting with variable right- (SD-R) and left-predominant (SD-L) profiles of temporal lobe atrophy compared to that of 30 participants with Alzheimer’s disease and 30 healthy older Control participants. Relative to Controls, SD-R but not SD-L or Alzheimer’s patients showed clinically significant anhedonia, representing a clear departure from premorbid levels. Overall, anhedonia was more strongly associated with functional impairment on the Frontotemporal Dementia Functional Rating Scale and motivational changes on the Cambridge Behavioural Inventory in SD than in Alzheimer’s disease patients. Voxel-based morphometry analyses revealed that anhedonia severity correlated with reduced grey matter intensity in a restricted set of regions centred on right orbitofrontal and temporopolar cortices, bilateral posterior temporal cortices, as well as the anterior cingulate gyrus and parahippocampal gyrus, bilaterally. Finally, regression and mediation analysis indicated a unique role for right temporal lobe structures in modulating anhedonia in SD. Our findings suggest that degeneration of predominantly right-hemisphere structures deleteriously impacts the capacity to experience pleasure in SD. These findings offer important insights into hemispheric lateralisation of motivational disturbances in dementia and suggest that anhedonia may emerge at different timescales in the SD disease trajectory depending on the integrity of the right hemisphere.

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Semantic Processing in Healthy Aging and Alzheimer’s Disease: A Systematic Review of the N400 Differences

Brain Sciences ◽

10.3390/brainsci10110770 ◽

2020 ◽

Vol 10 (11) ◽

pp. 770

Author(s):

Marilyne Joyal ◽

Charles Groleau ◽

Clara Bouchard ◽

Maximiliano A. Wilson ◽

Shirley Fecteau

Keyword(s):

Systematic Review ◽

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Semantic Processing ◽

Healthy Aging ◽

Semantic Knowledge ◽

Event Related Potential ◽

N400 Effect ◽

Pathological Aging ◽

Healthy Elderly

Semantic deficits are common in individuals with Alzheimer’s disease (AD). These deficits notably impact the ability to understand words. In healthy aging, semantic knowledge increases but semantic processing (i.e., the ability to use this knowledge) may be impaired. This systematic review aimed to investigate semantic processing in healthy aging and AD through behavioral responses and the N400 brain event-related potential. The results of the quantitative and qualitative analyses suggested an overall decrease in accuracy and increase in response times in healthy elderly as compared to young adults, as well as in individuals with AD as compared to age-matched controls. The influence of semantic association, as measured by N400 effect amplitudes, appears smaller in healthy aging and even more so in AD patients. Thus, semantic processing differences may occur in both healthy and pathological aging. The establishment of norms of healthy aging for these outcomes that vary between normal and pathological aging could eventually help early detection of AD.

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Semantic Knowledge of Famous People in Mild Cognitive Impairment and Progression to Alzheimer’s Disease

Dementia and Geriatric Cognitive Disorders ◽

10.1159/000076355 ◽

2004 ◽

Vol 17 (3) ◽

pp. 188-195 ◽

Cited By ~ 52

Author(s):

Armando Estévez-González ◽

Carmen García-Sánchez ◽

Anunciación Boltes ◽

Pilar Otermín ◽

Berta Pascual-Sedano ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Cognitive Impairment ◽

Mild Cognitive Impairment ◽

Semantic Knowledge ◽

Famous People

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Cognition in Alzheimer's disease: disorders of attention and semantic knowledge

Current Opinion in Neurobiology ◽

10.1016/0959-4388(94)90079-5 ◽

1994 ◽

Vol 4 (2) ◽

pp. 237-244 ◽

Cited By ~ 27

Author(s):

R Parasuraman

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Semantic Knowledge

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Impaired semantic knowledge underlies the reduced verbal short-term storage capacity in Alzheimer's disease

Neuropsychologia ◽

10.1016/j.neuropsychologia.2009.07.002 ◽

2009 ◽

Vol 47 (14) ◽

pp. 3067-3073 ◽

Cited By ~ 14

Author(s):

Frédéric Peters ◽

Steve Majerus ◽

Julie De Baerdemaeker ◽

Eric Salmon ◽

Fabienne Collette

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Storage Capacity ◽

Semantic Knowledge ◽

Short Term ◽

Short Term Storage ◽

Term Storage

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Reading lexically without semantics: Evidence from patients with probable Alzheimer's disease

Journal of the International Neuropsychological Society ◽

10.1017/s1355617700001363 ◽

1996 ◽

Vol 2 (4) ◽

pp. 340-349 ◽

Cited By ~ 13

Author(s):

Anastasia M. Raymer ◽

Rita Sloan Berndt

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Oral Reading ◽

Word Reading ◽

Semantic Knowledge ◽

Read Aloud ◽

Reading Processes ◽

Neurologically Normal ◽

Semantic Mediation ◽

Semantic Impairment

AbstractRecent modifications of the lexical model of oral reading make the prediction that under conditions where sublexical reading processes alone cannot achieve the target pronunciation (i.e., when words have exceptional spellings or when sublexical processes are impaired), patients with severe semantic impairment should have more difficulty reading aloud semantically impaired words than semantically retained words. In a battery of lexical-semantic and reading tasks, two neurologically normal control subjects and two subjects with probable Alzheimer's disease (AD) and only moderate semantic impairment read aloud all words accurately. One AD subject with severe semantic impairment was impaired in word reading but demonstrated no difference in reading words with regular and exceptional spellings. Another AD subject with severe semantic impairment read aloud without error virtually all regular and exception words. Neither severely impaired AD subject demonstrated any relationship between oral reading accuracy and semantic knowledge of exception words. These findings support a model of word reading incorporating lexical, nonsemantic processes by which lexical orthographic input representations directly activate lexical phonological output representations without the necessity of semantic mediation. (JINS, 1996, 2, 340–349.)

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