Regular ArticleNaming and Knowing in Dementia of Alzheimer's Type
Abstract
We studied the relationship between naming and the integrity of physical and associative knowledge in a group of patients with dementia of the Alzheimer type (DAT) and matched normal controls. All subjects named 48 line drawings and later generated verbal definitions in response to the names of a subset of the 48 items, which included a minimum of six definitions for correctly named objects and six definitions for items that the subject failed to name. A comprehensive scoring system was designed for the definitions, including physical and associative features of a general and a specific type, a superordinate label, the core concept, and various categories of errors. The definitions generated by the DAT patients, even those in the minimal group, contained significantly less correct information than those of normal subjects, and definitions corresponding to unnamed items were more impoverished than those for named items. Particularly striking was the loss of core concept for unnamed items. There was also a disproportionate reduction in physical information on unnamed compared to named items. We conclude that quantitative assessment of verbal definitions is a sensitive index of semantic memory breakdown. Our findings offer some support for the hypothesis that successful naming depends upon integrity of the subset of semantic knowledge comprising physical features.
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Perceptual strength influences lexical decision in Alzheimer's disease
2023, Journal of NeurolinguisticsThe multimodal approach where cognition is embodied in language, perceptual, motor, and emotional systems is a widely agreed theoretical framework for conceptual representations. However, the lack of work supporting this view of cognition in healthy and pathological aging stands in stark contrast with the ongoing need to understand the factors that uncover semantic degradation in brain pathologies. The aim of this study is to explore the impact of perceptual strength (PS) - i.e., the extent to which a word can be experienced by multiple sensory modalities - in visual word recognition in Alzheimer's disease (AD). Thirty-six healthy participants, 22 participants in the mild stage of AD (AD1) and 20 in the moderate stage (AD2) took part in a lexical decision task with two conditions: words with high vs low PS words. Results showed an interaction effect only between healthy controls and AD1 individuals, revealing that the latter were faster in processing high PS words in contrast to low PS words, while this was not the case for healthy individuals. Furthermore, it was specifically the ratings of the neuropsychological executive and lexical-semantic assessments that predicted these results. However, no results were observed for AD2 participants, suggesting that lexical-semantic degradation was too severe to reveal a PS effect. This study demonstrates the importance of considering the perceptual dimension when examining the conceptual system and opens up new avenues in the exploration of semantic impairment in AD.
Dissociating nouns and verbs in temporal and perisylvian networks: Evidence from neurodegenerative diseases
2021, CortexNaming of nouns and verbs can be selectively impaired in neurological disorders, but the specificity of the neural and cognitive correlates of such dissociation remains unclear. Functional imaging and stroke research sought to identify cortical regions selectively recruited for nouns versus verbs, yet findings are inconsistent.
The present study investigated this issue in neurodegenerative diseases known to selectively affect different brain networks, thus providing new critical evidence of network specificity. We examined naming performances on nouns and verbs in 146 patients with different neurodegenerative syndromes (Primary Progressive Aphasia – PPA, Alzheimer's disease – AD, and behavioral variant Frontotemporal Dementia – FTD) and 30 healthy adults. We then correlated naming scores with MRI-derived cortical thickness values as well as with performances in semantic and syntactic tasks, across all subjects.
Results indicated that patients with the semantic variant PPA named significantly fewer nouns than verbs. Instead, nonfluent/agrammatic PPA patients named fewer verbs than nouns. Across all subjects, performance on nouns (adjusted for verbs) specifically correlated with cortical atrophy in left anterior temporal regions, and performance on verbs (adjusted for nouns) with atrophy in left inferior and middle frontal, inferior parietal and posterior temporal regions. Furthermore, lower lexical-semantic abilities correlated with deficits in naming both nouns and verbs, while lower syntactic abilities only correlated with naming verbs.
Our results show that different neural and cognitive mechanisms underlie naming of specific grammatical categories in neurodegenerative diseases. Importantly, our findings showed that verb processing depends on a widespread perisylvian networks, suggesting that some regions might be involved in processing different types of action knowledge. These findings have important implications for early differential diagnosis of neurodegenerative disorders.
Words differ in the complexity of their semantic representations and their relationships to other words and these differences can be operationalised as a variety of semantic variables. The research presented here investigates how word production in aphasia is influenced by six feature-based semantic variables (number of near semantic neighbours, semantic similarity, number of semantic features, typicality, intercorrelational density, and distinctiveness). Previous research has reported inconsistent findings for some of the semantic variables, while others have not been previously studied in aphasia. Spoken picture naming data from a large group of individuals with aphasia with mixed spoken word production impairments (n = 175) and a sub-group who produced few phonological errors (n = 60) was analysed. We examined effects of the semantic variables on overall naming accuracy and on the occurrence of different error types (semantic errors overall, coordinate errors, omissions), while controlling for other psycholinguistic variables using generalised linear mixed effects models and Bayesian correlations. Across analyses, number of semantic features was the most important predictor with a facilitatory main effect on naming accuracy in the sub-group analysis. Number of semantic features, along with typicality and semantic similarity, also predicted error types and in some analyses these effects depended on the integrity of semantic processing. Effects of the semantic variables and their theoretical explanations and implications are discussed in light of previous research and models of word production.
Language deterioration in bilingual Alzheimer's disease patients: A longitudinal study
2017, Journal of NeurolinguisticsIn the context of bilingual research, little is known about the effects of neurodegenerative disorders (NDs) on the processing of two languages in a bilingual. In a recent cross-sectional study, we showed that Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) had similar effects on lexico-semantic processes in the two languages of highly proficient bilinguals (Costa et al., Neuropsychologia, 2012, 50, 740–53). In the present longitudinal study, we extend this finding by looking at the pattern of language deterioration over time in the same population of Catalan-Spanish bilingual patients. All the participants completed three language-processing tasks (picture naming, word translation and word comprehension), both in their dominant (L1) and non-dominant (L2) language. At one year, the final group was made up of 50 patients: 15 with MCI and 35 with AD. For AD but not MCI, the language deterioration over time was the same in both languages, as previously reported in the cross-sectional study. The results are discussed in the frame of the hypothesis of shared lexico-semantic processing in highly proficient bilinguals and the influence of executive control deficits in language production.
The majority of logopenic variant primary progressive aphasia (lv-PPA) cases harbour Alzheimer pathology, suggesting that lv-PPA constitutes an atypical presentation of Alzheimer's disease (AD). However, even if caused by Alzheimer pathology, the clinical manifestations of lv-PPA differ from those observed in the typical or amnestic AD presentation: in lv-PPA, aphasia is the main feature while amnestic AD is characterised by impaired episodic memory. Anomia or impaired naming, however, is present in both AD presentations. Whether these presentations share anatomical and mechanistic processes of anomia has not been fully investigated. Accordingly, we studied naming performance and its relationship with regions of brain atrophy in 23 amnestic AD and 22 lv-PPA cases with presumed underlying Alzheimer pathology. Both AD groups displayed some degree of anomia and impaired word comprehension but these were particularly severe in lv-PPA and accompanied by a range of linguistic deficits, comprising phonological substitutions, superordinate semantic paraphasias and abnormal single-word repetition. Analysis of cortical thickness revealed that anomia was correlated with thinning in left superior temporal gyrus in both groups. In amnestic AD, however, anomia was also associated with thinning in right inferior temporal regions. Single-word comprehension (SWC), by contrast, was associated with cortical thinning involving bilateral fusiform gyri in both groups. These findings suggest that anomia in both amnestic AD and lv-PPA results from the involvement at multiple steps of word processing, in particular, semantic and lexical retrieval; in addition lv-PPA patients display a more marked involvement of phonological processing.
Selectivity in acquired prosopagnosia: The segregation of divergent and convergent operations
2016, NeuropsychologiaFace recognition can be viewed as part of a divergent set of operations in object recognition, in which information from common low-level visual mechanisms feeds forward into increasingly specialized processes for different object types. This divergence may also involve hemispheric specialization, notably for faces in the right and words in the left hemisphere. However, in person recognition, face processing is one of a set of sensory inputs that converge upon access to stored information about people. We review the literature and evidence from a cohort of acquired prosopagnosic subjects, on three issues concerning selectivity. First, we review the data on object recognition in prosopagnosia, and recent evidence that, after adjusting for pre-morbid car expertise, impairments of car identification are common in our cohort, particularly among car experts. Second, we review the data on word processing in prosopagnosia. In our cohort we show that the word-length effect in single word reading is normal after right-sided lesions, but the discrimination of font and handwriting is impaired in most of our subjects, regardless of lesion location. Third, we discuss the status of voice recognition in prosopagnosia, and show that in our cohort, right anterior temporal lesions do not impair this function, but bilateral ones do. Together, these findings suggest that the processes for faces, cars and visual text involve either the same neural resources or parallel processes in close proximity. Voice and face processing remain distinct in our subjects, and confirm that right anterior temporal lesions cause an associative prosopagnosia rather than a multi-modal person recognition syndrome.