The Word Processing Deficit in Semantic Dementia: All Categories Are Equal, but Some Categories Are More Equal than Others

It has been claimed that semantic dementia (SD), the temporal variant of fronto-temporal dementia, is characterized by an across-the-board deficit affecting all types of conceptual knowledge. We here confirm this generalized deficit but also report differential degrees of impairment in processing specific semantic word categories in a case series of SD patients (N = 11). Within the domain of words with strong visually grounded meaning, the patients' lexical decision accuracy was more impaired for color-related than for form-related words. Likewise, within the domain of action verbs, the patients' performance was worse for words referring to face movements and speech acts than for words semantically linked to actions performed with the hand and arm. Psycholinguistic properties were matched between the stimulus groups entering these contrasts; an explanation for the differential degrees of impairment must therefore involve semantic features of the words in the different conditions. Furthermore, this specific pattern of deficits cannot be captured by classic category distinctions such as nouns versus verbs or living versus nonliving things. Evidence from previous neuroimaging research indicates that color- and face/speech-related words, respectively, draw most heavily on anterior-temporal and inferior-frontal areas, the structures most affected in SD. Our account combines (a) the notion of an anterior-temporal amodal semantic “hub” to explain the profound across-the-board deficit in SD word processing, with (b) a semantic topography model of category-specific circuits whose cortical distributions reflect semantic features of the words and concepts represented.

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Elucidating the Nature of Deregulated Semantic Cognition in Semantic Aphasia: Evidence for the Roles of Prefrontal and Temporo-parietal Cortices

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2009.21289 ◽

2010 ◽

Vol 22 (7) ◽

pp. 1597-1613 ◽

Cited By ~ 130

Author(s):

Krist A. Noonan ◽

Elizabeth Jefferies ◽

Faye Corbett ◽

Matthew A. Lambon Ralph

Keyword(s):

Executive Control ◽

Conceptual Knowledge ◽

Critical Role ◽

Case Series ◽

Semantic Knowledge ◽

Semantic Dementia ◽

Semantic Cognition ◽

On Line ◽

Parietal Cortices ◽

Semantic Impairment

Semantic cognition—semantically driven verbal and nonverbal behavior—is composed of at least two interactive principal components: conceptual representations and executive control processes that regulate and shape activation within the semantic system. Previous studies indicate that semantic dementia follows from a progressive yet specific degradation of conceptual knowledge. In contrast, multimodal semantic impairment in aphasic patients (semantic aphasia [SA]) reflects damage to the control component of semantic cognition [Jefferies, E., & Lambon Ralph, M. A. Semantic impairment in stroke aphasia versus semantic dementia: A case-series comparison. Brain, 129, 2132–2147, 2006]. The purpose of the present study was to examine the nature of the semantic control deficits in SA in detail for the first time. Seven patients with SA were tested on four comprehension and naming tasks that directly manipulated the requirement for executive control in different ways. In line with many theories of cognitive control, the SA patients demonstrated three core features of impaired control: (i) they exhibited poor on-line manipulation and exploration of semantic knowledge; (ii) they exhibited poor inhibition of strongly associated distractors; and (iii) they exhibited reduced ability to focus on or augment less dominant aspects of semantic information, although the knowledge itself remained and could be successfully cued by external constraints provided by the examiner. Our findings are consistent with the notion that the anterior temporal lobes are crucial for conceptual knowledge whereas the left prefrontal and temporo-parietal cortices, damaged in patients with SA, play a critical role in regulating semantic activation in a task-appropriate fashion.

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Timecourse and convergence of abstract and concrete knowledge in the anterior temporal lobe

10.1101/2020.06.04.134163 ◽

2020 ◽

Author(s):

L. Vignali ◽

Y. Xu ◽

J. Turini ◽

O. Collignon ◽

D. Crepaldi ◽

...

Keyword(s):

Temporal Lobe ◽

Conceptual Knowledge ◽

Word Processing ◽

Semantic Information ◽

Anterior Temporal Lobe ◽

Conceptual Processing ◽

Feature Spaces ◽

Semantic Hub ◽

Late Stages ◽

The Brain

AbstractHow is conceptual knowledge organized and retrieved by the brain? Recent evidence points to the anterior temporal lobe (ATL) as a crucial semantic hub integrating both abstract and concrete conceptual features according to a dorsal-to-medial gradient. It is however unclear when this conceptual gradient emerges and how semantic information reaches the ATL during conceptual retrieval. Here we used a multiple regression approach to magnetoencephalography signals of spoken words, combined with dimensionality reduction in concrete and abstract semantic feature spaces. Results showed that the dorsal-to-medial abstract-to-concrete ATL gradient emerges only in late stages of word processing: Abstract and concrete semantic information are initially encoded in posterior temporal regions and travel along separate cortical pathways eventually converging in the ATL. The present finding sheds light on the neural dynamics of conceptual processing that shape the organization of knowledge in the anterior temporal lobe.

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SEMANTIC DEMENTIA WITH CATEGORY SPECIFICITY:ACOMPARATIVE CASE-SERIES STUDY

Cognitive Neuropsychology ◽

10.1080/02643290244000301 ◽

2003 ◽

Vol 20 (3-6) ◽

pp. 307-326 ◽

Cited By ~ 61

Author(s):

Matthew A. Lambon Ralph ◽

Karalyn Patterson ◽

Peter Garrard ◽

John R. Hodges

Keyword(s):

Case Series ◽

Semantic Dementia ◽

Case Series Study ◽

Series Study

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Issues in Neurolinguistic Studies of Morphology

Oxford Research Encyclopedia of Linguistics ◽

10.1093/acrefore/9780199384655.013.599 ◽

2019 ◽

Author(s):

Robert Fiorentino

Keyword(s):

Word Processing ◽

Time Course ◽

Lexical Processing ◽

Temporal Dynamics ◽

Basic Unit ◽

Semantic Features ◽

Form Complex ◽

Complex Word ◽

Complex Words ◽

The Brain

Research in neurolinguistics examines how language is organized and processed in the human brain. The findings from neurolinguistic studies on language can inform our understanding of the basic ingredients of language and the operations they undergo. In the domain of the lexicon, a major debate concerns whether and to what extent the morpheme serves as a basic unit of linguistic representation, and in turn whether and under what circumstances the processing of morphologically complex words involves operations that identify, activate, and combine morpheme-level representations during lexical processing. Alternative models positing some role for morphemes argue that complex words are processed via morphological decomposition and composition in the general case (full-decomposition models), or only under certain circumstances (dual-route models), while other models do not posit a role for morphemes (non-morphological models), instead arguing that complex words are related to their constituents not via morphological identity, but either via associations among whole-word representations or via similarity in formal and/or semantic features. Two main approaches to investigating the role of morphemes from a neurolinguistic perspective are neuropsychology, in which complex word processing is typically investigated in cases of brain insult or neurodegenerative disease, and brain imaging, which makes it possible to examine the temporal dynamics and neuroanatomy of complex word processing as it occurs in the brain. Neurolinguistic studies on morphology have examined whether the processing of complex words involves brain mechanisms that rapidly segment the input into potential morpheme constituents, how and under what circumstances morpheme representations are accessed from the lexicon, and how morphemes are combined to form complex morphosyntactic and morpho-semantic representations. Findings from this literature broadly converge in suggesting a role for morphemes in complex word processing, although questions remain regarding the precise time course by which morphemes are activated, the extent to which morpheme access is constrained by semantic or form properties, as well as regarding the brain mechanisms by which morphemes are ultimately combined into complex representations.

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Methylene Blue-Aided In Vivo Staining of Central Airways during Flexible Bronchoscopy

The Scientific World JOURNAL ◽

10.1100/2012/625867 ◽

2012 ◽

Vol 2012 ◽

pp. 1-4 ◽

Cited By ~ 2

Author(s):

Sabine Zirlik ◽

Kai M. Hildner ◽

Markus F. Neurath ◽

Florian S. Fuchs

Keyword(s):

Methylene Blue ◽

Case Series ◽

Specific Pattern ◽

Premalignant Lesions ◽

Histopathologic Examination ◽

Bronchial Mucosa ◽

Dye Staining ◽

Staining Techniques ◽

The Right

Background. The early diagnosis of malignant and premalignant changes of the bronchial mucosa remains a major challenge during bronchoscopy. Intravital staining techniques are not new. Previous small case series suggested that analysis of the bronchial mucosal surface using chromoendoscopy allows a prediction between neoplastic and nonneoplastic lesions.Objectives. The aim of the present study was to evaluate chromobronchoscopy as a method to identify malignant and premalignant lesions in the central airways in a prospective manner.Methods. In 26 patients we performed chromoendoscopy with 0.1% methylene blue during ongoing flexible white light bronchoscopy. Circumscribed lesions in central airways were further analyzed by biopsies and histopathologic examination.Results. In the majority of cases neither flat nor polypoid lesions in the central airways were stained by methylene blue. In particular, exophytic growth of lung cancer did not show any specific pattern in chromobronchoscopy. However, a specific dye staining was detected in one case where exophytic growth of metastatic colorectal cancer was present in the right upper lobe. In two other cases, a circumscribed staining was noted in unsuspicious mucosa. But histology revealed inflammation only.Conclusions. In contrast to previous studies, the present findings clearly indicate that chromobronchoscopy is not useful for early detection of malignant or premalignant lesions of the central airways.

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Semantic dementia: Brazilian study of nineteen cases

Dementia & Neuropsychologia ◽

10.1590/s1980-57642008dn10400007 ◽

2007 ◽

Vol 1 (4) ◽

pp. 366-373 ◽

Cited By ~ 3

Author(s):

Mirna Lie Hosogi Senaha ◽

Paulo Caramelli ◽

Claudia Sellitto Porto ◽

Ricardo Nitrini

Keyword(s):

Semantic Memory ◽

Temporal Lobe ◽

Clinical Characteristics ◽

Case Series ◽

Semantic Dementia ◽

Brazilian Sample ◽

Dementia Syndrome ◽

Visuospatial Skills ◽

Low Performance ◽

Lobe Atrophy

Abstract The term semantic dementia was devised by Snowden et al. in 1989 and nowadays, the semantic dementia syndrome is recognized as one of the clinical forms of frontotemporal lobar degeneration (FTLD) and is characterized by a language semantic disturbance associated to non-verbal semantic memory impairment. Objectives: The aim of this study was to describe a Brazilian sample of 19 semantic dementia cases, emphasizing the clinical characteristics important for differential diagnosis of this syndrome. Methods: Nineteen cases with semantic dementia were evaluated between 1999 and 2007. All patients were submitted to neurological evaluation, neuroimaging exams and cognitive, language and semantic memory evaluation. Results: All patients presented fluent spontaneous speech, preservation of syntactic and phonological aspects of the language, word-finding difficulty, semantic paraphasias, word comprehension impairment, low performance in visual confrontation naming tasks, impairment on tests of non-verbal semantic memory and preservation of autobiographical memory and visuospatial skills. Regarding radiological investigations, temporal lobe atrophy and/or hypoperfusion were found in all patients. Conclusions: The cognitive, linguistic and of neuroimaging data in our case series corroborate other studies showing that semantic dementia constitutes a syndrome with well defined clinical characteristics associated to temporal lobe atrophy.

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