Semantic dementia

Hodges, John R.; Davies, Rhys; Patterson, Karalyn

doi:10.1017/cbo9780511581410.018

Cited by 16 publications

(20 citation statements)

References 81 publications

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“…Instead, word recognition is assumed to rely on a common cognitive system where lexical and semantic knowledge interdependently and concurrently influence word recognition (Dilkina et al, 2008, 2010). Indeed, this view meshes well with the literature on semantic dementia, a variant of frontotemporal lobe dementia marked by deficits in conceptual and lexical knowledge (see Hodges et al, 1998, for a review). Although the finer details of this literature are beyond the scope of the present report, there is broad support for a positive correlation between lexical and conceptual deficits in semantic dementia patients, which is consistent with a single system that mediates both lexical and semantic processing (see Dilkina et al, 2010, for a connectionist model of lexical/semantic processing that explains the patient data).…”

supporting

confidence: 81%

An Abundance of Riches: Cross-Task Comparisons of Semantic Richness Effects in Visual Word Recognition

Yap¹,

Pexman²,

Wellsby³

et al. 2012

Front. Hum. Neurosci.

129

162

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There is considerable evidence (e.g., Pexman et al., 2008) that semantically rich words, which are associated with relatively more semantic information, are recognized faster across different lexical processing tasks. The present study extends this earlier work by providing the most comprehensive evaluation to date of semantic richness effects on visual word recognition performance. Specifically, using mixed effects analyses to control for the influence of correlated lexical variables, we considered the impact of number of features, number of senses, semantic neighborhood density, imageability, and body–object interaction across five visual word recognition tasks: standard lexical decision, go/no-go lexical decision, speeded pronunciation, progressive demasking, and semantic classification. Semantic richness effects could be reliably detected in all tasks of lexical processing, indicating that semantic representations, particularly their imaginal and featural aspects, play a fundamental role in visual word recognition. However, there was also evidence that the strength of certain richness effects could be flexibly and adaptively modulated by task demands, consistent with an intriguing interplay between task-specific mechanisms and differentiated semantic processing.

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supporting

confidence: 81%

An Abundance of Riches: Cross-Task Comparisons of Semantic Richness Effects in Visual Word Recognition

Yap¹,

Pexman²,

Wellsby³

et al. 2012

Front. Hum. Neurosci.

129

162

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“…The latter is also known as semantic dementia as the primary deficit is a profound loss of conceptual knowledge underlying their anomia and progressive loss of verbal and non-verbal comprehension. Patients with semantic dementia have striking focal temporal lobe atrophy19 and the range of pathological findings are identical to that found in patients with fv FTD 1415 The literature on semantic dementia has focused predominantly on the cognitive and linguistic features, but a recent study suggested that changes in behaviour and personality are also common 20…”

mentioning

confidence: 89%

Which neuropsychiatric and behavioural features distinguish frontal and temporal variants of frontotemporal dementia from Alzheimer's disease?

Bozeat

Gregory²,

Ralph³

et al. 2000

Journal of Neurology, Neurosurgery &Amp; Psychiatry

576

470

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Objectives-To investigate the prevalence of changes in mood, personality, and behaviour in frontotemporal dementia (FTD) and Alzheimer's disease (AD) and hence, which features reliably distinguish between them. To establish whether the frontal and temporal variants of FTD are characterised by diVerent behavioural changes. Methods-A questionnaire was designed to assess a wide range of neuropsychiatric changes; it incorporated features reported in previous studies of FTD and components of the neuropsychiatric inventory. Results-Factor analysis showed four robust and meaningful symptom clusters: factor 1-stereotypic and eating behaviour; factor 2-executive dysfunction and self care; factor 3-mood changes; factor 4-loss of social awareness. Only stereotypic and altered eating behaviour and loss of social awareness reliably diVerentiated AD from FTD with no eVect of disease severity. By contrast, executive dysfunction, poor self care, and restlessness showed a significant eVect of disease severity only, with the more impaired patients scoring more highly. Changes in mood were found to be equally prevalent in the three patient groups. Analysis of individual symptoms showed increased rates of mental rigidity and depression in the patients with semantic dementia compared with those with fv FTD. Conversely, the latter group showed greater disinhibition. Discriminant function analysis correctly classified 71.4% overall and 86.5% of the patients with AD. Conclusions-This questionnaire disclosed striking diVerences between patients with FTD and AD, but only stereotypic behaviour, changes in eating preference, disinhibition, and features of poor social awareness reliably separated the groups. The patients with fv FTD and semantic dementia were behaviourally very similar, reflecting the involvement of a common network, the ventral frontal lobe, temporal pole, and amygdala. Dysexecutive symptoms and poor self care were found to be aVected by the severity of the disease, reflecting perhaps spread to dorsolateral prefrontal areas relatively late in the course of both FTD and AD. This questionnaire may be of value in the diagnosis and the monitoring of therapies.

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“…This model has been critiqued for its reliance on findings from patients with semantic dementia. This type of dementia is characterized by cell loss in the ATLs; however, patients also have both gray and white matter atrophy throughout the brain, making it difficult to claim that deficits are solely the result of damage to the ATLs (Garrard & Hodges, 2000; Hodges, Patterson, Oxbury, & Funnell, 1992; Patterson, Nestor, & Rogers, 2007). There is also conflicting evidence from individuals with focal lesions in the ATLs, who in stark contrast to the findings from individuals with semantic dementia (who have widespread degeneration), have semantic knowledge that is largely unimpaired (Bi et al, 2011; Simmons & Martin, 2009).…”

Section: Introductionmentioning

confidence: 99%

Individual differences in white matter microstructure predict semantic control

Nugiel

Alm

Olson

2016

Cogn Affect Behav Neurosci

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In everyday conversation, we make many rapid choices between competing concepts and words in order to convey our intent. This process is termed semantic control, and it is thought to rely on information transmission between a distributed semantic store in the temporal lobes and a more discrete region, optimized for retrieval and selection, in the left inferior frontal gyrus. Here, we used diffusion tensor imaging in a group of neurologically normal young adults to investigate the relationship between semantic control and white matter tracts that have been implicated in semantic memory retrieval. Participants completed a verb generation task that taps semantic control (Snyder & Munakata, 2008; Snyder et al., 2010) and underwent a diffusion imaging scan. Deterministic tractography was performed to compute indices representing the microstructural properties of the inferior fronto-occipital fasciculus (IFOF), the uncinate fasciculus (UF), and the inferior longitudinal fasciculus (ILF). Microstructural measures of the UF failed to predict semantic control performance. However, there was a significant relationship between microstructure of the left IFOF and ILF and individual differences in semantic control. Our findings support the view put forth by Duffau (2013) that the IFOF is a key structural pathway in semantic retrieval.

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Semantic dementia

Cited by 16 publications

References 81 publications

An Abundance of Riches: Cross-Task Comparisons of Semantic Richness Effects in Visual Word Recognition

An Abundance of Riches: Cross-Task Comparisons of Semantic Richness Effects in Visual Word Recognition

Which neuropsychiatric and behavioural features distinguish frontal and temporal variants of frontotemporal dementia from Alzheimer's disease?

Individual differences in white matter microstructure predict semantic control

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