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John R Hodges - One of the best experts on this subject based on the ideXlab platform.
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an update on Semantic Dementia genetics imaging and pathology
Alzheimer's Research & Therapy, 2016Co-Authors: John R Hodges, Fiona Kumfor, Ramon Landinromero, Rachel TanAbstract:Progressive and relatively circumscribed loss of Semantic knowledge, referred to as Semantic Dementia (SD) which falls under the broader umbrella of frontotemporal Dementia, was officially identified as a clinical syndrome less than 50 years ago. Here, we review recent neuroimaging, pathological, and genetic research in SD. From a neuroimaging perspective, SD is characterised by hallmark asymmetrical atrophy of the anterior temporal pole and anterior fusiform gyrus, which is usually left lateralised. Functional magnetic resonance imaging (fMRI) studies have revealed widespread changes in connectivity, implicating the anterior temporal regions in Semantic deficits in SD. Task-related fMRI have also demonstrated the relative preservation of frontal and parietal regions alongside preserved memory performance. In addition, recent longitudinal studies have demonstrated that, with disease progression, atrophy encroaches into the contralateral temporal pole and medial prefrontal cortices, which reflects emerging changes in behaviour and social cognition. Notably, unlike other frontotemporal Dementia subtypes, recent research has demonstrated strong clinicopathological concordance in SD, with TDP43 type C as the most common pathological subtype. Moreover, an underlying genetic cause appears to be relatively rare in SD, with the majority of cases having a sporadic form of the disease. The relatively clear diagnosis, clinical course, and pathological homogeneity of SD make this syndrome a promising target for novel disease-modifying interventions. The development of neuroimaging markers of disease progression at the individual level is an important area of research for future studies to address, in order to assist with this endeavour.
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on the right side a longitudinal study of left versus right lateralized Semantic Dementia
Brain, 2016Co-Authors: John R Hodges, Fiona Kumfor, Ramon Landinromero, Emma Devenney, Rosalind Hutchings, Roberto GrassoAbstract:The typical presentation of Semantic Dementia is associated with marked, left predominant anterior temporal lobe atrophy and with changes in language. About 30% of individuals, however, present with predominant right anterior temporal lobe atrophy, usually accompanied by behavioural changes and prosopagnosia. Here, we aimed to establish whether these initially distinct clinical presentations evolve into a similar syndrome at the neural and behavioural level. Thirty-one patients who presented with predominant anterior temporal lobe atrophy were included. Based on imaging, patients were categorized as either predominant left (n = 22) or right (n = 9) Semantic Dementia. Thirty-three Alzheimer's disease patients and 25 healthy controls were included for comparison. Participants completed the Addenbrooke's Cognitive Examination, a Face and Emotion Processing Battery and the Cambridge Behavioural Inventory, and underwent magnetic resonance imaging annually. Longitudinal neuroimaging analyses showed greater right temporal pole atrophy in left Semantic Dementia than Alzheimer's disease, whereas right Semantic Dementia showed greater orbitofrontal and left temporal lobe atrophy than Alzheimer's disease. Importantly, direct comparisons between Semantic Dementia groups revealed that over time, left Semantic Dementia showed progressive thinning in the right temporal pole, whereas right Semantic Dementia showed thinning in the orbitofrontal cortex and anterior cingulate. Behaviourally, longitudinal analyses revealed that general cognition declined in all patients. In contrast, patients with left and right Semantic Dementia showed greater emotion recognition decline than Alzheimer's disease. In addition, left Semantic Dementia showed greater motivation loss than Alzheimer's disease. Correlational analyses revealed that emotion recognition was associated with right temporal pole, right medial orbitofrontal and right fusiform integrity, while changes in motivation were associated with right temporal pole cortical thinning. While left and right Semantic Dementia show distinct profiles at presentation, both phenotypes develop deficits in emotion recognition and behaviour. These findings highlight the pervasive socio-emotional deficits in frontotemporal Dementia, even in patients with an initial language presentation. These changes reflect right anterior temporal and orbitofrontal cortex degeneration, underscoring the role of these regions in social cognition and behaviour.
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cognitive intervention in Semantic Dementia maintaining words over time
Alzheimer Disease & Associated Disorders, 2015Co-Authors: Sharon Savage, Olivier Piguet, John R HodgesAbstract:Patients with Semantic Dementia (SD) can improve their naming ability through cognitive intervention, with good retention 1 month later. Beyond this time, improvements often fade, yet no studies have investigated how to maintain performance. Nine SD patients completed a 2-month word training program and were then monitored over 6 months: firstly for 2 months without training, followed by a further 4 months, where additional training was provided to revise words, if required. All patients improved their naming immediately postintervention (P<0.001). After 2 months without practice, significant declines occurred in 4 patients. To sustain at least 80% of their postintervention performance 6 months later, 4 patients required minimal revision (<10 sessions over the period), 2 required regular weekly or biweekly revision sessions, with the remaining 3 patients requiring no revision sessions. During this period, group results indicated some decline in words that were initially known, but were not trained. Improvements in naming can be sustained in SD patients, with the support of less intense, but ongoing revision. Training words that are still known appears to help prolong memory of these words.
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right anterior temporal lobe dysfunction underlies theory of mind impairments in Semantic Dementia
Brain, 2014Co-Authors: Muireann Irish, John R Hodges, Olivier PiguetAbstract:Semantic Dementia is a progressive neurodegenerative disorder characterized by the amodal and profound loss of Semantic knowledge attributable to the degeneration of the left anterior temporal lobe. Although traditionally conceptualized as a language disorder, patients with Semantic Dementia display significant alterations in behaviour and socioemotional functioning. Recent evidence points to an impaired capacity for theory of mind in predominantly left-lateralized cases of Semantic Dementia; however, it remains unclear to what extent Semantic impairments contribute to these deficits. Further the neuroanatomical signature of such disturbance remains unknown. Here, we sought to determine the neural correlates of theory of mind performance in patients with left predominant Semantic Dementia ( n = 11), in contrast with disease-matched cases with behavioural-variant frontotemporal Dementia ( n = 10) and Alzheimer’s disease ( n = 10), and healthy older individuals ( n = 14) as control participants. Participants completed a simple cartoons task, in which they were required to describe physical and theory of mind scenarios. Irrespective of subscale, patients with Semantic Dementia exhibited marked impairments relative to control subjects; however, only theory of mind deficits persisted when we covaried for Semantic comprehension. Voxel-based morphometry analyses revealed that atrophy in right anterior temporal lobe structures, including the right temporal fusiform cortex, right inferior temporal gyrus, bilateral temporal poles and amygdalae, correlated significantly with theory of mind impairments in the Semantic Dementia group. Our results point to the marked disruption of cognitive functions beyond the language domain in Semantic Dementia, not exclusively attributable to Semantic processing impairments. The significant involvement of right anterior temporal structures suggests that with disease evolution, the encroachment of pathology into the contralateral hemisphere heralds the onset of social cognitive deficits in this syndrome. * Abbreviations : ACE-R : Addenbrooke’s Cognitive Examination-Revised FTD : frontotemporal Dementia ToM : theory of mind
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Right anterior temporal lobe dysfunction underlies theory of mind impairments in Semantic Dementia
Brain, 2014Co-Authors: Muireann Irish, John R HodgesAbstract:Semantic Dementia is a progressive neurodegenerative disorder characterized by the amodal and profound loss of Semantic knowledge attributable to the degeneration of the left anterior temporal lobe. Although traditionally conceptualized as a language disorder, patients with Semantic Dementia display significant alterations in behaviour and socioemotional functioning. Recent evidence points to an impaired capacity for theory of mind in predominantly left-lateralized cases of Semantic Dementia; however, it remains unclear to what extent Semantic impairments contribute to these deficits. Further the neuroanatomical signature of such disturbance remains unknown. Here, we sought to determine the neural correlates of theory of mind performance in patients with left predominant Semantic Dementia (n=11), in contrast with disease-matched cases with behavioural-variant frontotemporal Dementia (n=10) and Alzheimer's disease (n=10), and healthy older individuals (n=14) as control participants. Participants completed a simple cartoons task, in which they were required to describe physical and theory of mind scenarios. Irrespective of subscale, patients with Semantic Dementia exhibited marked impairments relative to control subjects; however, only theory of mind deficits persisted when we covaried for Semantic comprehension. Voxel-based morphometry analyses revealed that atrophy in right anterior temporal lobe structures, including the right temporal fusiform cortex, right inferior temporal gyrus, bilateral temporal poles and amygdalae, correlated significantly with theory of mind impairments in the Semantic Dementia group. Our results point to the marked disruption of cognitive functions beyond the language domain in Semantic Dementia, not exclusively attributable to Semantic processing impairments. The significant involvement of right anterior temporal structures suggests that with disease evolution, the encroachment of pathology into the contralateral hemisphere heralds the onset of social cognitive deficits in this syndrome.
Karalyn Patterson - One of the best experts on this subject based on the ideXlab platform.
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14 the language disorder in Semantic Dementia does it matter which language you speak
Journal of Neurology Neurosurgery and Psychiatry, 2019Co-Authors: Karalyn PattersonAbstract:From its inception, Karalyn Patterson has shaped the field of cognitive neuropsychology - the study of how the brain’s structure and function relates to mental processes concerning the generation and use of knowledge. Specifically, Karalyn has used the effects of brain disease and injury to improve our understanding of language and memory. Her approaches are varied and rigorous, combining computer modelling and structural and functional brain imaging with observations of behaviour in normal and brain-damaged adults, as well as those affected by certain brain diseases. This has allowed Karalyn to directly link particular structures in the brain with specific cognitive issues. Karalyn’s research has important consequences for our understanding of brain conditions that affect memory; for example, Alzheimer’s disease and other forms of Dementia. She has also revealed the impact of the same brain disorder on the speakers of two diverse languages, English and Japanese. Semantic Dementia (SD) is a neurodegenerative condition in the spectrum of frontotemporal Dementia, and considered to be one of the main varieties of primary progressive aphasia. The question in the title of this talk will be addressed from two different perspectives. The first asks whether the pattern of language features observed in SD varies in any principled and significant way across different languages. English and Japanese, for example, differ in almost every component of language – phonology, syntax, written form, etc; yet the profiles of language deficit in SD patients from these two language communities are virtually identical. From this perspective, therefore, the answer is no, it does not matter which language you speak. The second question asks whether the severity of the language disorder in SD varies in a principled and significant way across the two languages spoken by bilingual cases of SD. A high proportion of people living in India speak two or more languages. When bilingual Indian SD patients are given the same tests in their L1 and L2 languages, of course they are impaired in both, but they show a striking advantage for L1. Furthermore, and of substantial theoretical interest, the patients’ correct responses to test items in L2 are a virtually perfect subset of correct responses to the same test items in L1. From this perspective, therefore, the answer is yes, it does matter which language you are speaking. These contrasting answers to the two forms of the question follow from the following pair of hypotheses: (a) the language disorder in SD is a fairly pure reflection of a disintegrating Semantic system, and (b) the Semantic system is fundamentally language-independent. References Fushimi, T, Komori, K, Ikeda, M, Lambon Ralph, MA & Patterson, K. (2009). The association between Semantic Dementia and surface dyslexia in Japanese. Neuropsychologia. 2009;47:1061–1068. Patterson, K & Fushimi, T. Organisation of language in the brain: Does it matter which language you speak?Interdisciplinary Science Reviews2006;31:201–216 Ratnavalli, E, Narayana, J & Patterson, K(2019). Differential deterioration of languages in bilingual patients with Semantic Dementia: Implications for language representation in bilinguals. Under review.
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SD-Squared: On the Association Between Semantic Dementia
2015Co-Authors: Surface Dyslexia, David C. Plaut, Anna M. Woollams, Matthew Lambon A. Ralph, Karalyn PattersonAbstract:Within the connectionist triangle model of reading aloud, interaction between Semantic and phonological representations occurs for all words but is particularly important for correct pronunciation of lower frequency exception words. This framework therefore predicts that (a) Semantic Dementia, which compromises Semantic knowledge, should be accompanied by surface dyslexia, a frequency-modulated deficit in exception word reading, and (b) there should be a significant relationship between the severity of Semantic degradation and the severity of surface dyslexia. The authors evaluated these claims with reference to 100 observations of reading data from 51 cases of Semantic Dementia. Surface dyslexia was rampant, and a simple composite Semantic measure accounted for half of the variance in low-frequency exception word reading. Although in 3 cases initial testing revealed a moderate Semantic impairment but normal exception word reading, all of these became surface dyslexic as their Semantic knowledge deteriorated further. The connectionist account attributes such cases to premorbid individual variation in Semantic reliance for accurate exception word reading. These results provide a striking demonstration of the association between Semantic Dementia and surface dyslexia, a phenomenon that the authors have dubbed SD-squared
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ever decreasing circles speech production in Semantic Dementia
Cortex, 2014Co-Authors: Lotte Meteyard, Emma Quain, Karalyn PattersonAbstract:We explored the impact of a degraded Semantic system on lexical, morphological and syntactic complexity in language production. We analysed transcripts from connected speech samples from eight patients with Semantic Dementia (SD) and eight age-matched healthy speakers. The frequency distributions of nouns and verbs were compared for hand-scored data and data extracted using text-analysis software. Lexical measures showed the predicted pattern for nouns and verbs in hand-scored data, and for nouns in software-extracted data, with fewer low frequency items in the speech of the patients relative to controls. The distribution of complex morpho-syntactic forms for the SD group showed a reduced range, with fewer constructions that required multiple auxiliaries and inflections. Finally, the distribution of syntactic constructions also differed between groups, with a pattern that reflects the patients' characteristic anomia and constraints on morpho-syntactic complexity. The data are in line with previous findings of an absence of gross syntactic errors or violations in SD speech. Alterations in the distributions of morphology and syntax, however, support constraint satisfaction models of speech production in which there is no hard boundary between lexical retrieval and grammatical encoding.
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SD-squared 1 RUNNING HEAD: Semantic Dementia AND SURFACE DYSLEXIA SD-SQUARED: ON THE ASSOCIATION BETWEEN Semantic
2014Co-Authors: Surface Dyslexia, David C. Plaut, Anna M. Woollams, Matthew Lambon A. Ralph, Karalyn PattersonAbstract:Within the connectionist triangle model of reading aloud, interaction between Semantic and phonological representations occurs for all words but is particularly important for correct pronunciation of lower-frequency exception words. This framework therefore predicts that (a) Semantic Dementia, which compromises Semantic knowledge, should be accompanied by surface dyslexia, a frequencymodulated deficit in exception word reading; and (b) there should be a significant relationship between the severity of Semantic Dementia and of surface dyslexia. We evaluated these claims with reference to 100 observations of reading data from 51 cases of Semantic Dementia. Surface dyslexia was rampant, and a simple composite Semantic measure accounted for more than half of the variance in low-frequency exception word reading. These results provide a striking demonstration of the association between Semantic Dementia (SD) and surface dyslexia (SD), a phenomenon that we have dubbed SD-squared
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abnormalities of connected speech in Semantic Dementia vs alzheimer s disease
Aphasiology, 2012Co-Authors: Seyed Ahmad Sajjadi, Karalyn Patterson, Michal Tomek, Peter J NestorAbstract:Background: Neurodegenerative syndromes are associated with varying degrees of language impairment. Connected speech analysis provides the most realistic measure of language function but its use has been restricted by operational constraints. Aims: In this prospective study we assessed the relative utility of a picture description task and a semi-structured interview in exposing the language decline in Semantic Dementia (SD) and typical mild Alzheimer's disease (AD), compared to each other and to healthy volunteers. Methods & Procedures: Our cohort comprised 16 patients with a clinical diagnosis of SD, 20 with mild typical AD, and 30 healthy participants. All speech samples were recorded during a face-to-face interview and were subjected to a well-controlled quantitative analysis. Outcomes & Results: Our results suggest that (a) the picture description task is more sensitive to abnormalities in the Semantic measures, whereas the interviews are better at exposing morpho-syntactic deficits; (b) circumlocuti...
Olivier Piguet - One of the best experts on this subject based on the ideXlab platform.
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cognitive intervention in Semantic Dementia maintaining words over time
Alzheimer Disease & Associated Disorders, 2015Co-Authors: Sharon Savage, Olivier Piguet, John R HodgesAbstract:Patients with Semantic Dementia (SD) can improve their naming ability through cognitive intervention, with good retention 1 month later. Beyond this time, improvements often fade, yet no studies have investigated how to maintain performance. Nine SD patients completed a 2-month word training program and were then monitored over 6 months: firstly for 2 months without training, followed by a further 4 months, where additional training was provided to revise words, if required. All patients improved their naming immediately postintervention (P<0.001). After 2 months without practice, significant declines occurred in 4 patients. To sustain at least 80% of their postintervention performance 6 months later, 4 patients required minimal revision (<10 sessions over the period), 2 required regular weekly or biweekly revision sessions, with the remaining 3 patients requiring no revision sessions. During this period, group results indicated some decline in words that were initially known, but were not trained. Improvements in naming can be sustained in SD patients, with the support of less intense, but ongoing revision. Training words that are still known appears to help prolong memory of these words.
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right anterior temporal lobe dysfunction underlies theory of mind impairments in Semantic Dementia
Brain, 2014Co-Authors: Muireann Irish, John R Hodges, Olivier PiguetAbstract:Semantic Dementia is a progressive neurodegenerative disorder characterized by the amodal and profound loss of Semantic knowledge attributable to the degeneration of the left anterior temporal lobe. Although traditionally conceptualized as a language disorder, patients with Semantic Dementia display significant alterations in behaviour and socioemotional functioning. Recent evidence points to an impaired capacity for theory of mind in predominantly left-lateralized cases of Semantic Dementia; however, it remains unclear to what extent Semantic impairments contribute to these deficits. Further the neuroanatomical signature of such disturbance remains unknown. Here, we sought to determine the neural correlates of theory of mind performance in patients with left predominant Semantic Dementia ( n = 11), in contrast with disease-matched cases with behavioural-variant frontotemporal Dementia ( n = 10) and Alzheimer’s disease ( n = 10), and healthy older individuals ( n = 14) as control participants. Participants completed a simple cartoons task, in which they were required to describe physical and theory of mind scenarios. Irrespective of subscale, patients with Semantic Dementia exhibited marked impairments relative to control subjects; however, only theory of mind deficits persisted when we covaried for Semantic comprehension. Voxel-based morphometry analyses revealed that atrophy in right anterior temporal lobe structures, including the right temporal fusiform cortex, right inferior temporal gyrus, bilateral temporal poles and amygdalae, correlated significantly with theory of mind impairments in the Semantic Dementia group. Our results point to the marked disruption of cognitive functions beyond the language domain in Semantic Dementia, not exclusively attributable to Semantic processing impairments. The significant involvement of right anterior temporal structures suggests that with disease evolution, the encroachment of pathology into the contralateral hemisphere heralds the onset of social cognitive deficits in this syndrome. * Abbreviations : ACE-R : Addenbrooke’s Cognitive Examination-Revised FTD : frontotemporal Dementia ToM : theory of mind
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considering the role of Semantic memory in episodic future thinking evidence from Semantic Dementia
Brain, 2012Co-Authors: Muireann Irish, John R Hodges, Olivier Piguet, Donna Rose AddisAbstract:Semantic Dementia is a progressive neurodegenerative condition characterized by the profound and amodal loss of Semantic memory in the context of relatively preserved episodic memory. In contrast, patients with Alzheimer's disease typically display impairments in episodic memory, but with Semantic deficits of a much lesser magnitude than in Semantic Dementia. Our understanding of episodic memory retrieval in these cohorts has greatly increased over the last decade, however, we know relatively little regarding the ability of these patients to imagine and describe possible future events, and whether episodic future thinking is mediated by divergent neural substrates contingent on Dementia subtype. Here, we explored episodic future thinking in patients with Semantic Dementia ( n = 11) and Alzheimer's disease ( n = 11), in comparison with healthy control participants ( n = 10). Participants completed a battery of tests designed to probe episodic and Semantic thinking across past and future conditions, as well as standardized tests of episodic and Semantic memory. Further, all participants underwent magnetic resonance imaging. Despite their relatively intact episodic retrieval for recent past events, the Semantic Dementia cohort showed significant impairments for episodic future thinking. In contrast, the group with Alzheimer's disease showed parallel deficits across past and future episodic conditions. Voxel-based morphometry analyses confirmed that atrophy in the left inferior temporal gyrus and bilateral temporal poles, regions strongly implicated in Semantic memory, correlated significantly with deficits in episodic future thinking in Semantic Dementia. Conversely, episodic future thinking performance in Alzheimer's disease correlated with atrophy in regions associated with episodic memory, namely the posterior cingulate, parahippocampal gyrus and frontal pole. These distinct neuroanatomical substrates contingent on Dementia group were further qualified by correlational analyses that confirmed the relation between Semantic memory deficits and episodic future thinking in Semantic Dementia, in contrast with the role of episodic memory deficits and episodic future thinking in Alzheimer's disease. Our findings demonstrate that Semantic knowledge is critical for the construction of novel future events, providing the necessary scaffolding into which episodic details can be integrated. Further research is necessary to elucidate the precise contribution of Semantic memory to future thinking, and to explore how deficits in self-projection manifest on behavioural and social levels in different Dementia subtypes. * Abbreviation : VBM : voxel-based morphometry
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considering the role of Semantic memory in episodic future thinking evidence from Semantic Dementia
Brain, 2012Co-Authors: Muireann Irish, John R Hodges, Olivier Piguet, Donna Rose AddisAbstract:Semantic Dementia is a progressive neurodegenerative condition characterized by the profound and amodal loss of Semantic memory in the context of relatively preserved episodic memory. In contrast, patients with Alzheimer's disease typically display impairments in episodic memory, but with Semantic deficits of a much lesser magnitude than in Semantic Dementia. Our understanding of episodic memory retrieval in these cohorts has greatly increased over the last decade, however, we know relatively little regarding the ability of these patients to imagine and describe possible future events, and whether episodic future thinking is mediated by divergent neural substrates contingent on Dementia subtype. Here, we explored episodic future thinking in patients with Semantic Dementia (n=11) and Alzheimer's disease (n=11), in comparison with healthy control participants (n=10). Participants completed a battery of tests designed to probe episodic and Semantic thinking across past and future conditions, as well as standardized tests of episodic and Semantic memory. Further, all participants underwent magnetic resonance imaging. Despite their relatively intact episodic retrieval for recent past events, the Semantic Dementia cohort showed significant impairments for episodic future thinking. In contrast, the group with Alzheimer's disease showed parallel deficits across past and future episodic conditions. Voxel-based morphometry analyses confirmed that atrophy in the left inferior temporal gyrus and bilateral temporal poles, regions strongly implicated in Semantic memory, correlated significantly with deficits in episodic future thinking in Semantic Dementia. Conversely, episodic future thinking performance in Alzheimer's disease correlated with atrophy in regions associated with episodic memory, namely the posterior cingulate, parahippocampal gyrus and frontal pole. These distinct neuroanatomical substrates contingent on Dementia group were further qualified by correlational analyses that confirmed the relation between Semantic memory deficits and episodic future thinking in Semantic Dementia, in contrast with the role of episodic memory deficits and episodic future thinking in Alzheimer's disease. Our findings demonstrate that Semantic knowledge is critical for the construction of novel future events, providing the necessary scaffolding into which episodic details can be integrated. Further research is necessary to elucidate the precise contribution of Semantic memory to future thinking, and to explore how deficits in self-projection manifest on behavioural and social levels in different Dementia subtypes.
Muireann Irish - One of the best experts on this subject based on the ideXlab platform.
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right anterior temporal lobe dysfunction underlies theory of mind impairments in Semantic Dementia
Brain, 2014Co-Authors: Muireann Irish, John R Hodges, Olivier PiguetAbstract:Semantic Dementia is a progressive neurodegenerative disorder characterized by the amodal and profound loss of Semantic knowledge attributable to the degeneration of the left anterior temporal lobe. Although traditionally conceptualized as a language disorder, patients with Semantic Dementia display significant alterations in behaviour and socioemotional functioning. Recent evidence points to an impaired capacity for theory of mind in predominantly left-lateralized cases of Semantic Dementia; however, it remains unclear to what extent Semantic impairments contribute to these deficits. Further the neuroanatomical signature of such disturbance remains unknown. Here, we sought to determine the neural correlates of theory of mind performance in patients with left predominant Semantic Dementia ( n = 11), in contrast with disease-matched cases with behavioural-variant frontotemporal Dementia ( n = 10) and Alzheimer’s disease ( n = 10), and healthy older individuals ( n = 14) as control participants. Participants completed a simple cartoons task, in which they were required to describe physical and theory of mind scenarios. Irrespective of subscale, patients with Semantic Dementia exhibited marked impairments relative to control subjects; however, only theory of mind deficits persisted when we covaried for Semantic comprehension. Voxel-based morphometry analyses revealed that atrophy in right anterior temporal lobe structures, including the right temporal fusiform cortex, right inferior temporal gyrus, bilateral temporal poles and amygdalae, correlated significantly with theory of mind impairments in the Semantic Dementia group. Our results point to the marked disruption of cognitive functions beyond the language domain in Semantic Dementia, not exclusively attributable to Semantic processing impairments. The significant involvement of right anterior temporal structures suggests that with disease evolution, the encroachment of pathology into the contralateral hemisphere heralds the onset of social cognitive deficits in this syndrome. * Abbreviations : ACE-R : Addenbrooke’s Cognitive Examination-Revised FTD : frontotemporal Dementia ToM : theory of mind
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Right anterior temporal lobe dysfunction underlies theory of mind impairments in Semantic Dementia
Brain, 2014Co-Authors: Muireann Irish, John R HodgesAbstract:Semantic Dementia is a progressive neurodegenerative disorder characterized by the amodal and profound loss of Semantic knowledge attributable to the degeneration of the left anterior temporal lobe. Although traditionally conceptualized as a language disorder, patients with Semantic Dementia display significant alterations in behaviour and socioemotional functioning. Recent evidence points to an impaired capacity for theory of mind in predominantly left-lateralized cases of Semantic Dementia; however, it remains unclear to what extent Semantic impairments contribute to these deficits. Further the neuroanatomical signature of such disturbance remains unknown. Here, we sought to determine the neural correlates of theory of mind performance in patients with left predominant Semantic Dementia (n=11), in contrast with disease-matched cases with behavioural-variant frontotemporal Dementia (n=10) and Alzheimer's disease (n=10), and healthy older individuals (n=14) as control participants. Participants completed a simple cartoons task, in which they were required to describe physical and theory of mind scenarios. Irrespective of subscale, patients with Semantic Dementia exhibited marked impairments relative to control subjects; however, only theory of mind deficits persisted when we covaried for Semantic comprehension. Voxel-based morphometry analyses revealed that atrophy in right anterior temporal lobe structures, including the right temporal fusiform cortex, right inferior temporal gyrus, bilateral temporal poles and amygdalae, correlated significantly with theory of mind impairments in the Semantic Dementia group. Our results point to the marked disruption of cognitive functions beyond the language domain in Semantic Dementia, not exclusively attributable to Semantic processing impairments. The significant involvement of right anterior temporal structures suggests that with disease evolution, the encroachment of pathology into the contralateral hemisphere heralds the onset of social cognitive deficits in this syndrome.
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considering the role of Semantic memory in episodic future thinking evidence from Semantic Dementia
Brain, 2012Co-Authors: Muireann Irish, John R Hodges, Olivier Piguet, Donna Rose AddisAbstract:Semantic Dementia is a progressive neurodegenerative condition characterized by the profound and amodal loss of Semantic memory in the context of relatively preserved episodic memory. In contrast, patients with Alzheimer's disease typically display impairments in episodic memory, but with Semantic deficits of a much lesser magnitude than in Semantic Dementia. Our understanding of episodic memory retrieval in these cohorts has greatly increased over the last decade, however, we know relatively little regarding the ability of these patients to imagine and describe possible future events, and whether episodic future thinking is mediated by divergent neural substrates contingent on Dementia subtype. Here, we explored episodic future thinking in patients with Semantic Dementia ( n = 11) and Alzheimer's disease ( n = 11), in comparison with healthy control participants ( n = 10). Participants completed a battery of tests designed to probe episodic and Semantic thinking across past and future conditions, as well as standardized tests of episodic and Semantic memory. Further, all participants underwent magnetic resonance imaging. Despite their relatively intact episodic retrieval for recent past events, the Semantic Dementia cohort showed significant impairments for episodic future thinking. In contrast, the group with Alzheimer's disease showed parallel deficits across past and future episodic conditions. Voxel-based morphometry analyses confirmed that atrophy in the left inferior temporal gyrus and bilateral temporal poles, regions strongly implicated in Semantic memory, correlated significantly with deficits in episodic future thinking in Semantic Dementia. Conversely, episodic future thinking performance in Alzheimer's disease correlated with atrophy in regions associated with episodic memory, namely the posterior cingulate, parahippocampal gyrus and frontal pole. These distinct neuroanatomical substrates contingent on Dementia group were further qualified by correlational analyses that confirmed the relation between Semantic memory deficits and episodic future thinking in Semantic Dementia, in contrast with the role of episodic memory deficits and episodic future thinking in Alzheimer's disease. Our findings demonstrate that Semantic knowledge is critical for the construction of novel future events, providing the necessary scaffolding into which episodic details can be integrated. Further research is necessary to elucidate the precise contribution of Semantic memory to future thinking, and to explore how deficits in self-projection manifest on behavioural and social levels in different Dementia subtypes. * Abbreviation : VBM : voxel-based morphometry
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considering the role of Semantic memory in episodic future thinking evidence from Semantic Dementia
Brain, 2012Co-Authors: Muireann Irish, John R Hodges, Olivier Piguet, Donna Rose AddisAbstract:Semantic Dementia is a progressive neurodegenerative condition characterized by the profound and amodal loss of Semantic memory in the context of relatively preserved episodic memory. In contrast, patients with Alzheimer's disease typically display impairments in episodic memory, but with Semantic deficits of a much lesser magnitude than in Semantic Dementia. Our understanding of episodic memory retrieval in these cohorts has greatly increased over the last decade, however, we know relatively little regarding the ability of these patients to imagine and describe possible future events, and whether episodic future thinking is mediated by divergent neural substrates contingent on Dementia subtype. Here, we explored episodic future thinking in patients with Semantic Dementia (n=11) and Alzheimer's disease (n=11), in comparison with healthy control participants (n=10). Participants completed a battery of tests designed to probe episodic and Semantic thinking across past and future conditions, as well as standardized tests of episodic and Semantic memory. Further, all participants underwent magnetic resonance imaging. Despite their relatively intact episodic retrieval for recent past events, the Semantic Dementia cohort showed significant impairments for episodic future thinking. In contrast, the group with Alzheimer's disease showed parallel deficits across past and future episodic conditions. Voxel-based morphometry analyses confirmed that atrophy in the left inferior temporal gyrus and bilateral temporal poles, regions strongly implicated in Semantic memory, correlated significantly with deficits in episodic future thinking in Semantic Dementia. Conversely, episodic future thinking performance in Alzheimer's disease correlated with atrophy in regions associated with episodic memory, namely the posterior cingulate, parahippocampal gyrus and frontal pole. These distinct neuroanatomical substrates contingent on Dementia group were further qualified by correlational analyses that confirmed the relation between Semantic memory deficits and episodic future thinking in Semantic Dementia, in contrast with the role of episodic memory deficits and episodic future thinking in Alzheimer's disease. Our findings demonstrate that Semantic knowledge is critical for the construction of novel future events, providing the necessary scaffolding into which episodic details can be integrated. Further research is necessary to elucidate the precise contribution of Semantic memory to future thinking, and to explore how deficits in self-projection manifest on behavioural and social levels in different Dementia subtypes.
Matthew Lambon A. Ralph - One of the best experts on this subject based on the ideXlab platform.
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SD-Squared: On the Association Between Semantic Dementia
2015Co-Authors: Surface Dyslexia, David C. Plaut, Anna M. Woollams, Matthew Lambon A. Ralph, Karalyn PattersonAbstract:Within the connectionist triangle model of reading aloud, interaction between Semantic and phonological representations occurs for all words but is particularly important for correct pronunciation of lower frequency exception words. This framework therefore predicts that (a) Semantic Dementia, which compromises Semantic knowledge, should be accompanied by surface dyslexia, a frequency-modulated deficit in exception word reading, and (b) there should be a significant relationship between the severity of Semantic degradation and the severity of surface dyslexia. The authors evaluated these claims with reference to 100 observations of reading data from 51 cases of Semantic Dementia. Surface dyslexia was rampant, and a simple composite Semantic measure accounted for half of the variance in low-frequency exception word reading. Although in 3 cases initial testing revealed a moderate Semantic impairment but normal exception word reading, all of these became surface dyslexic as their Semantic knowledge deteriorated further. The connectionist account attributes such cases to premorbid individual variation in Semantic reliance for accurate exception word reading. These results provide a striking demonstration of the association between Semantic Dementia and surface dyslexia, a phenomenon that the authors have dubbed SD-squared
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SD-squared 1 RUNNING HEAD: Semantic Dementia AND SURFACE DYSLEXIA SD-SQUARED: ON THE ASSOCIATION BETWEEN Semantic
2014Co-Authors: Surface Dyslexia, David C. Plaut, Anna M. Woollams, Matthew Lambon A. Ralph, Karalyn PattersonAbstract:Within the connectionist triangle model of reading aloud, interaction between Semantic and phonological representations occurs for all words but is particularly important for correct pronunciation of lower-frequency exception words. This framework therefore predicts that (a) Semantic Dementia, which compromises Semantic knowledge, should be accompanied by surface dyslexia, a frequencymodulated deficit in exception word reading; and (b) there should be a significant relationship between the severity of Semantic Dementia and of surface dyslexia. We evaluated these claims with reference to 100 observations of reading data from 51 cases of Semantic Dementia. Surface dyslexia was rampant, and a simple composite Semantic measure accounted for more than half of the variance in low-frequency exception word reading. These results provide a striking demonstration of the association between Semantic Dementia (SD) and surface dyslexia (SD), a phenomenon that we have dubbed SD-squared
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the degraded concept representation system in Semantic Dementia damage to pan modal hub then visual spoke
Brain, 2012Co-Authors: Paul Hoffman, Roy W Jones, Matthew Lambon A. RalphAbstract:The core clinical feature of Semantic Dementia is a progressive yet selective degradation of conceptual knowledge. Understanding the cognitive and neuroanatomical basis for this deficit is a key challenge for both clinical and basic science. Some researchers attribute the deficit to damage to pan-modal conceptual representations that are independent of any particularsensory?motor modality and are represented in the ventrolateral anterior temporal lobes. Others claim that damage to modality-specific visual feature representations in the occipitotemporal ?ventral stream? is responsible. In the present study,we tested the hypothesis that concept degradation in Semantic Dementia involves a combination of these pan-modal and modality-specific elements. We investigated factors influencing knowledge of object concepts by analysing 43 sets of picture-naming data from patients with Semantic Dementia. We found a strong influence of two pan-modal factors: highly familiar and typical items were named more accurately than less familiar/atypical items at all stages of the disorder. Itemsassociated with rich sensory-motor information were also named more successfully at all stages, and this effect was present for sound/motion knowledge and tactile/action knowledge when these modalities were studied separately. However, there was no advantage for items rich in visual colour/form characteristics; instead, this factor had an increasingly negative impact in the laterstages of the disorder. We propose that these results are best explained by a combination of (i) degradation of modality-independent conceptual representations, which is present throughout the disorder and is a consequence of atrophy focused on the ventrolateral anterior temporal lobes; and (ii) a later additional deficit for concepts that depend heavily on visual colour/form information, caused by the spreading of atrophy to posterior ventral temporal regions specialized for representing this information. This explanation is consistent with a graded hub-and-spoke model of conceptual knowledge, in which there is a gradual convergence of information along the temporal lobes, with visual attributes represented in the posterior cortex giving way to pan-modal representations in the anterior areas.
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relearning in Semantic Dementia reflects contributions from both medial temporal lobe episodic and degraded neocortical Semantic systems evidence in support of the complementary learning systems theory
Neuropsychologia, 2011Co-Authors: Emily J Mayberry, Karen Sage, Sheeba Ehsan, Matthew Lambon A. RalphAbstract:When relearning words, patients with Semantic Dementia (SD) exhibit a characteristic rigidity, including a failure to generalise names to untrained exemplars of trained concepts. This has been attributed to an over-reliance on the medial temporal region which captures information in sparse, non-overlapping and therefore rigid representations. The current study extends previous investigations of SD relearning by re-examining the additional contribution made by the degraded cortical Semantic system. The standard relearning protocol was modified by careful selection of foils to show that people with Semantic Dementia were sometimes able to extend their learning appropriately but that this correct generalisation was minimal (i.e. the patients under-generalised their learning). The revised assessment procedure highlighted the fact that, after relearning, the participants also incorrectly over-generalised the learned label to closely related concepts. It is unlikely that these behaviours would occur if the participants had only formed sparse hippocampal representations. These novel data build on the notion that people with Semantic Dementia engage both the degraded cortical Semantic (neocortex) and the episodic (medial temporal) systems to learn. Because of neocortical damage to the anterior temporal lobes, relearning is disordered with a characteristic pattern of under- and over-generalisation.
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comprehension of concrete and abstract words in Semantic Dementia
Neuropsychology (journal), 2009Co-Authors: Elizabeth Jefferies, Karalyn Patterson, Roy W Jones, Matthew Lambon A. RalphAbstract:The vast majority of brain-injured patients with Semantic impairment have better comprehension of concrete than abstract words. In contrast, several patients with Semantic Dementia (SD), who show circumscribed atrophy of the anterior temporal lobes bilaterally, have been reported to show reverse imageability effects, that is, relative preservation of abstract knowledge. Although these reports largely concern individual patients, some researchers have recently proposed that superior comprehension of abstract concepts is a characteristic feature of SD. This would imply that the anterior temporal lobes are particularly crucial for processing sensory aspects of Semantic knowledge, which are associated with concrete not abstract concepts. However, functional neuroimaging studies of healthy participants do not unequivocally predict reverse imageability effects in SD because the temporal poles sometimes show greater activation for more abstract concepts. The authors examined a case-series of 11 SD patients on a synonym judgment test that orthogonally varied the frequency and imageability of the items. All patients had higher success rates for more imageable as well as more frequent words, suggesting that (1) the anterior temporal lobes underpin Semantic knowledge for both concrete and abstract concepts, (2) more imageable items--perhaps because of their richer multimodal representations--are typically more robust in the face of global Semantic degradation and (3) reverse imageability effects are not a characteristic feature of SD.
