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Semantic dementia and persisting Wernicke’s aphasia: Linguistic and anatomical profiles

Few studies have directly compared the clinical and anatomical characteristics of patients with progressive aphasia to those of patients with aphasia caused by stroke. In the current study we examined fluent forms of aphasia in these two groups, specifically semantic dementia (SD) and persisting Wernicke’s aphasia (WA) due to stroke. We compared 10 patients with SD to 10 age- and education-matched patients with WA in three language domains: language comprehension (single words and sentences), spontaneous speech and visual semantics. Neuroanatomical involvement was analyzed using disease-specific image analysis techniques: voxel-based morphometry (VBM) for patients with SD and overlays of lesion digitized lesion reconstructions in patients with WA. Patients with SD and WA were both impaired on tasks that involved visual semantics, but patients with SD were less impaired in spontaneous speech and sentence comprehension. The anatomical findings showed that different regions were most affected in the two disorders: the left anterior temporal lobe in SD and the left posterior middle temporal gyrus in chronic WA. This study highlights that the two syndromes classically associated with language comprehension deficits in aphasia due to stroke and neurodegenerative disease are clinically distinct, most likely due to distinct distributions of damage in the temporal lobe.

from Brain and Language

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Semantic dementia and persisting Wernicke’s aphasia: Linguistic and anatomical profiles

Few studies have directly compared the clinical and anatomical characteristics of patients with progressive aphasia to those of patients with aphasia caused by stroke. In the current study we examined fluent forms of aphasia in these two groups, specifically semantic dementia (SD) and persisting Wernicke’s aphasia (WA) due to stroke. We compared 10 patients with SD to 10 age- and education-matched patients with WA in three language domains: language comprehension (single words and sentences), spontaneous speech and visual semantics. Neuroanatomical involvement was analyzed using disease-specific image analysis techniques: voxel-based morphometry (VBM) for patients with SD and overlays of lesion digitized lesion reconstructions in patients with WA. Patients with SD and WA were both impaired on tasks that involved visual semantics, but patients with SD were less impaired in spontaneous speech and sentence comprehension. The anatomical findings showed that different regions were most affected in the two disorders: the left anterior temporal lobe in SD and the left posterior middle temporal gyrus in chronic WA. This study highlights that the two syndromes classically associated with language comprehension deficits in aphasia due to stroke and neurodegenerative disease are clinically distinct, most likely due to distinct distributions of damage in the temporal lobe.

from Brain and Language

Semantic dementia and persisting Wernicke’s aphasia: Linguistic and anatomical profiles

Few studies have directly compared the clinical and anatomical characteristics of patients with progressive aphasia to those of patients with aphasia caused by stroke. In the current study we examined fluent forms of aphasia in these two groups, specifically semantic dementia (SD) and persisting Wernicke’s aphasia (WA) due to stroke. We compared 10 patients with SD to 10 age- and education-matched patients with WA in three language domains: language comprehension (single words and sentences), spontaneous speech and visual semantics. Neuroanatomical involvement was analyzed using disease-specific image analysis techniques: voxel-based morphometry (VBM) for patients with SD and overlays of lesion digitized lesion reconstructions in patients with WA. Patients with SD and WA were both impaired on tasks that involved visual semantics, but patients with SD were less impaired in spontaneous speech and sentence comprehension. The anatomical findings showed that different regions were most affected in the two disorders: the left anterior temporal lobe in SD and the left posterior middle temporal gyrus in chronic WA. This study highlights that the two syndromes classically associated with language comprehension deficits in aphasia due to stroke and neurodegenerative disease are clinically distinct, most likely due to distinct distributions of damage in the temporal lobe.<p><p>from <a href=”Brain” _mce_href=”http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WC0-526MY1W-1&_user=108452&_coverDate=02%2F18%2F2011&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000059732&_version=1&_urlVersion=0&_userid=108452&md5=002ddc5a09de2364a6fdd719d92c8128&searchtype=a”>null”>http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WC0-526MY1W-1&_user=108452&_coverDate=02%2F18%2F2011&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000059732&_version=1&_urlVersion=0&_userid=108452&md5=002ddc5a09de2364a6fdd719d92c8128&searchtype=a”><em>Brain and Language</em></a></p>

Bias of quantifier scope interpretation is attenuated in normal aging and semantic dementia

Many sentences with two quantifiers exhibit a phenomenon known as “quantifier scope ambiguity.” Consider the example A unicorn ran through every garden, which contains the quantifiers “a” and “every.” Most speakers of English agree that it may refer to one or more than one unicorn. Very little previous work has evaluated the ability of brain-damaged or aphasic patients to interpret such sentences. We administered a sentence-reading task with picture verification to a group of semantic dementia patients (N = 5) and a matched group of cognitively normal controls (N = 23). Controls exhibited a tendency to interpret the word every as having wide scope regardless of the order of quantifiers, as evidenced by decreased reaction time and increased accuracy when verifying pictures that required this interpretation. This bias was attenuated by increasing age and by the presence of semantic dementia. Furthermore, higher FAS fluency scores were associated with slower responses and more errors, while higher semantic fluency scores were associated with the opposite pattern. These findings fit best with a model in which the initial products of linguistic analysis are underspecified and biases in their interpretation arise subsequently through frontally mediated logical or pragmatic reasoning.

from the Journal of Neurolinguistics

Phonological learning in semantic dementia

Patients with semantic dementia (SD) have anterior temporal lobe (ATL) atrophy that gives rise to a highly selective deterioration of semantic knowledge. Despite pronounced anomia and poor comprehension of words and pictures, SD patients have well-formed, fluent speech and normal digit span. Given the intimate connection between phonological STM and word learning revealed by both neuropsychological and developmental studies, SD patients might be expected to show good acquisition of new phonological forms, even though their ability to map these onto meanings is impaired. In contradiction of these predictions, a limited amount of previous research has found poor learning of new phonological forms in SD. In a series of experiments, we examined whether SD patient, GE, could learn novel phonological sequences and, if so, under which circumstances. GE showed normal benefits of phonological knowledge in STM (i.e., normal phonotactic frequency and phonological similarity effects) but reduced support from semantic memory (i.e., poor immediate serial recall for semantically degraded words, characterised by frequent item errors). Next, we demonstrated normal learning of serial order information for repeated lists of single-digit number words using the Hebb paradigm: these items were well-understood allowing them to be repeated without frequent item errors. In contrast, patient GE showed little learning of nonsense syllable sequences using the same Hebb paradigm. Detailed analysis revealed that both GE and the controls showed a tendency to learn their own errors as opposed to the target items. Finally, we showed normal learning of phonological sequences for GE when he was prevented from repeating his errors. These findings confirm that the ATL atrophy in SD disrupts phonological processing for semantically-degraded words but leaves the phonological architecture intact. Consequently, when item errors are minimised, phonological STM can support the acquisition of new phoneme sequences in patients with SD.

from Neuropsychologia

Model-oriented naming therapy in semantic dementia: A single-case fMRI study

Conclusions: Cueing hierarchies were successful, resulting in specific and immediate treatment effects, corroborating previous treatment studies in semantic dementia. Treatment-induced changes in cortical activity were mainly concentrated in right temporal cortex. Since right-sided modulation of cortical activity was associated with training-induced improvements in task performance, it may reflect right hemispheric compensatory mechanisms in this participant.

from Aphasiology

Model-oriented naming therapy in semantic dementia: A single-case fMRI study

Conclusions: Cueing hierarchies were successful, resulting in specific and immediate treatment effects, corroborating previous treatment studies in semantic dementia. Treatment-induced changes in cortical activity were mainly concentrated in right temporal cortex. Since right-sided modulation of cortical activity was associated with training-induced improvements in task performance, it may reflect right hemispheric compensatory mechanisms in this participant.

from Aphasiology

Connected speech production in three variants of primary progressive aphasia

Primary progressive aphasia is a clinical syndrome defined by progressive deficits isolated to speech and/or language, and can be classified into non-fluent, semantic and logopenic variants based on motor speech, linguistic and cognitive features. The connected speech of patients with primary progressive aphasia has often been dichotomized simply as ‘fluent’ or ‘non-fluent’, however fluency is a multidimensional construct that encompasses features such as speech rate, phrase length, articulatory agility and syntactic structure, which are not always impacted in parallel. In this study, our first objective was to improve the characterization of connected speech production in each variant of primary progressive aphasia, by quantifying speech output along a number of motor speech and linguistic dimensions simultaneously. Secondly, we aimed to determine the neuroanatomical correlates of changes along these different dimensions.

from Brain

Two cases of frontotemporal dementia with predominant temporal lobe atrophy

Frontotemporal dementia (FTD) is a subtype of frontotemporal lobar degeneration, which also includes semantic dementia (SD) and progressive non-fluent aphasia. Frontotemporal dementia is characterized by changes in personality and behavioral abnormalities, generally associated with predominant frontal lobe atrophy. Conversely, SD is typically characterized by Gogi (word meaning) aphasia based on semantic memory impairment and is associated with predominant temporal lobe atrophy. However, in the present cases, we diagnosed FTD on the basis of clinical symptoms, such as disinhibition, indifference, and stereotypy, without semantic memory impairment, even though neuroimaging showed predominant temporal lobe atrophy. We suggest that clinical symptoms are the most important cues for an accurate clinical diagnosis and there is no exclusive relationship between the syndrome and atrophy of the temporal lobes.

from Psychogeriatrics

The cognitive organization of music knowledge: a clinical analysis

Despite much recent interest in the clinical neuroscience of music processing, the cognitive organization of music as a domain of non-verbal knowledge has been little studied. Here we addressed this issue systematically in two expert musicians with clinical diagnoses of semantic dementia and Alzheimer’s disease, in comparison with a control group of healthy expert musicians. In a series of neuropsychological experiments, we investigated associative knowledge of musical compositions (musical objects), musical emotions, musical instruments (musical sources) and music notation (musical symbols). These aspects of music knowledge were assessed in relation to musical perceptual abilities and extra-musical neuropsychological functions. The patient with semantic dementia showed relatively preserved recognition of musical compositions and musical symbols despite severely impaired recognition of musical emotions and musical instruments from sound. In contrast, the patient with Alzheimer’s disease showed impaired recognition of compositions, with somewhat better recognition of composer and musical era, and impaired comprehension of musical symbols, but normal recognition of musical emotions and musical instruments from sound. The findings suggest that music knowledge is fractionated, and superordinate musical knowledge is relatively more robust than knowledge of particular music. We propose that music constitutes a distinct domain of non-verbal knowledge but shares certain cognitive organizational features with other brain knowledge systems. Within the domain of music knowledge, dissociable cognitive mechanisms process knowledge derived from physical sources and the knowledge of abstract musical entities.

from Brain

Loss of word-meaning with spared object semantics in a case of mixed primary progressive aphasia

This article provides a detailed assessment of patient HT with a history of progressive language deterioration of approximately 6 years presenting now as a fluent jargon aphasic with severe impairment of both speech production and comprehension. Neuropsychological testing of non-verbal cognitive functions showed no impairment, leading to the assumption of primary progressive aphasia (PPA). Contrary to the clinical criteria of the known PPA-subtypes there was nearly parallel decline of word comprehension and motor speech. HT also showed a significant dissociation between verbal and non-verbal semantic abilities resulting in severely impaired word comprehension with object semantics relatively spared. MRI scanning revealed pronounced focal atrophy of the left anterior temporal lobe and the left perisylvian region with relatively spared right temporal involvement. The clinical diagnostic criteria for PPA-subtypes do not seem to apply to the language features shown by our patient. The similarities and distinctions to semantic dementia and progressive non-fluent aphasia (PNFA) as subtypes of PPA will be discussed. The distinction between PNFA and SD may represent an oversimplification of the clinical presentations of PPA. It is also suggested that a mixed version of primary progressive aphasia should be taken into consideration as accepted clinical subtype.

from Brain and Language

A computerized technique to assess language use patterns in patients with frontotemporal dementia

Frontotemporal lobar degeneration (FTLD) is a neurodegenerative disorder that affects language. We applied a computerized information-theoretic technique to assess the type and severity of language-related FTLD symptoms. Audio-recorded samples of 48 FTLD patients from three participating medical centers were elicited using the Cookie-Theft picture stimulus. The audio was transcribed and analyzed by calculating two measures: a perplexity index and an out-of-vocabulary (OOV) rate. The perplexity index represents the degree of deviation in word patterns used by FTLD patients compared to patterns of healthy adults. The OOV rate represents the proportion of words used by FTLD patients that were not used by the healthy speakers to describe the stimulus. In this clinically well-characterized cohort, the perplexity index and the OOV rate were sensitive to spontaneous language manifestations of semantic dementia and the distinction between semantic dementia and progressive logopenic aphasia variants of FTLD. Our study not only supports a novel technique for the characterization of language-related symptoms of FTLD in clinical trial settings, it also validates the basis for the clinical diagnosis of semantic dementia as a distinct syndrome.

from the Journal of Neurolinguistics

Language networks in semantic dementia

Cognitive deficits in semantic dementia have been attributed to anterior temporal lobe grey matter damage; however, key aspects of the syndrome could be due to altered anatomical connectivity between language pathways involving the temporal lobe. The aim of this study was to investigate the left language-related cerebral pathways in semantic dementia using diffusion tensor imaging-based tractography and to combine the findings with cortical anatomical and functional magnetic resonance imaging data obtained during a reading activation task. The left inferior longitudinal fasciculus, arcuate fasciculus and fronto-parietal superior longitudinal fasciculus were tracked in five semantic dementia patients and eight healthy controls. The left uncinate fasciculus and the genu and splenium of the corpus callosum were also obtained for comparison with previous studies. From each tract, mean diffusivity, fractional anisotropy, as well as parallel and transverse diffusivities were obtained. Diffusion tensor imaging results were related to grey and white matter atrophy volume assessed by voxel-based morphometry and functional magnetic resonance imaging activations during a reading task. Semantic dementia patients had significantly higher mean diffusivity, parallel and transverse in the inferior longitudinal fasciculus. The arcuate and uncinate fasciculi demonstrated significantly higher mean diffusivity, parallel and transverse and significantly lower fractional anisotropy. The fronto-parietal superior longitudinal fasciculus was relatively spared, with a significant difference observed for transverse diffusivity and fractional anisotropy, only. In the corpus callosum, the genu showed lower fractional anisotropy compared with controls, while no difference was found in the splenium. The left parietal cortex did not show significant volume changes on voxel-based morphometry and demonstrated normal functional magnetic resonance imaging activation in response to reading items that stress sublexical phonological processing. This study shows that semantic dementia is associated with anatomical damage to the major superior and inferior temporal white matter connections of the left hemisphere likely involved in semantic and lexical processes, with relative sparing of the fronto-parietal superior longitudinal fasciculus. Fronto-parietal regions connected by this tract were activated normally in the same patients during sublexical reading. These findings contribute to our understanding of the anatomical changes that occur in semantic dementia, and may further help to explain the dissociation between marked single-word and object knowledge deficits, but sparing of phonology and fluency in semantic dementia.

from Brain

“Pre-semantic” cognition revisited: Critical differences between semantic aphasia and semantic dementia

Patients with semantic dementia show a specific pattern of impairment on both verbal and non-verbal “pre-semantic” tasks: e.g., reading aloud, past tense generation, spelling to dictation, lexical decision, object decision, colour decision and delayed picture copying. All seven tasks are characterised by poorer performance for items that are atypical of the domain and “regularisation errors” (irregular/atypical items are produced as if they were domain-typical). The emergence of this pattern across diverse tasks in the same patients indicates that semantic memory plays a key role in all of these types of “pre-semantic” processing. However, this claim remains controversial because semantically-impaired patients sometimes fail to show an influence of regularity. This study demonstrates that (a) the location of brain damage and (b) the underlying nature of the semantic deficit affect the likelihood of observing the expected relationship between poor comprehension and regularity effects. We compared the effect of multimodal semantic impairment in the context of semantic dementia and stroke aphasia on the seven “pre-semantic” tasks listed above. In all of these tasks, the semantic aphasia patients were less sensitive to typicality than the semantic dementia patients, even though the two groups obtained comparable scores on semantic tests. The semantic aphasia group also made fewer regularisation errors and many more unrelated and perseverative responses. We propose that these group differences reflect the different locus for the semantic impairment in the two conditions: patients with semantic dementia have degraded semantic representations, whereas semantic aphasia patients show deregulated semantic cognition with concomitant executive deficits. These findings suggest a reinterpretation of single case studies of comprehension-impaired aphasic patients who fail to show the expected effect of regularity on “pre-semantic” tasks. Consequently, such cases do not demonstrate the independence of these tasks from semantic memory.

from Neuropsychologia

Personal experience and arithmetic meaning in semantic dementia

Arithmetic skills are generally claimed to be preserved in semantic dementia (SD), suggesting functional independence of arithmetic knowledge from other aspects of semantic memory. However, in a recent case series analysis we showed that arithmetic performance in SD is not entirely normal. The finding of a direct association between severity of patients’ semantic disorder and arithmetic impairment pointed to a closer relationship between semantic memory and arithmetic knowledge than previously acknowledged. The present study aimed to determine whether arithmetic performance in SD is subject to the same influences as has been found in other semantic domains, namely an autobiographical effect. SD patients were assessed on their ability to perform arithmetic in personally relevant compared to non-personal contexts. Patients who were regular, current followers of the television game show Countdown performed better on a simplified version of the show’s number game compared to a conventional written calculation task, whereas patients with no experience of Countdown demonstrated the opposite pattern. SD patients showed better knowledge of multiplication table ‘facts’ when these were embedded in a situation relevant to their daily lives compared to a non-personal arithmetic task. They also performed better on a written calculation task when problems were presented as a monetary transaction compared to a standard arithmetic problem. A reference group of patients with Alzheimer’s disease (AD) showed the reverse pattern. The findings provide convincing evidence that autobiographical relevance influences SD patients’ arithmetic performance. Moreover, they challenge current views on conceptual number knowledge as a unitary, abstract competence.

from Neuropsychologia