1,721,019 research outputs found
Semantic memory in object use
No full textWe studied five patients with semantic memory disorders, four with semantic dementia and one with herpes simplex virus encephalitis, to investigate the involvement of semantic conceptual knowledge in object use. Comparisons between patients who had semantic deficits of different severity, as well as the follow-up, showed that the ability to use objects was largely preserved when the deficit was mild but progressively decayed as the deficit became more severe. Naming was generally more impaired than object use. Production tasks (pantomime execution and actual object use) and comprehension tasks (pantomime recognition and action recognition) as well as functional knowledge about objects were impaired when the semantic deficit was severe. Semantic and unrelated errors were produced during object use, but actions were always fluent and patients performed normally on a novel tools task in which the semantic demand was minimal. Patients with severe semantic deficits scored borderline on ideational apraxia tasks. Our data indicate that functional semantic knowledge is crucial for using objects in a conventional way and suggest that non-semantic factors, mainly non-declarative components of memory, might compensate to some extent for semantic disorders and guarantee some residual ability to use very common objects independently of semantic knowledge. © 2009 Elsevier Ltd. All rights reserved
The deficit for the word-class "verb" in corticobasal degeneration: Linguistic expression of the movement disorder?
No full textWe describe five patients with corticobasal degeneration who had apraxia with an ideational component and reduced action/verb naming ability. Patients also had difficulty in a series of tasks devised to explore the conceptual representation of actions associated with manipulable objects, such as action recognition, action miming and pantomime recognition; however, their ability to name manipulable objects was comparatively preserved. According to the current interpretation of ideational apraxia [De Renzi, E., & Lucchelli, F. (1988). Ideational apraxia. Brain, 111, 1173-1185] we considered the patients' apraxic disorder as the motor expression of decay of the action representation and we hypothesized that this may also have contributed to the action-naming deficit. The results are discussed within a "multimodal model" of semantic memory in which the concept of action is seen as the product of the integration between sensorial and motor attributes. We suggest that corticobasal degeneration might offer a unique opportunity to validate this model because it is typically characterized by a frontoparietal damage [Gibb, W. R., Luthert, P. J., & Marsden, C. D. (1989). Corticobasal degeneration. Brain, 1, 1171-1192] that prevents integration of sensory and motor information. We conclude that the selective impairment of action/verb should also be studied from the point of view of a movement disorder and not only in terms of a lexical-semantic deficit. © 2007 Elsevier Ltd. All rights reserved
Naming of grammatical classes in frontotemporal dementias: Linguistic and non linguistic factors contribute to noun-verb dissociation
No full textWe studied noun and verb naming in three main variants of frontotemporal dementia: the frontal variant(Fv-FTD), primary progressive aphasia (PPA) and semantic dementia (SD). We further distinguished PPA in nonfluent and fluent forms and restricted diagnosis of SD to subjects with progressive semantic breakdown leading to agnosia for words and objects. Fv-FTD and nonfluent-PPA named objects better than actions, SD showed an inverse dissociation and no specific pattern emerged in fluent-PPA. In this last group, in spite of the broad definition of fluent aphasia, quite heterogeneous patterns of language disorders and word class dissociation emerged when single-subject analyses were performed. In fv-FTD correlations between executive tasks and action naming were stronger than between executive tasks and object naming. We conclude that both linguistic and non linguistic factors, in particular an executive deficit, contribute to grammatical class dissociation. We also suggest that the fluent vs. nonfluent distinction does not reflect the complexity of primary aphasia. © 2007 - IOS Press and the authors. All rights reserved
Unilateral Spatial Neglect in Degenerative Brain Pathology
No full textObjective: In an attempt to interpret neglect as a disconnection syndrome, it is currently proposed that the disorder results from disorganization of large-scale networks involved in attentional spatial processes rather than of individual brain areas. We hypothesize that as degenerative brain diseases are " system pathologies," degeneration could be restricted to some of the neural subsystems implicated in the functional organization of spatial attention and different neglect syndromes could emerge depending on the patterns of the subsystems involved. Method: We studied five neglect patients: one with corticobasal degeneration (CBD), three with Posterior Cortical Atrophy (PCA) and one with frontotemporal dementia (FTD). Results: The patient with CBD and left parietoccipital atrophy showed right allocentric neglect; the three patients with PCA mostly distributed in the right posterior regions showed left egocentric extrapersonal neglect; the patient with FTD, who displayed more severe frontotemporal atrophy on the right, had left motor-executive neglect for both personal and extrapersonal space. All patients also presented a deep breakdown of spatial working memory. Conclusion: Our data would confirm that left neglect is more frequent than right neglect also in degenerative pathology and that damage to different neural substrates can produce different types of neglect. Our findings are also consistent with the hypothesis that both lateralized and nonlateralized attention disorders contribute to generate the syndrome. We suggest that evidence from degenerative diseases may contribute to construction of models of spatial attention. © 2011 American Psychological Association
The influence of semantic and perceptual factors on lexical comprehension in aphasics and right brain-damaged subjects
No full textResting-state functional connectivity is modulated by cognitive reserve in early Parkinson’s disease
No full textBackground: Fronto-striatal disconnection is thought to be at the basis of dysexecutive symptoms in patients with Parkinson’s disease (PD). Multiple reserve-related processes may offer resilience against functional decline. Among these, cognitive reserve (CR) refers to the adaptability of cognitive processes. Objective: To test the hypothesis that functional connectivity of pathways associated with executive dysfunction in PD is modulated by CR. Methods: Twenty-six PD patients and 24 controls underwent resting-state functional magnetic resonance imaging. Functional connectivity was explored with independent component analysis and seed-based approaches. The following networks were selected from the outcome of the independent component analysis: default-mode (DMN), left and right fronto-parietal (l/rFPN), salience (SalN), sensorimotor (SMN), and occipital visual (OVN). Seed regions were selected in the substantia nigra and in the dorsolateral and ventromedial prefrontal cortex for the assessment of seed-based functional connectivity maps. Educational and occupational attainments were used as CR proxies. Results: Compared with their counterparts with high CR, PD individuals with low CR had reduced posterior DMN functional connectivity in the anterior cingulate and basal ganglia, and bilaterally reduced connectivity in fronto-parietal regions within the networks defined by the dorsolateral and ventrolateral prefrontal seeds. Hyper-connectivity was detected within medial prefrontal regions when comparing low-CR PD with low-CR controls. Conclusion: CR may exert a modulatory effect on functional connectivity in basal ganglia and executive-attentional fronto-parietal networks. In PD patients with low CR, attentional control networks seem to be downregulated, whereas higher recruitment of medial frontal regions suggests compensation via an upregulation mechanism. This upregulation might contribute to maintaining efficient cognitive functioning when posterior cortical function is progressively reduced
Posterior AD-Type pathology: Cognitive subtypes emerging from a cluster analysis
No full textBackground. "Posterior shift" of the neuropathological changes of Alzheimer's disease (AD) produces a syndrome (posterior cortical atrophy) (PCA) dominated by high-level visual deficits. Objective. To explore in patients with AD-type pathology whether a data-driven analysis (cluster analysis) based on neuropsychological findings resulted in the emergence of different subgroups of patients; in particular to find out whether it was possible to identify patients with visuospatial deficits consistent with the hypothesis that PCA is a "dorsal stream" syndrome or, rather, whether there were subgroups of patients with different types of impairment within the high-level visual domain. Methods. 23 PCA and 16 DAT patients were studied. By a principal component analysis performed on a wide range of neuropsychological tasks, 15 variables were obtained that loaded onto five main factors (memory, language, perceptual, visuospatial, and calculation) which entered a hierarchical cluster analysis. Results. Four clusters of cognitive impairment emerged: visuospatial/perceptual, memory, perceptual/calculation, and language. Only in the first cluster a visuospatial deficit clearly emerged. Conclusions. AD pathology produces not only variants dominated by memory (DAT) and, to a lesser extent, visuospatial deficit (PCA), but also other distinct syndromic subtypes with disorders in visual perception and language which reflect a different vulnerability of specific functional networks. © 2014 Antonella Cappa et al
Writing errors in primary progressive aphasia
No full textPeripheral errors in writing, that is errors produced download the spelling, have been occasionally described in primary progressive aphasia (PPA), but the possibility that these errors might be a marker of parkinsonism associated to some subtypes of PPA has not been explored. We investigated whether errors of peripheral nature characterize the writing disorder in PPA when associated with parkinsonian signs (PSs). Subgroups of PPA without PSs and with PSs were studied. The proportion of the central and peripheral errors in writing words and pseudowords was calculated in each group. In writing words, central errors significantly exceeded peripheral errors in subgroups without PSs. The higher the number of peripheral errors, the higher the probability of presenting PSs. No relation emerged between any error and the Unified Parkinson’s Disease Rating Scale, but both types of errors correlated with measures of cognitive ability. Peripheral errors emerge when PSs are associated with PPA and may be linked to a decay of the cognitive control on movement, possibly involving the right hemisphere. Peripheral errors have clinical relevance in PPA, to the extent that they may assume the significance of a marker of specific subtypes and can help to outline the specific clinical picture of individual patients
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