1,721,082 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
Neuropsychological correlates of localized cerebral lesions in non-aphasic brain-damaged patients
No full textA neuropsychological test battery made up of verbal, visual-spatial, and intelligence tests was administered to 82 right and 67 on-aphasic left brain-damaged patients with localized cerebral lesions, in order to draw impairment profiles of the various subgroups. Separate analyses were undertaken on patients with unilobar and multilobar lesions. As for hemisphere effects, LH patients performed worse than RH subjects on verbal tests, while the reverse was true for visual-spatial tasks. As for lobe effects, patients with frontal lobe damage fared worse than other subgroups on word fluency, independent of the side of the lesion. RH patients with multilobar posterior lesions were significantly more impaired than other RH subgroups on the test of Copying Drawings with Landmarks, probably owing to the detrimental effect of unilateral spatial neglect on tasks requiring an accurate visual-spatial analysis
Toista tasoa korkeammalle transmonhiloissa: perustilafaasit ja dynamiikka
No full textAbstractSuperconducting qubits are one of the most promising platforms for the construc-tion of quantum computers. The state-of-the-art qubits and associated control gates are unfortunately still too prone to errors for general purpose quantum computing to be feasible. However, the circuits used to build the qubits can already be utilised in analogue quantum simulation. That is, they can be used as a building block of relatively simple and easy to control quantum mechanical device, used to emulate some aspects of more complicated systems. Here we focus specifically on the transmon, which is currently the most common qubit design. The few lowest energy levels of transmons can be described as an anharmonic oscillator. While the anharmonicity allows the two lowest levels to be used as a qubit, that does not mean that the higher levels should necessarily be neglected. Beyond the two-level approximation, the behaviour of transmon arrays can be well approximated with the Bose–Hubbard model with attractive interactions. Here we discuss analytical and numerical studies of the model, focusing on the higher excited levels of transmons.We begin by constructing ground state phase diagrams of the attractive model for constant numbers of bosons, including the effect of disorder, an unavoidable feature of manufactured devices. In the phase diagrams we find three distinct phases: the localised phase at strong disorder, the superfluid phase at high hopping frequencies, and the W phase when both disorder and hopping are dominated by the attractive interactions. Next, we study the dynamics of the model, utilising the wide-gapped band structure of the Bose–Hubbard spectrum. We describe the dynamics within each band with a compact and unified framework based on high-order degenerate perturbation theory. The unitary dynamics effectively occur within a single band, resulting in various forms of collective behaviour, such as bosons on a single site moving as a single quasiparticle and effective longer-range interactions between multiple quasiparticles. Finally, to account for the imperfect isolation of the transmons from their environment, we include dissipation and dephasing into our model of the dynamics. We provide analytical descriptions on how the environment affects the dynamics within the bands, and causes transitions between them.Original papersOriginal papers are not included in the electronic version of the dissertation.Mansikkamäki, O., Laine, S., & Silveri, M. (2021). Phases of the disordered Bose-Hubbard model with attractive interactions. Physical Review B, 103(22), L220202. https://doi.org/10.1103/PhysRevB.103.L220202Self-archived versionMansikkamäki, O., Laine, S., Piltonen, A., & Silveri, M. (2022). Beyond hard-core bosons in transmon arrays. PRX Quantum, 3(4), 040314. https://doi.org/10.1103/PRXQuantum.3.040314Self-archived versionBusel, O., Laine, S., Mansikkamäki, O., & Silveri, M. (2023). Dissipation and dephasing of interacting photons in transmon arrays. Manuscript submitted for publication.OsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Mansikkamäki, O., Laine, S., & Silveri, M. (2021). Phases of the disordered Bose-Hubbard model with attractive interactions. Physical Review B, 103(22), L220202. https://doi.org/10.1103/PhysRevB.103.L220202Rinnakkaistallennettu versioMansikkamäki, O., Laine, S., Piltonen, A., & Silveri, M. (2022). Beyond hard-core bosons in transmon arrays. PRX Quantum, 3(4), 040314. https://doi.org/10.1103/PRXQuantum.3.040314Rinnakkaistallennettu versioBusel, O., Laine, S., Mansikkamäki, O., & Silveri, M. (2023). Dissipation and dephasing of interacting photons in transmon arrays. Manuscript submitted for publication.Academic Dissertation to be presented with the assent of the Doctoral Training
Committee of Technology and Natural Sciences of the University of Oulu, for
public discussion in Auditorium L6, on April 21st, 2023, at 12 o’clock noonAbstract
Superconducting qubits are one of the most promising platforms for the construc-tion of quantum computers. The state-of-the-art qubits and associated control gates are unfortunately still too prone to errors for general purpose quantum computing to be feasible. However, the circuits used to build the qubits can already be utilised in analogue quantum simulation. That is, they can be used as a building block of relatively simple and easy to control quantum mechanical device, used to emulate some aspects of more complicated systems. Here we focus specifically on the transmon, which is currently the most common qubit design. The few lowest energy levels of transmons can be described as an anharmonic oscillator. While the anharmonicity allows the two lowest levels to be used as a qubit, that does not mean that the higher levels should necessarily be neglected. Beyond the two-level approximation, the behaviour of transmon arrays can be well approximated with the Bose–Hubbard model with attractive interactions. Here we discuss analytical and numerical studies of the model, focusing on the higher excited levels of transmons.
We begin by constructing ground state phase diagrams of the attractive model for constant numbers of bosons, including the effect of disorder, an unavoidable feature of manufactured devices. In the phase diagrams we find three distinct phases: the localised phase at strong disorder, the superfluid phase at high hopping frequencies, and the W phase when both disorder and hopping are dominated by the attractive interactions. Next, we study the dynamics of the model, utilising the wide-gapped band structure of the Bose–Hubbard spectrum. We describe the dynamics within each band with a compact and unified framework based on high-order degenerate perturbation theory. The unitary dynamics effectively occur within a single band, resulting in various forms of collective behaviour, such as bosons on a single site moving as a single quasiparticle and effective longer-range interactions between multiple quasiparticles. Finally, to account for the imperfect isolation of the transmons from their environment, we include dissipation and dephasing into our model of the dynamics. We provide analytical descriptions on how the environment affects the dynamics within the bands, and causes transitions between them
The influence of semantic and perceptual factors on lexical comprehension in aphasics and right brain-damaged subjects
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