The Experts below are selected from a list of 32949 Experts worldwide ranked by ideXlab platform
Junichi Tsujii - One of the best experts on this subject based on the ideXlab platform.
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generalising Semantic Category disambiguation with large lexical resources for fun and profit
2014Co-Authors: Pontus Stenetorp, Sampo Pyysalo, Sophia Ananiadou, Junichi TsujiiAbstract:Background Semantic Category Disambiguation (SCD) is the task of assigning the appropriate Semantic Category to given spans of text from a fixed set of candidate categories, for example Protein to “Fibrin”. SCD is relevant to Natural Language Processing tasks such as Named Entity Recognition, coreference resolution and coordination resolution. In this work, we study machine learning-based SCD methods using large lexical resources and approximate string matching, aiming to generalise these methods with regard to domains, lexical resources and the composition of data sets. We specifically consider the applicability of SCD for the purposes of supporting human annotators and acting as a pipeline component for other Natural Language Processing systems.
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generalising Semantic Category disambiguation with large lexical resources for fun and profit
2014Co-Authors: Pontus Stenetorp, Sampo Pyysalo, Sophia Ananiadou, Junichi TsujiiAbstract:Semantic Category Disambiguation (SCD) is the task of assigning the appropriate Semantic Category to given spans of text from a fixed set of candidate categories, for example Protein to “Fibrin”. SCD is relevant to Natural Language Processing tasks such as Named Entity Recognition, coreference resolution and coordination resolution. In this work, we study machine learning-based SCD methods using large lexical resources and approximate string matching, aiming to generalise these methods with regard to domains, lexical resources and the composition of data sets. We specifically consider the applicability of SCD for the purposes of supporting human annotators and acting as a pipeline component for other Natural Language Processing systems. While previous research has mostly cast SCD purely as a classification task, we consider a task setting that allows for multiple Semantic categories to be suggested, aiming to minimise the number of suggestions while maintaining high recall. We argue that this setting reflects aspects which are essential for both a pipeline component and when supporting human annotators. We introduce an SCD method based on a recently introduced machine learning-based system and evaluate it on 15 corpora covering biomedical, clinical and newswire texts and ranging in the number of Semantic categories from 2 to 91. With appropriate settings, our system maintains an average recall of 99% while reducing the number of candidate Semantic categories on average by 65% over all data sets. Machine learning-based SCD using large lexical resources and approximate string matching is sensitive to the selection and granularity of lexical resources, but generalises well to a wide range of text domains and data sets given appropriate resources and parameter settings. By substantially reducing the number of candidate categories while only very rarely excluding the correct one, our method is shown to be applicable to manual annotation support tasks and use as a high-recall component in text processing pipelines. The introduced system and all related resources are freely available for research purposes at: https://github.com/ninjin/simsem .
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simsem fast approximate string matching in relation to Semantic Category disambiguation
2011Co-Authors: Pontus Stenetorp, Sampo Pyysalo, Junichi TsujiiAbstract:In this study we investigate the merits of fast approximate string matching to address challenges relating to spelling variants and to utilise large-scale lexical resources for Semantic class disambiguation. We integrate string matching results into machine learning-based disambiguation through the use of a novel set of features that represent the distance of a given textual span to the closest match in each of a collection of lexical resources. We collect lexical resources for a multitude of Semantic categories from a variety of biomedical domain sources. The combined resources, containing more than twenty million lexical items, are queried using a recently proposed fast and efficient approximate string matching algorithm that allows us to query large resources without severely impacting system performance. We evaluate our results on six corpora representing a variety of disambiguation tasks. While the integration of approximate string matching features is shown to substantially improve performance on one corpus, results are modest or negative for others. We suggest possible explanations and future research directions. Our lexical resources and implementation are made freely available for research purposes at: http://github.com/ninjin/simsem
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almost total recall Semantic Category disambiguation using large lexical resources and approximate string matching
2011Co-Authors: Pontus Stenetorp, Sampo Pyysalo, Sophia Ananiadou, Junichi TsujiiAbstract:Data set Mean Ambiguity Ambiguity Mean Recall Recall EPI 1.8/89.4% 1.3/92.4% 99.5% 99.4% ID 2.9/81.9% 1.9/88.1% 98.8% 98.6% GE 2.1/80.9% 1.7/84.5% 99.4% 99.5% SSC 2.0/50.0% 1.7/57.5% 99.6% 99.5% NLPBA 1.8/64.0% 1.6/68.0% 99.1% 99.1% SGREC 2.4/60.0% 2.0/66.7% 98.7% 98.6% Table: Performance by ambiguity level/reduction and recall for the mean over the learning curve and when all training and development data was used as training data Evaluation Datasets
Claude Alain - One of the best experts on this subject based on the ideXlab platform.
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orienting attention to short term memory representations via sensory modality and Semantic Category retro cues
2020Co-Authors: Kristina C Backer, Bradley R Buchsbaum, Claude AlainAbstract:There is growing interest in characterizing the neural mechanisms underlying the interactions between attention and memory. Current theories posit that reflective attention to memory representations generally involves a fronto-parietal attentional control network. The present study aimed to test this idea by manipulating how a particular short-term memory (STM) representation is accessed, that is, based on its input sensory modality or Semantic Category, during functional magnetic resonance imaging (fMRI). Human participants performed a novel variant of the retro-cue paradigm, in which they were presented with both auditory and visual non-verbal stimuli followed by Modality, Semantic, or Uninformative retro-cues. Modality and, to a lesser extent, Semantic retro-cues facilitated response time relative to Uninformative retro-cues. The univariate and multivariate pattern analyses (MVPAs) of fMRI time-series revealed three key findings. First, the posterior parietal cortex (PPC), including portions of the intraparietal sulcus (IPS) and ventral angular gyrus (AG), had activation patterns that spatially overlapped for both modality-based and Semantic-based reflective attention. Second, considering both the univariate and multivariate analyses, Semantic retro-cues were associated with a left-lateralized fronto-parietal network. Finally, the experimental design enabled us to examine how dividing attention cross-modally within STM modulates the brain regions involved in reflective attention. This analysis revealed that univariate activation within bilateral portions of the PPC increased when participants simultaneously attended both auditory and visual memory representations. Therefore, prefrontal and parietal regions are flexibly recruited during reflective attention, depending on the representational feature used to selectively access STM representations.
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orienting attention to short term memory representations via sensory modality and Semantic Category retro cues
2020Co-Authors: Kristina C Backer, Bradley R Buchsbaum, Claude AlainAbstract:There is growing interest in characterizing the neural mechanisms underlying the interactions between attention and memory. Current theories posit that reflective attention to memory representations generally involves a fronto-parietal attentional control network. The present study aimed to test this idea by manipulating how a particular short-term memory (STM) representation is accessed – that is, based on its input sensory modality or Semantic Category – during functional magnetic resonance imaging (fMRI). Human participants performed a novel variant of the retro-cue paradigm, in which they were presented with both auditory and visual non-verbal stimuli followed by Modality, Semantic, or Uninformative retro-cues. Modality and, to a lesser extent, Semantic retro-cues facilitated response time relative to Uninformative retro-cues. The univariate and multivariate pattern analyses of fMRI time-series revealed three key findings. First, the Posterior Parietal Cortex (PPC), including portions of the Intraparietal Sulcus (IPS) and ventral Angular Gyrus (AG), had activation patterns that spatially overlapped for both Modality-based and Semantic-based reflective attention. Second, considering both the univariate and multivariate analyses, Semantic retro-cues were associated with a left-lateralized fronto-parietal network. Finally, the experimental design enabled us to examine how dividing attention cross-modally within STM modulates the brain regions involved in reflective attention. This analysis revealed that univariate activation within bilateral portions of the PPC increased when participants simultaneously attended both auditory and visual memory representations. Therefore, prefrontal and parietal regions are flexibly recruited during reflective attention, depending on the representational feature used to selectively access STM representations. Significance Statement This functional magnetic resonance imaging (fMRI) study sought to examine similarities and differences in neural activity when concrete (sensory modality) and abstract (Semantic Category) information is used to guide attention to short-term memory representations of non-verbal stimuli. The posterior parietal cortex (especially portions of Intraparietal Sulcus and left ventral Angular Gyrus (AG)) had activation patterns that were specific to both modality- and Semantic-based reflective attention. Semantic-based reflective attention also recruited additional left-lateralized prefrontal regions and dorsolateral AG. Furthermore, dividing attention across sensory domains within memory was associated with stronger activation within the dorsomedial posterior parietal cortex. Thus, attentional orienting to memory flexibly recruits prefrontal and parietal regions as necessary, depending on the information used to selectively access memory representations.
Alfonso Caramazza - One of the best experts on this subject based on the ideXlab platform.
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what are the facts of Semantic Category specific deficits a critical review of the clinical evidence
2003Co-Authors: Erminio Capitani, Marcella Laiacona, Bradford Z Mahon, Alfonso CaramazzaAbstract:In this study we provide a critical review of the clinical evidence available to date in the field of Semantic Category-specific deficits. The motivation for undertaking this review is that not all the data reported in the literature are useful for adjudicating among extant theories. This project is an attempt to answer two basic questions: (1) what are the categories of Category-specific deficits, and (2) is there an interaction between impairment for a type of knowledge (e.g., visual, functional, etc.) and impairment for a given Category of objects (e.g., biological, artefacts, etc.). Of the 79 case studies in which the reported data are sufficiently informative with respect to the aims of our study, 61 presented a disproportionate impairment for biological categories and 18 presented a disproportionate impairment for artefacts. Less than half of the reported cases provide statistically and theoretically interpretable data. Each case is commented upon individually. The facts that emerge from our critical review are that (1) the categories of Category-specific Semantic deficits are animate objects, inanimate biological objects, and artefacts (the domain of biological objects fractionates into two independent Semantic categories: animals, and fruit/ vegetables); (2) the types of Category-specific deficits are not associated with specific types of conceptual knowledge deficits. Other conclusions that emerge from our review are that the evidence in favour of the existence of cases of reliable Category-specific agnosia or anomia is not very strong, and that the visual structural description system functions relatively autonomously from conceptual knowledge about object form.
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minding the facts a comment on thompson schill et al s a neural basis for Category and modality specificity of Semantic knowledge
2000Co-Authors: Alfonso CaramazzaAbstract:In this comment on a recent paper by Thompson-Schill et al. (1999) I argue that the authors failed to consider important empirical facts that are at variance with their favored theory of the causes of Semantic Category-specific deficits. I also argue that the predictions they make about fusiform gyrus activation on the basis of the interactive modality-specific hypothesis of Semantic organization do not obviously follow from that model. I point out that simulations are needed in order to derive predictions from the model. Finally, I argue that the fMRI results they obtained are not obviously relevant to our understanding of the causes of Semantic Category-specific deficits.
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the interpretation of Semantic Category specific deficits what do they reveal about the organization of conceptual knowledge in the brain
1998Co-Authors: Alfonso CaramazzaAbstract:Abstract What does the existence of Semantic Category-specific deficits tell us about the organization of conceptual knowledge in the brain? Do these deficits reflect the existence of specialized mechanisms for the recognition and storage of specific Semantic categories? Or do they merely reflect differences In the correlational structure of the properties that define concepts in different Semantic domains? The received explanations of Category-specific deficits have adopted a reductionist perspective, appealing to some or other non-categorical principle to explain the disorder. Some have appealed to the relative importance of the visual properties of objects in distinguishing among members of a Semantic Category; others have appealed to the relative strengths of correlations between visual and functional properties in different categories. However, there is also a proposal that Semantic Category-specific deficits reflect the fact that conceptual knowledge is organized into broad Semantic domains. These p...
Marta Kutas - One of the best experts on this subject based on the ideXlab platform.
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The impact of Semantic memory organization and sentence context information on spoken language processing by younger and older adults: An ERP study
2002Co-Authors: Kara D. Federmeier, Devon B. Mclennan, Esmeralda De Ochoa, Marta KutasAbstract:To examine changes in Semantic memory organization and use during aging, we recorded event-related potentials as younger and older adults listened to sentences ending with the expected word, an unexpected word from the same Semantic Category, or an unexpected word from a different Category. Half of the contexts were highly constraining. In both groups, expected words elicited less negativity 300–500 ms ~N400! than unexpected ones, and unexpected words elicited smaller N400s when these were categorically related. Whereas younger adults showed the greatest N400 reduction to unexpected but related words in high constraint contexts, older adults showed the opposite tendency. Thus, unlike younger adults, older adults as a group do not seem to be using context predictively. Older adults with higher verbal fluency and larger vocabularies, however, showed the younger response pattern, suggesting resource availability may offset certain age-related changes.
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effects of transient mild mood states on Semantic memory organization and use an event related potential investigation in humans
2001Co-Authors: Kara D. Federmeier, Donald A Kirson, Eva Maria Olmedo Moreno, Marta KutasAbstract:The effects of transient mood states on Semantic memory organization and use were investigated using event-related potentials. Participants read sentence pairs ending with (1) the most expected word, (2) an unexpected word from the expected Semantic Category, or (3) an unexpected word from a different (related) Category; half the pairs were read under neutral mood and half under positive mood. Under neutral mood, N400 amplitudes were smallest for expected items and smaller for unexpected items when these came from the expected Category. In contrast, under positive mood, N400 amplitudes to the two types of unexpected items did not differ. Positive mood seemed to specifically facilitate the processing of distantly-related, unexpected items. The results suggest that transient mood states are associated with dynamic changes in how Semantic memory is used on-line.
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meaning and modality influences of context Semantic memory organization and perceptual predictability on picture processing
2001Co-Authors: Kara D. Federmeier, Marta KutasAbstract:: Using event-related potentials (ERPs), the authors investigated the influences of sentence context, Semantic memory organization, and perceptual predictability on picture processing. Participants read pairs of highly or weakly constraining sentences that ended with (a) the expected item, (b) an unexpected item from the expected Semantic Category, or (c) an unexpected item from an unexpected Category. Pictures were unfamiliar in Experiment 1 but preexposed in Experiment 2. ERPs to pictures reflected both contextual fit and memory organization, as do ERPs to words in the same contexts (K. D. Federmeier & M. Kutas, 1999). However, different response patterns were observed to pictures than to words. Some of these arose from perceptual predictability differences, whereas others seem to reflect true modality-based differences in Semantic feature activation. Although words and pictures may share Semantic memory, the authors' results show that Semantic processing is not amodal.
Erminio Capitani - One of the best experts on this subject based on the ideXlab platform.
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posterior cerebral artery infarcts and Semantic Category dissociations a study of 28 patients
2009Co-Authors: Erminio Capitani, Marcella Laiacona, R Pagani, Rita Capasso, Patrizia Zampetti, Gabriele MiceliAbstract:In this study we analysed the relationship between damage in the territory of the posterior cerebral artery and Semantic knowledge, with special reference to Category dissociations. Twenty-eight posterior cerebral artery stroke patients (18 left, 8 right and 2 bilateral posterior cerebral artery infarctions) completed a neuropsychological battery aimed at assessing Semantic knowledge. The battery included picture naming, word-picture matching, a verbal Semantic questionnaire and a picture reality decision task. For each participant, the lesion was reconstructed on the basis of MRI images, and was classified according to the involvement of the areas supplied by posterior cerebral artery. Defective naming scores were observed in 12 of 18 left posterior cerebral artery cases (67%), four of eight right posterior cerebral artery cases (50%), and one of two bilateral posterior cerebral artery cases (50%). Only in the bilateral posterior cerebral artery lesion case did we observe the pattern expected in pure visual agnosia, i.e. poor picture naming, poor picture reality decision, and normal verbal Semantic questionnaire. Nine left posterior cerebral artery cases and two right posterior cerebral artery cases presented with poor performance on both the picture naming task and the verbal Semantic questionnaire, thus suggesting Semantic impairment. For 5 of the 12 left posterior cerebral artery patients who fared poorly on the naming task, biological stimuli (overall) were significantly more impaired than artifacts. In three of these five subjects, performance on plant-life stimuli was significantly less accurate than that on animals. A further left posterior cerebral artery patient presented a disproportionate impairment on plant-life stimuli only on the word-picture matching and on the questionnaire. The patterns of performance in these subjects suggest that the observed dissociations originated at the Semantic level. Among left posterior cerebral artery patients, a naming deficit only occurred when damage to the fusiform gyrus extended anterior to Talairach's y-coordinate -50, and a disproportionate impairment of biological categories only when the lesion extended anterior to y = -32.5. Results show that the Semantic deficit for the Category of plant life is a genuine cognitive pattern, and does not depend on loss of colour knowledge. The contrast of left posterior cerebral artery strokes and herpes simplex encephalitis cases shows that the neural substrates for the Semantic representation of plant life and animals are, at least in part, distinct. Middle and posterior portions of the left fusiform are crucial for the representation of plant-life knowledge, whereas left anterior temporal areas are more crucial than left posterior and basal temporal areas for the representation of knowledge about animals.
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what are the facts of Semantic Category specific deficits a critical review of the clinical evidence
2003Co-Authors: Erminio Capitani, Marcella Laiacona, Bradford Z Mahon, Alfonso CaramazzaAbstract:In this study we provide a critical review of the clinical evidence available to date in the field of Semantic Category-specific deficits. The motivation for undertaking this review is that not all the data reported in the literature are useful for adjudicating among extant theories. This project is an attempt to answer two basic questions: (1) what are the categories of Category-specific deficits, and (2) is there an interaction between impairment for a type of knowledge (e.g., visual, functional, etc.) and impairment for a given Category of objects (e.g., biological, artefacts, etc.). Of the 79 case studies in which the reported data are sufficiently informative with respect to the aims of our study, 61 presented a disproportionate impairment for biological categories and 18 presented a disproportionate impairment for artefacts. Less than half of the reported cases provide statistically and theoretically interpretable data. Each case is commented upon individually. The facts that emerge from our critical review are that (1) the categories of Category-specific Semantic deficits are animate objects, inanimate biological objects, and artefacts (the domain of biological objects fractionates into two independent Semantic categories: animals, and fruit/ vegetables); (2) the types of Category-specific deficits are not associated with specific types of conceptual knowledge deficits. Other conclusions that emerge from our review are that the evidence in favour of the existence of cases of reliable Category-specific agnosia or anomia is not very strong, and that the visual structural description system functions relatively autonomously from conceptual knowledge about object form.
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Semantic Category dissociations in naming is there a gender effect in alzheimer s disease
1998Co-Authors: Marcella Laiacona, Riccardo Barbarotto, Erminio CapitaniAbstract:Several studies on picture naming in Alzheimer's disease have reported inconsistent findings regarding Semantic Category dissociation. To clarify this point, 26 patients suffering from dementia of the Alzheimer's type (DAT) were given a naming task, based on 60 black and white drawings, which allowed us to take into account several variables that might influence performance, notably word frequency, stimulus familiarity and prototypicality, name and image agreement and visual complexity. On a raw analysis, DAT patients as a group gave a lower performance with stimuli of Living Categories (LC) than with stimuli of Non-Living Categories (NLC), but when all the confounding factors were taken into account the Category effect disappeared. Nevertheless, with a multiple single case approach, some patients presented a true dissociation: 11 were significantly better with Non-Living stimuli, and 3 with Living stimuli. In order to find what factors were involved in determining this distribution, we took the distribution of asymmetry indices of each patient, and plotted the individual Category effect against the level of the general performance. In our sample, the distribution of asymmetry indices was skewed, and included a definite cluster of male subjects who were better at performing with Non-Living stimuli. Multivariate analysis suggested that the greater discrepancy shown by male patients was due to a protection acting on Non-Living stimuli rather than to a selective hampering of Living stimuli. The greater personal experience of males with Non-Living things could explain the relative preservation of these in male DAT subjects.
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Semantic Category dissociations a longitudinal study of two cases
1997Co-Authors: Marcella Laiacona, Erminio Capitani, Riccardo BarbarottoAbstract:We report the neuropsychological findings of two patients (LF and EA) with herpes simplex encephalitis. Both patients presented a greater deficit for living than non-living categories in a number of tasks, although EA was much more impaired than LF. We controlled the several stimulus variables that might affect the performance and could demonstrate that the dissociation was not artifactual. Neither LF nor EA revealed a selective or preferential involvement of perceptual Semantic knowledge, and both showed a homogeneous impairment of perceptual and associative encyclopaedic notions. At a second examination, carried out from 1 to 2 years later, LF showed a good recovery, whereas EA's improvement was confined to the non-living categories. The lesion of both patients affected the left temporal pole and the basal neocortical regions of the left temporal lobe. The involvement of limbic areas was more marked in LF, while the Wernicke area and the posterior parts of the middle and inferior temporal gyri were only involved in EA. Besides the basal temporal areas, also the posterior temporal regions are likely to play a role in determining the clinical picture of such patients, and their prospect of recovery.
