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PubMed1991

Semantic networks of English.

Principles of lexical semantics developed in the course of building an on-line lexical database are discussed. The approach is relational rather than componential. The fundamental semantic relation is synonymy, which is required in order to define the lexicalized concepts that words can be used to express. Other semantic relations between these concepts are then described. No single set of semantic relations or organizational structure is adequate for the entire lexicon: nouns, adjectives, and verbs each have their own semantic relations and their own organization determined by the role they must play in the construction of linguistic messages.

Attention↗

PubMed1988

Semantic relationships and medical bibliographic retrieval: a preliminary assessment.

This paper describes a project exploring whether semantic relationships between bibliographic terms may effectively partition the clinical literature. To address this question, a set of semantic relationships was identified between pairs of bibliographic terms taken from four categories: (1) diseases, (2) treatments, (3) tests, and (4) patient characteristics. The MEDLINE system of the National Library of Medicine was used to generate lists of abstracts relating to pairs of clinical terms. Each list of abstracts was examined to identify the semantic relationships, if any, which applied to the two terms in each paper. The study suggests that semantic relationships may play a potentially valuable role in assisting computer-based medical bibliographic retrieval. The degree to which relationships partition the literature is strongly dependent on the underlying semantics of the particular bibliographic terms involved.

Information Systems↗

PubMed1985

Event-related potentials associated with the discrimination of acoustic and semantic aspects of speech.

Analysis of a word's acoustic structure must precede identification of its meaning. Therefore, these aspects of speech processing could be associated with event-related potential (ERP) components that differed in their timing. To identify electrophysiologic indices of the cortical processing of acoustic and semantic features of speech, we recorded ERPs to the random presentation of nonsense or real words in four conditions designed to manipulate the extent to which the speech sounds were processed. In one condition subjects responded to all stimuli; in a second and third, to a designated nonsense or real word; and in the final condition to words within a specified semantic category. To define the cortical activity associated with acoustic processing, ERPs obtained when no discrimination was required were subtracted from those recorded during the identification of a specified speech target. The difference waveforms exhibited a negative potential that began about 50 msec after stimulus onset and lasted about 200 msec. Difference waveforms obtained by subtracting the non-discrimination ERP from those obtained during semantic discrimination exhibited a negative potential with similar onset timing. We concluded that the early negative potential indexed acoustic processes necessary for stimulus identification. To identify potentials associated with determination of a word's meaning, we subtracted the verbal discrimination from the semantic discrimination ERPs. This difference waveform exhibited a later negativity beginning at 150 msec and lasting about 250 msec. This potential may be related to the semantic processing of speech.

Adolescent↗

PubMed1992

Cerebral blood flow correlates of word monitoring in sentences: influence of semantic incoherence. A spect study in normals.

The aim of this study was to assess the cerebral blood flow (CBF) changes induced by the semantic incoherence of sentences whose words were to be monitored by the subjects. According to Marslen-Wilson and Tyler, word processing would be parallel (global) in semantically coherent sentences, and serial (local) in semantically incoherent ones. We hypothesized that, in comparison with the parallel mode, the serial mode of word processing would result in a preponderant activation of the frontal lobes and/or of the left hemisphere, hence in a flow increase in these regions. In addition, one could assume that the increase in task complexity resulting from the breaking of semantic coherence would reinforce the functional links between hemispheres. Furthermore, as interactions between the processing of semantically coherent vs incoherent of verbal materials and the processing of imageable vs non-imageable stimuli was recently suspected, we designed a study combining coherent vs incoherent sentences and imageable vs non-imageable words. The results we obtained in 12 normal volunteers by measuring regional cerebral blood flow by SPECT and IV injection of Xenon 133 during the four experimental conditions, did not allow us to firmly establish our hypotheses. Indeed, we failed to demonstrate any significant CBF changes across conditions and there was no interaction between coherent vs incoherent and imageable vs non-imageable conditions. However, the analysis of the inter-regional correlations pointed to an increase in the functional links between the hemispheres in the incoherent conditions, whatever the imageability.

Adult↗

PubMed1996

Living/non-living dissociation in a case of semantic dementia: a SPECT activation study.

A category-specific dissociation with massive deficits in semantic knowledge of animals and preservation of knowledge of objects was observed in a demented patient with a left inferior temporal cortical atrophy responsible for a deficit of visual semantic processing. When the patient successfully processed the semantic feature of aurally presented object names, a SPECT study showed an activation of the left posterior and middle temporal cortex (Wernicke's area). This haemodynamic pattern was not observed during an unsuccessful processing of animal names that was associated with an activation of the left and right inferior frontal regions. Activation in Wernicke's area probably reflects an adequate matching between auditory lexical input and semantic knowledge for entities with multimodal representations, such as man-made objects. Activation in Broca's area and its right homologous region may correspond to an unsuccessful phonological strategy to evoke semantic features of animals, a category that is mainly visually represented.

Aged↗

PubMed1989

Syntactic and semantic contributions to sentence comprehension in agrammatism.

Five aphasic subjects, who demonstrated agrammatic speech, and eight control subjects were presented with a sentence-picture matching task in which the factors of syntactic complexity, semantic reversibility, and sentence plausibility were independently varied. A subset of the sentences was patterned after that presented by A. Caramazza and E. Zurif (1976, Brain and Language, 5, 572-583) who concluded that Broca's aphasics rely on semantic constraints instead of syntactic information for sentence comprehension. Our aphasic subjects showed the same pattern of performance on this subset of sentences. However, the results from the full set of sentence materials we tested show that the aphasic subjects could perform some sentence level syntactic analyses, even when syntactic information conflicted with semantic constraints. The aphasic subjects correctly interpreted most active and passive sentences. They failed, however, to assign thematic roles and adjectives in center-embedded relative sentences, and instead relied on nonsyntactic information. These results show that both semantic and syntactic information contributed to sentence comprehension in the aphasic subjects we tested, in contrast to previous claims that syntactic and semantic processes are completely dissociated in this population.

Aged↗

PubMed1990

Semantic and associative priming in the cerebral hemispheres: some words do, some words don't ... sometimes, some places.

This study investigated spreading activation for words presented to the left and right hemispheres using an automatic semantic priming paradigm. Three types of semantic relations were used: similar-only (Deer-Pony), associated-only (Bee-Honey), and similar + associated (Doctor-Nurse). Priming of lexical decisions was symmetrical over visual fields for all semantic relations when prime words were centrally presented. However, when primes and targets were lateralized to the same visual field, similar-only priming was greater in the LVF than in the RVF, no priming was obtained for associated-only words, and priming was equivalent over visual fields for similar + associated words. Similar results were found using a naming task. These findings suggest that it is important to lateralize both prime and target information to assess hemisphere-specific spreading activation processes. Further, while spreading activation occurs in either hemisphere for the most highly related words (those related by category membership and association), our findings suggest that automatic access to semantic category relatedness occurs primarily in the right cerebral hemisphere. These results imply a unique role for the right hemisphere in the processing of word meanings. We relate our results to our previous proposal (Burgess & Simpson, 1988a; Chiarello, 1988c) that there is rapid selection of one meaning and suppression of other candidates in the left hemisphere, while activation spreads more diffusely in the right hemisphere. We also outline a new proposal that activation spreads in a different manner for associated words than for words related by semantic similarity.

Adult↗

PubMed1991

The effects of semantic and phonemic prestimulation cues on picture naming in aphasia.

In this study of auditory prestimulation cues, picture naming performances under phonemic and semantic conditions were compared to picture naming performance under a neutral condition. Twenty aphasic subjects named 324 pictures (108 pictures x 3 conditions) each. Responses were scored using a coding system adapted by the investigator from classification systems used by Williams and Canter (1982) and Kohn and Goodglass (1985). Results indicated that naming accuracy was facilitated by phonemic and semantic cues. An examination of the distribution of errors under the three conditions revealed systematic effects of phonemic and semantic cues on the frequency of occurrence of specific error types. Increases in semantic paraphasia proportion scores and decreases in unrelated word error proportion scores were associated with the semantic condition, while increases in phonemic paraphasia proportion scores were associated with the phonemic condition. The finding that naming performance of aphasic adults varies as a function of the type of information provided by the cue is discussed in relation to cascade visual confrontation naming models.

Adult↗

PubMed1988

The impaired learning of semantic knowledge following bilateral medial temporal-lobe resection.

The integrity of several aspects of semantic memory (including knowledge of the meaning, lexical status, perception, and pronunciation of words and famous names) was examined in H.M., a patient with anterograde amnesia following bilateral medial temporal-lobe excision. Despite normal memory for such semantic knowledge acquired prior to the onset of his amnesia in 1953, H.M. showed a severe deficit in memory for semantic information encountered subsequently. In combination with the previously reported impairments in new learning shown by H.M., the deficits observed here point to an association between semantic and episodic memory, and do not lend support to a distinction between them. The acquisition of semantic and episodic information, therefore, appears to depend upon a common memory system that requires the intact functioning of medial temporal-lobe structures.

Aged↗

PubMed1989

Face processing and name retrieval in an anomic aphasic: names are stored separately from semantic information about familiar people.

Recent models of face recognition have proposed that the names of familiar people are accessed from a lexical memory store that is distinct from the semantic memory store that holds information about such things as a familiar person's occupation and personality. Names are nevertheless retrieved via the semantic system. If such models are correct, then it should be possible for a patient to have full access to semantic information about familiar people while being unable to name many of them. We report this pattern in an anomic aphasic patient, EST, whose inability to recall the names of familiar people occurred in the context of a general word-finding problem. EST showed a preserved ability to access semantic information from familiar faces, voices, and spoken and written names and to process facial expressions, but he was unable to name many familiar faces. These findings are compatible with current models of face processing and challenge models which propose that names are stored alongside semantic information in a general-purpose long-term memory store.

Anomia↗

PubMed1990

Event-related potentials and the semantic matching of pictures.

Event-related potentials (ERPs) were recorded from one midline and three pairs of lateral electrodes while subjects determined whether pairs of sequentially presented pictures were semantically associated. The ERPs evoked by the second picture of each pair differed as a consequence of whether it was associated with its predecessor, such that ERPs to nonassociated pictures were more negative-going than those to associated items. These differences resulted from the modulation of two ERP components, one frontally distributed and centered on an N300 deflection, the other distributed more widely over the scalp and encompassing an N450 deflection. The modulation of N450 is interpreted as further evidence that the "N400" ERP component is sensitive to semantic relationships between nonverbal stimuli. The earlier N300 effects, which do not appear to occur when ERPs are evoked by semantically primed and unprimed words, could suggest that the semantic processing of pictorial stimuli involves neural systems different from those associated with the semantic processing of words.

Adolescent↗

PubMed1995

The roles of semantic networks and search efficiency in verbal fluency performance in intractable temporal lobe epilepsy.

Two competing hypotheses (i.e., disruption of semantic networks vs. search inefficiency) concerning the mechanisms underlying impaired semantic verbal fluency in temporal lobe epilepsy (TLE) were tested within a single paradigm. Reports that semantic verbal fluency is more impaired in left than right TLE groups were confirmed by the findings that the left TLE group produced fewer words on a supermarket fluency task than did the normal control (NC) group, and that the performance of the right TLE group was intermediate to that of the left TLE and NC groups. Because both TLE groups generated fewer words per category of supermarket items sampled, and produced a higher ratio of category labels relative to category exemplars than did the NC group, it can be surmised that TLE disrupts semantic memory networks. The findings did not support the competing hypothesis that reduced semantic verbal fluency in TLE is a manifestation of inefficient search/retrieval strategies, possibly associated with distal frontal lobe pathophysiology. Specifically, the TLE and NC groups did not differ significantly in their mean number of perseverations, intrusions, or search efficiency (operationalized as the ratio of the number of shifts between categories to the number of categories sampled).

Adult↗

PubMed2005

Models of high-dimensional semantic space predict language-mediated eye movements in the visual world.

In the visual world paradigm, participants are more likely to fixate a visual referent that has some semantic relationship with a heard word, than they are to fixate an unrelated referent [Cooper, R. M. (1974). The control of eye fixation by the meaning of spoken language. A new methodology for the real-time investigation of speech perception, memory, and language processing. Cognitive Psychology, 6, 813-839]. Here, this method is used to examine the psychological validity of models of high-dimensional semantic space. The data strongly suggest that these corpus-based measures of word semantics predict fixation behavior in the visual world and provide further evidence that language-mediated eye movements to objects in the concurrent visual environment are driven by semantic similarity rather than all-or-none categorical knowledge. The data suggest that the visual world paradigm can, together with other methodologies, converge on the evidence that may help adjudicate between different theoretical accounts of the psychological semantics.

Eye Movements↗

PubMed2003

Auditory lexical-semantic processing impairments in aphasic patients reflected in event-related potentials (N400).

OBJECTIVE: Event-related potentials (ERPs) and response latencies were recorded from aphasic subjects with auditory language processing impairments and age-matched normal controls, while performing a lexical-semantic evaluation task, aiming at clarifying whether ERPs could be a reliable measure for indicating language impairments in aphasic patients. METHODS: The stimuli were 50 pairs of spoken words (prime word-target word): 25 pairs, which were semantically and/or associatively related to each other, and 25 pairs which were not. The subjects pressed a switch in response to the presentation of target words semantically related to the prime words. The ERP component analyzed in this study was N400. RESULTS: With the performances, the response latencies were longer in the aphasic subjects than in the normal controls. With the ERPs, onset latencies of N400 were shifted behind in the aphasic patients compared to the normal controls. For the aphasic patients, there were correlations between the size of N400 and performances in auditory comprehension evaluated in the aphasia test. CONCLUSION: The conclusions drawn from the results are that not only response latencies in the lexical-semantic judgement task, but also N400 effects, may be a reliable clinical measure of the severity of even mild lexical-semantic impairments in aphasic patients.

Acoustic Stimulation↗

PubMed2006

Mémoire: A framework for semantic interoperability of case-based reasoning systems in biology and medicine.

OBJECTIVE: Mémoire is a framework for sharing and distributing case bases and case-based reasoning (CBR) systems in biology and medicine. METHODS AND MATERIAL: This paper first introduces the semantic Web approach to build a better Web where search engines, knowledge sources and servers, applications and services can live, work, and learn in cooperation. This semantic approach is particularly well suited for biomedical domains because significant ontologies have been developed there and constitute a sound basis for the standardization effort required for the semantic Web. Case-based reasoning systems in biomedicine have also benefited from these biomedical ontologies and models. RESULTS: This article demonstrates for three such systems how a semantics infused approach in CBR gives better, more accurate results in CBR. From this previous work on a semantic approach in CBR in biomedicine, the Mémoire framework has evolved. CONCLUSION: Mémoire proposes a unified OWL-based representation language for cases and case-based ontologies in biomedicine, where a Web Ontology Language (OWL) is a language to represent ontologies on the Web. Mémoire provides a set of tools for building case-based reasoning systems compliant with its language. Mémoire is extensible and can be adapted to different types of biomedical application domains, tasks, and environments. Mémoire will permit bridging the gap within the multiple case-based reasoning systems dedicated to a single domain, and make available to agents and Web services the case-based competency of the CBR systems adopting its interchange language. The approach could be extended to other application domains of CBR.

Artificial Intelligence↗

PubMed2004

Can semantic information be transferred between hemispheres in the split-brain?

Data from experiments with split-brain patients, who have had their left and right hemispheres disconnected, suggests a remarkable specialization of function within each hemisphere. At the same time, these patients conduct their daily lives with great proficiency. This ability suggests that some information integral to coordinated function between the hemispheres is available in the absence of the corpus callosum. Is information about the semantics of words one type of information that is shared? An experiment by suggests that it may be. Lambert reported that living/nonliving word categorization was delayed when disconnected hemispheres processed words belonging to the same category. Although other interpretations are plausible, Lambert described this effect as having a semantic source. We attempted to replicate the original effect with two additional split-brain patients, J.W. and V.P., and to extend the original design to clarify the source of the putative semantic effect. Our results indicate that any semantic interaction between the split hemispheres is not reliable. As such our study adds to the growing literature indicating that subcortical transfer of semantic information is more illusory than real.

Analysis of Variance↗

PubMed2005

Evaluating feature-category relations using semantic fluency tasks.

The issue of the relationship between semantic features and semantic categories has been raised by Warrington and colleagues, who claimed that sensory and functional-associative features are differentially important in determining the meaning of living and nonliving things (Warrington & McCarthy, 1983, 1987; Warrington & Shallice, 1984). In the present study, the effectiveness of semantic memory search for living and nonliving things with sensory and functional-associative search cues was evaluated through eight different adaptations of the semantic fluency task. More living thing responses and clusters were generated from sensory than from functional-associative search cues, while the reverse pattern holds for nonliving things responses and clusters. The results thus provide consistent empirical support for the assumption that sensory properties are fundamental in the representation of living things, while functional-associative properties are fundamental in the semantic representation of nonliving things.

Adult↗

PubMed2006

Episodic representations support early semantic learning: evidence from midazolam induced amnesia.

Current controversy exists regarding the role of episodic representations in the formation of long-term semantic memories. Using the drug midazolam to induce temporary amnesia we tested participants' memories for newly learned facts in a semantic cue condition or an episodic and semantic cue condition. Following midazolam administration, memory performance was superior in the episodic and semantic condition, suggesting early semantic learning is supported by episodic representations.

Adult↗