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PubMed2001

Semantic processing of open- and closed-class words: an event-related potentials study.

Previous research on open- and closed-class words has revealed the existence of several differences in the processing of these types of vocabulary. In this paper the processing of open- and closed-class words was compared by means of an early electrical brain response, recognition potential (RP), which indexes semantic processing and originates from basal extrastriate areas. The effects of word frequency on closed-class words were also investigated. For these purposes, open- and closed-class words, among other stimuli, were presented by means of the rapid stream stimulation procedure. Results showed that there were no significant differences when comparing the RP evoked by open- and closed-class words in the left hemisphere. However, in the right hemisphere this situation changed: the RP evoked by open- and closed-class words did differ. Moreover, there were no differences between the RP evoked by closed-class words and pseudowords. These patterns of results suggest that the semantic processing of closed-class words shares some aspects with the processing of open-class words, despite the existence of some differences. Thus, whereas the semantic processing of open-class words recruits brain areas of both hemispheres, the semantic processing of closed-class words is left-lateralized. A second purpose of this work is to study word-frequency effects on closed-class words. Our results show the insensitivity of closed-class words to word-frequency effects.

Adult↗

PubMed2000

Electrophysiology reveals semantic memory use in language comprehension.

The physical energy that we refer to as a word, whether in isolation or embedded in sentences, takes its meaning from the knowledge stored in our brains through a lifetime of experience. Much empirical evidence indicates that, although this knowledge can be used fairly flexibly, it is functionally organized in 'semantic memory' along a number of dimensions, including similarity and association. Here, we review recent findings using an electrophysiological brain component, the N400, that reveal the nature and timing of semantic memory use during language comprehension. These findings show that the organization of semantic memory has an inherent impact on sentence processing. The left hemisphere, in particular, seems to capitalize on the organization of semantic memory to pre-activate the meaning of forthcoming words, even if this strategy fails at times. In addition, these electrophysiological results support a view of memory in which world knowledge is distributed across multiple, plastic-yet-structured, largely modality-specific processing areas, and in which meaning is an emergent, temporally extended process, influenced by experience, context, and the nature of the brain itself.

Journal Article↗

PubMed1997

Syntactic and semantic processing in schizophrenic patients evaluated by lexical-decision tasks.

Two lexical-decision tasks with 500-ms stimulus-onset asynchrony were conducted with 34 schizophrenic patients. This group consisted of 24 schizophrenic patients with thought disorder (TD) and 10 schizophrenic patients without thought disorder (NTD), 14 psychiatric controls (depressive illness), 20 hospitalized controls, and 20 normal controls. One lexical-decision task with semantic relations (related vs. unrelated, Experiment 1) and 1 task with syntactic relations (congruent vs. incongruent; Experiment 2) were used to evaluate processing of different lexical information. In Experiment 1, although all control groups and NTD schizophrenic patients showed semantic priming, TD schizophrenic patients did not. In Experiment 2, all groups showed a significant syntactic effect. These findings provide evidence for an abnormality in semantic processing and the preservation of syntactic processing in TD schizophrenic patients, thus suggesting a deficit in the processing of semantic information under certain conditions when compared with normal syntactic processing.

Adult↗

PubMed2002

HealthCyberMap: a semantic visual browser of medical Internet resources based on clinical codes and the human body metaphor.

OBJECTIVES: HealthCyberMap (HCM-http://healthcybermap.semanticweb.org) is a web-based service for healthcare professionals and librarians, patients and the public in general that aims at mapping parts of the health information resources in cyberspace in novel ways to improve their retrieval and navigation. METHODS AND SERVICE DESCRIPTION: HCM adopts a clinical metadata framework built upon a clinical coding ontology for the semantic indexing, classification and browsing of Internet health information resources. A resource metadata base holds information about selected resources. HCM then uses GIS (Geographic Information Systems) spatialization methods to generate interactive navigational cybermaps from the metadata base. These visual cybermaps are based on familiar medical metaphors. CONCLUSIONS: HCM cybermaps can be considered as semantically spatialized, ontology-based browsing views of the underlying resource metadata base. Using a clinical coding scheme as a metric for spatialization ('semantic distance') is unique to HCM and is very much suited for the semantic categorization and navigation of Internet health information resources. Clinical codes ensure reliable and unambiguous topical indexing of these resources. HCM also introduces a useful form of cyberspatial analysis for the detection of topical coverage gaps in the resource metadata base using choropleth (shaded) maps of human body systems.

Abstracting and Indexing↗

PubMed2001

Associating semantic space abnormalities with formal thought disorder in schizophrenia: use of triadic comparisons.

Recent studies of schizophrenia have suggested that thought disorder results from abnormalities in semantic processing. In the following pilot study, the cognitive system used for organizing and associating concepts was examined using a triadic comparison task. The semantic maps of schizophrenia patients with high thought disorder (N = 5) were compared to that of schizophrenia patients with low levels of thought disorder (N = 5) and normal controls (N = 10) with multidimensional scaling analysis. At initial testing and at retest, patients with high levels of thought disorder exhibited consistently lower semantic goodness of fit scores and failed to map results of triadic comparisons along well-defined dimensions. Results suggest that thought disorder in schizophrenia is related to a disturbance in the organization of semantic networks.

Adult↗

PubMed2001

Semantic priming in Parkinson's disease: evidence for delayed spreading activation.

Nineteen persons with Parkinson's disease (PD) and 19 matched control participants completed a battery of online lexical decision tasks designed to isolate the automatic and attentional aspects of semantic activation within the semantic priming paradigm. Results highlighted key processing abnormalities in PD. Specifically, persons with PD exhibited a delayed time course of semantic activation. In addition, results suggest that experimental participants were unable to implicitly process prime information and, therefore, failed to engage strategic processing mechanisms in response to manipulations of the relatedness proportion. Results are discussed in terms of the 'Gain/Decay' hypothesis (Milberg, McGlinchey-Berroth, Duncan, & Higgins, 1999) and the dopaminergic modulation of signal to noise ratios in semantic networks.

Aged↗

PubMed2004

An early marker for semantic memory impairment in patients with schizophrenia.

INTRODUCTION: Semantic memory impairment is now a well-documented phenomenon in patients with schizophrenia. Nevertheless, the characteristics of this deficit and any early markers remain contentious. METHODS: In this preliminary study, 12 schizophrenic patients underwent longitudinal assessment using a battery of semantic memory tests. Patient performance was compared to 12 matched controls. Using set criteria (derived from Warrington & Shallice, 1979), we examined whether the patients had a disorder affecting access to intact representations, or a degradation/loss of the representations themselves. The criteria were: consistency across time and modality, level of attribute information, and responsiveness to cueing. Finally, we compared patient naming for the same items across two naming tests (naming-to-description and picture naming) to determine cross-modality consistency. RESULTS: As expected, normal controls outperformed the patients on all tests. Naming-to-description was the most significant differentiator between patients and controls. Patients were inconsistent across both time and modality, showed minimal attributional knowledge impairment, and improved significantly with cueing on two naming tests. CONCLUSION: The profile of results indicates an access-type semantic deficit in this cohort of patients with schizophrenic. Finally, on a naming-to-description task, the patients failed to name up to 20% of items that they could name to picture. This suggests that naming-to-definition may act as an early marker of semantic memory impairment.

Journal Article↗

PubMedDate not supplied

Semantic and inferencing abilities in children with communication disorders.

BACKGROUND: Semantic and inferencing abilities have not been fully examined in children with communication difficulties. AIMS: To investigate the inferential and semantic abilities of children with communication difficulties using newly designed tasks. METHODS & PROCEDURES: Children with different types of communication disorder were compared with each other and with three groups of typically developing children: those of the same chronological age and two groups of younger children. In total, 25 children aged 11 years with specific language impairment and 22 children, also 11 years of age, with primary pragmatic difficulties were recruited. Typically developing groups aged 11 (n=35; age-match), and those aged 9 (n=40) and 7 (n=37; language similar) also participated as comparisons. OUTCOMES & RESULTS: For Semantic Choices, children with specific language impairment performed significantly more poorly than 9- and 11-year-olds, whilst the pragmatic difficulties group scored significantly lower than all the typically developing groups. Borderline differences between specific language impairment and pragmatic difficulties groups were found. For inferencing, children with communication impairments performed significantly below the 11-year-old peers, but not poorer than 9- and 7-year-olds, suggesting that this skill is in line with language ability. Six children in the pragmatic difficulties group who met diagnosis for autism performed more poorly than the other two clinical groups on both tasks, but not statistically significantly so. CONCLUSIONS: Both tasks were more difficult for those with communication impairments compared with peers. Semantic but not inferencing abilities showed a non-significant trend for differences between the two clinical groups and children with pragmatic difficulties performed more poorly than all typically developing groups. The tasks may relate to each other in varying ways according to type of communication difficulty.

Aging↗

PubMedDate not supplied

A study of idiom comprehension in children with semantic-pragmatic difficulties. Part I: Task effects on the assessment of idiom comprehension in children.

In the apparent absence of suitable measures of idiom comprehension in normally developing and clinical populations, this study examined the relationship between a newly developed play task and a more conventional definition task. On the play task, children listened to a 1.5-minute, tape-recorded story into which were embedded 12 common idioms drawn from recordings of classroom teaching and children's television. As the story was then played again, sentence by sentence, the children were required to act it out using a play set and props. For each idiom, it was possible to act out either the idiomatic or literal meaning, but only the idiomatic meaning made sense in the context. The children's actions were video-taped and then played back to the child during the definition task. For this task, the video was stopped after each idiom occurred and the children were asked what they thought each idiom meant. Four groups of children were included. Twenty-six children (aged between 6-11 years), considered to have semantic-pragmatic difficulties, were compared with two groups of mainstream children (aged 6;6-7;6 and 10;6-11;6, respectively) and with a group of children (aged between 8-11 years) diagnosed with (other) language disorders not primarily of a semantic or pragmatic nature. The results indicate that the definition task underestimated common-idiom comprehension in normally developing children and, in particular, in children diagnosed with semantic-pragmatic difficulties or (other) language disorders. Furthermore, a significant difference in idiom comprehension between the two clinical groups evidenced on the play task was entirely masked on the definition task. It appeared that the expressive and metalinguistic demands of the definition task had a greater negative effect on the group of children with language disorders than on the children with semantic-pragmatic difficulties. Possible mechanisms through which the play task might have overestimated or underestimated idiom comprehension in these groups are examined and discussed. Although the nature of the play task probably facilitated idiom comprehension in these children, analysis supports the results of the play task being a reflection of true ability rather than an overestimation of idiom comprehension. A considerable incidence of false positive results on the definition task, coupled with its masking of significant differences in idiom comprehension across clinical groups militates against the use of definition tasks to assess idiom comprehension in research and clinical settings. In comparison with definition and multiple choice methodologies, the play task emerged as a more valid measure of common- and concrete-idiom comprehension in normally developing and clinical child populations.

Autistic Disorder↗

PubMed2005

YeastHub: a semantic web use case for integrating data in the life sciences domain.

MOTIVATION: As the semantic web technology is maturing and the need for life sciences data integration over the web is growing, it is important to explore how data integration needs can be addressed by the semantic web. The main problem that we face in data integration is a lack of widely-accepted standards for expressing the syntax and semantics of the data. We address this problem by exploring the use of semantic web technologies-including resource description framework (RDF), RDF site summary (RSS), relational-database-to-RDF mapping (D2RQ) and native RDF data repository-to represent, store and query both metadata and data across life sciences datasets. RESULTS: As many biological datasets are presently available in tabular format, we introduce an RDF structure into which they can be converted. Also, we develop a prototype web-based application called YeastHub that demonstrates how a life sciences data warehouse can be built using a native RDF data store (Sesame). This data warehouse allows integration of different types of yeast genome data provided by different resources in different formats including the tabular and RDF formats. Once the data are loaded into the data warehouse, RDF-based queries can be formulated to retrieve and query the data in an integrated fashion. AVAILABILITY: The YeastHub website is accessible via the following URL: http://yeasthub.gersteinlab.org.

Biology↗

PubMed1996

Brain activity during memory retrieval. The influence of imagery and semantic cueing.

The effects of imagery and semantic relatedness on cued retrieval of word pairs were examined in a functional imaging study of healthy volunteers. Subjects underwent 12 PET scans, preceded by the paced presentation of 12 paired associates. The associates were dichotomized into imageable and non-imageable groups. Within each group, the strength of semantic association between members of pairs was varied in an ordinal fashion. Subsequently, neural activity was measured while subjects were cued with the first item of each pair and required to recall the associated word. Recall of imageable words, when compared with non-imageable ones, was associated with activation of the precuneus, consistent with our hypothesis that this region is important in visual imagery at episodic retrieval. The reverse comparison, non-imageable versus imageable recall, was associated with activation of the left dorsolateral prefrontal cortex. Within both imageable and non-imageable groups, decreasing semantic association showed a corresponding increase in frontal activity bilaterally. One possible explanation is that of a practice-related effect, weaker-linked pairs having a greater number of pre-scan presentations. However, this explanation is incomplete as the most semantically distant, and most rehearsed, pairs (randomly linked) were associated with a reversal of this effect. This finding can be explained if frontal activity is associated with the difficulty of eliminating inappropriate responses at retrieval. For both randomly linked pairs and closely related pairs it is more likely that erroneous responses will be generated and, therefore, the work done to eliminate them will be greater. Our findings indicate that patterns of neural activity during cued recall depend upon the nature of the material and on the degree of association between the cue and the response.

Adult↗

PubMed2000

Time course of conscious and unconscious semantic brain activation.

Event-related brain potentials (ERPs) were used to investigate the neurophysiological correlates of conscious and unconscious semantic processing. Masked words, which do not enter consciousness, as well as visible words, were shown to modulate the N400 ERP potential to subsequently presented, meaningfully related target words. The N400 is known as an electrophysiological index of semantic processing. However, for unconsciously perceived words semantic brain activation decays fast within 200 ms, but increases with time for consciously perceived words. Thus, conscious and unconscious semantic activation involves similar brain areas, but both forms of processes exhibit distinct, qualitatively different time courses.

Adult↗

PubMed2003

Episodic and semantic memory in bilingual and monolingual children.

Although bilinguality has been reported to confer advantages upon children with respect to various cognitive abilities, much less is known about the relation between memory and bilinguality. In this study, 60 (30 girls and 30 boys) bilingual and 60 (30 girls and 30 boys) monolingual children in three age groups (mean ages 8.5, 10.5 and 12.5 years) were compared on episodic memory and semantic memory tasks. Episodic memory was assessed using subject-performed tasks (with real or imaginary objects) and verbal tasks, with retrieval by both free recall and cued recall. Semantic memory was assessed by word fluency tests. Positive effects of bilingualism were found on both episodic memory and semantic memory at all age levels. These findings suggest that bilingual children integrate and/or organize the information of two languages, and so bilingualism creates advantages in terms of cognitive abilities (including memory). Some sex differences were also found in episodic memory but not in semantic memory. This episodic memory difference was found with younger children.

Adolescent↗

PubMed1998

Abnormality of semantic network in patients with Alzheimer's disease. Evidence from verbal, perceptual, and olfactory domains.

A series of studies was initiated to model the organization of semantic memory in Alzheimer's disease (AD) patients using multidimensional scaling (MDS) and Pathfinder analyses. The resulting models (cognitive maps or semantic networks) embed studied stimuli in a coordinate space or network where distances between points are assumed to reflect psychological proximity between items. The organization of semantic networks in verbal and sensory domains were modeled based upon the frequency of the subject's choice of two concepts as most alike. Results suggested that while the organization of concepts in the semantic networks of AD patients was primarily based upon a concrete perceptual dimension in both verbal and olfactory domains, those of normal controls subjects were predominantly organized by an abstract conceptual attribute. Also, networks of AD patients were more complex and chaotic than normal, that is, they consisted of more unnecessary connections and of atypical strengths of association between concepts.

Alzheimer Disease↗

PubMed1999

Frontal brain activity during episodic and semantic retrieval: insights from event-related potentials.

Previous neuropsychological and neuroimaging results have implicated the prefrontal cortex in memory retrieval, although its precise role is unclear. In the present study, we examined patterns of brain electrical activity during retrieval of episodic and semantic memories. In the episodic retrieval task, participants retrieved autobiographical memories in response to event cues. In the semantic retrieval task, participants generated exemplars in response to category cues. Novel sounds presented intermittently during memory retrieval elicited a series of brain potentials including one identifiable as the P3a potential. Based on prior research linking P3a with novelty detection and with the frontal lobes, we predicted that P3a would be reduced to the extent that novelty detection and memory retrieval interfere with each other. Results during episodic and semantic retrieval tasks were compared to results during a task in which subjects attended to the auditory stimuli. P3a amplitudes were reduced during episodic retrieval, particularly at right lateral frontal scalp locations. A similar but less lateralized pattern of frontal P3a reduction was observed during semantic retrieval. These findings support the notion that the right prefrontal cortex is engaged in the service of memory retrieval, particularly for episodic memories.

Adolescent↗

PubMed1997

Specific semantic memory loss after hypoxic-ischemic injury.

A patient is reported who suffered hypoxic-ischemic injury causing isolated and eventually partially reversible semantic memory loss. Despite normal MRI findings, single-photon emission CT demonstrated dysfunction in posterior cortical association areas. Semantic memory is the sum of categorical, perceptual, and conceptual knowledge. While not localized in a strict sense like visual fields, semantic memory is thought to be broadly organized in the posterior association cortices, with a particular focus in the inferior temporal regions. Evidence for this has come from patients with herpes simplex encephalitis, temporo-occipital infarctions, and dementias. This case confirms the importance of these cortical regions for semantic memory. The rapid recovery in this case, as opposed to the encephalitis or infarction cases, suggests an important role for preservation of white matter connections in the region for reconstitution of function.

Adult↗

PubMed2026

PheBee: A Graph-Aware System for Scalable, Traceable, and Semantic Phenotyping.

OBJECTIVES: Phenotype-driven workflows in clinical and translational research require standardized ontology-based representation, ontology-aware cohort discovery, and provenance inspection for each assertion. Existing approaches optimize either for semantic traversal or scalable batch analytics, but not both. We describe PheBee, a hybrid system that links semantic assertions to scalable evidence storage via a deterministic identifier, preserving provenance while supporting ontology-aware discovery at cohort scale. MATERIALS AND METHODS: PheBee represents phenotype assertions in a knowledge graph as ontology-linked nodes with clinical modifier context (e.g., negated, family history), and stores supporting evidence records in a scalable row-oriented evidence table for cohort-scale access. The two layers are connected by a deterministic identifier enabling stable joins across repeated ingestions without duplicating high-volume evidence in the graph. We evaluated PheBee using synthetic datasets designed to exercise end-to-end ingestion and query workflows. RESULTS: Functional evaluation validated hierarchical term expansion, qualifier-aware retrieval, duplicate-free assertion handling under re-ingestion, and privacy-conscious management of subjects shared across multiple research projects. At scale (10,000 subjects producing 12M evidence records) PheBee completed ingestion in ~30 minutes and responded to interactive queries within 6 seconds under concurrent load. DISCUSSION: PheBee exposes a unified API for ontology-aware cohort discovery with hierarchical term expansion, subject-centric retrieval of phenotypes and clinical modifiers, and evidence and provenance queries. Its data model aligns with GA4GH Phenopackets, facilitating interoperability with phenotype exchange standards. CONCLUSION: By combining ontology-aware semantics with scalable, provenance-bearing evidence storage, PheBee provides a practical open-source foundation for phenotype-driven research workflows that demand both semantic precision and cohort-scale traceability.

cohort studies↗

PubMed1998

Letter and semantic fluency in Alzheimer's, Huntington's, and Parkinson's dementias.

A pattern of semantic fluency worse than letter fluency has been presented as evidence of impaired semantic networks in "cortical" dementias (e.g., Alzheimer's disease), distinguishing them from "subcortical" dementias (e.g., Parkinson's disease, Huntington's disease). However, there have been few systematic studies of this propositions. The present study compared Alzheimer's, Parkinson's, and Huntington's disease subjects with mild dementia to each other and to matched normal controls on letter and semantic fluency tasks. Results revealed parallel semantic/letter fluency patterns for all groups, suggesting that there is no unique pattern of semantic/letter fluency deficits for "cortical" or "subcortical" dementias. Qualitative errors (repetitions, intrusions) were also evaluated. Huntington's subjects had significantly more repetition errors than all other groups, and Alzheimer's subjects had significantly more repetition errors than Parkinson's subjects and normal controls. There were no differences in number of intrusion errors. Findings suggest that semantic fluency deficits are not unique to Alzheimer's dementia and may not help to differentiate between different etiologies of dementia.

Journal Article↗