SEARCH · PubMed Health

Results for “Semantics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

PubMed2006

Patterns of regional brain hypometabolism associated with knowledge of semantic features and categories in Alzheimer's disease.

The study of semantic memory in patients with Alzheimer's disease (AD) has raised important questions about the representation of conceptual knowledge in the human brain. It is still unknown whether semantic memory impairments are caused by localized damage to specialized regions or by diffuse damage to distributed representations within nonspecialized brain areas. To our knowledge, there have been no direct correlations of neuroimaging of in vivo brain function in AD with performance on tasks differentially addressing visual and functional knowledge of living and nonliving concepts. We used a semantic verification task and resting 18-fluorodeoxyglucose positron emission tomography in a group of mild to moderate AD patients to investigate this issue. The four task conditions required semantic knowledge of (1) visual, (2) functional properties of living objects, and (3) visual or (4) functional properties of nonliving objects. Visual property verification of living objects was significantly correlated with left posterior fusiform gyrus metabolism (Brodmann's area [BA] 37/19). Effects of visual and functional property verification for non-living objects largely overlapped in the left anterior temporal (BA 38/20) and bilateral premotor areas (BA 6), with the visual condition extending more into left lateral precentral areas. There were no associations with functional property verification for living concepts. Our results provide strong support for anatomically separable representations of living and nonliving concepts, as well as visual feature knowledge of living objects, and against distributed accounts of semantic memory that view visual and functional features of living and nonliving objects as distributed across a common set of brain areas.

Aged↗

PubMed2002

Semantic dysfunction in women with schizotypal personality disorder.

OBJECTIVE: This study examined whether early or late processes in semantic networks were abnormal in women with a diagnosis of schizotypal personality disorder. The N400 component of the EEG event-related potentials was used as a probe of semantic processes. METHOD: Word pairs were presented with short and long stimulus-onset asynchronies to investigate, respectively, early and late semantic processes in 16 women with schizotypal personality disorder and 15 normal female comparison subjects. Event-related potentials were recorded in response to the last words in a pair. RESULTS: With the short stimulus-onset asynchrony, the N400 amplitude was less negative in the schizotypal personality disorder group than in the normal comparison group. No group differences were found with the long stimulus-onset asynchrony. CONCLUSIONS: The finding of a less negative than normal N400 amplitude with the short stimulus-onset asynchrony in women with schizotypal personality disorder supports the hypothesis that persons with this disorder evince an overactivation of semantic networks. The absence of group differences with the long stimulus-onset asynchrony, which is primarily sensitive to processes involved in context integration, suggests that in this group of schizotypal personality disorder subjects, additional demands on working memory may be necessary to bring out the semantic dysfunction.

Adult↗

PubMed2004

Preferences and inferences in encoding visual objects: a systematic comparison of semantic and affective priming.

The authors systematically compared semantic and affective priming in five studies involving words and pictures. In Studies 1 (lexical decision task) and 2 (evaluation task), irrelevant short duration (200 ms) primes were briefly flashed before relevant targets. The authors orthogonally varied both the semantic and affective relations between primes and targets. In both studies, semantic priming but not affective priming was found. Study 3 revealed that the same stimuli can produce affective priming, but only when words come from a single semantic category. Studies 4 and 5 used pictures rather than words to examine automatic encoding tendencies. The results conceptually replicated those from Studies 1 and 2. In sum, the findings suggest that affective priming may be a relatively fragile phenomenon, particularly when the semantic properties of objects vary in a salient manner.

Adult↗

PubMed1975

The usefulness of the semantic differential with "mild grade' mental defectives.

Although the semantic differential has been quite widely used with mental defectives, its usefulness (in its traditional form) with such a population has not been conclusively demonstrated. The semantic differential was developed and shown to be valid as an index of representational mediation processes. However, there is also evidence of a mediational deficiency among retardates which, therefore, ought to be reflected in retardates' responses to the semantic differential. Thus, the present study was designed to test two hypotheses: (a) that mild grade retardates, in comparison with subjects of average intelligence, would show less discrimination in the use of the semantic differential, and (b) that such discriminative deficiencies would in turn predispose toward a polarized response bias among the retarded. The results, which support both hypotheses, are discussed in terms of their implications for the usefulness of an unmodified semantic differential with the mentally subnormal.

Adult↗

PubMed2005

Functional neuroimaging of semantic and episodic musical memory.

The distinction between episodic and semantic memory has become very popular since it was first proposed by Tulving in 1972. So far, very few neuropsychological, psychophysical, and imaging studies have related to the mnemonic aspects of music, notably on the long-term memory features, and practically nothing is known about the functional anatomy of long-term memory for music. Numerous functional imaging studies have shown that retrieval from semantic and episodic memory is subserved by distinct neural networks. For instance, the HERA model (hemispheric encoding/retrieval asymmetry) ascribes to the left prefrontal cortex a preferential role in the encoding process of episodic material and the recall of semantic information, while the right prefrontal cortex would preferentially operate in the recall of episodic information. However, these results were essentially obtained with verbal and visuo-spatial material. We have done a study to determine the neural substrates underlying the semantic and episodic components of music using familiar and nonfamiliar melodic tunes. Two distinct patterns of activations were found: bilateral activation of the middle and superior frontal areas and precuneus for episodic memory, and activation of the medial and orbital frontal cortex bilaterally, left angular gyrus, and the anterior part of the left middle and superior temporal gyri for semantic memory. We discuss these findings in light of the available neuropsychological data obtained in brain-damaged subjects and functional neuroimaging studies.

Auditory Pathways↗

PubMed2005

Toward semantic interoperability in home health care: formally representing OASIS items for integration into a concept-oriented terminology.

OBJECTIVE: The authors aimed to (1) formally represent OASIS-B1 concepts using the Logical Observation Identifiers, Names, and Codes (LOINC) semantic structure; (2) demonstrate integration of OASIS-B1 concepts into a concept-oriented terminology, the Medical Entities Dictionary (MED); (3) examine potential hierarchical structures within LOINC among OASIS-B1 and other nursing terms; and (4) illustrate a Web-based implementation for OASIS-B1 data entry using Dialogix, a software tool with a set of functions that supports complex data entry. DESIGN AND MEASUREMENTS: Two hundred nine OASIS-B1 items were dissected into the six elements of the LOINC semantic structure and then integrated into the MED hierarchy. Each OASIS-B1 term was matched to LOINC-coded nursing terms, Home Health Care Classification, the Omaha System, and the Sign and Symptom Check-List for Persons with HIV, and the extent of the match was judged based on a scale of 0 (no match) to 4 (exact match). OASIS-B1 terms were implemented as a Web-based survey using Dialogix. RESULTS: Of 209 terms, 204 were successfully dissected into the elements of the LOINC semantics structure and integrated into the MED with minor revisions of MED semantics. One hundred fifty-one OASIS-B1 terms were mapped to one or more of the LOINC-coded nursing terms. CONCLUSION: The LOINC semantic structure offers a standard way to add home health care data to a comprehensive patient record to facilitate data sharing for monitoring outcomes across sites and to further terminology management, decision support, and accurate information retrieval for evidence-based practice. The cross-mapping results support the possibility of a hierarchical structure of the OASIS-B1 concepts within nursing terminologies in the LOINC database.

Dictionaries, Medical as Topic↗

PubMed2006

Enhancing text categorization with semantic-enriched representation and training data augmentation.

OBJECTIVE: Acquiring and representing biomedical knowledge is an increasingly important component of contemporary bioinformatics. A critical step of the process is to identify and retrieve relevant documents among the vast volume of modern biomedical literature efficiently. In the real world, many information retrieval tasks are difficult because of high data dimensionality and the lack of annotated examples to train a retrieval algorithm. Under such a scenario, the performance of information retrieval algorithms is often unsatisfactory, therefore improvements are needed. DESIGN: We studied two approaches that enhance the text categorization performance on sparse and high data dimensionality: (1) semantic-preserving dimension reduction by representing text with semantic-enriched features; and (2) augmenting training data with semi-supervised learning. A probabilistic topic model was applied to extract major semantic topics from a corpus of text of interest. The representation of documents was projected from the high-dimensional vocabulary space onto a semantic topic space with reduced dimensionality. A semi-supervised learning algorithm based on graph theory was applied to identify potential positive training cases, which were further used to augment training data. The effects of data transformation and augmentation on text categorization by support vector machine (SVM) were evaluated. RESULTS AND CONCLUSION: Semantic-enriched data transformation and the pseudo-positive-cases augmented training data enhance the efficiency and performance of text categorization by SVM.

Algorithms↗

PubMed2005

An ERP study on facial expression of emotion: comparison of linguistic and visual semantic decoding.

The present research compared the semantic information processing of linguistic stimuli with semantic elaboration of nonlinguistic facial stimuli. To explore brain potentials (ERPs, event-related potentials) related to decoding facial expressions and the effect of semantic valence of the stimulus, we analyzed data for 20 normal subjects (M age = 23.6 yr., SD = 0.2). Faces with three basic emotional expressions (fear, happiness, and sadness from the 1976 Ekman and Friesen database), with three semantically anomalous expressions (with respect to their emotional content), and the neutral stimuli (face without an emotional content) were presented in a random order. Differences in peak amplitude of ERP were observed later for anomalous expressions compared with congruous expressions. In fact, the results demonstrated that the emotional anomalous faces elicited a higher negative peak at about 360 msec., distributed mainly over the posterior sites. The observed electrophysiological activity may represent specific cognitive processing underlying the comprehension of facial expressions in detection of semantic anomaly. The evidence is in favour of comparability of this negative deflection with the N400 ERP effect elicited by linguistic anomalies.

Adult↗

PubMed1998

Manual response set in a Stroop-like task involving categorization of English and Japanese words indicates a common semantic representation.

The present study examined the semantic representation for English and Japanese words. A previous study using the interlingual word categorization showed Japanese words affected the semantic processing of English words, but English words did not affect the semantic processing of Japanese words. The present study tested the interlingual word categorization by a manual response instead of the vocal response. Analysis showed English words also affected the semantic processing of Japanese words. The common semantic representation for English and Japanese words was discussed.

Attention↗

PubMed2001

Changes in the constraints of semantic and syntactic congruity on memory across three age groups.

20 college undergraduates, 25 sixth-grade, and 31 second-grade students studied targets embedded in three types of sentence contexts and then performed free recall and cued recall tests. Although there were no differences in performance of free recall among sentence types within each age group, the differences in cued recall among sentence types were observed. For sixth graders and undergraduates, both semantically congruous/syntactically congruous sentences and semantically incongruous/syntactically congruous sentences led to a better cued recall of targets than semantically incongruous/syntactically incongruous sentences. Second graders performed better in a cued recall of targets in semantically congruous/syntactically congruous sentences than for the other two sentence types. The results were interpreted as indicating changes across age groups in constraints of semantic and syntactic congruity on the spreading activation of targets in memory.

Adolescent↗

PubMed2001

Differential cognitive processing of Kanji and Kana words: do orthographic and semantic codes function in parallel in word matching task.

Relative engagements of the orthographic and semantic codes in Kanji and Hiragana word recognition were investigated. In Exp. 1, subjects judged whether the pairs of Kanji words (prime and target) presented sequentially were physically identical to each other in the word condition. In the sentence condition, subjects decided whether the target word was valid for the prime sentence presented in advance. The results showed that the response times to the target swords orthographically similar (to the prime) were significantly slower than to semantically related target words in the word condition and that this was also the case in the sentence condition. In Exp. 2, subjects judged whether the target word written in Hiragana was physically identical to the prime word in the word condition. In the sentence condition, subjects decided if the target word was valid for the previously presented prime sentence. Analysis indicated that response times to orthographically similar words were slower than to semantically related words in the word condition but not in the sentence condition wherein the response times to the semantically and orthographically similar words were largely the same. Based on these results, differential contributions of orthographic and semantic codes in cognitive processing of Japanese Kanji and Hiragana words was discussed.

Adult↗

PubMed2004

Semantic satiation effect in young and older adults.

Auditory and auditory+visual massed repetition served to examine semantic satiation in young and older adults and to understand the possible sources of this phenomenon. In Exp. 1, participants either heard or heard and saw prime words (ROYALTY) repeated 2, 15, or 30 times and made relatedness judgments on targets that were either semantically related (queen) or unrelated (box) to the repeated word. To distinguish satiation from general boredom, semantic satiation was operationally defined as a repetition-induced change in the difference between related and unrelated pairs (relatedness effect). Auditory massed repetition, either alone or in conjunction with prolonged visual exposure, produced semantic satiation effects in both young and older adults. In Exp. 2, participants heard the prime words of the earlier experiment, each repeated 30 times and reported perceptual changes (verbal transformations) during the repetition treatment. In this experiment, older adults were less susceptible to this type of habituation. The discussion focuses on the mechanisms that may be responsible for producing semantic satiation effects in young and older adults with different forms of massed repetition.

Adolescent↗

PubMed2001

Assessing the validity of the semantic differential portion of the Apperceptive Personality Test.

This study investigated the validity of the semantic differential portion of the Apperceptive Personality Test with 225 undergraduates who completed the Marlowe-Crowne Social Desirability scale, actual-self and ideal-self semantic differential scales (e.g., Actual-self and ideal-self), and either the Apperceptive Personality Test or a modified version. A projected-self score was calculated using the semantic differential ratings of the hero(ine) character on the test, e.g., Projected self. A strong negative correlation indicated that, as the difference between the Ideal-self and Actual-self dereased, the difference between the Actual-self and Projected-self increased. Discriminant analyses indicated that highly guarded participants, e.g., high Social Desirability scores, showed more congruency between Ideal-self and Actual-self and less congruency between Actual-self ratings and Projected-self on the APT than did less guarded participants. When the difference scores incorporated only those semantic differential items that loaded on an Ealuative factor, the same result of discriminant analysis was found when participants who comleted the modified version were included. These findings support the validity of the test's semantic differential items and suggest that guardedness tends to promote more similarity between Actual-self and Ideal-self and less similarity between Actual-self and Projected-self.

Adult↗

PubMed2000

How automatically is meaning accessed: a review of the effects of attention on semantic processing.

This chapter attempts to review electrophysiological data that stand at the intersection of two large domains of research: selective attention and semantic processing. Analogous behavioral studies will be discussed as a way of introducing the reader to some of the more complex paradigms, and providing convergent evidence. The focus of this review will be on data that add special insight into the issue of semantic processing in the absence of attention. However, paradigms which allow semantic activation in the absence of awareness will also be examined as these studies have also yielded data concerning automatic semantic processing. It is concluded that a great deal of semantic processing can occur in the absence of attention as well as in the absence of awareness.

Attention↗

PubMed1987

Do event-related potentials (ERPs) reflect right hemisphere's processing of semantics?

To test the right hemisphere's functional difference in relation to semantically related vs. semantically unrelated linguistic tasks we investigated 25 young right-handed healthy adults. A S1-S2 design was used. At S1 one word was presented binaurally, at S2 two words dichotically. S1-S2 was composed of sentence-like (syntagmatic) and nonsentence-like (paradigmatic) word sequences with and without semantic relations. As control trials we used pure tones and modulated noise. The EEG was recorded over frontal, central and temporoparietal areas of both hemispheres. Referring to semantics it could be shown only that semantic relations between words increased the amount of recalled words. Additionally, ERPs reflected: modes of presentation (binaural vs. dichotic) processing of different linguistic categories (e.g., syntagmatic vs. paradigmatic) and frontocentrally focused neuronal processes of both hemispheres before language production.

Adult↗

PubMed2004

Semantic priming effects in normal versus poor readers.

The authors studied sensitivity to semantic priming, as distinct from semantic judgment, in poor readers. Association strength (high vs. low semantic association) was manipulated factorially with semantic association type (categoric vs. thematic association). Participants were 11-year-old poor readers (n = 15) who were matched with a group of chronological-age controls (n = 13), and also matched with a group of reading-age controls (n = 15). Three priming conditions were used: related, unrelated, and neutral prime. Neutral primes consisted of a row of hash marks. Related primes elicited shorter decision latencies than did unrelated primes. Neutral primes elicited the slowest responses in all groups. Poor readers showed an additional delay in the neutral prime condition. No effects of association type (categorical vs. thematic) or association strength (high vs. low) were found, nor were any relationship with reading ability found. The delayed performance of the poor readers on neutral primes is explained in terms of orthographic processing and dependency on grapheme phoneme relationships. The findings are discussed with reference to F. R. Vellutino, D. M. Scanlon, and D. Spearing's (1995) work on semantic processing and reading ability.

Association↗

PubMed2002

Cascaded versus noncascaded models of lexical and semantic processing: the turple effect.

The density of the orthographic neighborhood surrounding an item has been shown to have an inhibitory effect for nonwords in a lexical decision experiment. Four experiments are reported investigating whether a similar pattern holds for a semantic categorization task (animal vs. non-animal). In the first experiment, no effects of neighborhood density were found for nonexemplars, whether they were words or nonwords. The absence of any inhibitory effect for nonwords implies that close orthographic neighbors are ignored. However, the second experiment showed that if the nonword has a neighbor that is an animal name (eg., turple), an interference effect is observed, implying that neighbors do exert an effect if they have the right semantic properties. The same items showed no additional interference in lexical decision. These results suggest the involvement of semantic properties very early in the processing cycle. A cascaded processing system monitoring activation in semantic features can explain these results, but cannot explain the frequency effect observed for nonexemplar words or the fact that variation in density is irrelevant when one of the neighbors is an exemplar. It is argued that existing models of semantic categorization must be extended to accommodate these results.

Decision Making↗

PubMed2002

The locus and nature of semantic congruity in symbolic comparison: evidence from the Stroop effect.

Pictures of animals with names of animals printed within the pictures were presented for comparative judgments of size based on either the pictures or the names. The picture-word compounds were compared faster with picture than with word as the relevant dimension. The comparisons of pictures were free of interference from the irrelevant names, but the comparisons of names suffered considerable Stroop interference from the irrelevant pictures. Large effects of semantic congruity characterized the comparisons of both pictures and words. Stroop congruity and semantic congruity did not interact even for comparison of words in which both were present, leading instead to additive effects. The results support theories that (1) place semantic congruity in the decision stage and (2) minimize the role of semantic processing as the basis of the semantic congruity effect.

Adult↗