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 1,657 records · Page 92Linked to original sources

PubMed1981

The impairment of verbal semantic memory: a single case study.

We report our investigations of a single patient in whom there was a selective impairment of semantic memory. She had a marked deficit of individual word comprehension although other language and linguistic skills were relatively preserved. Here we document that her failures in word comprehension were stable over a long time period. She made "phonological" errors in defining meanings, which we argue are analogous to "visual" errors in reading. On verbal learning tasks her performance was shown to be relatively preserved, a finding which provides evidence of the dissociation of verbal semantic memory and episodic (event) memory.

Aged↗

PubMed1990

Differential impairment of semantic and episodic memory in Alzheimer's and Huntington's diseases: a controlled prospective study.

A controlled prospective study compared the performance of 14 patients with dementia of Alzheimer type (DAT) and 14 patients with Huntington's Disease (HD), who were matched for overall level of dementia, on a battery of semantic and episodic memory tests. The DAT patients were significantly more impaired on measures of delayed verbal and figural episodic memory, and in addition showed a more rapid rate of decline on tests which depend upon the integrity of semantic knowledge (naming, number information, similarities and category fluency). In contrast, the HD patients were significantly worse, and showed a more rapid decline on the letter fluency test, a task especially sensitive to deficiencies in retrieval. The HD patients were also more impaired than DAT patients on a vocabulary test and on copying geometric figures. The observed double dissociations offer compelling evidence that aetiologically distinct forms of dementing illness result in different patterns of cognitive impairment.

Aged↗

PubMed1994

Initial letter and semantic category fluency in Alzheimer's disease, Huntington's disease, and progressive supranuclear palsy.

Ten patients with dementia of Alzheimer's type, 10 patients with progressive supranuclear palsy, and 10 patients with Huntington's disease were compared on two types of verbal fluency task--namely, initial letter fluency and category (semantic) fluency. The groups were carefully matched for overall level of dementia on the dementia rating scale, and were compared with 25 age matched normal controls. The controls found letter fluency more difficult than category fluency, and this relative pattern of performance was repeated in the progressive supranuclear palsy and Huntington's disease groups, although both groups were significantly impaired on both tasks. By contrast, patients with Alzheimer's disease performed just as poorly as the progressive supranuclear palsy and Huntington's disease groups on the category tasks, but were significantly less impaired at letter fluency, performing at near normal levels on this task. From these results, it is suggested that the performances of patients with progressive supranuclear palsy and Huntington's disease relate largely to initiation and retrieval problems secondary to disruption of frontostriatal circuits, whereas in Alzheimer's disease, the poorer performance on category fluency is due principally to the breakdown of semantic knowledge, which probably reflects temporal neocortical involvement.

Adult↗

PubMed2004

Test-retest reliability of fMRI during nonverbal semantic decisions in moderate-severe nonfluent aphasia patients.

Cortical reorganization in poststroke aphasia is not well understood. Few studies have investigated neural mechanisms underlying language recovery in severe aphasia patients, who are typically viewed as having a poor prognosis for language recovery. Although test-retest reliability is routinely demonstrated during collection of language data in single-subject aphasia research, this is rarely examined in fMRI studies investigating the underlying neural mechanisms in aphasia recovery. The purpose of this study was to acquire fMRI test-retest data examining semantic decisions both within and between two aphasia patients. Functional MRI was utilized to image individuals with chronic, moderate-severe nonfluent aphasia during nonverbal, yes/no button-box semantic judgments of iconic sentences presented in the Computer-assisted Visual Communication (C-ViC) program. We investigated the critical issue of intra-subject reliability by exploring similarities and differences in regions of activation during participants' performance of identical tasks twice on the same day. Each participant demonstrated high intra-subject reliability, with response decrements typical of task familiarity. Differences between participants included greater left hemisphere perilesional activation in the individual with better response to C-ViC training. This study provides fMRI reliability in chronic nonfluent aphasia, and adds to evidence supporting differences in individual cortical reorganization in aphasia recovery.

Aged↗

PubMed1988

Application of Osgood's Semantic Differential to the study of psychotherapeutic treatments.

Osgood's Semantic Differential was applied to a group of 35 neurotic patients at initial and final stage of individual psychoanalytical psychotherapy. When compared to 'normal' subjects who had not undergone treatment but were examined under the same conditions, neurotic subjects showed, between test and retest, more conspicuous semantic changes, several of which--although not all--brought them closer to normal subjects.

Adolescent↗

PubMed1979

Mood and affect: a semantic confusion.

Although semantic clarity is a cornerstone of scientific psychiatry, psychiatrists often use technical words with the false assumption that their meanings are clear. The common use of the terms "mood" and "affect" illustrates this point. The authors attempt to show how unclear definitions of these words have led to confusion and how they could be more clearly understood by careful semantic and phenomenologic analysis.

Affect↗

PubMed1994

Semantic organization of hallucinated "voices" in schizophrenia.

The authors found that the different hallucinated "voices" of four schizophrenic subjects reported over 1-3 weeks expressed semantic content that was at least as persistent as clauses sampled from single 5-7-minute conversational discourses of four comparison speakers. The high degree of semantic recurrence of voices from one day to the next may contribute to the mistaken belief that these experiences derive from a particular nonself agent or speaker.

Adult↗

PubMed2005

Cognitive control and semantics in schizophrenia: an integrated approach.

OBJECTIVE: The authors tested whether decisions about incongruencies in the representation and processing of semantic knowledge, thought to be related to cognitive control, are selectively impaired in schizophrenia. METHOD: Twenty-four patients with schizophrenia and 24 healthy comparison subjects determined the relative size of paired stimuli as they are in the real world. Stimuli were words or images. Real-world "distance" (size difference between stimuli) was manipulated within pairs, as was "congruency" between real-world and presentation size. RESULTS: Although patients were slower overall, both groups exhibited similar effects of "distance" and "congruency"; the task was easier when the real-world size difference between stimuli was greater and when stimuli were congruent in presentation and real-world size. CONCLUSIONS: Some aspects of the representation of semantic knowledge are preserved in schizophrenia, and patients use this information to control cognition in the same manner as healthy individuals.

Adult↗

PubMedDate not supplied

Using semantics, grammar, phonology, and rapid naming tasks to predict word identification.

This study investigated the relative importance of semantic, grammatical, phonological, and rapid naming abilities in predicting word identification in a large, representative sample of children enrolled in first through sixth grade, using correlation, factor analysis, multiple regression, and predictive outcome analysis techniques. Composite measures of these abilities were found to correlate significantly with word identification, even after controlling for the effects of nonverbal intelligence. Factor analysis indicated that the spoken language composites and the word identification composite loaded on one factor, whereas the perceptual speed composites loaded on a second factor. Multiple regression analyses showed that among younger children in the early stages of learning to read and children whose word identifying skills were below average, the phonology and rapid naming composites accounted for the most variance in predicting word identification skills. Among older children and children who were proficient in word identification, the semantics composite accounted for the most variance. The most important analyses in this study (i.e., the calculations of the sensitivity indexes, the specificity indexes, and the positive predictive values) evaluated the practical value of using the composites to predict poor word identification skills in children. To be considered practically useful, all predictive outcome values had to be .75 or greater. None of the composites studied, including an application of the double-deficit hypothesis, met this criterion. The results from this study question the accuracy and utility of using any of the abilities studied to predict which students are at risk for or have poor word identification skills.

Child↗

PubMedDate not supplied

Taxonomic clustering and frequency associations as features of semantic memory development in children with learning disabilities.

This study investigated taxonomic clustering and use of frequency associations as features in the semantic memory development of children with learning disabilities (LD). Free-recall organization of second- and sixth-grade children with and without LD was analyzed for two types of primary and secondary word lists: (a) items associated with frequency (FA), and (b) items related by category members (CM). In contrast to expected findings, younger, non-disabled children organized words categorically as proficiently as their older nondisabled peers, and the categorization abilities of children with LD were comparable to those of nondisabled subjects, with one exception: Subjects with LD showed less clustering for secondary FA. These results indicate that when individual child-generated word lists (i.e., meaningful and familiar words) are used, children with LD may not be impaired in their ability to recognize and utilize semantic structure to facilitate learning.

Adolescent↗

PubMedDate not supplied

Electrophysiological studies of visual word perception, lexical organization, and semantic processing: a tutorial review.

Visual word recognition requires the matching of an orthographic unit to its meaning via a phonological unit in the mental lexicon. The nature and the speed of this process are affected by "bottom-up" factors (e.g., the manner in which the phonology is represented by the orthography) and by "top-down" factors (e.g., network connections between related words in the lexicon, and contextual semantic information). Event-related potentials (ERPs) provide a relatively new tool that complements behavioral measures of word recognition. ERP components recorded during word perception tasks have been found to be sensitive to orthographic, phonological, and semantic manipulations. They go beyond behavioral measures by providing continuous information about the activity of the cognitive system from stimulus onset to the occurrence of the response. In addition, ERPs enable the researcher to examine word perception and reading in more natural situations, without time constraints and overt responses. Finally, intra-cranial ERP recording in humans and modern analytical techniques may shed light on the relations between cognitive linguistic processes and brain structures. Collaboration between cognitive psychologists, linguists, and ERP researchers will be necessary to exploit the great potential of these electrophysiological techniques.

Cognition↗

PubMed1998

Impairment of semantic categorization processes among thought-disordered schizophrenic patients.

OBJECTIVE: To explore semantic categorization strategies in patients with schizophrenia. METHOD: A short-term memory-recognition task that reveals the effects associated with categorization was created and applied to 2 groups of patients with schizophrenia and depression. RESULTS: Only the schizophrenic subgroup with formal thought disorder (measured using Andreasen's Thought, Language, and Communication [TLC] scale) exhibited a deficiency in semantic categorization strategies during the task. CONCLUSION: These results support the hypothesis of the impairment of the processes involved in the processing of contextual information in patients with schizophrenia who suffer from formal thought disorder.

Adult↗

PubMed2006

Next-generation applications in healthcare digital libraries using semantic service composition and coordination.

Healthcare digital libraries (DLs) increasingly make use of dedicated services to access functionality and/or data. Semantic (web) services enhance single services and facilitate compound services, thereby supporting advanced applications on top of a DL. The traditional process management approach tends to focus on process definition at build time rather than on actual service events in run time, and to anticipate failures in order to define appropriate strategies. This paper presents a novel approach where service coordination is distributed among a set of agents. A dedicated component plans compound semantic services on demand for a particular application. In failure, the planner is reinvoked to define contin- gency strategies. Finally, matchmaking is effected at runtime by choosing the appropriate service provider. These combined technologies will provide key support for highly flexible next-generation DL applications. Such technologies are under development within CASCOM.

Information Storage and Retrieval↗

PubMed1993

Latency of P3 in semantic categorization of Chinese characters: preliminary report.

ERPs to target stimulation with tone and semantic categorization of Chinese characters were studied in 100 healthy subjects. Age ranged from 40-50 years old (80 subjects) and 50-68 years old (20 subjects). Two hundred Chinese characters were divided into four groups in accordance with the meaning of characters. The probability of each group was 25%. Each group could be used as target stimulus. The latencies of the exogenous components on these two different tasks were the same. The endogenous components on the semantic categorization of Chinese characters were longer than with tone stimulation. In the 40-50 years age group the mean latencies of positive waves at Fz, Cz, C3, and Pz were 546.1034 msec, 547.8621 msec, 548.0345 msec and 547.3103 msec, respectively; latencies in the 50-68 years group were 542.9412 msec, 545.2941 msec, 543.8824 msec and 553.0588 msec respectively. A positive wave, which we called P550 and divided into P550a and P550b, could be recognized in 27.5% of them.

Adult↗

PubMed2002

Enhanced semantic priming in schizophrenia: a computer model based on excessive pruning of local connections in association cortex.

BACKGROUND: Many studies have found that people with schizophrenia exhibit abnormally high levels of semantic priming. Post-mortem and neuroimaging studies of schizophrenia suggest a reduction of neuritic processes (dendrites and synapses). AIMS: To demonstrate that reductions in neuritic processes can produce excessive priming in patients with schizophrenia. METHOD: Associative memory was simulated using a computer-based neural network system consisting of two interactive neural groups, one coding for individual memories and the other for the category to which each memory belonged. RESULTS: Variation of a single parameter determining the density of local connections within the two neuronal groups gave a close approximation to levels of memory access and semantic priming previously reported in normal subjects and in patients with schizophrenia. CONCLUSIONS: This study suggests that schizophrenia arises from excessive pruning of local connections in association cortex. Its findings shed light on the mechanisms underlying cognitive priming more generally, and how it might emerge developmentally.

Adolescent↗

PubMed2004

The evolution of semantic systems.

Semantic or cultural systems are sets of concepts connected by meaningful relationships, and they exhibit properties similar to those of populations of biological organisms. Drawing upon ideas from evolutionary biology and methods from information technology, this article explores the potential for research and engineering on the evolution of semantic systems. Such work in cultural genetics requires two things: (1) a rigorous but evolving taxonomic system to categorize cultural artifacts, elements, and clusters, and (2) a set of hypotheses about the processes that cause evolutionary change. This article illustrates systematic approaches to cultural taxonomy with data on the popular ideology of the space program, science fiction motion pictures, nanotechnology books, and nanotechnology research grants. It offers hypotheses derived from evolutionary and population biology that might be useful in explaining cultural evolution.

Biological Evolution↗

PubMed2006

Object-of-interest image segmentation based on human attention and semantic region clustering.

We propose a novel object-of-interest (OOI) segmentation algorithm for various images that is based on human attention and semantic region clustering. As object-based image segmentation is beyond current computer vision techniques, the proposed method segments an image into regions, which are then merged as a semantic object. At the same time, an attention window (AW) is created based on the saliency map and saliency points from an image. Within the AW, a support vector machine is used to select the salient regions, which are then clustered into the OOI using the proposed region merging. Unlike other algorithms, the proposed method allows multiple OOIs to be segmented according to the saliency map.

Algorithms↗

PubMed2002

The perceived urgency of speech warnings: semantics versus acoustics.

The relationship between the semantics of words and the acoustics of the way they are spoken is explored. Actors spoke warning signal words in an urgent, nonurgent and monotone style, and participants rated the urgency of the words. Results showed effects for signal word and style of presentation. Acoustic analysis showed that the urgent words were spoken at higher frequency with a broader pitch range and were louder than the nonurgent or monotone words. These acoustic differences were used to synthesize artificial versions of signal words in urgent and nonurgent formats. The urgent words were rated as more urgent than the nonurgent words, a finding attributable to their differing acoustics. Within each speaking style the words were acoustically the same, yet effects for signal word were found, suggesting that semantics is also important in urgency perception. This research has implications for the design and implementation of speech warning systems, particularly those in which urgency mapping is required.

Adolescent↗