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Results for “Semantics”

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PubMed2006

(Category-specific) semantic deficit in Alzheimer's patients: the role of semantic distance.

A semantic battery comprising items from living and nonliving categories was administered to a sample of subjects suffering from probable Alzheimer's type dementia (n=20). The results were analyzed to test the role of semantic distance in predicting group accuracy and its possible causal link with the phenomenon of a category-specific deficit for living things in the experimental population. Our findings confirm a category effect favoring nonliving items (over and above the role of confounding variables) in patients with Alzheimer's disease and support the major role of an imbalance of semantic distance in the testing material in the genesis of this phenomenon.

Aged↗

PubMed2006

Evidence of semantic disorganisation using semantic priming in individuals with high schizotypy.

Semantic processing deficits are present in schizophrenia and are particularly evident on semantic priming tasks. Using high schizotypes (psychosis-prone individuals) can overcome some confounds involved in studying actively symptomatic schizophrenics. In the current study, 26 high and 32 low scorers on the O-LIFE schizotypy scale (from a sample of 251 students) were selected for testing. All subjects were administered a lexical-decision semantic priming task where half the stimuli had a short 200 ms stimulus onset asynchrony (SOA, length of time from onset of prime to onset of target) and half the stimuli had a long 750 ms SOA. In addition, half the words were of high frequency and half of a low frequency. There were no group differences in priming for words of different frequencies. Low schizotypes showed greater priming at the 200 ms SOA than at the 750 ms SOA, whilst individuals with high schizotypy showed the opposite pattern. The pattern shown by the low schizotypes replicates earlier work by the authors using other normal control samples; establishing that there is greater priming under conditions of automatic spreading of activation. Furthermore, the data shows there is not an increase in automatic spreading of activation in individuals with high schizotypy. There has been controversy in the schizophrenia literature over whether there is increased priming under automatic conditions. The current study suggests that, when confounds are controlled for, schizophrenia-like symptoms are not related to an increase in automatic spreading of activation.

Adult↗

PubMed2003

Spelling via semantics and phonology: exploring the effects of age, Alzheimer's disease, and primary semantic impairment.

Spelling performance across a common set of stimuli was examined in young adults, healthy older adults, individuals with early stage dementia of the Alzheimer's type (DAT), and four individuals with a primary semantic impairment (PSI). The stimuli included homophones and low-frequency sound-to-spelling consistent (i.e. words with more predictable spellings) and inconsistent words (i.e. words with less predictable spellings). The results indicate that when spelling homophonic words (spelling/pleIn/ as plane versus plain), younger adults and to a greater extent individuals with PSI placed relatively more emphasis on phonological information (i.e. spell the word based on sound-to-spelling principles) whereas healthy older adults and individuals with DAT placed relatively more emphasis on semantic information (i.e. spell the word based on the dominant usage). For non-homophonic words, large consistency effects (spelling plaid as plad) were observed for both individuals with DAT and individuals with PSI. It is proposed that the decrease in accuracy for inconsistent words has different bases in DAT and PSI. We propose that deficits in attentional control (i.e. selection) underlie performance in DAT whereas disruption of semantic representations underlies performance in PSI.

Acoustic Stimulation↗

PubMed1999

[Deficit of language comprehension in a child with semantic-pragmatic disorder--dissociation between the phonemic and semantic processing abilities].

We studied the language comprehension deficit of a 11-year-old child with a semantic-pragmatic disorder. We used an original test battery using abstract nouns common to the tasks of repetition, reading aloud, auditory comprehension and comprehension of written words. Although he could repeat and read aloud words as good as normal controls, he could not choose correct pictures from semantically or phonemically resembling pictures by listening to or reading target words. This test demonstrated the dissociation between his phonemic and semantic processing abilities. An examination of the cerebral blood flow with SPECT suggested that the dysfunction of the left temporal lobe caused the deficit in language comprehension.

Brain↗

PubMed2000

A voxel-based morphometry study of semantic dementia: relationship between temporal lobe atrophy and semantic memory.

The cortical anatomy of 6 patients with semantic dementia (the temporal lobe variant of frontotemporal dementia) was contrasted with that of a group of age-matched normal subjects by using voxel-based morphometry, a technique that identifies changes in gray matter volume on a voxel-by-voxel basis. Among the circumscribed regions of neuronal loss, the left temporal pole (Brodmann area 38) was the most significantly and consistently affected region. Cortical atrophy in the left hemisphere also involved the inferolateral temporal lobe (Brodmann area 20/21) and fusiform gyrus. In addition, the right temporal pole (Brodmann area 38), the ventromedial frontal cortex (Brodmann area 11/32) bilaterally, and the amygdaloid complex were affected, but no significant atrophy was measured in the hippocampus, entorhinal, or caudal perirhinal cortex. The degree of semantic memory impairment across the 6 cases correlated significantly with the extent of atrophy of the left anterior temporal lobe but not with atrophy in the adjacent ventromedial frontal cortex. These results confirm that the anterior temporal lobe is critically involved in semantic processing, and dissociate its function from that of the adjacent frontal region.

Aged↗

PubMedDate not supplied

Is surface dysgraphia tied to semantic impairment? Evidence from a case of semantic dementia.

Recent models of lexical processing suggest that written spelling partly depends upon the semantic system. According to these models, a deterioration in word meanings would necessarily lead to a spelling impairment, especially for low-frequency and orthographically irregular words. We report a case study of a patient (MK) with semantic dementia who presents impairments in knowledge of word meanings and surface dysgraphia. By specifically identifying concepts that are still known or that are partially or completely deteriorated, we show that the patient's spelling deficit is highly correlated with word comprehension. These data confirm that surface dysgraphia is directly linked to the breakdown in semantic memory.

Aged↗

PubMed2006

Putting semantics into the semantic web: how well can it capture biology?

Could the Semantic Web work for computations of biological interest in the way it's intended to work for movie reviews and commercial transactions? It would be wonderful if it could, so it's worth looking to see if its infrastructure is adequate to the job. The technologies of the Semantic Web make several crucial assumptions. I examine those assumptions; argue that they create significant problems; and suggest some alternative ways of achieving the Semantic Web's goals for biology.

Computational Biology↗

PubMed1999

Functional neuroanatomy of semantic memory: recognition of semantic associations.

In an effort to examine the functional neuroanatomy of semantic memory, we studied the relative cerebral blood flow of eight healthy young subjects using 15O-water positron emission tomography (PET). Relative to a visual baseline control condition, each of four visual matching-to-sample tasks activated components of the ventral visual processing stream, including the inferior occipital and temporal cortices. Contrasting the task with the highest semantic component, a variation on the Pyramids and Palm Trees paradigm, with a size discrimination task resulted in focal activation in the anterior inferior temporal lobe, focused in the parahippocampal gyrus. There was additional activation in BA47 of the inferior frontal cortex. These data replicate and extend previously reported results using similar paradigms, and are consistent with cognitive neuropsychological models that stress the executive role of BA47 in semantic processing tasks.

Adolescent↗

PubMed2004

The role of the temporal lobe semantic system in number knowledge: evidence from late-stage semantic dementia.

Previous reports have demonstrated that many aspects of number knowledge remain unimpaired in semantic dementia, despite severe comprehension problems in other domains. It is argued that this advantage for numbers arises because the disease spares the parietal lobe magnitude system thought to be critical for number processing. Models of numerical cognition that favour a separation between verbal and magnitude representations of number might, however, predict a restricted impairment of the verbal number code in this condition. We obtained support for this hypothesis in a patient with late-stage semantic dementia. She was impaired at a variety of tasks tapping the verbal number code; for example, reading and writing Arabic numerals, naming and word-picture matching with dot pictures, reading aloud number words, digit span and magnitude comparison/serial ordering tasks with number words. In contrast, she demonstrated good understanding of the magnitude and serial order of numbers when tested with Arabic numerals and non-symbolic representations. These findings suggest that although the magnitude meaning of numbers is isolated from the temporal lobe semantic system, the anterior infero-temporal lobe may play a critical role in binding English number words to their non-symbolic magnitude meaning.

Aged↗

PubMed1993

Automatic access to lexical semantics in aphasia: evidence from semantic and associative priming.

We report the auditory lexical decision performance of four patients, all of whom are clinically diagnosed as Broca's aphasics. In a task that separates associative from semantic priming, all four patients show significant priming effects and no interaction with type of relatedness. We find no evidence to support some of the current accounts of these patients' linguistic difficulties in terms of an impairment in automatic processing routines. Instead, we argue that automatic access to lexical semantics is intact.

Adult↗

PubMed1997

Semantic organization, strategy use, and productivity in bilingual semantic verbal fluency.

This study of semantic verbal fluency addressed two research questions: (1) What are the between-language similarities and differences in the performance of balanced bilinguals? (2) What is the relationship between productivity and the use of a semantic grouping strategy to organize responses? Forty neurologically normal, bilingual adults were tested twice in each language (French/English), in a 2 (Language) by 2 (Test) by 2 (Group) design. On Test 2, half the 40 subjects were instructed to group items by subcategory, while half simply repeated the test. Results showed (1) many more between-language similarities than differences and (2) no between-group differences in productivity.

Adult↗

PubMed1989

Semantic abilities in dementia of the Alzheimer type. II. Grammatical semantics.

The grammatical semantic abilities of 18 Alzheimer patients were investigated using picture description tasks and compared to those of a group of institutionalized, nonneurologically impaired control subjects matched for age, sex, and educational level. During picture description, Alzheimer patients showed that they were able to provide as much information about the target picture as control subjects, but were less concise in their verbal representation of the information. The lack of conciseness was reflected in the DAT patients requiring more time and more syllables to communicate a similar quantity of information than the control subjects. The appropriateness of using a picture description task which involves a perceptual step-by-step account of unrelated events to assess sentential semantics and the conveying of information at a conceptual level is discussed.

Alzheimer Disease↗

PubMed1999

Developmental differences in sensitivity to semantic relations among good and poor comprehenders: evidence from semantic priming.

Semantic priming for category coordinates (e.g. CAT-DOG; AEROPLANE-TRAIN) and for pairs of words related through function (e.g. BROOM-FLOOR; SHAMPOO-HAIR) was assessed in children with good and poor reading comprehension, matched for decoding skill. Lexical association strength was also manipulated by comparing pairs of words that were highly associated with pairs that shared low association strength. Both groups of children showed priming for function-related words, but for the category co-ordinates, poor comprehenders only showed priming if the category pairs also shared high association strength. Good comprehenders showed priming for category-related targets, irrespective of the degree of prime-target association. These findings are related to models of language development in which category knowledge is gradually abstracted and refined from children's event-based knowledge and it is concluded that in the absence of explicit co-occurrence, poor comprehenders are less sensitive to abstract semantic relations than normal readers.

Child↗

PubMed1997

One or several semantic system(s)? Maybe none: evidence from a case study of modality and category-specific "semantic" impairment.

Following cerebral anoxia, EC a 55-year-old patient, exhibited a severe and clear-cut pattern of semantic impairments without general intellectual deficit or perceptual difficulty. EC demonstrated a complex neuropsychological picture including a massive visual agnosia and a complete lack of imagery, both of which involved all categories of objects (living and non living) and a category-specific word comprehension deficit limited to animal names. Findings are discussed in the light of the theoretical frameworks currently available in the area of neuropsychology. It is argued that neither the single nor the multiple view of semantics fully succeed in providing a satisfactory account of the data and a tentative interpretation of the whole pattern of impairment is proposed in the general framework of non abstractive conceptions of meaning.

Agnosia↗

PubMed1982

Semantic context effects in visual word recognition, sentence processing, and reading: evidence for semantic strategies.

Earlier research studying the effects of semantic context on single words suggested that subjects may have two strategies for using a context (Becker, 1980). The present research finds that the semantic context strategies may be used in reading short sentences. Further, individual differences in context effects both in a word-level task and in a sentence-level task are related to individual differences in reading continuous text. These results are presented within the framework of the verification model (Becker, 1976, 1980), and the implications for two-process theory (Stanovich & West, 1979, 1981) are discussed.

Adult↗

PubMed1992

Processing phonological and semantic ambiguity: evidence from semantic priming at different SOAs.

Disambiguation of heterophonic and homophonic homographs was investigated in Hebrew using semantic priming. Ambiguous primes were followed by unambiguous targets at 100 ms, 250 ms, and 750 ms stimulus onset asynchrony (SOA). Lexical decision for targets related to the dominant phonological alternatives of heterophonic homographs were facilitated at all SOAs. Targets related to subordinate alternatives were facilitated only at SOAs of 250 ms or longer. When the primes were homophonic homographs, semantic relationship facilitated lexical decision of targets at all SOAs regardless of the dominance of the meaning to which the targets were related. These data can be accounted for by assuming multiple lexical entries for heterophonic homographs, single lexical entries for homophonic homographs, and phonological mediation of accessing meanings. Language-specific factors probably account for the long-lasting activation of subordinate meanings.

Attention↗

PubMed1999

Relearning and subsequent forgetting of semantic category exemplars in a case of semantic dementia.

Over 15 months of longitudinal assessment, a patient with semantic dementia, D.M., improved on tests of naming and category fluency for a specific set of items (Experiment 1). The authors attribute this to his home drill with the names of these concepts plus pictures and descriptions of them. In Experiment 2, D.M. produced significantly more exemplars on category fluency for semantic categories that he had been practicing at home than for nonpracticed categories, an effect that cannot be attributed to an inherent difference between the 2 sets because the fluency performance of control participants revealed no significant difference between the 2 sets. In Experiment 3, D.M. rehearsed some of his previously nonpracticed categories daily for a period of 2 weeks: His fluency scores on the experimental categories improved substantially, but they declined once he ceased the daily drill. The results are discussed with respect to current views of long-term memory, particularly new word learning and forgetting, and to current techniques for facilitating word finding in aphasia.

Aphasia↗

PubMed2006

An efficient method for estimating semantic similarity based on feature overlap: reliability and validity of semantic feature ratings.

Two studies were conducted in which human participants rated pairs of words according to the perceived degree to which the words' referents shared semantic features. The participants found thetask intuitive, simple, and quick to complete. The ratings were reliable and valid. Interrater and interstudy correlations were high, and ratings were good predictors of known feature overlap values obtained from existing semantic feature norms.

Female↗