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PubMed1992

Semantic memory: complexity or connectivity?

The complexity hypothesis predicts that concept-feature verification times should be directly related to the number of features associated with a concept (the fan effect). Conversely, the connectivity hypothesis predicts that for interconnected semantic relationships, this verification time should be inversely related to the number of closely associated features (the reversed fan effect). In the present experiments, although the time required for episodic recognition memory decisions tended to be directly related to the number of features associated with a concept, semantic verification times were inversely related to the complexity of the concept. In addition, the concept's complexity was at least as good a predictor of performance in semantic tasks as was the strength of association between the concept and feature. Both of these results are interpreted in terms of the connectivity hypothesis.

Adult↗

PubMed1994

A reevaluation of semantic versus nonsemantic processing in implicit memory.

A number of investigations have purported to demonstrate that semantic processing does not produce a memorial advantage over nonsemantic processing on implicit tests, as contrasted with the typical advantage of semantic over nonsemantic processing on explicit tests. A review of 166 outcomes from 38 studies that have manipulated processing on implicit tests reveals that on 131 occasions (79%), priming was greater following semantic than it was following nonsemantic processing. This difference was found in both perceptual and conceptual implicit memory tests, as well as in within- and between-subjects designs. It suggests that implicit tests reflect the involvement of both conceptual and perceptual processes. Although explicit contamination may account for some of the processing difference in implicit tests, the pervasiveness of the phenomenon, especially in perceptual implicit tests, makes it an unlikely account for the entire effect.

Attention↗

PubMed1991

Influences of semantic and syntactic context on open- and closed-class words.

Event-related potentials (ERPs) were recorded as subjects read semantically meaningful, syntactically legal but nonsensical and random word strings. The constraints imposed by formal sentence structure alone did not reduce the amplitude of the N400 component elicited by open-class words, whereas semantic constraints did. Semantic constraints also eliminated the word-frequency effect of a larger N400 for low-frequency words. Responses to closed-class words exhibited reduced N400 amplitudes in syntactic and congruent sentences, indicating that formal sentence structure placed greater restrictions on closed-class words than it did on open-class words. However, unlike the open-class results, the impact of sentence context on closed-class words was stable across word positions, suggesting that these syntactic constraints were applied only locally. A second ERP component, distinct from the N400, was elicited primarily by congruent closed-class words.

Adolescent↗

PubMed2000

Effects of antecedent order and semantic context on Chinese pronoun resolution.

Three reading time experiments were conducted in order to examine the relative contributions of order of antecedents and semantic context to the resolution of temporarily ambiguous Chinese pronouns. These pronouns were ambiguous because each of them was preceded by two antecedents, both of which were likely candidates for coreference. The identity of the pronoun was revealed by subsequent disambiguating information that constrained the pronoun to one particular interpretation. Experiment 1 showed that reading of the disambiguating phrase was slower when the phrase confined the pronoun to the second rather than to the first antecedent. Experiment 2 produced the same effect of antecedent order (first vs. second antecedent) regardless of whether the target antecedent was an action-performing or an action-receiving entity. In Experiment 3, the order effect was eliminated by a biasing modifier inserted immediately before the pronoun. These results indicate that in a semantically neutral environment, the first-appearing antecedent is the preferred candidate for coreferencing the ambiguous Chinese pronoun. The interaction between order of antecedents and semantic context (in the form of preposed biasing modifiers) suggests that the initial comprehension of Chinese pronouns depends as much on contextual as on structural factors.

Adult↗

PubMed1989

Semantic facilitation and translation priming effects in Chinese-English bilinguals.

In two experiments, semantic facilitation and translation priming effects in Chinese-English bilingual speakers were demonstrated with a lexical decision task. A 300-msec stimulus-onset asynchrony (SOA) was used between display of the prime and the target item. Experiment 1 showed that subjects' lexical decision responses were facilitated to a greater extent when primed by a translation equivalent than a semantically related between-language word. In Experiment 2, we found that pictorial, between-language, and within-language primes produced comparable effects of semantic facilitation. These results are in line with the hypothesis that lexical items in different languages and pictures are processed by means of an amodal conceptual system.

Adult↗

PubMed1994

Phonological codes are early sources of constraint in visual semantic categorization.

Two experiments were directed at early phonological activation in the semantic categorization task. In Experiment 1, briefly exposed targets homophonic to category exemplars (ROWS for the category A FLOWER), and their graphemic controls (ROBS), were judged for category membership with and without a backward pattern mask. False positives were greater for ROWS than ROBS to the same degree under both unmasked and masked conditions. In Experiment 2, false positives were examined in the semantic categorization task under backward dichoptic masking by pseudowords that were, in turn, masked monoptically by a pattern mask. Briefly exposed homophones (e.g., WEAK), masked by a phonologically similar pseudoword ("feek"), a graphemic control ("felk"), or an unrelated pseudoword ("furt"), were categorized as category exemplars (A UNIT OF TIME). The difference in false positives was significant for WEAK-feek versus WEAK-furt, but not for WEAK-felk versus WEAK-furt. It was suggested that the persistence of the homophonic effects under the pattern masking of Experiment 1 and their amplification under the phonological masking of Experiment 2 were because phonological codes cohere rapidly and provide, thereby, immediately available constraints on semantic processing.

Adult↗

PubMed1989

Semantic priming: subliminal perception or context?

Briefly presented, masked priming stimuli that cannot be identified by themselves can affect the processing of subsequent targets. The effect, which is sometimes viewed as a demonstration of unconscious processing, has been linked to the subliminal perception literature. Experiments 1 and 2 indicated that the identification of primes in the context of semantically related targets is superior to the identification of primes presented alone, and that the identification of primes in the context of semantically unrelated targets is inferior to the identification of primes presented alone. Experiment 3 indicated parallel findings in a recognition task. Consequently, an explanation of semantic priming in terms of the interactive nature of stimuli that are near to one another in time seems preferable to one based upon concepts of unconscious processing and subliminal perception.

Adult↗

PubMed1999

Deficits in lexical and semantic processing: implications for models of normal language.

The investigation of language processing following brain damage may be used to constrain models of normal language processing. We review the literature on semantic and lexical processing deficits, focusing on issues of representation of semantic knowledge and the mechanisms of lexical access. The results broadly support a componential organization of lexical knowledge-the semantic component is independent of phonological and orthographic form knowledge, and the latter are independent of each other. Furthermore, the results do not support the hypothesis that word meaning is organized into modality-specific subcomponents. We also discuss converging evidence from functional imaging studies in relation to neuropsychological results.

Cognition Disorders↗

PubMed1999

The time course of phonological, semantic, and orthographic coding in reading: evidence from the fast-priming technique.

The present experiment employed the fast-priming paradigm in reading (Sereno & Rayner, 1992), in which sentences are silently read while eye-movement-contingent changes are made on a specified target region. In this paradigm, when readers fixate on a specified target word region, a prime word is encountered for a brief duration at the beginning of the fixation and then it is replaced by a target word. Three types of primes were employed: homophones, semantically related, and orthographically similar, and five prime durations were employed: 29, 32, 35, 38, and 41 msec. The primary finding was that significant homophone priming was obtained at prime durations ranging from 29 to 35 msec, whereas significant semantic priming occurred only at the 32-msec prime duration. In contrast, significant orthographic priming occurred at all prime durations. These findings indicate that phonological codes are activated during an eye fixation at least as rapidly as semantic codes. An explanation for the pattern of events is suggested using the framework of an activation-verification model.

Adult↗

PubMed1990

Semantic priming in the pronunciation task: the role of prospective prime-generated expectancies.

In the relatedness proportion effect, semantic priming increases with an increase in the probability that a word prime will be followed by a semantically related word target. This effect has frequently been obtained in the lexical decision task but not in a pronunciation task. In the present experiment, relatedness proportion was manipulated in two pronunciation tasks, one with and one without nonword targets, using category names as primes. In both tasks, a relatedness proportion effect occurred for high-dominance category exemplars but not for low-dominance category exemplars. These results converge with recent lexical decision results in suggesting that semantic priming in pronunciation is affected by a prospective prime-generated expectancy that is modulated by the relatedness proportion.

Adult↗

PubMed2003

The neural basis of autobiographical and semantic memory: new evidence from three PET studies.

A novel, neuropsychologically informed paradigm (extended retrieval of events in response to a cue word) was used to investigate the neural basis of autobiographical and semantic memory. Contrasting retrieval of autobiographical memories with retrieval of semantic facts (ABM-SEM) in 24 subjects across three PET studies revealed bilateral involvement of the middle temporal gyrus (BA 21) and medial frontal cortex (BA 9/10). The opposite contrast, SEM-ABM, resulted in increased regional cerebral blood flow in left posterior temporal regions (BA 37) and left prefrontal cortex (BA 45/46). Laterality maps suggest that the bilateral pattern seen in our studies, but not often in other neuroimaging investigations, reflects the use of a task stressing retrieval of specific personal events. Further comparisons revealed that the activation in the right anterior temporal lobe during autobiographical recall was virtually identical to that seen during retrieval of information about famous people or events in contrast with retrieval of general semantic facts. These findings suggest that the retrieval of an autobiographical event requires participation from conceptual knowledge, and that this type of knowledge is bilaterally distributed in the temporal lobes.

Adult↗

PubMed2000

Phonological and semantic fluencies are mediated by different regions of the prefrontal cortex.

Verbal phonological and semantic fluencies were investigated in 24 patients with unilateral prefrontal lesions and 10 normal control subjects. Lesions were limited to small areas within either the dorsolateral (Brodmann's area 46/9) or ventromedial (posterior part of the gyrus rectus) cortices. In a phonological fluency task, patients with lesions to the left dorsolateral region were impaired. In semantic fluency, not only the left dorsolateral group but also the two right frontal damaged groups performed worse than the control group. In agreement with previous studies, our results show that the phonological fluency is mediated by the left dorsolateral prefrontal cortex. In contrast to this, performance on the semantic fluency task depends on a wider portion of the prefrontal cortex involving the left and right dorsolateral and the right ventromedial areas.

Adult↗

PubMedDate not supplied

[Semantic verbal fluency in neurological patients without dementia with a low educational level].

INTRODUCTION AND OBJECTIVE: The Semantic Verbal Fluency Test (sVFT) is very sensitive to cognitive deterioration. Standard values are usually those found in normal persons with an average or high cultural level. We analyze the results of a sVFT in a broad sample of persons assessed in a Neurology Clinic so as to find the standard values in this particular population. PATIENTS AND METHODS: A sVFT (animals in one minute) was given to 138 patients without dementia, aged over 55 years, assessed in the Neurology Clinic. Variables recorded were sex, age, years of schooling, studies completed, diagnosis and place of origin. A bivariate descriptive study and multivariate lineal regression analysis was done following a 'step by step' strategy. RESULTS: This group had a low educational level (72% had been to school for less than 10 years), with an average +/- standard error of 16.02 +/- 0.45 animals in one minute. The variables: years of schooling, sex, age and diagnosis showed a significant association with semantic verbal fluency in the adjusted regression model. CONCLUSIONS: Our values are lower than those of other standard groups. This may be related to the low educational level of our group and to the inclusion of persons with neurological disorders. The lineal regression model proposed permits prediction of the values of semantic verbal fluency in specific persons depending on their personal characteristics.

Aged↗

PubMed1999

MEDTAG: tag-like semantics for medical document indexing.

Medical documentation is central in health care, as it constitutes the main means of communication between care providers. However, there is a gap to bridge between storing information and extracting the relevant underlying knowledge. We believe natural language processing (NLP) is the best solution to handle such a large amount of textual information. In this paper we describe the construction of a semantic tagset for medical document indexing purposes. Rather than attempting to produce a home-made tagset, we decided to use, as far as possible, standard medicine resources. This step has led us to choose UMLS hierarchical classes as a basis for our tagset. We also show that semantic tagging is not only providing bases for disambiguisation between senses, but is also useful in the query expansion process of the retrieval system. We finally focus on assessing the results of the semantic tagger.

Abstracting and Indexing↗

PubMed1999

Streamlining semantic interpretation for medical narratives.

We introduce two abstraction mechanisms by which the process of semantic interpretation of medical narratives can be simplified and further optimized. One relates to generalized triggering conditions, the other to inheritance-based specifications of semantic rules. The proposed methodology leads to a parsimonious inventory of abstract, simple and domain-independent semantic interpretation schemata whose effectiveness has been evaluated on a medical text corpus.

Evaluation Studies as Topic↗

PubMed1999

[Episodic and semantic memory after traumatic brain injury in a child].

In an early-life, a memory disturbance affects the learning and school record directly. Furthermore, it may cause the problem of maltreatment or adaptation difficulty for school life. We report a child amnesia caused by a traumatic brain injury when she was 9 years old. We examined her episodic and semantic memory. We developed 3-steps tasks of recognition and recall for the post-accident episodic memory. First, the examiner presented the patient with four words orally including a label of her episode, and asked her to choose one that she felt familiar with (the recognition of the episodic label). Second, if the word she selected was correct, she was required to recall the episode related to the word (the recall of the episode). Third, if she could not recall the episode herself correctly, she was required to choose a correct sentence about the episode (the recognition of the episode). She could not recall episodes correctly, but produced confabulation instead. She showed, however, good recognition of each episode. Furthermore, we performed recognition tests of time, person, and place about the same post-accident episodes, which were poor especially for time. In semantic memory tasks, we examined about kanji characters (ideogram) learned from the first grade to the sixth grade and mathematical knowledge learned from the second grade to the sixth grade at elementary school ("What centimeters is equal to one meter?" or "Tell me the formula of the size of a circle." etc). We found that she showed a retrograde impairment for about one year. For both episodic and semantic memory, she showed an anterograde impairment. Because of the anterograde amnesia she could not acquire new facts, and also showed para-amnesia or confabulation. In a child with brain damage, neuropsychological assessment is important in predicting effect of rehabilitation and recovery of school performance.

Adolescent↗

PubMedDate not supplied

Pattern of semantic memory impairment in dementia of Alzheimer's type.

The specific pattern of semantic memory impairment in patients with dementia of Alzheimer's type (DAT) remains unclear. Specifically, the presence of a category-specific deficit for biological concepts (reflected in anomia for these concepts) has been questioned. We studied 9 DAT patients using a semantic association judgement test in which they had to decide which of the two given words was most like a target word (e.g., lamb: goat, sheep). The 150 target words were drawn from 6 categories: animals, clothing and furniture, fruits and vegetables, tools, action verbs, and abstract nouns. Age- and education-matched control subjects performed equivalently (between 86 and 90% correct) in all categories. Compared to control subjects, DAT patients made significantly more errors in abstract and biological nouns, but not in verbs and man-made artifacts. This pattern of semantic memory impairment--a sparing of verbs and a selective deficit of nouns in the biological category--has been documented in patients with temporal lobe damage, suggesting a critical dysfunction in the temporal lobes of DAT.

Aged↗

PubMedDate not supplied

Spatial and temporal organization of episodic and semantic processes revealed by event-related potentials to unfamiliar faces.

This study investigated whether the semantic and episodic processes underlying the old/new effect can be dissociated by analyzing the spatial and temporal characteristics of event-related potentials (ERPs) evoked by unfamiliar face stimuli during direct and indirect memory tests. The ERP old/new effects obtained included three components. First, the classical posterior component, present in both tasks, which was thus interpreted as reflecting changes in the automatic activation of semantic representation. Second, an earlier frontal component, present in the direct test only, which was seen a consequence of the building of a contextual representation of presented items formed of a conjunction of elements stored in semantic memory. Third, a late right-temporal component, in the direct test, which was related to the integration of this conjunction into a unitized representation of the presented stimuli.

Adult↗