[Semantics of the radiographic picture. Comparative semantic content in cardiovascular radiology, seriography and cineradiography].
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Cardiovascular Diseases↗
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A semantic lexicon for medical language processing.
OBJECTIVE: Construction of a resource that provides semantic information about words and phrases to facilitate the computer processing of medical narrative. DESIGN: Lexemes (words and word phrases) in the Specialist Lexicon were matched against strings in the 1997 Metathesaurus of the Unified Medical Language System (UMLS) developed by the National Library of Medicine. This yielded a "semantic lexicon," in which each lexeme is associated with one or more syntactic types, each of which can have one or more semantic types. The semantic lexicon was then used to assign semantic types to lexemes occurring in a corpus of discharge summaries (603,306 sentences). Lexical items with multiple semantic types were examined to determine whether some of the types could be eliminated, on the basis of usage in discharge summaries. A concordance program was used to find contrasting contexts for each lexeme that would reflect different semantic senses. Based on this evidence, semantic preference rules were developed to reduce the number of lexemes with multiple semantic types. RESULTS: Matching the Specialist Lexicon against the Metathesaurus produced a semantic lexicon with 75,711 lexical forms, 22,805 (30.1 percent) of which had two or more semantic types. Matching the Specialist Lexicon against one year's worth of discharge summaries identified 27,633 distinct lexical forms, 13,322 of which had at least one semantic type. This suggests that the Specialist Lexicon has about 79 percent coverage for syntactic information and 38 percent coverage for semantic information for discharge summaries. Of those lexemes in the corpus that had semantic types, 3,474 (12.6 percent) had two or more types. When semantic preference rules were applied to the semantic lexicon, the number of entries with multiple semantic types was reduced to 423 (1.5 percent). In the discharge summaries, occurrences of lexemes with multiple semantic types were reduced from 9.41 to 1.46 percent. CONCLUSION: Automatic methods can be used to construct a semantic lexicon from existing UMLS sources. This semantic information can aid natural language processing programs that analyze medical narrative, provided that lexemes with multiple semantic types are kept to a minimum. Semantic preference rules can be used to select semantic types that are appropriate to clinical reports. Further work is needed to increase the coverage of the semantic lexicon and to exploit contextual information when selecting semantic senses.
Humans↗
[Schizophrenia and semantic priming effects].
INTRODUCTION: This article is a review of studies using the semantic priming paradigm to assess the functioning of semantic memory in schizophrenic patients. CONTEXT: Semantic priming describes the phenomenon of increasing the speed with which a string of letters (the target) is recognized as a word (lexical decision task) by presenting to the subject a semantically related word (the prime) prior to the appearance of the target word. This semantic priming is linked to both automatic and controlled processes depending on experimental conditions (stimulus onset asynchrony (SOA), percentage of related words and explicit memory instructions). Automatic process observed with short SOA, low related word percentage and instructions asking only to process the target, could be linked to the "automatic spreading activation" through the semantic network. Controlled processes involve "semantic matching" (the number of related and unrelated pairs influences the subjects decision) and "expectancy" (the prime leads the subject to generate an expectancy set of potential target to the prime). These processes can be observed whatever the SOA for the former and with long SOA for the later, but both with only high related word percentage and explicit memory instructions. LITERATURE FINDINGS: Studies evaluating semantic priming effects in schizophrenia show conflicting results: schizophrenic patients can present hyperpriming (semantic priming effect is larger in patients than in controls), hypopriming (semantic priming effect is lower in patients than in controls) or equal semantic priming effects compared to control subjects. DISCUSSION: These results could be associated to a global impairment of controlled processes in schizophrenia, essentially to a dysfunction of semantic matching process. On the other hand, efficiency of semantic automatic spreading activation process is controversial. These discrepancies could be linked to the different experimental conditions used (duration of SOA, proportion of related pairs and instructions), which influence on the degree of involvement of controlled processes and therefore prevent to really assess its functioning. In addition, manipulations of the relation between prime and target (semantic distance, type of semantic relation and strength of semantic relation) seem to influence reaction times. However, the relation between prime and target (mediated priming) frequently used could not be the most relevant relation to understand the way of spreading of activation in semantic network in patients with schizophrenia. Finally, patients with formal thought disorders present particularly high priming effects relative to controls. CONCLUSION: These abnormal semantic priming effects could reflect a dysfunction of automatic spreading activation process and consequently an exaggerated diffusion of activation in the semantic network. In the future, the inclusion of different groups schizophrenic subjects could allow us to determine whether semantic memory disorders are pathognomonic or specific of a particular group of patients with schizophrenia.
Cerebral Cortex↗
Nature of personal semantic memory: evidence from Alzheimer's disease.
Personal semantic memory is factual knowledge about a person's own past. Although personal semantic memory is assumed to have features of both semantic memory and episodic memory, the relationship to episodic memory and to semantic memory have not been well documented. In patients with Alzheimer's disease, episodic memory, semantic memory, and personal semantic memory are all defective. In this study, the hypothesis that defective personal semantic memory is related to both semantic and episodic memory dysfunction was tested in patients with Alzheimer's disease. Functions of episodic, semantic, and personal semantic memory were examined by using the Wechsler Memory Scale-Revised (WMS-R), subtests of the WAIS-R (Information, Vocabulary, Comprehension and Similarities), and the Family Line Test (FLT) in 62 patients who met the NINCDS/ADRDA criteria for probable Alzheimer's disease. Specific effects of episodic and semantic memory on personal semantic memory were examined by using multiple linear regression analysis with the total score of the FLT as the dependent variable and the WMS-R Delayed Recall weighted sum score and the WAIS-R Semantic Memory score (a composite of standardized scores of the four subtests) as the independent variables. Personal semantic memory function was significantly correlated with both the episodic and semantic memory functions, after controlling age, sex, educational attainment, and severity of dementia. This result supports the hypotheses that personal semantic memory has features of both episodic and semantic memory, and that semantic memory is transformed from episodic memory.
Aged↗
Semantic memory loss in dementia of Alzheimer's type. What do various measures measure?
This paper examines three methodological issues concerning the measurement of semantic memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of semantic memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their semantic memory store without visual perceptual deficits. The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of semantic memory. It was found that verbal fluency (generation of semantic category lists) was impaired due to two major constraints: deterioration of semantic memory store, and variable difficulties in semantic search. Verbal fluency, therefore, reflects semantic memory loss to some degree, but is not a direct test of semantic memory store in DAT. The second issue was whether semantic memory impairment in our patients conformed to the 'semantic storage disorder' syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether semantic cueing and semantic priming are altered in a similar manner in DAT. It demonstrated that semantic cueing and semantic priming, using the same words whose concepts were degraded in semantic memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of semantic loss after brain damage.
Aged↗
A PET study of stimulus- and task-induced semantic processing.
To investigate the neural correlates of semantic processing, previous functional imaging studies have used semantic decision and generation tasks. However, in addition to activating semantic associations these tasks also involve executive functions that are not specific to semantics. The study reported in this paper aims to dissociate brain activity due to stimulus-driven semantic associations and task-induced semantic and executive processing by using repetition and semantic decision on auditorily presented words in a cognitive conjunction design. The left posterior inferior temporal, inferior frontal (BA 44/45), and medial orbital gyri were activated by both tasks, suggesting a general role in stimulus-driven semantic and phonological processing. In addition, semantic decision increased activation in (i) left ventral inferior frontal cortex (BA 47), right cerebellum, and paracingulate, which have all previously been implicated in executive functions, and (ii) a ventral region in the left anterior temporal pole which is commonly affected in patients with semantic impairments. We attribute activation in this area to the effortful linkage of semantic features. Thus, our study replicated the functional dissociation between dorsal and ventral regions of the left inferior frontal cortex. Moreover, it also dissociated the semantic functions of the left posterior inferior temporal gyrus and anterior temporal pole: The posterior region subserves stimulus-driven activation of semantic associations and the left anterior region is involved in task-induced association of semantic information.
Adult↗
Semantic and episodic memory in aphasia.
Within the framework of the distinction between episodic and semantic memory, it has been argued that these two memory Systems are organised in a hierarchical way. The hierarchical hypothesis assumes that episodic memory is a specific subsystem of semantic memory and therefore implies that episodic memory cannot exist without semantic memory. If this hypothesis is correct, it should be expected that (episodic) yes/no recognition performance would improve in patients with preserved semantic memory, following semantic encoding. In the present study we investigated the influence of semantic encoding on recognition memory performance in a population of 28 aphasic patients (AA) and 14 normal controls (NC). Experiment 1 considered recognition memory for semantically unrelated items, whereas Experiments 2 and 3 assessed recognition memory for semantically related items. In Experiment 3, but not in Experiment 2, subjects were explicitly instructed to make a semantic association between the items. AA were impaired, compared to NC, only on the recognition memory performance of Experiment 1. The ability to make a semantic association between two items was significantly and positively correlated to the ability to recognise, in a subsequent test, those same items. A further analysis showed that patients who were impaired on the semantic association task did significantly worse on the recognition task of Experiment 3 than NC and than patients who were unimpaired on the semantic association task. These findings are discussed in the context of memory deficits in aphasia and interpreted as giving support to the view that episodic memory for an item is affected by the level of semantic awareness of that same item.
Aphasia↗
A lexical metaschema for the UMLS semantic network.
OBJECTIVE: A metaschema is a high-level abstraction network of the UMLS's semantic network (SN) obtained from a partition of the SN's collection of semantic types. Every metaschema has nodes, called meta-semantic types, each of which denotes a group of semantic types constituting a subject area of the SN. A new kind of metaschema, called the lexical metaschema, is derived from a lexical partition of the SN. The lexical metaschema is compared to previously derived metaschemas, e.g., the cohesive metaschema. DESIGN: A new lexical partitioning methodology is presented based on identical word-usage among the names of semantic types and the definitions of their respective children. The lexical metaschema is derived from the application of the methodology. We compare the constituent meta-semantic types and their underlying semantic-type groups with the previously derived cohesive metaschema. A similar comparison of the lexical partition and a published partition of the SN is also carried out. RESULTS: The lexical partition of the SN has 21 semantic-type groups, each of which represents a subject area. The lexical metaschema thus has 21 meta-semantic types, 19 meta-child-of hierarchical relationships, and 86 meta-relationships. Our comparison shows that 15 out of the 21 meta-semantic types in the lexical metaschema also appear in the cohesive metaschema, and 80 semantic types are covered by identical meta-semantic types or refinements between the two metaschemas. The comparison between the lexical partition and the semantic partition shows that they have very low similarity. CONCLUSION: The algorithmically derived lexical metaschema serves as an abstraction of the SN and provides views representing different subject areas. It compares favorably with the cohesive metaschema derived via the SN's relationship configuration.
Abstracting and Indexing↗
Consistency across the hierarchies of the UMLS Semantic Network and Metathesaurus.
OBJECTIVE: To develop and test a method for automatically detecting inconsistencies between the parent-child is-a relationships in the Metathesaurus and the ancestor-descendant relationships in the Semantic Network of the Unified Medical Language System (UMLS). METHODS: We exploited the fact that each Metathesaurus concept is assigned one or more semantic types from the UMLS Semantic Network and that the semantic types are arranged in a hierarchy. We compared the semantic types of each pair of parent and child concepts to determine if the types "explained" the Metathesaurus is-a relationships. We considered cases where the semantic type of the parent was neither the same as, nor an ancestor of, the semantic type of the child to be "unexplained." We applied this method to the January 2002 release of the UMLS and examined the unexplained cases we discovered to determine their causes. RESULTS: We found that 17022 (24.3%) of the parent-child is-a relationships in the UMLS Metathesaurus could not be explained based on the semantic types of the concepts. Causes for these discrepancies included cases where the parent or child was missing a semantic type, cases where the semantic type of the child was too general or the semantic type of the parent was too specific, cases where the parent-child relationship was incorrect, and cases where an ancestor-descendant relationship should be added to the UMLS Semantic network. In many cases, the specific cause of the discrepancy cannot be resolved without authoritative judgment by the UMLS developers. CONCLUSIONS: Our method successfully detects inconsistencies between the hierarchies of the UMLS Metathesaurus and Semantic Network. We believe that our method should be added to the set of tools that the UMLS developers use to maintain and audit the UMLS knowledge sources.
Abstracting and Indexing↗
Knowledge of famous faces and names in semantic dementia.
Semantic dementia is a focal clinical syndrome, resulting from degeneration of the temporal lobes and characterized by progressive loss of conceptual knowledge about the world. Because of the highly circumscribed nature of the disorder it is a natural model for improving understanding of how semantic information is cerebrally represented. There is currently a lack of consensus. One view proposes the existence of modality specific meaning systems, in which visual and verbal information are stored separately. An opposing view assumes that information is represented by a unitary, amodal semantic system. The present study explores these alternatives in an examination of famous face and name knowledge in 15 patients with semantic dementia. The study of face recognition in patients with an established semantic disorder also permits an examination of the relationship between semantic dementia and the focal clinical syndrome of progressive prosopagnosia. The semantic dementia patients were profoundly impaired on both face and name identification and familiarity judgement tasks compared with amnesic patients with Alzheimer's disease and healthy controls. However, whereas the two reference groups performed better for names than faces, the semantic group showed the opposite pattern. This overall profile masked individual differences: semantic dementia patients with predominant left temporal lobe atrophy showed better recognition of names than faces, whereas patients with right temporal predominance showed the reverse pattern. Relative superiority for names or faces was mirrored by corresponding superiority for words or pictures on a standard semantic test. We interpret the findings as inconsistent with a unitary, amodal model of semantic memory. However, the data are not wholly compatible with a strict multiple system account. The data favour a model of semantic memory comprising a single interconnected network, with dedicated brain regions representing modality specific information. The data emphasize the importance of the anterior, inferolateral parts of the left temporal lobe for the representation of names and the corresponding parts of the right temporal lobe for faces. Dissociations between face and name knowledge provide a challenge for existing models of face processing. Moreover, they lead us to argue that the focal syndrome of progressive prosopagnosia is one of the clinical presentations of semantic dementia and not a separate clinical entity.
Aged↗
Semantic encoding and retrieval in the left inferior prefrontal cortex: a functional MRI study of task difficulty and process specificity.
Prefrontal cortical function was examined during semantic encoding and repetition priming using functional magnetic resonance imaging (fMRI), a noninvasive technique for localizing regional changes in blood oxygenation, a correlate of neural activity. Words studied in a semantic (deep) encoding condition were better remembered than words studied in both easier and more difficult nonsemantic (shallow) encoding conditions, with difficulty indexed by response time. The left inferior prefrontal cortex (LIPC) (Brodmann's areas 45, 46, 47) showed increased activation during semantic encoding relative to nonsemantic encoding regardless of the relative difficulty of the nonsemantic encoding task. Therefore, LIPC activation appears to be related to semantic encoding and not task difficulty. Semantic encoding decisions are performed faster the second time words are presented. This represents semantic repetition priming, a facilitation in semantic processing for previously encoded words that is not dependent on intentional recollection. The same LIPC area activated during semantic encoding showed decreased activation during repeated semantic encoding relative to initial semantic encoding of the same words. This decrease in activation during repeated encoding was process specific; it occurred when words were semantically reprocessed but not when words were nonsemantically reprocessed. The results were apparent in both individual and averaged functional maps. These findings suggest that the LIPC is part of a semantic executive system that contributes to the on-line retrieval of semantic information.
Adolescent↗
ERP analyses of task effects on semantic processing from words.
Semantic (positive) priming refers to the facilitated processing of a probe word when preceded by a related prime word, and is a widely used technique for investigating semantic activation. However, the effect is interrupted or eliminated when attention is directed to low-level features of the prime word, such as its letters, a result which has been used to question the automaticity of semantic processing. We investigated this issue using both behavioural [reaction time (RT)] and electrophysiological measures [event-related potentials (ERPs)]. Subjects performed semantic categorization (living vs. nonliving) and letter search ("A" or "E") tasks on prime words followed by lexical decision on the probe. RT results showed the expected elimination of semantic priming following letter search. However, both prime tasks were affected by the semantic category of the prime, indicating that the meaning was processed. The ERP results supported this conclusion: an early component previously associated with automatic semantic processing [the Recognition Potential (RP)] was sensitive to the category of the prime word irrespective of the prime task. However, a later component (N400) was significantly affected by the task, in both the prime (categorization task) and probe words (semantic priming). The results dissociate rapid, automatic semantic processing from semantic priming. We suggest that a later inhibitory control mechanism suppresses this semantic activation when it is not relevant to the task, and that this produces the loss of semantic priming.
Adolescent↗
Semantic representation of consumer questions and physician answers.
The aim of this study was to identify the underlying semantics of health consumers' questions and physicians' answers in order to analyze the semantic patterns within these texts. We manually identified semantic relationships within question-answer pairs from Ask-the-Doctor Web sites. Identification of the semantic relationship instances within the texts was based on the relationship classes and structure of the Unified Medical Language System (UMLS) Semantic Network. We calculated the frequency of occurrence of each semantic relationship class, and conceptual graphs were generated, joining concepts together through the semantic relationships identified. We then analyzed whether representations of physician's answers exactly matched the form of the question representations. Lastly, we examined characteristics of the answer conceptual graphs. We identified 97 semantic relationship instances in the questions and 334 instances in the answers. The most frequently identified semantic relationship in both questions and answers was brings_about (causal). We found that the semantic relationship propositions identified in answers that most frequently contain a concept also expressed in the question were: brings_about, isa, co_occurs_with, diagnoses, and treats. Using extracted semantic relationships from real-life questions and answers can produce a valuable analysis of the characteristics of these texts. This can lead to clues for creating semantic-based retrieval techniques that guide users to further information. For example, we determined that both consumers and physicians often express causative relationships and these play a key role in leading to further related concepts.
Humans↗
Auditing the Unified Medical Language System with semantic methods.
OBJECTIVE: The National Library of Medicine's (NLM) Unified Medical Language System (UMLS) includes a Metathesaurus (Meta), which is a compilation of medical terms drawn from over 30 controlled vocabularies, and a Semantic Net, which contains the semantic types used to categorize Meta concepts and the semantic relations to connect them. Meta has been constructed through lexical matching techniques and human review. The purpose of this study was to audit the Meta using semantic techniques to identify possible inconsistencies. METHODS: Five different techniques were applied: (1) detection of ambiguity in Meta concepts with two or more semantic types, (2) detection of interchangeable keyword synonyms, (3) detection of redundant pairs of Meta concepts (using lexical matching combined with keyword synonyms), (4) detection of inconsistent parent-child relationships in Meta (based on the semantic type information), and (5) discovery of pairs of semantic types for which relations could be added to the Semantic Net, based on "other" relationships between Meta concepts. RESULTS: Of 57,592 concepts with multiple semantic types, 1817 (3.2%) were judged to be ambiguous. Keyword analysis showed 7121 pairs of interchangeable words. Using the keyword pairs, 5031 pairs of potentially redundant concepts were suggested, of which 3274 (65.1%) were judged to actually be redundant. Review of the 100,586 parent-child relationships revealed 544 (0.54%) that were incorrect. Review of the 219,664 "Other" relationships suggested 1299 places in the Semantic Net where relations between pairs of semantic types could be added. CONCLUSION: Semantic techniques, alone or in combination, can be used to audit the UMLS to detect inconsistencies that are not detectable through lexical techniques alone. Use of these methods to augment the UMLS maintenance process will lead to improvement in the UMLS.
Algorithms↗
Dissociation of automatic and strategic lexical-semantics: functional magnetic resonance imaging evidence for differing roles of multiple frontotemporal regions.
Behavioral research has demonstrated three major components of the lexical-semantic processing system: automatic activation of semantic representations, strategic retrieval of semantic representations, and inhibition of competitors. However, these component processes are inherently conflated in explicit lexical-semantic decision tasks typically used in functional magnetic resonance imaging (fMRI) research. Here, we combine the logic of behavioral priming studies and the neurophysiological phenomenon of fMRI priming to dissociate the neural bases of automatic and strategic lexical-semantic processes across a series of three studies. A single lexical decision task was used in all studies, with stimulus onset asynchrony or linguistic relationship between prime and target being manipulated. Study 1 demonstrated automatic semantic priming in the left mid-fusiform gyrus (mid-FFG) and strategic semantic priming in five regions: left middle temporal gyrus (MTG), bilateral anterior cingulate, anterior left inferior prefrontal cortex (aLIPC), and posterior LIPC (pLIPC). These priming effects were explored in more detail in two subsequent studies. Study 2 replicated the automatic priming effect in mid-FFG and demonstrated that automatic priming in this region is preferential for the semantic domain. Study 3 demonstrated a neural dissociation in regions contributing to the strategic semantic priming effect. Strategic semantic facilitation was observed in the aLIPC and MTG, whereas strategic semantic inhibition was observed in the pLIPC and anterior cingulate. These studies provide reproducible evidence for a neural dissociation between three well established components of the lexical-semantic processing system.
Adolescent↗
Distinct behavioural profiles in frontotemporal dementia and semantic dementia.
OBJECTIVE: To test predictions that frontotemporal dementia and semantic dementia give rise to distinct patterns of behavioural change. METHODS: An informant based semistructured behavioural interview, covering the domains of basic and social emotions, social and personal behaviour, sensory behaviour, eating and oral behaviour, repetitive behaviours, rituals, and compulsions, was administered to carers of 41 patients with semantic dementia and with apathetic (FTD-A) and disinhibited (FTD-D) forms of frontotemporal dementia. RESULTS: Consistent with prediction, emotional changes differentiated FTD from semantic dementia. Whereas lack of emotional response was pervasive in FTD, it was more selective in semantic dementia, affecting particularly the capacity to show fear. Social avoidance occurred more often in FTD and social seeking in semantic dementia. Patients with FTD showed reduced response to pain, whereas patients with semantic dementia more often showed exaggerated reactions to sensory stimuli. Gluttony and indiscriminate eating were characteristic of FTD, whereas patients with semantic dementia were more likely to exhibit food fads. Hyperorality, involving inedible objects, was unrelated to gluttony, indicating different underlying mechanisms. Repetitive behaviours were common in both FTD and semantic dementia, but had a more compulsive quality in semantic dementia. Behavioural differences were greater between semantic dementia and FTD-A than FTD-D. A logistic regression analysis indicated that emotional and repetitive, compulsive behaviours discriminated FTD from semantic dementia with 97% accuracy. CONCLUSION: The findings confirm predictions regarding behavioural differences in frontotemporal and semantic dementia and point to differential roles of the frontal and temporal lobes in affect, social functioning, eating, and compulsive behaviour.
Behavior↗
The influence of semantic encoding on recognition memory in Alzheimer's disease.
Within the framework of the distinction between episodic and semantic memory, it has been argued that these two memory systems are organised in a hierarchical way. The hierarchical hypothesis assumes that episodic memory is a specific subsystem of semantic memory and therefore implies that episodic memory cannot exist without semantic memory. If this hypothesis is correct, it should be expected that patients with impaired semantic memory also have impaired episodic memory. In the present study, two experiments investigated the influence of semantic encoding on recognition memory performance in a population of 20 patients with Alzheimer's disease and 18 normal controls. Both experiments assessed recognition memory for semantically-related items. In Experiment 2, but not in Experiment 1, subjects were explicitly instructed to make a semantic association between the items. Alzheimer's disease patients were impaired, compared to the normal controls, on the recognition memory performance of both experiments. The ability to make a semantic association between two items was significantly and positively correlated with the subjects' performance on the recognition tasks. A further analysis showed that patients who were impaired on the semantic association task did significantly worse on the recognition task of Experiment 2 than normal controls and patients who were unimpaired on the semantic association task. These findings are discussed in the context of memory deficits in Alzheimer's disease, and are interpreted as supporting the view that episodic memory for an item is affected by the level of semantic awareness of that same item.
Aged↗
The anatomy and time course of semantic priming investigated by fMRI and ERPs.
We combined complementary non-invasive brain imaging techniques with behavioural measures to investigate the anatomy and time course of brain activity associated with semantic priming in a lexical-decision task. Participants viewed pairs of stimuli, and decided whether the second item was a real word or not. There were two variables, the semantic relationship between the prime and the target (related or unrelated) and the interval between the onset of prime and target (200 or 1000 ms), to vary the degree of semantic expectancy that was possible during task performance. Behavioural results replicated the well-established finding that identification of the target is facilitated by a preceding semantically related prime. Event-related functional magnetic resonance imaging (efMRI) identified two brain areas involved in the semantic-priming effect. Activity in the anterior medial temporal cortex was diminished when target words were primed by semantically related words, suggesting involvement of this brain region during active semantic association or integration. In contrast, activity in the left supramarginal gyrus in the temporal-parietal junction was enhanced for target words primed by semantically related words. Brain areas influenced by the interval between prime and target words, and by the interaction between word interval and semantic priming were also identified. A parallel experiment using event-related potentials (ERPs) unveiled a striking difference in the time course of semantic priming as a function of expectancy. In line with previous reports, the primary effect of semantic priming on ERPs was the attenuation of the N400 component, in both short- and long-interval conditions. However, the priming effect started significantly earlier in the long-interval condition. Activity in the anterior medial temporal cortex has previously been shown to contribute to the N400 component, a finding that links the priming results obtained with efMRI and ERP methods.
Adult↗