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PubMed2004

An fMRI study with semantic access in low proficiency second language learners.

Brain activity was measured with fMRI in twelve 10- to 12-year-old Chinese children who began learning English when they were 8 years old in order to find out whether there is a common or a distinct neural semantic system for native language (L1) and second language (L2) in low proficiency bilingual subjects. Although they performed less well in L2 in the semantic decision task administered during fMRI measurement, these subjects showed similar robust activation, for both languages, in brain areas involved in semantic processing (e.g. the left inferior frontal cortex). Within-subject and group analyses revealed no significant difference in the activation patterns for L1 and L2 in these regions. These results suggest that at least at single-word level, there are shared neural substrates for semantic processing of L1 and L2 even when one is at a very low L2 proficiency level.

Brain↗

PubMed1993

Semantic structures and psychiatric diagnosis.

This study examines psychiatric diagnosis using the concepts and methods of cognitive anthropology. Clinicians are viewed as cultural experts whose knowledge is represented in semantic structures, which are arrangements of diagnostic categories based on similarity of meaning. A test of similarity judgments of diagnostic categories was administered to a group of clinicians to derive two semantic structures of the categories included in axis I and axis II, respectively, of DSM-III. These structures were then compared with actual clinical diagnoses of concurrent disorders, and with the expected incidence of such diagnoses, in order to determine the possible influence of semantic similarity on the diagnostic process. The results suggest that semantic meanings of diagnostic categories influence the use of rule-out diagnoses more than positive diagnoses, and that this influence is more pronounced with respect to axis II than axis I.

Anthropology, Cultural↗

PubMed1992

Progressive loss of semantic memory in a case of Alzheimer's disease.

The breakdown of semantic memory in a patient with Alzheimer's disease was monitored by using a word-picture matching task. Performance deteriorated from a time when target pictures were selected virtually without error to a time when targets and semantically related distractor pictures were selected equally often. From this point, selection deteriorated rapidly to random. Knowledge of category membership and semantic features declined together over the same period. No consistency in item selection could be discerned, and successful selection in early tests was not influenced by either the name frequency or the familiarity of the target. The findings are argued to support a theory of access to semantic memory which is non-hierarchical.

Alzheimer Disease↗

PubMed2005

Knowledge representation and sharing using visual semantic modeling for diagnostic medical image databases.

Information technology offers great opportunities for supporting radiologists' expertise in decision support and training. However, this task is challenging due to difficulties in articulating and modeling visual patterns of abnormalities in a computational way. To address these issues, well established approaches to content management and image retrieval have been studied and applied to assist physicians in diagnoses. Unfortunately, most of the studies lack the flexibility of sharing both explicit and tacit knowledge involved in the decision making process, while adapting to each individual's opinion. In this paper, we propose a knowledge repository and exchange framework for diagnostic image databases called "evolutionary system for semantic exchange of information in collaborative environments" (Essence). This framework uses semantic methods to describe visual abnormalities, and offers a solution for tacit knowledge elicitation and exchange in the medical domain. Also, our approach provides a computational and visual mechanism for associating synonymous semantics of visual abnormalities. We conducted several experiments to demonstrate the system's capability of matching synonym terms, and the benefit of using tacit knowledge in improving the meaningfulness of semantic queries.

Artificial Intelligence↗

PubMed2003

Semantic integration in videos of real-world events: an electrophysiological investigation.

Event-related potentials (ERPs) discriminated between contextually appropriate and inappropriate objects appearing in video film clips of common activities. Incongruent objects elicited a larger negative-going deflection, which was similar to the N400 component described previously in association with words and static pictures and which has been argued to reflect the integration of semantic information into a mental representation of the preceding context. The onset of this potential occurred shortly after object presentation, indicating that semantic integration is a rapid online component of real-world perception. In addition, the anomalies in movies evoked a large late positive potential at posterior regions, suggesting that in event perception, semantic incongruity may trigger cognitive processes other than those mediating pure semantic integration.

Adolescent↗

PubMed2003

The influence of semantic and phonological factors on syntactic decisions: an event-related brain potential study.

During language production and comprehension, information about a word's syntactic properties is sometimes needed. While the decision about the grammatical gender of a word requires access to syntactic knowledge, it has also been hypothesized that semantic (i.e., biological gender) or phonological information (i.e., sound regularities) may influence this decision. Event-related potentials (ERPs) were measured while native speakers of German processed written words that were or were not semantically and/or phonologically marked for gender. Behavioral and ERP results showed that participants were faster in making a gender decision when words were semantically and/or phonologically gender marked than when this was not the case, although the phonological effects were less clear. In conclusion, our data provide evidence that even though participants performed a grammatical gender decision, this task can be influenced by semantic and phonological factors.

Adult↗

PubMed2004

Repetition and semantic priming of nonwords: implications for theories of N400 and word recognition.

ERPs were elicited by two types of orthographically legal, pronounceable nonwords. One nonword set was derived from and resembled real words, whereas the other set did not. Nonwords derived from related root words elicited N400 semantic priming effects similar to those obtained for words, indicating semantic activation of the root words. N400 repetition priming effects from nonderived nonwords were similar to those obtained for words. The elicitation of N400 by only derived nonwords would have suggested it was generated by the activation of word meanings, per se. However, both types of nonwords produced an N400, and an N400 priming effect. Because nonderived nonwords are not associated with meaning, the N400 cannot be generated by semantic activation per se. Rather, the N400 appears to be generated by orthographic/phonological analysis and is attenuated by the top-down feed of semantic information to the orthographic/phonological level.

Adult↗

PubMed2005

Detecting silent pauses in speech: a new tool for measuring on-line lexical and semantic processing.

In this study, we introduce pause detection (PD) as a new tool for studying the on-line integration of lexical and semantic information during speech comprehension. When listeners were asked to detect 200-ms pauses inserted into the last words of spoken sentences, their detection latencies were influenced by the lexical-semantic information provided by the sentences. Listeners took longer to detect a pause when it was inserted within a word that had multiple potential endings, rather than a unique ending, in the context of the sentence. An event-related potential (ERP) variant of the PD procedure revealed brain correlates of pauses as early as 101 to 125 ms following pause onset and patterns of lexical-semantic integration that mirrored those obtained with PD within 160 ms of pause onset. Thus, both the behavioral and the electrophysiological responses to pauses suggest that lexical and semantic processes are highly interactive and that their integration occurs rapidly during speech comprehension.

Humans↗

PubMed2006

Object substitution masking interferes with semantic processing: evidence from event-related potentials.

Object substitution masking (OSM) refers to impaired target identification caused by common onset, but delayed offset, of a surrounding dot mask. This effect has been hypothesized to reflect reentrant processes that result in the mask replacing the target representation. However, little is known about the depth of processing associated with masked targets in this paradigm. We investigated this issue by examining the effect of OSM on the N400 component of the event-related potential, which reflects the degree of semantic mismatch between a target and its context. Participants read a context word followed by a semantically related or unrelated target word surrounded by dots. As expected, delayed dot offset significantly reduced accuracy in identifying the target. The N400 amplitude was also diminished by OSM. These findings offer the first evidence that substitution interferes with target processing prior to semantic analysis, demonstrating an important difference between OSM and other visual phenomena, such as the attentional blink, in which semantic processing is independent of awareness.

Adolescent↗

PubMed2005

Morphed facial expressions elicited a N400 ERP effect: a domain-specific semantic module?

Previous studies have revealed that decoding of facial expressions is a specific component of face comprehension and that semantic information might be processed separately from the basic stage of face perception. In order to explore event-related potentials (ERPs) related to recognition of facial expressions and the effect of the semantic content of the stimulus, we analyzed 20 normal subjects. Faces with three prototypical emotional expressions (fear, happiness, and sadness) and with three morphed expressions were presented in random order. The neutral stimuli represented the control condition. Whereas ERP profiles were similar with respect to an early negative ERP (N170), differences in peak amplitude were observed later between incongruous (morphed) expressions and congruous (prototypical) ones. In fact, the results demonstrated that the emotional morphed faces elicited a negative peak at about 360 ms, mainly distributed over the posterior site. The electrophysiological activity observed may represent a specific cognitive process underlying decoding of facial expressions in case of semantic anomaly detection. The evidence is in favor of the similarity of this negative deflection with the N400 ERP effect elicited in linguistic tasks. A domain-specific semantic module is proposed to explain these results.

Adult↗

PubMed1997

Emotional and semantic priming as a measure of information processing in young people with school refusal: a research note.

We investigated semantic and emotional priming of lexical decision-making in 20 school refusers and 20 attenders aged 11-16 years, matched for sex and reading ability. We hypothesised that: semantic and emotional priming would be demonstrable in both samples; and that the school refusers would show emotional priming of school-related words to aversive primes. Both samples showed semantic priming; emotional priming was shown by the attenders and 11 school refusers without a history of depression. School-refusing children did not show emotional priming for school-related words. Nine school-refusing children with either current or past depression showed a general reduction in their priming. These results show that both semantic and emotional priming can be detected in this age-range. They do not support school refusal being typically associated with anxiety about school. The reduction in priming in those with a depressive history is similar to inhibition in information processing in depressed adults. Priming is therefore sensitive to at least some psychiatrically relevant states or traits in this age-range. It is concluded that priming could be a useful measure of information processing in this age-group, and further research is warranted.

Adolescent↗

PubMed1993

Electrophysiological evidence for task effects on semantic priming in auditory word processing.

Event-related brain potentials (ERPs) associated with semantic relatedness were recorded in two auditory word recognition tasks. In the Memorize task, subjects listened to a list of words in anticipation of a subsequent recognition test. In the Count Nonwords task, subjects silently counted the number of nonwords occurring within a list of words. Within each list, target words were either semantically related or unrelated to the immediately preceding word. As in comparable visual tasks, the amplitude of a negative ERP component (N400) was significantly attenuated when targets were preceded by semantically related primes. This attenuation was greater in the Memorize than in the Count Nonwords task. These data are consistent with the view that the sensitivity of N400 amplitude to semantic relatedness is modulated by task variables that manipulate depth of processing.

Adult↗

PubMed1997

When syntax meets semantics.

Three experiments concerning the processing of syntactic and semantic violations were conducted. Event-related potentials (ERPs) showed that semantic violations elicited an N400 response, whereas syntactic violations elicited two early negativities (150 and 350 ms) and a P600 response. No interaction between the semantic and early syntactic ERP effects was found. Sentence complexity and violation probability (25% vs. 75%) affected only the P600 and not the early negativities. The probability effect was taken as evidence that the P600 resembles the P3b. The temporal order of word processing in a sentence as suggested by the data was such that a more automatic syntactic analysis was performed (earlier syntactic-related negativities) in parallel with a semantic analysis (N400), after which a syntactic reanalysis was performed (P600). A reanalysis interpretation of the P600 could explain why the extent of the reanalysis differed with syntactic complexity and probability of ungrammaticality.

Adult↗

PubMed1994

The nature of semantic priming effects in the recognition of familiar people.

We report a series of experiments examining the nature of semantic priming effects in the recognition of familiar people. Experiment 1 showed that facilitation of the recognition of familiar target faces by related face primes occurs within the recognition system, since there is no equivalent priming when subjects are asked only to determine the sex of the target faces, rather than to recognize them as familiar. Experiments 2 and 3 examined the basis of the facilitatory effect of related primes, and showed that both for familiarity decision (Expt 2 and Expt 3) and face naming (Expt 3) tasks it is primarily based on close association of the prime and target people, rather than common membership of a semantic category. This associative component of semantic priming was further explored in Expt 4, which showed that cross-domain priming from face primes to target names was present for associated prime-target pairs, but was maximal when prime and target were the face (prime) and name (target) of the same person. The results of the experiments are consistent with the interactive activation simulation developed by Burton, Bruce & Johnston (1990), and set constraints which will have to be met by any other plausible account of semantic priming.

Face↗

PubMed2000

Imaginal, semantic, and surface-level processing of concrete and abstract words: an electrophysiological investigation.

Words representing concrete concepts are processed more quickly and efficiently than words representing abstract concepts. Concreteness effects have also been observed in studies using event-related brain potentials (ERPs). The aim of this study was to examine concrete and abstract words using both reaction time (RT) and ERP measurements to determine (1) at what point in the stream of cognitive processing concreteness effects emerge and (2) how different types of cognitive operations influence these concreteness effects. Three groups of subjects performed a sentence verification task in which the final word of each sentence was concrete or abstract. For each group the truthfulness judgment required either (1) image generation, (2) semantic decision, or (3) evaluation of surface characteristics. Concrete and abstract words produced similar RTs and ERPs in the surface task, suggesting that postlexical semantic processing is necessary to elicit concreteness effects. In both the semantic and imagery tasks, RTs were shorter for concrete than for abstract words. This difference was greatest in the imagery task. Also, in both of these tasks concrete words elicited more negative ERPs than abstract words between 300 and 550 msec (N400). This effect was widespread across the scalp and may reflect activation in a linguistic semantic system common to both concrete and abstract words. ERPs were also more negative for concrete than abstract words between 550 and 800 msec. This effect was more frontally distributed and was most evident in the imagery task. We propose that this later anterior effect represents a distinct ERP component (N700) that is sensitive to the use of mental imagery. The N700 may reflect the a access of specific characteristics of the imaged item or activation in a working memory system specific to mental imagery. These results also support the extended dual-coding hypothesis that superior associative connections and the use of mental imagery both contribute to processing advantages for concrete words over abstract words.

Adult↗

PubMed2002

Object activation from features in the semantic system.

The human brain is thought to elicit an object representation via co-activation of neural regions that encode various object features. The cortical regions and mechanisms involved in this process have never been elucidated for the semantic system. We used functional magnetic resonance imaging (fMRI) to evaluate regions activated during a task designed to elicit object activation within the semantic system (e.g., presenting the words "desert" and "humps" with the task to determine if they combine to form an object, in this case a "camel"). There were signal changes in the thalamus for word pairs that activated an object, but not for pairs that (a) failed to activate an object, (b) were simply semantically associated, or (c) were members of the same category. These results suggest that the thalamus has a critical role in coordinating the cortical activity required for activating an object concept in the semantic system.

Adult↗

PubMed2002

Exploring the activation of semantic and phonological codes during speech planning with event-related brain potentials.

We present a new technique for studying the activation of semantic and phonological codes in speech planning using event-related brain potentials (ERPs) that extend a well-established behavioral procedure from speech production research. It combines a delayed picture-naming task with a priming procedure. While participants prepared the production of a depicted object's name, they heard an auditory target word. If the prepared picture name and the target word were semantically or phonologically related, the ERP waveform to the target word tended less towards the negative when compared to an unrelated control. These effects were widely distributed. By contrast, if participants performed a nonlinguistic task on the depicted object (natural size judgment), the semantic effect was still obtained while the phonological effect disappeared. This suggests that the former effect indexes semantic activation involved in object processing while the latter effect indexes word-form activation specific to lexical processing. The data are discussed in the context of models of lexical access in speech production.

Acoustic Stimulation↗

PubMed2003

An event-related FMRI investigation of implicit semantic priming.

The neural basis underlying implicit semantic priming was investigated using event-related fMRI. Prime-target pairs were presented auditorily for lexical decision (LD) on the target stimulus, which was either semantically related or unrelated to the prime, or was a nonword. A tone task was also administered as a control. Behaviorally, all participants demonstrated semantic priming in the LD task. fMRI results showed that for all three conditions of the LD task, activation was seen in the superior temporal gyrus (STG), the middle temporal gyrus (MTG), and the inferior parietal lobe, with greater activation in the unrelated and nonword conditions than in the related condition. Direct comparisons of the related and unrelated conditions revealed foci in the left STG, left precentral gyrus, left and right MTGs, and right caudate, exhibiting significantly lower activation levels in the related condition. The reduced activity in the temporal lobe suggests that the perception of the prime word activates a lexical-semantic network that shares common elements with the target word, and, thus, the target can be recognized with enhanced neural efficiency. The frontal lobe reductions most likely reflect the increased efficiency in monitoring the activation of lexical representations in the temporal lobe, making a decision, and planning the appropriate motor response.

Acoustic Stimulation↗