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PubMed2006

Neural correlates of semantic priming for ambiguous words: an event-related fMRI study.

We investigated the neural correlates of semantic priming by using event-related fMRI to record blood oxygen level dependent (BOLD) responses while participants performed speeded lexical decisions (word/nonword) on visually presented related versus unrelated prime-target pairs. A long stimulus onset asynchrony of 1000 ms was employed, which allowed for increased controlled processing and selective frequency-based ambiguity priming. Conditions included an ambiguous word prime (e.g. bank) and a target related to its dominant (e.g. money) or subordinate meaning (e.g. river). Compared to an unrelated condition, primed dominant targets were associated with increased activity in the LIFG, the right anterior cingulate and superior temporal gyrus, suggesting postlexical semantic integrative mechanisms, while increased right supramarginal activity for the unrelated condition was consistent with expectancy based priming. Subordinate targets were not primed and were associated with reduced activity primarily in occipitotemporal regions associated with word recognition, which may be consistent with frequency-based meaning suppression. These findings provide new insights into the neural substrates of semantic priming and the functional-anatomic correlates of lexical ambiguity suppression mechanisms.

Adult↗

PubMed2005

Lactate infusion fails to improve semantic categorization in Alzheimer's disease.

Impaired neuronal energy metabolism, oxidative changes and microvascular abnormalities lead to altered lactate levels in Alzheimer's dementia. The aim of the present study was to assess whether intravenous sodium-lactate, a metabolic alternative and vasodilator that is thought to improve cognition, advances the cognitive performance of Alzheimer patients. Semantic categorization paradigm was used to present the electrophysiological correlates of natural scene categorization of Alzheimer patients before and after intravenous saline or sodium-lactate infusion. Mean amplitudes of event-related potentials (ERPs) were measured in two time windows before and after the treatments; two negative components (N1 between 150 and 250 ms and N2 between 400 and 600 ms) and one positive component (P2 between 250 and 400 ms) were identified. The negative components were more negative for the non-animal trials than for the animal trials while the positive component was similar for both categories. After the lactate treatment the amplitudes of the negative components became more negative mainly for the non-animal trials while the amplitude of the positive component turned more positive for the animal trials, however these changes were not significant. No changes have been observed after normal saline infusion. These results suggest that, contrary to its anticipated beneficial effects, sodium-lactate fails to significantly improve semantic categorization processes in Alzheimer's disease and this enhancement can be detected by recording ERPs. The effect of sodium-lactate to slightly improve semantic memory might be based on its positive effect on cardio- and cerebro-vascular function and neuronal metabolism.

Aged↗

PubMed2006

Panic patients reveal idiographic associations between anxiety symptoms and catastrophes in a semantic priming task.

In the present study, a modified semantic priming paradigm was used to test whether panic patients more strongly associate catastrophes with anxiety symptoms than nonclinical subjects. Subjects named catastrophic target words (e.g. infarction) and target words neutral to anxiety themes (e.g. weekend) that followed auditive prime sentences immediately (i.e.0ms) or with a delay (i.e. 1500ms). Prime sentences described the perception of anxiety symptoms (e.g. You feel tense) or sensations neutral to anxiety (You feel relaxed). Consistent with an earlier study [Schniering C.A., & Rapee, R.M. (1997). A test of the cognitive model of panic: Primed lexical decision in panic disorder. Journal of Anxiety Disorders, 11, 557-571] the two groups did not differ if semantic priming effects were calculated in the usual way, i.e. by averaging across identical stimuli for all subjects. As expected, however, panic patients demonstrated stronger semantic priming effects for catastrophes immediately following prime sentences if priming effects were calculated for idiographically selected stimuli. The latter result indicated stronger automatic associations between idiographic anxiety symptoms and catastrophes in panic patients consistent with the cognitive model of panic disorder (Clark, D.M. (1986). A cognitive approach to panic. Behaviour Research and Therapy, 24, 461-470). The restriction of stronger associations in panic patients to idiographic stimuli is explained from an evolutionary perspective.

Adolescent↗

PubMed2006

A proposed semantic framework for diabetes education content management, customisation and delivery within the M2DM project.

M2DM (multi access services for telematic management of diabetes mellitus, ) is an EU-funded telemedicine project that aims at increasing the quality of diabetes care by improving communication between patients and caregivers. As part of this project, we have undertaken the initial work of describing the necessary requirements (framework) of an advanced educational component for M2DM in accordance with the latest Semantic Web concepts. This paper describes our proposed semantic framework for educational content management, customisation and delivery. A big internet challenge today is to find and push situation and user-specific quality knowledge to users based on their actual individual needs, circumstances and profiles at any given time. We believe that the semantic framework presented in this paper could be a good step towards meeting this challenge. Benefits for users, both developers and end users, of adopting such framework are also discussed. The ideas discussed in this paper could be easily adapted to other similar services besides M2DM and to different health topics besides diabetes mellitus.

Computer-Assisted Instruction↗

PubMed2005

An ERP study of P600 effects elicited by semantic anomalies.

Syntactic anomalies reliably elicit P600 effects. Recent studies, however, reported P600 effects to semantic anomalies. These findings are difficult to reconcile with the common view on the P600 as a purely syntactic component. The present study--carried out in Dutch--tested the possibility that a P600 to semantic anomalies would nevertheless reflect syntactic processing. We presented semantic reversal anomalies in syntactically correct and unambiguous sentences, like #The cat that fled from the mice.... If participants would use a plausibility strategy and combine the lexical items in the most plausible way, they would--in the case of the example--assume that the mice were fleeing from the cat. Furthermore, this interpretation could lead them to expect a particular inflection of the verb (here: plural inflection). The violation of this expectation could have elicited the P600 effect. Such a syntactic mismatch can occur only in sentences in which the number of theme and agent are different. Therefore, in the present study, the number of theme and agent was either different or the same. A centroparietal P600 effect was present not only in different number sentences but also in same number sentences. Consequently, the P600 effect was not due to a syntactic mismatch, thereby challenging a purely syntactic account of the P600. An alternative view concerning the functional significance of the P600 is discussed, i.e., that it reflects a monitoring component that checks upon the veridicality of ones sentence perception.

Acoustic Stimulation↗

PubMed2005

Semantic processing of unattended meaning is modulated by additional task load: evidence from electrophysiology.

Recently, we observed that the perception of word meaning, as measured with the N400 component of the event-related brain potential, is delayed but unimpaired by various additional tasks when the language task requires the processing of semantic properties of the word stimuli. In the present study, we assessed whether similar effects would be observed when the language task relates to acoustic rather than to semantic properties of the word stimuli. The N400 was elicited by synonymous and non-synonymous spoken noun pairs that were to be classified according to tone pitch. In a single task experiment, there was a small but clear synonymity effect in ERPs (N400), indicating the availability of word meaning to the semantic system. Additional processing load, imposed by an overlapping task, abolished N400 for all SOAs when stimulus-response assignments were incompatible. For compatible assignments, N400 amplitude was present but much attenuated at the longest SOA. We conclude that the availability of task-irrelevant meaning is modulated by additional task load and decay in short-term memory.

Adult↗

PubMed2005

Are semantic and syntactic cues inducing the same processes in the identification of word order?

The purpose of this study was to find a common pattern of event-related potential (ERP) fluctuations regardless of the type of information (either semantic or syntactic) determining the presence of a reversed word order. ERPs were recorded while subjects read Spanish transitive sentences in which either semantic or syntactic information determined the actual word order. On the one hand (semantic condition), the order could be reversed by using an inanimate noun in the first noun phrase (NP), together with a verb representing an action that cannot correspond to an inanimate entity. On the other hand (syntactic condition), word order could be manipulated depending on the presence of a preposition preceding the second NP, which confirms the preferred word order, or a determiner, conveying a reversed word order. Interestingly, the inanimate first noun elicited a frontal negativity, which could be interpreted as the detection of an initial difficulty for using that noun as the subject of the sentence. At the point of disambiguation in either condition, a late posterior positivity was observed. The P600/SPS might, therefore, be an indicator of the syntactic processing costs incurred by the variation of word order, reflecting phrase structure reallocation processes common to this operation regardless of the cue used.

Adult↗

PubMed2005

Semantic divergence and creative story generation: an fMRI investigation.

The aim of this fMRI investigation was to identify those areas of the brain associated with approaching a story generation task creatively and to investigate the effects upon these correlates of incorporating a set of words that were unrelated to each other-a strategy considered to encourage semantic divergence. Preliminary experiments were undertaken to investigate the possible confounding effects of the scanner environment upon creativity and to reveal the effects of creative effort and word relatedness upon the creativity of those who would be participating in the fMRI scan. In the final part of the investigation, a factorial fMRI design was used to elucidate brain regions involved in increased creative effort and also the effect upon activity in these regions when participants incorporated words that bore little semantic relationship with each other. Results support the notion that areas of the right prefrontal cortex are critical to the types of divergent semantic processing involved with creativity in this context.

Adult↗

PubMed2005

Semantic similarity and grammatical class in naming actions.

Italian speakers were asked to name pictures of actions (e.g. "bere", to drink). Pictures were presented at the same time as distracter words that were semantically related or unrelated to the picture names, and were of the same or different grammatical class (verbs or nouns). Half of the participants named the actions as verbs in citation form, the other half as verbs inflected for third person singular or plural. We found a reliable semantic interference effect. Crucially, we also observed a significant interaction between naming context and grammatical class: naming latencies were slower for verb distracters in the inflected form condition, but not in the citation form condition. The results are taken to provide evidence for the separability of semantics and grammatical class.

Humans↗

PubMed2006

Semantic integration in healthcare networks.

A seamless support of information flow for increasingly distributed healthcare processes requires to integrate heterogeneous IT systems into a comprehensive distributed information system. Different standards contribute to ease this integration. In a research project focussing on the development of a reference architecture for inter-institutional health information systems, we identified concurring standards currently in use. We therefore categorized these integration standards by distinguishing between technical and semantic integration on the one hand, and data and functional integration on the other hand. In addition, standards for semantic integration are roughly categorized according to their scope. By placing standards into a corresponding matrix a "semantic gap" is revealed, which cannot be covered by standards as it contains volatile medical concepts. As a conclusion, it is recommended to conceptually consider the necessity of system evolution in system architectures and also in future integration standards.

Hospital Information Systems↗

PubMed2003

OQAFMA Querying agent for the Foundational Model of Anatomy: a prototype for providing flexible and efficient access to large semantic networks.

The development of large semantic networks, such as the UMLS, which are intended to support a variety of applications, requires a flexible and efficient query interface for the extraction of information. Using one of the source vocabularies of UMLS as a test bed, we have developed such a prototype query interface. We first identify common classes of queries needed by applications that access these semantic networks. Next, we survey StruQL, an existing query language that we adopted, which supports all of these classes of queries. We then describe the OQAFMA Querying Agent for the Foundational Model of Anatomy (OQAFMA), which provides an efficient implementation of a subset of StruQL by pre-computing a variety of indices. We describe how OQAFMA leverages database optimization by converting StruQL queries to SQL. We evaluate the flexibility and efficiency of our implementation using English queries written by anatomists. This evaluation verifies that OQAFMA provides flexible, efficient access to one such large semantic network, the Foundational Model of Anatomy, and suggests that OQAFMA could be an efficient query interface to other large biomedical knowledge bases, such as the Unified Medical Language System.

Abstracting and Indexing↗

PubMed2005

The elicitation of phonological and semantic neuromagnetic field components by non-words in human auditory sentence comprehension.

The current research examined whether neuromagnetic field components relating to pre-lexical and semantic analysis would be evoked by non-word violations in Japanese auditory sentence comprehension. Stimuli contained semantically congruent short vowel-duration words, long vowel-duration non-words, and short-duration non-words with a deviant second syllable. Native speakers listened to sentences, while neuromagnetic fields were recorded with a twin 37-channel gradiometer system. The results in the 200-400 ms time window showed that at a peak latency of approximately 300 ms, vowel-lengthening and deviant-syllable violations produced larger magnetic fields than congruent words. In the 450-600 ms time range, the magnetic fields in response to deviant-syllable violations, but not vowel-lengthening violations, were larger than congruent words, with the peak latency at approximately 500 ms. The elicitations of M300 and M500 components in this study support the biphasic hypothesis where a pre-lexical phonological analysis stage precedes a post-lexical semantic integration stage in lexical recognition of a native language.

Acoustic Stimulation↗

PubMed2005

Modulation of the semantic system by word imageability.

A prevailing neurobiological theory of semantic memory proposes that part of our knowledge about concrete, highly imageable concepts is stored in the form of sensory-motor representations. While this theory predicts differential activation of the semantic system by concrete and abstract words, previous functional imaging studies employing this contrast have provided relatively little supporting evidence. We acquired event-related functional magnetic resonance imaging (fMRI) data while participants performed a semantic similarity judgment task on a large number of concrete and abstract noun triads. Task difficulty was manipulated by varying the degree to which the words in the triad were similar in meaning. Concrete nouns, relative to abstract nouns, produced greater activation in a bilateral network of multimodal and heteromodal association areas, including ventral and medial temporal, posterior-inferior parietal, dorsal prefrontal, and posterior cingulate cortex. In contrast, abstract nouns produced greater activation almost exclusively in the left hemisphere in superior temporal and inferior frontal cortex. Increasing task difficulty modulated activation mainly in attention, working memory, and response monitoring systems, with almost no effect on areas that were modulated by imageability. These data provide critical support for the hypothesis that concrete, imageable concepts activate perceptually based representations not available to abstract concepts. In contrast, processing abstract concepts makes greater demands on left perisylvian phonological and lexical retrieval systems. The findings are compatible with dual coding theory and less consistent with single-code models of conceptual representation. The lack of overlap between imageability and task difficulty effects suggests that once the neural representation of a concept is activated, further maintenance and manipulation of that information in working memory does not further increase neural activation in the conceptual store.

Adolescent↗

PubMed2006

Meta-analyzing left hemisphere language areas: phonology, semantics, and sentence processing.

The advent of functional neuroimaging has allowed tremendous advances in our understanding of brain-language relationships, in addition to generating substantial empirical data on this subject in the form of thousands of activation peak coordinates reported in a decade of language studies. We performed a large-scale meta-analysis of this literature, aimed at defining the composition of the phonological, semantic, and sentence processing networks in the frontal, temporal, and inferior parietal regions of the left cerebral hemisphere. For each of these language components, activation peaks issued from relevant component-specific contrasts were submitted to a spatial clustering algorithm, which gathered activation peaks on the basis of their relative distance in the MNI space. From a sample of 730 activation peaks extracted from 129 scientific reports selected among 260, we isolated 30 activation clusters, defining the functional fields constituting three distributed networks of frontal and temporal areas and revealing the functional organization of the left hemisphere for language. The functional role of each activation cluster is discussed based on the nature of the tasks in which it was involved. This meta-analysis sheds light on several contemporary issues, notably on the fine-scale functional architecture of the inferior frontal gyrus for phonological and semantic processing, the evidence for an elementary audio-motor loop involved in both comprehension and production of syllables including the primary auditory areas and the motor mouth area, evidence of areas of overlap between phonological and semantic processing, in particular at the location of the selective human voice area that was the seat of partial overlap of the three language components, the evidence of a cortical area in the pars opercularis of the inferior frontal gyrus dedicated to syntactic processing and in the posterior part of the superior temporal gyrus a region selectively activated by sentence and text processing, and the hypothesis that different working memory perception-actions loops are identifiable for the different language components. These results argue for large-scale architecture networks rather than modular organization of language in the left hemisphere.

Brain Mapping↗

PubMed2006

Language lateralization and the role of the fusiform gyrus in semantic processing in young children.

We used blood oxygen-dependent (BOLD) fMRI technique at 1.5 T to examine brain regions associated with language comprehension in normally developing children, age 5 to 10 years. Twenty-three children participated in the study using an auditory semantic decision task which varied in task difficulty. Analysis of individual participants' data showed patterns of activation largely consistent with previous neuroimaging findings in adult language processing. Group data analysis also showed a strong left-lateralized pattern of activation that closely resembles those typically observed in adults. In addition, significant activation in the left fusiform gyrus was observed and was associated with task accuracy. This finding suggests that auditory semantic processing in young children may recruit cortical regions associated with word reading in adults prior to the initiation of a semantic category decision, a process which is consistent with patterns of early word recognition process and language development.

Age Factors↗

PubMed2006

The impact of semantic reference on word class: an fMRI study of action and object naming.

There is a considerable body of neuropsychological and neuroimaging evidence supporting the distinction between the brain correlates of noun and verb processing. It is however still not clear whether the observed differences are imputable to grammatical or semantic factors. Beyond the basic difference that verbs typically refer to actions and nouns typically refer to objects, other semantic distinctions might play a role as organizing principles within and across word classes. One possible candidate is the notion of manipulation and manipulability, which may modulate the word class dissociation. We used functional magnetic resonance imaging (fMRI) to study the impact of semantic reference and word class on brain activity during a picture naming task. Participants named pictures of objects and actions that did or did not involve manipulation. We observed extensive differences in activation associated with the manipulation dimension. In the case of manipulable items, for both nouns and verbs, there were significant activations within a fronto-parietal system subserving hand action representation. However, we found no significant effect of word class when all verbs were compared to all nouns. These results highlight the impact of the biologically crucial sensorimotor dimension of manipulability on the pattern of brain activity associated to picture naming.

Adult↗

PubMed2006

Semantic ambiguity processing in sentence context: Evidence from event-related fMRI.

Lexical semantic ambiguity is the phenomenon when a word has multiple meanings (e.g. 'bank'). The aim of this event-related functional MRI study was to identify those brain areas, which are involved in contextually driven ambiguity resolution. Ambiguous words were selected which have a most frequent, dominant, and less frequent, subordinate meaning. These words were presented in two types of sentences: (1) a sentence congruent with the dominant interpretation and (2) a sentence congruent with the subordinate interpretation. Sentences without ambiguous words served as a control condition. The ambiguous words always occurred early in the sentences and were biased towards one particular meaning by the final word(s) of the sentence; the event at the end of the sentences was modeled. The results indicate that a bilaterally distributed network supports semantic ambiguity comprehension: left (BA 45/44) and right (BA 47) inferior frontal gyri and left (BA 20/37) and right inferior/middle temporal gyri (BA 20). The pattern of activation is most consistent with a scenario in which initially a frequency-based probabilistic choice is made between the alternative meanings, and the meaning is updated when this interpretation does not fit into the final disambiguating context. The neural pattern is consistent with the results of other neuroimaging experiments which manipulated various aspects of integrative and context processing task demands. The presence of a bilateral network is also in line with the lesion and divided visual field literature, but contrary to earlier claims, the two hemispheres appear to play similar roles during semantic ambiguity resolution.

Adult↗

PubMed2004

The impact of lexical-semantic impairment and of executive dysfunction on the word reading performance of patients with probable Alzheimer dementia.

The influence of lexical-semantic impairment and of executive dysfunction on word naming performance was investigated in a group of patients with probable Alzheimer dementia (AD). The patients, who varied in the severity of the illness, were tested in a word naming task where they had to read aloud Italian three-syllable words with a dominant or subordinate stress pattern. These types of words have been shown to interact with frequency in normal adults [J. Exp. Psychol.: Hum. Percept. Perform. 18 (4) (1992) 987], so that the effect of the subordinate stress pattern (slower reading times) is only apparent for low frequency words. The frequency and stress effects on accuracy increased across dementia severity levels. Regression analyses showed that the impairment in reading low frequency words with subordinate stress depended largely on the level of lexical-semantic impairment, measured by a test of semantic memory and comprehension. Implications for the current reading models are discussed.

Aged↗