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PubMedDate not supplied

The impact of semantic transparency of morphologically complex words on picture naming.

We examined the contribution of semantic similarity to morphological priming effects, using the immediate (Exp. 1 and 3) and the delayed variant (Exp. 2) of picture-word interference. Distractor words were either compounds morphologically related to the picture name, but differing with respect to their semantic transparency (hummingbird, jailbird (Exp. 1); butterfly, butter dish (Exp. 3)), or form-related non-compound words (e.g., trombone). All three experiments revealed strong facilitation of picture naming due to morphologically related distractors. Form-related distractors facilitated picture naming in the immediate variant only, and to a lesser degree than compounds. Interestingly, the size of the morphemic effect was almost identical for semantically transparent and opaque complex words, which suggests that they share morphemic representations. These results suggest that morphological complexity in speech production is coded at the level of form representations, independent of semantic transparency.

Humans↗

PubMed2002

Semantic analysis of auditory input during sleep: studies with event related potentials.

This review summarises the results of event-related potentials studies exploring the extent to which the human brain can extract semantic information from external stimuli during sleep. The persistence of a differential response to the subject's own name, relative to any other proper name, during stage 2 (S2) and paradoxical (REM) sleep (PS) suggests that the brain remains able to discriminate an intrinsically relevant word during these sleep stages. The similarities and the differences between these sleep cognitive responses and the waking P300 are stressed, and the functional significance of this component discussed especially in relation with consciousness and memory of the stimulus. Recent studies of the 'N400' potential evoked by semantically incongruous words, have shown that this component may be also elicited during S2 and PS, indicating preserved detection of semantic discordance during these sleep stages. However, linguistic incongruity appears to be processed in a different manner during PS than during waking, since words devoid of meaning (pseudo-words), which are detected as anomalous and evoke N400 during waking, yielded responses similar to those of congruous words in PS. All these data support the view that some semantic analysis of auditory stimuli remains possible in the human sleeping brain, and warrant further studies to elucidate the extent and limits of these capabilities.

Acoustic Stimulation↗

PubMedDate not supplied

Lexical and semantic factors influencing picture naming in aphasia.

Picture naming requires early visual analysis, accessing stored structural knowledge, semantic activation, and lexical retrieval. We tested the effect of perceptual, lexical, and semantic variables on the performance of aphasics in picture naming and assessed prevalence of natural categories vs artifact dissociations. Forty-nine aphasics were asked to name 60 pictures, from three natural (animals, fruits, and vegetables) and three artificial categories (tools, furniture, and vehicles). For each item visual (drawing complexity, image agreement), semantic (prototypicality, concept familiarity) and lexical variables (word frequency, name agreement) were available. The effect of these variables showed individual differences; altogether, visual complexity had little influence, whereas lexical and semantic variables were more influential. Name agreement was most important, followed by word frequency. On a multiple single case analysis 10 patients (20%) showed a natural/artificial category dissociation. Five of the six subjects faring better with artifacts were males, and all of four patients faring better with natural categories were females. Interpretations of this finding are discussed.

Adolescent↗

PubMedDate not supplied

Contribution of visual and semantic proximity to identification performance in a viral encephalitis patient.

Identification deficits were investigated in F.S., a patient with herpes simplex viral encephalitis. F.S.'s confrontation naming abilities were assessed for multiple repetitions of 12 line drawings of artifacts. Six of the line drawings consisted of psychologically "close" objects (i.e., objects that share many visual and semantic features with other objects) and 6 were psychologically "disparate" objects (i.e., objects that share few, if any, visual and semantic features with other objects). F.S. correctly named all of the objects from the "disparate" category but only 47% of the objects from the "close" category. We also tested F.S. using novel, computer-generated shapes that were paired with artifact labels. We paired semantically close or disparate labels to shapes and F.S. attempted to learn these pairings. Overall, F.S.'s shape-label confusions were most detrimentally affected when we used labels that referred to objects that were visually close and semantically distinct. Results indicate that, at least for our patient, visual similarity contributed the most to his identification errors.

Encephalitis, Herpes Simplex↗

PubMed1997

Molecular semantics and the origin of life.

The physical origin of life addresses itself to a semantic process on material grounds, in which causation toward contextualization is at work. Physically semantic process of whatever kind is specific in that every material participant is searching and modifying the material context to be fitted in. Fundamental to the physical semantics is the process of measurement proceeding internally among the constituent material participants, whereas the molecular syntax alone as embodied in the form of the quantum-mechanical equation of motion supplemented independently by exogenous boundary conditions cannot cope with the material process underlying the origin. A basic physical attribute of the phenomenon called life is variable duration, in contrast to invariant duration of Galilean inertia. In fact, moleculars replication thought as a harbinger of the phenomenon of life is a concrete form of variable duration and could be established unless internal measurement being instrumental to physically semantic process is forcibly eliminated by some external means. Physical experiments on the onset of molecular replication could become feasible only when external controllability over the intended experiments even at nano-meter scales is abandoned so as to save the room of internal measurement on the part of participating molecules.

Biological Evolution↗

PubMed2001

Recovering meaning: left prefrontal cortex guides controlled semantic retrieval.

Prefrontal cortex plays a central role in mnemonic control, with left inferior prefrontal cortex (LIPC) mediating control of semantic knowledge. One prominent theory posits that LIPC does not mediate semantic retrieval per se, but rather subserves the selection of task-relevant knowledge from amidst competing knowledge. The present event-related fMRI study provides evidence for an alternative hypothesis: LIPC guides controlled semantic retrieval irrespective of whether retrieval requires selection against competing representations. With selection demands held constant, LIPC activation increased with semantic retrieval demands and with the level of control required during retrieval. LIPC mediates a top-down bias signal that is recruited to the extent that the recovery of meaning demands controlled retrieval. Selection may reflect a specific instantiation of this mechanism.

Adolescent↗

PubMed2002

Common prefrontal regions coactivate with dissociable posterior regions during controlled semantic and phonological tasks.

One of the most ubiquitous findings in functional neuroimaging research is activation of left inferior prefrontal cortex (LIPC) during tasks requiring controlled semantic retrieval. Here we show that LIPC participates in the controlled retrieval of nonsemantic representations as well as semantic representations. Results also demonstrate that LIPC coactivates with dissociable posterior regions depending on the information retrieved: activating with left temporal cortex during the controlled retrieval of semantics and with left posterior frontal and parietal cortex during the controlled retrieval of phonology. Correlation of performance to LIPC activation suggests a processing role associated with mapping relatively ambiguous stimulus-to-representation relationships during both semantic and phonological tasks. These findings suggest that LIPC participates in controlled processing across multiple information domains collaborating with dissociable posterior regions depending upon the kind of information retrieved.

Adult↗

PubMed2001

Enhanced semantic priming in thought-disordered schizophrenic patients using a word pronunciation task.

Previous research on semantic priming in schizophrenia has produced contradictory findings. For the present study, it was intended to resolve some of the ambiguities in the literature. Using a semantic priming task with word pronunciation, evidence is provided that thought-disordered schizophrenic (TD) patients exhibit significantly increased semantic priming as compared to healthy and psychiatric controls. Results suggest that enhanced semantic priming is not confined to tasks that require lexical decision. Moreover, results indicate that TD schizophrenic patients suffer from a decay of hierarchical thinking, i.e. TD schizophrenics reveal a tendency to process the less meaningful rather than the dominant aspects of external information. Priming effects for the inferior meaning of homograph words (for example, 'dance' is an inferior, and 'game' is a superior associate of the word 'ball') were significantly greater compared to healthy controls and non-TD schizophrenics. Results were not moderated by sociodemographic background variables, psychomotor slowing and psychopathological symptoms other than thought disorder.

Adult↗

PubMed2003

Scaling and clustering in the study of semantic disruptions in patients with schizophrenia: a re-evaluation.

Some recent studies of semantics in schizophrenia have employed multidimensional scaling and clustering techniques to analyse verbal fluency and triadic comparison data. The conclusions have been: (i) patients generate fewer words in fluency tasks and display more variable similarity groupings of words in triadic tasks, and (ii) this is due to deficits in semantics. We analysed data from both tasks. On the verbal fluency task, patients produced significantly fewer responses than controls. The results also showed little patient-specific inter-individual consistency. Similarly, for triadic comparison data, we did not find much patient-specific inter-individual consistency. When correlating patients' results at different measurement times with means of controls, the data of individual patients (at either of the two measurement times) were not predicted better from their data at the other measurement time than from controls. This latter finding suggests little patient-specific intra-individual consistency and, thus, pleads against idiosyncratic semantic deficits. Our findings do not refute the hypothesis that schizophrenia is associated with semantic disruptions. However, our results demonstrate that because of severe statistical restrictions and requirements associated with some scaling and clustering techniques, these methods may not be as useful in this enterprise as previously thought.

Cluster Analysis↗

PubMed2000

Semantic priming by pictures and words in the cerebral hemispheres.

In order to determine whether pictures would act as more effective semantic primes than words in the right cerebral hemisphere, automatic semantic activation in intact hemispheres was studied with primed GO-NOGO lexical decision tasks by presenting word-word and picture-word pairs to the left visual field (right hemisphere) or to the right visual field (left hemisphere). Response times in Experiment 1 showed that categorically related targets (e.g., TABLE-BED) were primed only in the right visual field after both word and picture primes. Experiment 2 found that picture primes activated the representations of the corresponding written names in both visual fields. These observations suggest that the range of automatic semantic activation is larger in the left than in the right hemisphere. The results implicate that semantic categories may be organized in a different fashion in the left than the right hemisphere.

Adult↗

PubMed2002

Event-related potentials during discourse-level semantic integration of complex pictures.

This study examined event-related potentials (ERPs) elicited in response to semantic processing of non-verbal stories. ERPs were recorded from 29 scalp electrodes on 16 participants while they viewed series of complex gray-scale pictures, each of which relayed a simple story. The final picture of each story was either congruous or incongruous with the preceding context. Participants made delayed meaningfulness judgments for each story. Averaged ERPs time-locked to the onset of the final picture were more negative for incongruous than congruous pictures. Two distinct components were sensitive to congruency. The first component peaked at approximately 325 ms (N300) and was distributed over central and frontal sites. The second component peaked at approximately 500 ms and also had a centro-frontal maximum but was more widespread than the earlier component (anterior N400). The distinct scalp topographies of these two negativities provide strong evidence that the N300 and N400 are separate and distinguishable components. Furthermore, the presence of the N300 in this exclusively pictorial task suggests that the N300 is specific to the semantic processing of non-verbal stimuli and is not due to linguistic mediation. This study also revealed that the N400 can be modulated by discourse-level coherence manipulations with pictures. Finally, the different patterns of ERP effects observed during the semantic processing of verbal and non-verbal information suggest that non-identical neuronal sources, and thus non-identical representational systems, are accessed by these different types of materials. These findings strongly support at least partial modularity of semantic representations and processing mechanisms in the human brain.

Adult↗

PubMed2003

Short-term semantic retention during on-line sentence comprehension. Brain potential evidence from filler-gap constructions.

In filler-gap sentences, a phrase ('filler') is separated by intervening words from a subsequent phrase ('gap') with which it is integrated. The filler-gap interval provides a useful model for the study of short-term retention processes during sentence comprehension. Kluender and Kutas [J. Cogn. Neurosci. 5 (1993) 29] used event-related brain potentials (ERPs) to show that a filler phrase places a demand on short-term retention processes in the filler-gap interval, but left the processing level at which this demand arises unspecified. Here we use ERPs to address the issue of whether the filler places a demand on the semantic component of short-term retention processes in the filler-gap interval. Participants read filler-gap sentences, which began with a filler phrase and, in the filler-gap interval, contained a subject and object that were either semantically related or unrelated. There was also a control condition in which the filler phrase was absent (i.e. less memory demand). The main result was that during the filler-gap interval, bilateral posterior electrodes displayed a larger positivity for unrelated than related words. Moreover, during the same interval, posterior electrodes displayed a larger positivity for filler-gap sentences than for control sentences. In the control condition (non-filler gap sentences), manipulation of semantic relatedness did not produce differences in ERP activity. Our results suggest that a filler phrase places a demand on the semantic component of verbal working memory during on-line sentence comprehension.

Adult↗

PubMed2003

An ERP study of continuous speech processing. I. Segmentation, semantics, and syntax in native speakers.

Speech segmentation, breaking continuous streams of sound into units that can be recognized, is a necessary step in auditory language processing. To date, most studies of speech segmentation have been limited to behavioral measures that may not index online segmentation as it occurs when listening to natural speech. In the present study, we measured event-related potentials (ERPs) evoked by word-initial and word-medial syllables equated for loudness, length, and phonemic content. This comparison provided an online measure of natural speech segmentation. Word-initial sounds elicited a larger early sensory component (N100). In addition, we measured the effects of semantic and syntactic information on speech segmentation by comparing ERPs to word-initial and word-medial syllables in sentences with varying amounts of semantic and syntactic content. The results indicated that neither semantic nor syntactic information is necessary for the word-onset segmentation effect to be observed. We also identified additional ERP components that index more general semantic and syntactic aspects of natural speech processing.

Adult↗

PubMed2003

Does phonological encoding in speech production always follow the retrieval of semantic knowledge? Electrophysiological evidence for parallel processing.

In this article a new approach to the distinction between serial/contingent and parallel/independent processing in the human cognitive system is applied to semantic knowledge retrieval and phonological encoding of the word form in picture naming. In two-choice go/nogo tasks pictures of objects were manually classified on the basis of semantic and phonological information. An additional manipulation of the duration of the faster and presumably mediating process (semantic retrieval) allowed to derive differential predictions from the two alternative models. These predictions were tested with two event-related brain potentials (ERPs), the lateralized readiness potential (LRP) and the N200. The findings indicate that phonological encoding can proceed in parallel to the retrieval of semantic features. A suggestion is made how to accommodate these findings with models of speech production.

Adult↗

PubMed2003

Differences between noun and verb processing in a minimal phrase context: a semantic priming study using event-related brain potentials.

The aim of the present study was to enforce the priming of either nouns or verbs in order to evoke word-category-specific N400 effects. In two experiments two primes which were either a verb-noun or a noun-noun pair were followed by a semantically related or unrelated target which was a noun or verb, respectively. This target always completed the word sequence to a minimal phrase comprising verb, subject, and object (VNN or NNV triplets). In experiment I subjects judged the semantic relatedness of the target to the two primes, in experiment II subjects first generated an appropriate target of the required word category and then judged the semantic relatedness between self-generated word and target. ERPs were recorded from 124 scalp electrodes. In both experiments verbs and nouns as such evoked reliably distinct ERP topographies between 300 and 800 ms. With verbs in relation to nouns the amplitudes were most often found to be more positive over central to frontal or parietal areas and more negative over occipital and temporo-parietal areas. In contrast, N400 effects proved as topographically invariant for noun and verb targets in both experiments. The results suggest that access to noun and verb representations involves topographically distinct cell assemblies while the N400 effect seems to reflect semantic evaluation and integration processes which are more abstract and independent from a particular word category.

Adult↗

PubMed2003

Medial temporal lobe activation during semantic language processing: fMRI findings in healthy left- and right-handers.

Medial temporal lobe (MTL) areas are well known to serve episodic memory functions; their contribution to semantic memory has been occasionally noticed but not studied in detail. In the present fMRI study, 35 right-handed and 35 left-handed healthy subjects performed a semantic decision paradigm during which subjects heard spoken concrete nouns designating objects and had to decide on whether these objects were available in the supermarket and cost lest then a certain amount of money. The control paradigm consisted of sequences of low and high tones where subjects had to decide whether a sequence contained two high tones. The resulting contrast activation of semantic decision versus tone decision involved neocortical temporal, parietal, and prefrontal areas. Additional significant, bilateral activations in the MTL, the hippocampal formation, and adjacent areas were found. The exact incidence and location of activation was studied in a single-subject analysis for all 70 subjects. At the chosen threshold of P<0.001, 94% of subjects showed activations in the MTL and inferior temporal lobe (ITL). Activations were found along the longitudinal axis of the MTL, including the hippocampal formation and the parahippocampal gyrus. In the ITL, parts of the fusiform and lingual gyri were activated. Activations were similar in right- and left-handers. We conclude from this study that the MTL and parts of the ITL can be added to the areas activated by semantic verbal memory processing.

Acoustic Stimulation↗

PubMed1999

Episodic memory: new insights from the study of semantic dementia.

The study of patients with semantic dementia, the temporal variant of frontotemporal dementia, has provided new insights into the interaction between episodic and semantic memory, and the different roles played by various structures in the temporal lobe. Recent findings indicate that the syndrome of semantic dementia can inform us about the organisation of long-term memory and the relationship between semantic memory and other cognitive systems.

Dementia↗

PubMed2003

Functional analysis of the deficit in semantic context processes in schizophrenic patients: an event-related potentials study.

AIM: Schizophrenic patients exhibit a deficit in the semantic context processing strategies which might be responsible for the language and communication disorders that are characteristic of this condition. The aim of our study was to identify the nature of the contextualization processes which are lacking in schizophrenic patients, by distinguishing between processes for the generation of expectations and processes of semantic integration. PATIENTS AND METHOD: Thirteen schizophrenic patients and 12 healthy controls performed two tasks: (a) a lexical decision task (LDT) with a highly structured sentence context and whose experimental characteristics made it possible to call strongly on predictive strategies, and (b) a LDT with classic semantic priming (the context being reduced to a single word). In this latter task, the small number of related words did not prompt the generation of expectations but instead called on the postlexical integration process. The event-related potentials (ERP) were recorded during the administration of the task. RESULTS AND CONCLUSION: In the sentence task, we observed a modulation in the N400 amplitude due to the presence of expectations both in the schizophrenic and control participants: predictable words evoked a small N400 amplitude compared to the non-predictable words. In contrast, in the simple (priming) task, the semantic link evoked an N400 amplitude modulation in the control group exclusively. Our results indicate that schizophrenics could be able to use context to activate expectations for the most highly predictable item, and that their deficit appears when the processing strategy is based on the integration of the context stored in working memory.

Adult↗