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PubMed1999

Word and picture matching: a PET study of semantic category effects.

We report two positron emission tomography (PET) studies of cerebral activation during picture and word matching tasks, in which we compared directly the processing of stimuli belonging to different semantic categories (animate and inanimate) in the visual (pictures) and verbal (words) modality. In the first experiment, brain activation was measured in eleven healthy adults during a same/different matching task for textures, meaningless shapes and pictures of animals and artefacts (tools). Activations for meaningless shapes when compared to visual texture discrimination were localized in the left occipital and inferior temporal cortex. Animal picture identification, either in the comparison with meaningless shapes and in the direct comparison with non-living pictures, involved primarily activation of occipital regions, namely the lingual gyrus bilaterally and the left fusiform gyrus. For artefact picture identification, in the same comparison with meaningless shape-baseline and in the direct comparison with living pictures, all activations were left hemispheric, through the dorsolateral frontal (Ba 44/6 and 45) and temporal (Ba 21, 20) cortex. In the second experiment, brain activation was measured in eight healthy adults during a same/different matching task for visually presented words referring to animals and manipulable objects (tools); the baseline was a pseudoword discrimination task. When compared with the tool condition, the animal condition activated posterior left hemispheric areas, namely the fusiform (Ba 37) and the inferior occipital gyrus (Ba 18). The right superior parietal lobule (Ba 7) and the left thalamus were also activated. The reverse comparison (tools vs animals) showed left hemispheric activations in the middle temporal gyrus (Ba 21) and precuneus (Ba 7), as well as bilateral activation in the occipital regions. These results are compatible with different brain networks subserving the identification of living and non-living entities; in particular, they indicate a crucial role of the left fusiform gyrus in the processing of animate entities and of the left middle temporal gyrus for tools, both from words and pictures. The activation of other areas, such as the dorsolateral frontal cortex, appears to be specific for the semantic access of tools only from pictures.

Adult↗

PubMed1999

A neural basis for category and modality specificity of semantic knowledge.

Prevalent theories hold that semantic memory is organized by sensorimotor modality (e.g., visual knowledge, motor knowledge). While some neuroimaging studies support this idea, it cannot account for the category specific (e.g., living things) knowledge impairments seen in some brain damaged patients that cut across modalities. In this article we test an alternative model of how damage to interactive, modality-specific neural regions might give rise to these categorical impairments. Functional MRI was used to examine a cortical area with a known modality-specific function during the retrieval of visual and non-visual knowledge about living and non-living things. The specific predictions of our model regarding the signal observed in this area were confirmed, supporting the notion that semantic memory is functionally segregated into anatomically discrete, but highly interactive, modality-specific regions.

Adult↗

PubMed2006

Emotional and semantic networks in visual word processing: insights from ERP studies.

The event-related brain potential (ERP) literature concerning the impact of emotional content on visual word processing is reviewed and related to general knowledge on semantics in word processing: emotional connotation can enhance cortical responses at all stages of visual word processing following the assembly of visual word form (up to 200 ms), such as semantic access (around 200 ms), allocation of attentional resources (around 300 ms), contextual analysis (around 400 ms), and sustained processing and memory encoding (around 500 ms). Even earlier effects have occasionally been reported with subliminal or perceptual threshold presentation, particularly in clinical populations. Here, the underlying mechanisms are likely to diverge from the ones operational in standard natural reading. The variability in timing of the effects can be accounted for by dynamically changing lexical representations that can be activated as required by the subjects' motivational state, the task at hand, and additional contextual factors. Throughout, subcortical structures such as the amygdala are likely to contribute these enhancements. Further research will establish whether or when emotional arousal, valence, or additional emotional properties drive the observed effects and how experimental factors interact with these. Meticulous control of other word properties known to affect ERPs in visual word processing, such as word class, length, frequency, and concreteness and the use of more standardized EEG procedures is vital. Mapping the interplay between cortical and subcortical mechanisms that give rise to amplified cortical responses to emotional words will be of highest priority for future research.

Brain↗

PubMed2002

Predicability (ease of predication) as semantic substrate of imageability in reading and retrieval.

It was proposed by Jones (1985) that the apparent influence of a word's imageability upon the probability of the word being read correctly by a deep dyslexic person could be understood in terms of an underlying semantic variable, ease of predication (also termed predicability). In a recent critique, de Mornay Davies and Funnell (2000) claim to have identified a number of problems with the ease of predication proposal. It is shown here, however, that it is the critique itself which is fundamentally flawed. In contrast, the predicability approach continues to identify correctly the semantic substrate of apparent effects of imageability upon reading and memory retrieval.

Anomia↗

PubMed2002

The lateralized stroop: a meta-analysis and its implications for models of semantic processing.

The prevailing theory in the literature concerning the lateralization of Stroop effects involves a speed of processing account (see ). Because the left hemisphere (LH) demonstrates an overall advantage relative to the right hemisphere (RH) on most verbal tasks, interference effects are hypothesized to be greater in the LH than in the RH. Inspection of the data, however, reveals that many studies find no difference in magnitude of Stroop interference between the hemispheres. Given findings within the lateralized semantic priming literature, this is not surprising. A meta-analysis on a subset of lateralized Stroop experiments was conducted to determine whether or not the LH produces significantly more interference than the RH in this paradigm. Based on a number of exclusionary criteria, a total of 19 different studies were included, representing a potential 26 effect size estimates of differential interference. The effect size representing interference using congruent conditions as the baseline (d+=.06) reveals that there is no significant difference between the hemispheres in magnitude of the Stroop interference effect. The LH interference effect was d+=.73, which is significant. Likewise, the RH interference effect, d+=.67, was significant. In summary, while there was no significant difference between the hemispheres, each hemisphere, when examined independently, did exhibit significant within hemisphere interference effects. These findings are presented in light of the lateralized semantic priming literature.

Brain↗

PubMed2003

Lateralization effects during semantic and rhyme judgement tasks in deaf and hearing subjects.

A visual hemifield experiment investigated hemispheric specialization among hearing children and adults and prelingually, profoundly deaf youngsters who were exposed intensively to Cued Speech (CS). Of interest was whether deaf CS users, who undergo a development of phonology and grammar of the spoken language similar to that of hearing youngsters, would display similar laterality patterns in the processing of written language. Semantic, rhyme, and visual judgement tasks were used. In the visual task no VF advantage was observed. A RVF (left hemisphere) advantage was obtained for both the deaf and the hearing subjects for the semantic task, supporting Neville's claim that the acquisition of competence in the grammar of language is critical in establishing the specialization of the left hemisphere for language. For the rhyme task, however, a RVF advantage was obtained for the hearing subjects, but not for the deaf ones, suggesting that different neural resources are recruited by deaf and hearing subjects. Hearing the sounds of language may be necessary to develop left lateralised processing of rhymes.

Adolescent↗

PubMed2003

The unification of mind: Integration of hemispheric semantic processing.

Seventy-six participants performed a visual half-field lexical decision task at two different stimulus onset asynchronies (50 or 750 ms). Word targets were primed either by a highly associated word (e.g., CLEAN-DIRTY), a weakly associated word (e.g., CLEAN-TIDY), or an unrelated word (e.g., CLEAN-FAMILY) projected to either the same or opposite visual field (VF) as the target. In the short SOA, RVF-left hemisphere primes resulted in high associate priming regardless of target location (ipsilateral or contralateral to the prime) whereas LVF-right hemisphere primes produced both high and low associate priming across both target location conditions. In the long SOA condition, contralateral priming patterns converged, demonstrating only high associate priming in both VF locations. The results of this study demonstrate the critical role of interhemispheric transfer in semantic processing and indicate a need to elaborate current models of semantic processing.

Adolescent↗

PubMed2003

The breakdown of semantic knowledge: insights from a statistical model of meaning representation.

Investigations of patients with semantic category-specific deficits have revealed a wide range of performance and variability in categories that are impaired or spared; this variability presents a challenge to accounts of category specificity. Accounts based only on impairment to semantic features of a particular type (e.g., visual), as well as accounts based only on featural properties (e.g., feature intercorrelations), are insufficient to explain the variability of patients' performance. A first goal of the paper is to discuss how a hybrid account incorporating both a level of organization according to feature types (a level of nonlinguistic conceptual representations) and a level of organization dictated by featural properties may provide a more comprehensive account of the cases reported in the literature. The second and most novel goal of the study reported here is to derive from our hybrid account a series of novel predictions concerning the representation and impairment of a different domain of knowledge: knowledge of actions and events, a domain of knowledge that has received remarkably little attention to date.

Cognition↗

PubMed2004

Hemispheric asymmetries in the split-fovea model of semantic processing.

We report a series of neural network models of semantic processing of single English words in the left and the right hemispheres of the brain. We implement the foveal splitting of the visual field and assess the influence of this splitting on a mapping from orthography to semantic representations in single word reading. The models were trained on English four-letter words, presented according to their frequency in all positions encountered during normal reading. The architecture of the model interacted with the training set to produce processing asymmetries comparable to those found in behavioral studies. First, the cueing effects of dominant and subordinate meanings of ambiguous words were different for words presented to the left or to the right of the input layer. Second, priming effects of groups of related words were stronger in the left input than the right input of the model. These effects were caused by coarser-coding in the right half compared with the left half of the model, an emergent effect of the split model interacting with informational asymmetries in the left and right parts of words in the lexicon of English. Some or all of the behavioral data for reading single words in English may have a similar origin.

Brain↗

PubMedDate not supplied

Investigating the interplay between semantic and phonological distractor effects in picture naming.

In this paper, we investigate the interplay between phonological facilitation and semantic interference effects in picture naming. We use a double distractor variant of the classic picture-word interference paradigm to investigate whether the reported interaction between these effects is dependent on the two types of related information being presented by the same distractor word or not. While prior studies using single mixed distractors such as pigeon for the target PIG have reported an interaction between phonological facilitation and semantic interference, we find additivity when the two types of related information come from two different distractor words. Possible implications of this result for how activation is transmitted within the speech production system are discussed.

Humans↗

PubMed2004

Neural responses to morphological, syntactic, and semantic properties of single words: an fMRI study.

Dissociations in the recognition of specific classes of words have been documented in brain-injured populations. These include deficits in the recognition and production of morphologically complex words as well as impairments specific to particular syntactic classes such as verbs. However, functional imaging evidence for distinctions among the neural systems underlying these dissociations has been inconclusive. We explored the neural systems involved in processing different word classes in a functional Magnetic Resonance Imaging study, contrasting four groups of words co-varying morphological complexity (simple, monomorphemic words vs complex derived or inflected words) and syntactic class (verbs vs nouns/adjectives). Subtraction of word from letter string processing showed activation in left frontal and temporal lobe regions consistent with prior studies of visual word processing. No differences were observed for morphologically complex and simple words, despite adequate power to detect stimulus specific effects. A region of posterior left middle temporal gyrus showed significantly increased activation for verbs. Post hoc analyses showed that this elevated activation could also be related to semantic properties of the stimulus items (verbs have stronger action associations than nouns, and action association is correlated with activation). Results suggest that semantic as well as syntactic factors should be considered when assessing the neural systems involved in single word comprehension.

Adolescent↗

PubMed1999

Spatio-temporal analysis of electric brain activity during semantic and phonological word processing.

There is an ongoing debate in cognitive neuroscience about the time course and the functional independence of the different processes involved in encoding written language material. New data indicate very fast and highly parallel language analysis networks in the brain. Here we demonstrate a methodological approach to study the temporal dynamics of this network by searching for time periods where different task demands emphasize different aspects of the network. Multi-channel event related potentials (ERPs) were recorded during a semantic and a phonological reading task from 14 healthy subjects. Signals were analyzed exclusively on the basis of the spatial configuration of the electric potential distributions (ERP maps), since differences in these spatial patterns directly reflect changes in the configuration of the active sources in the brain. This analysis did not reveal any differences of the evoked brain electric fields between the two tasks up to 280 ms post-stimulus. The ERP maps then differed for a brief period between 280 and 380 ms, before they were similar again. The analysis of the maps using a global linear localization procedure revealed a network of areas, active in both tasks, that mainly involved the left postero-temporal and left antero-temporal regions. The left posterior activation was found already around 100 ms post-stimulus, indicating that language-specific functions appear early in time. We therefore conclude that phonological and semantic processing are essentially performed in both tasks and that only late decision-related processes influence the relative strength of activity of the different modules in the complex language network.

Adult↗

PubMed2003

Midazolam amnesia and retrieval from semantic memory: Developing methods to test theories of implicit memory.

Studies of organic anterograde amnesia have been central to the development of theories of implicit memory. Pharmacological amnesia provides an additional method for exploring implicit memory, allowing for the experimental manipulation of amnesia and the testing of more participants. A significant concern with pharmacological amnesia is whether its cognitive effects are specific to explicit memory. The current research examines the effects of the benzodiazepine, midazolam, on retrieval from semantic memory and encoding in explicit memory. We focus on midazolam because it holds significant advantages over other benzodiazepines in inducing pharmacological amnesia and prior research suggests it may be useful for testing theories of implicit memory. Our results demonstrate that midazolam does not impair accuracy of retrieval from semantic categories, even when it produces anterograde amnesia for retrieved category items on a later recall test. These results suggest ways midazolam can be used to help test theories of implicit memory.

Adult↗

PubMed2000

Effects of attention and semantic relation on event-related potentials in a picture-word naming task.

The interactive effects of attention and semantic relation on event-related potential (ERP) waveforms were examined during a naming task in which the physical stimulus array was the same across conditions. Superimposed picture-word pairs were presented in which the meaning of the words and pictures was congruent, semantically associated, or incongruent. In separate conditions, participants named words or pictures while ignoring the other stimulus. When words were attended, the superimposed pictures modulated the amplitude of P240 waves at posterior sites compared with when words were presented individually, but had no effect on N450 waves. In contrast, when pictures were attended to, the superimposed incongruent words elicited larger amplitude N450 waves at anterior sites than did congruent words or individually presented pictures. These effects affirm the independent processing of words and pictures during attention and are consistent with automatic and controlled processing of words and pictures, respectively. They also illustrate the endogenous nature of these late ERP waves.

Adult↗

PubMed2000

The influence of semantic priming on event-related potentials to painful laser-heat stimuli in humans.

In this study we investigated the effects of different semantic primes on the processing of painful stimuli. For prime stimuli, descriptors of three categories were used: somatosensory pain-related, affective pain-related, and neutral adjectives. While subjects (n=10) processed these primes, a painful laser-heat stimulus was applied. Laser-evoked potentials (LEPs) were recorded and pain intensity ratings were obtained after each single laser stimulus. Painful stimuli applied while subjects processed pain-related primes (affective and somatosensory adjectives) resulted in larger LEP amplitudes at 370 ms post laser stimulus compared to amplitudes of laser-evoked activities while subjects processed neutral primes (F((2,18))=3.90, P=0.05). It is suggested that pain-related semantic primes might preactivate neural networks subserving pain memory and pain processing. The processing of pain-related primes seems to preactivate cortical cell-assemblies involved in the processing of the succeeding painful laser stimuli.

Acoustic Stimulation↗

PubMed1999

Semantic or lexico-syntactic factors: what determines word-class specific activity in the human brain?

Words from different classes have been found to activate different brain areas. However, it is unclear whether grammatical word properties, for example their being part of different lexical categories (e.g. nouns vs. verbs) or semantic features of the words (e.g. that they refer to visually perceived entities or to actions) are relevant for eliciting differential brain responses. We tested this by comparing brain potentials elicited by nouns and verbs that varied in their action and visual associations. Naturally spoken word stimuli were from three categories: (1) nouns with strong visual associations; (2) action verbs with strong associations of actions, and (3) nouns with strong action associations. Word-category specific differences became apparent around 500 ms after stimulus onset, approximately 150-200 ms after the average recognition point of the words involved. Brain responses to visual nouns and action verbs differed at central and occipital recording sites. A very similar topographical difference emerged from the comparison of visual vs. action nouns, whereas no significant difference was found between action-related nouns and verbs. These results indicate that grammatical differences alone, e.g. between two lexical classes such as action verbs and action-related nouns, are not sufficient for eliciting differential brain responses. In contrast, semantic differences between items from the same lexical category can be sufficient for changing the topography of cortical processes induced by word stimuli. This is support for associative theories of word processing.

Adult↗

PubMed2002

Exploring self-image during hot flushes using a semantic differential scale: associations between poor self-image, depression, flush frequency and flush distress.

OBJECTIVES: This study developed a semantic differential scale for assessing self-image during hot flushes, based on a previously published scale (Nursing Res. 35 (1986) 81). The objectives were to explore the sensitivity and validity of this scale, and to examine whether poor self-image during hot flushes is linked to flush distress, perceived control, flush frequency, flush chronicity, self-esteem and depression. METHOD: Two community samples of women with current experience of hot flushes completed a postal questionnaire. RESULTS: The semantic differential scale was sensitive to individual differences in self-image, and was validated through its association with measured self-esteem using a standardised scale. Defining the self in negative ways during flushes was highly predictive of flush distress. Poor self-image was also closely associated with depression. Correlations with perceived control, and flush frequency were weaker and did not reach significance in the second, smaller sample. CONCLUSION: The study extends previous findings that women low in self-esteem have more difficulty coping with menopausal changes, by showing that negative self-appraisal during flushes (e.g. defining self as unattractive or dirty) are highly demoralising and associated with distress. The findings suggest that cognitive behavioural strategies of challenging and re-interpreting thoughts about self could be helpful in moderating the discomfort and stressfulness of hot flushes for women not taking HRT. However, the findings are based on relatively small, volunteer samples and require further replication.

Adaptation, Psychological↗

PubMed2001

Activation of right fronto-temporal cortex characterizes the 'living' category in semantic processing.

It is a vital ability for humans to distinguish between living and non-living objects. Whether the semantic features of these two classes of objects are represented in distinct brain areas, is unknown. In our study, words belonging to the categories 'living' and 'non-living' were presented visually to twelve right-handed volunteers, while brain activation was measured with event-related fMRI. Subjects had to judge whether the item belonged to one of these categories. Common areas of activation (P<0.05, corrected) during processing of both categories include the inferior occipital gyri bilaterally (BA 17/18), left inferior frontal gyrus (BA 44/45) and left inferior parietal lobe (BA 40). During processing of 'living' minus 'non-living' items, signal changes (P<0.05, corrected) were present in the the right inferior frontal (BA 47), middle temporal (BA 21) and fusiform gyrus (BA 19). Our results are in line with findings from patients with a deficit in semantic processing of living things, who specifically suffer from right hemispheric lesions.

Adult↗