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Segregating semantic and syntactic aspects of processing in the human brain: an fMRI investigation of different word types.

The processing of single words that varied in their semantic (concrete/abstract word) and syntactic (content/function word) status was investigated under different task demands (semantic/ syntactic task) in an event-related functional magnetic resonance imaging experiment. Task demands to a large degree determined which subparts of the neuronal network supporting word processing were activated. Semantic task demands selectively activated the left pars triangularis of the inferior frontal gyrus (BA 45) and the posterior part of the left middle/superior temporal gyrus (BA 21/22/37). In contrast, syntactic processing requirements led to an increased activation in the inferior tip of the left frontal operculum (BA 44) and the cortex lining the junction of the inferior frontal and inferior precentral sulcus (BA 44/6). Moreover, for these latter areas a word class by concreteness interaction was observed when a syntactic judgement was required. This interaction can be interpreted as a prototypicality effect: non-prototypical members of a word class, i.e. concrete function words and abstract content words, showed a larger activation than prototypical members, i.e. abstract function words and concrete content words. The combined data suggest that the activation pattern underlying word processing is predicted neither by syntactic class nor semantic concreteness but, rather, by task demands focusing either on semantic or syntactic aspects. Thus, our findings that semantic and syntactic aspects of processing are both functionally distinct and involve different subparts of the neuronal network underlying word processing support a domain-specific organization of the language system.

Adult↗

A brain perspective on language mechanisms: from discrete neuronal ensembles to serial order.

Language is constituted by discrete building blocks, sounds and words, which can be concatenated according to serial order principles. The neurobiological organization of these building blocks, in particular words, has been illuminated by recent metabolic and neurophysiological imaging studies. When humans process words of different kinds, various sets of cortical areas have been found to become active differentially. The old concept of two language centers processing all words alike must therefore be replaced by a model according to which words are organized as discrete distributed neuron ensembles that differ in their cortical topographies. The meaning of a word, more precisely, aspects of its reference, may be crucial for determining which set of cortical areas becomes involved in its processing. Whereas the serial order of sounds constituting a word may be established by serially aligned sets of neurons called synfire chains, different mechanisms are necessary for establishing word order in sentences. The serial order of words may be organized by higher-order neuronal sets, called sequence detectors here, which are being activated by sequential excitation of neuronal sets representing words. Sets of sequence detectors are proposed to process aspects of the syntactic information contained in a sentence. Other syntactic rules can be related to general features of the dynamics of cortical activation and deactivation. These postulates about the brain mechanisms of language, which are rooted in principles known from neuroanatomy and neurophysiology, may provide a framework for theory-driven neuroscientific research on language.

Brain↗

Developmental dyslexia: ERP correlates of anomalous phonological processing during spoken word recognition.

Ample evidence suggests that developmental dyslexia results from a phonological deficit that may not be reducible to a low-level auditory deficit. Yet, on-line phonological processing (in)capacities in dyslexics remain virtually unexplored, as studies have typically focused on either meta-phonological awareness tasks or, at the other extreme, basic perceptual tasks. The present study investigates event-related potential (ERP) correlates of implicit phonological processing during the recognition of spoken words in dyslexic and normally reading children (7-10 years). We examined general ERP morphology and alliteration priming effects on ERP measures in an auditory lexical decision task. Primes were words (Experiment 1) and non-words (Experiment 2). Alliteration priming effects suggested a distinct pattern of normal versus anomalous aspects of spoken word processing in dyslexic children. Whereas dyslexics showed deviant priming effects in earlier time windows encompassing the N1 and N2, later N400 priming effects were comparable to those of normal readers. The same pattern of results was also present in group comparisons of general ERP morphology. These findings suggest that dyslexics have selective processing anomalies at an earlier phonetic/phonological level, while processing at a later phonological/lexical level proceeds normally. In particular, our results indicate an anomalous contribution of phonological (word onset) information to the processing of spoken words, which may be related to time-course aspects of phonetic/phonological processing.

Acoustic Stimulation↗

Modulation of the N400 potential during auditory phonological/semantic interaction.

The processing of phonological and semantic word attributes has been commonly explored with electrophysiological methods using simple contexts where competition between features is eliminated. Conversely, the interaction between phonological and semantic attributes has not been systematically examined. We therefore recorded an event-related electrophysiological marker of word discordance, the N400, in response to sequences of auditory word pairs containing semantic incongruences, phonological discordances, or a mixture of the two. N400 enhancement to semantically unrelated words was systematically observed, whether the subjects heard the sequences passively (no instruction) or actively (semantic judgement task), and even in contexts where the task did not concern semantic attributes. In contrast, the N400 effect to phonologically unrelated (non-rhyming) words was exclusively obtained in the active situation (phonological judgment), while it disappeared in passive conditions and during semantic/phonological interference. This suggests that the detection of semantic incongruences is a more robust and automatized mechanism than that of phonological ones, and tends to occlude this latter when both features are in competition. Our data also provide new elements supporting the persistence of the semantic N400 during 'shallow' word processing tasks, i.e. tasks that discourage analysis of semantic aspects of the words.

Acoustic Stimulation↗

Neurophysiology of fluent and impaired reading: a magnetoencephalographic approach.

This article reviews a series of magnetoencephalographic (MEG) experiments aimed at identifying cortical areas and time windows relevant or even critical for fluent reading. The approach was to compare single-word processing in fluent and dyslexic readers. The activations which differed between the two groups were then studied in more detail to determine their functional roles. In fluent reading, overall visual feature processing occurs about 100 milliseconds (ms) after seeing a word, in the posteromedial extrastriate cortex bilaterally. This activation does not differentiate between letters and symbols. The first reading-specific signal is detected about 150 ms after word onset, when the left inferior occipitotemporal cortex responds preferentially to letter strings. After 200 ms, the left superior temporal cortex, in particular, is engaged in semantic processing of single words and their integration with connected text. While visual feature processing seems to be within normal limits in dyslexic subjects, reading is disrupted during the first 200 ms after seeing a word, at the letter-string specific stage. The subsequent activations are weak and delayed as compared with those in fluent readers. Also presented is a case of deep dyslexia, where the same tools were used to demonstrate that reading comprehension was still subserved by the left hemisphere despite severe damage.

Cerebral Cortex↗

Brain reflections of words and their meaning.

The neurobiological organization of meaningful language units, morphemes and words, has been illuminated by recent metabolic and neurophysiological imaging studies. When humans process words from different categories, sets of cortical areas become active differentially. The meaning of a word, more precisely aspects of its reference, may be crucial for determining which set of cortical areas is involved in its processing. Word-related neuron webs with specific cortical distributions might underlie the observed category-specific differences in brain activity. Neuroscientific principles can explain these differential topographies.

Journal Article↗

Differential sensitivity to words and shapes in ventral occipito-temporal cortex.

Efficient extraction of shape information is essential for proficient reading but the role of cortical mechanisms of shape analysis in word reading is not well understood. We studied cortical responses to written words while parametrically varying the amount of visual noise applied to the word stimuli. In only a few regions along the ventral surface, cortical responses increased with word visibility. We found consistently increasing responses in bilateral posterior occipito-temporal sulcus (pOTS), at an anatomical location that closely matches the "visual word form area". In other cortical regions, such as V1, responses remained constant regardless of the noise level. We performed 3 additional tests to assess the functional specialization of pOTS responses for written word processing. We asked whether pOTS responses are 1) left lateralized, 2) more sensitive to words than to line drawings or false fonts, and 3) invariant for visual hemifield of words but not other stimuli. We found that left and right pOTS response functions both had highest sensitivity for words, intermediate for line drawings, and lowest for false fonts. Visual hemifield invariance was similar for words and line drawings. These results suggest that left and right pOTS are both involved in shape processing, with enhanced efficiency for processing visual word forms.

Adult↗

Computerized literature reference system: use of an optical scanner and optical character recognition software.

A computerized reference system for radiology journal articles was developed by using an IBM-compatible personal computer with a hand-held optical scanner and optical character recognition software. This allows direct entry of scanned text from printed material into word processing or data-base files. Additionally, line diagrams and photographs of radiographs can be incorporated into these files. A text search and retrieval software program enables rapid searching for keywords in scanned documents. The hand scanner and software programs are commercially available, relatively inexpensive, and easily used. This permits construction of a personalized radiology literature file of readily accessible text and images requiring minimal typing or keystroke entry.

Electronic Data Processing↗

Brain responses to segmentally and tonally induced semantic violations in Cantonese.

The present event-related potential (ERP) study examined the role of tone and segmental information in Cantonese word processing. To this end, participants listened to sentences that were either semantically correct or contained a semantically incorrect word. Semantically incorrect words differed from the most expected sentence completion at the tone level, at the segmental level, or at both levels. All semantically incorrect words elicited an increased frontal negativity that was maximal 300 msec following word onset and an increased centroparietal positivity that was maximal 650 msec following word onset. There were differences between completely incongruous words and the other two violation conditions with respect to the latency and amplitude of the ERP effects. These differences may be due to differences in the onset of acoustic deviation of the presented from the expected word and different mechanisms involved in the processing of complete as compared to partial acoustic deviations. Most importantly, however, tonally and segmentally induced semantic violations were comparable. This suggests that listeners access tone and segmental information at a similar point in time and that both types of information play comparable roles during word processing in Cantonese.

Acoustic Stimulation↗

The low-frequency encoding disadvantage: Word frequency affects processing demands.

Low-frequency words produce more hits and fewer false alarms than high-frequency words in a recognition task. The low-frequency hit rate advantage has sometimes been attributed to processes that operate during the recognition test (e.g., L. M. Reder et al., 2000). When tasks other than recognition, such as recall, cued recall, or associative recognition, are used, the effects seem to contradict a low-frequency advantage in memory. Four experiments are presented to support the claim that in addition to the advantage of low-frequency words at retrieval, there is a low-frequency disadvantage during encoding. That is, low-frequency words require more processing resources to be encoded episodically than high-frequency words. Under encoding conditions in which processing resources are limited, low-frequency words show a larger decrement in recognition than high-frequency words. Also, studying items (pictures and words of varying frequencies) along with low-frequency words reduces performance for those stimuli.

Adolescent↗

Survey of ACCP members regarding use of computers and information processing.

A questionnaire was sent to a random sample of 480 members of the American College of Clinical Pharmacy to determine their opinions on various issues relating to computer technology and the future role of computers in information processing in pharmacy. Results from the 335 evaluable responses revealed nearly universal use of computers. Word processing was the most common application and IBM or compatible computers were the dominant machines. Respondents used a wide variety of generalized and specialized programs, especially electronic communication products. Computer technology is expected to have a major impact on routine aspects of pharmacy practice, although, respondents were split on its impact on more cognitively intensive functions.

Clinical Pharmacy Information Systems↗

Influence of imaging ability on word transformation.

In the present study, we examined whether individual differences in imaging ability affect visual word recognition. Poor and vivid imagers performed a naming task that involved nonreversed (e.g., JUMP) and reversed (e.g., PMUJ) words (Experiment 1). Poor and vivid imagers were also tested on a naming task that was controlled for verbal ability; all the words were reversed and presentation time was varied (Experiment 2). In both experiments, imaging ability interacted with task difficulty, suggesting that individual differences in imaging ability affect visual word recognition. Specifically, the present data suggest that poor imagers may be less efficient than vivid imagers at processing words analytically. The data are interpreted within a limited-capacity, hybrid, word recognition model, in which words can be processed as either word-level or letter-level codes.

Adult↗

Pitfalls in the clustering of neuroimage data and improvements by global optimization strategies.

In this paper, we examined three vector quantization (VQ) methods used for the unsupervised classification (clustering) of functional magnetic resonance imaging (fMRI) data. Classification means that each brain volume element (voxel), according to a given scanning raster, was assigned to one group of voxels based on similarity of the fMRI signal patterns. It was investigated how the VQ methods can isolate a cluster that describes the region involved in a particular brain function. As an example, word processing was stimulated by a word comparison task. VQ analysis methodology was verified using simulated fMRI response patterns. It was demonstrated in detail that VQ based on global rather than local optimization of the objective function yielded a higher performance. Performance was measured in statistically relevant series of VQ attempts using several indices for goodness, reliability and efficiency of VQ solutions. Furthermore, it was shown that a poor local optimization caused either an underestimation or an overestimation of the stimulus-induced brain activation. However, this was not observed if the cluster analysis was based upon a global optimization strategy.

Adult↗

[The computer in radiology. findings obtained by the text rail].

As a dedicated solution for professional classification, the COMRAD (COMputer in RADiology) system makes available a "dialog system" that enables the fully integrated processing of operational layouts or word processing and administration of medical practice. The dialog system is based on data files which enable direct access to all stored data as well as the storage of new data, thus avoiding a multiple input and storage. The operational layout of text processing which is to be introduced by this paper, permits radiological findings to be prepared in a flow text, strictly observing a division of the analysis into a descriptive and a evaluative report. The synthesis of the findings is reached through a dialed description of a pathological condition, which is automatically supplemented for assessment by the pertinent evaluation text including its variables. In contrary of assembling text modules the texts of all not directly dialed findings without pathological changes are automatically incorporated both into the description and into the assessment. The variables may be standard attributes, free attributes and pairing attributes.

Computers↗