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

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

Brain activity during syntactic and semantic processing--a magnetoencephalographic study

Drawings of objects were presented in series of 54 each to 14 German speaking subjects with the tasks to indicate by button presses a) whether the grammatical gender of an object name was masculine ("der") or feminine ("die") and b) whether the depicted object was man-made or nature-made. The magnetoencephalogram (MEG) was recorded with a whole-head neuromagnetometer and task-specific patterns of brain activity were determined in the source space (Minimum Norm Estimates, MNE). A left-temporal focus of activity 150-275 ms after stimulus onset in the gender decision compared to the semantic classification task was discussed as indicating the retrieval of syntactic information, while a more expanded left hemispheric activity in the gender relative to the semantic task 300-625 ms after stimulus onset was discussed as indicating phonological encoding. A predominance of activity in the semantic task was observed over right fronto-central region 150-225 ms after stimulus-onset, suggesting that semantic and syntactic processes are prominent in this stage of lexical selection.     

An ERP study on the time course of phonological and semantic activation in Chinese word recognition

With the event-related potential (ERP) technique, we examined the time course of phonological and semantic activation in Chinese word recognition. Participants did a semantic judgment task and a homophone judgment task over the same set of word pairs. Each pair was of either high or low word frequency and the two words were either unrelated or related semantically or phonologically, i.e., being homophones. For high-frequency words, both the semantically related pairs in the homophone task and the homophonic pairs in the semantic task elicited ERP responses different from the unrelated control pairs in the N400 component but not any component earlier, suggesting a similar time course for semantic and phonological activation. For low-frequency words, the semantically related pairs in the homophone task were associated with a similar modulation of N400. However, compared to the unrelated controls, the homophonic pairs in the semantic task elicited a larger P200, a component implicated in phonological processing in the literature, and thus demonstrated a phonological activation earlier than semantic activation. The results showed that word frequency affects the time course of semantic and phonological activation suggesting that phonology is not invariably activated before semantics in Chinese word recognition.     

Building a comprehensive syntactic and semantic corpus of Chinese clinical texts

ObjectiveTo build a comprehensive corpus covering syntactic and semantic annotations of Chinese clinical texts with corresponding annotation guidelines and methods as well as to develop tools trained on the annotated corpus, which supplies baselines for research on Chinese texts in the clinical domain.Materials and methodsAn iterative annotation method was proposed to train annotators and to develop annotation guidelines. Then, by using annotation quality assurance measures, a comprehensive corpus was built, containing annotations of part-of-speech (POS) tags, syntactic tags, entities, assertions, and relations. Inter-annotator agreement (IAA) was calculated to evaluate the annotation quality and a Chinese clinical text processing and information extraction system (CCTPIES) was developed based on our annotated corpus.ResultsThe syntactic corpus consists of 138 Chinese clinical documents with 47,426 tokens and 2612 full parsing trees, while the semantic corpus includes 992 documents that annotated 39,511 entities with their assertions and 7693 relations. IAA evaluation shows that this comprehensive corpus is of good quality, and the system modules are effective.DiscussionThe annotated corpus makes a considerable contribution to natural language processing (NLP) research into Chinese texts in the clinical domain. However, this corpus has a number of limitations. Some additional types of clinical text should be introduced to improve corpus coverage and active learning methods should be utilized to promote annotation efficiency.ConclusionsIn this study, several annotation guidelines and an annotation method for Chinese clinical texts were proposed, and a comprehensive corpus with its NLP modules were constructed, providing a foundation for further study of applying NLP techniques to Chinese texts in the clinical domain.     

An influence of flanker in a category verification task on semantic satiation effect

This study examined semantic satiation in a flanked-category verification task. In the experiment, a target pair (FRUIT grape) was flanked by a distractor (i.e., flanker). There were three conditions; compatible condition in which flankers were semantically related to a target category word (FRUIT grape vs. apple), incompatible condition in which flankers were not related (FRUIT grape vs. coffee), baseline condition in which flankers were not presented. Seventy-three college students participated in the experiment and judged whether or not a instance word was related to a category word in the target pair. As a result, the semantic satiation effect was found regardless of flanker conditions. Additionally, the influence of flanker was not attenuated by prime repetitions. These results were elucidated in terms of decision criterion based on a semantic relatedness of prime and target instance words. A possibility indicated that the locus of decision criteria was shifted to a more careful one by prolonged prime repetitions. Finally, one explanation was discussed that an influence of satiation would be emerged from the process which suited semantic information to the context.     

MEG study on neural activities associated with syntactic and semantic violations in spoken Korean sentences

We carried out an magnetoencephalography (MEG) study to record cortical responses elicited in the left hemisphere by ending verb phrases, which had syntactic or semantic anomalies, in Korean sentences of subject-object-verb order. Using the high temporal and spatial resolution of MEG, the study was aimed at identifying neural activities that occur during a latency course associated with the syntactic or semantic process in the spoken sentence. Major responses, distinct from the responses to normal sentences, were observed in two latency periods of about 400 and 600 ms following the onset of the verb phrase. Source localization of the grand average fields indicated separate activities in the inferior frontal region and the vicinity of the auditory cortex for the first 400-ms response to the syntactic anomaly. The region around the auditory cortex was indicated for the response to the semantic anomaly in a similar latency. The second 600-ms response indicated activity around the middle temporal gyrus inferior to the auditory cortex for both syntactic and semantic anomalies. The results are discussed with reference to the ERP components established for Indo-European languages, and the possibility of concurrent processing of syntactic and semantic aspects is suggested.     

Computational modelling of the effects of semantic dementia on visual word recognition

Rogers, Lambon Ralph, Hodges, and Patterson (2004) Rogers, T. T., Lambon Ralph, M. A., Hodges, J. R. and Patterson, K. 2004. Natural selection: The impact of semantic impairment on lexical and object decision. Cognitive Neuropsychology, 21: 331–352. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] studied two-alternative forced-choice visual lexical decision performance in patients with semantic dementia. With item pairs where the target word was more “typical” (i.e., higher in bigram and trigram frequency) than the foil (all foils were pseudohomophones), lexical decision performance was good and was unaffected by word frequency. With item pairs where the target word was less “typical” (i.e., lower in bigram and trigram frequency) than the foil, lexical decision performance was worse and was affected by word frequency, being particularly inaccurate when the word targets were low in frequency. We show (using as materials all the monosyllabic items used by Rogers and colleagues) that the same pattern of results occurs in the lexical decision performance of the DRC (dual-route cascaded) computational model of reading when the model is lesioned by probabilistic deletion of low-frequency words from its orthographic lexicon. We consider that the PDP (parallel distributed processing) computational model of reading used by Woollams, Plaut, Lambon Ralph, and Patterson (2007) to simulate reading in semantic dementia is not capable of simulating this lexical decision result. We take this, in conjunction with previous work on computational modelling of reading aloud in surface dyslexia, phonological dyslexia, and semantic dementia using the DRC and PDP reading models, to indicate that the DRC model does a better job than the PDP model in accounting for what is known about the various forms of acquired dyslexia.     

A controlled study of processing of semantic and syntactic information in Alzheimer's disease.

Several previous studies have suggested a possible dissociation in the ability of patients with Alzheimer's Disease (AD) to utilize syntactic versus semantic information. This report describes a controlled experimental investigation of AD subjects' ability to process syntactic and semantic information. Thirteen mildly and moderately impaired AD patients were compared with 17 age- and education-matched elderly controls. Two tasks required subjects to identify and correct sentential errors; a third was a homophone spelling task. Results of the first task indicated that AD subjects were equivalent to controls in their ability to detect various types of sentential errors. When performing the second task, AD subjects were impaired in their ability to correct both types of errors, although there was a tendency for better performance with syntactically-based corrections. The third (homophone-spelling) task did not reveal a statistically significant differential sensitivity of AD subjects to syntactic versus semantic information. However, there was again a tendency for the former to be more easily processed. Results are discussed in terms of possible mechanisms which may underlie variations in the language-related performance of AD subjects.     

How and when prosodic boundaries influence syntactic parsing under different discourse contexts: An ERP study

In the present study, the ERP (event-related brain potentials) technique was used to investigate how and when prosodic boundaries interact with ongoing discourse context during on-line syntactic processing and especially the precise time characteristics of this prosodic boundaries effect. Chinese question-answer dialogues were used as stimuli. The answers were syntactically ambiguous phrases, the meaning of which could be biased via changing the preceding question context or the prosodic boundaries in the carrier sentence. The results revealed that, first, presence of prosodic boundaries, relative to absence of these boundaries, evoked a P2 effect. Second and importantly, there was an immediate interaction between discourse context and prosodic boundaries. When the prosodic boundaries were inconsistent with the syntactic interpretation built upon the ongoing discourse context, a left-anterior distributed LAN effect or a combined LAN and N400 effect was elicited (time-locked to the critical words at the immediate right side of prosodic boundaries). The results indicated that prosodic boundaries can be used to guide syntactic parsing and can be immediately integrated with the ongoing discourse context during spoken discourse comprehension. In addition, the LAN effect elicited by prosodic boundaries violation indicated that prosodic information may affect the initial incorporation of a word into the syntactic structure in speech processing.     

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

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

Early components of event-related potentials related to semantic and syntactic processes in the Japanese language

Brain activities were compared between semantic and syntactic processing in the Japanese language using event-related potentials with a 58-ch EEG system. We previously found that semantic violations elicited N400 and syntactic violations elicited P600 but not early left anterior negativity (ELAN) or left anterior negativity (LAN) using a relatively long stimulus presentation time (1 s). In the present study, we adopted a shorter stimulus presentation time (0.5 s), which might impose a heavier burden on the working memory system, to test the possible relevance of load on the working memory system to ELAN/LAN. A global field power analysis showed an increased potential field strength at the latency of 320 ms in either type, as well as those at the later latencies reflecting N400 (556 ms) and P600 (712 ms). Statistical analyses revealed a significant negative deflection in the right frontal region for the semantic type, whereas no significant deflection in either specified region was obtained for the syntactic type at the latency of 320 ms. The lack of ELAN/LAN suggested that it was not due to the deactivation of the working memory system. Moreover, scalp current density topographies implied that the processing of the verbal stimuli was mediated by distinct areas within the left temporal region, according to its semantic congruency with the preceding context at a latency as early as 320 ms. These findings are in line with the dual-route hypothesis of reading, which suggests that the reading of verbal stimuli semantically incongruent with the preceding context is dominated by phonological processes rather than lexico-semantic.     

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.     

The interplay between semantic and phonological constraints during spoken‐word comprehension

This study addresses how top‐down predictions driven by phonological and semantic information interact on spoken‐word comprehension. To do so, we measured event‐related potentials to words embedded in sentences that varied in the degree of semantic constraint (high or low) and in regional accent (congruent or incongruent) with respect to the target word pronunciation. The data showed a negative amplitude shift following phonological mismatch (target pronunciation incongruent with respect to sentence regional accent). Here, we show that this shift is modulated by sentence‐level semantic constraints over latencies encompassing auditory (N100) and lexical (N400) components. These findings suggest a fast influence of top‐down predictions and the interplay with bottom‐up processes at sublexical and lexical levels of analysis.     

Age-related changes in word retrieval: role of bilateral frontal and subcortical networks

Healthy older adults frequently report word-finding difficulties, yet the underlying cause of these problems is not well understood. This study examined whether age-related changes in word retrieval are related to changes in areas of the frontal lobes thought to subserve word retrieval or changes in areas of the inferior temporal lobes thought to be involved in semantic knowledge. Twenty younger and 20 older healthy adults named aloud photographs during event-related fMRI. Results showed that in the face of equivalent naming accuracy, older adults activated a larger frontal network than younger adults during word retrieval, but there were no activity differences between groups in the fusiform gyrus, suggesting that the substrates for word retrieval but not for semantic knowledge change with aging. Additionally, correlations between BOLD response and naming accuracy and response latency were found in several frontal and subcortical regions in older adults. Findings are discussed in the context of possible compensatory mechanisms invoked to maintain performance in healthy aging, and suggest that increased involvement of the right hemisphere is not universally beneficial to performance.     

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

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

A comparison of phonemic, semantic, and alternating word fluency in Parkinson's disease.

Word fluency in 45 medicated non-demented Parkinson's disease (PD) patients and 45 normal control subjects was studied with a Phonemic Word Fluency (PWF) task using the letters F, A, and S, a Semantic Word Fluency (SWF) task using the categories animals, boys' names, and states, and an Alternating Word Fluency (AWF) task requiring the person to alternate between colors and occupations, animals and states, and words beginning with C and P. The number of words generated did not differ for trials with F, A, S, or states, but PD patients generated significantly fewer animal names and boys' names. PD patients also generated significantly fewer words on each of the three AWF trials. The PD patients scored 21% lower than the normal control group on the total AWF score, but only 10% lower for the PWF and SWF scores. The greater impairment on the AWF task which requires the use of internal attentional control to rapidly shift mental set can be considered a type of executive functioning deficit. This is consistent with the growing literature suggesting frontal systems dysfunction in PD and with the view that dopaminergic treatment only incompletely restores functioning in the frontostriatal system.     

Comparing arithmetic and semantic fact retrieval: Effects of problem size and sentence constraint on event-related brain potentials

Event-related potentials were recorded with 61 electrodes from 16 students who verified either the correctness of single-digit multiplication problems or the semantic congruency of sentences. Multiplication problems varied in size and sentence fragments in constraint. Both semantic and arithmetic incongruencies evoked a typical N400 with a clear parieto-central maximum. In addition, numerically larger problems (8×7), in comparison to smaller problems (3×2), evoked a negativity starting at about 360 ms whose maximum was located over the right temporal-parietal scalp. These results indicate that the arithmetic incongruency and the problem-size effect are functionally distinct. It is suggested that the arithmetic and the semantic incongruency effects are both functionally related to a context-dependent spread of activation in specialized associative networks, whereas the arithmetic problem-size effect is due to rechecking routines that go beyond basic fact retrieval.     

Olfaction and its dynamic influence on word and face processing: cross-modal integration

The article specifies several important aspects related to the sense of smell in vertebrates. The idea that odors exert effects in the human brain though being not consciously perceived is introduced. Functional aspects related to cross-modal sensory interaction between olfaction and vision are highlighted. In particular, studies making use of electrophysiological methods providing high temporal resolution reveal an early processing stage around 300 ms and a later stage around 700 ms after stimulus onset. The early stage has been associated with subconscious olfactory information processing, whereas the later stage most likely reflects conscious odor perception. Specific interactions are described between olfaction and language and between olfaction and face processing in correlation with both stages of olfactory information processing. A consciously perceived odor can negatively affect language and face processing if these stimuli are presented and associated simultaneously, whereas simultaneous subconscious odor processing has the potential to improve memory formation in other stimulus modalities. Strikingly, the subconscious effect seems not to depend on odor valence. Besides a better understanding of the sense of olfaction itself, these findings on cross-modal integration support the idea that neural representations exist for semantic contents (object meaning) independent from particular sensory modalities. These representations can be referred to as meta representations because the information they contain is derived from a great variety of sensory information integrated into a semantic representation of an object. It is suggested that such meta representations represent the basic units for cognition and that they provide inputs during dreaming.     

Comparing arithmetic and semantic fact retrieval: effects of problem size and sentence constraint on event-related brain potentials

Event-related potentials were recorded with 61 electrodes from 16 students who verified either the correctness of single-digit multiplication problems or the semantic congruency of sentences. Multiplication problems varied in size and sentence fragments in constraint. Both semantic and arithmetic incongruencies evoked a typical N400 with a clear parieto-central maximum. In addition, numerically larger problems (8x7), in comparison to smaller problems (3x2), evoked a negativity starting at about 360 ms whose maximum was located over the right temporal-parietal scalp. These results indicate that the arithmetic incongruency and the problem-size effect are functionally distinct. It is suggested that the arithmetic and the semantic incongruency effects are both functionally related to a context-dependent spread of activation in specialized associative networks, whereas the arithmetic problem-size effect is due to rechecking routines that go beyond basic fact retrieval.