How Distance Affects Semantic Integration in Discourse: Evidence from Event-Related Potentials

Event-related potentials were used to investigate whether semantic integration in discourse is influenced by the number of intervening sentences between the endpoints of integration. Readers read discourses in which the last sentence contained a critical word that was either congruent or incongruent with the information introduced in the first sentence. Furthermore, for the short discourses, the first and last sentence were intervened by only one sentence while for the long discourses, they were intervened by three sentences. We found that the incongruent words elicited an N400 effect for both the short and long discourses. However, a P600 effect was only observed for the long discourses, but not for the short ones. These results suggest that although readers can successfully integrate upcoming words into the existing discourse representation, the effort required for this integration process is modulated by the number of intervening sentences. Thus, discourse distance as measured by the number of intervening sentences should be taken as an important factor for semantic integration in discourse.     

Integration of Sentence-Level Semantic Information in Parafovea: Evidence from the RSVP-Flanker Paradigm

During text reading, the parafoveal word was usually presented between 2° and 5° from the point of fixation. Whether semantic information of parafoveal words can be processed during sentence reading is a critical and long-standing issue. Recently, studies using the RSVP-flanker paradigm have shown that the incongruent parafoveal word, presented as right flanker, elicited a more negative N400 compared with the congruent parafoveal word. This suggests that the semantic information of parafoveal words can be extracted and integrated during sentence reading, because the N400 effect is a classical index of semantic integration. However, as most previous studies did not control the word-pair congruency of the parafoveal and the foveal words that were presented in the critical triad, it is still unclear whether such integration happened at the sentence level or just at the word-pair level. The present study addressed this question by manipulating verbs in Chinese sentences to yield either a semantically congruent or semantically incongruent context for the critical noun. In particular, the interval between the critical nouns and verbs was controlled to be 4 or 5 characters. Thus, to detect the incongruence of the parafoveal noun, participants had to integrate it with the global sentential context. The results revealed that the N400 time-locked to the critical triads was more negative in incongruent than in congruent sentences, suggesting that parafoveal semantic information can be integrated at the sentence level during Chinese reading.     

Working Memory Is Partially Preserved during Sleep

Although several cognitive processes, including speech processing, have been studied during sleep, working memory (WM) has never been explored up to now. Our study assessed the capacity of WM by testing speech perception when the level of background noise and the sentential semantic length (SSL) (amount of semantic information required to perceive the incongruence of a sentence) were modulated. Speech perception was explored with the N400 component of the event-related potentials recorded to sentence final words (50% semantically congruent with the sentence, 50% semantically incongruent). During sleep stage 2 and paradoxical sleep: (1) without noise, a larger N400 was observed for (short and long SSL) sentences ending with a semantically incongruent word compared to a congruent word (i.e. an N400 effect); (2) with moderate noise, the N400 effect (observed at wake with short and long SSL sentences) was attenuated for long SSL sentences. Our results suggest that WM for linguistic information is partially preserved during sleep with a smaller capacity compared to wake.     

Semantics in action: an electrophysiological study on the use of semantic knowledge for action.

Recent studies have supported close interactions between language and action-related processes, suggesting comparable neural mechanisms. However, relatively little is known about the semantics involved in action planning. The present study investigated the activation of semantic knowledge in meaningful actions by recording event-related potentials (ERPs). Subjects prepared meaningful or meaningless actions with objects and made a semantic categorization response before executing the action. Words presented could be either congruent or incongruent with respect to the goal of the action. Preparation of meaningful actions elicited a larger anterior N400 for words incongruent to the present action goal as compared to congruent words, while no N400 effect was found when subjects prepared meaningless actions. These findings indicate that the preparation of meaningful actions with objects is accompanied by the activation of semantic information representing the usual action goals associated with those objects.     

Eye Movement Evidence for Hierarchy Effects on Memory Representation of Discourses

In this study, we applied the text-change paradigm to investigate whether and how discourse hierarchy affected the memory representation of a discourse. Three kinds of three-sentence discourses were constructed. In the hierarchy-high condition and the hierarchy-low condition, the three sentences of the discourses were hierarchically organized and the last sentence of each discourse was located at the high level and the low level of the discourse hierarchy, respectively. In the linear condition, the three sentences of the discourses were linearly organized. Critical words were always located at the last sentence of the discourses. These discourses were successively presented twice and the critical words were changed to semantically related words in the second presentation. The results showed that during the early processing stage, the critical words were read for longer times when they were changed in the hierarchy-high and the linear conditions, but not in the hierarchy-low condition. During the late processing stage, the changed-critical words were again found to induce longer reading times only when they were in the hierarchy-high condition. These results suggest that words in a discourse have better memory representation when they are located at the higher rather than at the lower level of the discourse hierarchy. Global discourse hierarchy is established as an important factor in constructing the mental representation of a discourse.     

Cortical Dynamics of Semantic Processing during Sentence Comprehension: Evidence from Event-Related Optical Signals

Using the event-related optical signal (EROS) technique, this study investigated the dynamics of semantic brain activation during sentence comprehension. Participants read sentences constituent-by-constituent and made a semantic judgment at the end of each sentence. The EROSs were recorded simultaneously with ERPs and time-locked to expected or unexpected sentence-final target words. The unexpected words evoked a larger N400 and a late positivity than the expected ones. Critically, the EROS results revealed activations first in the left posterior middle temporal gyrus (LpMTG) between 128 and 192 ms, then in the left anterior inferior frontal gyrus (LaIFG), the left middle frontal gyrus (LMFG), and the LpMTG in the N400 time window, and finally in the left posterior inferior frontal gyrus (LpIFG) between 832 and 864 ms. Also, expected words elicited greater activation than unexpected words in the left anterior temporal lobe (LATL) between 192 and 256 ms. These results suggest that the early lexical-semantic retrieval reflected by the LpMTG activation is followed by two different semantic integration processes: a relatively rapid and transient integration in the LATL and a relatively slow but enduring integration in the LaIFG/LMFG and the LpMTG. The late activation in the LpIFG, however, may reflect cognitive control.     

The Relation between Thematic Role Computing and Semantic Relatedness Processing during On-Line Sentence Comprehension

Sentence comprehension involves timely computing different types of relations between its verbs and noun arguments, such as morphosyntactic, semantic, and thematic relations. Here, we used EEG technique to investigate the potential differences in thematic role computing and lexical-semantic relatedness processing during on-line sentence comprehension, and the interaction between these two types of processes. Mandarin Chinese sentences were used as materials. The basic structure of those sentences is “Noun+Verb+‘le’+a two-character word”, with the Noun being the initial argument. The verb disambiguates the initial argument as an agent or a patient. Meanwhile, the initial argument and the verb are highly or lowly semantically related. The ERPs at the verbs revealed that: relative to the agent condition, the patient condition evoked a larger N400 only when the argument and verb were lowly semantically related; however, relative to the high-relatedness condition, the low-relatedness condition elicited a larger N400 regardless of the thematic relation; although both thematic role variation and semantic relatedness variation elicited N400 effects, the N400 effect elicited by the former was broadly distributed and reached maximum over the frontal electrodes, and the N400 effect elicited by the latter had a posterior distribution. In addition, the brain oscillations results showed that, although thematic role variation (patient vs. agent) induced power decreases around the beta frequency band (15–30 Hz), semantic relatedness variation (low-relatedness vs. high-relatedness) induced power increases in the theta frequency band (4–7 Hz). These results suggested that, in the sentence context, thematic role computing is modulated by the semantic relatedness between the verb and its argument; semantic relatedness processing, however, is in some degree independent from the thematic relations. Moreover, our results indicated that, during on-line sentence comprehension, thematic role computing and semantic relatedness processing are mediated by distinct neural systems.     

Event-related brain potentials during semantic categorization in normal aging and senile dementia of the Alzheimer's type

To assess the effects of normal aging and senile dementia of the Alzheimer's type (SDAT) on semantic analysis of words, we examined the N400 component of the event-related potential (ERP) elicited during the processing of highly constrained (opposites) and less constrained materials (category-category exemplars) in 12 young control subjects, 12 elderly control subjects and 12 patients with SDAT. We employed a priming paradigm in which a context phrase was spoken and a target word (congruent or incongruent) was presented visually. The N400 effect was reduced in amplitude and delayed in the elderly control group relative to that of the younger subjects, and was further attenuated in amplitude, delayed in latency and somewhat flatter in its distribution across the scalp in the SDAT patients. These findings are consistent with less efficient processing and integration of lexical items with semantic context in normal aging, which is further exacerbated by SDAT. Differences in the N400 range associated with the opposite and category conditions were observed only in the young subjects, suggesting less use of controlled attentional resources or perhaps weaker associative links with age.     

How Is Sentence Processing Affected by External Semantic and Syntactic Information? Evidence from Event-Related Potentials

Background

A crucial question for understanding sentence comprehension is the openness of syntactic and semantic processes for other sources of information. Using event-related potentials in a dual task paradigm, we had previously found that sentence processing takes into consideration task relevant sentence-external semantic but not syntactic information. In that study, internal and external information both varied within the same linguistic domain—either semantic or syntactic. Here we investigated whether across-domain sentence-external information would impact within-sentence processing.

Methodology

In one condition, adjectives within visually presented sentences of the structure [Det]-[Noun]-[Adjective]-[Verb] were semantically correct or incorrect. Simultaneously with the noun, auditory adjectives were presented that morphosyntactically matched or mismatched the visual adjectives with respect to gender.

Findings

As expected, semantic violations within the sentence elicited N400 and P600 components in the ERP. However, these components were not modulated by syntactic matching of the sentence-external auditory adjective. In a second condition, syntactic within-sentence correctness-variations were combined with semantic matching variations between the auditory and the visual adjective. Here, syntactic within-sentence violations elicited a LAN and a P600 that did not interact with semantic matching of the auditory adjective. However, semantic mismatching of the latter elicited a frontocentral positivity, presumably related to an increase in discourse level complexity.

Conclusion

The current findings underscore the open versus algorithmic nature of semantic and syntactic processing, respectively, during sentence comprehension.     

Applauding with Closed Hands: Neural Signature of Action-Sentence Compatibility Effects

Background

Behavioral studies have provided evidence for an action–sentence compatibility effect (ACE) that suggests a coupling of motor mechanisms and action-sentence comprehension. When both processes are concurrent, the action sentence primes the actual movement, and simultaneously, the action affects comprehension. The aim of the present study was to investigate brain markers of bidirectional impact of language comprehension and motor processes.

Methodology/Principal Findings

Participants listened to sentences describing an action that involved an open hand, a closed hand, or no manual action. Each participant was asked to press a button to indicate his/her understanding of the sentence. Each participant was assigned a hand-shape, either closed or open, which had to be used to activate the button. There were two groups (depending on the assigned hand-shape) and three categories (compatible, incompatible and neutral) defined according to the compatibility between the response and the sentence. ACEs were found in both groups. Brain markers of semantic processing exhibited an N400-like component around the Cz electrode position. This component distinguishes between compatible and incompatible, with a greater negative deflection for incompatible. Motor response elicited a motor potential (MP) and a re-afferent potential (RAP), which are both enhanced in the compatible condition.

Conclusions/Significance

The present findings provide the first ACE cortical measurements of semantic processing and the motor response. N400-like effects suggest that incompatibility with motor processes interferes in sentence comprehension in a semantic fashion. Modulation of motor potentials (MP and RAP) revealed a multimodal semantic facilitation of the motor response. Both results provide neural evidence of an action-sentence bidirectional relationship. Our results suggest that ACE is not an epiphenomenal post-sentence comprehension process. In contrast, motor-language integration occurring during the verb onset supports a genuine and ongoing brain motor-language interaction.     

Auditory event-related potentials to semantic priming during sleep

The present study uses the N400 component of event-related potentials (ERPs) as a processing marker of single spoken words presented during sleep. Thirteen healthy volunteers participated in the study. The auditory ERPs were registered in response to a semantic priming paradigm made up of pairs of words (50% related, 50% unrelated) presented in the waking state and during sleep stages II, III–IV and REM. The amplitude, latency and scalp distribution parameters of the negativity observed during stage II and the REM stage were contrasted with the results obtained in the waking state. The `N400-like' effect elicited in these stages of sleep showed a mean amplitude for pairs of unrelated words significantly greater than for related pairs and an increment of latency. These results suggest that during these sleep stages a semantic priming effect is maintained actively although the lexical processing time increases.     

Words and Melody Are Intertwined in Perception of Sung Words: EEG and Behavioral Evidence

Language and music, two of the most unique human cognitive abilities, are combined in song, rendering it an ecological model for comparing speech and music cognition. The present study was designed to determine whether words and melodies in song are processed interactively or independently, and to examine the influence of attention on the processing of words and melodies in song. Event-Related brain Potentials (ERPs) and behavioral data were recorded while non-musicians listened to pairs of sung words (prime and target) presented in four experimental conditions: same word, same melody; same word, different melody; different word, same melody; different word, different melody. Participants were asked to attend to either the words or the melody, and to perform a same/different task. In both attentional tasks, different word targets elicited an N400 component, as predicted based on previous results. Most interestingly, different melodies (sung with the same word) elicited an N400 component followed by a late positive component. Finally, ERP and behavioral data converged in showing interactions between the linguistic and melodic dimensions of sung words. The finding that the N400 effect, a well-established marker of semantic processing, was modulated by musical melody in song suggests that variations in musical features affect word processing in sung language. Implications of the interactions between words and melody are discussed in light of evidence for shared neural processing resources between the phonological/semantic aspects of language and the melodic/harmonic aspects of music.     

Electrophysiological bases of semantic processing of objects

How pictures and words are stored and processed in the human brain constitute a long-standing question in cognitive psychology. Behavioral studies have yielded a large amount of data addressing this issue. Generally speaking, these data show that there are some interactions between the semantic processing of pictures and words. However, behavioral methods can provide only limited insight into certain findings. Fortunately, Event-Related Potential (ERP) provides on-line cues about the temporal nature of cognitive processes and contributes to the exploration of their neural substrates. ERPs have been used in order to better understand semantic processing of words and pictures. The main objective of this article is to offer an overview of the electrophysiologic bases of semantic processing of words and pictures. Studies presented in this article showed that the processing of words is associated with an N 400 component, whereas pictures elicited both N 300 and N 400 components. Topographical analysis of the N 400 distribution over the scalp is compatible with the idea that both image-mediated concrete words and pictures access an amodal semantic system. However, given the distinctive N 300 patterns, observed only during picture processing, it appears that picture and word processing rely upon distinct neuronal networks, even if they end up activating more or less similar semantic representations.     

Differences in the late components of the event-related potential due to age and to semantic and non-semantic tasks

Recent work in event-related potentials (ERPs) has revealed differences between ERPs elicited during the performance of semantic and non-semantic tasks. This experiment examined age differences in the late components of the ERP as a function of these tasks. Young and elderly males were presented with 5-word strings on each trial. The subject's task was to decide whether or not the fifth word matched the other four. In one condition, the first 4 words were identical to one another and the fifth word was either the same or different. In the other condition, the first 4 words were different from one another but were drawn from from the same semantic category. The fifth word was either from the category or from a different category. Matches occurred in 15% of the trials and mismatches in 85%. The ERP to the fifth word was analyzed. All ERPs evidenced a late positive component (LPC), the latency of which was greater for the Category task and for mismatches. LPC amplitude was greater in the Identity task. In addition, young subjects' LPC amplitudes were greater for matches than for mismatches, whereas the reverse was true for the elderly. In agreement with previous research, our results indicated that an N400 wave is evident only in response to semantic incongruity and that variables affecting late positive activity seem to be independent of those producing N400. The N400 wave was seen at a greater latency in the elderly. Our results extend previous work (e.g., Kutas and Hillyard 1980) by finding an N400 in a semantic context other than sentences, and in concluding that this component is relatively insensitive to stimulus frequency.     

Emotional Meaning in Context in Relation to Hypomanic Personality Traits: An ERP Study

The ability to integrate contextual information is important for the comprehension of emotional and social situations. While some studies have shown that emotional processes and social cognition are impaired in people with hypomanic personality trait, no results have been reported concerning the neurophysiological processes mediating the processing of emotional information during the integration of contextual social information in this population. We therefore chose to conduct an ERP study dealing with the integration of emotional information in a population with hypomanic personality trait. Healthy participants were evaluated using the Hypomanic Personality Scale (HPS), and ERPs were recorded during a linguistic task in which participants silently read sentence pairs describing short social situations. The first sentence implicitly conveyed the positive or negative emotional state of a character. The second sentence was emotionally congruent or incongruent with the first sentence. We analyzed the difference in the modulation of two components (N400 and LPC) in response to the emotional word present at the end of the “target” sentences as a function of the HPS score and the emotional valence of the context. Our results showed a possible modulation of the N400 component in response to both positive and negative context among the participants who scored high on the Mood Volatility subscale of the Hypomanic Personality Scale. These results seem to indicate that the participants with hypomanic personality traits exhibited specificities in the integration of emotions at the level of the early-mobilized neurocognitive processes (N400). Participants with hypomanic personality traits found it difficult to integrate negative emotional contexts, while simultaneously exhibiting an enhanced integration of positive emotional contexts.     

Re-Examination of Chinese Semantic Processing and Syntactic Processing: Evidence from Conventional ERPs and Reconstructed ERPs by Residue Iteration Decomposition (RIDE)

A number of studies have explored the time course of Chinese semantic and syntactic processing. However, whether syntactic processing occurs earlier than semantics during Chinese sentence reading is still under debate. To further explore this issue, an event-related potentials (ERPs) experiment was conducted on 21 native Chinese speakers who read individually-presented Chinese simple sentences (NP1+VP+NP2) word-by-word for comprehension and made semantic plausibility judgments. The transitivity of the verbs was manipulated to form three types of stimuli: congruent sentences (CON), sentences with a semantically violated NP2 following a transitive verb (semantic violation, SEM), and sentences with a semantically violated NP2 following an intransitive verb (combined semantic and syntactic violation, SEM+SYN). The ERPs evoked from the target NP2 were analyzed by using the Residue Iteration Decomposition (RIDE) method to reconstruct the ERP waveform blurred by trial-to-trial variability, as well as by using the conventional ERP method based on stimulus-locked averaging. The conventional ERP analysis showed that, compared with the critical words in CON, those in SEM and SEM+SYN elicited an N400–P600 biphasic pattern. The N400 effects in both violation conditions were of similar size and distribution, but the P600 in SEM+SYN was bigger than that in SEM. Compared with the conventional ERP analysis, RIDE analysis revealed a larger N400 effect and an earlier P600 effect (in the time window of 500–800 ms instead of 570–810ms). Overall, the combination of conventional ERP analysis and the RIDE method for compensating for trial-to-trial variability confirmed the non-significant difference between SEM and SEM+SYN in the earlier N400 time window. Converging with previous findings on other Chinese structures, the current study provides further precise evidence that syntactic processing in Chinese does not occur earlier than semantic processing.     

How the speed of working memory updating influences the on-line thematic processing of simple sentences in Mandarin Chinese

This ERP study used electrophysiological technique to examine how individual differences in the speed of working memory updating influence the use of syntactic and semantic information during on-line sentence argument interpretation, and the time course of that working memory updating effect. The basic structure of the experimental sentences was “Noun + Verb + adverb + ‘le’ + a two-character word”, with the Noun being the sentence initial argument. This initial argument is animate or inanimate and the following verb disambiguates it as an agent or patient. The results at the initial argument revealed that, the quick-updating group elicited a larger positivity over the frontal cortex (within 500–800 ms post-noun onset) as compared with the slow-updating group. At the following disambiguating verb, the slow-updating group only showed a word order effect, indicating that the patient-first condition elicited a larger P600 (within 500–1,000 ms post-verb onset) than the agent-first one; for the quick-updating group, at the early stage of processing, the patient-first sentences elicited a larger N400 (within 300–500 ms post-verb onset) than the agent-first ones only when the initial argument was inanimate; however, at the late stage, the patient-first sentences elicited an enhanced P600 (within 800–1,000 ms post-verb onset) only when the initial argument was animate. These results suggested that the speed of working memory updating not only influences the maintenance of sentence argument when the contents of working memory change but also influences the efficiency of integrating that argument with the verb at a late time point. When integrating the argument with the disambiguating verb, individuals with quick-updating ability can combine multiple sources of information (both noun animacy and word order), and conduct rapid and fine-grained two-stage processing; individuals with slow-updating ability, however, only rely on one dominant source of information types (word order), and conducted slow and course-grained processing.     

The N400 in a semantic categorization task across 6 decades

Objectives: To characterize the effects of normal aging on the amplitude, latency and scalp distribution of the N400 congruity effect.Methods: Event-related brain potentials (ERPs) were recorded from 72 adults (half of them men) between the ages of 20 and 80 years (12/decade) as they performed a semantic categorization task. Participants listened to spoken phrases (e.g. `a type of fruit' or `the opposite of black') followed about 1 s later by a visually-presented word that either did or did not fit with the sense of the preceding phrase; they reported the word read and whether or not it was appropriate. ERP measurements (mean amplitudes, peak amplitudes, peak latencies) were subjected to analysis of variance and linear regression analyses.Results: All participants, regardless of age, produced larger N400s to words that did not fit than to those that did. The N400 congruity effect (no-fit ERPs−fit ERPs) showed a reliable linear decrease in the amplitude (0.05–0.09 μV per year, r=0.40) and a reliable linear increase peak latency (1.5–2.1 ms/year, r=0.60) with age.Conclusions: In sum, the N400 semantic congruity effect at the scalp gets smaller, slower and more variable with age, consistent with a quantitative rather than qualitative change in semantic processing (integration) with normal aging.