The reading brain extracts syntactic information from multiple words within 50 milliseconds

To what extent do readers process multiple words in parallel? Although it is now commonly accepted that letters are processed across multiple words simultaneously, higher-order (lexical, semantic, syntactic) parallel processing remains contentious. Recent use of the flanker paradigm has revealed that the syntactic recognition of foveal target words is influenced by the syntactic congruency of parafoveal flanking words even when target and flankers are shown for only 170 ms. It has been argued, however, that such settings may allow processing of multiple words even if this were to happen on a serial one-by-one basis. To circumvent this possibility, here I have tested participants in a syntactic categorization task whereby targets and flankers were shown for only 50 ms and replaced by post-masks. Significant effects of target-flanker congruency were observed in both response times and accuracy, indicating that readers extracted syntactic information from multiple words within the very brief presentation time. The present results strongly suggest that the brain extracts higher-order linguistic information from multiple words in parallel.

Interpreting Rhythm as Parsing: Syntactic-Processing Operations Predict the Migration of Visual Flashes as Perceived During Listening to Musical Rhythms

Music can be interpreted by attributing syntactic relationships to sequential musical events, and, computationally, such musical interpretation represents an analogous combinatorial task to syntactic processing in language. While this perspective has been primarily addressed in the domain of harmony, we focus here on rhythm in the Western tonal idiom, and we propose for the first time a framework for modeling the moment-by-moment execution of processing operations involved in the interpretation of music. Our approach is based on (1) a music-theoretically motivated grammar formalizing the competence of rhythmic interpretation in terms of three basic types of dependency (preparation, syncopation, and split; Rohrmeier, 2020), and (2) psychologically plausible predictions about the complexity of structural integration and memory storage operations, necessary for parsing hierarchical dependencies, derived from the dependency locality theory (Gibson, 2000). With a behavioral experiment, we exemplify an empirical implementation of the proposed theoretical framework. One hundred listeners were asked to reproduce the location of a visual flash presented while listening to three rhythmic excerpts, each exemplifying a different interpretation under the formal grammar. The hypothesized execution of syntactic-processing operations was found to be a significant predictor of the observed displacement between the reported and the objective location of the flashes. Overall, this study presents a theoretical approach and a first empirical proof-of-concept for modeling the cognitive process resulting in such interpretation as a form of syntactic parsing with algorithmic similarities to its linguistic counterpart. Results from the present small-scale experiment should not be read as a final test of the theory, but they are consistent with the theoretical predictions after controlling for several possible confounding factors and may form the basis for further large-scale and ecological testing.

Diffuse glioma-induced structural reorganization in close association with preexisting syntax-related networks

Glioma in the left frontal cortex has been reported to cause agrammatic comprehension and induce global functional connectivity alterations within the syntax-related networks. However, it remains unclear to what extent the structural reorganization is affected by preexisting syntax-related networks. We examined 28 patients with a diffuse glioma in the left hemisphere and 23 healthy participants. Syntactic abilities were assessed by a picture-sentence matching task with various sentence types. The lesion responsible for agrammatic comprehension was identified by region-of-interest-based lesion-symptom mapping (RLSM). Cortical structural alterations were examined by surface-based morphometry (SBM), in which the cortical thickness and fractal dimension were measured with three-dimensional magnetic resonance imaging (MRI). Fiber tracking on the human population-averaged diffusion MRI template was performed to examine whether the cortical structural alterations were associated with the syntax-related networks. The RLSM revealed associations between agrammatic comprehension and a glioma in the posterior limb of the left internal capsule. The SBM demonstrated that decreased cortical thickness and/or increased complexity of the right posterior insula were associated not only with agrammatic comprehension of the patients but also with the syntactic abilities of healthy participants. The fiber tracking revealed that the route between these two regions was anatomically integrated into the preexisting syntax-related networks previously identified. These results suggest a potential association between agrammatic comprehension in patients with diffuse glioma and structural variations in specific tracts and cortical regions, which may be closely related to the syntax-related networks.

Cross-clause planning in Nungon (Papua New Guinea): Eye-tracking evidence

Hundreds of languages worldwide use a sentence structure known as the "clause chain," in which 20 or more clauses can be stacked to form a sentence. The Papuan language Nungon is among a subset of clause chaining languages that require "switch-reference" suffixes on nonfinal verbs in chains. These suffixes announce whether the subject of each upcoming clause will differ from the subject of the previous clause. We examine two major issues in psycholinguistics: predictive processing in comprehension, and advance planning in production. Whereas previous work on other languages has demonstrated that sentence planning can be incremental, switch-reference marking would seem to prohibit strictly incremental planning, as it requires speakers to plan the next clause before they can finish producing the current one. This suggests an intriguing possibility: planning strategies may be fundamentally different in Nungon. We used a mobile eye-tracker and solar-powered laptops in a remote village in Papua, New Guinea, to track Nungon speakers' gaze in two experiments: comprehension and production. Curiously, during comprehension, fixation data failed to find evidence that switch-reference marking is used for predictive processing. However, during production, we found evidence for advance planning of switch-reference markers, and, by extension, the subjects they presage. We propose that this degree of advance syntactic planning pushes the boundaries of what is known about sentence planning, drawing on data from a novel morpheme type in an understudied language.

Syntactic and Semantic Processing in Japanese Sentence Reading: A Research Using Functional Near-Infrared Spectroscopy (fNIRS)

In order to examine whether syntactic processing is a necessary prerequisite for semantic integration in Japanese, cortical activation was monitored while participants engaged in silent reading task. Congruous sentences (CON), semantic violation sentences (V-SEM), and syntactic violation sentences (V-SYN) were presented in the experiment. The participants' oxygenated hemoglobin concentration changes during the reading task were measured using functional near-infrared spectroscopy. The results suggest that the CON sentences did not require additional cognitive load on syntactic processing or semantic processing. The V-SEM sentences demanded great cognitive load on semantic processing. Besides, it also elicited great cognitive load on syntactic processing. The V-SYN sentences induced great cognitive load on syntactic processing, but it did not induce additional load on semantic processing. These evidence demonstrates that, in Japanese language processing, the difficultness of semantic processing could influence the difficultness of syntactic processing, while the difficultness of syntactic processing would not influence the difficultness of semantic processing. Our findings are suggestive of the possibility that in Japanese language reading, semantic processing precedes syntactic processing, or semantic processing and syntactic processing are in parallel.

Effects of Syntactic Distance and Word Order on Language Processing: An Investigation Based on a Psycholinguistic Treebank of English

We conducted a broad-coverage investigation of the effects of syntactic distance and word order on language processing against a dependency-annotated reading time corpus of English. A combined method of quantitative syntax and psycholinguistic analyses was adopted to yield converging evidence. It was found that (i) head-initial structures allow greater structural complexity, i.e., larger head-dependent distance, than head-final structures in both language comprehension and production; (ii) within the capacity limit of working memory, syntactic distance is a positive predictor of reading time for a word with a preceding head, whereas a negative predictor of reading time for a word with a following head; and (iii) at the sentence level, syntactic distance is a significant predictor of sentence reading time. These results suggest that (i) different word orders may enjoy different processing mechanisms in terms of cognitive difficulty and processes, which can be explained by an incremental language parser; and (ii) in addition to distance, word order should also be considered as a factor affecting language processing, which is an important extension to distance-based language processing models. Taken as a whole, our study paves the way for corpus-based integration of quantitative linguistic and psycholinguistic methods into understanding language processing and its underlying cognitive mechanisms.

The posterior middle temporal gyrus serves as a hub in syntactic comprehension: A model on the syntactic neural network

Neuroimaging studies have revealed a distributed neural network involving multiple fronto-temporal regions that are active during syntactic processing. Here, we investigated how these regions work collaboratively to support syntactic comprehension by examining the behavioral relevance of the global functional integration of the syntax network (SN). We found that individuals with a stronger resting-state within-network integration in the left posterior middle temporal gyrus (lpMTG) were better at syntactic comprehension. Furthermore, the pair-wise functional connectivity between the lpMTG and the Broca's area, the middle frontal gyrus, and the angular and supramarginal gyri was positively correlated with participants' syntactic processing ability. In short, our study reveals the behavioral significance of intrinsic functional integration of the SN in syntactic comprehension, and provides empirical evidence for the hub-like role of the lpMTG. We proposed a neural model for syntactic comprehension highlighting the hub of the SN and its interactions with other regions in the network.

Musical Garden Paths: Evidence for Syntactic Revision Beyond the Linguistic Domain

While theoretical and empirical insights suggest that the capacity to represent and process complex syntax is crucial in language as well as other domains, it is still unclear whether specific parsing mechanisms are also shared across domains. Focusing on the musical domain, we developed a novel behavioral paradigm to investigate whether a phenomenon of syntactic revision occurs in the processing of tonal melodies under analogous conditions as in language. We present the first proof-of-existence for syntactic revision in a set of tonally ambiguous melodies, supporting the relevance of syntactic representations and parsing with language-like characteristics in a nonlinguistic domain. Furthermore, we find no evidence for a modulatory effect of musical training, suggesting that a general cognitive capacity, rather than explicit knowledge and strategies, may underlie the observed phenomenon in music.

Frequency tagging of syntactic structure or lexical properties; a registered MEG study

A traditional view on sentence comprehension holds that the listener parses linguistic input using hierarchical syntactic rules. Recently, physiological evidence for such a claim has been provided by Ding et al.'s (2016) MEG study that demonstrated, using a frequency-tagging paradigm, that regularly occurring syntactic constituents were spontaneously tracked by listeners. Even more recently, this study's results have been challenged as artifactual by Frank and Yang (2018) who successfully re-created Ding's results using a distributional semantic vector model that relied exclusively on lexical information and did not appeal to any hierarchical syntactic representations. The current MEG study was designed to dissociate the two interpretations of Ding et al.'s results. Taking advantage of the morphological richness of Russian, we constructed two types of sentences of different syntactic structure; critically, this was achieved by manipulating a single affix on one of the words while all other lexical roots and affixes in the sentence were kept the same. In Experiment 1, we successfully verified the intuition that due to almost complete lexical overlap the two types of sentences should yield the same activity pattern according to Frank and Yang's (2018) lexico-semantic model. In Experiment 2, we recorded Russian listeners' MEG activity while they listened to the two types of sentences. Contradicting the hierarchical syntactic account and consistent with the lexico-semantic one, we observed no difference across the conditions in the way participants tracked the stimuli properties. Corroborated by other recent evidence, our findings show that peaks interpreted by Ding et al. as reflecting higher-level syntactic constituency may stem from non-syntactic factors.

Processing cataphors: Active antecedent search is persistent

Cataphors precede their antecedents, so they cannot be fully interpreted until those antecedents are encountered. Some researchers propose that cataphors trigger an active search during incremental processing in which the parser predictively posits potential antecedents in upcoming syntactic positions (Kazanina et al., Journal of Memory and Language, 56[3], 384-409, 2007). One characteristic of active search is that it is persistent: If a prediction is disconfirmed in an earlier position, the parser should iteratively search later positions until the predicted element is found. Previous research has assumed, but not established, that antecedent search is persistent. In four experiments in English and Norwegian, we test this hypothesis. Two sentence completion experiments show a strong off-line preference for coreference between a fronted cataphor and the first available argument position (the main subject). When the main subject cannot be the antecedent, participants posit the antecedent in the next closest position: object position. Two self-paced reading studies demonstrate that comprehenders actively expect the antecedent of a fronted cataphor to appear in the main clause subject position, and then successively in object position if the subject does not match the cataphor in gender. Our results therefore support the claim that antecedent search is active and persistent.

When politeness processing encounters failed syntactic/semantic processing

Previous studies have elucidated the neural mechanism of syntactic/semantic processing and pragmatic processing. However, the exact mechanisms by which these two aspects of processing interact during language comprehension remain unknown. In this event-related brain potential study, we examined the interaction between politeness processing and local syntactic/semantic processing of a phrase. We used a full factorial design that crossed politeness consistency with local syntactic/semantic coherence. Politeness violations elicited a P200 effect in the 190-320 ms range, centro-parietally distributed positivity in the 360-866 ms range, and pure local syntactic/semantic violation elicited a broad distributed positivity in the 362-868 ms range. Crucially, we found that event-related potential responses elicited by combined politeness and syntactic/semantic violations resemble those elicited by separate syntactic/semantic violations. These results indicated that local syntactic/semantic processing has a functional primacy over politeness processing. Furthermore, our results support the blocking hypothesis from a politeness processing perspective instead of the independent hypothesis.

Filling the gap in gap-filling: Long-distance dependency formation in sentence production

In a sentence like Who does the artist think chased the chef?, the who at the beginning depends on the last bit of the sentence, chased the chef. This is an instance of a long-distance dependency. What is the nature of the cognitive process that allows speakers to produce sentences that include distant elements that form dependencies? In four experiments, speakers described drawings that elicited long-distance dependencies. Critically, speakers were sometimes primed to produce a that in sentences where that was ungrammatical due to a grammatical constraint known as the that-trace constraint (e.g.,*Who does the artist think that chased the chef). Results showed that, when primed to say an ungrammatical that, speakers were slower to start to speak. Because the that-trace constraint applies selectively to certain configurations of long-distance dependencies, this suggests that the grammatical details of the long-distance dependency are already planned before speakers start to speak the sentences involving long-distance dependencies. I propose a formal model that explains how speakers plan long-distance dependencies in advance of speaking them while also managing the cognitive pressure to speak sentences incrementally.

Syntax, morphosyntax, and serial recall: How language supports short-term memory

In the classic view of verbal short-term memory, immediate recall is achieved by maintaining phonological representations, while the influence of other linguistic information is negligible. According to language-based accounts, short-term retention of verbal material is inherently bound to language production and comprehension, thus also influenced by semantic or syntactic factors. In line with this, serial recall is better when lists are presented in a canonical word order for English rather than in a noncanonical order (e.g., when adjectives precede nouns rather than vice versa; Perham et al., 2009, Quarterly Journal of Experimental Psychology, 62[7], 1285–1293). However, in many languages, grammaticality is not exclusively determined by word order. In German, an adjective–noun sequence is grammatical only if the adjective is inflected in congruence with the noun’s person, number, and grammatical gender. Therefore, we investigated whether similar effects of syntactic word order occur in German. In two modified replications of Perham et al.’s study, we presented lists of three pairs of adjectives and nouns, presented in adjective–noun or in noun–adjective order. In addition, we manipulated morphosyntactic congruence between nouns and adjectives within pairs (Exp. 1: congruently inflected vs. uninflected adjectives; Exp. 2: congruently inflected vs. incongruently inflected adjectives). Both experiments show an interaction: Word order affected recall performance only when adjectives were inflected in congruence with the corresponding noun. These findings are in line with language-based models and indicate that, in a language that determines grammaticality in an interplay of syntactic and morphosyntactic factors, word order alone is not sufficient to improve verbal short-term memory.

Stable brain loci for the processing of complex syntax: A review of the current neuroimaging evidence

We conducted a retrospective review of fMRI studies of complex syntax, in order to study the stability of the neural bases of mechanisms engaged in syntactic processing. Our review set out rigorous selection criteria of studies which we discuss, including transparency and minimality of the contrasts between stimuli, and the presence of whole brain analyses corrected for multiple comparisons. Seventeen studies with 316 participants survived our sieve. We mapped the 65 resulting maxima onto JuBrain, a state-of-the-art cytoarchitectonic brain atlas (Amunts et al., 2020), and a sharp picture emerged: syntactic displacement operations (a k a MOVE) produce highly consistent results, activating left Broca's region across-the-board and unambiguously; to a somewhat lesser extent, maxima clustered in left posterior brain regions, including the STS/STG. The few studies of syntactic tree-building operations (a k a MERGE) produce a murkier picture regarding the involvement of the left IFG. We conclude that the extant data decisively point to the JuBrain-defined Broca's region as the main locus of complex receptive syntax in healthy people; the STS/STG also are involved, but to a lesser extent.

Mechanisms for handling nested dependencies in neural-network language models and humans

Recursive processing in sentence comprehension is considered a hallmark of human linguistic abilities. However, its underlying neural mechanisms remain largely unknown. We studied whether a modern artificial neural network trained with "deep learning" methods mimics a central aspect of human sentence processing, namely the storing of grammatical number and gender information in working memory and its use in long-distance agreement (e.g., capturing the correct number agreement between subject and verb when they are separated by other phrases). Although the network, a recurrent architecture with Long Short-Term Memory units, was solely trained to predict the next word in a large corpus, analysis showed the emergence of a very sparse set of specialized units that successfully handled local and long-distance syntactic agreement for grammatical number. However, the simulations also showed that this mechanism does not support full recursion and fails with some long-range embedded dependencies. We tested the model's predictions in a behavioral experiment where humans detected violations in number agreement in sentences with systematic variations in the singular/plural status of multiple nouns, with or without embedding. Human and model error patterns were remarkably similar, showing that the model echoes various effects observed in human data. However, a key difference was that, with embedded long-range dependencies, humans remained above chance level, while the model's systematic errors brought it below chance. Overall, our study shows that exploring the ways in which modern artificial neural networks process sentences leads to precise and testable hypotheses about human linguistic performance.

The hunt for structure-dependent interpretation: The case of Principle C

Jacques Mehler's earliest work concerned the independence of syntactic and semantic representations in adult sentence understanding, probing for independent contributions of sentence structure and sentence meaning in the psychological processes that underlie linguistic perception (e.g., Mehler, 1963; Mehler & Miller, 1964). The bulk of his career was spent pioneering the study of infants' linguistic cognition. In this paper, we bring these two streams together, using data from a suite of infant looking tasks to probe the syntactic representations that underlie sentence understanding for 30-month-olds. Each participant completed a battery of 3 tasks: one measuring knowledge of Principle C, one measuring lexical access speed and one measuring syntactic processing. We find that variability in performance on a Principle C task is predicted by variability in vocabulary, but not by either lexical access speed or a new measure of syntactic integration. Successful deployment of Principle C in 30-month-olds may therefore depend on factors related to vocabulary, but distinct from either lexical access or structure building. Identification of such factors remains an important goal for future work.

Jacques Mehler's early psycholinguistic days in Paris

This article first describes Jacques Mehler's initial efforts to make psycholinguistics and, more generally, the cognitive sciences better known during his first years in Paris. Two lines of research on sentence perception, that we conducted in collaboration with Jacques, are then presented to illustrate his focus. In the Seventies, sentence perception was a central topic in psycholinguistics, with contrasting proposals of syntactic autonomy and interactivity being confronted. A first series of experiments aimed at defining the role of syntax in lexical selection process as revealed by the rapid serial visual presentation (RSVP) of the words in a sentence. The second series, using the phoneme monitoring technique, examined the clause as a processing unit during the auditory perception of sentences. These results confirm the fundamental role played by syntax in language processing.

Reduced right-hemisphere ERP P600 grammaticality effect is associated with greater right-hemisphere inhibition: Evidence from right-handers with familial sinistrality

The present study examined the hypothesis that left hemisphere (LH) equivalent language capabilities in the right hemisphere (RH) are inhibited in neurologically intact individuals by testing healthy young right-handers with a history of familial sinistrality (FS+, i.e. with at least one left handed biological relative), a population documented to show greater variability for RH language processing. Event-Related Potential (ERP) and split visual field presentation techniques were combined to assess LH- and RH- biased responses to syntactic category violations. In addition, a bilateral flanker task was used to measure inter-hemispheric inhibition ability in the same set of participants. Replicating prior findings, in addition to the LH-biased P600 grammaticality effect previously seen for right-handers in general, a fair amount, though not all, of FS + right-handers showed RH-biased P600 responses, leading to a reliable RH P600 grammaticality effect at the group level. Capitalizing on the variability of RH P600 responses, our results further revealed that reduced RH-biased P600 effects were reliably correlated with more effective RH inhibition (indexed by smaller reaction time differences between incongruent and neutral flankers presented to the RH via the left visual field). These results corroborated previous findings that the RH is capable of processing syntactic information in a manner qualitatively similar to that in the LH and further demonstrated that LH-equivalent processing in the RH as indexed by the P600 responses is modulated by RH inhibition, contributing to inter-individual variability in syntactic lateralization.

The oscillatory mechanisms associated with syntactic binding in healthy ageing

Older adults frequently display differential patterns of brain activity compared to young adults in the same task, alongside widespread neuroanatomical changes. Differing functional activity patterns in older adults are commonly interpreted as being compensatory (e.g., Cabeza et al., 2002). We examined the oscillatory activity in the EEG during syntactic binding in young and older adults, as well as the relationship between oscillatory activity and behavioural performance on a syntactic judgement task within the older adults. 19 young and 41 older adults listened to two-word sentences that differentially load onto morpho-syntactic binding: correct syntactic binding (morpho-syntactically correct, e.g., "I dotch"); incorrect syntactic binding (morpho-syntactic agreement violation, e.g., "they dotches") and no syntactic binding (minimizing morpho-syntactic binding, e.g., "dotches spuff"). Behavioural performance, assessed in a syntactic judgement task, was characterized by inter-individual variability especially in older adults, with accuracy ranging from 76 to 100% in young adults and 58-100% in older adults. Compared to young adults, older adults were slower, but not less accurate. Functional neural signatures for syntactic binding were assessed as the difference in oscillatory power between the correct and no syntactic binding condition. In older adults, syntactic binding was associated with a smaller increase in theta (4-7 Hz), alpha (8-12 Hz) and beta (15-20 Hz) power in a time window surrounding the second word. There was a significant difference between the older and young adults: in the alpha range, the condition difference seemed to be in the opposite direction for older versus young adults. Our findings thus suggest that the neural signature associated with syntactic binding in older adults is different from young adults. However, we found no evidence of a significant association between behavioural performance and the neural signatures of syntactic binding for older adults, which does not readily support the predictions of compensatory models of language and ageing.

Mind the stimulation site: Enhancing and diminishing sentence comprehension with anodal tDCS

In a previous sham-controlled study, we showed the feasibility of increasing language comprehension in healthy participants by applying anodal transcranial direct current stimulation (atDCS) over the left inferior frontal gyrus (LIFG). In the present work, we present a follow-up experiment targeting with atDCS the left inferior parietal cortex (LIPC) while participants performed the same auditory comprehension task used in our previous experiment. Both neural sites (LIFG and LIPC) are crucial hubs of Baddeley's model of verbal short-term memory (vSTM). AtDCS over LIPC decreased accuracy as compared to sham and LIFG stimulation, suggesting the involvement of this area in sentence comprehension. Crucially, our results highlighted that applying tDCS over different hubs of the same neural network can lead to opposite behavioural results, with relevant implications from a clinical perspective.

Effects of reader's facial expression on syntactic processing: A brain potential study

Embodied views of language support that facial sensorimotor information can modulate language comprehension. The aim of this study is to test whether the syntactic processing of simple sentences, as measured with event-related brain potentials (ERP), could be affected by reader's facial expressions. Participants performed a correctness decision task using sentences that could be either correct (50%) or contain a morphosyntactic disagreement (either in gender or number), while making one of four facial expressions: participants either (a) posed no facial expression ("control" condition) (b) brought their eyebrows together, making the ends of two golf tees touch ("frown" condition), (c) held a pencil with their teeth ("smile" condition), or (d) held the pencil using their lips ("non-smile" condition). In all conditions the customary left anterior negativities did not appear. In contrast, an N400-like component emerged, which was larger for the "frown" condition and reduced in the "smile" and "non-smile" conditions. These results can be interpreted as the consequence of either an unconscious emotion induction or an interplay between the motor and the language systems subsequent to the effort needed to hold the facial expression.

How readers process syntactic input depends on their goals

During reading, the recognition of words is influenced by the syntactic compatibility of surrounding words: a sentence-superiority effect. However, when the goal is to make syntactic categorization decisions about single target words, these decisions are influenced by the syntactic congruency rather than compatibility of surrounding words. Although both these premises imply that readers can extract syntactic information from multiple words in parallel, they also suggest that how the brain organizes syntactic input-and consequently how surrounding stimuli affect word recognition-depends on the reader's top-down goals. The present study provides a direct test of this conception. Participants were offered nouns and verbs amidst a grammatical context ('this horse fell') and ungrammatical context ('fell horse this'). Using a conditional task setup, we manipulated the amount of emphasis put on respectively sentences and single words. In two blocks readers were instructed to make sentence grammaticality judgments only if the middle word was respectively noun or verb; in two other blocks readers were instructed to syntactically categorize the middle word only if the sentence was respectively correct or incorrect. We established an interaction effect whereby the impact of grammatical correctness on syntactic categorization decisions was greater than the effect of grammatical correctness per se. This first sentence-superiority effect in the categorization of single words, combined with the absence of this effect in prior flanker studies, leads us to surmise that word-to-word syntactic constraints only operate if the reader is engaged in sentence processing.

Poor working memory performance in healthy elderly adults with electroencephalographic risk of cognitive decline affects syntactic processing

OBJECTIVE

To examine the effects of working memory (WM) load and gender agreement on sentence processing as a function of the electroencephalographic risk (i.e., abnormally high values of theta absolute power) of cognitive decline in older adults.

METHODS

Event-related potentials (ERPs) were collected from Spanish speakers (22 older adults belonged to the Risk group, mean age = 67.7 years; 22 older adults belonged to the Control group, mean age = 65.2 years) while reading sentences to detect grammatical errors. Sentences varied with regard to (1) the gender agreement of the noun and adjective, where gender of the adjective either agreed or disagreed with the noun, and (2) WM load (i.e., the number of words between the noun and adjective in the sentence).

RESULTS

The Risk group showed a lower percentage of correct answers and longer reaction times than the Control group. The Risk group also showed a different pattern of ERP components, which was characterized by smaller amplitude and longer latency of the P600a component under high WM load conditions.

CONCLUSION

The findings suggest that the Risk group shows difficulties integrating information associated with the previous sentence context.

SIGNIFICANCE

The electroencephalographic risk factor of cognitive decline might be not only a predictor of but also an indicator of current decline.

In dialogue with an avatar, language behavior is identical to dialogue with a human partner

The use of virtual reality (VR) as a methodological tool is becoming increasingly popular in behavioral research as its flexibility allows for a wide range of applications. This new method has not been as widely accepted in the field of psycholinguistics, however, possibly due to the assumption that language processing during human-computer interactions does not accurately reflect human-human interactions. Yet at the same time there is a growing need to study human-human language interactions in a tightly controlled context, which has not been possible using existing methods. VR, however, offers experimental control over parameters that cannot be (as finely) controlled in the real world. As such, in this study we aim to show that human-computer language interaction is comparable to human-human language interaction in virtual reality. In the current study we compare participants' language behavior in a syntactic priming task with human versus computer partners: we used a human partner, a human-like avatar with human-like facial expressions and verbal behavior, and a computer-like avatar which had this humanness removed. As predicted, our study shows comparable priming effects between the human and human-like avatar suggesting that participants attributed human-like agency to the human-like avatar. Indeed, when interacting with the computer-like avatar, the priming effect was significantly decreased. This suggests that when interacting with a human-like avatar, sentence processing is comparable to interacting with a human partner. Our study therefore shows that VR is a valid platform for conducting language research and studying dialogue interactions in an ecologically valid manner.

The role of nondeclarative memory in the skill for language: Evidence from syntactic priming in patients with amnesia

Syntactic priming, the phenomenon in which participants adopt the linguistic behaviour of their partner, is widely used in psycholinguistics to investigate syntactic operations. Although the phenomenon of syntactic priming is well documented, the memory system that supports the retention of this syntactic information long enough to influence future utterances, is not as widely investigated. We aim to shed light on this issue by assessing patients with Korsakoff's amnesia on an active-passive syntactic priming task and compare their performance to controls matched in age, education, and premorbid intelligence. Patients with Korsakoff's syndrome display deficits in all subdomains of declarative memory, yet their nondeclarative memory remains intact, making them an ideal patient group to determine which memory system supports syntactic priming. In line with the hypothesis that syntactic priming relies on nondeclarative memory, the patient group shows strong priming tendencies (12.6% passive structure repetition). Our healthy control group did not show a priming tendency, presumably due to cognitive interference between declarative and nondeclarative memory. We discuss the results in relation to amnesia, aging, and compensatory mechanisms.

P600 alteration of syntactic language processing in patients with bipolar mania: Comparison to schizophrenic patients and healthy subjects

BACKGROUND

Disturbances in thought, speech, and linguistic processing are frequently observed in bipolar manic patients, but the underlying neurophysiological mechanisms are not well understood. P600 is a distinct, positive event-related potential component elicited by syntactic violations. Using the P600 ERP, we examined neural processing of syntactic language comprehension in patients with bipolar mania compared to patients with schizophrenia and healthy people.

METHOD

P600s were recorded from 21 manic patients with bipolar disorder, 26 patients with schizophrenia, and 29 healthy subjects during the presentation of 120 auditory sentences with syntactic violations or non-violations. Subjects were asked to judge whether each sentence was correct or incorrect.

RESULTS

Patients with mania and schizophrenia had significantly smaller P600 amplitudes associated with syntactic violations compared with healthy subjects. There was no difference in P600 amplitude between patient groups. For behavioral performance, patients with schizophrenia had significantly less accurate rates and longer reaction times compared with healthy subjects, whereas manic patients exhibited no significant differences in accuracy and only showed increased reaction times in comparison with healthy subjects.

LIMITATIONS

Psychotropic drug usage and small sample size.

CONCLUSION

Patients with bipolar mania have reduced P600 amplitude, comparable to patients with schizophrenia. Our findings may represent the first neurophysiological evidence of abnormal syntactic linguistic processing in bipolar mania.

ERP evidence for on-line syntactic computations in 2-year-olds

Syntax allows human beings to build an infinite number of sentences from a finite number of words. How this unique, productive power of human language unfolds over the course of language development is still hotly debated. When they listen to sentences comprising newly-learned words, do children generalize from their knowledge of the legal combinations of word categories or do they instead rely on strings of words stored in memory to detect syntactic errors? Using novel words taught in the lab, we recorded Evoked Response Potentials (ERPs) in two-year-olds and adults listening to grammatical and ungrammatical sentences containing syntactic contexts that had not been used during training. In toddlers, the ungrammatical use of words, even when they have been just learned, induced an early left anterior negativity (surfacing 100-400ms after target word onset) followed by a late posterior positivity (surfacing 700-900ms after target word onset) that was not observed in grammatical sentences. This late effect was remarkably similar to the P600 displayed by adults, suggesting that toddlers and adults perform similar syntactic computations. Our results thus show that toddlers build on-line expectations regarding the syntactic category of upcoming words in a sentence.

Syntactic processing is distributed across the language system

Language comprehension recruits an extended set of regions in the human brain. Is syntactic processing localized to a particular region or regions within this system, or is it distributed across the entire ensemble of brain regions that support high-level linguistic processing? Evidence from aphasic patients is more consistent with the latter possibility: damage to many different language regions and to white-matter tracts connecting them has been shown to lead to similar syntactic comprehension deficits. However, brain imaging investigations of syntactic processing continue to focus on particular regions within the language system, often parts of Broca's area and regions in the posterior temporal cortex. We hypothesized that, whereas the entire language system is in fact sensitive to syntactic complexity, the effects in some regions may be difficult to detect because of the overall lower response to language stimuli. Using an individual-subjects approach to localizing the language system, shown in prior work to be more sensitive than traditional group analyses, we indeed find responses to syntactic complexity throughout this system, consistent with the findings from the neuropsychological patient literature. We speculate that such distributed nature of syntactic processing could perhaps imply that syntax is inseparable from other aspects of language comprehension (e.g., lexico-semantic processing), in line with current linguistic and psycholinguistic theories and evidence. Neuroimaging investigations of syntactic processing thus need to expand their scope to include the entire system of high-level language processing regions in order to fully understand how syntax is instantiated in the human brain.

Self-Guided Reading: Touch-Based Measures of Syntactic Processing

A novel online reading methodology termed Self-Guided Reading (SGR) is examined to determine if it can successfully detect well-studied syntactic processing behaviours. In SGR, a participant runs their finger under masked text in order to reveal a sentence. It is therefore similar to self-paced reading in presentation of stimuli, but different in the motion that the participant makes to interact with the stimuli. The phenomena of relative clause, adverb and noun phrase/sentential attachment are utilised to allow comparison to previous research that employed self-paced reading and eye-tracking. SGR was able to detect the predicted processing behaviours in all sentence types. Moreover, once design choices and task effects are accounted for, SGR was the most consistent in triggering a motor movement change at the predicted point in the sentence. Able to provide a semi-continuous reading measure at low cost, SGR should be investigated further to uncover the full potential of the method for psycholinguistic research.

The interplay between referential processing and local syntactic/semantic processing: ERPs to written Chinese discourse

Two event-related brain potential experiments were conducted to investigate the functional interplay between discourse-level referential processing and local syntactic/semantic processing of phrases. We manipulated both the syntactic/semantic coherence of a noun phrase (NP) and the referential ambiguity of the same NP. Incoherence of the NP elicited a P600 effect in both experiments. Referential ambiguities elicited a sustained negativity (Nref) in a subset of the participants in both experiments. Crucially, among participants showing robust Nref effects to referential ambiguity in the coherent condition, Nref effects were absent when the NP was incoherent. These results provide evidence against theories in which referential processing is functionally independent of local syntactic/semantic processing of phrases. Instead, a local phrase anomaly can block aspects of referential processing concerning ambiguity.

The association between aerobic fitness and language processing in children: implications for academic achievement

Event-related brain potentials (ERPs) have been instrumental for discerning the relationship between children's aerobic fitness and aspects of cognition, yet language processing remains unexplored. ERPs linked to the processing of semantic information (the N400) and the analysis of language structure (the P600) were recorded from higher and lower aerobically fit children as they read normal sentences and those containing semantic or syntactic violations. Results revealed that higher fit children exhibited greater N400 amplitude and shorter latency across all sentence types, and a larger P600 effect for syntactic violations. Such findings suggest that higher fitness may be associated with a richer network of words and their meanings, and a greater ability to detect and/or repair syntactic errors. The current findings extend previous ERP research explicating the cognitive benefits associated with greater aerobic fitness in children and may have important implications for learning and academic performance.

Grammatical number agreement processing using the visual half-field paradigm: an event-related brain potential study

Despite indications in the split-brain and lesion literatures that the right hemisphere is capable of some syntactic analysis, few studies have investigated right hemisphere contributions to syntactic processing in people with intact brains. Here we used the visual half-field paradigm in healthy adults to examine each hemisphere's processing of correct and incorrect grammatical number agreement marked either lexically, e.g., antecedent/reflexive pronoun ("The grateful niece asked herself/*themselves…") or morphologically, e.g., subject/verb ("Industrial scientists develop/*develops…"). For reflexives, response times and accuracy of grammaticality decisions suggested similar processing regardless of visual field of presentation. In the subject/verb condition, we observed similar response times and accuracies for central and right visual field (RVF) presentations. For left visual field (LVF) presentation, response times were longer and accuracy rates were reduced relative to RVF presentation. An event-related brain potential (ERP) study using the same materials revealed similar ERP responses to the reflexive pronouns in the two visual fields, but very different ERP effects to the subject/verb violations. For lexically marked violations on reflexives, P600 was elicited by stimuli in both the LVF and RVF; for morphologically marked violations on verbs, P600 was elicited only by RVF stimuli. These data suggest that both hemispheres can process lexically marked pronoun agreement violations, and do so in a similar fashion. Morphologically marked subject/verb agreement errors, however, showed a distinct LH advantage.