A Topographical Study on the Event-related Potential Correlates of Scrambled Word Order in Japanese Complex Sentences

Electrophysiological evidence for a subject-first strategy in visually situated auditory sentence processing in Korean

This study investigated a subject-first strategy in prediction mechanism in visually situated sentence processing in Korean, using event-related potentials (ERPs). According to the subject-first strategy, parsers tend to generate sentences conforming to canonical sentence word order (i.e., SOV in Korean), subject-first sentence, mapping conceptually more prominent referent such as agent of the event on the subject position of the sentence. Therefore, in the predictive mechanism of language comprehension, the subject is pre-activated and anticipated for the first NP of the sentence at the initial phase of bottom-up language processing. This study tested this subject-first strategy in Korean by examining brain responses to object-initial sentences (OV) compared with subject-initial sentences (SV) under the context of clear thematic role relations set by a visual image. The results of an ERP experiment with 30 native Korean speakers identified neural effects for object-initial sentences compared with subject-initial sentences at the NP and Verb, reflecting a conflict between the pre-activated representation in the parser's mind and the encountered bottom-up input. An N400 effect was elicited at the NP, as early as at the noun, not at the following object case marker. Late frontal positivity (LFP) was also found in the sentence-final verb, proving the processing difficulty of non-canonical object-initial sentences compared with canonical subject-initial sentences. These results indicate that Korean native speakers build linguistic representation conforming to a canonical sentence in SOV language in the predictive mechanism supporting subject-first strategy but revise the predicted event structure rapidly upon newly encountering input.

Neural correlates of thematic role assignment for passives in Standard Indonesian

Previous studies of multiple languages have found processing differences between patient-first and agent-first word orders. However, the results are inconsistent as they do not identify a specific ERP component as a unique correlate of thematic role processing. Furthermore, these studies generally confound word order with frequency, as patient-first structures tend to be infrequent in the languages that have been investigated. There is evidence that frequency at the sentence level plays a significant role in language processing. To address this potential confounding variable, we will test a language where the non-canonical sentences are more frequent and are comparable to the canonical sentences, namely Standard Indonesian. In this language, there is evidence from acquisition, corpus, and clinical data indicates that the use of passive is frequent and salient. One instance of this difference can be demonstrated by the fact that it has been suggested that frequency may be the reason why Indonesian-speaking aphasic speakers do not have impairments in the comprehension of passives, whereas speakers of other languages with aphasia often do. In the present study, we will test 50 native speakers of Indonesian using 100 sentences (50 active and 50 passive sentences). If the neural correlates of thematic role processing are not observed in the critical region of the sentence (the prefix of the verb), this would suggest that the previous results were indeed influenced by frequency, but if we find that specific ERPs are connected to the hypothesized syntactic operations, this would further reinforce the existing evidence of the increased cognitive load required to process more syntactically complicated sentences.

Towards Understanding Sustained Neural Activity Across Syntactic Dependencies

Sustained anterior negativities have been the focus of much neurolinguistics research concerned with the language-memory interface, but what neural computations do they actually reflect? During the comprehension of sentences with long-distance dependencies between elements (such as object wh-questions), prior event-related potential work has demonstrated sustained anterior negativities (SANs) across the dependency region. SANs have been traditionally interpreted as an index of working memory resources responsible for storing the first element (e.g., wh-phrase) until the second element (e.g., verb) is encountered and the two can be integrated. However, it is also known that humans pursue top-down approaches in processing long-distance dependencies-predicting units and structures before actually encountering them. This study tests the hypothesis that SANs are a more general neural index of syntactic prediction. Across three experiments, we evaluated SANs in traditional wh-dependency contrasts, but also in sentences in which subordinating adverbials (e.g., although) trigger a prediction for a second clause, compared to temporal adverbials (e.g., today) that do not. We find no SAN associated with subordinating adverbials, contra the syntactic prediction hypothesis. More surprisingly, we observe SANs across matrix questions but not embedded questions. Since both involved identical long-distance dependencies, these results are also inconsistent with the traditional syntactic working memory account of the SAN. We suggest that a more general hypothesis that sustained neural activity supports working memory can be maintained, however, if the sustained anterior negativity reflects working memory encoding at the non-linguistic discourse representation level, rather than at the sentence level.

Semantic reversal anomalies under the microscope: Task and modality influences on language-associated event-related potentials

Semantic reversal anomalies (SRAs)-sentences where an implausibility is created by reversing participant roles-have attracted much attention in the literature on the electrophysiology of language. In spite of being syntactically well formed but semantically implausible, these sentences unexpectedly elicited a monophasic P600 effect in English and Dutch rather than an N400 effect. Subsequent research revealed variability in the presence/absence of an N400 effect to SRAs depending on the language examined and the choice of verb type in English. However, most previous studies employed the same presentation modality (visual) and task (acceptability judgement). Here, we conducted two experiments and three statistical analyses to investigate the influence of stimulus modality, task demand and statistical choices on event-related potential (ERP) response patterns to SRAs in English. We reproduced a previous study's procedure and analysis (N. Bourguignon et al. (2012) Brain and Language, 122, 179-189) and further introduced between-subjects factors of task type and modality, using mixed-effects modelling to analyse the data. We observed an N400 effect to typical English SRAs (agent subject verbs, e.g. "the fries will eat the boys"), which contrasts existing literature and was not predicted by existing theories that account for SRA processing. Task demand modulated the ERPs elicited by SRAs, while auditory presentation led to increased comprehension accuracy and a more broadly distributed ERP. Finally, the statistical methods used influenced the presence/absence of ERP effects. Our results suggest a sensitivity of language-related ERP patterns to methodological parameters, and we conclude that future experiments should take this into careful consideration.

Neural architecture of human language: Hierarchical structure building is independent from working memory

Using functional magnetic resonance imaging (fMRI), we show that the neural substrate of language does not overlap with that for verbal working memory when we carefully define verbal working memory in sentence processing. Object-Subject-Verb (OSV) sentences in Japanese were contrasted with canonical Subject-Object-Verb (SOV) sentences, which had less hierarchy in linguistic structure. This contrast revealed the posterior part of Broca's area and the left posterior middle temporal gyrus (pMTG) as the neural bases for hierarchical structure building. Furthermore, we changed verbal working memory load in OSV sentences by adding modifiers to the subject or object noun phrases; this resulted in the activation in the op9, which is situated in the frontal operculum and is adjacent to, but not situated in, Broca's area. The neuroanatomical segregation of language processing from verbal working memory suggests independence of the faculty of language from the verbal working memory system, providing evidence for the domain-specificity of language in human cognition.

Negative Transfer Effects on L2 Word Order Processing

Does first language (L1) word order affect the processing of non-canonical but grammatical syntactic structures in second language (L2) comprehension? In the present study, we test whether L1-Spanish speakers of L2-Basque process subject-verb-object (SVO) and object-verb-subject (OVS) non-canonical word order sentences of Basque in the same way as Basque native speakers. Crucially, while OVS orders are non-canonical in both Spanish and Basque, SVO is non-canonical in Basque but is the canonical word order in Spanish. Our electrophysiological results showed that the characteristics of L1 affect the processing of the L2 even at highly proficient and early-acquired bilingual populations. Specifically, in the non-native group, we observed a left anterior negativity-like component when comparing S and O at sentence initial position and a P600 when comparing those elements at sentence final position. Those results are similar of those reported by Casado et al. (2005) for native speakers of Spanish indicating that L2-Basque speakers rely in their L1-Spanish when processing SVO-OVS word order sentences. Our results favored the competition model (MacWhinney, 1997).

Native and Non-native Speakers' Brain Responses to Filled Indirect Object Gaps

We examined native and non-native English speakers' processing of indirect object wh-dependencies using a filled-gap paradigm while recording event-related potentials (ERPs). The non-native group was comprised of native German-speaking, proficient non-native speakers of English. Both participant groups showed evidence of linking fronted indirect objects to the subcategorizing verb when this was encountered, reflected in an N400 component. Evidence for continued filler activation beyond the verb was seen only in the non-native group, in the shape of a prolonged left-anterior negativity. Both participant groups showed sensitivity to filled indirect object gaps reflected in a P600 response, which was more pronounced and more globally distributed in our non-native group. Taken together, our results indicate that resolving indirect object dependencies is a two-step process in both native and non-native sentence comprehension, with greater processing cost incurred in non-native compared to native comprehension.

Interaction Between Syntactic Structure and Information Structure in the Processing of a Head-Final Language

The effects of syntactic and information structures on sentence processing load were investigated using two reading comprehension experiments in Japanese, a head-final SOV language. In the first experiment, we discovered the main effects of syntactic and information structures, as well as their interaction, showing that interaction of these two factors is not restricted to head-initial languages. The second experiment revealed that the interaction between syntactic structure and information structure occurs at the second NP (O of SOV and S of OSV), which, crucially, is a pre-head position, suggesting the incremental nature of the processing of both syntactic structure and information structure in head-final languages.

Greater Left Inferior Frontal Activation for SVO than VOS during Sentence Comprehension in Kaqchikel

Cortical activations during the processing of Kaqchikel transitive sentences with canonical and non-canonical word orders were investigated using functional magnetic resonance imaging. Kaqchikel is an endangered Mayan language spoken in Guatemala. The word order in this language is relatively flexible. We observed higher cortical activations in the left inferior frontal gyrus for sentences with the subject-verb-object (SVO) word order, as compared to sentences with the verb-object-subject (VOS) word order, suggesting that Kaqchikel sentences are easier to process when they have the VOS order than when they have the SVO order. This supports the traditional analysis of Mayan word order: the syntactically simplest word order of transitive sentences in Mayan languages, including Kaqchikel, is VOS. More importantly, the results revealed that the subject-before-object word order preference in sentence comprehension, previously observed in other languages, might not reflect a universal aspect of human languages. Rather, processing preference may be language-specific to some extent, reflecting syntactic differences in individual languages.

Incremental Sentence Processing in Japanese: A Maze Investigation into Scrambled and Control Sentences

This study investigates preverbal structural and semantic processing in Japanese, a head-final language, using the maze task. Two sentence types were tested-simple scrambled sentences (Experiment 1) and control sentences (Experiment 2). Experiment 1 showed that even for simple, mono-clausal Japanese sentences, (1) there are online processing costs associated with parsing noncanonical word orders and (2) these costs are incurred during the incremental integration of constituents into developing sentence representations. Experiment 2 indicated (1) that antecedents are provisionally assigned to empty subjects in Japanese control sentences before verb information becomes available and (2) that this process is guided by an object control bias. Taken together, these findings are interpreted to suggest an important role for preverbal analysis in the processing of displaced constituents and of referential properties for empty elements in head-final languages.

Age-related changes in sentence production abilities and their relation to working-memory capacity: evidence from a verb-final language

Objectives

This study investigated the best predictor to capture age-related changes in passive-sentence production using a constrained sentence-production paradigm and explored the role of working-memory capacity in relation to the task demands of the sentence-production tasks.

Methods

A total of 60 participants participated in the study ranging in age from 21 to 86. All were administered a syntactic-priming and a sentence-completion task under either canonical or noncanonical word-order conditions.

Results

Age was significantly and negatively correlated with sentence-production tasks, and the most demanding condition with a noncanonical word order under the syntactic priming paradigm was the best predictor of aging. Working-memory capacity was significantly and positively correlated with all conditions, but the significant correlation remained only for the most demanding condition (the priming task with a noncanonical word order) after controlling for age.

Discussion

Sentence-production abilities were vulnerable to aging, and these effects manifested most clearly when the task demands were high enough to tax individuals’ cognitive capacity. Working-memory capacity partially accounted for age-related changes in sentence-production abilities.

Word order processing in a second language: from VO to OV

Event-related potential studies on second language processing reveal that L1/L2 differences are due either to proficiency, age of acquisition or grammatical differences between L1 and L2 (Kotz in Brain Lang 109(2-3):68-74, 2009). However, the relative impact of these and other factors in second language processing is still not well understood. Here we present evidence from behavioral and ERP experiments on Basque sentence word order processing by L1Spanish-L2Basque early bilinguals (Age of Aquisition [Formula: see text] 3 years) with very high proficiency in their L2. Results reveal that these L2 speakers have a preference towards canonical Subject-Object-Verb word order, which they processed faster and with greater ease than non-canonical Object-Subject-Verb. This result converges with the processing preferences shown by natives and reported in Erdocia et al. (Brain Lang 109(1):1-17, 2009). However, electrophysiological measures associated to canonical (SOV) and non-canonical (OSV) sentences revealed a different pattern in the non-natives, as compared to that reported previously for natives. The non-native group elicited a P600 component that native group did not show when comparing S and O at sentence's second position. This pattern of results suggests that, despite high proficiency, non-native language processing recruits neural resources that are different from those employed in native languages.

Information structure influences depth of syntactic processing: event-related potential evidence for the Chomsky illusion

Information structure facilitates communication between interlocutors by highlighting relevant information. It has previously been shown that information structure modulates the depth of semantic processing. Here we used event-related potentials to investigate whether information structure can modulate the depth of syntactic processing. In question-answer pairs, subtle (number agreement) or salient (phrase structure) syntactic violations were placed either in focus or out of focus through information structure marking. P600 effects to these violations reflect the depth of syntactic processing. For subtle violations, a P600 effect was observed in the focus condition, but not in the non-focus condition. For salient violations, comparable P600 effects were found in both conditions. These results indicate that information structure can modulate the depth of syntactic processing, but that this effect depends on the salience of the information. When subtle violations are not in focus, they are processed less elaborately. We label this phenomenon the Chomsky illusion.

Prominence vs. aboutness in sequencing: a functional distinction within the left inferior frontal gyrus

Prior research on the neural bases of syntactic comprehension suggests that activation in the left inferior frontal gyrus (lIFG) correlates with the processing of word order variations. However, there are inconsistencies with respect to the specific subregion within the IFG that is implicated by these findings: the pars opercularis or the pars triangularis. Here, we examined the hypothesis that the dissociation between pars opercularis and pars triangularis activation may reflect functional differences between clause-medial and clause-initial word order permutations, respectively. To this end, we directly compared clause-medial and clause-initial object-before-subject orders in German in a within-participants, event-related fMRI design. Our results showed increased activation for object-initial sentences in a bilateral network of frontal, temporal and subcortical regions. Within the lIFG, posterior and inferior subregions showed only a main effect of word order, whereas more anterior and superior subregions showed effects of word order and sentence type, with higher activation for sentences with an argument in the clause-initial position. These findings are interpreted as evidence for a functional gradation of sequence processing within the left IFG: posterior subportions correlate with argument prominence-based (local) aspects of sequencing, while anterior subportions correlate with aboutness-based aspects of sequencing, which are crucial in linking the current sentence to the wider discourse. This proposal appears compatible with more general hypotheses about information processing gradients in prefrontal cortex (Koechlin & Summerfield, 2007).

Phrase length matters: the interplay between implicit prosody and syntax in Korean "garden path" sentences

In spoken language comprehension, syntactic parsing decisions interact with prosodic phrasing, which is directly affected by phrase length. Here we used ERPs to examine whether a similar effect holds for the on-line processing of written sentences during silent reading, as suggested by theories of "implicit prosody." Ambiguous Korean sentence beginnings with two distinct interpretations were manipulated by increasing the length of sentence-initial subject noun phrases (NPs). As expected, only long NPs triggered an additional prosodic boundary reflected by a closure positive shift (CPS) in ERPs. When sentence materials further downstream disambiguated the initially dispreferred interpretation, the resulting P600 component reflecting processing difficulties ("garden path" effects) was smaller in amplitude for sentences with long NPs. Interestingly, additional prosodic revisions required only for the short subject disambiguated condition-the delayed insertion of an implicit prosodic boundary after the subject NP-were reflected by a frontal P600-like positivity, which may be interpreted in terms of a delayed CPS brain response. These data suggest that the subvocally generated prosodic boundary after the long subject NP facilitated the recovery from a garden path, thus primarily supporting one of two competing theoretical frameworks on implicit prosody. Our results underline the prosodic nature of the cognitive processes underlying phrase length effects and contribute cross-linguistic evidence regarding the on-line use of implicit prosody for parsing decisions in silent reading.

An event-related fNIRS investigation of Japanese word order

Japanese is a free word-order language, and allows both subject-object-verb (SOV) and object-subject-verb (OSV) orders. Our previous study using near-infrared spectroscopy (NIRS) imaging revealed that OSV sentences induce more activation in the left frontal lobe than SOV sentences. The present study develops our previous experiment: (1) by adopting an event-related design, and (2) by using sentences involving the adverb naze 'why', which plays a prominent role in recent linguistic studies. The results of our new experiment indicated that the cerebral activation in O why SV sentences was significantly larger than that in S why OV sentences, in the right anterior prefrontal region, which is consistent with the assumption that O why SV order is derived from S why OV order. We speculate that the activation observed in the anterior prefrontal cortex during the processing of the sentences involving 'why' might be due to the processing of higher-order function in the cerebral cortex.

On the processing of Japanese wh-questions: an ERP study

The processing of Japanese wh-questions was investigated using event-related brain potentials (ERPs). Unlike in English or German, a wh-element in Japanese need not be displaced from its canonical position, but instead needs a corresponding Q(uestion)-particle to indicate its interrogative scope. We tested to see if there were any processing correlates specific to these features of Japanese wh-questions. Both mono-clausal and bi-clausal Japanese wh-questions elicited right-lateralized anterior negativity (RAN) between wh-words and corresponding Q-particles, relative to structurally-equivalent yes/no-question control conditions. These results suggest a reliable neural processing correlate of the dependency between wh-elements and Q-particles in Japanese, similar to effects of (left) anterior negativity between wh-fillers and gaps in English and German, but with a right- rather than left-lateralized distribution. It is suggested that wh-in-situ questions in Japanese are processed by the incremental formation of a long-distance dependency between wh-elements and their Q-particles, resulting in a working memory load for keeping track of scopeless wh-elements.

Syntactic complexity and ambiguity resolution in a free word order language: behavioral and electrophysiological evidences from Basque

In natural languages some syntactic structures are simpler than others. Syntactically complex structures require further computation that is not required by syntactically simple structures. In particular, canonical, basic word order represents the simplest sentence-structure. Natural languages have different canonical word orders, and they vary in the degree of word order freedom they allow. In the case of free word order, whether canonical word order plays any role in processing is still unclear. In this paper, we present behavioral and electrophysiological evidence that simpler, canonical word order preference is found even in a free word order language. Canonical and derived structures were compared in two self-paced reading and one ERPs experiment. Non-canonical sentences required further syntactic computation in Basque, they showed longer reading times and a modulation of anterior negativities and P600 components providing evidence that even in free word order, case-marking grammars, underlying canonical word order can play a relevant role in sentence processing. These findings could signal universal processing mechanisms because similar processing patterns are found in typologically very distant grammars. We also provide evidence from syntactically fully ambiguous sequences. Our results on ambiguity resolution showed that fully ambiguous sequences were processed as canonical sentences. Moreover, when fully ambiguous sequences were forced to complex interpretation by means of the world knowledge of the participants, a frontal negativity distinguished simple and complex ambiguous sequences. Thus the preference of simple structures is presumably a universal design property for language processing, despite differences on parametric variation of a given grammar.

The neural mechanisms of word order processing revisited: electrophysiological evidence from Japanese

We present two ERP studies on the processing of word order variations in Japanese, a language that is suited to shedding further light on the implications of word order freedom for neurocognitive approaches to sentence comprehension. Experiment 1 used auditory presentation and revealed that initial accusative objects elicit increased processing costs in comparison to initial subjects (in the form of a transient negativity) only when followed by a prosodic boundary. A similar effect was observed using visual presentation in Experiment 2, however only for accusative but not for dative objects. These results support a relational account of word order processing, in which the costs of comprehending an object-initial word order are determined by the linearization properties of the initial object in relation to the linearization properties of possible upcoming arguments. In the absence of a prosodic boundary, the possibility for subject omission in Japanese renders it likely that the initial accusative is the only argument in the clause. Hence, no upcoming arguments are expected and no linearization problem can arise. A prosodic boundary or visual segmentation, by contrast, indicate an object-before-subject word order, thereby leading to a mismatch between argument "prominence" (e.g. in terms of thematic roles) and linear order. This mismatch is alleviated when the initial object is highly prominent itself (e.g. in the case of a dative, which can bear the higher-ranking thematic role in a two argument relation). We argue that the processing mechanism at work here can be distinguished from more general aspects of "dependency processing" in object-initial sentences.