Matthias Schlesewsky

The extended argument dependency model: A neurocognitive approach to sentence comprehension across languages

Real-time language comprehension is a principal cognitive ability and thereby relates to central properties of the human cognitive architecture. Yet how do the presumably universal cognitive and neural substrates of language processing relate to the astounding diversity of human languages (over 5,000)? The authors present a neurocognitive model of online comprehension, the extended argument dependency model (eADM), that accounts for cross-linguistic unity and diversity in the processing of core constituents (verbs and arguments). The eADM postulates that core constituent processing proceeds in three hierarchically organized phases: (1) constituent structure building without relational interpretation, (2) argument role assignment via a restricted set of cross-linguistically motivated information types (e.g., case, animacy), and (3) completion of argument interpretation using information from further domains (e.g., discourse context, plausibility). This basic architecture is assumed to be universal, with cross-linguistic variation deriving primarily from the information types applied in Phase 2 of comprehension. This conception can derive the appearance of similar neurophysiological and neuroanatomical processing correlates in seemingly disparate structures in different languages and, conversely, of cross-linguistic differences in the processing of similar sentence structures.

Revisiting the role of Broca's area in sentence processing: syntactic integration versus syntactic working memory.

Most previous neuroimaging studies of sentence processing have associated Brocas area with syntactic processing; however, the exact nature of the processes subserved by this brain region is yet not well understood. Although some authors suggest that Brodmann area (BA) 44 of the left inferior frontal gyrus (i.e., Brocas area) is relevant for syntactic integration processes, others claim that it is associated with working memory mechanisms relevant for language processing. To dissociate these two possible functions, the present study investigated hemodynamic responses elicited while participants processed German indirect wh‐questions. Activation increases were observed in left BA 44 together with superior temporal areas and right hemispheric homologues for sentences with noncanonical word order, in which a verb argument was dislocated from its canonical position over a relatively long distance. In these sentences, syntactic working memory load was assumed to be greatest. In contrast, no activation increase was elicited by object–initial as opposed to subject–initial sentences that did not differ with respect to working memory costs but with respect to syntactic integration costs. These data strongly suggest that Brocas area plays a critical role in syntactic working memory during online sentence comprehension. Hum. Brain Mapping 24:79–91, 2005.

Separating syntactic memory costs and syntactic integration costs during parsing: The processing of German WH-questions.

Event-related brain potentials (ERPs) were recorded while participants processed case-unambiguous German subject and object WH-questions with either a long or a short distance between the WH-filler and its gap. A sustained left anterior negativity was observed for object questions with long filler-gap distance but not for short object questions. This negativity was modulated by individual differences in working memory capacity. No comparable negativity was elicited by WHETHER-questions which did not contain a filler-gap dependency. A positive-going ERP effect was observed for short and long object WH-questions at the position of the second noun phrase. We interpret the sustained negativity as reflecting working memory processes required for maintaining the dislocated object in memory. Processing costs associated with integrating the stored element into the phrase structure representation are indicated by the local positivity. These results support the notion of separable syntactic working memory and syntactic integration cost components as causes of processing difficulty in complex sentences.

Syntactic working memory and the establishment of filler-gap dependencies: insights from ERPs and fMRI.

In this contribution, we review an ERP experiment and an fMRI experiment which investigated the processing of German wh-questions. On the basis of the ERP results, we will discuss current models of sentence processing and resource distribution during sentence comprehension. We argue that there exists a separate cognitive or neural resource that supports syntactic working memory processes necessary for the temporary maintenance of syntactic information for the parser. In the context of wh-movement, such a memory component is necessary for establishing filler-gap dependencies. The data obtained from the fMRI experiment will be used to discuss the results of previous neuroimaging studies of sentence processing. It is claimed that syntactic working memory, rather than syntactic processing per se, is supported by Brocas Area.

The N400 reflects problems of thematic hierarchizing.

Using event-related potentials (ERPs), we present evidence that the current interpretation of the N400 component must be extended. This component is elicited in incorrect German sentences with two grammatical subjects, thereby showing its sensitivity to thematic relations between arguments in a sentence (who is doing what to whom). Such a violation only elicits an N400 when both arguments are animate but not when one of them is animate and the other inanimate, thus showing that the brain uses animacy information to overcome interpretation problems due to thematic competition. Structures with two subjects additionally elicit a P600 component which occurs independently of the animacy variation. Thus, animacy information does not appear to influence the syntactic processing problems resulting from such violations.

The role of prominence information in the real time comprehension of transitive constructions: A cross-linguistic approach

Approaches to language processing have traditionally been formulated with reference to general cognitive concepts (e.g. working memory limitations) or have based their representational assumptions on concepts from generative linguistic theory (e.g. structure determines interpretation). Thus, many well-established generalisations about language that have emerged from cross-linguistic/typological research have not as yet had a major influence in shaping ideas about online processing. Here, we examine the viability of using typologically motivated concepts to account for phenomena in online language comprehension. In particular, we focus on the comprehension of simple transitive sentences (i.e. sentences involving two arguments/event participants) and cross-linguistic similarities and differences in how they are processed. We argue that incremental argument interpretation in these structures is best explained with reference to a range of cross-linguistically motivated, hierarchically ordered information types termed ‘prominence scales’ (e.g. animacy, definiteness/specificity, case marking and linear order). We show that the assumption of prominence-based argument processing can capture a wide range of recent neurocognitive findings, as well as deriving well-known behavioural results.

Reconciling time, space and function: A new dorsal-ventral stream model of sentence comprehension

We present a new dorsal-ventral stream framework for language comprehension which unifies basic neurobiological assumptions (Rauschecker & Scott, 2009) with a cross-linguistic neurocognitive sentence comprehension model (eADM; Bornkessel & Schlesewsky, 2006). The dissociation between (time-dependent) syntactic structure-building and (time-independent) sentence interpretation assumed within the eADM provides a basis for the division of labour between the dorsal and ventral streams in comprehension. We posit that the ventral stream performs time-independent unifications of conceptual schemata, serving to create auditory objects of increasing complexity. The dorsal stream engages in the time-dependent combination of elements, subserving both syntactic structuring and a linkage to action. Furthermore, frontal regions accomplish general aspects of cognitive control in the service of action planning and execution rather than linguistic processing. This architecture is supported by a range of existing empirical findings and helps to resolve a number of theoretical and empirical puzzles within the existing dorsal-ventral streams literature.

The P600 as an indicator of syntactic ambiguity.

In a study using event-related brain potentials, we show that the current characterization of the P600 component as an indicator of revision processes (reanalysis and repair) in sentence comprehension must be extended to include the recognition of syntactic ambiguity. By comparing the processing of ambiguous and unambiguous sentence constituents in German, we show that the P600 is elicited when our language processing system has syntactic alternatives at a certain item given in the input string. That the P600 is sensitive to syntactic ambiguity adds crucial evidence to current debates in psycholinguistic modelling, as the results clearly favour parallel models of syntactic processing which assume that ambiguity is recognized and costly.

The emergence of the unmarked: A new perspective on the language-specific function of Broca's area

A number of neuroimaging studies have implicated an involvement of Brocas area, particularly of the pars opercularis of the left inferior frontal gyrus (IFG), in the processing of complex (permuted) sentences. However, functional interpretations of this regions role range from very general (e.g., in terms of working memory) to highly specific (e.g., as supporting particular types of syntactic operations). A dissociation of these competing accounts is often impossible because in most cases, the language internal complexity of permuted sentence structures is accompanied invariably by increasing costs of a more general cognitive nature (e.g., working memory, task difficulty, and acceptability). We used functional magnetic resonance imaging to explore the precise nature of the pars opercularis activation in the processing of permuted sentences by examining the permutation of pronouns in German. Although clearly involving a permutation operation, sentences with an initial object pronoun behave like simple, subject‐initial sentences (e.g., in terms of acceptability) because of a rule stating that pronouns should generally precede non‐pronominal arguments. The results of the experiment show that in contrast to non‐pronominal permutations, sentences with a permuted pronoun do not engender enhanced pars opercularis activation. Our findings therefore speak against both language‐related working memory and transformation‐based accounts of this regions role in sentence comprehension. Rather, we argue that the pars opercularis of the left IFG supports the language‐specific linearization of hierarchical linguistic dependencies. Hum Brain Mapp, 2005.

To Predict or Not to Predict: Influences of Task and Strategy on the Processing of Semantic Relations

We report a series of event-related potential experiments designed to dissociate the functionally distinct processes involved in the comprehension of highly restricted lexical-semantic relations (antonyms). We sought to differentiate between influences of semantic relatedness (which are independent of the experimental setting) and processes related to predictability (which differ as a function of the experimental environment). To this end, we conducted three ERP studies contrasting the processing of antonym relations (black-white) with that of related (black-yellow) and unrelated (black-nice) word pairs. Whereas the lexical-semantic manipulation was kept constant across experiments, the experimental environment and the task demands varied: Experiment 1 presented the word pairs in a sentence context of the form The opposite of X is Y and used a sensicality judgment. Experiment 2 used a word pair presentation mode and a lexical decision task. Experiment 3 also examined word pairs, but with an antonymy judgment task. All three experiments revealed a graded N400 response (unrelated > related > antonyms), thus supporting the assumption that semantic associations are processed automatically. In addition, the experiments revealed that, in highly constrained task environments, the N400 gradation occurs simultaneously with a P300 effect for the antonym condition, thus leading to the superficial impression of an extremely reduced N400 for antonym pairs. Comparisons across experiments and participant groups revealed that the P300 effect is not only a function of stimulus constraints (i.e., sentence context) and experimental task, but that it is also crucially influenced by individual processing strategies used to achieve successful task performance.