First-Pass versus Second-Pass Parsing Processes in a Wernicke''s and a Broca''s Aphasic: Electrophysiological Evidence for a Double Dissociation

The present paper is a first attempt to integrate the classical brain lesion behavioral impairment approach of functional neuroanatomy and the electrophysiological brain mapping approach in the domain of syntactic processing. In a group of normal age-matched controls we identified three electrophysiological components previously observed in correlation with language comprehension processes: an early left anterior negativity normally seen in correlation with syntactic first-pass parsing processes (ELAN), a centroparietal negativity seen in correlation with processes of lexical-semantic integration (N400), and a late centroparietal positivity observed in correlation with secondary syntactic processes of reanalysis and repair (P600). The early left anterior negativity was absent in a patient with an extended lesion in the anterior part of the left hemisphere sparing the temporal lobe, although the late centroparietal positivity and the centroparietal N400 were present. In a patient with a left temporal-parietal lesion the early left anterior negativity was found to be present, whereas the N400 component was absent. These findings suggest that first-pass parsing and secondary processes are subserved by distinct brain systems.     

Lexical integration: Sequential effects of syntactic and semantic information

Both semantic and syntactic context constraints can influence word processing at the level of lexical integration. In event-related brain potentials (ERPs), semantic integration is reflected by a negativity around 400 msec (N400), whereas phrase structure assignment and syntactic integration are assumed to be reflected by an early left anterior negativity and a late positivity (P600), respectively. An ERP study is presented in which participants read different types of sentences whose terminal verb was either congruent with the preceding context or incongruent due to a phrase structure violation, a semantic violation, or both. The main finding was that only the pure semantic violation condition, but not the combined semantic and syntactic violation condition, elicited a large N400. The two conditions containing phrase structure violations were predominantly characterized by a P600. Both semantic violation conditions, moreover, displayed a late negativity around 700 msec that overlapped with the P600 in the double violation condition. The absence of an N400 effect for elements that are syntactically as well as semantically incongruent with prior context suggests an early influence of phrase structure information on processes of lexical-semantic integration. The present data are discussed in comparison to previous ERP findings, and a new view of lexical integration processes is proposed.     

Distinct Neurophysiological Patterns Reflecting Aspects of Syntactic Complexity and Syntactic Repair

Aspects of syntactic complexity and syntactic repair were investigated by comparing the event-related (brain) potentials (ERPs) for sentences of different syntactic complexity to those containing a syntactic violation. Previous research had shown that both aspects of syntactic processing are reflected in a late positivity (P600). Results from the present reading experiment demonstrate, however, that although both processing aspects elicit a late positivity, they are different in distribution. The repair-related positivity preceded by a negativity displayed a centroparietal distribution, whereas the complexity-related positivity showed a frontocentral scalp distribution. These data indicate that the P600 is not a unitary phenomenon. Moreover, the distributional differences strongly suggest that different neural structures underlie the two aspects of processing, namely syntactic repair and syntactic integration difficulties, most evident when processing syntactically complex sentences.     

On the early left-anterior negativity (ELAN) in syntax studies

Within the framework of Friederici’s (2002) neurocognitive model of sentence processing, the early left anterior negativity (ELAN) in event-related potentials (ERPs) has been claimed to be a brain marker of syntactic first-pass parsing. As ELAN components seem to be exclusively elicited by word category violations (phrase structure violations), they have been taken as strong empirical support for syntax-first models of sentence processing and have gained considerable impact on psycholinguistic theory in a variety of domains. The present article reviews relevant ELAN studies and raises a number of serious issues concerning the reliability and validity of the findings. We also discuss how baseline problems and contextual factors can contribute to early ERP effects in studies examining word category violations. We conclude that - despite the apparent wealth of ELAN data - the functional significance of these findings remains largely unclear. The present paper does not claim to have falsified the existence of ELANs or syntax-related early frontal negativities. However, by separating facts from myths, the paper attempts to make a constructive contribution to how future ERP research in the area of syntax processing may better advance our understanding of online sentence comprehension.     

Storage and integration in the processing of filler-gap dependencies: an ERP study of topicalization and wh-movement in German

We recorded event-related brain potentials (ERPs) during the processing of unambiguous German sentences containing different types of filler-gap dependency. Both topicalization constructions and wh-questions were found to elicit a left-anterior negativity (LAN) prior to the processing of the subcategorizing verb, relative to a gap-free control condition. At the subcategorizing verb, sentences containing a wh-dependency produced a parietal positivity (P600) relative to topicalization structures. These results support the claim that separable parsing processes are involved in the processing of syntactic dependencies, with working memory based processes being reflected in an LAN, and the relative difficulty of integrating the filler with its subcategorizer reflected in a P600. Integration cost but not memory cost was found to be influenced by the type of filler-gap dependency involved.     

Prosody and parsing in coordination structures

The effect of prosodic boundary cues on the off-line disambiguation and on-line parsing of coordination structures was examined. It was found that relative clauses were attached to coordinated object noun phrases in preference to second conjuncts in sentences like: The lawyer greeted the powerful barrister and the wise judge who was/were walking to the courtroom. Naive speakers signalled the syntactic contrast between the two structures by a prosodic break between the conjuncts when the relative clause was attached to the second conjunct. Listeners were able to use this prosodic information in both off-line syntactic disambiguation and on-line syntactic parsing. The findings are compatible with a model in which prosody has a strong immediate effect on parsing. It is argued that the current experimental design has avoided confounds present in earlier studies on the on-line integration of prosodic and syntactic information.     

Connectionist natural language parsing

The key developments of two decades of connectionist parsing are reviewed. Connectionist parsers are assessed according to their ability to learn to represent syntactic structures from examples automatically, without being presented with symbolic grammar rules. This review also considers the extent to which connectionist parsers offer computational models of human sentence processing and provide plausible accounts of psycholinguistic data. In considering these issues, special attention is paid to the level of realism, the nature of the modularity, and the type of processing that is to be found in a wide range of parsers.     

The Time Course of Syntactic Activation During Language Processing: A Model Based on Neuropsychological and Neurophysiological Data

This paper presents a model describing the temporal and neurotopological structure of syntactic processes during comprehension. It postulates three distinct phases of language comprehension, two of which are primarily syntactic in nature. During the first phase the parser assigns the initial syntactic structure on the basis of word category information. These early structural processes are assumed to be subserved by the anterior parts of the left hemisphere, as event-related brain potentials show this area to be maximally activated when phrase structure violations are processed and as circumscribed lesions in this area lead to an impairment of the on-line structural assignment. During the second phase lexical-semantic and verb-argument structure information is processed. This phase is neurophysiologically manifest in a negative component in the event-related brain potential around 400 ms after stimulus onset which is distributed over the left and right temporo-parietal areas when lexical-semantic information is processed and over left anterior areas when verb-argument structure information is processed. During the third phase the parser tries to map the initial syntactic structure onto the available lexical-semantic and verb-argument structure information. In case of an unsuccessful match between the two types of information reanalyses may become necessary. These processes of structural reanalysis are correlated with a centroparietally distributed late positive component in the event-related brain potential. The different temporal and topographical patterns of the event-related brain potential. as well as some aspects of aphasics′ comprehension behavior are taken to support the view that these different processing phases are distinct and that the left anterior cortex, in particular, is responsible for the on-line assignment of syntactic structure.     

Prosodic form and parsing commitments

This paper examines the question of whether there are effects of prosody on the syntactic parsing of temporarily ambiguous sentences containing complement verbs. It reports the results of five experiments employing cross-modal response tasks where the visually presented target word was either an appropriate or an inappropriate continuation in terms of the prosodic form of the preceeding auditory sentence fragment. Two experiments employing cross-modal naming only showed indications of sensitivity to syntactic and appropriateness manipulations when coupled with a simultaneous appropriateness judgment task. In contrast, the experiments employing cross-modal lexical decision showed greater sensitivity to syntactic and appropriateness effects. However, while the results from these studies replicated our earlier auditory parsing results and provided support for the suggestion that there are differences in visual and auditory parsing processes and for a constituent-based, minimal commitment type auditory parser, none of the studies demonstrated an effect of prosodic form on the parsing process.     

Head position and parsing ambiguity

A strongly principle-based model of parsing seeks to employ principles of the competence grammar directly in language processing. Within grammatical theory, the Projection Principle holds that each level of syntactic representation is a uniform projection of the lexical properties of heads. With respect to parsing this suggests that a phrasal node cannot be projected until the occurrence of its head and thus constitutes a strong empirical hypothesis concerning the fundamental nature of human language processing. This paper contrasts some cross-linguistic predictions made by a specific Grammarderived parsing model against those of a well-known top-down model whose functional motivation is decidedly nonlinguistic. This latter Minimal Attachment model is found to predict significant difficulty with respect to the processing of languages such as Japanese, which display rather different surface properties than English. This problem is not encountered in a model which recognizes the crucial role of heads in licensing argument structure with respect to Processing as well as Grammar. Cross-linguistic parsing differences are attributed to the linear and structural positions of licensing heads which constitute the primary locus of the cross-linguistic variation which is therefore ultimately to be ascribed directly to the Projection Principle.     

An ERP investigation of binding and coreference

This study examines the nature of violations in processing one class of binding construction, namely those involving reflexives and their antecedents. When arguments of verbs appear at the point where a syntactic violation is detected, a centroparietal positivity occurs, peaking at 600 ms after the presentation of the stimulus (P600), as is consistent with other types of syntactic anomalies. However, nonarguments in similar sentences fail to elicit the same response. For example, the reflexive in "John's brothers like himself" is in an argument position and elicits the P600 when compared to its grammatical counterpart. The nonargument, participating in the same type of mismatch, "John's brothers like Bill and himself," does not elicit the same positivity. This provides evidence that there are two processes involved in parsing this binding construction, one syntactic and another as yet unidentified, perhaps involving meaning or pragmatics.     

Contextual information modulates initial processes of syntactic integration: the role of inter- versus intrasentential predictions

The authors demonstrate that intersentential context may influence syntactic integration processes during online sentence comprehension, although this influence appears to be restricted to cases in which a contextual requirement must be fulfilled. By applying event-related brain potentials to the processing of clause-medial word order variations in German, the authors show that the local processing difficulty (a negativity from 300 to 450 ms) observed for object-initial sentences in a neutral context is also obtained in a (behaviorally) facilitating context in which the object is contextually given. By contrast, the processing pattern for a focused (questioned) initial object does not differ from that for a focused subject: both elicit a parietal positivity (280-480 ms) post-onset of the focused phrase. The authors interpret this early positivity as a general marker of focus integration, a process that appears to briefly supersede sentence-internal requirements.     

The role of incremental parsing in syntactically conditioned word learning

In a series of three experiments, we use children’s noun learning as a probe into their syntactic knowledge as well as their ability to deploy this knowledge, investigating how the predictions children make about upcoming syntactic structure change as their knowledge changes. In the first two experiments, we show that children display a developmental change in their ability to use a noun’s syntactic environment as a cue to its meaning. We argue that this pattern arises from children’s reliance on their knowledge of verbs’ subcategorization frame frequencies to guide parsing, coupled with an inability to revise incremental parsing decisions. We show that this analysis is consistent with the syntactic distributions in child-directed speech. In the third experiment, we show that the change arises from predictions based on verbs’ subcategorization frame frequencies.     

Differences in the perception and time course of syntactic and semantic violations

A reading time and an ERP experiment conducted in Italian investigated the parser's responses to a syntactic violation (subject-verb number agreement) and to a semantic violation (subject-verb selectional restriction), examining the time course of comprehension processes until sentence end. The reading-time data showed that the syntactic violation was detected earlier than the semantic one and that the two violations differed in the time-course. The ERP data fully supported the reading time data: Syntactic anomalies elicited a left anterior negativity (LAN) and a P600. Semantic anomalies elicited a N400 centred on the parietal sites which started 90 ms later (latency 430 ms) than the LAN. Furthermore, the N400 evoked by the words that followed the target word continued and increased until sentence end. The results are discussed with respect to the hypotheses that the parser constructs distinct syntactic and semantic analyses of a sentence and that this characteristic holds cross-linguistically. The appropriateness of different methodologies to the study of sentence processing is also evaluated.     

Studying the grammatical aspects of word recognition: lexical priming,parsing, and syntactic ambiguity resolution

Two experiments are reported examining the relationship between lexical and syntactic processing during language comprehension, combining techniques common to the on-line study of syntactic ambiguity resolution with priming techniques common to the study of lexical processing. By manipulating grammatical properties of lexical primes, we explore how lexically based knowledge is activated and guides combinatory sentence processing. Particularly, we find that nouns (like verbs, see Trueswell & Kim, 1998) can activate detailed lexically specific syntactic information and that these representations guide the resolution of relevant syntactic ambiguities pertaining to verb argument structure. These findings suggest that certain principles of knowledge representation common to theories of lexical knowledge—such as overlapping and distributed representations—also characterize grammatical knowledge. Additionally, observations from an auditory comprehension study suggest similar conclusions about the lexical nature of parsing in spoken language comprehension. They also suggest that thematic role and syntactic preferences are activated during word recognition and that both influence combinatory processing.     

Seven principles of surface structure parsing in natural language

In generative grammar there is a traditional distinction between sentence acceptability, having to do with performance, and sentence grammaticality, having to do with competence. The attempt of this paper is to provide a characterization of the notion ‘acceptable sentence’ in English, with some suggestions as to how this characterization might be made universal. The procedure is to outline a set of procedures which are conjectured to be operative in the assignment of a surface structure tree to an input sentence. To some extent, these principles of parsing are modeled on certain parsing techniques formulated by computer scientists for computer languages. These principles account for the high acceptability of right branching structures, outline the role of grammatical function words in sentence perception, describe what seems to be a fixed limit on short-term memory in linguistic processing, and hypothesize the structure of the internal syntactic processing devices. The operation of various classes of transformations with regard to preparing deep structures for input to parsing procedures such as those outlined in the paper is discussed.     

Auditory awareness negativity is an electrophysiological correlate of awareness in an auditory threshold task

One theory of visual awareness proposes that electrophysiological activity related to awareness occurs in primary visual areas approximately 200 ms after stimulus onset (visual awareness negativity: VAN) and in fronto-parietal areas about 300 ms after stimulus onset (late positivity: LP). Although similar processes might be involved in auditory awareness, only sparse evidence exists for this idea. In the present study, we recorded electrophysiological activity while subjects listened to tones that were presented at their own awareness threshold. The difference in electrophysiological activity elicited by tones that subjects reported being aware of versus unaware of showed an early negativity about 200 ms and a late positivity about 300 ms after stimulus onset. These results closely match those found in vision and provide convincing evidence for an early negativity (auditory awareness negativity: AAN), as well as an LP. These findings suggest that theories of visual awareness are also applicable to auditory awareness.     

Development of action monitoring through adolescence into adulthood: ERP and source localization

In this study we examined the development of three action monitoring event-related potentials (ERPs) - the error-related negativity (ERN/Ne), error positivity (P(E)) and the N2 - and estimated their neural sources. These ERPs were recorded during a flanker task in the following groups: early adolescents (mean age = 12 years), late adolescents (mean age = 16 years), and adults (mean age = 29 years). The amplitudes of the ERN/Ne and N2 were greater in the adult and late adolescent groups than in the early adolescent group. Both of these components had neural sources in the anterior cingulate cortex (ACC). Although P(E) was present across groups, P(E) amplitude was greater in the late adolescent group compared to the adult group and also had neural sources in the ACC. ERN/Ne amplitude was related to post-error slowing across age groups; it was related to task performance only in the adult group. These findings are discussed in light of the role of the maturation of the ACC in the development of action monitoring processes.     

Two distinct parsing stages in nonword reading aloud: Evidence from Russian

Word reading partly depends on the activation of sublexical letter clusters. Previous research has studied which types of letter clusters have psychological saliency, but less is known about cognitive mechanisms of letter string parsing. Here, we take advantage of the high degree of context-dependency of the Russian orthography to examine whether consonant–vowel (CV) clusters are treated as units in two stages of sublexical processing. In two experiments using a nonword reading task, we use two orthogonal manipulations: (a) insertion of a visual disruptor (#) to assess whether CV clusters are kept intact during the early visual parsing stage, and (b) presence of context-dependent grapheme–phoneme correspondences (GPCs; e.g., л[а] → /l/; л[я] → /l^j/), to assess whether CV clusters remain intact or are split during the print-to-speech conversion stage. The results suggest that although CV clusters are initially processed as perceptual units in the early visual parsing stage, letters and not CV clusters drive print-to-speech conversion.