The sentence wrap-up dogma.

Current sentence processing research has focused on early effects of the on-line incremental processes that are performed at each word or constituent during processing. However, less attention has been devoted to what happens at the end of the clause or sentence. More specifically, over the last decade and a half, a lot of effort has been put into avoiding measuring event-related brain potentials (ERPs) at the final word of a sentence, because of the possible effects of sentence wrap-up. This article reviews the evidence on how and when sentence wrap-up impacts behavioral and ERP results. Even though the end of the sentence is associated with a positive-going ERP wave, thus far this effect has not been associated with any factors hypothesized to affect wrap-up. In addition, ERP responses to violations have not been affected by this positivity. "Sentence-final" negativities reported in the literature are not unique to sentence final positions, nor do they obscure or distort ERP effects associated with linguistic manipulations. Finally, the empirical evidence used to argue that sentence-final ERPs are different from those recorded at sentence-medial positions is weak at most. Measuring ERPs at sentence-final positions is therefore certainly not to be avoided at all costs, especially not in cases where the structure of the language under investigation requires it. More importantly, researchers should follow rigorous method in their experimental design, avoid decision tasks which may induce ERP confounds, and ensure all other possible explanations for results are considered. Although this article is directed at a particular dogma from a particular literature, this review shows that it is important to reassess what is regarded as "general knowledge" from time to time.

Age Effects in L2 Grammar Processing as Revealed by ERPs and How (Not) to Study Them.

In this study we investigate the effect of age of acquisition (AoA) on grammatical processing in second language learners as measured by event-related brain potentials (ERPs). We compare a traditional analysis involving the calculation of averages across a certain time window of the ERP waveform, analyzed with categorical groups (early vs. late), with a generalized additive modeling analysis, which allows us to take into account the full range of variability in both AoA and time. Sixty-six Slavic advanced learners of German listened to German sentences with correct and incorrect use of non-finite verbs and grammatical gender agreement. We show that the ERP signal depends on the AoA of the learner, as well as on the regularity of the structure under investigation. For gender agreement, a gradual change in processing strategies can be shown that varies by AoA, with younger learners showing a P600 and older learners showing a posterior negativity. For verb agreement, all learners show a P600 effect, irrespective of AoA. Based on their behavioral responses in an offline grammaticality judgment task, we argue that the late learners resort to computationally less efficient processing strategies when confronted with (lexically determined) syntactic constructions different from the L1. In addition, this study highlights the insights the explicit focus on the time course of the ERP signal in our analysis framework can offer compared to the traditional analysis.

Prolonged L2 immersion engenders little change in morphosyntactic processing of bilingual natives.

Bilingual and monolingual language processing differ, presumably because of constant parallel activation of both languages in bilinguals. We attempt to isolate the effects of parallel activation in a group of German first-language (L1) attriters, who have grown up as monolingual natives before emigrating to an L2 environment. We hypothesized that prolonged immersion will lead to changes in the processing of morphosyntactic violations. Two types of constructions were presented as stimuli in an event-related potential experiment: (1) verb form combinations (auxiliaries+past participles and modals+infinitives) and (2) determiner-noun combinations marked for grammatical gender. L1 attriters showed the same response to violations of gender agreement as monolingual controls (i.e. a significant P600 effect strongest over posterior electrodes). Incorrect verb form combinations also elicited a significant posterior P600 effect in both groups. In attriters, however, there was an additional posterior N400 effect for this type of violation. Such biphasic patterns have been found before in L1 and L2 speakers of English and might reflect the influence of this language. Generally, we interpret our results as evidence for the stability of the deeply entrenched L1 system, even in the face of L2 interference.

When correction turns positive: processing corrective prosody in Dutch.

Current research on spoken language does not provide a consistent picture as to whether prosody, the melody and rhythm of speech, conveys a specific meaning. Perception studies show that English listeners assign meaning to prosodic patterns, and, for instance, associate some accents with contrast, whereas Dutch listeners behave more controversially. In two ERP studies we tested how Dutch listeners process words carrying two types of accents, which either provided new information (new information accents) or corrected information (corrective accents), both in single sentences (experiment 1) and after corrective and new information questions (experiment 2). In both experiments corrective accents elicited a sustained positivity as compared to new information accents, which started earlier in context than in single sentences. The positivity was not modulated by the nature of the preceding question, suggesting that the underlying neural mechanism likely reflects the construction of an interpretation to the accented word, either by identifying an alternative in context or by inferring it when no context is present. Our experimental results provide strong evidence for inferential processes related to prosodic contours in Dutch.

An ERP study on L2 syntax processing: When do learners fail?

Event-related brain potentials (ERPs) can reveal online processing differences between native speakers and second language (L2) learners during language comprehension. Using the P600 as a measure of native-likeness, we investigated processing of grammatical gender agreement in highly proficient immersed Romance L2 learners of Dutch. We demonstrate that these late learners consistently fail to show native-like sensitivity to gender violations. This appears to be due to a combination of differences from the gender marking in their L1 and the relatively opaque Dutch gender system. We find that L2 use predicts the effect magnitude of non-finite verb violations, a relatively regular and transparent construction, but not that of gender agreement violations. There were no effects of age of acquisition, length of residence, proficiency or offline gender knowledge. Additionally, a within-subject comparison of stimulus modalities (written vs. auditory) shows that immersed learners may show some of the effects only in the auditory modality; in non-finite verb violations, an early native-like N400 was only present for auditory stimuli. However, modality failed to influence the response to gender. Taken together, the results confirm the persistent problems of Romance learners of Dutch with online gender processing and show that they cannot be overcome by reducing task demands related to the modality of stimulus presentation.

Questions left unanswered: how the brain responds to missing information.

It sometimes happens that when someone asks a question, the addressee does not give an adequate answer, for instance by leaving out part of the required information. The person who posed the question may wonder why the information was omitted, and engage in extensive processing to find out what the partial answer actually means. The present study looks at the neural correlates of the pragmatic processes invoked by partial answers to questions. Two experiments are presented in which participants read mini-dialogues while their Event-Related brain Potentials (ERPs) are being measured. In both experiments, violating the dependency between questions and answers was found to lead to an increase in the amplitude of the P600 component. We interpret these P600-effects as reflecting the increased effort in creating a coherent representation of what is communicated. This effortful processing might include the computation of what the dialogue participant meant to communicate by withholding information. Our study is one of few investigating language processing in conversation, be it that our participants were 'eavesdroppers' instead of real interactants. Our results contribute to the as of yet small range of pragmatic phenomena that modulate the processes underlying the P600 component, and suggest that people immediately attempt to regain cohesion if a question-answer dependency is violated in an ongoing conversation.

Comprehension of marked pronouns in Spanish and English: object anaphors cross-linguistically.

Previous research on pronoun resolution has identified several individual factors that are deemed to be important for resolving reference. In this paper, we argue that of these factors, as tested here, plausibility is the most important, but interacts with form markedness and structural parallelism. We investigated how listeners resolved object pronouns that were ambiguous in the sense of having more than one possible antecedent. We manipulated the form of the anaphoric expression in terms of accentuation (English: Experiments 1a and 2a) and morphology (Spanish: Experiments 1b and 2b). We looked at sentences where both antecedents were equally plausible, or where only one of the antecedents was plausible. Listeners generally resolved toward the (parallel) grammatical object of the previous clause. When the pronouns were marked due to accentuation (English) or use of specific morphology (Spanish), preference switched to the alternative antecedent, the grammatical subject of the previous clause. In contrast, when one of the two antecedents was a much more plausible antecedent than the other, antecedent choice was almost wholly dictated by plausibility, although reference form prominence did significantly attenuate the strength of the preference.

The whole is more than the sum of its parts - audiovisual processing of phonemes investigated with ERPs.

In the current ERP study, an active oddball task was carried out, testing pure tones and auditory, visual and audiovisual syllables. For pure tones, an MMN, an N2b, and a P3 were found, confirming traditional findings. Auditory syllables evoked an N2 and a P3. We found that the amplitude of the P3 depended on the distance between standard and deviant. A smaller distance required more attention, which was reflected in a larger amplitude. An analysis of audiovisual material, after correction for visual activity, showed that McGurk type stimuli evoked brain responses that differed from both the standard and the congruent deviants. Finally, we found that congruent audiovisual stimuli elicited an N2 with a shorter latency and a P3 with a smaller amplitude than auditory stimuli. The current ERP study, thus, shows that for audiovisual processing the whole is more than the sum of its parts.

Processing polarity: ERP evidence for differences between positive and negative polarity.

The goal of the present study was to investigate event-related potential (ERP) responses to Dutch negative and positive polarity adverbs of degree presented in licensed and unlicensed contexts with negative and affirmative particles directly preceding the polarity item. To control for effects of the processing of negation as such, neutral adverbs were also presented in negative and affirmative contexts. The results did not show any significant effect of negation for the non-polar adverbs, allowing context effects for polarity items to be interpreted as being due to the appropriateness of the context. Negative polarity violations elicited an N400 response that might reflect the lack of semantic congruity of the negative polarity item in an affirmative context. In contrast, processing positive polarity items in context of negation resulted in a positive effect resembling the P600, which may be considered as a marker of a different sort of integration difficulty caused by violation of licensing conditions and/or a search for a licensor in the wider discourse context. The study presented here is the first to show an unambiguous dissociation between responses to negative and positive polarity violations. This dissociation argues for different mechanisms underlying the processing of these two types of polarity; we propose that positive polarity items are sensitive to wider discourse context, while negative polarity items are more sensitive to local lexical context.

Less is not more: neural responses to missing and superfluous accents in context.

Prosody, particularly accent, aids comprehension by drawing attention to important elements such as the information that answers a question. A study using ERP registration investigated how the brain deals with the interpretation of prosodic prominence. Sentences were embedded in short dialogues and contained accented elements that were congruous or incongruous with respect to a preceding question. In contrast to previous studies, no explicit prosodic judgment task was added. Robust effects of accentuation were evident in the form of an "accent positivity" (200-500 msec) for accented elements irrespective of their congruity. Our results show that incongruously accented elements, that is, superfluous accents, activate a specific set of neural systems that is inactive in case of incongruously unaccented elements, that is, missing accents. Superfluous accents triggered an early positivity around 100 msec poststimulus, followed by a right-lateralized negative effect (N400). This response suggests that redundant information is identified immediately and leads to the activation of a neural system that is associated with semantic processing (N400). No such effects were found when contextually expected accents were missing. In a later time window, both missing and superfluous accents triggered a late positivity on midline electrodes, presumably related to making sense of both kinds of mismatching stimuli. These results challenge previous findings of greater processing for missing accents and suggest that the natural processing of prosody involves a set of distinct, temporally organized neural systems.

Sentence comprehension and its association with executive functions in patients with Parkinson's disease.

Coexistent impairments in executive functions and language comprehension in patients with Parkinson's disease (PD) have been repeatedly observed. In this study, the aim was to provide insights into the interaction between linguistic representation and processing and executive functioning. Therefore, sentence comprehension and executive functions were assessed in 28 Dutch-speaking PD patients and 28 healthy control subjects. Three aspects of the sentence materials were varied: (1) phrase structure complexity, (2) sentence length, and (3) picture congruence. PD patients with mild-to-moderate disease severity showed decreased sentence comprehension compared to healthy control subjects. The difficulties encountered by PD patients were not limited to one aspect of the sentence materials. The same pattern of results was present in healthy control subjects. Deficits in set-switching were specifically associated with the comprehension of passive sentences. Generally, our study confirms that there does not appear to be a language faculty encapsulated from the influence of executive functions.

Neural correlates of Dutch Verb Second in speech production.

Dutch speakers with agrammatic Broca's aphasia are known to have problems with the production of finite verbs in main clauses. This performance pattern has been accounted for in terms of the specific syntactic complexity of the Dutch main clause structure, which requires an extra syntactic operation (Verb Second), relative to the basic Subject-Object-Verb order surfacing in Dutch subordinate clauses. We report an fMRI study into the question whether this syntactic complexity is reflected in increased brain activation correlated with the production of Dutch main clause word order, in speakers without language impairment. Nineteen healthy subjects performed a covert sentence completion task, during which main and subordinate clauses were alternately elicited in a block design. Results show a left middle to superior frontal cluster of activation correlated to production of Verb-Second over Verb-Final clauses, with no activation in the opposite contrast. This activation pattern is counter to what might be expected from the frequency distribution of main and subordinate clauses. We conclude that the Verb-Second deviation from the basic Dutch SOV word order costs extra neural resources and that this also underlies the agrammatic problems with the production of finite verbs in Dutch main clauses.

Semantic ambiguity processing in sentence context: Evidence from event-related fMRI.

Lexical semantic ambiguity is the phenomenon when a word has multiple meanings (e.g. 'bank'). The aim of this event-related functional MRI study was to identify those brain areas, which are involved in contextually driven ambiguity resolution. Ambiguous words were selected which have a most frequent, dominant, and less frequent, subordinate meaning. These words were presented in two types of sentences: (1) a sentence congruent with the dominant interpretation and (2) a sentence congruent with the subordinate interpretation. Sentences without ambiguous words served as a control condition. The ambiguous words always occurred early in the sentences and were biased towards one particular meaning by the final word(s) of the sentence; the event at the end of the sentences was modeled. The results indicate that a bilaterally distributed network supports semantic ambiguity comprehension: left (BA 45/44) and right (BA 47) inferior frontal gyri and left (BA 20/37) and right inferior/middle temporal gyri (BA 20). The pattern of activation is most consistent with a scenario in which initially a frequency-based probabilistic choice is made between the alternative meanings, and the meaning is updated when this interpretation does not fit into the final disambiguating context. The neural pattern is consistent with the results of other neuroimaging experiments which manipulated various aspects of integrative and context processing task demands. The presence of a bilateral network is also in line with the lesion and divided visual field literature, but contrary to earlier claims, the two hemispheres appear to play similar roles during semantic ambiguity resolution.

Evidence for bilateral involvement in idiom comprehension: An fMRI study.

The goal of the current study was to identify the neural substrate of idiom comprehension using fMRI. Idioms are familiar, fixed expressions whose meaning is not dependent on the literal interpretation of the component words. We presented literally plausible idioms in a sentence forcing a figurative or a literal interpretation and contrasted them with sentences containing idioms for which no literal interpretation was available and with unambiguously literal sentences. The major finding of the current study is that figurative comprehension in the case of both ambiguous and unambiguous idioms is supported by bilateral inferior frontal gyri and left middle temporal gyrus. The right middle temporal gyrus is also involved, but seems to exclusively process the ambiguous idioms. Therefore, our data suggest a bilateral neural network underlying figurative comprehension, as opposed to the exclusive participation of the right hemisphere. The data also provide evidence against proposed models of idiom comprehension in which literal processing is by-passed, since figurative processing demanded more resources than literal processing in the language network.

Processing of visual semantic information to concrete words: temporal dynamics and neural mechanisms indicated by event-related brain potentials( ).

Event-related brain potentials were used to study the retrieval of visual semantic information to concrete words, and to investigate possible structural overlap between visual object working memory and concreteness effects in word processing. Subjects performed an object working memory task that involved 5 s retention of simple 4-angled polygons (load 1), complex 10-angled polygons (load 2), and a no-load baseline condition. During the polygon retention interval subjects were presented with a lexical decision task to auditory presented concrete (imageable) and abstract (nonimageable) words, and pseudowords. ERP results are consistent with the use of object working memory for the visualisation of concrete words. Our data indicate a two-step processing model of visual semantics in which visual descriptive information of concrete words is first encoded in semantic memory (indicated by an anterior N400 and posterior occipital positivity), and is subsequently visualised via the network for object working memory (reflected by a left frontal positive slow wave and a bilateral occipital slow wave negativity). Results are discussed in the light of contemporary models of semantic memory.

Memory effects in syntactic ERP tasks.

The study presented here investigated the role of memory in normal sentence processing by looking at ERP effects to normal sentences and sentences containing grammatical violations. Sentences where the critical word was in the middle of the sentence were compared to sentences where the critical word always occurred in sentence-final position. Grammaticality judgments were required at the end of the sentence. While the violations in both conditions result in the expected increase in the P600 component (reflecting the fact that the syntactic violation is being processed), the sentences with the sentence-medial critical word also result in a late frontal negativity effect. It is hypothesized that this effect is due to greater memory requirements that are needed to keep the violation in mind until a response can be made at the end of the sentence. The maintenance of the decision that a sentence is ungrammatical must be kept in memory longer for sentence-medial violations as opposed to when the violation occurs at the end of the sentence (immediately preceding the moment at which the judgment can be made).

Activations of "motor" and other non-language structures during sentence comprehension.

In this paper we report the results of an experiment in which subjects read syntactically unambiguous and ambiguous sentences which were disambiguated after several words to the less likely possibility. Understanding such sentences involves building an initial structure, inhibiting the non-preferred structure, detecting that later input is incompatible with the initial structure, and reactivating the alternative structure. The ambiguous sentences activated four areas more than the unambiguous sentences. These areas are the left inferior frontal gyrus (IFG), the right basal ganglia (BG), the right posterior dorsal cerebellum (CB) and the left median superior frontal gyrus (SFG). The left IFG is normally activated when syntactic processing complexity is increased and probably supports that function in the current study as well. We discuss four hypotheses concerning how these areas may support comprehension of syntactically ambiguous sentences. (1) The left IFG, right CB and BG could support articulatory rehearsal used to support the processing of ambiguous sentences. This seems unlikely since the activation pattern associated with articulatory rehearsal in other studies is not similar to that seen here. (2) The CB acts as an error detector in motor processing. Error detection is important for recognizing that the wrong sentence structure has been chosen initially. (3) The BG acts to select and sequence movements in the motor domain and in cognitive domains may serve to inhibit competing and completed plans which is not unlike inhibiting the initially non-preferred structure or "unchoosing" the initial choice when incompatible syntactic input is received. (4) The left median SFG is relevant for the evaluation of plausibility. Evaluating the plausibility of the two possibilities provides an important basis for choosing between them. The notion of the use of domain general cognitive processes to support a linguistic process is in line with recent suggestions that the a given area may subserve a specific cognitive task because it carries out an appropriate sort of computation rather than because it supports a specific cognitive domain.

Seeing words in context: the interaction of lexical and sentence level information during reading.

The ERP experiment reported here addresses some outstanding questions regarding word processing in sentential contexts: (1) Does only the 'message-level' representation (the representation of sentence meaning combining lexico-semantic and syntactic constraints) affect the processing of the incoming word [J. Exp. Psychol.: Learn. Mem. Cogn. 20 (1994) 92]? (2) Is lexically specified semantic relatedness between multiple words the primary factor instead [J. Exp. Psychol.: Learn. Mem. Cogn. 15 (1989) 791]? (3) Alternatively, do word and sentence level information interact during sentence comprehension? Volunteers read sentences (e.g. Dutch sentences resembling The javelin was by the athletes...) in which the (passive) syntactic structure and the semantic content of the lexical items together created a strong expectation of a specific final word (e.g., thrown), but also sentences in which the syntactic structure was changed from passive to active (e.g. Dutch sentences resembling The javelin has the athletes...), which altered the message level constraint substantially and strongly reduced the expectation of any particular completion. Half of the sentences ended in a final word with a good lexico-semantic fit relative to the preceding content words (e.g. thrown, fitting well with the preceding javelin and athletes). This creates very plausible sentences in the strong constraint context but semantically anomalous ones in the weakly constraining context (e.g., The javelin has the athletes thrown). In the other half the final word had a poor lexico-semantic fit (e.g., summarized that does not fit at all with javelin and athletes). Good lexico-semantic fit endings showed no difference in N400 amplitude in the strong and weak message-level constraint sentences, despite the fact that the latter were semantically anomalous. This result suggests that lexico-semantic fit can be more important for word processing than the meaning of the sentence as determined by the syntactic structure, at least initially. These conditions did differ, however, in the region of the P600 where the anomalous weak constraint version was much more positive, a pattern usually seen with ungrammatical sentences. The processing of poor lexico-semantic fit words showed a quite different pattern; in both strong and weak constraint sentences they elicited a substantial N400 effect, but N400-amplitude was significantly more negative following strong constraint contexts, even though both sentence contexts were equivalently anomalous. Taken together, these findings provide evidence for the importance of both message-level and lexico-semantic information during sentence comprehension. The implications for theories of sentence interpretation are discussed and an extension of the message-based hypothesis will be proposed.

An event-related potential investigation of the relationship between semantic and perceptual levels of representation.

The present study was conducted to investigate relationships between semantic and perceptual levels of representation. A picture-word repetition paradigm was used in which we manipulated the semantic relationship between pictures and words. Experiment 1 involved two types of trials, one with words that had the same meaning as pictures and one with words that were unrelated to pictures. In Experiment 2 we replaced words that were identical in meaning with words that were semantically associated to pictures. In both experiments, visually presented probe stimuli were used to determine the presence of perceptual effects within the visual system, originating from the semantic interaction between words and pictures. In both experiments, conditions with unrelated picture-word pairs generated a search process following the N400 which included activity overlying the visual cortex. Probe stimuli were found to attenuate the amplitude of the search related negativity. The latency of the interaction, which was significant at the time of the N1 response to the probe, suggested that the attempt to find a relationship between the picture and the word involved processing within extrastriate visual areas. UVF probes provided stronger attenuation, possibly because the UVF has direct transmission to the ventral processing stream which is believed to be involved in visual semantic processing. Semantic interactions between matching picture-word pairs in Experiment 1 were found to have an effect on the ERPs to probes presented at the same location as pictures. Probes presented under these conditions showed a stronger P2 over frontal areas followed by a more negative P3 over occipital areas. Although we had expected beforehand to find earlier effects in the latency of the probes' P1 and N1 responses, this result is consistent with the idea that retinotopic levels of object representation are linked with the semantic level of object description. Unlike Experiment 1, same location probes presented in associated picture-word conditions of Experiment 2 did not result in any specific ERP effects on the P2 and P3 components. This suggest that semantic interactions between pictures and words do not automatically propagate to the perceptual level, unless there is direct reference from the word to the visual representation of the object.