An electrophysiological investigation of referential communication.

A key aspect of linguistic communication involves semantic reference to objects. Presently, we investigate neural responses at objects when reference is disrupted, e.g., "The connoisseur tasted *that wine"… vs. "…*that roof…" Without any previous linguistic context or visual gesture, use of the demonstrative determiner "that" renders interpretation at the noun as incoherent. This incoherence is not based on knowledge of how the world plausibly works but instead is based on grammatical rules of reference. Whereas Event-Related Potential (ERP) responses to sentences such as "The connoisseur tasted the wine …" vs. "the roof" would result in an N400 effect, it is unclear what to expect for doubly incoherent "…*that roof…". Results revealed an N400 effect, as expected, preceded by a P200 component (instead of predicted P600 effect). These independent ERP components at the doubly violated condition support the notion that semantic interpretation can be partitioned into grammatical vs. contextual constructs.

Effects of Dispositional Affect on the N400: Language Processing and Socially Situated Context.

We examined whether the N400 Event-Related Potential (ERP) component would be modulated by dispositional affect during sentence processing. In this study, 33 participants read sentences manipulated by direct object type (congruent vs. incongruent) and object determiner type (definite vs. demonstrative). We were particularly interested in sentences of the form: (i) The connoisseur tasted the wine on the tour vs. (ii) The connoisseur tasted the # roof … We expected that processing incongruent direct objects (#roof) vs. congruent objects (wine) would elicit N400 effects. Previous ERP language experiments have shown that participants in (induced) positive and negative moods were differentially sensitive to semantic anomaly, resulting in different N400 effects. Presently, we ask whether individual dispositional affect scores (as measured by the Positive and Negative Affect Schedule; PANAS) would modulate N400 effects as shown previously. Namely, previous results showed larger N400 effects associated with happy moods and attenuated amplitudes associated with sad moods. Results revealed significant N400 effects, driven by the #roof vs. the wine, where larger amplitude differences were found for individuals showing smaller negative affect (NA) scores, thus partially replicating previous findings. We discuss our results in terms of theories of local (lexical) inhibition, such that low NA promotes stronger lexico-semantic links in sentences. Finally, our results support accounts of language processing that include social and biological characteristics of individuals during real-time sentence comprehension.

A preliminary investigation of dispositional affect, the P300, and sentence processing.

We examined whether dispositional affect modulated the relation between sentence processing and the P300 Event Related Potential (ERP) component. We used sentence stimuli from our previous study, where sentences started with subject nouns that were quantified e.g., Every kid… or not, as in The kid…, and continued with a direct object which was either singular, as in a tree, or plural the trees. In this Stroop-like task, participants read sentences presented in 1- and 2-word chunks, and were asked to identify the number of words on the screen at the target word tree(s), which was always presented alone (and never sentence-final). We replicated previous findings of a P300 effect, at the target tree(s), however, actual by-condition effects differed from previous work. Of interest, clear individual differences were apparent. Participants with relatively lower Positive Affect scores (as measured by the Positive and Negative Affect Schedule; PANAS), showed differential P300 responses to the control condition, Every/The kid climbed the tree. Thus, the present ERP findings demonstrate that dispositional affect modulated P300 effects. These findings suggest that, rather than relying on global heuristic cues for sentence meaning interpretation, these participants may be differentially sensitive to local (grammatical) cues which signify task relevance. We discuss our results in terms of theories of positive affect, where less positive individuals are differentially sensitive to local (grammatical) information.

The Neuronal Correlates of Indeterminate Sentence Comprehension: An fMRI Study.

Sentences such as The author started the book are indeterminate because they do not make explicit what the subject (the author) started doing with the object (the book). In principle, indeterminate sentences allow for an infinite number of interpretations. One theory, however, assumes that these sentences are resolved by semanticcoercion, a linguistic process that forces the noun book to be interpreted as an activity (e.g., writing the book) or by a process that interpolates this activity information in the resulting enriched semantic composition. An alternative theory, pragmatic, assumes classical semantic composition, whereby meaning arises from the denotation of words and how they are combined syntactically, with enrichment obtained via pragmatic inferences beyond linguistic-semantic processes. Cognitive neuroscience studies investigating the neuroanatomical and functional correlates of indeterminate sentences have shown activations either at the ventromedial pre-frontal cortex (vmPFC) or at the left inferior frontal gyrus (L-IFG). These studies have supported the semantic coercion theory assuming that one of these regions is where enriched semantic composition takes place. Employing functional magnetic resonance imaging (fMRI), we found that indeterminate sentences activate bilaterally the superior temporal gyrus (STG), the right inferior frontal gyrus (R-IFG), and the anterior cingulate cortex (ACC), more so than control sentences (The author wrote the book). Activation of indeterminate sentences exceeded that of anomalous sentences (…drank the book) and engaged more left- and right-hemisphere areas than other sentence types. We suggest that the widespread activations for indeterminate sentences represent the deployment of pragmatic-inferential processes, which seek to enrich sentence content without necessarily resorting to semantic coercion.

Interpreting quantifier scope ambiguity: evidence of heuristic first, algorithmic second processing.

The present work suggests that sentence processing requires both heuristic and algorithmic processing streams, where the heuristic processing strategy precedes the algorithmic phase. This conclusion is based on three self-paced reading experiments in which the processing of two-sentence discourses was investigated, where context sentences exhibited quantifier scope ambiguity. Experiment 1 demonstrates that such sentences are processed in a shallow manner. Experiment 2 uses the same stimuli as Experiment 1 but adds questions to ensure deeper processing. Results indicate that reading times are consistent with a lexical-pragmatic interpretation of number associated with context sentences, but responses to questions are consistent with the algorithmic computation of quantifier scope. Experiment 3 shows the same pattern of results as Experiment 2, despite using stimuli with different lexical-pragmatic biases. These effects suggest that language processing can be superficial, and that deeper processing, which is sensitive to structure, only occurs if required. Implications for recent studies of quantifier scope ambiguity are discussed.

ERPs reveal sensitivity to hypothetical contexts in spoken discourse.

We used event-related potentials to examine the interaction between two dimensions of discourse comprehension: (i) referential dependencies across sentences (e.g. between the pronoun 'it' and its antecedent 'a novel' in: 'John is reading a novel. It ends quite abruptly'), and (ii) the distinction between reference to events/situations and entities/individuals in the real/actual world versus in hypothetical possible worlds. Cross-sentential referential dependencies are disrupted when the antecedent for a pronoun is embedded in a sentence introducing hypothetical entities (e.g. 'John is considering writing a novel. It ends quite abruptly'). An earlier event-related potential reading study showed such disruptions yielded a P600-like frontal positivity. Here we replicate this effect using auditorily presented sentences and discuss the implications for our understanding of discourse-level language processing.

The neural underpinnings of semantic ambiguity and anaphora.

We used event-related brain potentials (ERPs) in order to investigate how definite NP anaphors are integrated into semantically ambiguous contexts. Although sentences such as Every kid climbed a tree lack any syntactic or lexical ambiguity, these structures exhibit two possible meanings, where either many trees or only one tree was climbed. This semantic ambiguity is the result of quantifier scope ambiguity. Previous behavioural studies have shown that a plural definite NP continuation is preferred (as reflected in a continuation sentence, e.g., The trees were in the park) over singular NPs (e.g., The tree was in the park). This study aimed to identify the neurophysiological pattern associated with the integration of the continuation sentences, as well as the time course of this process. We examined ERPs elicited by the noun and verb in continuation sentences following ambiguous and unambiguous context sentences. A sustained negative shift was most evident at the Verb position in sentences exhibiting scope ambiguity. Furthermore, this waveform did not differentiate itself until 900 ms after the presentation of the Noun, suggesting that the parser waits to assign meaning in contexts exhibiting quantifier scope ambiguity, such that such contexts are left as underspecified representations.

An electrophysiological study of mood, modal context, and anaphora.

We investigated whether modal information elicited empirical effects with regard to discourse processing. That is, like tense information, one of the linguistic factors shown to be relevant in organizing a discourse representation is modality, where the mood of an utterance indicates whether or not it is asserted. Event-related potentials (ERPs) were used in order to address the question of the qualitative nature of discourse processing, as well as the time course of this process. This experiment investigated pronoun resolution in two-sentence discourses, where context sentences either contained a hypothetical or actual Noun Phrase antecedent. The other factor in this 2x2 experiment was type of continuation sentence, which included or excluded a modal auxiliary (e.g., must, should) and contained a pronoun. Intuitions suggest that hypothetical antecedents followed by pronouns asserted to exist present ungrammaticality, unlike actual antecedents followed by such pronouns. Results confirmed the grammatical intuition that the former discourse displays anomaly, unlike the latter (control) discourse. That is, at the Verb position in continuation sentences, we found frontal positivity, consistent with the family of P600 components, and not an N400 effect, which suggests that the anomalous target sentences caused a revision in discourse structure. Furthermore, sentences exhibiting modal information resulted in negative-going waveforms at other points in the continuation sentence, indicating that modality affects the overall structural complexity of discourse representation.

Neural substrates of linguistic prosody: evidence from syntactic disambiguation in the productions of brain-damaged patients.

The present investigation focussed on the neural substrates underlying linguistic distinctions that are signalled by prosodic cues. A production experiment was conducted to examine the ability of left- (LHD) and right- (RHD) hemisphere-damaged patients and normal controls to use temporal and fundamental frequency cues to disambiguate sentences which include one or more Intonational Phrase level prosodic boundaries. Acoustic analyses of subjects' productions of three sentence types-parentheticals, appositives, and tags-showed that LHD speakers, compared to RHD and normal controls, exhibited impairments in the control of temporal parameters signalling phrase boundaries, including inconsistent patterns of pre-boundary lengthening and longer-than-normal pause durations in non-boundary positions. Somewhat surprisingly, a perception test presented to a group of normal native listeners showed listeners experienced greatest difficulty in identifying the presence or absence of boundaries in the productions of the RHD speakers. The findings support a cue lateralization hypothesis in which prosodic domain plays an important role.

Sensitivity to prosodic structure in left- and right-hemisphere-damaged individuals.

An experiment was conducted in order to determine whether left- (LHD) and right-hemisphere-damaged (RHD) patients exhibit sensitivity to prosodic information that is used in syntactic disambiguation. Following the work of, a cross-modal lexical decision task was performed by LHD and RHD subjects, as well as by adults without brain pathology (NC). Subjects listened to sentences with attachment ambiguities with either congruent or incongruent prosody, while performing a visual lexical decision task. Results showed that each of the unilaterally damaged populations differed from each other, as well as from the NCs in terms of sensitivity regarding prosodic cues. Specifically, the RHD group was insensitive to sentence prosody as a whole. This was in contrast to the LHD patients, who responded to the prosodic manipulation, but in the unexpected direction. Results are discussed in terms of current hypotheses regarding the hemispheric lateralization of prosodic cues.