Abstract
Gamma-band neuronal synchronization during sentence-level language comprehension has previously been linked with semantic unification. Here, we attempt to further narrow down the functional significance of gamma during language comprehension, by distinguishing between two aspects of semantic unification: successful integration of word meaning into the sentence context, and prediction of upcoming words. We computed event-related potentials (ERPs) and frequency band-specific electroencephalographic (EEG) power changes while participants read sentences that contained a critical word (CW) that was (1) both semantically congruent and predictable (high cloze, HC), (2) semantically congruent but unpredictable (low cloze, LC), or (3) semantically incongruent (and therefore also unpredictable; semantic violation, SV). The ERP analysis showed the expected parametric N400 modulation (HC < LC < SV). The time-frequency analysis showed qualitatively different results. In the gamma-frequency range, we observed a power increase in response to the CW in the HC condition, but not in the LC and the SV conditions. Additionally, in the theta frequency range we observed a power increase in the SV condition only. Our data provide evidence that gamma power increases are related to the predictability of an upcoming word based on the preceding sentence context, rather than to the integration of the incoming word’s semantics into the preceding context. Further, our theta band data are compatible with the notion that theta band synchronization in sentence comprehension might be related to the detection of an error in the language input.
Highlights
The term semantic unification refers to the integration of lexically retrieved semantic information into a representation of multiword utterances, as well as the integration of meaning extracted from non-linguistic modalities (Hagoort, 2005; see Baggio and Hagoort, 2011)
In this paper we present evidence that further specifies the functional significance of the reactivity of gamma-band activity in the context of language comprehension processes
Visual inspection showed that the semantic violations (SVs) condition elicited the largest N400 amplitude, while the high cloze (HC) condition elicited the smallest N400 amplitude
Summary
The term semantic unification (in the sense implied by, e.g., Jackendoff, and the related computational model by Vosse and Kempen; Vosse and Kempen, 2000; Jackendoff, 2007, which differs from Shieber’s use that relates to constraint-based lexicalist grammars; Shieber, 1985) refers to the integration of lexically retrieved semantic information into a representation of multiword utterances, as well as the integration of meaning extracted from non-linguistic modalities (Hagoort, 2005; see Baggio and Hagoort, 2011). The process of semantic unification has been studied extensively by means of the N400 component of the event-related potential (ERP; for review, see Lau et al, 2008; Kutas and Federmeier, 2011). From this extensive literature, the notion has emerged that the N400 is related to at least two aspects of semantic unification: semantic integration of words into their preceding context, and the facilitation, based on increased predictability of the upcoming word through the preceding context, of the lexical retrieval of that word. In this paper we present evidence that further specifies the functional significance of the reactivity of gamma-band activity in the context of language comprehension processes
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