Abstract
During monitoring of the discourse, the detection of the relevance of incoming lexical information could be critical for its incorporation to update mental representations in memory. Because, in these situations, the relevance for lexical information is defined by abstract rules that are maintained in memory, a central aspect to elucidate is how an abstract level of knowledge maintained in mind mediates the detection of the lower-level semantic information. In the present study, we propose that neuronal oscillations participate in the detection of relevant lexical information, based on “kept in mind” rules deriving from more abstract semantic information. We tested our hypothesis using an experimental paradigm that restricted the detection of relevance to inferences based on explicit information, thus controlling for ambiguities derived from implicit aspects. We used a categorization task, in which the semantic relevance was previously defined based on the congruency between a kept in mind category (abstract knowledge), and the lexical semantic information presented. Our results show that during the detection of the relevant lexical information, phase synchronization of neuronal oscillations selectively increases in delta and theta frequency bands during the interval of semantic analysis. These increments occurred irrespective of the semantic category maintained in memory, had a temporal profile specific for each subject, and were mainly induced, as they had no effect on the evoked mean global field power. Also, recruitment of an increased number of pairs of electrodes was a robust observation during the detection of semantic contingent words. These results are consistent with the notion that the detection of relevant lexical information based on a particular semantic rule, could be mediated by increasing the global phase synchronization of neuronal oscillations, which may contribute to the recruitment of an extended number of cortical regions.
Highlights
Executive functions have a critical role in supporting language
Despite the fact that our hypothesis concerns the physiological mechanisms accounting for the interaction between different levels of knowledge in the natural language condition, in the present work we decided to reduce the study to a controlled condition
Because phase synchronization may allow the strengthening of the functional coupling, we predict that: (i) while the semantic information is being decoded, functional bridges are established with frontal areas to detect the relevance of information, (ii) when the semantic relevance of words is detected, these established phase synchronizations selectively increase, probably recruiting new cortical areas
Summary
Executive functions have a critical role in supporting language. It has been proposed that these functions are important for language appearance during evolution (Aboitiz and García, 1997; Aboitiz, 2012), for language acquisition (Baddeley, 1992), and for its normal use (Gibson, 1998; Caplan and Waters, 1999), allowing the coordination of sensory and semantic processes across time and accommodating moment-by-moment shifts in goals and strategies (Binder et al, 1997; Smith et al, 1998). From the combinatorial operations that assemble the basic components (lexical semantic units) into larger structures – a process named “unification” (Hagoort, 2005) – additional information is created and maintained that, in turn, is used to monitor new lexical material. This more abstract level of knowledge, or propositional semantics (Givón, 1995), generates rules that dynamically set the relevance for processed words (Sperber and Wilson, 1987, 1995, 2004), based on its own semantic information. It becomes fundamental to understand how the contingent lexical information is detected and incorporated, when it is based on a more abstract semantic representation
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