Dissociating activation and integration of discourse referents: evidence from ERPs and oscillations

Abstract

A key challenge in understanding stories and conversations is the comprehension of 'anaphora', words that refer back to previously mentioned words or concepts ('antecedents').In psycholinguistic theories, anaphor comprehension involves the initial activation of the antecedent and its subsequent integration into the unfolding representation of the narrated event.A recent proposal suggests that these processes draw upon the brain's recognition memory and language networks, respectively, and may be dissociable in patterns of neural oscillatory synchronization (Nieuwland & Martin, 2017). We addressed this proposal in an electroencephalogram (EEG) study with pre-registered data acquisition and analyses, using event-related potentials (ERPs) and neural oscillations. Dutch participants read two-sentence mini stories containing proper names, which were repeated or new (ease of activation) and coherent or incoherent with the preceding discourse (ease of integration). Repeated names elicited lower N400 and Late Positive Component amplitude than new names, and also an increase in theta-band (4-7 Hz) synchronization, which was largest around 240-450 ms after name onset. Discourse-coherent proper names elicited an increase in gamma-band (60-80 Hz) synchronization compared to discourse-incoherent names. This effect was largest around 690-1000 ms after name onset and was localized to the left frontal cortex. We argue that the initial activation and subsequent discourse-level integration of referents can be dissociated with eventrelated EEG activity, and are associated with respectively theta-and gamma-band activity.These findings further establish the link between memory and language through neural oscillations.

Distinguishing Old From New Referents During Discourse Comprehension: Evidence From ERPs and Oscillations

“…One study with a similar manipulation did not report any LPC modulation (Yang et al, 2007). And while one recent study with repeated proper name anaphors also reported enhanced LPC for new names (Coopmans and Nieuwland, 2019), two other studies with proper names reported a reverse LPC pattern (Van Petten et al, 1991; Swaab et al, 2004). For example, in a study on natural text comprehension, Van Petten et al (1991) reported enhanced LPC amplitude for repeated proper names compared to novel names, and suggested that these effects reflect the retrieval of semantic information associated with known names 2 .…”

“…In a recent study on comprehension of proper name anaphors, Coopmans and Nieuwland (2019) observed effects in both the theta and gamma frequency range. Their participants read story contexts that described characteristics of two people (e.g., “John and Peter are the best players in the football team”), followed by a target sentence containing a repeated or novel proper name that was either congruent or incongruent with the discourse context (e.g., “The top scorer of the team was John with thirty goals in total”).…”

“…However, definite noun phrases sometimes introduce a new referent (e.g., Heim, 1982; Fraurud, 1990; Garrod et al, 1994; Poesio and Vieira, 1998; Gundel et al, 2001; Pyke, 2007; Pyke et al, 2007a, b), and people can use the semantic content of a definite noun as a basis to introduce a novel referent when required, e.g., ‘the alien’ when the context only mentioned astronauts. This process is sometimes referred to as discourse updating (e.g., Burkhardt, 2006), which is related to, yet distinct from the integration process by which people process discourse-level meaning (e.g., Coopmans and Nieuwland, 2019). In other words, processes involved in noun phrase anaphor resolution must distinguish old from new referents, and may do so partly relying on memory processes (for a review and computational account, see Pyke, 2007).…”

“…Referentially ambiguous anaphors, like ‘the alien’ when two different aliens were mentioned in the context, or the pronoun ‘he’ without a male antecedent in the sentence, elicit a sustained, frontal negativity compared to non-ambiguous anaphors (the Nref effect; for reviews, see Van Berkum et al, 2007; Nieuwland and Van Berkum, 2008b). The Nref effect can start at about 200–300 ms after word onset (not unlike an N400 effect, at least for written language comprehension), and has been obtained with noun phrases (e.g., Van Berkum et al, 1999a, 2003; Nieuwland et al, 2007; Nieuwland and Van Berkum, 2008a), pronouns (e.g., Nieuwland and Van Berkum, 2006; Nieuwland, 2014; Karimi et al, 2018), noun phrase ellipsis (e.g., Martin et al, 2012), and proper names (e.g., Coopmans and Nieuwland, 2019). While the onset latency of the Nref suggests that it indexes processes that rapidly link expressions to potential referents, the sustained nature of this effect suggests that inability to resolve reference may have a prolonged impact on comprehension (see Nieuwland et al, 2007; Nieuwland and Martin, 2017).…”

“…ERPs and oscillatory responses are complementary electrophysiological measures, because whereas ERP analysis can only detect activity that is both time- and phase-locked to stimulus onset, time-frequency analysis can detect activity that is time-locked only 3 . To date, only a handful of studies have applied time-frequency analysis to examine reference processing (Van Berkum et al, 2004; Heine et al, 2006; Boudewyn et al, 2015 4 ; Meyer et al, 2015; Nieuwland and Martin, 2017; Coopmans and Nieuwland, 2019).…”