Poster B38, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Dissociating activation and integration of discourse referents: Evidence from ERPs and oscillations
Cas Coopmans1,2, Mante Nieuwland1,3;1Max Planck Institute for Psycholinguistics, 2Centre for Language Studies, Nijmegen, 3Donders Institute for Brain, Cognition and Behaviour
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 from a representation of the discourse, and the subsequent integration of this antecedent into the unfolding representation of the narrated event (e.g. Garrod & Terras, 2000). The neural implementation of these two processes is unknown, but a recent proposal suggests that they draw upon the brain’s recognition memory and language networks, respectively, and may be dissociable in patterns of neural oscillatory synchronization (Nieuwland & Martin, 2017). Following up on this proposal, the current EEG study with pre-registered analyses examines whether referent activation and integration can be disentangled by event-related potentials (ERPs) and by activity in the theta and gamma frequency bands. Forty Dutch participants read two-sentence mini stories containing proper names. We investigated referent activation and integration in a two-by-two factorial design by separately manipulating whether the proper name in the second sentence was repeated or new (ease of activation) and whether it rendered the target sentence coherent or incoherent with the preceding discourse (ease of integration). Analyses of ERPs (N400, Late Positive Component) and oscillations (theta, gamma) were time-locked to the onset of the proper name in the second sentence. We found that repeated names elicited lower N400 and LPC amplitude than new names, and they elicited an increase in theta-band (4-7 Hz) synchronization compared to new names, which was largest around 300-500 ms after name onset. Discourse coherence was not accompanied by modulations of either the N400 or the LPC, but discourse-coherent proper names elicited an increase in gamma-band (60-80 Hz) synchronization around 500-1000 ms compared to discourse-incoherent ones. Beamformer source analysis localized this gamma-band effect to the left frontal cortex. In line with the predictions of Nieuwland and Martin (2017), our findings show that activation and integration of discourse referents can indeed be dissociated in event-related EEG activity. Processes related to referent activation are reflected in N400, LPC and theta activity, while integration processes modulate gamma activity. We suggest that the N400 effect reflects facilitated activation of the repeated name. In line with the recognition memory literature (Jacobs et al., 2006; Chen & Caplan, 2017), we take the increase in theta-band synchronization to reflect a successful match between anaphor and antecedent. The gamma-band effect, which originated from left frontal areas, likely reflects integration of this antecedent into a meaningful discourse representation (Bastiaansen & Hagoort, 2006, 2015). In all, our results show that analyses of ERPs and oscillations provide complementary views on the processes underlying anaphor comprehension. In addition, they further emphasize the importance of memory processes, possibly mediated by theta oscillations, in online language comprehension.
Themes: Meaning: Discourse and Pragmatics, Meaning: Lexical Semantics
Method: Electrophysiology (MEG/EEG/ECOG)