A neural oscillatory signature of reference

Nieuwland, M. S. & Martin, A. E.

Department of Psychology, University of Edinburgh

The ability to use words to refer to the world is a vital mechanism that gives human language its communicative power. In particular, the use of words to refer to previously mentioned concepts (anaphora) is what allows dialogue to be coherent and meaningful. Psycholinguistic theory posits that anaphor comprehension involves reactivating a memory representation of the antecedent. Whereas this implies the involvement of episodic memory, the neural processes for reference resolution are largely unknown. Here, we report time-frequency analysis of four EEG experiments to reveal the increased coupling of functional neural systems associated with referring expressions that can be straightforwardly understood compared to those that cannot (referential coherence or ambiguity). Despite varying in modality, language and type of referential expression, all experiments showed larger gamma-band power for coherence compared to ambiguity. In high-density EEG Experiment 4, Beamformer analysis localised this increase to the posterior parietal cortex around 300-500 ms after onset of the anaphor and to frontal-temporal cortex around 500-1000 ms. We argue that the observed gamma-band power increases reflect successful referential binding and resolution, which links incoming information to previously encountered concepts through an interaction between the episodic memory network and the frontal-temporal language network.