Presentation

Friederike Contier¹, Mathias Weymar¹, Isabell Wartenburger¹, Milena Rabovksy¹; ¹University of Potsdam, Germany

The P600 event-related component is elicited by a wide range of anomalies in the linguistic input, such as structural violations, ambiguities, and semantically deviant words. The component is traditionally interpreted as a signal of specific linguistic combinatorial operations and continues to inform neurocognitive models of language comprehension (e.g., Kuperberg, 2021, Top. Cogn. Sci.). However, the P600 – just like the earlier domain-general P3 – has alternatively been proposed to signal phasic norepinephrine (NE) release from the locus coeruleus (LC) to salient and relevant stimuli more generally (e.g., Bornkessel-Schlesewsky & Schlesewsky, 2019, Front. Psychol.). Indeed, the P600 mirrors the LC/NE phasic response in that its latency is response-aligned (Sassenhagen & Bornkessel-Schlesewsky, 2015, Cortex) and its amplitude covaries with pupil size (Contier et al., in prep). To complement this correlational evidence, we plan to further test the link between the P600 and NE release by applying non-invasive auricular transcutaneous vagus nerve stimulation (taVNS; Farmer et al., 2021, Front. Hum. Neurosci.), which likely affects activation of the LC/NE system. 40 Participants will come to the lab for two experimental sessions, one for each stimulation condition (order counterbalanced). In both sessions, participants will perform a sentence processing task, in which they read sentences word by word with either morphosyntactic violations, semantic violations, or correct control sentences. During the entire task, they will receive either continuous stimulation at the cymba conchae (an area exclusively innervated by the auricular branch of the vagus nerve, experimental condition) or the ear lobe (sham condition). If the P600 is linked to NE release from the LC, its amplitude should be larger under vagus than sham stimulation. Additionally, we will administer a non-linguistic oddball task in both sessions with the same stimulation manipulation in order to replicate the effect of taVNS on the P3 (Ventura-Bort et al., 2018, Front. Hum. Neurosci.). Finally, to test the specificity of the effects, we will test whether the stimulation also has an effect on the N400 in the semantically violated sentences. As a manipulation check, we will additionally assess two putative biomarkers of NE: salivary alpha-amylase levels and baseline pupil size. The study has been preregistered on OSF, data collection is ready to start, and we expect to present preliminary results at the 2022 SNL meeting. The results of this study will contribute to our understanding of the neurobiological basis of the P600 ERP component. An effect of taVNS on the P600 and P3 amplitude would further support the idea that both ERP components might rely on a shared neural generator and, more specifically, that they may both be linked to phasic NE release.

Topic Areas: Control, Selection, and Executive Processes, Syntax