Slide Slam M15
The P600, but not the N400, is modulated by sustained attention
Friederike Schütte1, Isabell Wartenburger1, Mathias Weymar1, Milena Rabovsky1; 1University of Potsdam
There are two prominent language related ERP components, the N400 and P600 component, and it’s still debated how exactly they differ in terms of underlying processes during sentence comprehension. It has recently been suggested that one important dimension along which these components vary is in terms of automaticity versus attentional control, with N400 amplitudes reflecting more automatic and P600 amplitudes reflecting more attention dependent aspects of sentence comprehension (Rabovsky & McClelland, 2020, Phil. Trans. B.). Indeed, the P600 correlates with indicators of executive function (Brothers et al., 2021, biorxiv) and is reduced or absent when the task does not require participants to process linguistic anomalies while N400 effects are less task dependent (Schacht et al., 2014, PLoS One). However, besides the direct manipulation of task relevance, more evidence on the role of attention for P600 and N400 amplitudes is still scarce. Generally, the availability of executive resources depends on the degree of sustained attention, which fluctuates over time (Esterman & Rothlein, 2019, Curr Opin Psychol). Thus, if the P600 indeed reflects a controlled process, it should be reduced when sustained attention is low, and thus, less of the necessary executive resources are available. On the other hand, if the N400 indeed reflects an automatic process, its amplitude should not depend on sustained attention. Here, we tested these predictions with a sentence processing paradigm using reaction time variability as an index of sustained attention. We re-analysed EEG and behavioral data from a visual sentence processing task by Sassenhagen & Bornkessel-Schlesewsky (2015, Cortex). Half of the German sentences were correct (Lit: 'To the category fruit belong the pear, the apple, and the mango'). ¼ of the sentences contained a mismatching determiner (morphosyntactic violation) and further ¼ of the sentences contained a hyponym which belonged to a different semantic category (semantic violation). Participants read sentences phrase by phrase and indicated whether a sentence contained any type of anomaly as soon as they had the relevant information. To quantify periods of high versus low sustained attention, we extracted a moving reaction time coefficient of variation over the entire course of the task for each participant (see e.g., Van den Brink et al., 2016, PLoS One). P600 amplitude was significantly larger during periods of low reaction time variability (high sustained attention) than in periods of high reaction time variability (low sustained attention), even when controlling for individual trial reaction time (β = 0.767, SE = 0.322, t = 2.376, χ2 = 5.64, p = .017). In contrast, the amplitude of the N400 was not affected by reaction time variability (β = 0.38, SE = 0.28, t = 1.36, χ2 = 1.85, p = .174). These results thus suggest that the P600 component is sensitive to the current degree of sustained attention while the N400 component is not, which is in line with the idea that P600 amplitudes reflect more controlled and N400 amplitudes more automatic aspects of sentence comprehension (Rabovsky & McClelland, 2020).