Parietal alpha stimulation causally enhances attentional information coding in evoked and oscillatory activity

Background

Selective attention is a fundamental cognitive mechanism that allows people to prioritise task-relevant information while ignoring irrelevant information. Previous research has suggested key roles of parietal event-related potentials (ERPs) and alpha oscillatory responses in attention tasks. However, the informational content of these signals is less clear, and their causal effects on the coding of multiple task elements are yet unresolved.

Objective

To test the causal roles of alpha oscillations and ERPs in coding different types of attentional information (where to attend, what to attend to, and features of the visual stimulus).

Methods

We first used EEG to examine the temporal dynamics of alpha oscillations and ERPs in coding attentional information. Then, we applied rhythmic-TMS (rh-TMS) at individual alpha frequency over the right intraparietal sulcus (IPS), while concurrently measuring EEG, to causally manipulate parietal alpha power and ERPs and investigate their roles in coding multiple task features in a selective attention task.

Results

EEG-only data suggested that ERPs coded all three types of task-relevant information with distinct temporal dynamics, while alpha oscillations carried information regarding both where to attend and what to attend to. TMS-EEG results indicated that, compared to arrhythmic-TMS, alpha rh-TMS increased alpha power and inter-trial phase coherence and yielded more negative posterior-contralateral ERPs. Moreover, alpha rh-TMS specifically and causally improved multivariate decoding of information about where to attend (but not what to attend to or visual feature information) during task performance, with decoding improvements predicting changes in behavioural performance.

Conclusions

These findings illuminate the dynamics with which the complementary aspects of a selective attention task are encoded in evoked and oscillatory brain activity. Moreover, they reveal a specific and causal role of IPS-controlled evoked and oscillatory activity in carrying behaviour-driving information exclusively about where to focus attention.