Temporal dynamics of target selection and distractor suppression mechanisms in the right Frontal Eye Field

The ability of the human brain to selectively attend to relevant information while ignoring irrelevant distraction is essential for the successful completion of everyday tasks. The present PhD project aimed to unravel the temporal dynamics of target selection and distractor suppression in the Frontal Eye Field (FEF), a key node in the dorsolateral attention network. Previous research (Lega et al., 2019) had assessed the contribution of both IPS and FEF to the deployment of visuo- spatial attention by means of 10 Hz TMS during a visual search task. The stimulation was delivered in a post-stimulus epoch from 100 to 300 ms, considered crucial for attentional computations in visual search. This study found that the TMS protocol improved distractor suppression mechanisms, reducing the cost engendered by salient but task-irrelevant distractors. To further clarify the temporal contribution of right FEF to distractor suppression, two experiments were carried out. Experiment 1 applied single-pulse TMS over right FEF at three different time points, 50, 200 or 350 ms after search array onset. Experiment 2 aimed to exert a stronger TMS effect over right FEF while maintaining a temporal-punctate approach. It applied trains of triple-pulse TMS at 20 Hz over right FEF in three different time windows: from -50 to 50 ms (T1), from 100 to 200 ms (T2) and from 250 to 350 ms (T3) after the search array onset. While Experiment 1 showed only a general, time-unspecific and quasi- significant effect of stimulation over response times, Experiment 2 revealed that stimulation at T2 (100-200 ms) was associated with an increase of the distractor cost, specifically for distractors located contralaterally to the stimulation site. These findings support the role of right FEF in suppressing distractions from salient but irrelevant stimuli and suggest that TMS may activate/inhibit the neural network that regulates and limits interference from such distractions. Further research is needed to precisely assess the physiological effects of different TMS protocols of the right FEF and its influence on attentional computation.