The Role Of Frontal Eye Fields In The Inhibitory Tagging Mechanism: A Study With Transcranial Magnetic Stimulation

The Inhibitory Tagging Mechanism has been proposed as the system responsible for impeding the reorientation of attention to previously visited locations or items. Accumulating evidence suggests that its neural underpinnings are located in the Frontal Eye Field (FEF) neurons in mammals. In the present study, we aimed to investigate the nature of this phenomenon which was elicited using the Multi-Item Localization (MILO) Task. The MILO task is a visual search task whereby participants are asked to select, according to a given order, a number of targets in sequence. Selection can occur via tapping on a screen or clicking with a mouse, and the order is typically given by increasing numbers (e.g. from 1 to 8) attached to each target item. There are two conditions: in one condition each item disappears upon selection (Vanish), in the other condition no item disappears upon selection (Remain). Serial reaction times (SRTs), that is the times needed to select each successive item in the sequence, are measured. Previous studies have demonstrated that SRTs decrease with increasing selected target items in the sequence for both the Vanish and Remain conditions. For the Vanish condition this can be explained by a decrease in set size with increasing target number, whereas for the Remain condition this indicates the presence of inhibitory tagging. By reducing the cortical excitability of FEF using offline 1Hz Transcranial Magnetic Stimulation (TMS), we expect to observe a divergent pattern between the curves describing SRT as a function of target number for the Vanish and Remain conditions.