Cortical control of inhibition of return: Causal evidence for task-dependent modulations by dorsal and ventral parietal regions

Inhibition of return (IOR) reflects a bias to preferentially attend to non-previously attended or inspected spatial locations. IOR is paramount to efficiently explore our environment, by avoiding repeated scanning of already visited locations. Patients with left visual neglect after right parietal damage or fronto-parietal disconnection demonstrated impaired manual, but not saccadic, IOR for right-sided targets (Bourgeois et al., 2012). Here we aimed at investigating in healthy participants the causal role of distinct cortical sites within the right hemisphere in manual and saccadic IOR, by evaluating the offline effects of repetitive Transcranial Magnetic Stimulation (rTMS) on the right intra-parietal sulcus (IPS) and the right temporo-parietal junction (TPJ). Our results show that rTMS over both sites lastingly interfered with manual but not saccadic IOR for right-sided targets. This behavioral pattern closely mimicked the performance of neglect patients evaluated with the same paradigm. In contrast, for left-sided targets, rTMS over the right IPS impaired both manual and saccadic IOR, while rTMS over the right TPJ produced no modulation in either task. We concluded that distinct parietal nodes of the dorsal and ventral spatial attention networks of the right hemisphere make different contributions to exogenous orienting processes implicated in IOR, and that such effects are hemifield- and task-dependent.