The Benefit of Scene-Like Interactions on Object Identification Arises in LO Rather than Being a Consequence of Parietal Attentional Modulation

Abstract

Our visual experience is generally not of isolated objects, but of scenes, where multiple objects are interacting. Such interactions (e.g., a watering can positioned to pour water onto a plant) have been shown to facilitate object identification compared to when the objects are depicted as not interacting (e.g., a watering can positioned so that it is pouring away from the plant) (Green & Hummel, 2006). Where is the neural locus for this advantage? The lateral occipital cortex (LO), the first cortical region where intact shape is distinguished from texture (Malach et al., 1995; Cant & Goodale, 2007), is the same area that shows greater responses to object pairs depicted as interacting compared to when they are not interacting (Kim & Biederman, in press; Roberts & Humphreys, 2010). However it is possible that the intraparietal sulcus (IPS), engaged by attentional demands (e.g., Kanwisher & Wojciulik, 2000), modulates the activity in LO. To test this hypothesis, we delivered transcranial magnetic stimulation (TMS) to LO and IPS while subjects detected a target object that was or was not interacting with another object to form a scene. TMS delivered to LO but not IPS abolished the facilitation of object identification for interacting objects compared to non-interacting depictions observed in the absence of TMS, suggesting that it is LO and not IPS that is critical in the coding object interactions.