Cognitive neuroscience and neuropsychology 913 Grasping actions remap peripersonal space Claudio Brozzoli a,b , Francesco Pavani c,d , Christian Urquizar a , Lucilla Cardinali a,b and Alessandro Farne ` a,b The portion of space that closely surrounds our body parts is termed peripersonal space, and it has been shown to be represented in the brain through multisensory processing systems. Here, we tested whether voluntary actions, such as grasping an object, may remap such multisensory spatial representation. Participants discriminated touches on the hand they used to grasp an object containing task-irrelevant visual distractors. Compared with a static condition, reach-to-grasp movements increased the interference exerted by visual distractors over tactile targets. This remapping of multisensory space was triggered by action onset and further enhanced in real time during the early action execution phase. Additional experiments showed that this phenomenon is hand-centred. These results provide the first evidence of a functional link between voluntary object-oriented actions and multisensory coding of the space around us. NeuroReport 20:913–917  c 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins. NeuroReport 2009, 20:913–917 Keywords: bimodal neurons, cross-modal congruency effect, grasping, kinematics, motor control, multisensory, peripersonal space a INSERM UMR-S 864 ‘Espace et Action’, Bron, b Universite ´ Claude Bernard Lyon I, Lyon, France, c Department of Cognitive Sciences and Education and d Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy Correspondence to Claudio Brozzoli, INSERM, 16, avenue du Doyen Le ´ pine, Lyon 69002, France Tel: + 33 472 913420; fax: + 33 472 913401; e-mail: claudio.brozzoli@inserm.fr; alessandro.farne@inserm.fr Received 13 March 2009 accepted 24 March 2009 Introduction The representation of the space near the body, termed ‘peripersonal’ space (PpS) [1,2], relies on multisensory processing, both in human and non-human primates. In monkeys, bimodal neurons in parieto-frontal and sub- cortical structures code for tactile events on a body part (e.g. the hand) and visual events near that body part, thus giving rise to body-centred representations of PpS [3–6]. In humans, a functionally homologous coding of PpS is largely supported by behavioural studies showing stronger visuotactile interaction in near rather than far space in brain-damaged [7–9] and healthy individuals [10–13]. For example, visual events occurring in the immediate proximity to the body induce more severe tactile extinction than farther ones [7–9]. Recent func- tional neuroimaging studies further support the exis- tence of similar multisensory integrative structures in the human brain [11–13]. Despite the large body of knowledge accumulated across species on the multisensory properties of PpS, little is known about its function, and this issue has never been directly assessed in humans. By acting as an anticipatory sensorimotor interface, PpS may serve early detection of potential threats approaching the body to drive in- voluntary defensive movements [3]. The same antici- patory feature, however, may also have evolved to serve voluntary object-oriented actions [1,2,14]. Here, we tested the latter hypothesis by assessing the effects of grasping objects on the multisensory coding of PpS. In Experiment 1, we modified a cross-modal paradigm [10], whereby participants indicate the elevation (up or down) of a tactile target delivered to a finger (index or thumb), while a visual distractor is presented at either congruent or incongruent elevation (Fig. 1). We then con- ducted three experiments in which participants were additionally required to grasp the object in which the visual distractors were embedded. Although the percep- tual task was always performed on the right hand, the motor task was performed by either the right (Experi- ments 2 and 4) or left (Experiment 3) hand. This simple manipulation is crucial in two respects: it equalizes attentional demands for the target object in the sti- mulated and the nonstimulated hand actions, and it allows assessing whether any modulation of multisensory processing is hand-centred. Experimental procedures Participants Fifteen healthy participants (nine men, mean age 27 ± 5 years) took part in Experiments 1, 19 (10 men, mean age 26 ± 6 years) in Experiments 2 and 3, and 16 (8 male, mean age 25 ± 3) in Experiment 4. All gave their verbal informed consent to take part in this study, approved by the local INSERM Ethics Board. Supplementary data are available at The NeuroReport Online (http://links.lww.com/ A1251; http://links.lww.com/A1250; http://links.lww.com/A1249; http://links.lww. com/A1248; http://links.lww.com/A1247; http://links.lww.com/A1246) 0959-4965  c 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/WNR.0b013e32832c0b9b