RESEARCH ARTICLE Sandhiran Patchay Æ Patrick Haggard Umberto Castiello An object-centred reference frame for control of grasping: effects of grasping a distractor object on visuomotor control Received: 19 July 2004 / Accepted: 29 September 2005 / Published online: 23 November 2005 Ó Springer-Verlag 2005 Abstract Previous evidence based on perceptual inte- gration and arbitrary responses suggests extensive cross-modal links in attention across the various modalities. Attention typically shifts to a common location across the modalities, despite the vast differ- ences in their initial coding of space. An issue that remains unclear is whether or not these effects of multisensory coding occur during more natural tasks, such as grasping and manipulating three-dimensional objects. Using kinematic measures, we found strong effects of the diameter of a grasped distractor object on the aperture used to grasp a target object at both coincident and non-coincident locations. These results suggest that interference effects can occur between proprioceptive and visuomotor signals in grasping. Unlike other interference effects in cross-modal atten- tion, these effects do not depend on the spatial relation between target and distractor, but occur within an object-based frame of reference. Keywords Kinematics Æ Reach to grasp Æ Multisensory information Æ Vision Æ Proprioception Æ Motor control Introduction The view that the senses are interrelated modalities ra- ther than independent channels has been recently sup- ported by several studies providing evidence for common neural and attentional mechanisms for pro- cessing of multisensory information (e.g., Driver and Spence 1999). In these studies, the emphasis was on cross-modal links between combinations of vision, audition and tactile inputs. Most of the research conducted in humans on cross-modal integration has typically focused on per- ceptual integration, and has involved an arbitrary re- sponse, such as reaction time, to a sensory stimulus. However, the study of the effects of multisensory coding during more natural tasks, such as grasping and manipulating three-dimensional objects, is still in its infancy. This is perhaps surprising, given that these manual actions generally involve a complex interplay between vision, proprioception and touch (Castiello 2005). Nevertheless, recent research on multimodal is- sues shows that cross-modal links in motor control are substantial and numerous. Distractor size was previously identified as a key parameter for distractor effects on grasping by Castiello (1996). Gentilucci et al. (1998) used distractor size to investigate cross-modal links between haptic informa- tion and visuomotor control when reaching to grasp a visual target. In their experiments, participants reached and grasped with one hand a visual target (sphere) presented with different sizes, while holding another unseen sphere (distractor) of different sizes on the other hand. These authors found that proprioceptively guided manipulation with the right hand influenced finger shaping of visuomotor grasping with the left hand when the two objects differed in size. They reported an inter- ference effect only for an unseen small distractor object. Moreover, this effect was only seen for a distractor manipulated by the right hand while reaching to grasp an object with the left hand. S. Patchay Æ U. Castiello (&) Department of Psychology, Royal Holloway University of London, London, UK E-mail: umberto.castiello@unipd.it S. Patchay Department of Psychology and Counselling, University of Greenwich, London, UK P. Haggard Institute of Cognitive Neuroscience and Department of Psychology, University College London, London, UK U. Castiello Dipartimento di Psicologia Generale, Universita` di Padova, Via Venezia 8, 35131 Padova, Italy Exp Brain Res (2006) 170: 532–542 DOI 10.1007/s00221-005-0240-6