Abstract
When we grasp an object using one hand, the opposite hemisphere predominantly guides the motor control of grasp movements (Davare et al., 2007; Rice et al., 2007). However, it is unclear whether visual object analysis for grasp control relies more on inputs (a) from the contralateral than the ipsilateral visual field, (b) from one dominant visual field regardless of the grasping hand, or (c) from both visual fields equally. For bimanual grasping of a single object we have recently demonstrated a visual field preference for the left visual field (Le and Niemeier, 2013a,b), consistent with a general right-hemisphere dominance for sensorimotor control of bimanual grasps (Le et al., 2014). But visual field differences have never been tested for unimanual grasping. Therefore, here we asked right-handed participants to fixate to the left or right of an object and then grasp the object either with their right or left hand using a precision grip. We found that participants grasping with their right hand performed better with objects in the right visual field: maximum grip apertures (MGAs) were more closely matched to the object width and were smaller than for objects in the left visual field. In contrast, when people grasped with their left hand, preferences switched to the left visual field. What is more, MGA scaling with the left hand showed greater visual field differences compared to right-hand grasping. Our data suggest that, visual object analysis for unimanual grasping shows a preference for visual information from the ipsilateral visual field, and that the left hemisphere is better equipped to control grasps in both visual fields.
Highlights
Vision plays a crucial role in the sensorimotor control of actions
EXPERIMENT 1: RIGHT-HAND GRASPING Grasping trajectories showed a maximum grip apertures (MGAs) during the second half of the movement (∼66% of total movement time), which resembled the typical trajectories for unimanual grasping (Figure 2; see Jeannerod, 1984; Tresilian and Stelmach, 1997; Castiello, 2005)
Visual field effects on the MGA of reach-to-grasp movements To see whether the metrics of grasping movements were influenced by visual field, we studied four measures related to MGA for the two visual fields separately: MGA scaling, absolute and proportional MGA size, and MGA variability
Summary
Vision plays a crucial role in the sensorimotor control of actions. To grasp an object, the brain may analyze visual input to estimate grasp-relevant object features. Grasp movements originate from visuomotor control mechanisms that are computed by a cortical network in the inferior frontal and intraparietal cortex (Castiello, 2005; Castiello and Begliomini, 2008; Grafton, 2010; Davare et al, 2011). The hub of this dorsolateral network is the anterior intraparietal sulcus (aIPS; Culham et al, 2003; Frey et al, 2005) which has been shown to implement the initial steps of the visual analysis for grasps (Rizzolatti and Luppino, 2001; Tunik et al, 2005, 2008; Culham and Valyear, 2006; Castiello and Begliomini, 2008; Grafton, 2010; Le et al, 2014) as well as perform ensuing transformations for visuomotor control (Castiello, 2005; Davare et al, 2007, 2010; Cavina-Pratesi et al, 2010; Koch et al, 2010; Monaco et al, 2013; Theys et al, 2013)
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