Effects of Visual Cues of Object Density on Perception and Anticipatory Control of Dexterous Manipulation

Anticipatory force planning during grasping is based on visual cues about the object’s physical properties and sensorimotor memories of previous actions with grasped objects. Vision can be used to estimate object mass based on the object size to identify and recall sensorimotor memories of previously manipulated objects. It is not known whether subjects can use density cues to identify the object’s center of mass (CM) and create compensatory moments in an anticipatory fashion during initial object lifts to prevent tilt. We asked subjects (n = 8) to estimate CM location of visually symmetric objects of uniform densities (plastic or brass, symmetric CM) and non-uniform densities (mixture of plastic and brass, asymmetric CM). We then asked whether subjects can use density cues to scale fingertip forces when lifting the visually symmetric objects of uniform and non-uniform densities. Subjects were able to accurately estimate an object’s center of mass based on visual density cues. When the mass distribution was uniform, subjects could scale their fingertip forces in an anticipatory fashion based on the estimation. However, despite their ability to explicitly estimate CM location when object density was non-uniform, subjects were unable to scale their fingertip forces to create a compensatory moment and prevent tilt on initial lifts. Hefting object parts in the hand before the experiment did not affect this ability. This suggests a dichotomy between the ability to accurately identify the object’s CM location for objects with non-uniform density cues and the ability to utilize this information to correctly scale their fingertip forces. These results are discussed in the context of possible neural mechanisms underlying sensorimotor integration linking visual cues and anticipatory control of grasping

The effect of the “rod-and-frame” illusion on grip planning in a sequential object manipulation task

We investigated the effect of visual context (i.e., a visual illusion) on the planning of a sequential object manipulation task. Participants (n = 13) had to grasp a rod embedded in a “rod-and-frame” illusion and insert the rod-end into a tight hole in a pre-defined way. The grip type (defined by start posture, either pronated or supinated; and end posture, either comfortable or uncomfortable) used to grasp the rod was registered as a macroscopic variable of motor planning. Different rod orientations forced the participants to switch between grip types. As expected, most participants switched between pronated and supinated start postures, such that they ended the movement with a comfortable end posture. As it has been argued that planning is dependent on visual context information, we hypothesized that the visual illusion would affect the specific rod orientation at which participants would switch into a different grip type. This hypothesis was confirmed. More specifically, the illusion affected the critical spatial information that is used for action planning. Collectively, these findings are the first to show an effect of an illusion on motor planning in a sequential object manipulation task

Ontwikkeling van www.kindexpert.nl

Door middel van deze presentatie wordt de ontwikkeling van Kindexpert.nl besproken met de onderzoekers van Integraal Jeugdbeleid

Mijlpalen-app

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Symposium 'Zorg op maat voor prematuur geboren kinderen'

Lancering KindexpertTijdens het slotsymposium van het project Tailored care for preterm infants (SIA RAAK) is de website Kindexpert.nl gelanceerd. Het symposium is goed bezocht door psychologen, logopedisten en verpleegkundigen

www.kindexpert.nl

Tijdens het slotsymposium van het project Tailored care for preterm infants (SIA RAAK) is de website Kindexpert.nl gelanceerd. Het symposium is goed bezocht door psychologen, logopedisten en verpleegkundigen.Deze presentatie gaat in op vragen die ouders hebben over de ontwikkeling van hun prematuur geboren kind. Deze vraagarticulatie heeft als basis gediend voor de ontwikkeling van Kindexpert.nl. De presentatie is gehouden voor collega’s in Montreal en is onderdeel van het project Tailored care for preterm infants (SIA RAAK)