Haptic-Motor Transformations for the Control of Finger Position

Shibata, Daisuke; Choi, Jason Y.; Laitano, Juan C.; Santello, Marco

doi:10.1371/journal.pone.0066140

Cited by 8 publications

(13 citation statements)

References 44 publications

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“…[ 17 , 55 ]). This method also avoids potential problems when reporting with the contralateral hand [ 4 , 56 ].…”

Section: Methodsmentioning

confidence: 99%

“…Grasping is an important human sensorimotor function which is finely controlled. Our sensorimotor system easily incorporates novel grasped objects with a wide range of sizes and weights into our working ‘space’ [ 1 ] and we seamlessly alter digit placement and force on a grasped object depending on the task [ 2 – 4 ]. The ability to grasp, lift and manipulate objects involves complex movements of many joints and contraction of multiple muscles (e.g.…”

Section: Introductionmentioning

confidence: 99%

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How Weight Affects the Perceived Spacing between the Thumb and Fingers during Grasping

2015

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We know much about mechanisms determining the perceived size and weight of lifted objects, but little about how these properties of size and weight affect the body representation (e.g. grasp aperture of the hand). Without vision, subjects (n = 16) estimated spacing between fingers and thumb (perceived grasp aperture) while lifting canisters of the same width (6.6cm) but varied weights (300, 600, 900, and 1200 g). Lifts were performed by movement of either the wrist, elbow or shoulder to examine whether lifting with different muscle groups affects the judgement of grasp aperture. Results for perceived grasp aperture were compared with changes in perceived weight of objects of different sizes (5.2, 6.6, and 10 cm) but the same weight (600 g). When canisters of the same width but different weights were lifted, perceived grasp aperture decreased 4.8% [2.2 ‒ 7.4] (mean [95% CI]; P < 0.001) from the lightest to the heaviest canister, no matter how they were lifted. For objects of the same weight but different widths, perceived weight decreased 42.3% [38.2 ‒ 46.4] from narrowest to widest (P < 0.001), as expected from the size-weight illusion. Thus, despite a highly distorted perception of the weight of objects based on their size, we conclude that proprioceptive afferents maintain a reasonably stable perception of the aperture of the grasping hand over a wide range of object weights. Given the small magnitude of this ‘weight-grasp aperture’ illusion, we propose the brain has access to a relatively stable ‘perceptual ruler’ to aid the manipulation of different objects.

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“…[ 17 , 55 ]). This method also avoids potential problems when reporting with the contralateral hand [ 4 , 56 ].…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

How Weight Affects the Perceived Spacing between the Thumb and Fingers during Grasping

2015

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“…Such a contact event (mechanical vibration and pressure change) could be encoded in the tactile afferent signals conveying precise timing information (Johansson and Birznieks 2004). The second source of feedback could result from integrating tactile and proprioceptive signals associated with changes in fingertip distance when contacting a small vs. large object (Santello and Soechting 1997;Shibata et al 2013). It should be pointed out that the earlier force differentiation as a function of object width found for the vision condition does not rule out the possibility that the vision group also might have used haptic feedback to adjust digit forces.…”

Section: Execution Of Dexterous Manipulation: Digit Contact Event Andmentioning

confidence: 99%

Coordination between digit forces and positions: interactions between anticipatory and feedback control

Santello

2014

Journal of Neurophysiology

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Humans adjust digit forces to compensate for trial-to-trial variability in digit placement during object manipulation, but the underlying control mechanisms remain to be determined. We hypothesized that such digit position/force coordination was achieved by both visually guided feed-forward planning and haptic-based feedback control. The question arises about the time course of the interaction between these two mechanisms. This was tested with a task in which subjects generated torque (± 70 N·mm) on a virtual object to control a cursor moving to target positions to catch a falling ball, using a virtual reality environment and haptic devices. The width of the virtual object was varied between large (L) and small (S). These object widths result in significantly different horizontal digit relative positions and require different digit forces to exert the same task torque. After training, subjects were tested with random sequences of L and S widths with or without visual information about object width. We found that visual cues allowed subjects to plan manipulation forces before contact. In contrast, when visual cues were not available to predict digit positions, subjects implemented a "default" digit force plan that was corrected after digit contact to eventually accomplish the task. The time course of digit forces revealed that force development was delayed in the absence of visual cues. Specifically, the appropriate digit force adjustments were made 250-300 ms after initial object contact. This result supports our hypothesis and further reveals that haptic feedback alone is sufficient to implement digit force-position coordination.

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“…We used a 10-s delay between the “perceive and memorize” and “match” phase in our previous work to ensure memory formation (Shibata et al, 2013). We used the same delay in the present study to allow comparison with our previous work.…”

Section: Methodsmentioning

confidence: 99%

“…To understand the sensorimotor transformations responsible for the above phenomenon of digit position-force coordination, our previous study examined subjects’ ability to match the remembered relative vertical distance between the center of pressure (CoP) of thumb and index finger pads without visual feedback of the hand (Shibata et al, 2013 ). This study revealed that sensorimotor transformations are more accurate for (a) larger vertical separations between the digits’ CoP; and (b) when fingertips’ vertical distance is reproduced with the same hand and at the same posture as those used when sensing the fingertip distance.…”

Section: Introductionmentioning

confidence: 99%

Digit forces bias sensorimotor transformations underlying control of fingertip position

Shibata

Kappers

Santello

2014

Front. Hum. Neurosci.

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Humans are able to modulate digit forces as a function of position despite changes in digit placement that might occur from trial to trial or when changing grip type for object manipulation. Although this phenomenon is likely to rely on sensing the position of the digits relative to each other and the object, the underlying mechanisms remain unclear. To address this question, we asked subjects (n = 30) to match perceived vertical distance between the center of pressure (CoP) of the thumb and index finger pads (dy) of the right hand (“reference” hand) using the same hand (“test” hand). The digits of reference hand were passively placed collinearly (dy = 0 mm). Subjects were then asked to exert different combinations of normal and tangential digit forces (Fn and Ftan, respectively) using the reference hand and then match the memorized dy using the test hand. The reference hand exerted Ftan of thumb and index finger in either same or opposite direction. We hypothesized that, when the tangential forces of the digits are produced in opposite directions, matching error (1) would be biased toward the directions of the tangential forces; and (2) would be greater when the remembered relative contact points are matched with negligible digit force production. For the test hand, digit forces were either negligible (0.5–1 N, 0 ± 0.25 N; Experiment 1) or the same as those exerted by the reference hand (Experiment 2).Matching error was biased towards the direction of digit tangential forces: thumb CoP was placed higher than the index finger CoP when thumb and index finger Ftan were directed upward and downward, respectively, and vice versa (p < 0.001). However, matching error was not dependent on whether the reference and test hand exerted similar or different forces. We propose that the expected sensory consequence of motor commands for tangential forces in opposite directions overrides estimation of fingertip position through haptic sensory feedback.

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Haptic-Motor Transformations for the Control of Finger Position

Cited by 8 publications

References 44 publications

How Weight Affects the Perceived Spacing between the Thumb and Fingers during Grasping

How Weight Affects the Perceived Spacing between the Thumb and Fingers during Grasping

Coordination between digit forces and positions: interactions between anticipatory and feedback control

Digit forces bias sensorimotor transformations underlying control of fingertip position

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