The influence of object height on maximum grip aperture in empirical and modeled data.

2014 ◽  
Vol 40 (2) ◽  
pp. 889-896 ◽  
Author(s):  
Svenja Borchers ◽  
Rebekka Verheij ◽  
Jeroen B. J. Smeets ◽  
Marc Himmelbach
Keyword(s):  
Grip Aperture ◽  
Maximum Grip Aperture ◽  
Maximum Grip

On the Relation Between Object Shape and Grasping Kinematics

2004 ◽  
Vol 91 (6) ◽  
pp. 2598-2606 ◽  
Author(s):  
Raymond H. Cuijpers ◽  
Jeroen B. J. Smeets ◽  
Eli Brenner
Keyword(s):  
Principal Axis ◽  
Grip Aperture ◽  
Object Shape ◽  
Hand Orientation ◽  
Principal Axes ◽  
Movement Distance ◽  
Maximum Grip Aperture ◽  
The Many ◽  
Elliptical Cylinders ◽  
Maximum Grip

Despite the many studies on the visual control of grasping, little is known about how and when small variations in shape affect grasping kinematics. In the present study we asked subjects to grasp elliptical cylinders that were placed 30 and 60 cm in front of them. The cylinders' aspect ratio was varied systematically between 0.4 and 1.6, and their orientation was varied in steps of 30°. Subjects picked up all noncircular cylinders with a hand orientation that approximately coincided with one of the principal axes. The probability of selecting a given principal axis was the highest when its orientation was equal to the preferred orientation for picking up a circular cylinder at the same location. The maximum grip aperture was scaled to the length of the selected principal axis, but the maximum grip aperture was also larger when the length of the axis orthogonal to the grip axis was longer than that of the grip axis. The correlation between the grip aperture— or the hand orientation—at a given instant, and its final value, increased monotonically with the traversed distance. The final hand orientation could already be inferred from its value after 30% of the movement distance with a reliability that explains 50% of the variance. For the final grip aperture, this was only so after 80% of the movement distance. The results indicate that the perceived shape of the cylinder is used for selecting appropriate grasping locations before or early in the movement and that the grip aperture and orientation are gradually attuned to these locations during the movement.

scholarly journals Are reaching and grasping effector-independent? Similarities and differences in reaching and grasping kinematics between the hand and foot

2021 ◽  
Author(s):  
Yuqi Liu ◽  
James Caracoglia ◽  
Sriparna Sen ◽  
Ella Striem-Amit
Keyword(s):  
Peak Velocity ◽  
Object Size ◽  
Body Parts ◽  
Acceleration Phase ◽  
Grip Aperture ◽  
Deceleration Phase ◽  
Neural Representations ◽  
Maximum Grip Aperture ◽  
Similarities And Differences ◽  
Maximum Grip

While reaching and grasping are highly prevalent manual actions, neuroimaging studies provide evidence that their neural representations may be shared between different body parts, i.e. effectors. If these actions are guided by effector-independent mechanisms, similar kinematics should be observed when the action is performed by the hand or by a cortically remote and less experienced effector, such as the foot. We tested this hypothesis with two characteristic components of action: the initial ballistic stage of reaching, and the preshaping of the digits during grasping based on object size. We examined if these kinematic features reflect effector-independent mechanisms by asking participants to reach toward and to grasp objects of different widths with their hand and foot. First, during both reaching and grasping, the velocity profile up to peak velocity matched between the hand and the foot, indicating a shared ballistic acceleration phase. Secondly, maximum grip aperture and time of maximum grip aperture of grasping increased with object size for both effectors, indicating encoding of object size during transport. Differences between the hand and foot were found in the deceleration phase and time of maximum grip aperture, likely due to biomechanical differences and the participants' inexperience with foot actions. These findings provide evidence for effector-independent visuomotor mechanisms of reaching and grasping that generalize across body parts.

The influence of target object shape on maximum grip aperture in human grasping movements

2014 ◽  
Vol 232 (11) ◽  
pp. 3569-3578 ◽  
Author(s):  
Rebekka Verheij ◽  
Eli Brenner ◽  
Jeroen B. J. Smeets
Keyword(s):  
Target Object ◽  
Grip Aperture ◽  
Object Shape ◽  
Maximum Grip Aperture ◽  
Maximum Grip

scholarly journals Is Grasping Impaired in Hemispatial Neglect?

2002 ◽  
Vol 13 (1-2) ◽  
pp. 17-28 ◽  
Author(s):  
Monika Harvey ◽  
Stephen R. Jackson ◽  
Roger Newport ◽  
Tanja Krämer ◽  
D. Llewlyn Morris ◽  
...  
Keyword(s):  
Right Hemisphere ◽  
Target Object ◽  
Cerebral Stroke ◽  
Hemispatial Neglect ◽  
Grip Aperture ◽  
Maximum Grip Aperture ◽  
Path Curvature ◽  
The Right ◽  
Path Deviation ◽  
Maximum Grip

Patients with right unilateral cerebral stroke, four of which showed acute hemispatial neglect, and healthy aged-matched controls were tested for their ability to grasp objects located in either right or left space at near or far distances. Reaches were performed either in free vision or without visual feedback from the hand or target object. It was found that the patient group showed normal grasp kinematics with respect to maximum grip aperture, grip orientation, and the time taken to reach the maximum grip aperture. Analysis of hand path curvature showed that control subjects produced straighter right hand reaches when vision was available compared to when it was not. The right hemisphere lesioned patients, however, showed similar levels of curvature in each of these conditions. No behavioural differences, though, could be found between right hemisphere lesioned patients with or without hemispatial neglect on either grasp parameters, path deviation or temporal kinematics.

scholarly journals Prehension and Perception of Size in Left Visual Neglect

2002 ◽  
Vol 13 (1-2) ◽  
pp. 3-15 ◽  
Author(s):  
R. D. McIntosh ◽  
C. L. Pritchard ◽  
H. C. Dijkerman ◽  
A. D. Milner ◽  
R. C. Roberts
Keyword(s):  
Right Hemisphere ◽  
Visual Neglect ◽  
Grip Aperture ◽  
Estimation Task ◽  
Deceleration Phase ◽  
Maximum Grip Aperture ◽  
Patient Groups ◽  
Visual Size ◽  
Null Finding ◽  
Maximum Grip

Right hemisphere damaged patients with and without left visual neglect, and age-matched controls had objects of various sizes presented within left or right body hemispace. Subjects were asked to estimate the objects’ sizes or to reach out and grasp them, in order to assess visual size processing in perceptual-experiential and action-based contexts respectively. No impairments of size processing were detected in the prehension performance of the neglect patients but a generalised slowing of movement was observed, associated with an extended deceleration phase. Additionally both patient groups reached maximum grip aperture relatively later in the movement than did controls. For the estimation task it was predicted that the left visual neglect group would systematically underestimate the sizes of objects presented within left hemispace but no such abnormalities were observed. Possible reasons for this unexpected null finding are discussed.

scholarly journals Some illusions are more inconsistent than others

2019 ◽  
Author(s):  
Jeroen B. J. Smeets ◽  
Eli Brenner
Keyword(s):  
Motion Aftereffect ◽  
Apparent Size ◽  
Ebbinghaus Illusion ◽  
Reach To Grasp ◽  
Grip Aperture ◽  
Maximum Grip Aperture ◽  
Pencil And Paper ◽  
Maximum Grip

Illusions are characterized by inconsistencies. For instance, in the motion aftereffect, we see motion without an equivalent change in position. We used a simple pencil-and-paper experiment to determine whether illusions that influence an object’s apparent size give rise to equivalent changes in apparent positions along the object’s outline. We found different results for two equally strong size illusions. The Ebbinghaus illusion affected perceived positions in a way that was consistent with its influence on perceived size, but a modified diagonal illusion did not affect perceived positions. This difference between the illusions might explain why there are so many conflicting reports about the effects of size illusions on the maximum grip aperture during reach-to-grasp movements.

Effect of visual and haptic feedback on grasping movements

2014 ◽  
Vol 112 (12) ◽  
pp. 3189-3196 ◽  
Author(s):  
Chiara Bozzacchi ◽  
Robert Volcic ◽  
Fulvio Domini
Keyword(s):  
Visual Feedback ◽  
Haptic Feedback ◽  
Block Design ◽  
Three Dimensional ◽  
Tactile Feedback ◽  
Hand Position ◽  
Reach To Grasp ◽  
Grip Aperture ◽  
3D Information ◽  
Maximum Grip

Perceptual estimates of three-dimensional (3D) properties, such as the distance and depth of an object, are often inaccurate. Given the accuracy and ease with which we pick up objects, it may be expected that perceptual distortions do not affect how the brain processes 3D information for reach-to-grasp movements. Nonetheless, empirical results show that grasping accuracy is reduced when visual feedback of the hand is removed. Here we studied whether specific types of training could correct grasping behavior to perform adequately even when any form of feedback is absent. Using a block design paradigm, we recorded the movement kinematics of subjects grasping virtual objects located at different distances in the absence of visual feedback of the hand and haptic feedback of the object, before and after different training blocks with different feedback combinations (vision of the thumb and vision of thumb and index finger, with and without tactile feedback of the object). In the Pretraining block, we found systematic biases of the terminal hand position, the final grip aperture, and the maximum grip aperture like those reported in perceptual tasks. Importantly, the distance at which the object was presented modulated all these biases. In the Posttraining blocks only the hand position was partially adjusted, but final and maximum grip apertures remained unchanged. These findings show that when visual and haptic feedback are absent systematic distortions of 3D estimates affect reach-to-grasp movements in the same way as they affect perceptual estimates. Most importantly, accuracy cannot be learned, even after extensive training with feedback.

scholarly journals Grasping of Real-World Objects Is Not Biased by Ensemble Perception

2021 ◽  
Vol 12 ◽  
Author(s):  
Annabel Wing-Yan Fan ◽  
Lin Lawrence Guo ◽  
Adam Frost ◽  
Robert L. Whitwell ◽  
Matthias Niemeier ◽  
...  
Keyword(s):  
Real World ◽  
Motor Behavior ◽  
Support Vector ◽  
Visually Guided ◽  
Grip Aperture ◽  
Ensemble Perception ◽  
Ensemble Statistics ◽  
Maximum Grip Aperture ◽  
Average Size ◽  
Circular Target

The visual system is known to extract summary representations of visually similar objects which bias the perception of individual objects toward the ensemble average. Although vision plays a large role in guiding action, less is known about whether ensemble representation is informative for action. Motor behavior is tuned to the veridical dimensions of objects and generally considered resistant to perceptual biases. However, when the relevant grasp dimension is not available or is unconstrained, ensemble perception may be informative to behavior by providing gist information about surrounding objects. In the present study, we examined if summary representations of a surrounding ensemble display influenced grip aperture and orientation when participants reached-to-grasp a central circular target which had an explicit size but importantly no explicit orientation that the visuomotor system could selectively attend to. Maximum grip aperture and grip orientation were not biased by ensemble statistics during grasping, although participants were able to perceive and provide manual estimations of the average size and orientation of the ensemble display. Support vector machine classification of ensemble statistics achieved above-chance classification accuracy when trained on kinematic and electromyography data of the perceptual but not grasping conditions, supporting our univariate findings. These results suggest that even along unconstrained grasping dimensions, visually-guided behaviors toward real-world objects are not biased by ensemble processing.

Eating interrupted: the effect of intent on hand-to-mouth actions

2014 ◽  
Vol 112 (8) ◽  
pp. 2019-2025 ◽  
Author(s):  
Jason W. Flindall ◽  
Claudia L. R. Gonzalez
Keyword(s):  
Nonhuman Primates ◽  
Reach To Grasp ◽  
Food Items ◽  
Left Handed ◽  
Behavioral Studies ◽  
Neurophysiological Studies ◽  
Maximum Grip Aperture ◽  
Similar Motor ◽  
Behavioral Evidence ◽  
Maximum Grip

Evidence from recent neurophysiological studies on nonhuman primates as well as from human behavioral studies suggests that actions with similar kinematic requirements but different end-state goals are supported by separate neural networks. It is unknown whether these different networks supporting seemingly similar reach-to-grasp actions are lateralized, or if they are equally represented in both hemispheres. Recently published behavioral evidence suggests certain networks are lateralized to the left hemisphere. Specifically, when participants used their right hand, their maximum grip aperture (MGA) was smaller when grasping to eat food items than when grasping to place the same items. Left-handed movements showed no difference between tasks. The present study investigates whether the differences between grasp-to-eat and grasp-to-place actions are driven by an intent to eat, or if placing an item into the mouth (sans ingestion) is sufficient to produce asymmetries. Twelve right-handed adults were asked to reach to grasp food items to 1) eat them, 2) place them in a bib, or 3) place them between their lips and then toss them into a nearby receptacle. Participants performed each task with large and small food items, using both their dominant and nondominant hands. The current study replicated the previous finding of smaller MGAs for the eat condition during right-handed but not left-handed grasps. MGAs in the eat and spit conditions did not significantly differ from each other, suggesting that eating and bringing a food item to the mouth both utilize similar motor plans, likely originating within the same neural network. Results are discussed in relation to neurophysiology and development.

Quantification of Hand Grip Force under Dynamic Conditions

1993 ◽  
Vol 37 (10) ◽  
pp. 715-719 ◽  
Author(s):  
Katherine R. Lehman ◽  
W. Gary Allread ◽  
P. Lawrence Wright ◽  
William S. Marras
Keyword(s):  
Grip Force ◽  
Wrist Flexion ◽  
Range Of Movement ◽  
Ulnar Deviation ◽  
Dynamic Conditions ◽  
Radial Deviation ◽  
Hand Grip ◽  
Flexion Extension ◽  
Maximum Grip ◽  
Lower Grip

A laboratory experiment was conducted to determine whether grip force capabilities are lower when the wrist is moved than in a static position. The purpose was to determine the wrist velocity levels and wrist postures that had the most significant effect on grip force. Maximum grip forces of five male and five female subjects were determined under both static and dynamic conditions. The dominant wrist of each subject was secured to a CYBEX II dynamometer and grip force was collected during isokinetic wrist deviations for four directions of motion (flexion to extension, extension to flexion, radial to ulnar, and ulnar to radial). Six different velocity levels were analyzed and grip forces were recorded at specific wrist positions throughout each range of movement. For flexion-extension motions, wrist positions from 45 degrees flexion to 45 degrees extension were analyzed whereas positions from 20 degrees radial deviation to 20 degrees ulnar deviation were studied for radial-ulnar activity. Isometric exertions were also performed at each desired wrist position. Results showed that, for all directions of motion, grip forces for all isokinetic conditions were significantly lower than for the isometric exertions. Lower grip forces were exhibited at extreme wrist flexion and extreme radial and ulnar positions for both static and dynamic conditions. The direction of motion was also found to affect grip strength; extension to flexion exertions produced larger grip forces than flexion to extension exertions and radial to ulnar motion showed larger grip forces than ulnar to radial deviation. Although, males produced larger grip forces than females in all exertions, significant interactions between gender and velocity were noted.

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