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

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.

Download Full-text

Is Grasping Impaired in Hemispatial Neglect?

Behavioural Neurology ◽

10.1155/2002/495854 ◽

2002 ◽

Vol 13 (1-2) ◽

pp. 17-28 ◽

Cited By ~ 22

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.

Download Full-text

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

Journal of Experimental Psychology Human Perception & Performance ◽

10.1037/a0035061 ◽

2014 ◽

Vol 40 (2) ◽

pp. 889-896 ◽

Cited By ~ 2

Author(s):

Svenja Borchers ◽

Rebekka Verheij ◽

Jeroen B. J. Smeets ◽

Marc Himmelbach

Keyword(s):

Grip Aperture ◽

Maximum Grip Aperture ◽

Maximum Grip

Download Full-text

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

10.1101/2021.10.26.464901 ◽

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.

Download Full-text

Prehension and Perception of Size in Left Visual Neglect

Behavioural Neurology ◽

10.1155/2002/252405 ◽

2002 ◽

Vol 13 (1-2) ◽

pp. 3-15 ◽

Cited By ~ 17

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.

Download Full-text

Some illusions are more inconsistent than others

10.31234/osf.io/7mxg8 ◽

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.

Download Full-text

The Effect of Learned Perceptual Associations on Visuomotor Programming Varies with Kinematic Demands

Journal of Cognitive Neuroscience ◽

10.1162/08989290051137495 ◽

2000 ◽

Vol 12 (6) ◽

pp. 950-964 ◽

Cited By ~ 12

Author(s):

Angela M. Haffenden ◽

Melvyn A. Goodale

Keyword(s):

Relative Size ◽

Target Object ◽

Perceptual Information ◽

Visually Guided ◽

Large Circle ◽

Object Shape ◽

Size Information ◽

Demand Changes ◽

Finger Posture ◽

Shape And Size

The present set of experiments investigated the possibility that learned perceptual information can, under certain circumstances, be utilized by visuomotor programming. In Experiment 1 (N = 28), an association was established between the color and size of square wooden blocks (e.g., red = large; yellow = small, or vice-versa). In Experiment 2 (N = 28), an association was established between the shape and size of plastic objects (e.g., hexagon = large; circle = small, or vice-versa). It was expected that the learned associations would change the perceived size of two probe objects halfway in size between the large and small objects (the probe object matched by color or shape to the large group of objects would appear smaller than the probe object matched to the small group of objects as a result of within-group relative size comparisons). In both experiments, half of the participants grasped the target objects, and the other half estimated the size of the objects by opening their thumb and finger a matching amount. For Experiment 1, it was predicted that an influence of the lérned association on the treatment of the probe objects would be seen in manual estimations and in grip scaling because the kinematics of the grasping movement were very similar across trials. As predicted, the learned association between size and color was as easily incorporated into visually guided grasping as it was into visual perceptions. In Experiment 2, it was predicted that an influence of the learned perceptual association would be seen only in manual estimations, and not in grip scaling, because the variability in target object shape from trial to trial would demand changes in precontact finger posture across trials. Despite the significant effect of the size-shape association on size estimations, no influence was seen in preparatory grip scaling, probably because varying shape increased the metrical demands on visuomotor programming from those in Experiment 1. Together, the results suggest that visuomotor programming can make use of learned size information under some, but not all, conditions.

Download Full-text

Effect of visual and haptic feedback on grasping movements

Journal of Neurophysiology ◽

10.1152/jn.00439.2014 ◽

2014 ◽

Vol 112 (12) ◽

pp. 3189-3196 ◽

Cited By ~ 12

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.

Download Full-text