Effect of visual and haptic feedback on grasping movements

Area of Science:

• Neuroscience
• Perception
• Motor Control

Background:

• Perceptual estimates of 3D properties like distance and depth are often inaccurate.
• Despite this, it's assumed 3D distortions don't impact reach-to-grasp movements.
• However, grasping accuracy decreases without visual hand feedback.

Purpose of the Study:

• To investigate if specific training can correct grasping behavior without feedback.
• To determine if 3D perceptual distortions influence reach-to-grasp movements in the absence of feedback.

Main Methods:

• Subjects grasped virtual objects at varying distances without visual or haptic feedback.
• Movement kinematics were recorded before and after training blocks with different feedback combinations.
• Training included visual feedback of the hand and tactile object feedback.

Main Results:

• Pre-training showed systematic biases in hand position, final grip aperture, and maximum grip aperture, modulated by object distance.
• Post-training, only hand position showed partial adjustment; grip apertures remained unchanged.
• These biases mirrored those found in perceptual tasks.

Conclusions:

• Systematic distortions in 3D estimates affect reach-to-grasp movements when visual and haptic feedback are absent.
• Grasping accuracy in the absence of feedback cannot be learned, even with extensive training.
• Motor control for grasping is susceptible to perceptual distortions of 3D space.