On orienting the hand to reach and grasp an object

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Reaching and grasping are complex motor skills involving multiple body segments.
• Understanding how visual and non-visual cues influence these movements is crucial for motor control research.

Purpose of the Study:

• To investigate the kinematic changes in reaching and grasping movements under varying object properties (position, orientation, size).
• To examine the role of visual feedback in modulating these kinematic adjustments.

Main Methods:

• Participants performed reaching and grasping tasks with a parallelepiped under full vision and no vision conditions.
• Kinematic data of reaching and grasping movements were analyzed, focusing on movement direction, amplitude, finger axis orientation, wrist angular displacement, and finger aperture.

Main Results:

• Object orientation significantly affected reaching direction and amplitude.
• Object position influenced the timing of finger axis orientation and wrist angular displacement.
• Finger aperture during grasping was modulated by object size and orientation, independent of visual perception distortions.
• These kinematic adjustments persisted even without visual control.

Conclusions:

• Reaching and grasping kinematics are robustly influenced by object properties like orientation and position.
• Visual feedback is not essential for these specific kinematic adjustments during reaching and grasping.
• The findings support the integration of distal (object-related) and proximal (effector-related) information in motor planning and execution.