Sensorimotor mapping for anticipatory grip force modulation.

Area of Science:

• Neuroscience
• Biomechanics
• Human Motor Control

Background:

• Predictive grip force modulation is crucial for object manipulation, compensating for inertial forces during movement.
• The coupling between grip force (GF) and load force (LF) suggests internal models govern predictive GF control.
• Understanding variables influencing GF modulation at movement initiation is key.

Purpose of the Study:

• To identify variables influencing grip force modulation at movement initiation.
• To investigate predictive grip force control strategies under altered gravity conditions.

Main Methods:

• Twenty subjects performed point-to-point movements in normal and hypergravity (parabolic flights).
• Control experiments varied movement kinematics and object mass under normal gravity.
• Grip force (GF) and load force (LF) were analyzed during object manipulation.

Main Results:

• Subjects accurately adjusted to increased weight in hypergravity but overestimated inertial loads.
• Under hypergravity, GF-LF relationships during movement resembled increased object mass, not altered kinematics.
• Altered movement kinematics alone did not replicate hypergravity effects on GF-LF coupling.

Conclusions:

• Anticipatory grip force modulation relies on sensorimotor mapping combining perceived weight and movement kinematics.
• This strategy reflects prior knowledge of mass-weight-load relationships in Earth's gravity.
• Humans may not fully adapt predictive grip control to novel inertial environments beyond Earth's gravity.