The sensorimotor and cognitive integration of gravity

Area of Science:

• Neuroscience
• Biomechanics
• Human Physiology

Background:

• Gravity influences motor control beyond local limb loading.
• The central nervous system (CNS) uses gravity as a dynamic orienting reference for motor acts.
• Understanding motor adaptation in altered gravity (e.g., weightlessness) is crucial.

Purpose of the Study:

• To demonstrate gravity's role as a dynamic orienting reference for motor control.
• To review experimental evidence from 1g and 0g conditions.
• To investigate CNS strategies for maintaining motor schemas in weightlessness.

Main Methods:

• Review of experiments conducted in normal gravity (1g) and weightlessness (0g).
• Analysis of locomotor tasks and head stabilization strategies.
• Examination of three-dimensional arm reaching movements.

Main Results:

• Head stabilization relative to gravity is a key strategy for dynamic equilibrium.
• Existing motor schemas evolved under normal gravity may not suffice in weightlessness.
• The CNS may need to develop novel motor strategies through learning when conservative processes fail.

Conclusions:

• Gravity is a critical factor in motor planning and execution at higher nervous system levels.
• Motor control in weightlessness requires adaptation, potentially involving new strategy creation.
• Future research needs novel experimental paradigms to study human motor control in space, moving beyond the "terrestrial biped" model.