Sensorimotor function may be fundamentally limited in hypogravity

Area of Science:

• Spaceflight physiology
• Sensorimotor neuroscience
• Human factors engineering

Background:

• Humans experience altered sensorimotor function during spaceflight due to changing gravitational fields.
• Adaptation to altered gravity is known, but inherent physiological limitations in hypogravity remain unclear.

Purpose of the Study:

• To investigate whether human physiology has limitations in hypogravity that adaptation cannot overcome.
• To assess manual control performance in a simulated hypogravity environment.

Main Methods:

• A laboratory-based centrifuge simulated hypogravity (0.5 Gc).
• Ten healthy subjects performed a joystick-controlled manual task to manage chair tilt.
• Manual control performance was measured during transitions from 1.0 Gc to 0.5 Gc and during adaptation in 0.5 Gc.

Main Results:

• Manual control performance decreased by 69% immediately after transitioning to 0.5 Gc.
• Performance partially adapted over 18 minutes but remained significantly impaired (42% worse than 1.0 Gc).
• Computational modeling indicated adaptation involved increased control gain (KP).

Conclusions:

• Hypogravity imposes fundamental limitations on closed-loop sensorimotor performance, likely due to a reduced signal-to-noise ratio in sensory receptors.
• Impaired performance in hypogravity may increase risks during tasks like lunar piloting and ambulation.
• Adaptation mechanisms involve adjustments in neural control strategies, but do not fully restore performance to 1.0 Gc levels.