Motor coordination uses external spatial coordinates independent of developmental vision

Area of Science:

• Neuroscience
• Human Motor Control
• Perceptual Psychology

Background:

• Bimanual movement coordination provides insights into human movement planning.
• A known constraint is the benefit of symmetry relative to the body midline for hand and finger movements.
• This symmetry constraint suggests movement coordination is guided by a perceptual code, often assumed to be visual.

Purpose of the Study:

• To investigate whether the visual system is critical for the externally coded symmetry constraint in bimanual movement coordination.
• To determine if congenitally blind individuals exhibit the same symmetry constraint as sighted individuals.

Main Methods:

• Congenitally blind and sighted participants performed symmetrical and non-symmetrical (parallel) bimanual tapping and finger oscillation tasks.
• Movement execution accuracy was compared between symmetrical and non-symmetrical conditions for both groups.
• Performance was analyzed independent of anatomical factors like hand posture and finger homology.

Main Results:

• Both congenitally blind and sighted participants executed symmetrical bimanual movements more accurately than parallel movements.
• This effect was consistent regardless of hand posture or finger homology.
• Blind participants showed reliance on external spatial factors for movement coordination, contrasting with their perceptual processing.

Conclusions:

• The externally coded symmetry constraint in bimanual coordination can develop without visual input.
• The visual system is not essential for establishing an external-spatial reference frame in motor control.
• Movement planning utilizes external spatial information that is independent of the visual system.