Fooling the brain into thinking it sees both hands moving enhances bimanual spatial coupling

Area of Science:

• Neuroscience
• Motor Control
• Human Perception

Background:

• Bimanual coordination involves complex motor control.
• The role of visual feedback in interlimb coordination is well-established.
• Mirror visual feedback is known to influence motor imagery and execution.

Purpose of the Study:

• To investigate if mirror reflection of one hand's movement directly influences the motor output of the contralateral (hidden) hand.
• To determine the extent of bimanual spatial coupling under mirror visual feedback conditions.
• To differentiate the effects of mirror feedback from simple visual feedback of one hand.

Main Methods:

• Participants performed bimanual circle drawing tasks with a mirror positioned between their hands.
• One hand and its reflection were visible, while the other hand remained hidden.
• Measures of circle size and spatial coupling were analyzed.
• Comparison with conditions involving vision of one hand only and full vision control tasks.

Main Results:

• Mirror reflection significantly enhanced bimanual spatial coupling, as evidenced by changes in circle size.
• The observed effects of mirror feedback were distinct from those of viewing one hand alone.
• No significant difference was found between mirror feedback and a control task performed in full vision.
• No consistent phase lead of the visible hand was detected, suggesting immediate processing.

Conclusions:

• Visual mirror symmetry can deceive the brain into perceiving simultaneous movement of both hands.
• This perceptual illusion leads to increased spatial coupling and synchronization of bimanual movements.
• The observed effects are immediate, indicating an automatic process rather than a feedback-dependent one.