When mirrors lie: "visual capture" of arm position impairs reaching performance

Area of Science:

• Neuroscience
• Perception
• Human Motor Control

Background:

• The brain integrates multisensory information to create a coherent sense of body position.
• Visual information often dominates when conflicting sensory inputs arise regarding limb location.

Purpose of the Study:

• To investigate the influence of visual feedback from a mirrored limb on reaching movements of the unseen contralateral limb.
• To examine the impact of visual-proprioceptive conflict on motor control.

Main Methods:

• Participants viewed their left arm in a mirror, creating a visual representation of their right arm.
• Reaching movements of the unseen right arm were recorded under conditions of visual-proprioceptive congruence and conflict.
• The mirror illusion was employed to manipulate visual input of limb position.

Main Results:

• Reaching movements of the unseen right arm were significantly more affected by visual-proprioceptive conflict when the left arm was viewed in the mirror.
• This indicates a 'visual capture' of the unseen arm's perceived position.
• The magnitude of reaching error increased with greater conflict between visual and proprioceptive cues.

Conclusions:

• Visual information, even when derived from a mirrored limb, can capture the perceived position of an unseen limb.
• This visual capture significantly influences subsequent motor behavior, specifically reaching movements.
• Findings highlight the brain's dynamic integration of sensory modalities in body representation and motor control.