Vestibular feedback maintains reaching accuracy during body movement.

Area of Science:

• Neuroscience
• Human Motor Control
• Vestibular System

Background:

• Unintended body motion can disrupt arm movements and interaction accuracy.
• Vestibular stimulation can evoke arm movements, but their functional role is unclear.
• A compensatory mechanism for body motion would ideally operate in an earth-fixed, not body-fixed, reference frame.

Purpose of the Study:

• To investigate the functional role of vestibular-evoked arm movements.
• To determine if vestibular control of arm movements is task-dependent.
• To test the hypothesis that vestibular-evoked arm movements compensate for body motion in an earth-fixed reference frame.

Main Methods:

• Subjects performed reaching tasks towards earth-fixed and body-fixed targets.
• Galvanic vestibular stimulation (GVS) was applied during gentle chair rotation.
• Arm trajectory was recorded to assess responses to GVS and body motion.

Main Results:

• GVS induced significant, polarity-dependent arm corrections during the earth-fixed task.
• These corrections compensated for perceived changes in body motion.
• No compensatory arm responses to GVS were observed during the body-fixed task.
• The observed effects were independent of limb kinematics differences between tasks.

Conclusions:

• Vestibular control of the upper limb serves to maintain reaching accuracy during unpredictable body motion.
• This compensatory function is specific to movements within an earth-fixed reference frame.
• The findings confirm the functional role of vestibular-evoked arm movements in stabilizing interactions with the environment.