Pointing to oneself: active versus passive proprioception revisited and implications for internal models of motor...

Area of Science:

• Neuroscience
• Biomechanics
• Human Movement Science

Background:

• Proprioception, the sense of limb position, is crucial for motor control.
• The role of internal models in processing proprioceptive information during active movements is debated.

Purpose of the Study:

• To compare the accuracy of active versus passive proprioception in unconstrained 3D movements.
• To investigate the influence of movement duration on proprioceptive accuracy.
• To evaluate the necessity of internal forward models for limb position estimation.

Main Methods:

• Subjects performed pointing movements to proprioceptively match limb positions.
• Both active (self-generated) and passive (experimenter-generated) limb movements were tested.
• Visual feedback was manipulated (eyes open/closed) and movement duration varied.

Main Results:

• High accuracy was observed in localizing limb position using proprioception during unconstrained movements.
• Active and passive proprioception yielded comparable accuracy in estimating final limb position.
• Movement duration did not significantly affect the accuracy of proprioceptive estimates.
• Accuracy was not improved with eyes open compared to eyes closed.

Conclusions:

• Proprioceptive information provides highly accurate limb position estimates in natural movements.
• Active proprioception offers no accuracy advantage over passive proprioception.
• The findings challenge the necessity of invoking internal forward models to explain limb position estimation accuracy.