Complex podokinetic (PK) response to post-rotational vestibular stimulation

Area of Science:

• Neuroscience
• Biomechanics
• Human Locomotion

Background:

• The podokinetic (PK) system senses and controls spatial orientation during locomotion by referencing body orientation to a stable stance foot.
• Understanding the interplay between the vestibular system and the PK system is crucial for explaining complex motor behaviors.

Purpose of the Study:

• To investigate the interaction between the vestibular and podokinetic systems.
• To analyze the resulting body rotation and sensory feedback during a step-in-place task following vestibular stimulation.

Main Methods:

• Blindfolded subjects performed a step-in-place task after a unidirectional post-rotational vestibular stimulus.
• Observed and recorded the direction and speed of body rotation.
• Developed and simulated a closed-loop model of the vestibular-PK system.

Main Results:

• Six out of nine subjects exhibited self-initiated rotation in the direction of prior turntable rotation, despite no sensation of turning.
• The PK-induced rotation showed a complex pattern: initial decline, reversal, and gradual decay over several minutes.
• The closed-loop model simulation closely matched the experimental behavioral data.

Conclusions:

• A functionally closed loop exists between the vestibular and podokinetic systems during locomotion.
• This feedback loop significantly influences spatial orientation and motor control, particularly after vestibular perturbation.
• The findings provide insights into the neural mechanisms underlying adaptive motor responses.