Postural control in the lamprey: A study with a neuro-mechanical model

Area of Science:

• Neuroscience
• Biophysics
• Animal Behavior

Background:

• Lampreys maintain dorsal-side-up orientation via a vestibular-driven postural control system.
• Reticulospinal (RS) pathways transmit postural correction commands from the brainstem to the spinal cord.
• RS neurons show strong dynamic but weak static responses to contralateral roll tilt.

Purpose of the Study:

• To test the hypothesis that spinal cord decoding of RS commands relies on subtracting left and right pathway signals.
• To investigate the role of vestibular input and locomotor oscillations in lamprey postural stabilization.

Main Methods:

• A neuro-mechanical model of an intact lamprey was used, restraining postural activity but allowing undulations.
• Left and right RS pathway activity was recorded and used to control a motor for axial rotation.
• The model's ability to stabilize orientation and reproduce characteristic postural effects was assessed.

Main Results:

• The hybrid system automatically stabilized lamprey orientation, compensating for large tilts (+/-180 degrees).
• Reduced RS neuron activity and vestibular responses in non-swimming lampreys impaired stabilization, but oscillations restored balance.
• The model reproduced the dorsal light response, effects of labyrinth removal, and compensation by visual input.

Conclusions:

• Supraspinal commands for roll plane postural corrections are effectively decoded by subtracting signals from left and right RS pathways.
• Head oscillations during locomotion contribute to postural stabilization by activating vestibular organs.
• The findings provide insights into the neural mechanisms of postural control in vertebrates.