Proprioceptive feedback modulates coordinating information in a system of segmentally distributed microcircuits.

Area of Science:

• Neuroscience
• Animal Behavior
• Locomotion Control

Background:

• Crustacean swimmerets generate metachronal propulsion via modular neural circuits.
• Intersegmental coordinating circuits synchronize these modules with specific phase differences.

Purpose of the Study:

• To investigate how crayfish neural circuits controlling swimmerets respond to imposed movements.
• To understand the role of sensory feedback in modulating rhythmic neural activity.

Main Methods:

• Utilized a semi-intact crayfish preparation with one attached swimmeret and isolated central nervous system (CNS).
• Recorded extracellularly from power-stroke (PS) and return-stroke (RS) nerves, coordinating axons, and homologous nerves in adjacent segments.
• Manipulated limb position (maintained retractions) and voltage-clamped nonspiking stretch receptors (NSSRs).

Main Results:

• Maintained retractions weakened PS bursts, strengthened RS bursts, and altered coordinating axon efference copies without changing cycle period.
• Changes in efference copies modified the phase and duration, but not strength, of PS bursts in neighboring segments.
• Voltage clamping NSSRs altered burst durations and strengths in innervating axons and their efference copies.

Conclusions:

• Swimmeret neural modules dynamically adjust motor output and intersegmental coordination in response to mechanical perturbations.
• Nonspiking stretch receptors provide crucial sensory feedback that modulates rhythmic activity and efference copy signals.
• The system exhibits rapid adaptation and reversibility, ensuring efficient and robust locomotion control.