A central pattern-generating network contributes to "reflex-reversal"-like leg motoneuron activity in the locust

Area of Science:

• Neuroscience
• Locomotion Biology
• Insect Physiology

Background:

• Locomotion relies on complex neural circuits.
• Central pattern generators (CPGs) are key to rhythmic motor output.
• Understanding CPGs in insects offers insights into fundamental motor control.

Purpose of the Study:

• To introduce a novel, pharmacologically-independent rhythmic preparation of the locust mesothoracic segment.
• To investigate the central generation of rhythmic motor activity in locust leg motoneurons.
• To explore the role of proprioceptive feedback in modulating CPG output.

Main Methods:

• Isolation of the locust mesothoracic ganglion.
• Recording of motoneuron activity in leg muscles (femur-tibia joint).
• Deafferentation experiments to test for central generation of rhythmicity.
• Stimulation of proprioceptive organs (femoral chordotonal organ) to mimic joint movement.

Main Results:

• The isolated locust mesothoracic segment preparation exhibits long-lasting rhythmic activity in leg motoneurons.
• This rhythmic activity, characterized by alternating flexor and extensor bursts, is centrally generated in 37% of preparations.
• Proprioceptive feedback, specifically mimicking femur-tibia joint flexion or extension, effectively reversed motoneuron activity patterns, indicating reflex reversal.

Conclusions:

• The locust mesothoracic preparation provides a robust model for studying central pattern generators.
• The observed reflex reversal is mediated by the action of central pattern-generating networks.
• This study supports the hypothesis that CPGs are responsible for the observed reflex reversal in insect locomotion.