Partly shared spinal cord networks for locomotion and scratching

Area of Science:

• Neuroscience
• Comparative Physiology
• Motor Control

Background:

• Animals exhibit diverse rhythmic behaviors using limited motor systems.
• Central pattern generators (CPGs) in the nervous system produce basic rhythmic movements.
• In invertebrates, single or overlapping CPGs can generate multiple behaviors; less is known in vertebrates.

Purpose of the Study:

• To investigate the extent of CPG sharing between hind limb locomotion and scratching in vertebrates.
• To understand how spinal cord networks generate and coordinate different rhythmic motor patterns.

Main Methods:

• Used spinally transected, immobilized adult red-eared turtles to isolate spinal cord function.
• Recorded activity of individual spinal cord interneurons during swimming and scratching motor pattern generation.
• Applied simultaneous swim- and scratch-evoking stimuli to observe interactions in motor output.

Main Results:

• Many spinal interneurons were active during both swimming and scratching, suggesting shared circuitry.
• Some interneurons showed differential activity, being active in scratching but inhibited in swimming.
• Simultaneous stimulation led to complex interactions, including hybrid rhythms or cessation of movement, dependent on stimulus intensity.

Conclusions:

• Locomotion and scratching in vertebrates likely involve partly shared spinal cord CPGs.
• Spinal cord networks exhibit significant plasticity, allowing for the generation of multiple rhythmic behaviors.
• Interactions between different motor pattern inputs highlight the complex integration within the vertebrate spinal cord.