V1 and v2b interneurons secure the alternating flexor-extensor motor activity mice require for limbed locomotion

Area of Science:

• Neuroscience
• Motor Control
• Spinal Cord Physiology

Background:

• Locomotion and reflex behaviors in vertebrates rely on reciprocal muscle activation.
• Spinal cord inhibitory interneurons are critical for motor coordination, but their specific roles in flexor-extensor activity remain unclear.

Purpose of the Study:

• To identify the specific spinal interneurons responsible for coordinating alternating flexor-extensor muscle activity.
• To elucidate the role of V1 and V2b interneurons in generating locomotor rhythms and reflex behaviors.

Main Methods:

• Investigated the function of V1 and V2b interneurons in the mammalian spinal cord.
• Utilized genetic manipulation to abrogate neurotransmission from V1 and V2b interneurons.
• Analyzed locomotor activity and reflex responses in isolated spinal cord preparations and live animals.

Main Results:

• Disruption of V1 and V2b interneuron neurotransmission led to synchronous, non-alternating locomotor activity.
• Mice lacking V1 and V2b inhibition exhibited significant deficits in limb joint articulation.
• Impaired limb-driven reflex movements were observed in V1 and V2b-deficient mice.

Conclusions:

• V1 and V2b inhibitory interneurons are essential components of the central pattern generator (CPG) for limb locomotion.
• These neurons play a critical role in coordinating flexor-extensor activity for rhythmic movement and reflexes.
• Identifies V1 and V2b interneurons as key players in spinal motor control circuits.