Orientation-dependent changes in single motor neuron activity during adaptive soft-bodied locomotion

Area of Science:

• Neuroscience
• Biophysics
• Zoology

Background:

• Studying motor control in stiff-bodied animals is challenging due to complex neural codes.
• Soft-bodied organisms offer simplified models for motor control research.

Purpose of the Study:

• To investigate the neural basis of adaptive motor control in the soft-bodied tobacco hawkmoth caterpillar (Manduca sexta).
• To understand how motor neuron activity relates to gait kinematics during locomotion in different planes.

Main Methods:

• Utilized flexible microelectrode arrays to record electromyographic (EMG) signals from individual motor neurons in Manduca sexta larvae.
• Converted EMG traces into motor neuron frequency patterns with single-neuron resolution.
• Correlated motor neuron activity with gait kinematics during climbing and other movements.

Main Results:

• Motor neuron activity timing and gait kinematics were found to be dependent on the orientation of the plane of motion.
• During climbing, motor neuron activity shifted to correlate with movements in anterior body segments.
• Observed an orientation-dependent shift in motor activity consistent with changing propulsive force requirements.

Conclusions:

• Manduca sexta exhibits adaptive load compensation through central command timing, challenging previous hypotheses.
• The soft-bodied nature and simple motor innervation of Manduca sexta larvae provide a powerful model for dissecting neural control of movement.