Task-dependent modification of leg motor neuron synaptic input underlying changes in walking direction and walking...

Area of Science:

• Neuroscience
• Locomotion research
• Animal behavior

Background:

• Animals exhibit adaptable behaviors for environmental navigation.
• Terrestrial locomotion involves complex adaptations, including changes in speed and direction.
• Understanding the neural basis of motor control is crucial for explaining behavioral flexibility.

Purpose of the Study:

• To investigate how leg motor neurons control changes in walking direction and speed in the stick insect Cuniculina impigra.
• To identify the specific synaptic input alterations responsible for modifying motor output during locomotion tasks.

Main Methods:

• Utilized a semi-intact stick insect preparation for intracellular recordings from leg motor neurons.
• Employed a single-leg preparation with a treadwheel to elicit and record walking motor activity.
• Stimulated abdominal and cephalic regions to evoke fictive forward and backward locomotion, respectively.

Main Results:

• Changing walking direction involved a phase switch in thorax-coxa joint motor neuron activity (protractor and retractor).
• This phase switch resulted from reciprocal changes in phasic synaptic inputs (inhibitory/excitatory) during the step cycle.
• Increased stepping velocity during stance correlated significantly only with flexor motor neuron activity.

Conclusions:

• Locomotion control in stick insects involves task-specific modulation of synaptic inputs to leg joint motor neurons.
• Different motor tasks, like altering direction, are achieved by distinct neural circuit configurations.
• The findings highlight the specificity of neural control mechanisms underlying behavioral adaptations in locomotion.