Interactions between the tonic and cyclic postural motor programs in the crayfish abdomen.

Area of Science:

• Neuroscience
• Animal Behavior
• Motor Control

Background:

• Crayfish (Procambarus clarkii) utilize abdominal muscles and motoneurons for both tonic postural adjustments and cyclic movements during terrestrial walking.
• It is hypothesized that these distinct behavioral subsystems may share common tonic premotor interneurons.

Purpose of the Study:

• To investigate whether tonic postural control and cyclic movement generation in crayfish share premotor interneurons.
• To understand the interaction between these two behavioral subsystems at the premotor and motoneuron levels.

Main Methods:

• Monitoring of tonic flexion- and extension-producing interneurons during cyclic pattern generation in crayfish.
• Simultaneous activation of single tonic postural interneurons with the cyclic motor pattern.

Main Results:

• A small proportion of tonic interneurons were recruited or inhibited during cyclic pattern generation, but none significantly contributed to the cyclic motor output.
• Interactions between tonic postural interneurons and the cyclic motor pattern were complex, with some overriding, some being overridden, and others showing variable dominance across ganglia.
• Weak interactions were observed at the premotor level, with stronger interactions occurring at the motoneuron level.

Conclusions:

• Each behavioral subsystem (tonic posture and cyclic movement) appears to rely on its own unique set of premotor interneurons.
• Interactions at the motoneuron level are likely crucial for switching between postural adjustments and cyclic movements.
• The specific interneurons responsible for generating the cyclic motor pattern remain unidentified.