Oviposition digging in the grasshopper. II. Descending neural control

Area of Science:

• Neuroscience
• Animal Behavior
• Entomology

Background:

• Oviposition digging in grasshoppers is a complex, rhythmic motor behavior.
• The neural control mechanisms underlying this behavior are not fully understood.

Purpose of the Study:

• To investigate the neural control of oviposition digging in female grasshoppers.
• To identify the role of the ventral nerve cord in initiating and modulating this behavior.

Main Methods:

• Transection of the ventral nerve cord in female grasshoppers.
• Electrical stimulation of the cut nerve cord at different levels.
• Application of cold saline to the nerve cord.
• Intracellular recordings of ventral opener motoneurones.

Main Results:

• Ventral nerve cord transection activated the oviposition digging motor program.
• Electrical stimulation induced inhibition, phase resetting, and frequency modulation of motor activity.
• Cold saline application reversibly elicited the motor program.
• Stimulation evoked inhibitory postsynaptic potentials (IPSPs) and abolished synaptic input to motoneurones.

Conclusions:

• Neural control of oviposition digging involves both thoracic and cephalic components.
• The motor program is likely initiated and maintained by a release from descending neural inhibition.