On the role in stridulation of plurisegmental interneurons of the acridid grasshopperOmocestus viridulus L.

Summary

• 1. An experimental set-up (Fig. 1) was designed to permit monitoring of multiple parameters of the activity of the acridid grasshopperOmocestus viridulus during stridulation induced by electrical stimulation of the brain (Fig. 2). These parameters were (i) intracellularly recorded action potentials of descending neurons subsequently stained by dye injection, (ii) electrical activity of the stridulatory muscles, (iii) the stridulatory movements and (iv) the sound pattern produced.

• 2. D.C. stimulation of the meso- and metathoracic ganglia isolated by transection of anterior and posterior connectives shows that these ganglia are independent of phasic input when generating the pattern of excitation for species-specific stridulation (Fig. 3).

• 3. Stridulation-related activity was observed (Figs. 4, 5) in neurons descending from the dorsal protocerebrum to at least the third abdominal ganglion. They send out collaterals in the subesophageal and all the thoracic ganglia. During stridulation, all but one of these brain neurons show a tonic increase in discharge rate; the remaining cell discharges in phase with the stridulation.

• 4. Neurons descending from the subesophageal ganglion (Figs. 6–9) project into the metathoracic ganglion and in some cases, into the abdominal ganglia. They send out collaterals in all the ganglia in which they have been visualized. The activity of the fibers is phasically coupled to the stridulation rhythm, the individual neurons being active at different phases of the stridulation cycle.