Control of Grasshopper Singing Behavior by the Brain: Responses to Electrical Stimulation 1

and Summary The influence of the supraesophageal ganglion (brain) on the acoustic behavior of the acridid grasshopper Gomphocerus rufus L. was studied by means of local electrical stimulation.1 For stimulation sharpened metal wires as well as semimicroelectrodes filled with cobalt‐salt solution were used with which the fibre tracts were marked near the stimulation site. The behavior was recorded by a video system and represented graphically. 2 Stimulation of the brain of freely moving or partly restrained males elicited the courtship song, with its three subunits and the ordinary song mostly accompanied by the appropriate locomotion. The sequence and structure of the song subunits elicited in certain experiments indicated the presence of a pacemaker for the courtship song. The brain controls songtype, sequence of courtship subunits and their coordination. Only stridulatory movements could never be altered by stimulation. Other effects included the induction of pursuit sounds, elements of copulatory behavior and locomotion. 3 Stimulus induced behavior could override other behavior such as feeding or even copulation. It could be modified, within limits, by the presentation of a female. 4 The assignment of the electrode‐tip‐marks to specific brain substrates was based on a three‐dimensional reconstruction of the brain from serial sections. The stimulus currents were so low that the substrate responsible for the effect is presumed to have been near the electrode tip; a variety of previously published evidence supports this view. The possible locations of fibers affected by the stimulus were further restricted by marking with cobalt sulfide. 5 All the stimulus sites at which acoustic behavior was elicited were in a region surrounding, or in a few cases within, the mushroom bodies. A system of fibers passing from the α‐lobe to the calyx was found to be significant in the production of the ordinary song or song with head‐shaking. Production of the courtship song also involves regions of the brain medioventral to the mushroom bodies.Zusammenfassung Mit lokaler elektrischer Reizung wurde der Einfluß des Oberschlundganglions (Gehirn) auf das akustische Verhalten der Feldheuschrecke Gomphocerus rufus L. untersucht. Das Verhalten wurde auf einem Videosystem aufgezeichnet und graphisch dargestellt. Durch Stimulation freibeweglicher Tiere über zugeätzte Metallelektroden, sowie von teilweise gehalterten Tieren über kobaltgefüllte Semi‐Mikrokapillaren läßt sich sowohl der Lockgesang mit der ihn begleitenden Lokomotion, als auch der aus drei Untereinheiten aufgebaute Werbegesang auslösen. Die Reihenfolge, in der die Untereinheiten dabei auftreten, läßt auf einen interneuralen Taktgeber schließen. Das ausgelöste Verhalten ist in Grenzen modifizierbar, kann sich aber gegenüber Fressen oder gar Kopulation durchsetzen. Die Lokalisation der Elektrodenspitzenpunkte erfolgte mit Hilfe einer drei‐dimensionalen Rekonstruktion des Gehirns. Als ein für das akustische Verhalten wichtiges neurales Substrat stellen sich dabei die Pilzkörper, ein sich ihnen anschließendes Fasersystem, aber auch Bereiche medioventral davon heraus.