Prothoracic DUM neurons of the cricket Gryllus bimaculatus ? responses to natural stimuli and activity in walking behavior

Abstract

Responses to sensory stimuli and spike activity during walking were investigated in bilaterally symmetrical dorsal unpaired median (DUM) neurons of the cricket. Intracellular recordings within the prothoracic ganglion were made either in restrained animals or in stationary walking specimens whilst parameters of their intended locomotion were measured. Three types of DUM cells were distinguished morphologically and physiologically. DUMa neurons send axons through segmental nerves. They often generated spontaneously large action potentials with low frequencies. Most DUMa neurons showed multimodal sensitivity, preferentially to cercal wind puffs and 15 kHz sound. Mean latencies ranged from 25 to 349 ms. Their large intraindividual variability could be correlated with behavioral modes during walking. Generally, the spike frequency increased with increased forward speed, while it was not related to turning. DUMb neurons projected either through the anterior or posterior connectives, but seemed physiologically similar to DUMa neurons. DUMc neurons were H-shaped with axons in both pairs of connectives. No external stimulus led to discrete spikes, but the regular spontaneous activity was modulated following cercal wind puffs to a restrained animal. During wind evoked escape the spike activity of another DUMc cell was modulated in phase with the rhythmic running behavior. The possibly different functions of DUMa and DUMc neurons during walking are discussed.

Distribution and activation of different types of octopaminergic DUM neurons in the locust

“…11). This notion agrees with results in crickets (Gras et al, 1990), where a lesion of the neck connective tissues leads to a drastic reduction of the response to mechanosensory stimulation. Furthermore, the VUM neurons of the larvae of Manduca sexta receive descending inputs from the SEG (Johnston et al, 1997), which indicates that in different insect species mechanosensory information is first processed in the SEG and then is passed to modulatory unpaired median neurons.…”

“…The intersegmental coordination of the activity of DUM5 and DUM3,4,5 neurons is probably mediated by ascending and descending interneurons because lesions of both the abdominal and the anterior connective tissues led to an irreversible reduction in the number of common PSPs in these neurons. Gras et al (1990) observed a persistent reduction of PSPs in prothoracic DUM neurons when cutting the neck connectives in Gryllus bimaculatus. Furthermore, common intersegmental inputs have been shown in locust abdominal DUM neurons (Pflü ger and Watson, 1995) and in abdominal VUM neurons in Manduca sexta (Pflü ger et al, 1993).…”

Auditory modulation of wind-elicited walking behavior in the cricket, Gryllus bimaculatus

“…It has recently been reported that corollary discharges during singing inhibit the GI's responses to air-puff stimuli (Schöneich and Hedwig, 2015). However, some multimodal interneurons that respond to both auditory and air-puff stimuli have been identified in the cephalic and prothoracic ganglia (Gras et al, 1990;Schildberger, 1984a). It is possible that the cercal and auditory signals are combined in the cephalic and thoracic ganglia.…”

Octopamine and Experience-Dependent Modulation of Aggression in Crickets

“…This seems feasible considering that specific octopaminergic neurones are activated by flight or flightinducing stimuli (Gras et al, 1990;Ramirez and Orchard, 1990;Duch et al, 1999; for review, see Bräunig and Pflüger, 2001) and that specific octopaminergic neurones invade all brain neuropiles (Bräunig, 1991;Hammer, 1993), including areas in which electrical stimulation elicits aggression (cf. Huber, 1955).…”