Temporal processing properties of auditory DUM neurons in a bush-cricket
Insects with ears process sounds and respond to conspecific signals or predator cues. Axons of auditory sensory cells terminate in mechanosensory neuropils from which auditory interneurons project into (brain-) areas to prepare response behaviors. In the prothoracic ganglion of a bush-cricket, a cluster of local DUM (dorsal unpaired median) neurons has recently been described and constitutes a filter bank for carrier frequency. Here, we demonstrate that these neurons also constitute a filter bank for temporal patterns. The majority of DUM neurons showed pronounced phasic-tonic responses. The transitions from phasic to tonic activation had different time constants in different DUM neurons. Time constants of the membrane potential were shorter in most DUM neurons than in auditory sensory neurons. Patterned stimuli with known behavioral relevance evoked a broad range of responses in DUM neurons: low-pass, band-pass, and high-pass characteristics were encountered. Temporal and carrier frequency processing were not correlated. Those DUM neurons producing action potentials showed divergent processing of temporal patterns when the graded potential or the spiking was analyzed separately. The extent of membrane potential fluctuations mimicking the patterned stimuli was different between otherwise similarly responding neurons. Different kinds of inhibition were apparent and their relevance for temporal processing is discussed.
KeywordsHearing Insect Temporal filtering Exponential fit Inhibition
The project was funded by the German Science Foundation DFG STU 189/9-1 granted to AS. George Theophilidis, Aristotle University of Thessaloniki, Greece, helped with the permit to catch and export the insects. We thank Martin Göpfert for ongoing support. Heribert Gras gave numerous hints for using the Spike2 languages. Matthias Hennig initiated the use of intensity series of longer block stimuli for characterizing basic properties of temporal processing. We thank two anonymous reviewers for numerous helpful suggestions and Deborah Goggin (A.T. Still University) for meticulous proof reading and improving the English language.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
- Dobler S, Stumpner A, Heller K-G (1994b) Sex-specific spectral tuning for the partner’s song in the duetting bushcricket Ancistrura nigrovittata (Orthoptera: Phaneropteridae). J Comp Physiol A 175:303–310Google Scholar
- Fielden A (1960) Transmission through the last abdominal ganglion of the dragonfly nymph, Anax imperator. J Exp Biol 37:832–844Google Scholar
- Gerhardt HC, Huber F (2002) Acoustic communication in insects and anurans: Common problems and diverse solutions. Chicago University Press, ChicagoGoogle Scholar
- Lang F, Brandt G, Glahe M (1993) A versatile multichannel acoustic stimulator controlled by a personal computer. In: Elsner N, Heisenberg M (eds) Gene, brain, behaviour. Thieme, Stuttgart, p A892Google Scholar
- Marquart V (1985) Auditorische Interneurone im thorakalen Nervensystem von Heuschrecken: Morphologie, Physiologie und synaptische Verbindungen. Dissertation, Universität BochumGoogle Scholar
- Schul J, Bush S, Frederick KH (2014) Evolution of call patterns and pattern recognition mechanisms in Neoconocephalus katydids. In: Hedwig B (ed) Insect hearing and acoustic communication. Animal signals and communication. Springer, Berlin, pp 167–184Google Scholar
- Stumpner A, Ronacher B (1991) Auditory interneurones in the metathoracic ganglion of the grasshopper Chorthippus biguttulus. I. Morphological and physiological characterization. J Exp Biol 158:391–410Google Scholar
- Stumpner A, Ronacher B, von Helversen O (1991) Auditory interneurones in the metathoracic ganglion of the grasshopper Chorthippus biguttulus. II. Processing of temporal patterns of the song of the male. J Exp Biol 158:411–430Google Scholar