Temporal resolution and neuronal integration in the auditory pathway of the locust
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1
Humboldt-University Berlin, Germany
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2
Bernstein Center for Computational Neuroscience Berlin, Germany
Two key functions of auditory processing in insects are predator avoidance and mate recognition, the latter involving localization and evaluation of a potential conspecific mate. During the acoustic communication for mating purposes male grasshoppers typically exhibit a species-specific calling song to which a female may respond. The male can then use the female song for a phonotactic approach.
The auditory system of grasshoppers comprises approximately 60 excitatory receptor neurons (RN) per ear which is located in the first abdominal segment. The RNs convey information to local interneurons (LN) located in the metathoracic ganglion. These LNs give inhibitory and excitatory input to the ascending neurons (AN), which in turn project to the brain. While the firing rates of the RNs correspond to basic features of the auditory stimulus (such as sound intensity), the ANs extract specific, rather complex features of the auditory stimulus (such as lateralization of the sound source, pause duration between stimuli and onset intensity). Thus, an important part of auditory processing already takes place at the metathoracic level.
In the present study, we explore a) the temporal resolution of LNs and ANs, and b) how LNs and ANs integrate short auditory stimuli. Therefore, we conduct experiments stimulating with short broadband clicks (duration 40 µs), and simultaneously perform intracellular recordings. We determine single and double click detection thresholds for LNs and ANs, and vary inter-click intervals as well as relative click intensity in the double click paradigm. Thus, we can determine integration in LNs and ANs as a function of both intensity and time.
In the migratory locust (Locusta migratoria) acoustic communication plays only a minor role for mating; however, previous studies have revealed that the neuronal structures underlying auditory preprocessing have been evolutionary conserved across grasshopper species (Neuhofer et al. 2008). This makes the migratory locust a good model system for investigating basic neuronal properties of the grasshopper auditory system.
The integration of double clicks of auditory receptors in insects is consistent with an energy detector model (Tougaard 1996, Gollisch et al. 2002). Hence, in receptors the detection threshold for double click stimuli is lower than for single clicks. Similar effects appear to apply for the majority of the LNs due to the purely excitatory input from the RNs, but nonlinear effects resulting from the network activity of excitatory and inhibitory synaptic inputs take place in the ANs.
References
Gollisch, T., Schütze, H., Benda, J., and Herz, A. V. M. (2002). Energy integration describes sound-intensity coding in an insect auditory system. J Neurosci 22, 10434–10448.
Neuhofer, D., Wohlgemuth, S., Stumpner, A., and Ronacher, B. (2008). Evolutionarily conserved coding properties of auditory neurons across grasshopper species. Proc R Soc B 275, 1965-1974.
Tougaard, J. (1996). Energy detection and temporal integration in the noctuid A1 auditory receptor. J Comp Physiol A 178, 669-677.
Keywords:
Auditory system,
Grasshoppers,
neuronal integration,
temporal resolution
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for student poster award)
Topic:
Sensory: Audition
Citation:
Wirtssohn
S and
Ronacher
B
(2012). Temporal resolution and neuronal integration in the auditory pathway of the locust.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00242
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Miss. Sarah Wirtssohn, Humboldt-University Berlin, Berlin, Germany, sarah-wirtssohn@web.de