Bernhard Ronacher

Research interests

A) Neuronal processing of acoustic communication signals in grasshoppers

Many grasshopper species use acoustic signals to find a mate. The receiver in these communication systems has to solve two demanding tasks, i.e., to recognize whether the signal is coming from a conspecific and to localize it. Signal recognition is rendered difficult by noise and distortions of the signal imposed on its way through the biotope. Directional hearing is impeded by the small size of the animals, which leads to a deterioriation of directionality cues. Since mate finding obviously affects the fitness, there is a high selective pressure laid on the optimization of neuronal processing of such communication signals. Correspondingly, the grasshopper Chorthippus biguttulus shows a remarkable performance in gap detection and directional hearing, which in several respects is not inferior to that of vertebrates, including man. These capacities must be based on an "innate hardware" - the grasshoppers overwinter as eggs, and therefore have no chance to learn from their parents. Furthermore, the animals must solve these tasks with not too many auditory afferents and interneurones (many of which can be identified). These features of the grasshopper's communication make it a well suited system to investigate how a small nervous system extracts the relevant features from noisy and distorted signals. Apart from external noise the precision of neuronal processing is constrained by intrinsic noise that causes a considerable trial-to-trial variability visible in the spiking responses of afferents and interneurones. Due to their rather small nervous system, grasshoppers probably cannot get rid of this variability by simply averaging over a large population of parallel neuronal elements.

We use behavioural experiments and electrophysiological methods in order to better understand how the animals' nervous system processes information on sound patterns and on sound direction. In addition, in a collaboration started with Andreas Herz' group in the SFB 618 and now continued with Susanne Schreiber at the Humboldt University, we applied stimulus reconstruction and modelling techniques to the spike train data recorded from auditory neurons. By these approaches we intend to reveal how external stimuli are represented along the auditory pathway of these insects and how much and what kind of information is transmitted by different neurones. We also aim at understanding the evolutionary lines along which such communication systems may have evolved. The limitations imposed on processing capacity by a rather small number of neurons available for such tasks could give more general insights into the selective forces that have shaped the evolution of small brains.

B) GENART (functional genomics of speciation)

This project was initiated by PD Dr. Frieder Mayer (Museum für Naturkunde, MfN) to bring together groups from the Museum für Naturkunde, the Humboldt-Universität, the University Potsdam, the Leibniz-Institut für Zoo- und Wildtierforschung, the Berlin Centre for Genomics in Biodiversity Research, and the Berlin Centre for Medical Systems biology (BIMSBI at Max Delbrück Centre, MDC) to join efforts to better understand the genetic basis of speciation processes. Combining various behavioural tests and genomic analyses we investigate pairs of closely related species. This project is funded by a grant from the Leibniz-Gemeinschaft.

C) Navigation and 3-D spatial orientation of desert ants

Joint project with Rüdiger Wehner (Zürich), and H. Wolf (Ulm), funding by the DFG and the Volkswagen Stiftung.

Desert ants of the genus Cataglyphis are famous for their ability to perform large scale foraging excursions from which they precisely return to their nest by path integration. To compute and continuously update their 'home vector', the ants need two types of information: about the current direction of their path, and about the respective distance travelled in that particular direction. While the celestial compass that is used by ants and bees to infer their travelling direction is well understood (e.g. Wehner 1997), the ant's distance estimation, the 'odometer', remained enigmatic until 2006 (see Wittlinger et al. 2006). However, experiments in which the ants were trained to walk over a series of hills have added a further twist to the navigation story. They revealed unexpected capabilities of these animals to perform path integration in the third dimension. The results indicate that the ant's distance estimation is much more elaborate than previously thought. We now aim at a better understanding (i) of how these ants measure travelling distances in hilly terrain, (ii) which algorithms describe the ant’s path integration, and (iii) how the ants achieve the necessary accuracy since path integration is inherently prone to the accumulation of errors. These fascinating insects may help to address a general open question about brain function: how complex computational tasks can be boiled down to simpler approximative solutions.

Publications (since 2000)

Grasshopper publications

  1. Ronacher B (2012/13) Processing of species-specific signals in the auditory pathway of grasshoppers. In Hedwig B (ed) Topics of acoustic communication in insects. Springer Verlag
  2. Stange N, Ronacher B (2012) Population differences in song characteristics and morphologies of the grasshopper Chorthippus biguttulus L. J Comp Physiol A, in press
  3. Ronacher B, Stange N (2012) Processing of acoustic signals in grasshoppers – a neuroethological approach towards female choice. invited review, J Physiol (Paris) online
  4. Clemens J, Ronacher B (2012) Nonlinear computations underlying temporal and population sparseness in the auditory system of the grasshopper. J Neurosci in press
  5. Stange N, Ronacher B (2012) Grasshopper calling songs convey information about condition and health of males. J Comp Physiol A 198: 309-318
  6. Neuhofer D, Ronacher B (2012) Influence of different envelope maskers on signal recognition and neuronal representation in the auditory system of a grasshopper. Plos-ONE, 10.1371/journal.pone.0034384
  7. Clemens J, Kutzki O, Ronacher B, Schreiber S, Wohlgemuth S (2011). Efficient transformation of an auditory population code in a "small" sensory system. PNAS 108(33): 13812-13817.
  8. Einhäupl A, Stange N, Hennig, RM, Ronacher B (2011) Attractiveness of grasshopper songs correlates with their robustness against noise. Behav. Ecol. 22(4): 791-799
  9. Neuhofer D, Stemmler M, Ronacher B (2011) Neuronal Precision and the Limits for Acoustic Signal Recognition in a Small Neuronal Network. J Comp Physiol A 197: 251-265
  10. Wohlgemuth S, Vogel A, Ronacher B (2011) Encoding of amplitude modulations by auditory neurons of the locust: influence of modulation frequency, rise time, and modulation depth. J Comp Physiol A 197: 61-74
  11. Clemens J, Weschke G, Vogel A, Ronacher B (2010) Intensity invariance properties of auditory neurons compared to the statistics of relevant natural signals in grasshoppers. J. Comp Physiol A 196: 285-297
  12. Creutzig F, Benda J, Wohlgemuth S, Stumpner A, Ronacher B, Herz AVM (2010) Timescale-invariant pattern recognition by feed-forward inhibition and parallel signal processing. Neural Computation 22: 1493-1510
  13. Creutzig F, Wohlgemuth S, Stumpner A, Benda J, Ronacher B, Herz AVM (2009) Time-scale invariant representation of acoustic communication signals by a bursting neuron. J. Neurosci 29: 2575 - 2580
  14. Neuhofer D, Wohlgemuth S, Stumpner A, Ronacher B ( 2008) Evolutionarily conserved coding properties of auditory neurons across grasshopper species. Proc Roy Soc Lond B, 208: 1965-1974
  15. Weschke G, Ronacher B (2008) Influence of sound pressure level on the processing of amplitude modulations by auditory neurons of the locust. J Comp Physiol A, 194: 255-265
  16. Schmidt A, Ronacher B, Hennig RM (2008 The role of frequency, phase and time for processing amplitude modulated signals by grasshoppers. J Comp Physiol A, 194: 221-233
  17. Ronacher B, Wohlgemuth S, Vogel A, Krahe R (2008) Discrimination of acoustic communication signals by grasshoppers: temporal resolution, temporal integration, and the impact of intrinsic noise. J Comp Psychol.22: 252-263
  18. Vogel A, Ronacher B (2007) Neural correlations increase between consecutive processing levels in the auditory system of locusts. J Neurophysiol 97, 3376-3385
  19. Wohlgemuth S, Ronacher B (2007) Auditory discrimination of amplitude modulations based on metric distances of spike trains. J Neurophysiol 97, 3082-3092
  20. Vogel A, Hennig RM, Ronacher B (2005) Increase of neuronal response variability at higher processing levels as revealed by simultaneous recordings. J Neurophysiol 93: 3548-3559
  21. Ronacher B, Franz A, Wohlgemuth S, Hennig H (2004) Variability of spike trains and the processing of temporal patterns of acoustic signals – problems, constraints, and solutions. J Comp Physiol A 190: 257-277
  22. Ronacher B, Hennig RM (2004) Neuronal adaptation improves the recognition of temporal patterns in a grasshopper. J Comp Physiol A190: 311-319
  23. Ronacher B, Hoffmann C (2003). Influence of amplitude modulated noise on the recognition of communication signals in the grasshopper Chorthippus biguttulus. J Comp Physiol A, 189: 419-425
  24. Machens CK, Schütze H, Franz A, Stemmler MB, Ronacher B, Herz AVM (2003). Auditory receptor neurons preserve characteristic differences between conspecific communication signals. Nature Neurosci 6: 341-342
  25. Prinz P, Ronacher B (2002). Temporal modulation transfer functions in auditory receptor fibres of the locust (Locusta migratoria L.). J Comp Physiol A 188, 577-587
  26. Franz A, Ronacher B (2002) : Temperature dependence of time resolution in an insect nervous system. J Comp Physiol A 188, 261-271
  27. Krahe R, Budinger E, Ronacher B (2002) Coding of a sexually dimorphic song feature by auditory interneurons of grasshoppers: The role of leading inhibition. J Comp Physiol A 187, 977-985
  28. Machens CK, Prinz P, Stemmler MB, Ronacher B, Herz AVM (2001b): Discrimination of behaviorally relevant signals by auditory receptor neurons. Neurocomp. Vol 38-40, 263-268
  29. Machens CK, Stemmler MB, Prinz P, Krahe R, Ronacher B, Herz AVM (2001a): Representation of acoustic communication signals by insect auditory receptor neurons. J. Neurosci. 21, 3215-3227
  30. Ronacher B, Krahe R, Hennig M (2000): Effects of signal duration on the recognition of masked communication signals by a grasshopper. J Comp Physiol A, 186, 1065-1072
  31. Ronacher B, Krahe R (2000) Temporal integration versus parallel processing: coping with the variability of neuronal messages in directional hearing of insects. Europ. J. Neurosci. 12, 2147-2156
  32. Krahe R, Larsen ON, Ronacher B (2000) Directional hearing is only weakly dependent on the rise time of acoustic stimuli. J. Acoust. Soc. Amer. 107, 1067-1070

Ant publications

  1. Wintergerst & Ronacher (2012) Discrimination of inclined path segments by the desert ant Cataglyphis fortis. J Comp Physiol A 198: 363-373
  2. Lebhardt F, Koch J, Ronacher B (2012) The polarization compass dominates over idiothetic cues in path integration of desert ants. J Exp Biol 215: 526-535
  3. Heß D, Koch, J, Ronacher B (2009) Desert ants do not rely on sky compass information for the perception of inclined path segments. J Exp Biol 212: 1528-1534
  4. Ronacher B (2008) Path integration as the basic orientation mechanism of desert ants. Myrmecological News 11, 53-62 (invited review)
  5. Grah G, Ronacher B (2008) 3-D orientation in desert ants: Context-independent memorisation and recall of sloped path segments. J Comp Physiol A 194: 517-522
  6. Grah G, Wehner R, Ronacher B (2007) Desert ants do not acquire and use a three-dimensional global vector. Frontiers in Zoology 4:12 doi:10.1186/1742-9994-4-12
  7. Ronacher B, Westwig E, Wehner R (2006) Integrating two-dimensional paths: Do desert ants process distance information in the absence of celestial compass cues? J Exp Biol 209: 3301-3308
  8. Grah G, Wehner R, Ronacher B (2005) Path integration in a three-dimensional maze: ground distance estimation keeps desert ants (Cataglyphis fortis) on course. J Exp Biol 208: 4005-4011
  9. Wohlgemuth S, Ronacher B, Wehner R (2002). Distance estimation in the third dimension in desert ants. J Comp Physiol A 188, 273-281
  10. Wohlgemuth S, Ronacher B, Wehner R (2001) Ant odometry in the third dimension. Nature 411, 795-798
  11. Ronacher B, Gallizzi K, Wohlgemuth S, Wehner R (2000): Lateral optic flow does not influence distance estimation in the desert ant Cataglyphis fortis. J. Exp. Biol. 203, 1113-1121

Other publications

  1. Ronacher B (2011) Ein “Zick-Zack“-Experiment. In H. Zappe (ed.) Von der Lust am Unbekannten. Humboldts Erben auf Forschungsreisen. Panama Verlag, Berlin 2011 ISBN 978-3-938714-14-0
  2. Ronacher B (2010) Die Entwicklung des Instituts für Biologie seit 1993. pp 607-610 in R vom Bruch, H-E Tenorth (Hsg.) 1810-2010 – 200 Jahre Universität unter den Linden. Geschichte der Universität zu Berlin. Akademie-Verlag Berlin (2010)
  3. Granada, A, Hennig M, Ronacher B, Kramer A, Herzel HP (2009) Phase response curves: elucidating the dynamics of coupled oscillators. Methods in Enzymology 454: 1-27
  4. Efler D, Ronacher B (2000). Evidence against a retinotopic template matching in honeybees' pattern recognition. Vision Research 40, 3391-3403