Biophysics, neural processing and robotics of the lizard ear, a highly directional sensor

Forfattere

  • Jakob Christensen-Dalsgaard Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark

Resumé

The ear of lizards shows strongly directional responses with up to 40 dB differencesinsensitivitytoipsi-andcontralateralstimulation.Thedirectionality is generated by a simple principle: strong acoustical coupling of the eardrums through the large mouth cavity. Our laser vibrometry measurements show that the lizard ear is a two-input system with approximately 0 dB contralateral transmission gain in a 2 kHz frequency band. This transmission is boosted by resonances in the large, open tympanic cavities. Probably because of these resonances, the interaural delay is approximately three times larger than the arrival-time differences at the lizard eardrums. Since already the ear is directional, the subsequent neural processing may be much simpler than in mammals, for example, where directionality is based on neural computation. Our neurophysiological experiments show that binaural comparison is based on contralateral inhibition with no apparent segregation of time and intensity processing. This simple computation generates a strongly directional lateralization that is suf cient to orient the animal. This has been shown by robot simulations, where the ear is modelled by a simple three- impedance acoustical analog. Implementation of the model in a digital signal processor and subsequent neural processing based on binaural comparison produces a robust directional response.

Referencer

Brittan-Powell, E. F., Christensen-Dalsgaard, J., Tang, Y., Carr, C. E., and Dooling, R. (2010). “The auditory brainstem response in two lizard species,” J. Acoust. Soc. Am. in press.

Christensen-Dalsgaard, J. (2005). “Directional hearing in non-mammalian tetrapods,” in Sound Source Localization edited by A. N. Popper and R. R. Fay (Springer- Verlag, New York), pp. 67-123.

Christensen-Dalsgaard, J., and Carr, C. E. (2008). “Evolution of a sensory novelty: the tympanic ears and the associated neural processing,” Brain Res. Bull. 75, 365- 370.

Christensen-Dalsgaard, J., and Kanneworff, M. (2005). “Binaural interactions in the frog dorsal medullary nucleus,” Brain Res. Bull. 66, 522-525.

Christensen-Dalsgaard, J., and Manley, G. A. (2005). “Directionality of the lizard ear,” J. Exp. Bio. 208, 1209-1217.

Christensen-Dalsgaard, J., and Manley, G. A. (2008). “Acoustical coupling of lizard eardrums,” JARO 9, 407-416.

Clack, J. A. (1997). “The evolution of tetrapod ears and the fossil record,” Brain. Behav. Evol. 50, 198-212.

Feng, A. S., and Christensen-Dalsgaard, J. (2007). “Interconnections between the ears in nonmammalian vertebrates,” in The Senses: A comprehensive reference edited by A. Basbaum A. et al. (Elsevier), vol 3, p. 217-224.

Fletcher, N. H. (1992). Acoustic systems in biology (Oxford University Press, Oxford).

Manley, G. A. (1981). “A review of the auditory physiology of the reptiles,” Prog. Sens. Physiol. 2, 49-134.

Manley, G. A. (1990). Peripheral Hearing Mechanisms in Reptiles and Birds (Springer- Verlag, New York).

Manley, G. A. (2002). “Evolution of structure and function of the hearing organ of lizards,” J. Neurobiol. 53, 202-211.

Michelsen, A., and Rohrseitz, K. (1995) “Directional sound processing and interaural sound transmission in a small and a large grasshopper,” J Exp Biol 198, 1817- 1827.

Shaikh, D., Hallam, J., Christensen-Dalsgaard, J., and Zhang, L. (2009) “A Braitenberg Lizard: Continuous Phonotaxis with a Lizard Ear Model,” in Lecture Notes in Computer Science 5602 (Springer-Verlag, New York ), pp. 439-448.

Vossen, C., Christensen-Dalsgaard, J., and van Hemmen, J. L. (2010). “An analytical model of the lizard pressure-gradient receiver ear,” J. Acoust .Soc. Am., in press.

Wever, E. G. (1978). The Reptile Ear (Princeton University Press, Princeton).

Zhang, L., Hallam, J., and Christensen-Dalsgaard, J. (2006). “Modelling the lizard auditory periphery,” in From animals to animats 9. Proceedings of 9th international conference on simulation of adaptive behaviour, edited by S. Nol et al. (Springer), pp. 65-76.

Yderligere filer

Publiceret

2009-12-15

Citation/Eksport

Christensen-Dalsgaard, J. (2009). Biophysics, neural processing and robotics of the lizard ear, a highly directional sensor. Proceedings of the International Symposium on Auditory and Audiological Research, 2, 29–36. Hentet fra https://proceedings.isaar.eu/index.php/isaarproc/article/view/2009-03

Nummer

Årg. 2 (2009): Binaural Processing and Spatial Hearing

Sektion

2009/1. Physiological measures and models of binaural hearing

Licens

Authors who publish with this journal agree to the following terms:

a. Authors retain copyright* and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.

b. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.

c. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).

*From the 2017 issue onward. The Danavox Jubilee Foundation owns the copyright of all articles published in the 1969-2015 issues. However, authors are still allowed to share the work with an acknowledgement of the work's authorship and initial publication in this journal.