Tympanal mechanics and neural responses in the ears of a noctuid moth

Hofstede, Hannah M. and Goerlitz, Holger R. and Montealegre-Z, Fernando and Robert, Daniel and Holderied, Marc W. (2011) Tympanal mechanics and neural responses in the ears of a noctuid moth. Naturwissenschaften, 98 (12). pp. 1057-1061. ISSN 0028-1042

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Official URL: http://dx.doi.org/10.1007/s00114-011-0851-7

Abstract

Ears evolved in many groups of moths to detect the echolocation calls of predatory bats. Although the neurophysiology of bat detection has been intensively studied in moths for decades, the relationship between
sound-induced movement of the noctuid tympanic membrane and action potentials in the auditory sensory cells (A1 and A2) has received little attention. Using laser Doppler vibrometry, we measured the velocity and displacement of the tympanum in response to pure tone pulses for moths that were intact or prepared for neural recording. When recording from the auditory nerve, the displacement of the
tympanum at the neural threshold remained constant across frequencies, whereas velocity varied with frequency. This suggests that the key biophysical parameter for triggering action potentials in the sensory cells of noctuid moths is tympanum displacement, not velocity. The validity of studies on the neurophysiology of moth hearing rests on
the assumption that the dissection and recording procedures do not affect the biomechanics of the ear. There were no consistent differences in tympanal velocity or displacement when moths were intact or prepared for neural recordings for sound levels close to neural threshold, indicating that this and other neurophysiological studies provide good estimates of what intact moths hear at threshold.

Item Type:Article
Additional Information:Ears evolved in many groups of moths to detect the echolocation calls of predatory bats. Although the neurophysiology of bat detection has been intensively studied in moths for decades, the relationship between sound-induced movement of the noctuid tympanic membrane and action potentials in the auditory sensory cells (A1 and A2) has received little attention. Using laser Doppler vibrometry, we measured the velocity and displacement of the tympanum in response to pure tone pulses for moths that were intact or prepared for neural recording. When recording from the auditory nerve, the displacement of the tympanum at the neural threshold remained constant across frequencies, whereas velocity varied with frequency. This suggests that the key biophysical parameter for triggering action potentials in the sensory cells of noctuid moths is tympanum displacement, not velocity. The validity of studies on the neurophysiology of moth hearing rests on the assumption that the dissection and recording procedures do not affect the biomechanics of the ear. There were no consistent differences in tympanal velocity or displacement when moths were intact or prepared for neural recordings for sound levels close to neural threshold, indicating that this and other neurophysiological studies provide good estimates of what intact moths hear at threshold.
Keywords:Lepidoptera, Auditory threshold, Neurophysiology, Moth auditory biomechanics
Subjects:C Biological Sciences > C770 Biophysical Science
C Biological Sciences > C990 Biological Sciences not elsewhere classified
Divisions:College of Science > School of Life Sciences
ID Code:6266
Deposited By: Fernando Montealegre-Z
Deposited On:08 Oct 2012 09:57
Last Modified:26 Feb 2013 20:47

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