01910nas a2200181   4500008004100000245007300041210006900114520135500183653001001538653001101548653002901559653001101588653001301599100002001612700002101632700002001653856005501673       2014                        eng d00aMechanical basis of otoacoustic emissions in tympanal hearing organs0 aMechanical basis of otoacoustic emissions in tympanal hearing or3 a<p>Tympanal hearing organs of insects emit dis- tortion&ndash;product otoacoustic emissions (DPOAes), which in mammals are used as indicator for nonlinear cochlear amplification, and which are highly vulnerable to manipu- lations interfering with the animal&rsquo;s physiological state. Although in previous studies, evidence was provided for the involvement of auditory mechanoreceptors, the source of DPOAe generation and possible active mechanisms in tympanal organs remained unknown. Using laser Dop- pler vibrometry in the locust ear, we show that DPOAes mechanically emerge at the tympanum region where the auditory mechanoreceptors are attached. Those emission- coupled vibrations differed remarkably from tympanum waves evoked by external pure tones of the same frequency, in terms of wave propagation, energy distribution, and loca- tion of amplitude maxima. Selective inactivation of the auditory receptor cells by mechanical lesions did not affect the tympanum&rsquo;s response to external pure tones, but abol- ished the emission&rsquo;s displacement amplitude peak. These findings provide evidence that tympanal auditory recep- tors, comparable to the situation in mammals, comprise the required nonlinear response characteristics, which during two-tone stimulation lead to additional, highly localized deflections of the tympanum.</p>
10aDPOAE10aInsect10alaser Doppler vibrometry10alocust10atympanum1 aMöckel, Doreen1 aNowotny, Manuela1 aKössl, Manfred  uhttp://link.springer.com/10.1007/s00359-014-0914-202072nas a2200205   4500008004100000245008700041210006900128520133100197653001601528653002001544653002201564653001901586653002901605653001801634100002101652700002101673700002001694700002101714856013101735       2014                        eng d00aProcessing of simple and complex acoustic signals in a tonotopically organized ear0 aProcessing of simple and complex acoustic signals in a tonotopic3 a<p>Processing of complex signals in the hearing organ remains poorly understood. This paper aims to contribute to this topic by presenting investigations on the mechanical and neuronal response of the hearing organ of the tropical bushcricket species Mecopoda elongata to simple pure tone signals as well as to the conspecific song as a complex acoustic signal. The high-frequency hearing organ of bushcrickets, the crista acustica (CA), is tonotopically tuned to frequencies between about 4 and 70 kHz. Laser Doppler vibrometer measurements revealed a strong and dominant low-frequency-induced motion of the CA when stimulated with either pure tone or complex stimuli. Consequently, the high-frequency distal area of the CA is more strongly deflected by low-frequency-induced waves than by high-frequency-induced waves. This low-frequency dominance will have strong effects on the processing of complex signals. Therefore, we additionally studied the neuronal response of the CA to native and frequency-manipulated chirps. Again, we found a dominant influence of low-frequency components within the conspecific song, indicating that the mechanical vibration pattern highly determines the neuronal response of the sensory cells. Thus, we conclude that the encoding of communication signals is modulated by ear mechanics.</p>
10abushcricket10acrista acustica10aElectrophysiology10ainsect hearing10alaser Doppler vibrometry10aTettigoniidae1 aHummel, Jennifer1 aWolf, Konstantin1 aKössl, Manfred1 aNowotny, Manuela  uhttps://royalsocietypublishing.org/doi/10.1098/rspb.2014.1872https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2014.1872