@article {57994, title = {Lateralization of Travelling Wave Response in the Hearing Organ of Bushcrickets}, year = {2014}, abstract = {

Travelling waves are the physical basis of frequency discrimination in many vertebrate and invertebrate taxa, including mammals, birds, and some insects. In bushcrickets (Tettigoniidae), the crista acustica is the hearing organ that has been shown to use sound-induced travelling waves. Up to now, data on mechanical characteristics of sound-induced travelling waves were only available along the longitudinal (proximal-distal) direction. In this study, we use laser Doppler vibrometry to investigate in-vivo radial (anterior-posterior) features of travelling waves in the tropical bushcricket Mecopoda elongata. Our results demonstrate that the maximum of sound-induced travelling wave amplitude response is always shifted towards the anterior part of the crista acustica. This lateralization of the travelling wave response induces a tilt in the motion of the crista acustica, which presumably optimizes sensory transduction by exerting a shear motion on the sensory cilia in this hearing organ.

}, doi = {10.1371/journal.pone.008609010.1371/journal.pone.0086090.g00110.1371/journal.pone.0086090.g00210.1371/journal.pone.0086090.g00310.1371/journal.pone.0086090.s00110.1371/journal.pone.0086090.s002}, url = {https://dx.plos.org/10.1371/journal.pone.0086090}, author = {Arun Palghat Udayashankar and K{\"o}ssl, Manfred and Nowotny, Manuela} } @article {57949, title = {Mechanical basis of otoacoustic emissions in tympanal hearing organs}, year = {2014}, abstract = {

Tympanal hearing organs of insects emit dis- tortion\–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\’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\’s response to external pure tones, but abol- ished the emission\’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.

}, keywords = {DPOAE, Insect, laser Doppler vibrometry, locust, tympanum}, doi = {10.1007/s00359-014-0914-2}, url = {http://link.springer.com/10.1007/s00359-014-0914-2}, author = {M{\"o}ckel, Doreen and Nowotny, Manuela and K{\"o}ssl, Manfred} } @article {57891, title = {Processing of simple and complex acoustic signals in a tonotopically organized ear}, year = {2014}, abstract = {

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.

}, keywords = {bushcricket, crista acustica, Electrophysiology, insect hearing, laser Doppler vibrometry, Tettigoniidae}, doi = {10.1098/rspb.2014.1872}, url = {https://royalsocietypublishing.org/doi/10.1098/rspb.2014.1872https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2014.1872}, author = {Hummel, Jennifer and Wolf, Konstantin and K{\"o}ssl, Manfred and Nowotny, Manuela} }