@article {57620, title = {Mechanisms of frequency-specific responses of ω neuron 1 in crickets (Teleogryllus oceanicus): a polysynaptic pathway for song?}, year = {2001}, abstract = {

In crickets (Teleogryllus oceanicus), the auditory interneuron \ω neuron 1 (ON1) responds to sounds over a wide range of frequencies but is most sensitive to the frequency of conspecific songs (4.5 kHz). Response latency is longest for this same frequency. We investigate the mechanisms that might account for the longer latency of ON1 to cricket-like sounds. Intracellular recordings revealed no evidence for appropriately timed postsynaptic inhibition of ON1 that might increase its latency, nor was latency affected by picrotoxin. The onset of excitatory postsynaptic potentials (EPSPs) was delayed for 4.5 kHz stimuli compared with ultrasound stimuli, pointing to a presynaptic locus for the latency difference. When ON1 is stimulated with high frequencies, discrete, apparently unitary EPSPs can be recorded in its dendrite, and these are latency-locked to spikes recorded simultaneously in the auditory nerve. This suggests that input to ON1 from high-frequency-tuned auditory receptor neurons is monosynaptic. In agreement with this, brief ultrasound stimuli evoke a single, short-latency EPSP in ON1. In contrast, the EPSP evoked by a brief 4.5 kHz stimulus consists of an early component, similar in latency to that evoked by ultrasound and possibly evoked by ultrasound-tuned receptors, and a later, dominant component. We interpret the early peak as arising from a monosynaptic afferent pathway and the late peak from a polysynaptic afferent pathway. Multiple-peak EPSPs, with timing similar to those evoked by sound stimuli, were also evoked by electrical stimulation of the auditory nerve.

}, keywords = {audition, auditory interneuron, cricket, excitatory postsynaptic potential, Insect, monosynaptic pathway, omega neuron 1 (ON1), polysynaptic pathway, song, Teleogryllus oceanicus}, author = {Faulkes, Z and Gerald S. Pollack} } @article {50906, title = {The heterospecific calling song can improve conspecific signal detection in a bushcricket species}, journal = {Hearing Research}, year = {2017}, month = {Jan-09-2017}, abstract = {

In forest clearings of the Malaysian rainforest, chirping and trilling Mecopoda species often live in sympatry. We investigated whether a phenomenon known as stochastic resonance (SR) improved the ability of individuals to detect a low-frequent signal component typical of chirps when members of the heterospecific trilling species were simultaneously active. This phenomenon may explain the fact that the chirping species upholds entrainment to the conspecific song in the presence of the trill. Therefore, we evaluated the response probability of an ascending auditory neuron (TN-1) in individuals of the chirping Mecopoda species to triple-pulsed 2, 8 and 20 kHz signals that were broadcast 1 dB below the hearing threshold while increasing the intensity of either white noise or a typical triller song.

Our results demonstrate the existence of SR over a rather broad range of signal-to-noise ratios (SNRs) of input signals when periodic 2 kHz and 20 kHz signals were presented at the same time as white noise. Using the chirp-specific 2 kHz signal as a stimulus, the maximum TN-1 response probability frequently exceeded the 50\% threshold if the trill was broadcast simultaneously. Playback of an 8 kHz signal, a common frequency band component of the trill, yielded a similar result. Nevertheless, using the trill as a masker, the signal-related TN-1 spiking probability was rather variable. The variability on an individual level resulted from correlations between the phase relationship of the signal and syllables of the trill. For the first time, these results demonstrate the existence of SR in acoustically-communicating insects and suggest that the calling song of heterospecifics may facilitate the detection of a subthreshold signal component in certain situations. The results of the simulation of sound propagation in a computer model suggest a wide range of sender-receiver distances in which the triller can help to improve the detection of subthreshold signals in the chirping species.

}, keywords = {acoustic communication, auditory interneuron, Ensifera, signal detection, stochastic resonance}, issn = {03785955}, doi = {10.1016/j.heares.2017.09.011}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0378595517302113}, author = {Abdelatti, Zainab A.S. and Hartbauer, Manfred} } @article {47616, title = {Maintaining acoustic communication at a cocktail party: heterospecific masking noise improves signal detection through frequency separation}, journal = {Journal of Experimental Biology}, volume = {216}, year = {2013}, month = {Oct-24-20132050}, pages = {4655 - 4665}, abstract = {

We examined acoustic masking in a chirping katydid species of the Mecopoda elongata complex due to interference with a sympatric Mecopoda species where males produce continuous trills at high amplitudes. Frequency spectra of both calling songs range from 1 to 80 kHz; the chirper species has more energy in a narrow frequency band at 2 kHz and above 40 kHz. Behaviourally, chirper males successfully phase-locked their chirps to playbacks of conspecific chirps under masking conditions at signal-to- noise ratios (SNRs) of \−8 dB. After the 2 kHz band in the chirp had been equalised to the level in the masking trill, the breakdown of phase-locked synchrony occurred at a SNR of +7 dB. The remarkable receiver performance is partially mirrored in the selective response of a first-order auditory interneuron (TN1) to conspecific chirps under these masking conditions. However, the selective response is only maintained for a stimulus including the 2 kHz component, although this frequency band has no influence on the unmasked TN1 response. Remarkably, the addition of masking noise at 65 dB sound pressure level (SPL) to threshold response levels of TN1 for pure tones of 2 kHz enhanced the sensitivity of the response by 10 dB. Thus, the spectral dissimilarity between masker and signal at a rather low frequency appears to be of crucial importance for the ability of the chirping species to communicate under strong masking by the trilling species. We discuss the possible properties underlying the cellular/synaptic mechanisms of the \‘novelty detector\’.

}, keywords = {ambient noise, auditory interneuron, insects, katydid, novelty detection, selective encoding}, issn = {0022-0949}, doi = {10.1242/jeb.089888}, url = {http://jeb.biologists.org/cgi/doi/10.1242/jeb.089888https://syndication.highwire.org/content/doi/10.1242/jeb.089888}, author = {Siegert, M. E. and Heiner R{\"o}mer and Hartbauer, M.} }