Source data for the study "High-pass noise suppression in the mosquito auditory system" in <i>Culex pipiens </i>mosquito.

The Matlab script and the bandpass-filtered source data from the electrophysiological acoustic experiments with male and female Culex pipiens mosquitoes. Each data file contains a series of tones with stepwise increase of frequency. First channel - electrophysiological recording from the auditory neuron(s) by the electrode in the antennal nerve of mosquito. Second channel - signal from the microphone located near mosquito. Stimulation is done via phase-calibrated speakers. hilb.m A script in Matlab, performing the analysis of the instantaneous phase shift between the two recording channels. It takes a fragment of recording cut from the source file, containing a single stimulation tone. data_example/cp126_180.wav Example of such fragment. data_example/cp126_180.wav.txt Output of the script Method of recording and data processing Individual mosquitoes were fixed by attachment to a 10×5 mm copper-covered triangular plate by a flour paste with addition of sodium chloride, as described in Lapshin, Vorontsov, 2013. Focal extracellular recordings from the axons of the antennal nerve were made with glass microelectrodes (1B100F–4, WPI Inc., Sarasota, FL, USA) filled with 0.15 M sodium chloride and inserted at the scape–pedicel joint. After the penetration of the cuticle, the electrodes had a resistance of 10–60 MΩ. Neuronal responses were amplified using a home-made AC amplifier (bandpass 5–5000 Hz). For stimulation, two orthogonally oriented stationary speakers were used; they created a vector superposition of acoustic waves at the point of mosquito antenna, as described in detail in Lapshin, Vorontsov (2019). The mosquito was positioned at the crossing of the axes of two speakers in such a way that the antenna's flagellum was perpendicular to the directions of sound waves originating from each of the two speakers. This approach enabled us to set the desired direction of the acoustic vector relative to the antenna flagellum. A differential microphone (NR-231-58-000, Knowles Electronics, Itasca, IL, USA) positioned next to the mosquito on a micropositioner with axial rotation feature recorded the stimulation signals. Neuronal responses and stimulation signals were digitized using an Е14-440 A/D board (L-Card, Moscow, Russian Federation) at 20 kHz sampling rate, and LGraph2 software. Calibration of the stimulating equipment was performed using the same differential microphone. The differential microphone together with its amplifier was previously calibrated in the far field using a B&K 2253 sound level meter with a B&K 4176 microphone (Brüel & Kjær, Nærum, Denmark). All sound level data in this study are given on a logarithmic scale in dB RMS SPVL (root mean square sound particle velocity level), with a reference level of 0 dB being equal to 4.85 × 10⁻⁵ mm/s. At the beginning of the experiment, as the electrode was gradually advanced into the antennal nerve, the preparation was continuously stimulated with tonal pulses (filling frequency 200 Hz for male mosquitoes, 100 Hz for female mosquitoes, amplitude 60 dB SVPL, duration 80 ms, period 600 ms). In this searching procedure, groups of JO neurons situated orthogonal to the antenna oscillation could be overlooked. To avoid this, the vector of the acoustic wave was periodically changed by 90°. A response amplitude of 500 µV (peak-to-peak) or more was considered sufficient for subsequent measurements. More detailed methodology for measuring the auditory receptor thresholds was described earlier (Lapshin, 2012a, 2012b; Lapshin, Vorontsov, 2013). The phasic properties of the auditory response were measured by stimulating the preparation with tonal pulses that incrementally varied from low to high frequencies (50 dB SPVL and 10 Hz increments for male mosquitoes, 60 dB SPVL and 5 Hz increments for female mosquitoes). The duration of individual pulses was typically 3–4 seconds; however, it could be increased in the presence of occasional spontaneous interference in the neuronal response. The interval between successive pulses was maintained at a constant 0.15 seconds. Both the stimulation control circuit (microphone and the microphone amplifier) and the electrophysiological amplification circuit were pre-calibrated for phase shifts, and the data recorded from the neurons were adjusted accordingly. Before the measurement of the phase shift, signals in both recording channels (acoustic stimulation and neuronal response) were bandpass-filtered using the Sound Forge 10 PRO software (Sony, Japan). The purpose of this procedure was to isolate the fundamental frequency in each channel while simultaneously suppressing harmonics and noise. The filter was adjusted to the stimulation frequency in each case. To control for artifacts of digital frequency filtering, a pre-synthesized sinusoidal signals of 50 and 100 Hz with predetermined phase shifts between the channels (typically –90°, 90°, and 180°) were filtered in the same way. After the filtering procedure, the phase shift between the signals in the two channels remained unchanged. To measure the phase difference between the stimulus and response signals, an instantaneous phase functions for both signals were calculated in Matlab via the Hilbert transform, as was proposed for the analysis of mosquito flight sounds by Aldersley et al. (2014). The phase shift was measured in the second half of a tonal pulse when the system entered a steady-state regime. For each tonal pulse, the median value of the phase shift was taken to plot the phase-frequency characteristic.