C. elegans: Sensing the low-frequency profile of amplitude-modulated ultrasound
Tianyang Long, Linzhou Xie, Mayibaier Pulati, Quan Wen, Xiasheng Guo, Dong Zhang
Ultrasonics 2023 · 10.1016/j.ultras.2022.106887
Abstract
Several research groups have demonstrated that C. elegans can respond to pulsed ultrasound stimuli, and elucidating the underlying mechanisms is necessary to develop ultrasound neuromodulation. Here, amplitude-modulated (AM) ultrasound is applied to C. elegans, and its behavioral responses are investigated in detail. By loading surface acoustic waves (SAWs) onto free-moving worms on an agar surface, a carrier wave with a frequency of 8.80 MHz is selected. The signal is modulated by a rectangular or sinusoidal profile. It is demonstrated that sinusoidal modulation can produce similar responses in worms to rectangular modulation, with the strongest responses occurring at modulation frequencies of around 1.00 kHz. Meanwhile, the behavioral response is relatively weak when the ultrasonic signal is unmodulated, that is, when only the carrier wave is applied. At modulation frequencies other than 100.00 Hz to 10.00 kHz, the worms respond weakly, but when a second modulation frequency of 1.00 kHz is introduced, an improvement in response can be observed. These results suggest that C. elegans may sense the low-frequency envelope and respond to amplitude-modulated ultrasonic stimuli like an amplitude demodulator. MEC-4, an ion channel for touch sensing, is involved in the behavioral response of C. elegans to ultrasound in the present setup.
Abstract via europepmc.
Exposures
Exposure 1: 8.8 MHz surface-acoustic-wave stimulation with single and double amplitude modulation
Target: c elegans neurons — “C. elegans moving on an agar slice (whole body exposed)”
Device: custom-built · interdigital transducer on 128-degree Y-X LiNbO3 (SAW device), 8.80 MHz central frequency
| Waveform | pulsed, other_patterned | |
|---|---|---|
| Fundamental frequency (kHz) | 8,800 | ✓✓✓ |
| Pulse duration (ms) | not reported | ⚑ |
| Pulse repetition frequency (Hz) | 50, 100, 1,000, 10,000, 100,000, 311,000swept | ✓✓✓⚑ |
| Duty cycle (%) | 50 | ✓✓✓⚑ |
| Sonication duration (s) | 0.2 | ✓✓✓ |
| Free-field pressure (kPa) | 500 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not applicable | |
| In-situ pressure (kPa) | not applicable | |
| In-situ Isppa (W/cm²) | not applicable | |
| In-situ Ispta (W/cm²) | not applicable |
The 8.80 MHz carrier was amplitude modulated by rectangular or sinusoidal envelopes at modulation frequencies of 0.05 to 311 kHz (single-AM), or by two envelopes (double-AM, second at 1.00 kHz). Each worm received ten 200-ms exposures at 1-min intervals.
Flags from extraction
exposures[0].unspecified_domain.pressure_kpa— Pressure is a rough estimate in agar derived from laser-vibrometer substrate displacement assuming water properties; the authors call it only a rough estimation. Domain not clearly free-field or in situ.exposures[0].timing.pulse_repetition_frequency_hz— Values are the modulation frequencies fm1 (Table 1), listed as the PRF equivalent for rectangular modulation; for sinusoidal modulation there are no discrete pulses.exposures[0].timing.duty_cycle_pct— 50 % applies to the single rectangular (single-R) protocol only; sinusoidal and double-AM have different envelopes.exposures[0].timing.pulse_duration_ms— Not stated; protocol is amplitude modulation of a carrier.n_subjects— Worm numbers appear only in figure brackets, not in text.