Figure 5.
Ultrasound efficacy depends on pulse repetition frequency and duty cycle. A, The response (black circles, mean ± SEM) of wild-type animals to a train of ultrasound pulses plotted as a function of pulse repetition frequency. The duty cycle was held constant at 50% in all cases, ensuring that all stimuli deliver the same amount of energy. The smooth curve (green) shows a simulation of the sensitivity of TRN currents to sinusoidal mechanical indentations (Eastwood et al., 2015). B, The response (black circles, mean ± SEM) of wild-type animals as a function of duty cycle. Because the pulse repetition rate was 1 kHz in all cases, a duty cycle of 5, 10, 25, 50, 75, 100% corresponds to a pulse width of 50 μs, 100 μs, 250 μs, 500 μs, 750 μs, and 1 ms (continuous wave, no off epochs), respectively. The green curve shows the level of TRN activation expected from the frequency filtering shown in panel A (Materials and Methods for modeling details). Temperature increase (orange circles, mean ± SEM, n = 5) as a function of duty cycle. The smooth curve (orange) is a quadratic fit to the data and is included for visual clarity. A, B, The carrier frequency was 10 MHz, the stimulus amplitude was 1 MPa, and the stimulus duration 200 ms. The dotted line shows the unstimulated reversal frequency.