Fig. 4.

Cellular basis of variance adaptation in JO neurons. a Sound-induced antennal movement was measured using laser vibrometry (b). Generator (c) and spike-driven (d) currents were read out via patch clamp recordings of the giant fiber neuron (GFN), after bath application of TTX (c) or with normal saline (d). b–e Amplitude profile of the noise steps used to probe adaptation in different processing stages in JONs (top). Step size is color coded (see legend in d). Magnitude of antennal movement (b), generator current (c), spike-driven currents (d), and CAP (e) to the intensity steps. Adaptation transients first arise in the generator current (c). All panels show one fly with 20 trials per step (c—100 trials per step). f Time constant of adaptation at different stages within JON processing obtained by fitting exponentials to the transients in b–e (time constant averaged across all step sizes). The lack of adaptation in the antennal movements prevented estimation of time constants for the antenna. P values indicate the results of two-tailed tests (sign test for paired data (generator vs. spike), rank sum for unpaired data (LDV (laser Doppler vibrometry) vs. generator, spike vs. CAP)). N = 7 flies for generator/spike, N = 4 for LDV, N = 5 for CAP (number of trials as in b–e). g Strength of adaptation for the signals in b–e was obtained by comparing the responses to the different intensities at step onset vs. steady state. Adaptation values of 1.0 indicate complete adaptation (values can be greater than 1 or smaller than 0 due to noise in the CAP responses). Statistical procedures and N as in f. Error bars in f and g show mean ± standard deviation over flies. h Adaptation in flies mutant for the TRP channel nompC (green, blue, wild-type flies shown in gray for comparison). All mutants adapt for background intensity by shifting their tuning curve. The black diagonal line corresponds to perfect adaptation, complete absence of adaptation would lead to horizontal trends. Adaptation is reduced for soft backgrounds (1/4–1 mm s⁻¹) in the nompC double mutants due to their reduced sound sensitivity. Mean ± s.d. over flies (see Supplementary Fig. 9 for N)