Fig. 5: Statistical analysis of spike signals from Cd²⁺–NR interactions.

A total of 786 spike events were recorded from a 5-μM Cd²⁺ solution in the presence of 5-mM CsCl. The background noise level was measured at 0.4 fm. a, Histogram of spike durations (dwell times, τ), showing an exponential decay with a time constant of 149 ± 16 ms. b, Histogram of waiting times between consecutive spikes. An exponential fit (dashed blue line) yields a spike rate of 3.8 ± 0.4 s⁻¹. c, Histogram of spike amplitudes with a double Gaussian fit (dashed line), indicating a mean magnitude of 7.2 fm and a standard deviation of 3.5 fm. d, Histogram of the detrended beat frequency signal, centred at zero. The blue histogram represents the background noise, whereas the gold histogram corresponds to the sensing signal. For additional analysis, see appendix E in the Supplementary Information.