HSN activity is subject to negative feedback modulation by egg-laying. A) Without any modulations, HSN will be autonomously oscillating in Ca2+ levels as shown by a theoretical cameleon trace. B) In a physiological ionic environment HSN activity shows sparse spikes, suggesting that it is under inhibitory modulation (four representative traces are shown). C) In egl-15 worms, where egg-laying is prevented due to abnormal vulval muscle development, HSN inhibition is partially removed, with neurons exhibiting unconstrained oscillations about half of the time, similar to the theoretical pattern in panel A. The other half of recordings are silent as indicated by the second trace.