A bifurcation amplifies and integrates a noisy signal from many molecular thermo-receptors

In various biological systems information from many individually noisy molecular receptors must be integrated into a collective response. A striking example is the thermal imaging organ of pit vipers. Single neurons in the organ reliably respond to mK temperature increases, 1000 times more sensitive than single thermo-TRP ion channels, whose opening probability barely rises – by less than 0.1%. Here, we propose a mechanism for the integration of this molecular information into an amplified neural response. In our model TRP channels are embedded into the electrical dynamics of the neural membrane. Due to the channels' intrinsic voltage sensitivity, these dynamics contain a bifurcation separating a monostable regime, with regular firing of action potentials (APs), from a bistable regime, with rare and stochastic APs. Near the transition, AP frequency has a sharp dependence on temperature, naturally accounting for the 1000-fold increase in sensitivity from single channels to neuronal firing. Furthermore, near the bifurcation most of the information about temperature available in the channels' kinetics can be easily read out by the timing of APs. While tuning to such bifurcation points typically requires fine-tuning of parameters, we propose that having feedback act from the order parameter (AP frequency) onto the control parameter naturally maintains the system in the vicinity of the bifurcation.