A bifurcation integrates information from many noisy ion channels and allows for milli-Kelvin thermal sensitivity in the snake pit organ

The thermal imaging organ of pit vipers is a remarkable example for how biological systems integrate information from many noisy sensors into a collective response. Single nerve fibers innervating the organ robustly respond to milli-Kelvin changes in temperature, even though the opening probability of each individual temperature-sensitive ion channel only changes by 0.1%. Here, we propose a mechanism for the integration of this noisy molecular information into an amplified response. Amplification arises due to proximity to a dynamical bifurcation, separating a regime with frequent and regular firing of action potentials (APs), from one with irregular and infrequent firing. Near the transition, AP frequency can have an extremely sharp dependence on temperature, and most of the information in molecular receptors is efficiently transmitted to AP firing even if additional noise corrupts the signal or readout. Our model explains several key features of experimental data. Most significantly, it predicts that the coefficient of variation in the distribution of times between APs decreases for larger AP frequency. It also suggests that the intrinsic channel timescale is slower than the timescale of the cell's voltage dynamics, thereby leading to memory in the state of the channels.