Sensitive thermometry through criticality in voltage-coupled TRP channels

Sensory systems must integrate information from many individually noisy receptors. Here we study the TRP family of ion channels, which are sensitive to a range of physiological stimuli in animals, including hot and cold temperatures. While individual channels open over a 3-5 Kelvin temperature range, thermal imaging organs found in bats and snakes respond to infrared radiation that heats them by just a few milli-Kelvin. Thus, these organs have responses thousands of times more sensitive than individual molecular sensors, but the mechanism through which they achieve this dramatic amplification is unknown. The simple quantifiable function of these organs makes them ideal for studying how information is integrated into coherent and sensitive responses. Here we propose a theoretical model wherein sensitivity arises due to the diverging susceptibility close to a critical point. Individual channels are embedded into a larger dynamical system with positive feedback from the collective response. These dynamics, combined with slower adaptation naturally tunes the dynamical process to the vicinity of a bifurcation critical point. In our model, positive feedback is mediated through voltage, which indeed activates all TRP channels, irrespective of whether they are hot or cold sensitive channels. Our work could shed light into a design principle common for many sensory systems and TRP channels in particular.