Event

Biological systems must integrate and amplify signals which are faint and insignificant at the level of individual sensory receptors. In this talk I will argue that organisms can use the diverging susceptibilities found near critical points to naturally amplify sensory information. While critical points in general require fine-tuning, I will further show that these systems can exploit a feedback scheme that makes use of the same diverging susceptibility to robustly tune to the critical point.   Crucially, this feedback must come from the amplified output back onto the unamplified input, implementing a scheme that is reminiscent of self-organized criticality.  I will present three specific examples that my group has been exploring; amplification of weak thermal signals through proximity to a saddle-node bifurcation in the pit organ of snakes, sound amplification through Hopf bifurcations in the mammalian cochlea, and amplification of weak chemical signals in an active lattice critical point used by bacteria for chemosensing.