Christopher Bergevin1
1Department of Physics & Astronomy, York University, Toronto, Canada
The auditory periphery is comprised of many disparate elements actively working together to allow for high sensitivity and selectivity. For example, the eardrum appears to move a fraction of the atomic diameter of hydrogen in response to incident sounds at threshold. To achieve such sensitivity, especially in light of thermal noise, biophysical cooperation amongst the elements of the ear is crucial. We argue here that a key principle governing those complex interactions is synchrony. By this we mean the dynamics associated with weakly-coupled self-sustained (i.e., active) oscillators. Here we describe a non-mammalian model, the Anolis lizard, to elucidate how synchrony manifests concurrently at different levels of the periphery. First, within a given inner ear, evidence suggests hair cells metabolically use energy to behave as limit cycle oscillators. Further, they couple together to form groups (or “clusters”) that synchronize, effectively allowing them to increase their sensitivity and selectivity to low-level sounds. Second, by virtue of direct coupling between the tympanic membranes via the interaural canal, the two active ears can also synchrnonize, possibly allowing for improvements in the localization to sounds close to threshold. In parallel, lizards offer an opportunity to explore how synchrony change across the lifespan, given the ability of hair cell regeneration to repair damage to the sensory epithelium. An overarching goal is to explore how these results elucidating cooperativity might be generalized more broadly to the mammalian auditory pathway (e.g., feedback loops in cortical networks).