Pascal Martin from Laboratoire Physico-Chimie...

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Pascal Martin from Laboratoire Physico-Chimie Curie, Paris, will give a seminar "Hair cells : sensors, oscillators and non-linear amplifiers of sound in the ear" on Friday December 7th at 11:00 a.m. in the Pierre Cotton room.

The seminar will be of general interest. The topic - the hearing process - involves mechanical traveling waves, regenerative amplification, frequency selective signal processing and critical oscillators. This will be a very stimulating seminar at the interface of physics and biology.
The seminar will be preceded by a coffee break at 10h45, also in Pierre Cotton Room.

Abstract :
The cochlea –the auditory organ of the inner ear− is endowed with a longitudinal array of mechanosensory hair cells that are each tuned to detect a characteristic sound frequency. Sound produces travelling waves that deliver the energy associated with a given sound frequency to a specific group of cells in the organ. As a result, different frequencies are detected by different cells. In this talk, I will review recent work showing that mechanical activity by the hair cells is key for frequency analysis of sound. In particular, the hair cell can power noisy spontaneous oscillations of its mechanoreceptive hair bundle, resulting in frequency-selective, nonlinear amplification of periodic inputs. I will discuss how the interplay between ion channels, molecular motors, and Ca2+ feedback explains the oscillatory behavior, how mechanical coupling between neighboring calls can overcome the physical limit to detection that is imposed by intrinsic sources of noise, and how mechanical gradients at cellular and molecular levels can tune different cells to different frequencies. Overall, our work promotes a general physical principle of auditory detection that is based on the activity of “critical oscillators”, which are active dynamical system poised in a vicinity of a Hopf bifurcation.

Invitation : Loïc Le Goff and Anne Sentenac
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