Chaire Blaise-Pascal de Jonathan Ashmore
Organisé par : Jonathan Ashmore (Univ. College London)
Jonathan ASHMORE, britannique, biophysicien et physiologiste de grand renom de la mécanique de la cochlée, organe sensoriel de l’audition. Il a été accueilli à l’Institut Pasteur sur une Chaire internationale de recherche Blaise-Pascal, en tant que lauréat de la promotion 2007.
Ressources en ligne
- The mechanics of hearing and sound amplification by the cochlea (le 11 décembre 2008) — Jonathan Ashmore
Premier exposé présenté par Jonathan Ashmore dans le cadre du séminaire complémentaire, Physiologie cochléaire : actualités, du cours 2008–09 de Christine Petit, professeur titulaire de la chaire Génétique et physiologie cellulaire au Collège de France.
This lecture covers the question of how the cochlea amplifies incoming sound. It is now well appreciated that the inner ear contains a biological hearing aid which is responsible for amplifying sound and without this process we are effectively deaf. The cellular basis of this mechanism originates from the operation of the cochlear outer hair cells, a specialised population of cells found in mammals. These cells are fast force generators and can feed back energy into the otherwise passive mechanical components of the ear.
I describe some of the recent findings about outer hair cells, how they depend for their force generation on a motor molecule, named prestin, which has been identified as membrane bound transporter molecule. How such molecules can be used to generate cellular and macroscopic forces will be a central theme of this lecture.
The lecture will be prefaced by a short discussion on a recent mathematical model which suggest that the coiling of the mammalian cochlea can assist low frequency hearing.
- Synaptic processing in the cochlea and the dynamic range problem (le 8 janvier 2009) — Jonathan Ashmore
Second exposé présenté par Jonathan Ashmore dans le cadre du séminaire complémentaire, Physiologie cochléaire : actualités, du cours 2008–09 de Christine Petit, professeur titulaire de la chaire Génétique et physiologie cellulaire au Collège de France.
The information about the frequency, intensity and timing of sound arriving at ear is encoded by the sensory cells of the cochlea, the inner hair cells. The frequency components in a complex sounds are analysed on a moment-by-moment basis as described in the first lecture, and this information is then relayed to auditory nerve by populations of inner hair cells. Information about the intensity of the sound is carried by the stratified activity of populations of auditory nerve fibres, although there is still dispute about the precise mechanisms: this is known as the dynamic range problem.
In this lecture I shall be discussing new and recent experiments carried out at the Institut Pasteur during tenure of a Chaire Blaise-Pascal which address this latter point. Using imaging methods it has proved possible to identify synaptic activity at the inner hair cells of the mouse and to characterise some of the events occurring during electrical activation of the synapse.
The lecture will be prefaced by a short discussion of some recent results obtained by a group at M.I.T. which visualise the tectorial membrane, a further mechanically active structure within the mammalian cochlea.
Jonathan Ashmore (Univ. College London)
Jonathan Ashmore is Bernard Katz Professor of Biophysics au Ear Institute, University College London (UCL School of Life & Medical Sciences).