Subject: Re: Auditory efferents and phase locking From: "Richard F. Lyon" <DickLyon@xxxxxxxx> Date: Wed, 31 Aug 2011 19:45:43 -0700 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Matt, I'm not among those who think the efferent feedback is merely protective, but it's a possibility. When there's no efferent feedback to turn them down, the OHCs just work as hard as they can, which saturates at high enough levels. Presbycusis is largely a lack of OHC activity, whether it's modulated by efferent feedback or not. Loss of OHCs or their ability to provide amplification causes a huge loss of gain, and corresponding threshold elevation. Along with this comes a reduction in "compression", which would also be expected from lack of efferent feedback, but that's a somewhat more subtle effect. Still, it's surprising to me that people haven't found a good way to assess the effect of missing the feedback. Dick At 11:33 AM +1000 9/1/11, Matt Flax wrote: >I understand this point of view, that gain-control is primarily >protective ... if you follow that line of literature and theory, we have >the classical view of hearing ... augmentation of the passive travelling >wave to get the active travelling wave. Where local amplification away >from the best frequency acts to restrict movement... to protect. > >In this argument, we can only assume that emissions occur from backwards >travelling waves ... do you agree - or am I jumping the gun like Usain >Bolt (2011 - world championships) ? > >So here I sever the classical view from the non-classical view. > >We have to turn back to experiments which look at how the waves travel >in the Cochlea. > >Ren.T. clearly shows (in most of his body of work) forward active >travelling waves (in the base). Wilson (1980) agrees with him. Ruggero >similarly is most likely in agreement [1]. > >And all of this is in the base of the Cochlear ... what happens in the >apex is a toatally different story. > >Matt >p.s. If it was to protect, then why is Presbycusis so bad ? > >[1] Ruggero, M.A., "Comparison of group delays of 2f- f distortion >product otoacoustic emissions and cochlear travel times", Acoustics >Research Letters Online 5 (2004), pp. 143. > >On Wed, 2011-08-31 at 16:54 -0700, Richard F. Lyon wrote: >> Perhaps the >> gain-control role is primarily protective, as many have speculated?