Re: cochlear parameters ?

[Matt Flax <flatmax@xxxxxxxx>]

Hi Mohammad,

Not as straight forward as you would think !
Consider that you are talking about a system which has elements in the
mechanical, electrophysiological and neurological domains ... they are
connected in such a way that they are time dependent and each has
nonlinear properties - even the mechanics!

The following questions have answers in the literature [1] for example.
Generally the firing rate varies, maximum firing rate would depend on
species. Adaptation is a very tricky question, as it is not a simple
mechanism i.e. time dependent.
There are models which attempt to apply random noise to a signal to
model firing rates ... it is believed to be a random process, can't
think of a reference for that off the top of my head ... but you should
be able to find them ...
Time constant - are you talking about travel time ? they are the fastest
afferents in the body I believe - and firing threshold is zero for those
with spontaneous firings and varies for steady neurons e.g. 20 to 100
spikes per second in Liberman's cats.
> -The ratio between threshold of the firing neurons of highest and
> lowest nerve fibers : ?
> - sponataneous firing rate of cochlea's output neurons : ?
> - Maximum firing rate : ?
> - Adaptation time scale of these neurons : ?
> - The approximate ratio between initial and steady state firing rate
> of such neurons  : ?
> - time constant and firing threshold : ? [are these parameters
> specifically much different from the other typical neurons in the
> auditory pathway ?]
> 
> - Attack and Release time constants of Outer Hair Cells ;   ?

Hair cells are instantaneous limiters. This was shown in my theory and
the implementation of a physiological model. One of the founding
concepts of the Compression Wave Cochlear Amplifier.
Surprised ?
Old theory suggests that hair cells may be modelled as a linear 1st
order system, which would have at least one time constant. However it is
well known that OHCs do not suffer loss of motility at high frequencies
(more then 100 kHz). Also biological membranes are nonlinear ...
consequently old theories fail to explain why OHCs don't have a
significant frequency limit. Check [2] (I think that is the correct
reference).

> 
> - and finally the Inner hair cell typical time constant : ?

As per the OHCs they have similar homeostatic properties however the
OHCs have a specialised anion transporter called Prestin [3] which duals
as the physical motor. Although the stereocilia also act as motors.
Other differences exist, especially on higher neurological levels where
Calcium is currently thought to be a trigger.

> 
> Thanks in advance for your help.

no worries

> 
> Regards
> M.Abdollahi
> 
[1] @ARTICLE{liberman:1978,
  author = {Liberman, M.C.},
  title = {{Auditory-nerve response from cats raised in a low-noise
chamber}},
  journal = {The Journal of the Acoustical Society of America},
  year = {1978},
  volume = {63},
  pages = {442--455},
  number = {2}
}

[2] @article{kros:2006,
  title={{Tuning in to cochlear hair cells}},
  author={Kros, C.J. and Evans, M.G.},
  journal={The Journal of Physiology},
  volume={576},
  number={1},
  pages={7},
  year={2006},
  publisher={Physiological Soc}
}

[3] @article{zheng:2000,
  title={{Prestin is the motor protein of cochlear outer hair cells}},
  author={Zheng, J. and Shen, W. and He, D.Z.Z. and Long, K.B. and
Madison, L.D. and Dallos, P.},
  journal={Nature},
  volume={405},
  number={6783},
  pages={149--155},
  year={2000}
}