From: rowe@pender.ee.upenn.edu (Mickey Rowe)
Newsgroups: k12.ed.science
Subject: Re: deafness
Date: 21 Jan 93 23:09:11 GMT
Organization: University of Pennsylvania

In article <39669.2B5D07A4@puddle.fidonet.org>
     Hollie.Svetich@p0.f14.n346.z1.fidonet.org (Hollie Svetich) writes:

>...Ever since then I have been interested in the deaf and the
>language they use.  

You would probably be very interested in a book written by Oliver
Sacks in 1989.  The book is called _Seeing Voices : A Journey into the
World of the Deaf_.  Oliver Sacks is a neurologist, and he wrote the
book after spending time at Gallaudet University, which is a
University composed largely of hearing impaired students.  

>What I am wondering is how some people become deaf or partially deaf.

I'm not certain, but I think that the principle cause of deafneas
prior to birth is the mother contracting german measles virus, and the
principle causes of hearing loss after birth are direct injury (like
hanging out at rock concerts) and inner ear infections.  Unfortunately
the tubes which equalize pressure across our eardrums connect to tubes
going to our mouth and nose.  Sometimes infecting microorganims travel
up those tubes and destroy the crucial structures in the inner ear.

>Is it possible to cure or at least help some of the deaf?  I know
>that hearing aids can help but how much can they help?  

How much a hearing aid can help is dependent upon the nature of the
deafness.  One of the reasons that people become hearing impaired as
they get older is that the bones in the middle ear become rigid.
Hearing aids can help to compensate for this by increasing the energy
moving the bones.  Hearing aids can be quite sophisticated little
devices now that integrated circuits have gotten so small.  The better
hearing aids can be adjusted so that they only amplify sounds with
frequencies which the hearing impaired person has difficulty sensing.

If the deafness occurs due to a problem with the inner ear, hearing
aids may not really help.  There is still something that can be done
for these people, however, as long as their auditory nerve is intact.
For the past 15 years, bioengineers have been working on devices
called cochlear implants.  The cochleus is a snail shaped structure in
your inner ear.  It contains the sensory cells which translate sounds
into nerve signals.  Deafness which arises from the destruction of
those cells can be compensated for with direct electrical stimulation
of the nerves which would normally receive their stimulation from the
sensory cells in the cochlea.

There are a lot of difficulties in constructing these devices, but the
principle one is that in a hearing individual, each of the nerve
fibers responds only to sound energy at particular frequencies.  In
order to imitate what the cochlea does, you would need to connect a
lot of differnt wires, each one sending an electrical signal only when
it receives energy at its particular frequency, and then only to a
selected group of nerve fibers.  As people have gotten more experience
with building these devices, they've been building them with more and
more such wires.  Although it's nothing at all like what Jamie Somers
had in "The Bionic Woman", some people with these implants are capable
of recognizing some sounds including, I believe, human speech.

If the auditory nerve is destroyed in a person, then there's nothing
that we can currently do to provide them with hearing in any form.

>I am considering a career in working with the hearing impaired and
>would welcome any information!  

If you do choose to work with deaf people, you're going to find that
there is a community of people that don't want to have their hearing
restored.  If you read Oliver Sacks' book you may come to appreciate
something of why that might be.

>Thank You!

You're welcome.  I hope that helped.

>uucp: uunet!m2xenix!puddle!346!14.0!Hollie.Svetich
>Internet: Hollie.Svetich@p0.f14.n346.z1.fidonet.org

Mickey Rowe     (rowe@pender.ee.upenn.edu)
Xref: sparky k12.ed.science:2167 alt.save.the.earth:1478