Blue Sky Science: How do we hear?

How do we hear? My name is Ruth Litovsky. I’m a professor of communication
sciences and disorders, and also in the department of surgery in
the otolaryngology division. The way that we hear is that sounds in
the world reach our ears, from different locations. First they travel through the ear, then
they come through the ear canal and then little tiny bones inside
the middle ear end up vibrating. Those sound vibrations push on this
tiny little window that then gets a special membrane inside
our ear to vibrate. We have a swirly-shaped sensory organ
called the cochlea. Inside the cochlea we have this
membrane that vibrates. When it vibrates, it excites tens of
thousands of little cells. They’re called hair cells. When the hairs move, they have ion
channels that open which bring chemicals into the cells. They send information to a special nerve
called the auditory nerve or the cochlear nerve. That nerve sends information up
to the brain. When those hair cells don’t work, somebody has deafness or severe
to profound hearing loss. That means they don’t understand speech,
they can’t hear music. And when they are deaf, one thing we
can do is have them go through a special surgery. It’s called a cochlear implantation. In that surgery, a very tiny electrode
is placed inside the cochlea. We stimulate it with special pulses
of electricity. What those pulses of electricity do
is stimulate the auditory nerve. The auditory nerve sends information
up to the brain, and somebody can hear that way. We call it bionic hearing. The work in my lab right now is focusing
on a few interesting questions. One of them has to do with whether people
should receive one cochlear implant in one ear, or dual, bilateral cochlear implants. We’re learning that when you give
somebody one cochlear implant, they’re able to understand speech
and language. But they have a very difficult time
knowing where sounds are coming from, hearing speech and
noise is difficult, and they’re working hard. They have a much harder time listening. They exert more effort. When we give them two cochlear
implants, we see a few important benefits. We’re starting to learn that when you
turn both cochlear implants on, instead of just one, it’s easier to listen. We call it release from listening effort.

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