The Penny

Example is not the main thing in influencing others. It is the only thing.

[Thursday, July 9, 2009]

Another Trip to Good Old Steve

Day-glo cochlea. Three rows of outer hair cells at the top and a row of 
inner hair cells below. The nuclei of the inner hair cells are stained blue, 
and you can see orangey red neurons attached to all of the hair cells. 
There are no actual hairs on hair cells, but you can see why 
somebody that "hair cells" would be an apt name.

Laynie went to see her friend Steve the Audiologist this morning, because she had been experiencing discomfort and odd sensations related to her implant. Her map was adjusted almost a month ago, and it was better for a while, but the problem came back.

Laynie understood a word on the way up to The Listening Center! We were in the elevator, and as we approached the fifth floor, the little computer lady voice said, "This is level five." Laynie turned to me and asked, "Did that just say number five?"

Steve turned down the stimulation levels on the implant. No surprise. And goodness, Steve is picking up signing skills.. or showing the skills that he has. He handled the normal greetings and had a short conversation with Laynie about her teaching, without much help from me. Anyway...

He did not turn down the power evenly across electrodes. For one thing, electrode 10 seems to be back off. I don't know if Laynie knows that. But I could see Steve's computer screen from my interpreting-friendly vantage point closer to his side of the table. Ha. So aside from electrode 10 being off (was it already?)... electrodes 1-3 were turned down relatively more than the rest. Steve commented that low frequency sounds have a tendency to overpower higher frequency sounds, and he doesn't want that to happen. Electrodes 8, 9, and 11 (mid-high frequencies) were barely turned down at all, so now the map is more even, for lack of a better word. Not the ski slope that it was. The old map is on program 2, in case Laynie wants to compare them, or if she needs more stimulation after Monday's surgery. You never know.

Steve actually tried to turn down the lower pitched electrodes even more, but Laynie mixed up some of her Ling sounds after he did that, so he brought those electrodes up. Too bad she doesn't know what the speech sounds are "supposed" to sound like and can't give feedback on whether they sound distorted.

Oh, the Ling sounds are six speech sounds (phonemes) that cover the entire frequency spectrum of speech: mm, ah, oo, ee, sh, and ss. The sounds that a patient confuses can help the audiologist know which frequencies need adjusting.

Sooo... what else... Oh, Laynie asked if her experience of tingling and pain in the ear is unusual. Steve said not terribly, but it depends on the kind of patients. This was the part I enjoyed. Ah, new knowledge.

Although there is a spectrum of responses, people who are born deaf and receive a cochlear implant as adults often fall into one of two categories. They are either hypersensitive to sound, where every noise bothers them (think Laynie's first 6 weeks but continual), or they are hyposensitive to sound, where they can take a lot without saying it is loud. This is because they have not had much experience with sound, so they are either very sensitive to it, or they don't know when it is too much. 

Apparently Laynie falls into the second category. Steve pointed out that Laynie has never told him that a sound was painfully loud. He has achieved "comfortably loud" with her, but he's always able to push it more (he doesn't, but he could). There does not seem to be a limit to her tolerance. That is perceptual, though. Her body, of course, does have a tolerance limit, and maybe it has been exceeded. Keep in mind that the cochlear implant works by directing electricity in close proximity to nerve endings. You don't want it to be too strong. You want it to be just strong enough. Remember how last time we found that at some level her brain realizes that the stimulation was too much? It was activating the acoustic reflex, which is meant to protect the ear against very loud sounds. Her stimulation levels were turned down last time and again today, and hopefully that will do until her next appointment, on August 25, when her second implant will be activated.

Laynie also asked why she has felt that tingly feeling a couple of times when her processor was off. Obviously it is not related to loud sounds, since she can't hear anything without her processor. Steve had an explanation for this too. Smarty pants. He said this is not necessarily a bad thing, because it probably means that her brain is learning how to listen.

Laynie has spent her life without meaningful auditory stimulation. With her hearing aid, sounds didn't make sense, so her brain went, "Unimportant, ignore." Laynie couldn't tolerate having her hearing aid on very much (at least not in the five years I have known her), and she only used it for music and movies. Otherwise, it quickly became annoying. All she got was meaningless, garbled noise. She never understood one word with her hearing aid. Now, she has clear sounds coming in, and her brain seems to have realized that these sounds have meaning. They are organized. They make sense. Her brain doesn't know how to process them just yet, but it has figured out that it should not ignore them. When her implant is off, the auditory nerve is still mildly active. It always is, just as all of our nerves are.. it's called a resting potential. Her brain basically ignored everything that came from that nerve before, so it never noticed the resting potential. But now that her brain knows the nerve is bringing in meaningful information, it is very attentive to that nerve. It doesn't know exactly what is meaningful, so it is thinking that the resting potential could be something to listen to. It is trying to pull in information, even when nothing is there. Her brain is searching for sound. Yay! Laynie's brain is so smart. It is learning to listen.


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