Our brains have an auditory cortex on each side.
I hope that made you as dizzy as I feel. Because I am mean that way. HA!
But really, the pathways between your ears (or my cochlear implants) and the auditory cortex on each side of the brain make things a little more complicated:
But let’s simplify a bit:
There is more to hearing than just sound going in your ears. There is how the sound gets to your brain, and then what your brain does with it. But there is also a part of your brain that has to remember sounds, and there are different parts of your brain for sounds and speech. So that’s why it gets complicated.
But for this, we are focused on these pathways of how sound gets from outside my head to into my brain to be understood – and how bilateral (two, one on each side) cochlear implants makes a difference.
The important thing to understand here is that it is not like the one implant only affects one part of my brain.
It does, actually, have the potential to affect both sides of the brain.
It has the potential to affect both sides, in some way, because there are pathways that cross across. Here’s the simple version of that “complicated” picture above:
To keep things simple, what this shows is how sound from the cochlea can go to that auditory cortex, but it can also go to the other one on the other side!
Here is the graphic from yesterday, from the email I got from Cochlear Community, which talked about bilateral cochlear implants:
You can see from the blue and red arrows at the bottom, how the sound can cross to the other side.
But here is the thing about that cross-over, where the red and blue arrows cross – no one knows until the second implant is activated – whether the cross-over ENHANCES sound or CANCELS sound. They have no way to test that yet on individuals, and so this is why I was cautioned that I may lose sound after the second implant or when the second processor is added on January 19th.
Michael Chorost, who wrote REBUILT, said it this way (talking about the complicated diagram at the top of this blog, and my cochlear implants being years of upgrades since what he experienced and wrote about):
“It’s well-known that the right ear sends most of its signal to the left hemisphere for high-level processing, and that the hemispheres have only partial access to what each other knows. But there is significant crossover as the signal ascends neural pathways to the auditory cortex. A quick glance at a diagram from Yost’s Fundamentals of Hearing makes that clear.”
(In the 4th edition of Yost, from 2000, it is page 228.)
So what this means is that having one cochlear implant has the possibility to affect both sides of the brain.
Getting a second cochlear implant, with the training will do the same thing, and then teach both sides to also enhance the other.
That feels automatic.
Except there is also the possibility that the cross-over cancels each other out, make it a starting-over kind of thing.
We didn’t know which way I would go.
Would I lose everything, and have to re-learn from scratch?
We knew not EVERYTHING, because at least this time I would know WHAT to listen FOR – even crossover signals that cancelled each other out would not wipe out the sound-memory that has been developed. I would remember sound this time, know it in a way that I did not know with the first surgery. So even if I had to start over, at least I would know where I was going this time.
Or, would adding the second implant just give me MORE sound (from the other side of my head) and give me direction (to be able to know where sound comes from)?
Or, would the second processor activate crossover in such a way that sound was actually enhanced? Greater clarity, more discrimination between sounds, increased speech recognition – even in noisy environments? More pitch perception, more tone discernment, more ability to understand even music?
We would not know until the second implant is activated, they said.
It is a hard thing to wait the four weeks between surgery and activation. There has to be a waiting period because brain swelling has to go down enough that it is safe to activate the new 32 (for a total of 64) electrodes in my brain without causing any further damage. Activation Day, or A-Day as it is known in the cochlear implant community, cannot come soon enough. It isn’t until then that you know whether or not surgery was successful, and not until the subsequent mappings that you know HOW successful.
And so I wait, urging January 19th to arrive, so that I can find out whether or not this second surgery was successful. And as I wait, I sit and wonder whether my crossover will cancel or enhance my hearing.
Until last night.
Last night, I was eating chips and realized for the first time that I could hear myself eating chips. It was the weirdest thing! I have not heard before this digital sound of your own chip crunching.
And that made me think and ponder, even about my earlier in the week observations that I could hear my own voice better than I could before surgery. It was significant then, because there was the chance that after surgery the static-sound (the electrodes picking up the sound of brain noise inside my head) would be so much I would not be able to hear with my “old” processor (the first one, on the left), and that I may lose my hearing and my speech while my brain heals.
All of that was possible, even though I do not yet have the processor on the right, so I can hear no NEW sounds from the OUTSIDE of my head
until Activation Day.
So no NEW sound is coming IN to me, but already my brain is processing sound DIFFERENTLY!
This was confirmed when I was thinking about that the awful beeping sound I hate, the one that could drive me crazy because it sounds like an alarm clock going off in your head, or like the heart monitor at the hospital, except it is in my head and no one can turn it off… I just have to wait for the brain swelling to go down, and my adjustment to the new brain noise. So the static is horrible, and it is frightening. I can’t stand it! That static sound is what makes cochlear patients go crazy (literally), and what makes them quit wearing their processors and give up on the Cochlear Implant before ever getting to the point of discovering how to understand sound.
(If you want to hear what it is like to learn how to hear with cochlear implants, going from the static sound to learning to hear digitally, CLICK HERE for a sentence example, HERE for a song example, and HERE for a music example.)
Except what I realized as I thought about that awful static sound is that the ONLY thing that relieves it at all is leaving the processor ON on my left side. Any time I remove my left processor, that alarm goes off on the right, and it is horrible. So much that my greatest recovery challenge is being able to fall asleep with the alarm going off in my head. It’s awful.
BUT, look what that means!
If my left processor is affecting the other side, then it means my crossover is GOOD!
And if already I can now hear my own voice, and hear myself crunching chips, then it means the crossover is not just good, but it is the ENHANCING sort!
This is the best news! It is very exciting to me, and of a great comfort to me. I do not have to wait four weeks (three more now) until January 19th to find out if it surgery was successful, because now I know it was! I do not have to wait to find out if my crossover will cancel or enhance, because now I know it is enhancing already!
I will still have to work. I will still have to remove my left processor and do my listening rehab with the right processor, to teach that side of my brain what it needs to know.
But it was learning all along!
It’s so amazing!
I think it will need it’s own listening rehab, of course, but I do not think I will be starting from scratch.
I think having sound coming at me – into me – from both sides will be some difficult, and sometimes emotional, adjustments and adapting-ness.
But it’s going to be okay.
And so here I am, one week since surgery, ready to get the 20 staples in my head taken out tomorrow morning, and already knowing that my crossover ENHANCES instead of cancels.
I am so relieved, and so excited! It’s an amazing thing!
It’s a miracle, truly!
I am so grateful for being led to this insight, and for the peace and confidence understanding it brings me.
I am grateful for the people who have been caring for me and helping me.
I am grateful for the blessings I received before and after surgery, all of which promised a quick recovery.
I am grateful for a covenant God who keeps His promises.
After my first cochlear implant, I was not even awake yet after a week.
Today, not only am I awake, but I am more and more alert each time I wake up after sleeping, and I am feeding myself, regaining motor skill function, walking without my walker, folding my own laundry, able to still hear, able to still speak, and healing very well.
It leaves me in awe.
This morning my chapter to read was Helaman 3, and it made me want to claim an “unconquerable spirit”.
I knew, with Lachoneus, that the only way to be delivered is to cry unto the Lord for strength.
I have experienced, like Gidgiddoni, that when you do pray unto the Lord, He will tell you where to go and what to do. He will show the way.
Even if it is just the pathway from your ears to your brain, from sound to understanding.
It is a miracle, I say.
My cochlea is the size of a pea.
What technology it is that can implant a device into my brain, and connect it to that pea-sized space so that I can HEAR sound, and not just see it.
Rhapsody in Hue: a Deaf Symphony by Cole Holland (the son of the real life Mr. Holland’s Opus)