January 5th, 2014 by Elizabeth | Tags: Audiology, AVT, Cochlear Implant, Facts, Hearing Aids, New Parents, Spoken Language | 16 Comments »
Whenever people ask me what I do, I tell them that I help families of children with hearing loss teach their children to listen and speak without the use of sign language. Inevitably, the next question I hear is, “HOW?!?” Those poor people. Little do they know that they’ve opened up the door for me to talk them to death about my one of my favorite subjects: The Auditory Brain. Most people think that hearing loss is an ear problem. Makes sense, right? But that answer fails to look into the complicated, incredible processes that help us communicate. It’s important for the general public to understand, but it’s even more important for the families of children with hearing loss and those who work with them.
Ears are incredible. Even those weird-looking folds on the outside of your ear (the pinna) are specially formed to capture sound and send it down your ear canal. The bones in your middle ear — the tiniest bones in your body — work together to send the sound through the system. The snail-shaped cochlea is filled with many, many tiny hair cells that move when sound waves pass through the fluid that surrounds them, stimulating the auditory nerve and sending impulses to the brain. All of those steps are important, but here’s the thing: if we could get those electrical impulses to the brain without needing any of those intermediary structures, a person could still experience sound. That’s what happens with the electrical signals of a cochlear implant (or an auditory brain stem implant). Those electrical signals travel up the auditory nerve to the auditory centers of the brain.
That’s when the real magic starts to happen. You see, no matter how good your hearing aids or how well programmed your cochlear implants, those sound waves or electrical impulses are meaningless until they are processed by the auditory cortex in the brain and become linked to sounds, words, or music. The brain has fantastic capacity to grow and change, and it is one of the crucial components to success with a cochlear implant. The brain has what we call experience dependent plasticity — a fancy way of saying “what happens to you shapes your brain.” For a child whose parents have chosen a listening and spoken language outcome, the more words that go in, the more listening experiences that child has, the more that center of their brain will grow. Conversely, if a person has gone through a long period of auditory deprivation (relying primarily on visual communication and/or not using hearing technology), that part of the brain gets pirated away to be used for different purposes (use it or lose it).
The brain is also all about connection. All of the cells in your brain (called neurons) connect to one another to form complex webs. These connections are called synapses. When a child hears the sound of a word and then puts it together with its meaning, a synapse is formed. Over time, those connections build stronger and stronger webs that enable us, for example, to hear the word “dog” and know not only what that means but also to connect it to a web of other information we know and have experienced (names of our family pets, different types of dogs, the sound a dog makes, stories we’ve read about dogs, etc.). If a child’s access to input is limited, either because they are not in a listening, talking environment, do not have appropriate hearing technology, or are not wearing their technology all waking hours, these synapses can be weaker, disorganized or even disconnected. The richer, fuller input a child receives going IN, the better speech, language, comprehension, and cognition they are going to have coming OUT. Remember: the quality of the INPUT determines the quality of the OUTPUT.
The importance of the brain is why many leaders in the field have called hearing loss a “neurodevelopmental emergency.” If children with hearing loss do not receive access to sound and appropriate intervention as soon as possible, the auditory centers of their brain may never regain the infinite potential they have at birth to become fully functioning members of a world full of speech and sound. It is also one reason why we see varied results among cochlear implant users. If we — people with hearing loss, parents, professionals, and the public at large — could stop thinking “ears” when we think about hearing loss and start thinking BRAIN, we would be one step closer to achieving optimal outcomes!