Researching the effect of deafness on synaptic plasticity recently led me to think about my sister, who was born with profound hearing loss, and her cochlear implant. A cochlear implant is a small electronic device that simulates a sense of sound. It doesn’t restore sounds, but gives individuals a better understanding of speech. When there’s an acoustic stimulation, like speech or music, the cochlear implant uses a microphone to record it and turn it into a digital code, which is eventually turned into an electrical signal and sent to the brain. Individuals with cochlear implants must learn, through synaptic plasticity, how to interpret this new input. Synaptic plasticity is the ability of synapses to strengthen through repeated use. That’s why you get better at guitar, playing tennis or drawing through practice. Without a cochlear implant, a deaf person’s neurons perform ‘axonal sprouting’- they ignore the inactive neuron, and make connections with neighbouring neurons instead. An interesting effect of this is that when a deaf person without a cochlear implant is signed to (in American Sign Language, for example) their auditory cortex is activated.
Cochlear implants are not a cure; it takes years of practice with behavior therapists to understand how to process this unfamiliar input (see this video to hear examples). Still, the benefits of cochlear implants are clear- a chance to reduce (if not totally eliminate) the barriers and difficulties that deafness can present, as well as improving synaptic plasticity (Tirko and Ryugo, 2014). Recent studies have shown that the benefit of cochlear implants is highly dependent on the age at which they are implanted- they are advantageous before the age of two, but no later than four in prelingually deaf individuals (Kral, 2006). During this sensitive period, the brain is able to learn how to classify the electrical signals sent to it by the cochlear implant.
But the ethics behind cochlear implants are not always clear cut. With hearing loss, one’s deficit is another’s unique perspective, and there is fierce debate within the deaf community as to their efficacy and value (read more about this here). Although cochlear implants can improve the quality of life for certain people, others in the deaf community believe they imply that deafness is a problem to be “fixed”. Deaf communities have their own culture with rich histories, values, traditions, heroes and a unique and expressive language. Expectant parents of children who may experience hearing loss need to consider their values and cultural assumptions about health, independence and the roles of people with mental and physical disabilities, within our families and within our society.
But the ethics behind cochlear implants are not always clear cut. With hearing loss, one’s deficit is another’s unique perspective, and there is fierce debate within the deaf community as to their efficacy and value (read more about this here). Although cochlear implants can improve the quality of life for certain people, others in the deaf community believe they imply that deafness is a problem to be “fixed”. Deaf communities have their own culture with rich histories, values, traditions, heroes and a unique and expressive language. Expectant parents of children who may experience hearing loss need to consider their values and cultural assumptions about health, independence and the roles of people with mental and physical disabilities, within our families and within our society.
REFERENCES
Kral, A. (2006, February). Brain Plasticity under Cochlear Implant Stimulation. Retrieved September 21, 2017, from https://www.karger.com/Article/Abstract/9464
Tirko, N. N., & Ryugo, D. K. (2012). Synaptic Plasticity in the Medial Superior Olive of Hearing, Deaf, and Cochlear-Implanted Cats. The Journal of Comparative Neurology, 520(10), 2202–2217.
Really interesting read. A very good friend of mine is an ASL translator and has spent a lot of time practicing her signs with friends in the deaf community. She's told me how implants are a really polarizing decision because, as you said, deafness can be considered part of a person's unique character (like a pattern of freckles or a specific speech pattern). However, differences like this do not limit what a person can do and who a person can communicate with like deafness can. It's definitely a personal ethical choice.
ReplyDeleteIf you're interested in synaptic plasticity, there is an excellent miniseries episode directed and narrated by Paul Giamatti called 'Breakthrough' (episode: More Than Human). It is an absolutely mindblowing exploration of how far the brain can extend beyond our body. It analyzes how our brains can make machines and computer code part of our body in seconds because of synaptic plasticity. Very cool to watch and follows closely the vein of this discussion. Also analyzes similar ethical questions about enhancement/correction of the human form
This is a great article, and the timing is excellent due to our last TBL addressing the concept of synaptic plasticity in sensory impaired individuals. For the longest time I always saw cochlear implants as a revolutionary technology that everyone would love to have, but an Ethics in Health and Medicine class I took in college opened my eyes a little bit. It never occurred to me that maybe society wants to "fix" these individuals who suffer from deafness more than the individuals themselves want to be "fixed". I think parents and loved ones obviously want their child to live the most "normal" life possible, and struggle with the idea of their child not ever hearing their voice. It's encouraging to see these individuals form their own cultures and accept their condition, but I fear that individuals who are given or decide to get cochlear implants will be ostracized by the very community they thrived in before. All of that being said, I don't have any personal family or acquaintances who are prelingually deaf, so I acknowledge I may still harbor misconceptions.
ReplyDeleteOn a different note, I've know multiple people (including my grandfather) who got cochlear implants to combat age-related hearing loss. I'm assuming that they probably didn't experience the same challenges of "learning to accept the signals," due to their having heard language their entire life. Do you know if I'm correct in this assumption, or could they still have had some challenges?
Cochlear implants tend to be more successful when implanted before the age of two, but no later than four in prelingually deaf individuals (Kral, 2006). During this sensitive period, the brain is able to learn how to classify the electrical signals sent to it by the cochlear implant. However, studies have shown the benefit of cochlear implants if the person receiving the implantation has lost their hearing due to age, disease or disorder. Previously hearing individuals have already developed their auditory plasticity and thus are more successful at learning how to classify the electrical signals sent to the brain by a cochlear implant. Despite this, the success of implantation is highly dependent on how long and well they used to hear.
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