SynapseWords
In the works... here's a preview...
Based on personal interviews with:
Dr. David Ryugo, Professor of Otolaryngology & Neuroscience at Johns Hopkins Medical School.
His manuscript - "Restoration of Auditory Nerve Synapse in Cats by Cochlear Implants"- is being sent to Science Magazine on November 8th, and should be published within a month or so after that.
Dr. David Ryugo has a very special collection of cats. He recently took me to the lower levels of Traylor Hall, at Hopkins Medical School, where he keeps them... a dozen or so furry white felines which cost him hundreds of thousands of dollars to purchase, and which are all congenitally deaf (deaf from birth). They are the only such population in the world, and they are perfect animal models for studying deafness.
In deaf humans, cochlear implants have restored hearing for many, but not all recipients. Dr. Ryugo wanted to know why... He performed tests to better comprehend synaptic plasticity in the auditory nerve, which is vital in understanding the beneficial effects of cochlear implants in congenitally deaf children. Dr Ryugo seeks to identify the latest stage at which implants could be placed in deaf children, so that they could still obtain some benefit. (If cochlear implants are inserted too late- if parents are hesitant, in other words- these instruments may not work at all to improve hearing.)
Previously, the clinical consensus as to why cochlear implants worked for some patients but not others was that language development prior to deafness lead to the best outcomes. Among congenitally deaf children, the younger the age of implant activation, the better the aural language results. These clinical experiences imply that uncorrected congenital deafness introduces irreversible abnormalities in the developing central nervous system. In mammalian models of congenital deafness, the synaptic structure of auditory nerve endings is abnormal. Ryugo wondered if the status of auditory nerve synapses represented an important link to the success or failure of cochlear implants.
He studied defects in the auditory nerve... specifically, he studied myelinated auditory never fibers called the endbulbs of Held. They transmit signals from the auditory nerve fiber to the postsynaptic cell with a high degree of fidelity. Congenitally deaf animals exhibit endbulbs with marked reduction in branching. Moreover, they contain fewer synaptic vesicles. These structural abnormalities have been associated with transmission irregularities at the synapse of endbulbs that may underlie loss of temporal resolution in the midbrain in neonatally deafened cats.
Ryugo stimulated deaf cats via a 6-channel cochlear implant and found that their endbulb synapses resembled those from normal hearing cats, after 3 to 6 months. I'm just brushing over the results here- until I write my article- but Ryugo hypothesizes that the changes observed after cochlear implantation at this crucial synapse enable the development of integrative and cognitive brain functions reflected in aural and oral communication in deaf children...
Beyond this angle, Dr. Ryugo is also interested in studying how chemicals could be imbedded in cochlear implants, to improve hearing. A pharmacological approach to improving deafness.
Side-note: Dr. Ryugo is one of the most enthusiastic people I've ever met. If you find yourself in Baltimore, look him (and his cats) up. A true delight.
-MGW-
Based on personal interviews with:
Dr. David Ryugo, Professor of Otolaryngology & Neuroscience at Johns Hopkins Medical School.
His manuscript - "Restoration of Auditory Nerve Synapse in Cats by Cochlear Implants"- is being sent to Science Magazine on November 8th, and should be published within a month or so after that.
Dr. David Ryugo has a very special collection of cats. He recently took me to the lower levels of Traylor Hall, at Hopkins Medical School, where he keeps them... a dozen or so furry white felines which cost him hundreds of thousands of dollars to purchase, and which are all congenitally deaf (deaf from birth). They are the only such population in the world, and they are perfect animal models for studying deafness.
In deaf humans, cochlear implants have restored hearing for many, but not all recipients. Dr. Ryugo wanted to know why... He performed tests to better comprehend synaptic plasticity in the auditory nerve, which is vital in understanding the beneficial effects of cochlear implants in congenitally deaf children. Dr Ryugo seeks to identify the latest stage at which implants could be placed in deaf children, so that they could still obtain some benefit. (If cochlear implants are inserted too late- if parents are hesitant, in other words- these instruments may not work at all to improve hearing.)
Previously, the clinical consensus as to why cochlear implants worked for some patients but not others was that language development prior to deafness lead to the best outcomes. Among congenitally deaf children, the younger the age of implant activation, the better the aural language results. These clinical experiences imply that uncorrected congenital deafness introduces irreversible abnormalities in the developing central nervous system. In mammalian models of congenital deafness, the synaptic structure of auditory nerve endings is abnormal. Ryugo wondered if the status of auditory nerve synapses represented an important link to the success or failure of cochlear implants.
He studied defects in the auditory nerve... specifically, he studied myelinated auditory never fibers called the endbulbs of Held. They transmit signals from the auditory nerve fiber to the postsynaptic cell with a high degree of fidelity. Congenitally deaf animals exhibit endbulbs with marked reduction in branching. Moreover, they contain fewer synaptic vesicles. These structural abnormalities have been associated with transmission irregularities at the synapse of endbulbs that may underlie loss of temporal resolution in the midbrain in neonatally deafened cats.
Ryugo stimulated deaf cats via a 6-channel cochlear implant and found that their endbulb synapses resembled those from normal hearing cats, after 3 to 6 months. I'm just brushing over the results here- until I write my article- but Ryugo hypothesizes that the changes observed after cochlear implantation at this crucial synapse enable the development of integrative and cognitive brain functions reflected in aural and oral communication in deaf children...
Beyond this angle, Dr. Ryugo is also interested in studying how chemicals could be imbedded in cochlear implants, to improve hearing. A pharmacological approach to improving deafness.
Side-note: Dr. Ryugo is one of the most enthusiastic people I've ever met. If you find yourself in Baltimore, look him (and his cats) up. A true delight.
-MGW-
posted by Meagan G at
1:56 PM
<< Home