The links between tectorial membrane development, hearing loss and early vocabulary composition in children

            Hearing loss over the years has seen a lot of development in terms of understanding it better. What caused it? How do we prevent it? Are there many types of hearing loss? How can it be fixed? A lot of these questions that were formerly impossible to answer with detail and solid proof, have been answered by modern neuroscience and have raised more detailed and specific questions in the field, as is the way of science. Hearing loss in early development is consequently connected to speech impediments in children before they can get cochlear implants. There has been a recent study conducted at the University of Miami however, that shows that one specific type of vocabulary, when present in large proportions in a child’s language, leads to better language development as much as 3 years later in life. To understand the mechanism by which hearing loss can be caused, as well as a possible solution to the issue, let’s take a look at the following experiment.

            The study: Critical role of hepsin/TMPRSS1 in hearing and tectorial membrane morphogenesis: insights from transgenic mouse models, conducted by Dr. Yu and his fellow researchers, shows that hepsin knockout (KO) mice had profound hearing loss. The focus of the study was hepsin, which is a transmembrane serine protease. It is heavily expressed in the liver and also responsible for the development of the tectorial membrane (TM) due to acting as a co-expressor with important cochlear development proteins. This study Is relevant in the discussion of the U-Miami study article as it highlights a possible cause for hearing loss as well as possible restoration of hearing. These mice were found to have abnormal TM development morphologically, where their TM was detached and more spaced apart than normal. This was how the hearing loss in the mice was able to be attributed to the serine protease of focus and not the outer hair cells being dysfunctional. This was done using electron microscopy on the mice with and without the protease, and the next portion brought the experiment together as it showed that the introduction of human hepsin into these mice could restore tectorin protein levels (which are involved in TM development and co-expressed with hepsin).

            This leads to the connection here between the mechanism of hearing loss, and the important of “shape-based vocabulary,” for children with hearing loss. The paper Vocabulary Composition Shapes Language Development in Children With Cochlear Implants, shows findings regarding the language development of children pre and post cochlear implants. This study and the data used in it are a part of the Childhood Development after Cochlear Implantation Study which is a national, multi-site longitudinal study. The researchers analyzed data on the language abilities of young children with cochlear implants prior to their implantation surgery and once every 6 months after. The control group was children with normal hearing who were also a part of the study and were assessed in the same fashion. The results shows that children that had a larger proportion of “shape-based nouns” in their vocabularies (which are a category of nouns associated with objects’ shapes like “chair” or “cup.”) shortly after implantation, led to larger overall vocabularies a year, two years and even three years afterwards. They were more also more likely to have caught up with their peers with normal hearing which is a large indicator of the importance of certain words in language development.

            Hearing is a very important sense, even in the modern day and age where we no longer hunt our prey and hide from our predators. In an increasingly advancing world, the ability of neuroscientific development in providing people with an opportunity to regain a lost sense, is nothing short of miraculous. The age of equity is dawning and these studies are a large part of the reason why these kids will have a level playing ground like everybody deserves.

 

References

Yang, T. H., Hsu, Y. C., Yeh, P., Hung, C. J., Tsai, Y. F., Fang, M. C., Yen, A. C. C., Chen, L. F., Pan, J. Y., Wu, C. C., Liu, T. C., Chung, F. L., Yu, W. M., & Lin, S. W. (2024). Critical role of hepsin/TMPRSS1 in hearing and tectorial membrane morphogenesis: Insights from transgenic mouse models. Hearing research, 453, 109134. https://doi.org/10.1016/j.heares.2024.109134

University of Miami. (2024, November 14). New study sheds light on language development in children with hearing loss. ScienceDaily. Retrieved December 11, 2024 from www.sciencedaily.com/releases/2024/11/241114161248.htm