Presbycusis

Our ears are constantly listening. They are able to receive sound waves and convert them into a way our brain can interpret it. When air molecules vibrate and move in a pattern, we call those patterns sound waves. Sound is a form of energy and it has the ability to vibrate slowly or quickly. When sound vibrates slowly, it creates deep sounds; when sound vibrates quickly, it creates high-pitched sounds (Garrett, 2011). Sound enters the ear by way of the pinna through the external auditory canal where it reaches the middle ear. The tympanic membrane begins to vibrate and activates the ossicular chain (Garrett, 2011). The ossicular chain is made up of three small bones, the malleus, incus, and the stapes. The stapes pushes the oval window in and out. These sound vibrations move from the ossicular chain to the inner ear where the cochlea resides (Garrett, 2011).

The cochlea resembles a snail-shell, which is also where it gets its name in Latin, and is filled with fluid (Garrett, 2011). The rocking back and forth of the stapes against the oval window sends pressure waves through the fluid of the cochlea, and activates the organ of Corti (Garrett, 2011). The entire length of the cochlea is lined with sensory cells known as hair cells. When the basilar membrane vibrates, the fluid in the cochlea bends the hair cells (Garrett, 2011). The hair cells at the base of the cochlea near the oval window are responsible for higher frequencies, whereas the cochlear apex hair cells are responsible for lower frequencies (Garrett, 2011). This bending of the hair cells allows for the opening of potassium and calcium channels that depolarize the hair cell membrane (Garrett, 2011). The electrical impulses that are produced are passed along the hearing sensory nerve to the auditory cortex part of the brain (Garrett, 2011). This allows the brain to distinguish between music and speech.

Presbycusis is the deterioration of hearing ability that occurs with age. Presbycusis comes from the Greek words “presbys” meaning “elder” and “akousis” meaning “hearing” (Gates & Mills, 2005). It can range from mild to significant, and if left untreated, it can lead to isolation and depression (Gates & Mills, 2005). Hearing loss can be caused by exposure to loud noises over time or even inherited diseases (Cruickshanks et al., 2010). Other causes such as objects blocking the external auditory canal, such as earwax, have also been known to cause hearing loss (Gates & Mills, 2005).

There are two main categories of presbycusis. The first is conductive, which is loss due to disorders of the pinna and middle ear, and the second is sensorineural, which is hearing loss due to the inability to transduce information to usable neural signals. The pinna’s role is to help funnel sound to the external auditory canal. In the even that it is removed or damaged, a person’s hearing loses that funneling ability (Gratton, Bateman, Cannuscio, & Saunders, 2008). In the event that the external auditory canal is blocked, the tympanic membrane cannot receive sound waves properly. Hearing loss may also occur in the case of otosclerosis or damage to the tympanic membrane (Gates & Mills, 2005).

Cochlea hair cells and spiral ganglion cells in the vestibulocochlear nerve can be affected in sensorineural loss (Bao & Ohlemiller, 2010; H. S. Lee, Lee, Kang, Lee, & Lee, 2014). This happens when to the cochlear hairs or nerve pathways to the brain are damaged and this is the most common form of hearing loss. Due to heredity and ageing, the hairs and nerve endings become less functional and less mobile (Huang & Tang, 2010). Sadly, this type of damage cannot be reversed. Partaking in jobs in which there is a lot of loud noises such as construction, certain medications, and even diseases such as meningitis can lead to this type of hearing loss (Cruickshanks et al., 2010).

A person with presbycusis can lead to misunderstanding in the context of conversations (Gates & Mills, 2005). A person may hear math and they may mistake if for map or mash (Gates & Mills, 2005). This leads to communication errors. The loss of the lower frequencies, which are received by the base of the cochlea, results in reduced speech detection. Going to concerts or even the movies will become less enjoyable as the inability to hear high pitch sounds or even the ability to pick out background noise takes hold. Working in fields, such as music, may lead to multiple errors. For a person who works as a conductor, his job is dependent on the ability to hear all of the sounds that’s coming from the members of the orchestra. If he is unable to hear those sounds, he is unable to effectively do his job.

References

Bao, J., & Ohlemiller, K. K. (2010). Age-related loss of spiral ganglion neurons. Hearing Research, 264(1-2), 93–97. doi:10.1016/j.heares.2009.10.009 ↩
Cruickshanks, K. J., Nondahl, D. M., Tweed, T. S., Wiley, T. L., Klein, B. E. K., Klein, R., et al. (2010). Education, occupation, noise exposure history and the 10-yr cumulative incidence of hearing impairment in older adults. Hearing Research, 264(1-2), 3–9. doi:10.1016/j.heares.2009.10.008 ↩1 ↩2
Garrett, B. (2011). Brain and Behavior: An Introduction to Biological Psychology (3rd ed.). Los Angeles, CA: Sage. ↩1 ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9
Gates, G. A., & Mills, J. H. (2005). Presbycusis. The Lancet, 366(9491), 1111–1120. doi:10.1016/S0140-6736(0567423-5 ↩1 ↩2 ↩3 ↩4 ↩5 ↩6
Gratton, M. A., Bateman, K., Cannuscio, J. F., & Saunders, J. C. (2008). Outer- and middle-ear contributions to presbycusis in the Brown Norway rat. Audiology & Neuro-Otology, 13(1), 37–52. doi:10.1159/000107551 ↩
Huang, Q., & Tang, J. (2010). Age-related hearing loss or presbycusis. European Archives of Oto-Rhino-Laryngology : Official Journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : Affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery, 267(8), 1179–1191. doi:10.1007/s00405-010-1270-7 ↩
Lee, H. S., Lee, Y. J., Kang, B. S., Lee, B. D., & Lee, J. S. (2014). A clinical analysis of sudden sensorineural hearing loss cases. Korean Journal of Audiology, 18(2), 69–75. doi:10.7874/kja.2014.18.2.69