Hearing research can be studied in the context of the following:

Speed of hearing – humans can listen to sounds at about 20,000 times per second (the visual system processes images below 20-30 times per second; images presented above 20-30/s is seen as a continuum, e.g., movies, TV). Thus, the auditory system process information faster than any other sensory system, such as vision.

Atomic sensitivity – tiny movements the size of an atom can be detected by the hearing organ

The broad range of sensitivity – thresholds in humans range from 0 dB to 120 dB, which represents about one trillion-fold difference in energy.

Hearing loss in the general population is about 10-15%. Most of the time, it is caused by genetic disorders. However, other causes include infections, drugs, loud noise, and aging. Genetic disorders represent about 50% of the causes of hearing loss, which might consist of SRS.

Using sonogram, Dr. Yamoah reads a poem to illustrate how vowels and consonants are represented in the form of high and low frequencies, respectively. These frequencies are broken down by the auditory nerve and sent to the brain. The ability to hear higher frequencies are lost as we age. He also compared the difference between listening to music in a quiet vs. in a crowded (noisy) environment. The noisy background reduces the ability to hear the music. As we age, it becomes difficult to hear in noisy backgrounds or certain tones.

Hearing works by activating tiny bones in the inner ear. In the inner ear, there is a snail-shaped cavity called the cochlea, which contains fluid. This place massive force on tiny hair bundles that signal the auditory nerve into the brain. In the inner ear, ion channels and proteins work together to circulate potassium ions and, in doing so, generate a battery that serves as a powerhouse to increase the sensitivity of the ear. This process is done through specific potassium ion channels, which are regulated by polyamines.

Research question: Is the polyamine disruption in SRS mice sufficient to alter the function of the inner ear to cause hearing loss?

Research:

The research was done to compare hearing in 6-week old SRS mice to healthy mice. Results show that hearing is reduced starting at six weeks of age and continues to decline until 16 weeks of age, as shown in his graphs. This work shows there is a problem with the potassium channels. The problems are primarily seen in outer hair cells, but not in inner hair cells. There is also damage to part of the basal cochlear as a result of the activation of chemicals which cause cell death. This is called apoptosis. If hair cells can be replaced, perhaps the undisturbed nerves might be to continue to support the replaced hair cells.

Ongoing/future research:

Further, evaluate the cause of hearing loss and if these hearing changes might follow the progression of SRS. It is still too early to know, but further work will be done.