Answers to a Long-waited Question Regarding our Hearing Ability
Professor Bok Jinwoong's Research Team
Sound frequency discrimination is crucial for daily activities such as verbal communication and social interactions throughout animal kingdom. This process begins at the auditory peripheral organ, the cochlea, which resides within the inner ear. In 1961, Professor Georg von Békésy was awarded the Nobel Prize in Physiology or Medicine for one of his findings that high-frequency sounds were perceived near the base of the cochlea and lower frequencies toward the apex. Since then, many graded anatomical and physiological features that facilitate frequency discrimination within the cochlea have been identified. However, the underlying molecular mechanism(s) for establishing this cochlea’s special organization, known as the tonotopy (from Greek, tono- = frequency and topos = place), remained largely elusive.
In a recent study published in PNAS, Professor Bok Jinwoong’s research team proposed that Sonic hedgehog (Shh), which is one of the key signaling molecules important for animal development and homeostasis, mediates specification of regional identity along the developing cochlea, and this regional identity prefigures the tonotopic organization of the mature cochlea. Prof. Bok’s research team also revealed that while the early role of Shh in specifying the regional cochlear identity is conserved in mammals and birds, downstream effectors that play roles in executing the Shh function in the tonotopic organization are diverged between the two species. Prof. Bok noted that this finding answers to a long-waited question of how the cochlea acquires its capability to discriminate different sound frequencies.