"This is the first time anyone has been able to hormonally induce a change in hearing sensitivity in a vertebrate," said Joseph Sisneros, a UW assistant psychology professor who studies the neural basis of behavior. He is the lead author of a paper being published in the July 16 edition of the journal Science.
Sisneros and a Cornell research team headed by Andrew Bass, found that a spike in levels of the hormones testosterone and estradiol (an estrogen) triggers changes in the females' inner ear so they are capable of detecting higher frequencies in the males' multi-harmonic humming. This process couples the transmission of sound by the males and reception by the females.
"We suspected that enhancing the sensitivity of the females' ear to the upper harmonics of the males' hums should improve detection of their vocalization," said Bass, who is a professor of neurobiology and behavior. "Upper harmonics propagate farther in shallow-water environments like those where midshipman males build nests and sing their love songs to attract females. But the females can't process this vital information and respond appropriately if they can't hear it. Steroid hormones appear to provide a key molecule that leads to shifts in the hearing sensitivity of females."