May 24, 2006 — Human ears can wiggle and make noise, and now researchers have a better understanding of how these unusual processes work.
Since ear wiggling involves complex coordination of facial muscles, the research could shed light on related disorders, such as Bell’s palsy, which can cause facial paralysis.
The ear sounds research, meanwhile, is surprisingly illuminating when it comes to gender and sexuality issues.
This is because heterosexual men and women and homosexual women appear to produce different levels of ear noise.
While most human ears produce sound, controlled, detectable ear wiggling is not as common.
"The mechanism behind ear movements is sophisticated," said Bastiaan ter Meulen, who led the ear wiggling study.
Ter Meulen, a researcher at Erasmus MC, a university medical center in Rotterdam, the Netherlands, added that, unlike other facial muscles, ear muscles have their own accessory nucleus -- a control area for muscle function -- in the brainstem.
"Compared to animals, especially bats and cats, this nucleus is rather small in humans," he said.
He explained to Discovery News that a muscle involved in eye movement also directly controls ear motion. That's why when we look left or right, our ears slightly withdraw on both sides.
Breathing and swallowing are also linked to ear movement through muscles and neuronal pathways.
Ter Meulen and his team made these determinations after conducting an EEG, or brain wave test, on a 43-year-old woman who lost consciousness and experienced rhythmic bursts of ear movement.
Their study, which has been accepted for publication in the journal Clinical Neurophysiology, marks the first time such ear muscle activity has ever been documented in an EEG.
Another team of researchers analyzed noises made by the inner ear that are like echoes that occur in response to clicks, such as pencil tapping, or distortion, such as a bad radio signal.
Dennis McFadden, a professor of psychology at the University of Texas, Austin, and his colleagues measured the strength of these otoacoustic emissions, or ear-produced sounds, in rhesus monkeys and spotted hyenas. The studies have both been accepted for publication in the journal Hormones and Behavior.
The scientists found that, as for humans, the sounds were stronger in females. During the fall breeding season, the differences between the male and female ear sounds became even more pronounced, suggesting that hormones affect the emissions.
Because male and female spotted hyenas are more androgynous when young, the researchers expected that their otoacoustic emissions would be similar. As predicted, measurements of the echo-like ear sounds obtained from nine male and seven female hyenas were similar.
In a prior study, McFadden found that the sounds produced in the inner ears of homosexual and bisexual women were weaker than those emitted from the ears of heterosexual women.
Since men also exhibit weaker echo-like sounds in the inner ear, MdFadden said the results suggest the inner ear and some unknown brain structures may play a role in sexual preference.
"The inner ear may be a valuable non-invasive window into events that occur during brain development and sexual differentiation," he said.
