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'Speak in my right ear and sing in my left'

"Asymmetric Cochlear Processing Mimics Hemispheric Specialization"
Described in Science, Vol 305, Issue 5690, 1581 , 10 September 2004
by Y. S. Sininger and B. Cone-Wesson:


This finding is similar to those of enhanced processing of tones in
right auditory cortical areas and of rapidly changing stimuli on the
left, (given strong crossed connections from ear to brain)...
Behaviorally, reaction time is faster and stimulus identification is
more accurate when a subject's right ear is presented with speech-type
stimuli or when the left ear is presented with tonal information ...
 >These findings indicate that processing at the level of the ear
may facilitate lateralization of auditory function in the brain...
"We always assumed that our left and right ears worked exactly the same
"We were intrigued to discover that clicks triggered more amplification
in the baby's right ear..."

Authorial interviews from South African Independent Media Online
described as
  'Speak in my right ear and sing in my left'; Full text follows.


<Washington - The right and left human ears process sound differently,
according to scientists who studied the hearing of babies and found the
right ear better at picking up speech-like sounds and the left more
attuned to music.

It has long been known that the right and left halves of the brain
process sound differently, but those differences were thought to stem
from cellular properties unique to each brain hemisphere.

The new research suggests that the differences start at the ear.

"We always assumed that our left and right ears worked exactly the same
way," said lead researcher Yvonne Sininger of the University of
California at Los Angeles. "As a result, we tended to think it didn't
matter which ear was impaired in a person. Now we see that it may have
profound implications for the individual's speech and language

The discovery, described in the current issue of Science Magazine, will
help doctors enhance speech and language development in
hearing-impaired newborns and the rehabilitation of persons with
hearing loss.

Sininger and her colleagues studied hearing in more than 3 000
newborns, specifically tiny amplifiers located in the outer hair cells
of the inner ear.

These cells contract and expand to amplify sound vibrations, convert
the vibrations to neural cells and send them to the brain.

The scientists inserted tiny probes into the babies' ears that emitted
two different types of sounds and measured the amplified vibrations.
They found that speech-like clicks triggered greater amplification in
the right ear, while music-like sustained tones were more greatly
amplified by the left ear.

"We were intrigued to discover that the clicks triggered more
amplification in the baby's right ear, while the tones induced more
amplification in the baby's left ear," Sininger said. "This parallels
how the brain processes speech and music, except the sides are reversed
due to the brain's cross connections."

"Our findings demonstrate that auditory processing starts in the ear
before it is ever seen in the brain," said co-author Barbara
Cone-Wesson of the University of Arizona. "Even at birth, the ear is
structured to distinguish between different types of sound and to send
it to the right place in the brain." - Sapa-AFP >



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