[Paleopsych] MSNBC: How the brain tunes out background noise
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Fri Dec 30 19:31:01 UTC 2005
How the brain tunes out background noise
'Detector neurons' focus exclusively on novel sounds, scientists
Special neurons in the brain stem of rats focus exclusively on
novel sounds and help them ignore predictable and ongoing noises, a
new study finds.
The same process likely occurs in humans and may affect our speech,
and even help us laugh.
The "novelty detector neurons," as researchers call them, quickly
stop firing if a sound or a pattern of sounds is repeated. They
will briefly resume firing if some aspect of the sound changes. The
neurons can detect changes in pitch, loudness or duration of a
single sound and can also note shifts in the pattern of a complex
series of sounds.
"It is probably a good thing to have this ability, because it
allows us to tune out background noises like the humming of a car's
motor while we are driving or the regular tick-tock of a clock,"
said study team member Ellen Covey, a psychology professor at the
University of Washington. "But at the same time, these neurons
would instantly draw a person's attention if their car's motor
suddenly made a strange noise or if their cell phone rang."
Covey said similar neurons seem to be present in all vertebrates
and almost certainly exist in the human brain.
The novelty detector neurons seem to act as gatekeepers, Covey and
her colleagues conclude, preventing information about unimportant
sounds from reaching the brain's cortex, where higher processing
occurs. This allows people to ignore sounds that don't require
The results are detailed this month in the European Journal of
The novelty detector neurons seem able to store information about a
pattern of sound, so they may also be involved in speech, which
requires anticipating the end of a word and knowing where the next
"Speech fluency requires a predictive strategy," Covey explained.
"Whatever we have just heard allows us to anticipate what will come
next, and violations of our predictions are often surprising or
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