The Sounds of Silence: Brains are Active in Absence of Sound
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THE SOUNDS OF SILENCE: BRAINS ARE ACTIVE IN ABSENCE OF SOUND
WASHINGTON, DC, January 4, 2006 – Listen up! Our brains can actually listen to silence, suggests new research appearing in the January 4th issue of The Journal of Neuroscience.
Some of the same brain areas that are active while listening to actual sounds also are active while attentively listening to silence, find Pierre Fonlupt, PhD, Julien Voisin, PhD, and their team of researchers at INSERM, France’s national research institute. “This is the first study in humans to show that the auditory cortex is activated when a subject is attending to and listening to silence, when expecting an upcoming sound,” says Fonlupt.
“This finding tells us something about the mechanisms in the brain that are important for attention—when you expect an event to occur, your brain is highly sensitized to that possibility,” says Robert Zatorre, PhD, of the Montreal Neurological Institute in Canada.
Results parallel previous studies in vision that found that the brain’s visual areas were activated before subjects could see a stimulus, but were expecting to see that stimulus at a specific location. “Taken together,” says Fonlupt, “these studies provide some evidence that all of the brain’s sensory areas prepare the brain to process actual stimuli.”
Fonlupt and his colleagues observed the brains of 11 subjects using functional magnetic resonance imaging—a brain scanning procedure—while the subjects were at rest, listening to silence, and listening to an actual sound. For the listening to silence trial, subjects were told that they would eventually hear a sound in the right (or left) ear, indicated by a right (or left) glowing arrow.
While subjects were listening to silence, brain networks in the auditory cortex were activated on the side of the brain opposite to where the sound was going to come from, scientists found. The auditory cortex also is activated when listening to actual sounds. Two areas in the front of the brain associated with auditory attention also were activated, regardless of which side the sound was going to be coming from. These activations differed from the resting trial and from networks related to general attention and motor preparation.
“These findings may spark further research aimed at uncovering more selective pre-activations of auditory and other sensory areas,” suggests Fonlupt.
The Society for Neuroscience is an organization of more than 37,500 basic scientists and clinicians who study the brain and nervous system. Pierre Fonlupt, PhD, is a member of the Society. He can be contacted via e-mail at: email@example.com.