http://www.livescience.com/health/080707-brain-noise.html

Brain 'Noise' Increases With Age
By Andrea Thompson, Senior Writer
posted: 07 July 2008 03:25 pm ET

Like the wavy lines and snowy static that dance across old TV
screens, your brain generates noise.

Neuroscientists had thought that this brain noise, detectable by
researchers using high-tech gear, wasn't important to the goings-on
in your noggin. It was also suspected that this noise would decline
with age as children grew up and their mental processes became more
efficient.

But new research suggests that noise actually increases with age and
is a sign of greater complexity in the brain.

Researchers at the Baycrest Centre for Geriatric Care in Toronto had
a group of 79 people complete a series of face memory tasks,
measuring how well they were able to accurately recall faces. The
participants represented two age groups, children (ages 8 to 15) and
young adults (ages 20 to 33). While they were performing the task,
EEG (electroencephalography) recordings were taken to measure the
precise timing of brain activity.

The young adults scored better on the tasks than the children,
showing that their memory was better and their performance more
reliable. But they didn't have less noise than the children — in
fact, they had more.

"What we discovered is that brain maturation not only leads to more
stable and accurate behavior in the performance of a memory task, but
correlates with increased brain signal variability," said study
leader Randy McIntosh. "This doesn't mean the brain is working less
efficiently. It's showing greater functional variability, which is
indicative of enhanced neural complexity."

As McIntosh described it to LiveScience, "the brain's kind of
exploring what it can do" by trying out different possibilities.

The study, detailed in the July 4 issue of the online journal Public
Library of Science – Computational Biology, was funded by the James
S. McDonnell Foundation.

McIntosh and his colleagues are starting to look at the noise levels
in the brains of infants and the elderly, to see how they change with
age. There is some evidence, McIntosh says, that noise levels go down
with diseases such as Alzheimer's and go up with disorders such as
schizophrenia.

"There's a level at which [the noise] is optimal," McIntosh said. But
just what that level is, researchers don't yet know, he added.