Brain 'Noise' Increases With Age


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.