According to a new study, your brain is charged with detecting sound functions even when you are sound asleep.
The findings of the study by UCLA and Tel Aviv University scientists were published in the journal Nature Neuroscience. A one-of-a-kind investigation of brain activity in the cerebral cortex of epilepsy patients discovered a strong reaction to sound during sleep that closely resembled the brain’s response during alertness. However, there was one significant variation between sleep and awake, and that was the level of alpha-beta waves.
The attenuation of these waves marks the awake state and indicates neural input from higher brain areas that aids in understanding sound and anticipating what is to come. This was the main reason for the lack of sleep.
“The neuronal orchestra is never shut from the environment when the person is deep asleep,” said Dr. Itzhak Fried, a study co-author and director of UCLA’s Epilepsy Surgery Program. “The neurons are like musicians playing Mozart, each one with great fidelity and volume. Only the conductor, the one who monitors performance and leads expectations, is missing.”
Fried, who has extensively researched the brain’s activity during waking and sleep in earlier study, said the results might help us understand how much information is processed by those in unaware conditions, such as comatose patients or those under anaesthesia. They may also suggest to strategies to improve memory during sleep, when the brain consolidates recent knowledge, maybe through audio stimulation.
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Study on brain cells
Researchers took an exceptionally detailed look at the activity of single brain cells in individuals with severe epilepsy using electrodes placed in their brains to pinpoint seizure sites for possibly curative surgery.
Patients who volunteered to participate in the study at UCLA and Tel Aviv Sourasky Medical Center were given bedside speakers that played words and music when they were awake and listening as well as sound asleep. Mozart’s “Eine kleine Nachtmusik,” or “A Little Night Music,” was a fitting musical option for the study.
Over the course of seven years, the researchers collected data from over 700 neurons throughout awake and various stages of sleep, allowing them to compare neural activity and brain waves. During sleep, primary auditory cortex brain cells reacted most strongly, but there was a decrease in “top-down” neural input from higher brain areas that govern attention and expectancy.
“That’s probably why we are still not conscious, although we are still processing the sensory information from the external world. So you’re not completely shut from the environment in that sense,” Fried said.
