You may go to sleep and "lose consciousness", but that doesn't mean your brain takes a break. But what does the brain do and what doesn't it do during deep sleep? What's the difference between consciousness and the lack of it?


When we're awake, different parts of the brain use chemicals and nerve cells to communicate constantly across the entire neuronal network. However, in the deepest part of sleep "the brain breaks down into little islands that can't talk to one another," said study leader Giulio Tononi of the University of Wisconsin-Madison.

Tononi's team attached electrodes to the participants' heads, and then activated various parts of the brain using non-invasive methods. The electrodes were used to monitor how various stimulations of the brain triggered reactions elsewhere in the brain.

Researchers found that the dreaming state was somewhat similar to the state of being awake. However, during the deep dream-less sleep, the brain activity and reactions looked very different: "During deep sleep early in the night, the response is short-lived and doesn't propagate at all," Tononi said.

These findings suggest that consciousness depends on the brain's ability to integrate information. Tononi's colleague, Marcello Massimini said that the compartmentalization of the brain makes possible sleep and resting. "This process would allow cortical circuits to eliminate noisy synapses and renormalize in order to be ready for the next day," said Massimini. Moreover, according to researchers, this is why performance in various tasks improves after sleep.