Why It's Impossible To Focus When You Haven't Slept

We all know how difficult it is to pay attention at work -- or to get anything done, for that matter -- after a night of bad sleep. 

It should come as little surprise, then, that sleep and attention are critically linked. Now, a new study from neuroscientists at the Queensland Brain Institute in Australia  reveals why the ability to pay attention during the day relies on our capacity to do the opposite at night. 

The researchers explain that sleep and attention are "like yin and yang" -- opposing forces that work together to create harmony -- and the two systems may have even co-evolved to regulate each other. 

"The yin and yang in Chinese philosophy describe contrary forces that are in fact interdependent and give rise to each other, as with light and dark," Leonie Kirszenblat, a neuroscience researcher at the University of Queensland and the study's lead author, told The Huffington Post. "Sleep and attention seem like opposite brain states, but they may actually arise from similar brain mechanisms that relate to ignoring the outside world."

Sleep and attention may balance each other, because the ability to pay attention depends on getting adequate sleep and the amount of sleep we need seems to be driven by learning and performing tasks that require attention.

The researchers analyzed a variety of sleep studies conducted on animals, investigating the function of sleep in different types of species. The data revealed that in animals with simple nervous systems, such as nematodes, sleep is used for development or as a response to environmental stress. 

It turned out that in animals with complex nervous systems -- including insects, humans and other mammals -- sleep isn't only used for growing or responding to stress. Instead, the data showed that sleep is an everyday activity that's used to support cognitive functions, including selective attention. 

The data also suggested that tasks requiring more attention correlated with an increased need for sleep, and a great intensity of sleep. 

Sleep and attention tend to be viewed as fundamentally different states, but they seem to involve a common mechanism for suppressing external distractions.

"Sleep and attention may be two sides of the same coin," Kirszenblat said. "Both allow animals to selectively process some information, while ignoring most other sensory stimuli. More broadly, we tend to view sleep and wake as fundamentally different phenomena, but mechanistically they might be quite similar because both involve suppressing the outside world."

Dr. Bruno van Swinderen, a neuroscientist at the university, said in a statement that this is a "revolutionary" way of thinking about how the brain works during sleep and waking.

The study was published in December in the journal Trends in Neurosciences .

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