Mind blanking: Study shows how the brain ‘sleeps’ when it goes blank

The mind is not supposed to stop working, even unconsciously. It is not easy to leave it empty. However, there are times when it suddenly goes blank; when there is no way to recover the thread of what we were saying; when whatever was previously in our head cannot be recovered even as a vague thought or idea. Now, several researchers have put together everything that is known about this phenomenon and argue that, in these cases, there is a specific and distinct pattern of brain activity that resembles what happens when we sleep. According to these experts, these mental lapses have to do with changes in the excitability of various areas of the brain and are inevitable.

In a scientific article published in the journal Trends in Cognitive Sciences, the authors begin by highlighting how much is unknown about mind blanking. It is not only that we don’t have a definition for this phenomenon, we don’t know what causes it, or whether it reflects a temporary absence of consciousness due to lapses of attention or if it is the result of problems with memory, language or accessing content. Moreover, it is a multifaceted phenomenon; mind blanking can happen while talking, but also when thinking in silence, when listening to music and even when dreaming, producing what are called dreams without content.

“That’s why it’s such a fascinating topic,” says Athena Demertzi, director of the Laboratory of the Physiology of Knowledge at the University of Liège in Belgium and co-author of this paper. “In our review, we tried to connect typical cases of blank mind — the small gaps that can occur in our daily lives — with other types of content-free experiences that occur during sleep [e.g., white dreams] or meditative practices,” she adds.

Using this approach, she and her team sought to identify potentially related phenomena. “We argue that this family of ‘blank minds’ could perhaps share some mechanisms, and that one type may shed light on the others,” she says.

The researchers used two different imaging techniques that record brain activity — functional magnetic resonance imaging and electroencephalograms — on people who were asked to blank their minds. While acknowledging that a spontaneous mental blank is not the same as an induced blank, they found that specific patterns appeared that were distinct from other mental states. There is a kind of deactivation of a complex circuit that connects different areas of the brain.

“We believe that spontaneous mind blanks, even induced mind blanks, can occur due to a local sleep intrusion phenomenon,” Demertzi explains. “When the mind suddenly goes blank, it may be due to fatigue and part of the brain feeling drowsy. While you’re still awake, it’s possible that part of your brain network is working less efficiently,” she says. Reinforcing this idea, they saw sleep-like rhythms (so-called slow waves) appearing in electroencephalograms that could disrupt normal information processing.

“From a network perspective, this is associated with excess connectivity, which could also disrupt cognitive processes. The mind could experience a kind of wavering, causing a brief vacuum,” she concludes.

What the authors of this work have observed over the years is that these mental gaps tend to appear during the development of demanding mental tasks, in which several areas of the brain with all their interconnections are at play. But they can also emerge during high levels of activation, for example, immediately after intense physical exercise.

Regarding how often they occur, there is no real-life data, but during laboratory tests, these lapses appeared more than 10% of the time during which some cognitive function was performed. Although everyone experiences these lapses, minors and those with attention deficit hyperactivity disorder (ADHD) are likely to experience them more frequently.

Thomas Andrillon from the Paris Brain Institute and co-author of the paper, points out that blank mind moments increase with sleep pressure and sleep deprivation. “Given that 50% of adults and children with ADHD have sleep disorders, which often lead to excessive daytime sleepiness, we believe that the increase in the blanks for those with ADHD could be a direct consequence of a decrease in daytime wakefulness due to sleep problems,” he explains.

From the Institute for Advanced Studies in the Humanities at Edinburgh University in Scotland, Adriana Alcaraz says that there are several theories about this mental vacuum. “One is that the brain is in a state of ‘rest,’ or as it is referred to in neuroscience, in a default state.”

This default state corresponds to the state in which the brain finds itself when we are not doing anything, and is usually associated with moments of digression. “Other theories suggest that the type of brain state that occurs during mind blanking is similar to what happens during states of meditation, or even when we are falling asleep,” says Alcaraz, whose field of study is precisely sleep and dreams.

What happens, in this scenario, is that the brain enters a state of low connectivity. But there is a third group of more recent theories that suggest that “when the mind is blank, our brain is in a basic state of alertness. The brain is activated, but it is not processing anything,” adds Alcaraz.

Alcaraz stresses that studying the state of mental blankness helps us explore what happens in the brain when we’re not thinking or perceiving anything: “It allows us to better understand the brain in its most basic state,” she says. Due to its similarity to other brain states, such as meditation or sleep, it allows us “to gain a deeper understanding of other types of experiences that are more difficult to study experimentally.”

Alcaraz suggests another good reason for studying these mental lapses: “In a world in which our minds are constantly busy — working and looking at our phones — investigating what happens when we do none of these things not only allows us to learn more about one facet of our mind, but also flags up the need to pay more attention to these types of states and their possible benefits.”

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