What Happens When Your Mind Goes Blank? It Could Be Your Brain In “Local Sleep”

“We sought to better understand mind blanking by parsing through 80 relevant research articles – including some of our own in which we recorded participants’ brain activity when they were reporting that they were ‘thinking of nothing’,” said senior study author Athena Demertzi in a statement.

Demertzi and a team of colleagues based in France, Australia, and Belgium believed that a deeper investigation into mind blanking could help answer some intriguing questions about the nature of consciousness. Not everyone experiences mind blanking, so understanding it better could, in turn, help us learn more about subjective experience – a tricky concept that has been explained as the “’what it is like’ experience of internal neural processing that typically arises from a sensory stimulus.”

The researchers learned that on average, people’s minds are “blank” about 5-20 percent of the time. However, just as some people have no inner monologue or mind’s eye, each of us will experience mind blanking in a different way and to different degrees. For example, people with ADHD reported experiencing mind blanks more frequently than their neurotypical peers.

The data also showed that there was a clear difference in what people describe as their mind “blanking” versus their mind “wandering”.  

Mind blanking was most often reported after periods of sustained focus, like taking an exam, during sleep deprivation, or after intense physical exercise. While for many people it’s part and parcel of the normal functioning of the brain, it is also associated with a number of neurological and psychiatric conditions, including anxiety, traumatic brain injuries, and Kleine-Levin syndrome, which causes episodes in which people can sleep up to 20 hours per day.

As well as behavioral studies, research using brain imaging and other investigative techniques was analyzed. When someone’s mind is blank, they might not be having any specific thoughts in that moment, but that doesn’t mean the brain is idle.

In fact, evidence from electroencephalography (EEG) suggests that while the person remains awake during a mind blank, their brain might be going into what’s been called a “local sleep” state. The EEGs showed slow, sleep-like waves and reduced signal complexity, and this was coupled with a slower heart rate and decreased pupil size – all hallmarks of sleep.

The team also cited a 2019 study that used functional magnetic resonance imaging (fMRI). Subjects were asked to “think of nothing” during the scans – trust us, it’s harder than you’d expect! The results showed deactivation in several key brain regions: the inferior frontal gyrus, Broca’s area, supplementary motor cortex, and hippocampus.

However, because the people were deliberately trying to keep their minds empty in this study, Demertzi and the team explain that this could be different from a spontaneous mind blank – there are still a lot of unanswered questions.

“We realize that the investigation of [mind blanks] presents methodological and conceptual challenges,” the team writes.

On balance, they believe that mind blanking is more likely to occur when the brain is in either a high or low arousal state. Since mind blanking differs so much between people, it may be more useful to consider it as a group of experiences.

“The experience of a ‘blank mind’ is as intimate and direct as that of bearing thoughts,” commented co-author Jennifer Windt.

Mainly, the team aims to spark more of a conversation around this topic in the hopes that it will inspire future research.

“We believe that the investigation of mind blanking is insightful, important, and timely,” said first author Thomas Andrillon. “Collectively, we stress that ongoing experiences come in shades with varying degrees of awareness and richness of content.”

The study is published in the journal Trends in Cognitive Sciences.