Your mind is usually busy – replaying conversations, planning dinner, worrying about tomorrow, talking about the present. But from time to time this activity seems to stop. There is no thought to follow and no image to cling to. For a brief moment, awareness itself seems empty.
Such moments are often perceived as lapses in attention or memory. The new findings suggest that they instead reflect brief interruptions in conscious experience itself—transient states that occur during wakefulness and are characterized by measurable changes in brain activity. Work published in Proceedings of the National Academy of Sciencessuggests that consciousness does not always coincide precisely with wakefulness and that these interruptions may be a common feature of everyday awareness.
“Mind blackout is probably an extremely common phenomenon during which certain areas of the brain briefly enter a sleep-like state. We estimate that this occurs between 5 and 20 [percent] hours of wakefulness, although there is significant variation between people,” the study authors said in press release.
The Elusive Nature of Mind Shutdowns
Despite growing interest, researchers have not yet fully reached a consensus on what qualifies as intelligence extinguishing. At its core, the term refers to episodes in which people report an inability to describe any mental content at all—not because it is fleeting or difficult to articulate, but because it seems to be absent altogether.
“Mental blackout is defined as the complete absence of mental content that can be described to others. No mental images, no catchy tune running through the head, no intrusive thoughts.” […] Nothing! This experience is often sought after by practitioners of meditation or mindfulness. But it’s not limited to them: it seems to be very common after intense and prolonged cognitive effort, such as a university exam, or in cases of sleep deprivation,” said Esteban Muñoz-Musat, a neurologist and co-author of the study.
Beyond everyday life fatiguemind shutdown is also observed in clinical settings. Previous studies have linked it to conditions such as generalized anxiety disorder, and it has been more commonly reported in people with attention deficit hyperactivity disorder (ADHD).
Read more: ADHD is difficult to diagnose, but proper treatment is critical
Tracking brain fog with brain recordings
To capture this fading of consciousness, the researchers designed an experiment that required prolonged attention. They recorded brain activity using high-density electroencephalography (hdEEG) in 62 healthy volunteers performing long-term, repetitive tasks. Participants were also periodically asked to report what was going on in their minds immediately before each prompt.
When participants said their mind was empty, their brains behaved differently than when they were focused on a task or lost in unrelated thoughts. Large-scale connectivity in the brain has weakened, suggesting that distant regions are no longer working in sync. At the same time, the brain's processing of incoming visual information changed.
In particular, neural activity associated with later stages of visual processing—often associated with conscious perception—was reduced or absent altogether. During these moments, there were also subtle changes in behavior: participants responded more slowly, made more mistakes, and appeared less attentive.
“These observations indicate that during the blackout episode, participants had limited access to sensory information from the environment,” said Thomas Andrillon, senior author of the study. “These new findings support a new idea: being awake does not necessarily mean being aware of something. Shutting down the mind corresponds to an actual interruption in the flow of thoughts.”
A mosaic view of conscious experience
Future research will explore whether “switching off the mind” can help refine understanding of certain neurological or psychiatric conditions, as well as shed new light on how attention and awareness fluctuate in the brain.
“Our results suggest that the structure of conscious experience is more like a mosaic of discrete states than a continuous mental movie. A mosaic in which the absence of certain tiles results in brief moments of unconsciousness while the subject is awake,” said Lionel Naccache, a neuroscientist and co-author of the study.
Read more: Your brain has five ages – and they shape your thinking for life.
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