We all know what it feels like when our mind wanders.

In fact, it's a common experience for many of us.

As William James, the father of modern psychology, put it, our minds are like birds, constantly moving between flying and perching!

This fleeting nature of our thoughts can lead us to struggle with focus, especially when we're not deeply motivated. It's not uncommon to find ourselves thinking about unrelated things – the past, future, tasks yet to be done, or even forgotten ones. This phenomenon, known as “mind wandering,” can often make us lose track of the present moment.

But what happens when we take this a step further? What if our mind blanks completely, leaving us feeling like we're not sure where we were or what we were doing? This experience is known as "mind blanking," and it happens more often than we realize, especially when we're tired or under stress.

If we find ourselves blanking out during important moments, like while driving, taking an exam, or presenting at work, the consequences can be significant. What's more, sleep deprivation often makes this phenomenon worse.

In a fascinating study published in Nature Communications, we explored what happens in our brains during moments of mind wandering and mind blanking. By studying brain activity while healthy young individuals performed a monotonous task, we were able to track their attention and their performance.

Randomly, we would interrupt them to ask whether they were focused on the task, mind wandering, or mind blanking. Alongside this, we used an electroencephalogram (EEG) to monitor their brain rhythms.

What we discovered was intriguing. When people are tired, sleep-like slow waves – a pattern of brain activity associated with sleep – can be detected in certain parts of their brain even while they're awake. This phenomenon, known as "local sleep," can be seen as a brief episode of sleep during wakefulness, which interferes with our focus and cognitive abilities. It turns out that these sleep-like waves are not an all-or-nothing event but can manifest in specific areas of the brain.

We found that the occurrence of these slow waves could predict when mind wandering or mind blanking occurred. Slow waves in the frontal regions of the brain, responsible for controlling actions and thoughts, were linked to impulsivity and mind wandering.

On the other hand, slow waves in the posterior brain regions, which handle sensory processing, were tied to sluggishness and mind blanking. This finding suggests that local sleep, when it occurs in certain areas of the brain, can have different cognitive effects depending on the region it impacts.

This discovery can help us understand why we lose focus and experience attentional lapses throughout our day. Even when we're not sleep-deprived or suffering from any disorders, parts of our brain can "go offline" without us realizing it. This can happen during dull, repetitive tasks, which is exactly what we tested during this study. It's a normal phenomenon – the brain is constantly trying to balance wakefulness and sleep.

This study sheds new light on how sleep and wakefulness coexist in the brain, offering a new perspective on the everyday lapses in attention that we all experience. We may not always be aware of it, but our brains are constantly switching between states of wakefulness and sleep, which can significantly affect our concentration and awareness!