Scientists identify sleep-like slow waves as responsible for daydreaming and... sorry, what were we talking about again?

Localised brain sleeping behind wakeful forgetfulness and poor atten


Neuroscientists have developed a method for predicting when your mind might go blank or completely forget whatever it was we were talking about.

Slow waves, a pattern of neural activity commonly associated with the transition to sleep, could be a good prediction of that unedifying moment in a meeting when you've forgotten the name of the person you're talking to and indeed the subject about which you are supposed to be talking, while instead idly daydreaming of tonight's dinner.

Anyway, where were we?

Oh yes. According to neurologists, these lapses of attention can occur when we are awake. They are associated with mind wandering – or daydreaming – where the stream of consciousness halts and we experience the vertigo of brain freeze.

Such lapses occur more often when people are tired, and researchers argue they could be linked to a neural phenomenon called "local sleep", where certain brain regions show signs of being in slow-wave sleep while the rest of the brain is alert. Although the link has been made in sleep-deprived rodents and humans, it had not been demonstrated in well-rested humans.

That is until Thomas Andrillon, a research fellow at the Institut du Cerveau, or Paris Brain Institute, and his colleagues recorded whole brain electrical activity with electroencephalography in 26 well-rested adult humans.

Subjects were asked to perform tasks focusing on images of faces or numbers for an average of 1.7 hours. They were also told to press a button in response to certain facial expressions or digits to maintain their focus.

But – and here's the tricky part – the participants were interrupted at random every 30 to 70 seconds. Then researchers asked whether their mental state was "task-focused, mind-wandering or mind-blanking" and about their levels of sleepiness. At the same time eye pupil size was measured.

According to a paper published in Nature Communications today, researchers showed that slow waves in frontal brain areas preceded daydreaming and impulsive behaviour. However, when the same wave patterns occur further back in the brain they seemed to indicate mind blanking and slow responsiveness.

"The location of slow waves could distinguish between sluggish and impulsive behaviours, and between mind wandering and mind blanking. Our results suggest attentional lapses share a common physiological origin: the emergence of local sleep-like activity within the awake brain," the paper said.

The importance of the study is underscored by the observation that both in-lab and real-life studies show humans spend up to half of their waking lives not paying attention to their environment or any task at hand, remarkable for a species with such a strong evolutionary track record. At least now the researchers can suggest a physiological link to predict a wandering or blank mind.

"We propose that these slow waves reflect local intrusions of sleep within waking and constitute a mechanistic and proximate cause to explain attentional lapses. Identifying a proximate mechanism of attentional lapses could inspire novel applications leveraging brain-machine interfaces in educational or professional settings," the paper said.

It does not elaborate further on the precise "novel applications", but we're imagining a bucket of cold water propelled from behind the monitor, or a cartoon-like slap about the chops should the machine side of the interface suspect the human of not being "all there" following a large lunch. ®


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