How turning off the mind helps us understand what’s going on in the mind

We usually think that our mind is full of thoughts when we are awake. Like an ever-flowing river, we are entertained by our own dynamic mental stream: one thought can lead to another, relevant to what we do or don’t do, that lies between our inner life and our outer environment. However, how can the brain continuously maintain such a thought-related mode? A study just published in the Proceedings of the National Academy of Sciences points out that it really can’t, and that our brains also need to “go off the grid” for some moments that we can experience as gaps in consciousness.

Researchers from the University of Liège and the EPF Lausanne and the University of Geneva reanalyzed previously collected data set where healthy participants reported their state of mind before hearing the auditory probe (beep) while resting in the MRI scanner. Responses included environmental perception, stimulus-dependent thoughts, stimulus-independent thoughts, and mental absences. Functional images were collected during this experience sampling method.

The researchers found that mind-switching episodes were reported relatively infrequently compared to other conditions, and that they also appeared less frequently over time. Using machine learning, researchers discovered that our brains are organized in such a way that during mind-switching episodes, all areas of the brain were communicating with each other at the same time.

This ultra-resolved brain pattern was also characterized by high global fMRI signal amplitude, which is a proxy for low cortical excitability. In other words, when we report mind off, it appears that our brain is in a mode similar to deep sleepwe just woke up.

“Mind switching off is a relatively new mental state within the study of spontaneous cognition. It opens up exciting opportunities for studying the underlying biological mechanisms that occur during wakefulness. Perhaps the boundaries between sleep and wakefulness are not as discrete as they seem after all,” says the lead researcher Dr. Demerci Athena, FNRS researcher at GIGA ULiège.

“It changes constantly and quickly brain activity reliable methods of analysis are required to confirm the specific sign of unconsciousness,” continues Dr. Van De Wiel Dimitri.

The researchers argue that the robust neurofunctional profile of mind shutdown may account for the inability to report mental content due to the brainInability to differentiate signals informatively. Pending elucidation of the underlying mechanisms, this work suggests that momentary unreported mental events may occur during wakefulness, making gaps in consciousness a salient mental state during prolonged experience.