Med thumb looking out window

When we’re immersed in activities that require our full focus — crunching numbers, proofreading travesties of syntax, evaluating fourth-quarter growth strategies — our minds don’t really wander. But, once we ditch the concentration-demanding tasks, we enter “mental rest” and the journeying begins. The meandering thoughts that make up our streams of consciousness may not follow any logical sequence, but they’re predictable in at least one way: They’re about us.

Self-reflection is a major component of mental rest. Even the mere act of shutting one’s eyes, studies have shown, corresponds to increased internal focus. Self-reflection is necessary for self-awareness — the capacity for continued, conscious distinction between one's self and the surrounding world. Self-awareness, in turn, is vital to psychological health. (Think about it. Exhibiting a lack of self-awareness is a telltale sign that someone is off.)

Neuroscience research supports the connection between zoning out and self-reflection. Brain scans performed during mental rest have shown increased activity in what’s known as the  Default Mode Network (DFM) — basically, the neural equivalent of airplane mode. During cognitively challenging tasks, on the other hand, the DFM shuts down.

Let’s put those thoughts together: Zoning out enables self-awareness. But the connection appears to go further. Suppressing the DFM during rest, according to cognitive scientists in Tel Aviv, disrupts our general sense of self.

For a study published earlier this year in the journal Consciousness and Cognition, the research team found that “turning off” (so to speak) the DFM during rest left people with feelings of dissociation  — i.e., the sort of out-of-body sensations similar to those experienced when under the spell of hypnosis, as well as with certain types of psychosis.

Here’s how they did it: Fifty-five participants took three tests to measure their levels of self-awareness, external awareness and dissociative feelings. Then, researchers (essentially) shocked their brains. Well, one-third of participants received a targeted form of deep brain stimulation, called Deep Transcranial Magnetic Stimulation, which, in effect, temporarily suppressed the DFM. Another third received a weaker type of magnetic stimulation that didn’t target the DFM network with the same specificity. And the remaining third only got fake shocks.

Following the brain-zapping sessions, participants were again randomly assigned to one of two activities. They either partook in mental rest (eyes closed, minds blank) or had to perform a cognitively challenging auditory task that required their full focus. Then, all participants repeated the psychological measures of awareness and disassociation.

Researchers were most interested in the group that received deep brain stimulation and then rested. Why? To review: Turning off the DFM translated to turning off the brain activity underlying reflective, stream-of-conscious thought. Mental rest is a period of self-reflection. If the study authors hypothesized correctly, participants with powered-down DFM would struggle to engage in self-aware thinking during their mental rest. But, since self-aware thinking is a lot of what we do when our minds take a load off, decreased ability to self-reflect should, they predicted, leave participants with feelings of dissociation and disrupted senses of self.

And, that’s basically what happened. The group-in-question reported dissociation and decreased self-awareness, while other participants, both those in the sham group and the weak stimulation group, didn't. Interestingly enough, the stimulated-and-rested participants only reported lower self-awareness, but maintained their levels of external awareness. The combined results, researchers wrote, supports their hypothesis: “Spontaneous PFC activity (DFM) during rest plays a critical role in the generation of self-related mental processing and is thus necessary for the intact, ongoing sense of self, or for the existence of the ever intriguing ‘stream of consciousness.”