Our minds feel trapped in endless loops of thought for a reason—and that reason is ancient.
To understand it, we have to go back to the caveman.

What we now call the Default Mode Network (DMN) was once a survival advantage. It is the brain’s internal simulator, constantly stitching together memory, identity, and imagination into a working model of reality.

Where should we hunt for antelope?
Across the river, perhaps.
Any danger?
Last time, there were lions nearby.
Solution?
Bring spears. Bring allies. Prepare for the worst.

This ability to replay the past and project it forward—part memory, part prediction—kept early humans alive. The DMN didn’t just plan; it told stories. Stories about who we were, what had happened, and what might happen next.

And it had a talent for catastrophe.

What if the hunt fails?
My family starves.
Winter is coming.
We need backups—fish from the river, thicker shelter, contingency upon contingency.

This wasn’t a flaw. It was insurance against extinction.

Alongside it worked another system: the Salience Mode Network (SMN)—the brain’s sentinel and gatekeeper. While others slept, someone always stood watch. A moment of inattention could mean death. The SMN scanned everything: the pressure of bare feet on dirt, the rhythm of crickets, the shift of air on the skin.

Then—silence breaks.
A roar.

The SMN flags it instantly: This matters.
Heart rate surges. Adrenaline floods the body. Muscles tense before conscious thought even forms.

The Salience Network doesn’t think in sentences. It points. It taps the shoulder of the brain and says, Pay attention. Now.

Together, the DMN and SMN helped humanity survive for thousands of years.

But the world changed.

Wild predators faded. Food became reliable. Shelter stopped being a daily gamble. Evolution, however, moves slowly. Our neural settings remain tuned for a world that no longer exists.

That’s where the trouble begins.

An overactive DMN replays the past on a relentless loop—a failed business, a broken relationship, a moment of humiliation. It then projects those memories forward, predicting failure before the future even arrives. The story becomes heavy, repetitive, inescapable.

“Ever lie in bed thinking, I need to sleep—only to feel sleep retreat further away? The harder you try, the more alert you become. The CEN behaves like an overachieving employee, surfacing every unfinished task the moment the lights go out“

At the same time, the Salience Network may remain overly sensitive, constantly flagging internal sensations and external cues as potential threats. Every sound feels loaded. Every glance seems meaningful. The body stays on edge, unable to fully relax.

Anxiety doesn’t arise from one network alone. It emerges when the SMN keeps sounding alarms and the DMN supplies an endless narrative explaining why those alarms must be right.

Modern brain imaging reveals something crucial: these networks are not isolated switches. The DMN and the Central Executive Network (CEN)—the system responsible for focused attention and problem-solving—tend to compete for dominance. The Salience Network sits between them, acting as a traffic controller, deciding whether attention should turn inward to thought and memory, or outward toward action and control.

When the DMN dominates, we drift inward. We ruminate. We mentally time-travel. Minutes vanish. You open your phone and forget why. You replay conversations that ended years ago.

When the Salience Network keeps flagging danger, the world begins to feel hostile. Crowds tighten the chest. Silence feels suspicious. Panic lurks just beneath awareness. In conditions like social anxiety or phobias, harmless cues are repeatedly mislabeled as threats, keeping the body locked in defensive mode.

What once protected us now overwhelms us.

Then there is the Central Executive Network (CEN)—the brain’s operator. If the DMN tells the story and the SMN decides what matters, the CEN gets things done. It holds information in working memory, builds mental to-do lists, prioritizes tasks, and suppresses distractions long enough to act.

It is not the narrator of your inner world—but it is the one trying to manage it.

When you’re thinking hard, organizing plans, or solving problems, the CEN is active. When it’s overloaded, it struggles to shut down. Lying in bed, it keeps reaching for unfinished tasks, unresolved questions, and imagined consequences.

You stare at the ceiling, replaying tomorrow’s meeting.
What if they complain again?
What does that mean for my job?
Did I miss something important?

Each thought cues another. The Salience Network flags the thoughts as relevant. The DMN spins meaning around them. The CEN tries—and fails—to bring order. Your heart rate rises. Breathing becomes shallow. Sleep slips away.

Ironically, the CEN often ends up working overtime because the other systems won’t quiet down. None of these networks are villains. They’re automatic, ancient, and loyal.

The good news is that the CEN is the most accessible to conscious influence.

This insight has shaped modern relaxation and mindfulness-based therapies. Brainwave research shows that different mental states correspond to different patterns of brain activity. Relaxed wakefulness often brings increased alpha rhythms, while effortful thinking engages faster beta and gamma activity. Delta waves dominate deep sleep, not waking calm—but the overall picture is clear: a mind no longer fighting itself begins to slow.

Neurofeedback and meditation practices aim to help people recognize and enter these calmer states, training the brain to step out of constant control mode. While the technology can be sophisticated, the core skill is surprisingly simple.

Try this.

Set a timer. Close your eyes. Don’t try to force your mind empty. Instead, notice how quickly thoughts appear. A reminder. A worry. A fragment of a story. When one arises, stop the timer.

Most people last only seconds.

Now try again, but give your attention a gentle anchor—your breathing. Notice the rise and fall of the chest. The sensation of air moving in and out. When attention drifts, calmly return it.

Slow breathing directly softens the Salience Network’s alarm signals. As those alarms quiet, the DMN runs out of fuel for catastrophic storytelling. The CEN no longer needs to intervene. Balance returns—not because the networks shut off, but because they stop fighting for control.

Even brief moments of this state can ease the burden of constant mental effort.

Give your inner operator a break.

The Sleep Paradox

Ever lie in bed thinking, I need to sleep—only to feel sleep retreat further away? The harder you try, the more alert you become. The CEN behaves like an overachieving employee, surfacing every unfinished task the moment the lights go out.

And yet sleep arrives effortlessly in strange places: on long highway drives, in dim lecture halls, during painfully dull meetings.

What do these situations share?

A single, neutral, repetitive focus. Something unthreatening. Almost boring.

Some therapists advise people with insomnia to try a counterintuitive approach: stop trying to sleep. Instead, focus on one gentle sensation—the sound of a fan, the rhythm of the breath. As the Salience Network stops flagging danger and the DMN loses its narrative grip, the CEN finally stands down. Sleep arrives unnoticed.

A Date with the Mind

For many people, nighttime rest is elusive because the day never truly ends. The brain never receives a clear signal that work is finished.

A practical fix exists.

Two or three hours before bed, step away from demanding tasks. Then deliberately review tomorrow. Write the list. Organize it. Make decisions. When finished, consciously conclude the process.

This creates psychological closure. It tells the Central Executive Network that its job is done. Without that signal, it keeps running background programs deep into the night.

Like a computer given a proper shutdown command, the mind releases unnecessary processes when it knows the workday has ended.

Your mind doesn’t need to work less.
It just needs to know when to stop.

In the end, the restless mind isn’t broken—it’s loyal.

It is doing exactly what it evolved to do: anticipate danger, scan for meaning, prepare for what might go wrong. The problem is not the brain, but the era it operates in.

The caveman never had email.
Never had deadlines without sunsets.
Never carried unfinished conversations into bed.

Peace doesn’t come from silencing the mind by force. It comes from reassuring it. Letting it know the fire is lit, the shelter is secure, and tonight—no lions are coming.

When we slow our breathing, narrow our focus, or consciously close the mental ledger of the day, we aren’t fighting our neural networks. We are coordinating them.

We tell the Default Mode Network it can stop predicting.
The Salience Network that it can stand down.
And the Central Executive Network—faithful and exhausted—that its shift is finally over.

Rest does not come from doing nothing.
It comes from knowing that, for now, nothing more needs to be done.

And sometimes, the most powerful thing a modern human can do
is remind an ancient brain
that it is safe to sleep.

A Friendly Reality Check Before closure

The human brain is a beautifully busy place. Scientists describe it as having seven interconnected neural loops working behind the scenes.

In this article, we’re shining the spotlight on just three of them—the SMN, DMN, and CEN—not because the others don’t matter (they absolutely do!), but because these three help tell a clearer, more digestible story for everyday readers. Think of this as a simplified map, not the entire territory.

You’ll also come across a few gentle techniques along the way—like mindful meditation or the idea of a “sleep paradox.” These are meant as easy, practical tools to help you unwind and better understand your mind. They’re not medical treatments, and they’re definitely not substitutes for professional care.

If you’re dealing with ongoing insomnia, anxiety, depression, or emotional distress, you don’t have to handle it alone. A qualified mental health professional can offer the kind of support and guidance that no article—no matter how well-intentioned—can replace

This article is authored by Dr Chong Siew Koon, Psychiatrist, Hospital Kuala Lumpur, and Dr Ong Wan Xi, Psychiatrist, Hospital Taiping.