The ADHD Loop Engine, Part 1: The Loop Machine

Why Your Brain Gets Stuck—And Why That's Not a Flaw

The Song That Won't Stop Playing

Picture this: Someone with ADHD looks up from their laptop and realizes it's 4 AM.

They've written 8,000 words. Built an entire system. Solved problems that had been stuck for weeks. Time disappeared. Meals were forgotten. The work that emerged? Couldn't have been created any other way. That kind of focus doesn't take requests—it arrives like weather.

Two days later, same person, different story.

Four hours spent mentally replaying a text message. Fourteen words. Read fifty times, each reading finding new ways to interpret it negatively. By hour three, a full narrative constructed—what went wrong, what it means, what's coming.

The text said: "Sounds good, let's talk later."

That's it. That's what hijacked the evening.

Same brain. Same mechanism. Opposite outcomes.

This is the ADHD loop engine. The same neural wiring that enables extraordinary hyperfocused creation is the exact same wiring that traps you in emotional spirals, anxiety loops, and 3 AM rumination about something said years ago.

The brain isn't broken. It's a loop machine—and nobody provides the manual.

Until now.

Explain This to Three People

Part 1: What ADHD Actually Is

Let's start by throwing out the name.

"Attention Deficit Hyperactivity Disorder" is a misnomer that's been confusing people for decades. People with ADHD don't have less attention. They have unregulated attention. The deficit isn't in the amount—it's in the control.

Here's what's actually happening:

The Interest-Based Nervous System

Dr. William Dodson coined this term, and it's the most accurate description of how ADHD brains allocate attention. The brain doesn't assign focus based on importance, deadlines, or consequences. It assigns focus based on:

• Interest: Is this genuinely fascinating right now?
• Novelty: Is this new, different, stimulating?
• Challenge: Is this the right level of difficulty?
• Urgency: Is there immediate pressure?

Notice what's missing: importance. Something can be critically important—taxes, that email, someone's feelings—and the ADHD brain will deprioritize it if it's not interesting, novel, challenging, or urgent.

This isn't laziness. This isn't a character flaw. It's architecture.

The Thermostat vs. The Light Switch

Here's a useful comparison:

Neurotypical brains operate like a thermostat. They adjust gradually. When something needs attention, focus increases proportionally. When something is boring but necessary, they can sustain moderate engagement. They regulate.

ADHD brains operate like a light switch. ON or OFF. When something captures interest, focus goes to 100%—hyperfocus, flow state, time disappears. When something doesn't capture interest, focus drops to near-zero, regardless of importance.

Neither system is wrong. They're different architectures optimized for different things. The thermostat is optimized for steady, sustained, controllable output. The light switch is optimized for intense bursts of high-performance focus—but it doesn't take requests.

The Loop Engine Reframe

So here's the reframe that will structure this entire series:

ADHD is not an attention deficit. It's an attention loop engine.

The brain locks onto whatever is most emotionally or mentally "loud"—and it doesn't let go easily. When that target is something productive (a creative project, a fascinating problem, a new skill), you get rocket loops: extraordinary output, rapid learning, flow states. When that target is something destructive (a perceived rejection, an ambiguous interaction, a shame spiral), you get gravity loops: rumination, anxiety, emotional hijacking.

Same engine. Different fuel. Same mechanism. Opposite outcomes.

The brain isn't broken. It's a loop machine operating exactly as designed—just without the manual explaining what it's designed FOR.

Part 2: The Dopamine Prediction Error Model

Now let's go deeper. What's actually happening at the neural level when the brain loops?

The Seeking State

ADHD brains have lower baseline dopamine activity. This isn't about having "less dopamine"—it's about how dopamine is regulated and released.

Lower baseline means the brain is in a constant seeking state. Always hunting for stimulation, always scanning for something interesting, always ready to lock onto a target. When it finds something that triggers dopamine release (novelty, challenge, interest, reward), it LATCHES.

This seeking state is why ADHD brains:

• Get bored easily with routine
• Crave novelty and stimulation
• Struggle with tasks that don't provide immediate feedback
• Can hyperfocus intensely on the "right" things

The VTA Broadcast System

The Ventral Tegmental Area (VTA) is the brain's dopamine broadcasting station. When something triggers it, the VTA sends dopamine signals to:

• Striatum: Handles reward processing and habit formation. Dopamine here says "this is valuable, keep doing it."
• Prefrontal Cortex: Handles planning, decision-making, and executive control. Dopamine here says "pay attention to this."

In ADHD brains, this broadcast system is dysregulated. When something interesting arrives, the broadcast is LOUD—overwhelming other signals, capturing attention completely. When something boring arrives (even if important), the broadcast is weak or absent.

This is why someone can focus on a video game for six hours but can't focus on an email for six minutes. The game triggers strong VTA broadcasts. The email doesn't.

Prediction Error: Why Loops Won't Release

Here's where it gets technical—but this is crucial for understanding why loops persist.

The brain uses prediction errors to learn and allocate attention. Based on the Rescorla-Wagner learning model:

• When something happens that was predicted, there's no prediction error. The brain moves on.
• When something happens that wasn't predicted (positive or negative), there's a prediction error. The brain pays attention, updates its model, and tries to resolve the error.

Loops persist because prediction errors aren't being resolved.

Consider a creative loop: Working on a project, each step reveals something new. New information = prediction error = dopamine = continued attention. The loop sustains itself through constant small discoveries until the project is complete (errors resolved) or novelty exhausted.

Now consider a rumination loop: Someone said something ambiguous. What did they mean? The prediction error can't be resolved because there's no clear answer. The brain keeps replaying it, searching for resolution that doesn't exist. The loop sustains itself through unresolvable uncertainty.

This is why "just stop thinking about it" doesn't work. The brain is doing exactly what it's supposed to do—trying to resolve prediction errors. But some errors (emotional ambiguity, social uncertainty, shame) have no resolution point. So the loop continues. Indefinitely.

The Drift Diffusion Model: Committing Too Fast

When making decisions, the brain accumulates evidence until it hits a threshold (boundary), then commits. The "boundary separation" determines how much evidence is needed before deciding.

ADHD brains often have low boundary separation for emotional decisions.

This means:

• Committing to interpretations too quickly
• Not accumulating enough disconfirming evidence
• Once committed, the loop locks in

That ambiguous message? A high-boundary-separation brain might think: "Hmm, unclear. I'll wait for more information before interpreting." A low-boundary-separation brain commits almost instantly: "They're upset with me." And once committed, the loop begins—and disconfirming evidence struggles to penetrate.

The brain commits too early to worry-loops and can't accumulate disconfirming evidence.

This is why reality-checking with another person helps. External perspective provides the disconfirming evidence the internal system won't seek on its own.

Wanting vs. Liking

Final piece of the dopamine puzzle—and this one is uncomfortable:

Dopamine signals salience, not pleasure.

Research distinguishes between "wanting" (dopamine-driven motivation to pursue) and "liking" (actual enjoyment when you get it). They're separate systems.

This means being trapped in a loop without enjoying it. The brain keeps pursuing the rumination, the checking, the replaying—not because it feels good, but because it's salient. The prediction error is unresolved. The loop must continue.

This explains:

• Gaming spirals where the fun stopped hours ago but stopping doesn't happen
• Doom scrolling that leaves you feeling worse
• Anxious rumination that clearly isn't helping but continues anyway

The choice isn't there. The dopamine system is pursuing salience, not pleasure. Understanding this removes some self-blame.

Part 3: The Default Mode Network—The Brain's Idle Loop Generator

If dopamine explains why loops latch, the Default Mode Network explains where loops come from.

What is the DMN?

The Default Mode Network is a set of brain regions that activate when not focused on external tasks. It's the brain's "idle mode"—what happens when not actively doing something.

DMN functions include:

• Self-reflection and introspection
• Mind-wandering and daydreaming
• Future planning and simulation
• Processing past events
• Social cognition and mentalizing

In neurotypical brains, the DMN activates during rest and deactivates during focused tasks. It's like a screensaver that turns on when the computer isn't in use.

The ADHD DMN Difference

ADHD brains show atypical DMN activity in two ways:

1. DMN doesn't deactivate properly during tasks.

When trying to focus on something, the DMN keeps intruding. Random thoughts, tangential ideas, unrelated memories—these are the DMN refusing to go quiet. This is the neurological basis of "distractibility."

2. DMN goes into overdrive during downtime.

When not focused on something external, the DMN doesn't just activate—it dominates. Without a task to suppress it, the brain generates content at high volume.

The Loop Generator

Here's the crucial insight:

The brain's idle mode is a loop generator.

During low-stimulation states, the DMN produces content. In ADHD brains with low baseline dopamine, the DMN is essentially starving for stimulation—so it generates its own.

What does it generate? Whatever is most salient:

• If novelty is salient: Creative ideas, new projects, interesting connections (rocket fuel)
• If threats are salient: Worries, fears, worst-case scenarios, social threats (gravity fuel)

The DMN doesn't discriminate. It generates loops from whatever raw material is available. Recent rejection, ambiguity, or conflict? That's the raw material. Recent fascinating discovery? That's the raw material.

Good Loops Suppress DMN, Bad Loops Amplify It

This is the key mechanism:

Rocket loops SUPPRESS the DMN. When hyperfocused on an external task, the DMN goes quiet. All resources directed outward. No mind-wandering, no self-reflection, no rumination. Just flow.

Gravity loops AMPLIFY the DMN. When ruminating, the DMN is in overdrive. All resources directed inward. The loop generates more content, more scenarios, more replay—feeding itself.

This is why rocket loops feel effortless and gravity loops feel inescapable. In rocket mode, the loop generator is off. In gravity mode, it's running at maximum.

The Night Problem

Evening is the danger zone for gravity loops. Here's why:

Circadian dopamine dip. Dopamine levels naturally decline in the evening as part of the circadian rhythm. Lower dopamine means less fuel for executive control and DMN suppression.

Reduced external stimulation. Evening typically involves less task engagement, fewer novel inputs, more downtime. Less external focus = more DMN activation.

Accumulated stress. By evening, the day's unresolved prediction errors have accumulated. The DMN has plenty of raw material.

This is why 3 AM is the classic rumination hour. Low dopamine + no external focus + accumulated stress = DMN running wild with no suppression available.

Part 4: Memory Systems—Why Some Loops Stick Harder

The hippocampus—the brain's memory formation center—plays a crucial role in why some loops are easy to exit and others trap for days.

Pattern Separation: Why Learning Happens So Fast

The dentate gyrus, a region within the hippocampus, performs pattern separation—storing new information as distinct, separate memory traces.

In ADHD brains, this system works remarkably well during interest-driven learning:

• New information arrives rapidly during hyperfocus
• Pattern separation stores each piece distinctly
• Minimal interference between new memories
• Result: Entire skills learned in a weekend

This is the neurological basis of the polymath tendency in ADHD. When the interest system is engaged, the memory system is optimized for rapid, distinct encoding.

Pattern Completion: Why Letting Go Is Hard

The CA3 region of the hippocampus performs pattern completion—reconstructing full memories from partial cues.

This is supposed to be helpful. Smell of cookies → full memory of grandmother's kitchen. Old song → full memory of that summer.

But in emotional contexts, pattern completion becomes a trap:

• One small cue (a word, a tone, a silence)
• CA3 reconstructs the FULL associated memory
• Including all the emotional content
• Loop activates from a fragment

This is why a single ambiguous message can trigger a four-hour spiral. The message is a partial cue. The brain completes the pattern with the full emotional memory of every similar situation. One data point → full catastrophe movie.

Emotional Consolidation: Slow and Stubborn

Memory consolidation—the process of stabilizing and storing memories long-term—happens differently for emotional content:

• Emotional memories consolidate more slowly
• They require more processing time
• Without intervention, they keep reactivating
• Each reactivation strengthens the trace

This is why rejection loops can last for days. The emotional memory isn't consolidated—it keeps reactivating, each reactivation strengthening it, creating a self-reinforcing cycle.

The good news: This slow consolidation window is also an intervention point. Interrupting the loop before consolidation completes can weaken the trace. This is why the "24-hour cue parking" technique works—it allows consolidation to settle before engaging with the emotional content.

Part 5: Executive Function—The Control Problem

The final piece of the loop puzzle: executive function.

The Top-Down Problem

Executive function refers to the "top-down" cognitive processes that enable controlling behavior, overriding impulses, switching tasks, and directing attention voluntarily. Key brain regions include:

Dorsolateral Prefrontal Cortex (dlPFC): Task-switching, working memory, cognitive flexibility. This enables shifting attention from one thing to another.

Anterior Cingulate Cortex (ACC): Conflict monitoring, error detection. This notices when something's wrong or when current focus conflicts with goals.

Frontal Eye Fields (FEF): Voluntary attention direction. This enables consciously deciding where to focus.

In ADHD, all three systems show reduced activation or connectivity.

The Detection-Without-Resolution Problem

Here's a crucial insight:

The ACC detects the conflict. The dlPFC can't resolve it.

When stuck in a gravity loop, part of the brain KNOWS there's looping happening. The ACC is firing: "Hey, this rumination is conflicting with the goal of sleeping. Hey, this worry isn't helping. Hey, this message has been read fifty times."

But the dlPFC—the part that would normally override and switch tasks—doesn't have the activation to execute the switch. Awareness of being stuck. Inability to get unstuck.

This is why "just stop thinking about it" is useless advice. The detection system works fine. The resolution system is underpowered. Knowing there's looping. Not being able to exit.

ADHD loops persist because executive control can't override salience—the brain detects the conflict (ACC) but can't switch tasks (dlPFC).

The Bottom-Up Hijack

Without strong top-down control, bottom-up salience wins every time.

Whatever is most emotionally LOUD captures attention. Interest, threat, novelty—these bottom-up signals hijack the attention system because the top-down systems can't compete.

This is why:

• Games get hours of focus (high bottom-up salience) but emails don't (low salience)
• Emotional threats capture attention even when trying to focus elsewhere
• "Boring but important" loses to "interesting but trivial" every time

Why Body-Doubling Works

Here's a practical implication:

Body-doubling—having another person present while working—provides external executive function.

Another person's presence serves as an external signal that helps activate control systems. Borrowed attention helps suppress the DMN. External expectations create urgency that internal systems can't generate.

This isn't weakness or dependence. It's strategic scaffolding. If internal FEF is underpowered, borrow external FEF. Organizations do this all the time—it's called "management." Individuals should too.

The Loop Engine Diagram

Here's the complete system:

THE ADHD LOOP ENGINE
                           
     ┌─────────────────────────────────────────────────┐
     │   DOPAMINE SYSTEM                               │
     │   VTA → Broadcasts to Striatum + PFC            │
     │   Prediction errors drive attention locking     │
     │   Low boundary separation = commits too fast    │
     └────────────────────┬────────────────────────────┘
                          │
                          ▼
     ┌─────────────────────────────────────────────────┐
     │   EXECUTIVE CONTROL (Weakened)                  │
     │   dlPFC: Can't switch tasks                     │
     │   ACC: Detects conflict, can't resolve          │
     │   FEF: Can't direct attention voluntarily       │
     │   → Bottom-up salience wins                     │
     └────────────────────┬────────────────────────────┘
                          │
            ┌─────────────┴─────────────┐
            ▼                           ▼
    ┌───────────────┐           ┌───────────────┐
    │ ROCKET LOOP 🚀│           │GRAVITY LOOP 🌀│
    │ DMN Suppressed│           │ DMN Amplified │
    │ External focus│           │ Internal focus│
    │ Pattern sep.  │           │ Pattern comp. │
    │ "Unstoppable" │           │ "Can't escape"│
    └───────────────┘           └───────────────┘
            │                           │
            └─────────────┬─────────────┘
                          ▼
     ┌─────────────────────────────────────────────────┐
     │   HIPPOCAMPUS                                   │
     │   Dentate: Separation → Learn fast (gift)       │
     │   CA3: Completion → Stuck replay (trap)         │
     │   Emotional memories consolidate slowly         │
     └─────────────────────────────────────────────────┘

Part 6: The Foundation

The mechanism is now understood.

Dopamine prediction errors create the locking behavior. The brain latches onto whatever generates prediction errors—novelty, threat, unresolved emotional content—and won't let go until errors resolve.

Low boundary separation means committing to interpretations too fast. One ambiguous interaction becomes a catastrophe before disconfirming evidence accumulates.

The Default Mode Network generates loop content during low-stimulation states. Rocket loops suppress it. Gravity loops amplify it. Evening is the danger zone.

Memory systems explain both the gift and the trap. Pattern separation enables fast learning. Pattern completion triggers full emotional replay from fragments.

Weakened executive control means detecting looping but not being able to override it. The ACC fires; the dlPFC can't respond.

Same hardware, different outcomes. Creative genius and anxious mess share an engine. One doesn't exist without the other.

The Reframe

This isn't a broken neurotypical brain. It's a different operating system with different specs.

The loop engine is powerful. When pointed at something valuable—a creative project, a fascinating problem, a new skill—it produces extraordinary results. When pointed at something destructive—a perceived rejection, an ambiguous interaction, a shame memory—it produces suffering.

The engine will loop. That's what it does.

The job isn't to delete the engine. It's to:

• Recognize when looping is happening
• Identify whether it's a rocket or gravity loop
• Exit gravity loops faster
• Protect and sustain rocket loops intentionally

What's Coming

Part 2 maps the territory—every type of loop, what it looks like, what it costs, what it gifts. The creative loop, the learning loop, the problem-solving loop. The emotional loop, the rejection loop, the shame loop. Same hardware, full taxonomy.

Part 3 delivers the tools—the Loop Kit. How to SPOT when looping. How to SWITCH out of gravity loops. How to STEER toward rocket loops. Scripts, experiments, the 14-day protocol to build a personalized manual.

The loop engine exists. Now let's learn to drive it.

Research & Citations

Neuroscience foundations:

• Volkow et al. on dopamine transporter differences
• Rescorla-Wagner prediction error model
• DMN studies in ADHD populations
• Barkley on ADHD as emotional regulation disorder
• Dodson on Interest-Based Nervous System and RSD

Course concepts integrated:

• Dopamine signaling and prediction error (reward learning research)
• Default Mode Network activity patterns
• Hippocampal pattern separation and completion
• Executive function and prefrontal control systems
• Drift diffusion models of decision-making

Continue the Series

→ [Part 2: Rocket Loops & Gravity Loops](/blog/adhd-loop-engine-part-2-rocket-loops-gravity-loops)

Mapping every loop type—what they look like, what they cost, what they gift

→ [Part 3: The Loop Kit](/blog/adhd-loop-engine-part-3-the-loop-kit)

Tools, scripts, and experiments for working WITH the brain

If this framework helps, share it with someone whose brain works the same way. The manual is for everyone who never got one.