Mindly Different

Your Brain’s Energy

If you’ve ever felt mentally exhausted after what seems like a “normal” day – even if to others around you seem fine – you’re not imagining it. And you’re not weak, unmotivated, or lazy. Cognitive fatigue is real, measurable, and deeply tied to how the brain manages its energy.

For neurodivergent people and those living with brain injuries, this experience can be especially intense. Tasks that appear simple from the outside – answering messages, making decisions, switching between activities, maintaining focus – can drain the brain much faster and much deeper than most people realize.

But why does this happen?

Your Brain Runs on Energy (and Some Tasks Cost More Than Others)

Your brain uses a surprisingly large amount of energy just to keep you functional. And some forms of mental activity – especially those involving planning, self-regulation, attention, and flexible thinking – require significantly more neural resources than others.

This is why things like:

• staying organized
• coping with sensory input
• reading social cues
• shifting between tasks
• making decisions

…can leave you feeling depleted long before the day is over.
This isn’t a personality trait. It’s an energy equation.

What Science Reveals About the Biology of Cognitive Fatigue

Recent research is helping clarify what many neurodivergent individuals and brain-injury survivors have known intuitively for years: cognitive exhaustion has a biological foundation.

Using advanced techniques that measure chemical activity inside the brain, scientists have observed changes in the lateral prefrontal cortex, the region responsible for working memory, focus, inhibitory control, and high-level decision-making.

Here’s what they found:

When people engage in demanding mental tasks, the lateral prefrontal cortex shows a build-up of glutamate, one of the brain’s major excitatory neurotransmitters. But this build-up does not occur when people perform simpler, low-effort tasks.

This suggests something important:

Fatigue arises from metabolic changes in cognitive-control regions when they are pushed too hard or too long.

As these metabolic alterations grow, the “cost” of using cognitive control increases. This makes the brain naturally shift toward:

• easier tasks
• reduced effort
• and quick, low-energy rewards

This biological shift is what we feel as cognitive fatigue.

In simple terms: Your brain isn’t failing you – it’s protecting you.

Why This Matters for Neurodivergent Brains and Brain-Injury Survivors

For many of us with non-typical brains, the systems responsible for self-regulation, sensory processing, and executive functioning require more energy to operate in environments designed for neurotypical rhythms.

If you’re autistic, ADHD, dyslexic, or otherwise neurodivergent, or if you’re living with the effects of a brain injury, your brain often works twice as hard just to perform tasks that others complete automatically.

Your cognitive fatigue isn’t imaginary.
It isn’t being dramatic or lazy.

It’s biology.

Why This Fatigue Feels So Hard to Explain

Unlike physical exhaustion, cognitive fatigue is invisible.
You may look fine. You may still be standing, thinking, or speaking.
But internally, your system may be depleted.

This invisibility is why many people feel misunderstood or judged.

It’s also why people with neurodivergent minds or brain injuries often push themselves past their limits – wanting to keep up, keep smiling, keep performing, keep proving they’re “fine”. But the brain has boundaries. And listening to those boundaries is not weakness.

It’s wisdom.

I say this from experience. For years, I ignored my body’s signals. I ridiculously masked. I pretended. I pushed through exhaustion and sensory overload, believing that effort and resilience were the only acceptable answers. Deep down, I knew that this pattern was doing more harm than good, yet, thanks to my bringing up, I didn’t know another way to be.

There are still moments when I struggle to forgive myself for that – for not understanding sooner, for the pressure I placed on a brain that was trying to heal, for the ways I may have slowed or interrupted my own recovery. But I’m learning, slowly and now more compassionately, that this too is part of the journey: recognizing past patterns not to punish myself, but to choose differently now.

What Cognitive Fatigue Can Look Like

Some signs include:

• mental fog or slow processing
• sudden irritability
• difficulty speaking or putting thoughts together
• emotional sensitivity
• inability to focus
• feeling overstimulated or “buzzing” inside
• a strong urge to withdraw
• physical heaviness or imbalance

These are not moral failures or signs of low resilience.
They are physical symptoms of a brain doing its best under strain.

Supporting Your Brain’s Energy: What Actually Helps

You don’t have to “push through” cognitive fatigue. In fact, pushing through can prolong recovery and intensify symptoms.

Here are some effective strategies that may help:

• Pacing and micro-rests. Short, regular breaks prevent overload better than long, occasional rests.
• Lowering cognitive load. Reduce steps, simplify tasks, use routines and external supports (lists, reminders).
• Sensory regulation. Reducing sensory input lowers the energy cost of daily life.
• Monotasking. Doing one thing at a time is not a luxury – it’s brain-friendly.
• Emotional self-regulation. Calming your nervous system reduces cognitive demand.
• Recognizing early signs of overload. Irritability, zoning out, or visual strain are signals, learn to detect them early.
• Compassionate boundaries. Protecting your energy is part of respecting your unique brain.

Learning to understand your brain’s energy needs is one of the most compassionate things you can do for yourself.
Rest becomes not an indulgence, but a form of neurological care.
Pauses become strategy, not defeat.
And recognizing your limits becomes a stepping stone toward a healthier, more grounded everyday life.

Your brain is different – beautifully, meaningfully, uniquely different – and it deserves to be supported, not pushed beyond its energetic boundaries.

By Nataliya Popova
Mindly Different – Coaching for the beautifully different mind