Two 2025 studies confirm it:
In some people, COVID leaves parts of the brain functionally switched off.
PET and EEG both show disruptions in regions that control attention, motivation, and emotion.
What that actually means🧵
In some people, COVID leaves parts of the brain functionally switched off.
PET and EEG both show disruptions in regions that control attention, motivation, and emotion.
What that actually means🧵
Reduced glucose metabolism = less energy in certain parts of the brain, measured with PET using radioactive glucose. Siqueira et al., 2025.
Most affected: the left orbitofrontal cortex (just above the eyes), often extending into the frontal lobe.
Most affected: the left orbitofrontal cortex (just above the eyes), often extending into the frontal lobe.
This brain region handles:
executive functions
attention
emotional regulation
motivation
social behavior
When it’s underpowered - you may feel
brain fog
anxiety or apathy
lack of drive or disconnection from others
executive functions
attention
emotional regulation
motivation
social behavior
When it’s underpowered - you may feel
brain fog
anxiety or apathy
lack of drive or disconnection from others
Clinically, this matches what long COVID patients often describe:
I know what I want to do, but I just can’t get it done.
Everything takes me forever. I can’t think straight.
I don’t feel like myself.
These aren’t vague complaints. They point to a real biological disruption.
I know what I want to do, but I just can’t get it done.
Everything takes me forever. I can’t think straight.
I don’t feel like myself.
These aren’t vague complaints. They point to a real biological disruption.
EEG slowing - brainwaves shifting to a slower rhythm. Manganotti et al. 2025
What it is:
More slow waves (delta, theta)
Fewer normal rhythms (alpha, beta)
Where: Mostly in the left frontal region - the same area affected on PET
What it is:
More slow waves (delta, theta)
Fewer normal rhythms (alpha, beta)
Where: Mostly in the left frontal region - the same area affected on PET
What it means:
EEG slowing is a non-specific but serious sign of cortical dysfunction.
You see similar EEG patterns in
Alzheimer’s
inflammatory encephalopathies
severe metabolic disorders
In plain terms: this means the brain in these regions isn’t processing information effectively.
EEG slowing is a non-specific but serious sign of cortical dysfunction.
You see similar EEG patterns in
Alzheimer’s
inflammatory encephalopathies
severe metabolic disorders
In plain terms: this means the brain in these regions isn’t processing information effectively.
Why does it matter that PET and EEG show the same thing?
Two completely different tools (metabolism vs. electrical activity)
pointing to the same disrupted area
in the same group of patients
That’s strong evidence.
Not random.
Not just patient perception.
It’s an objective, biological problem.
Two completely different tools (metabolism vs. electrical activity)
pointing to the same disrupted area
in the same group of patients
That’s strong evidence.
Not random.
Not just patient perception.
It’s an objective, biological problem.
How does this fit into the long COVID puzzle?
SARS-CoV-2 affects:
blood vessels in the brain
inflammation and microglial activation
the blood–brain barrier
These can all lead to localized metabolic dysfunction in brain tissue.
SARS-CoV-2 affects:
blood vessels in the brain
inflammation and microglial activation
the blood–brain barrier
These can all lead to localized metabolic dysfunction in brain tissue.
And when both low metabolism and disrupted brain rhythms persist for months…
certain circuits stay dimmed
which explains chronic symptoms we associate with long COVID
This isn’t just tiredness or stress.
It’s measurable dysfunction.
certain circuits stay dimmed
which explains chronic symptoms we associate with long COVID
This isn’t just tiredness or stress.
It’s measurable dysfunction.
Persistent hypometabolism and EEG slowing have also been observed after:
HIV
HSV-1 encephalitis
Influenza A in severe cases
Zika virus, especially in infants
SARS-CoV-2 appears to join this group - but uniquely affects the orbitofrontal cortex more often and can do so without causing classic encephalitis.
HIV
HSV-1 encephalitis
Influenza A in severe cases
Zika virus, especially in infants
SARS-CoV-2 appears to join this group - but uniquely affects the orbitofrontal cortex more often and can do so without causing classic encephalitis.
The brain remembers. And sometimes, COVID doesn’t just fade away.
So if you’re experiencing brain fog after COVID - it’s not just in your head.
PET and EEG show clear signs of disrupted function, especially in brain areas critical for daily life.
So if you’re experiencing brain fog after COVID - it’s not just in your head.
PET and EEG show clear signs of disrupted function, especially in brain areas critical for daily life.
Manganotti et al. 2025. Mapping brain changes in post-COVID-19 cognitive decline via FDG PET hypometabolism and EEG slowing. nature.com/articles/s4159…
Siqueira et al., 2025. Metabolic brain changes in post-acute COVID-19: systematic review and meta-analysis of [18F]-FDG-PET findings. link.springer.com/article/10.100…
• • •
Missing some Tweet in this thread? You can try to
force a refresh
