COVID can damage memory - even months after recovery.
Not just any memory: the precision of memory, tied to the hippocampus.
A new study shows that it doesn’t recover over time!
It actually gets worse.
A short thread on the hippocampus, neurogenesis, and a virus that lingers.🧵
Not just any memory: the precision of memory, tied to the hippocampus.
A new study shows that it doesn’t recover over time!
It actually gets worse.
A short thread on the hippocampus, neurogenesis, and a virus that lingers.🧵
The hippocampus isn’t just - a memory disk.
It’s one of the only brain areas where new neurons grow in adulthood!
It helps us:
learn new things
navigate space and time
distinguish between “same” and “similar”
Exactly what “brain fog” disrupts.
It’s one of the only brain areas where new neurons grow in adulthood!
It helps us:
learn new things
navigate space and time
distinguish between “same” and “similar”
Exactly what “brain fog” disrupts.
A new study (Meyer & Zaiser, 2025) tested >1400 people using a memory precision task.
People post-COVID showed significantly lower scores (LDI).
The deficit appeared even in those who felt fully recovered!
This wasn’t fatigue or depression.
It was hippocampal dysfunction.
People post-COVID showed significantly lower scores (LDI).
The deficit appeared even in those who felt fully recovered!
This wasn’t fatigue or depression.
It was hippocampal dysfunction.
The most concerning finding?
The longer since infection, the worse the result.
Memory didn’t improve - it declined.
This suggests:
persistent neuroinflammation,
or
a slow, degenerative process.
The longer since infection, the worse the result.
Memory didn’t improve - it declined.
This suggests:
persistent neuroinflammation,
or
a slow, degenerative process.
Memory isn’t just about “how much” you remember.
It’s about how precisely your brain can separate similar events.
Losing that ability means:
poor decisions
impaired learning
mental exhaustion
Often without being aware of it.
It’s about how precisely your brain can separate similar events.
Losing that ability means:
poor decisions
impaired learning
mental exhaustion
Often without being aware of it.
The hippocampus is a silent but essential player.
COVID can disrupt its function even without severe illness.
And time alone may not heal it.
Worse: the process may slowly continue.
COVID can disrupt its function even without severe illness.
And time alone may not heal it.
Worse: the process may slowly continue.
What do other studies show?
Post-mortem findings in COVID-19 patients:
fewer new neurons in the dentate gyrus
activated microglia
elevated CCL11 - a known blocker of neurogenesis
Animal models:
loss of newborn neurons
memory deficits
behavioral changes
Post-mortem findings in COVID-19 patients:
fewer new neurons in the dentate gyrus
activated microglia
elevated CCL11 - a known blocker of neurogenesis
Animal models:
loss of newborn neurons
memory deficits
behavioral changes
We don’t yet know how long the neurogenesis block lasts.
But we do know:
it can persist for months or more
and may take on degenerative features in some people
In a chronically inflamed hippocampus, new neurons may be completely suppressed.
But we do know:
it can persist for months or more
and may take on degenerative features in some people
In a chronically inflamed hippocampus, new neurons may be completely suppressed.
Sound familiar?
Some HIV’s proteins (Tat, gp120) - hippocampal inflammation, loss of neurogenesis, cognitive decline.
SARS-CoV-2? Spike, ORF3a, N, E.
Different virus, same target.
Some HIV’s proteins (Tat, gp120) - hippocampal inflammation, loss of neurogenesis, cognitive decline.
SARS-CoV-2? Spike, ORF3a, N, E.
Different virus, same target.
Long COVID isn’t just “feeling tired.”
It’s a measurable, inflammatory brain syndrome.
And the hippocampus may be one of its first victims.
It’s a measurable, inflammatory brain syndrome.
And the hippocampus may be one of its first victims.
Meyer & Zaiser, 2025, Insights on the neurocognitive mechanisms underlying hippocampus-dependent memory impairment in COVID-19
nature.com/articles/s4159…
nature.com/articles/s4159…
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