Thread by @ZdenekVrozina

With longer duration of Long COVID, some key brain connections become weaker - especially those linked to prefrontal regulatory areas.
At the same time, other connections become stronger.
A new fMRI study shows this reflects a progressive reorganization of how brain networks communicate🧵

The study didn’t just look at isolated brain regions.
It examined how entire brain networks coordinate during cognitive effort - because performance depends less on single areas and more on how well networks synchronize

That synchronization was disrupted in Long COVID.
The main problem wasn’t damage to one function, but impaired regulation - the brain’s ability to detect what matters and shift efficiently into task-focused mode.

The most affected system was the salience network.
This network acts as a central switchboard.
It detects important stimuli or conflicts and shifts the brain between internal processing and active performance states.

In Long COVID, this network showed weaker connectivity with the rest of the brain - especially after prior mental exertion.
This suggests reduced capacity to regulate and coordinate activity under cognitive load.

Another key system involved was the central executive network.
It includes the prefrontal cortex and basal ganglia and supports planning, working memory, response selection, and filtering of distractions.

Deficits in this network produce a characteristic pattern.
Slower responses, difficulty filtering competing inputs, reduced ability to maintain task rules.
This reflects impaired regulatory control rather than isolated memory loss.

A crucial part of the study design was that brain activity was measured during two consecutive cognitive challenges.
The second run captured the brain after prior mental exertion.

During the second run, connectivity deficits became more widespread and new abnormal network patterns emerged.
This indicates that regulatory dysfunction worsens under cognitive stress.

At the same time, some regions showed increased connectivity.
Most notably the angular gyrus - an area integrating visual, language, and motor information.
The authors interpret this as a compensatory response.

Compensation does not mean the brain is functioning normally.
It usually means the opposite.
When core regulatory circuits weaken, the brain recruits alternative pathways to maintain performance.

These alternative pathways are less efficient and more energy demanding.
In simple terms -
the brain works harder to achieve worse results.

This aligns closely with what many patients describe.
Needing intense concentration for tasks that used to feel automatic.

Time dependent findings were especially important.
With longer illness duration, key regulatory connections continued to weaken - particularly those linked to prefrontal control systems!

Meanwhile, connections in visual and language networks became stronger.
This pattern suggests ongoing network adaptation to compensate for regulatory dysfunction.

Sum:
Long COVID has a measurable neurobiological signature in how brain networks coordinate during cognitive effort - and mental exertion amplifies these differences.
This pattern reflects dynamic reorganization of brain networks over time, rather than a static or purely residual condition.

Barnden at al., Impaired brain intrinsic connectivity in long COVID during cognitive exertion revealed by independent component analysis. Scientific Reports 2026. nature.com/articles/s4159…

This study fits a broader pattern seen across Long COVID research - persistent biological activity has been documented - including viral protein persistence and immune dysregulation - along with parallels to other chronic infections.

What is concerning here is the evidence of ongoing brain network remodeling over time.
This suggests a dynamic process in which regulatory circuits weaken while compensatory pathways strengthen.

The biggest unknown is scale - especially in younger populations/kids.
Long COVID likely exists on a spectrum, and it remains unclear how many people experience these network-level changes - especially beyond the most severe cases. @szupraha @ZdravkoOnline @adamvojtech86

Large national education datasets consistently report declines in literacy and numeracy outcomes among school-age children after the pandemic period.