Long COVID: How lost connections between nerve cells in the brain may explain cognitive symptom

Scientists are working to understand how a COVID infection affects the human brain.

For a portion of people who get COVID, symptoms continue for months or even years after the initial infection. This is commonly referred to as “long COVID”.

Some people with long COVID complain of “brain fog”, which includes a wide variety of cognitive symptoms affecting memory, concentration, sleep and speech. There’s also growing concern about findings that people who have had COVID are at increased risk of developing brain disorders, such as dementia.

Scientists are working to understand how exactly a COVID infection affects the human brain. But this is difficult to study, because we can’t experiment on living people’s brains. One way around this is to create organoids, which are miniature organs grown from stem cells.

In a recent study, we created brain organoids a little bigger than a pinhead and infected them with SARS-CoV-2, the virus that causes COVID-19.

In these organoids, we found that an excessive number of synapses (the connections between brain cells) were eliminated – more than you would expect to see in a normal brain.

Also Read | What is – and what isn’t – ‘brain fog’?

Synapses are important because they allow neurons to communicate with each other. Still, the elimination of a certain amount of inactive synapses is part of normal brain function. The brain essentially gets rid of old connections when they’re no longer needed, and makes way for new connections, allowing for more efficient functioning.