Scientists may have finally solved the mystery behind “brain fog” in people with long Covid — a condition that has frustrated patients and doctors for years. Millions who caught the virus still struggle with memory lapses, slow thinking, and trouble focusing long after recovery.

A new Japanese study has found a clear biological reason. Using advanced brain imaging, researchers discovered abnormal activity in AMPA receptors — the parts of the brain that handle memory and learning. “Our findings prove that long Covid brain fog is a real medical condition,” said Professor Takuya Takahashi, one of the study’s authors. This breakthrough could open the door to more accurate diagnoses and targeted treatments in the near future.

The team compared brain scans from 30 long Covid patients to 80 healthy volunteers. They found that the more severe the brain fog, the denser the receptor activity — suggesting a direct link between AMPA dysfunction and cognitive symptoms. Scientists believe this may explain why so many long Covid patients feel mentally drained months or even years after infection.

With new Covid variants like Stratus and Nimbus spreading, experts warn that brain fog and other lingering symptoms could affect even more people. “This discovery gives hope that we can finally treat the invisible struggles of long Covid,” said one researcher. For now, health officials continue urging people to wear masks and isolate if sick — small steps that can help prevent lasting damage.