Of long COVID’s many possible symptoms, brain fog “is by far one of the most disabling anddestructive,” said Emma Ladds, a primary-care specialist from the University of Oxford. It’s alsoamong the most misunderstood. It wasn’t even included in the list of possible COVID symptomswhen the coronavirus pandemic first began. But 20-30% of patients report brain fog three monthsafter their initial infection, as do 65-85% of the long-haulers who stay sick for much longer. It canafflict people who were never ill enough to need a ventilator—or any hospital care. And it canaffect young people in the prime of their mental lives.
       Long-haulers with brain fog say that it is more profound than the clouded thinking thataccompanies hangovers, stress, or fatigue. It is not psychosomatic, and involves real changes to thestructure and chemistry of the brain. It is not a mood disorder: “If anyone is saying that this is dueto depression and anxiety, they have no basis for that, and data suggest it might be the otherdirection,” said Joanna Hellmuth, a neurologist at UC San Francisco.
        And despite its nebulous name, brain fog is not an umbrella term for every possible mentalproblem. At its core, Hellmuth said, it is almost always a disorder of “executive function”—the setof mental abilities that includes focusing attention, holding information in mind, and blocking outdistractions. These skills are so foundational that when they crumble, much of a person’s cognitiveedifice collapses. Anything involving concentration, multitasking, and planning—that is, almosteverything important—becomes absurdly arduous. “It raises what are unconscious processes forhealthy people to the level of conscious decision making,” said Fiona Robertson, a writer based inAberdeen, Scotland. Several clinicians argued that the term brain fog makes the condition soundlike a temporary inconvenience and deprives patients of the legitimacy that more medicalizedlanguage like cognitive impairment would bestow.
         Memory suffers, too, but in a different way from degenerative conditions like Alzheimer’s.The memories are there, but with executive function malfunctioning, the brain neither chooses theimportant things to store nor retrieves that information efficiently. Most people with brain fog arenot so severely affected, and gradually improve with time. But even when people recover enough towork, they can struggle with minds that are less nimble than before. “I’ve had surgeons who can’tgo back to surgery, because they need their executive function,” said Monica Verduzco-Gutierrez, arehabilitation specialist at UT Health San Antonio.
         In early 2022, a team of British researchers rendered the invisible nature of brain fog in thestark black-and-white imagery of MRI scans. They analyzed data from the UK Biobank study,which had regularly scanned the brains of hundreds of volunteers for years prior to the pandemic.When some of those volunteers caught COVID, the team could compare their scans before and afterCOVID. They found that even mild infections can slightly shrink the brain and reduce the thicknessof its neuron-rich gray matter. At their worst, these changes were comparable to a decade of aging.They were especially pronounced in areas such as the parahippocampal gyrus, which is importantfor encoding and retrieving memories, and the orbitofrontal cortex, which is important for executivefunction. They were still apparent in people who hadn’t been hospitalized. And they wereaccompanied by cognitive problems.
【題組】45. According to the passage, which of the following statements is true?
(A) Some patients reported the symptom of brain fog three months after their initial infection ofCOVID.
(B) Brain fog will only affect patients with severe conditions who need a ventilator.
(C) Brain fog only affects older people who need hospital care.
(D) Brain fog is one of the most benign symptoms of COVID by far.