Publikationen – TEST

The GIST

• BOLD MRIs measure blood oxygen levels (energy production) across the brain and what could be more telling than that? Our brains are never always turned on – that would take too much energy. Instead, when a part of the brain is needed – say, during cognitive activity – the mitochondria in that part of the brain take up more oxygen in the blood.
• In a process called “neurovascular coupling” our brains quickly and efficiently transport blood to the active region. How well they can do this not only determines how well tasks are carried out but also plays an important role in the “energy economics” of the brain. Sluggish blood flows result in the brain working overhard to carry out tasks resulting in fatigue.
• This study gave ME/CFS patients and healthy controls two cognitive tests and assessed which parts of the brain reacted; i.e. which became more active. They wanted to see, if, as past studies have found, people with ME/CFS need to use more of their brains to complete the task  – and to see if their brains adapted to the task.
• It turns out that when healthy people do the same task twice their brains use less energy the second time around – they’ve adapted to the task.
• The study found partial evidence that people with ME/CFS used more of their brains than healthy controls to complete the task. The major finding, though, was that their brains did not adapt – in what seemed to signal that postexertional malaise was present – their brains used more energy not less to complete the second task.  Somehow doing the task the first time around had made things worse.
• The authors proposed an inadequate activation of a calcium signaling pathway that increases blood flows to distinct parts of the brain was present and noted that several Australian studies have found problems with calcium mobilization in TRPM3 ion channels in natural killer cells in ME/CFS.
• They didn’t mention it but the finding also appears to fit well with Wirth and Scheibenbogen’s hypothesis regarding calcium mobilization problems in the mitochondria and blood vessels. They believe that the inability of the Na+/K+-ATPase enzyme to remove sodium from ME/CFS cells causes the sodium-calcium exchanger (NCX) to import, rather than remove, calcium from the cells. The calcium buildup that results then impacts mitochondrial functioning and the blood vessels.
• Wirth and Lohn recently proposed that dysfunctional TRPM3 ion channels are wreaking havoc not just in immune cells but in cells across the body. They believe further investigations of this ion channel are “crucial” to understanding ME/CFS. (A blog is coming up.)
• The authors of the present study did not mention energy production. One wonders, though, if the exertion of the first cognitive test might have dampened energy production in the same way that physical exertion does.
• If the authors are correct then cognitive stress at least temporarily impairs the ability of the brain to speed resources (in the form of oxygen in the blood) to parts of the brain that need it – producing fatigue. (That sounds like postexertional malaise of the brain to me.) This group has been engaged in a large study (n=288 (!)) examining neurovascular coupling in ME/CFS from different angles.We should learn much more about that soon.