ME/CFS and the thalamus as a precision gate: what reversible thalamocortical connectivity reveals about central gain...

Kim and colleagues report a finding that is easy to understate: thalamic hyperconnectivity with sensorimotor and visuo-occipital cortices, present in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) at baseline, shifts back toward the pattern seen in healthy controls after hyperbaric oxygen therapy and does so most in the patients who improve clinically. To my knowledge, this is the first treatment-coupled, apparently reversible thalamocortical signature in ME/CFS. Viewed through predictive processing (the framework in which the brain continually predicts its own sensory and bodily inputs), the thalamus is theorised to be a gain-control gate that helps set the precision or weight assigned to ascending bodily signals. I argue that the baseline hyperconnectivity reflects deficient filtering of expected input, and that its post-treatment reduction may index restored filtering. The same failure of attenuation offers a parsimonious account of several symptoms that often co-occur in patients, including sensory hypersensitivity, pain, orthostatic intolerance, and cognitive "brain fog", as one mechanism expressed across exteroceptive, nociceptive, autonomic, and cognitive domains. Because hyperbaric oxygen therapy is a vascular intervention and resting-state connectivity is an indirect measure this gain interpretation remains a hypothesis and I outline how it can be tested across exertion and post-exertional malaise rather than at baseline alone.