Images from the brains of those patients were compared with two control groups who had different educational backgrounds. “The first was matched to this population, with at least a college degree, good motor skills, and jobs that require multitasking. The second was a traditional traumatic brain injury control group,” Verma says. The team was not able to build a control group of unaffected government personnel also stationed in Cuba, which is a limitation of the analysis, says Dorina Papageorgiou, a neuroimaging specialist at Baylor College of Medicine. They also didn’t have scans available for patients from before symptoms started, which would have allowed them to have an established baseline for each person and thus pinpoint changes case-by-case.