Whatever was behind the sonic attacks" experienced by US government personnel in Havana, Cuba, starting in late 2016 remains a mystery - but a new study published Tuesday looks inside the workers' brains for clues. MRI brain scans from 40 patients - 23 men and 17 women - showed variations in brain structure and functional connectivity ... when compared with 48 other adults. "There were group differences all over the brain," said study author Ragini Verma. "Especially in an area called the cerebellum, which is also implicated in the kind of clinical symptoms that most of these patients were demonstrating, which is balance, eye movement, dizziness, etcetera." Differences in connectivity were also observed in the brain's auditory and visuospatial areas. These patterns don't fit a clear picture of a specific disorder. "It certainly does not resemble the imaging presentation of traumatic brain injury or concussion, although they present with clinical symptoms which are concussion-like," Verma said. "The sounds were often associated with pressurelike or vibratory sensory stimuli," according to the study. One patient reported hearing two 10-second pulses, while others said they could hear the sound for more than 30 minutes. State Department and federal investigators have testified that they were unable to determine the source or cause of the ailments in Havana, stating only that they "were most likely related to trauma from a non-natural source."