Neural correlates of vestibular adaptation in cosmonauts after long duration spaceflight

Long-duration spaceflight affects otolith-mediated ocular counter-roll (OCR) and brain function, but the relationship between these changes is unclear. This study examines whether OCR changes correlate with functional connectivity (FC) changes in the vestibular network in the same cosmonauts after a long-duration (6-month) spaceflight mission. Using a human vestibular atlas, we found that changes in FC between the right operculum (OP2_PIVC) and inferior parietal lobule (IPL, area PGp and PGa) were positively correlated with OCR changes. First-time flyers showed a greater decrease in OCR, linked to more significant FC reductions. Irrespective of the OCR, increased FC was observed postflight between the left visual cingulate cortex (CSv) and the anterior cingulate cortex (ACC, area 33), superior parietal lobule (SPL, area 5C), and thalamus (pulvinar), and between the right OP2_PIVC and SPL (area 5Ci). Secondly, decreased FC was observed between the left OP2_PIVC and the IPL (PGp) and SPL (area 7A). Additionally, increased FC postflight was observed between the left lateral sensorimotor area (LSM) and IPL (area PGp), and between the right lateral visual area (LVA) and cerebellum (Crus 1, Lobule VI). These findings suggest sensory reweighting and sensory system reorganization after long-duration spaceflight.