Thank you for putting that IF
Astronauts train by exposing themselves to repetitive provocative stimuli. The classical one is the tilt-while-rotating, which consists in sitting on a rotating chair and perform a series of tilts of the head (e.g. the chair rotates at 60-120°/s, or one turn in 3-6s, wait 20 s then tilt the head forward-backward, with a good amplitude and one movement every 2 to 4s. Btw, be carefull if you try it at home: you may pretty well fall from the chair). This stimulus will create aberrant canal stimulations which are in conflict with gravity signals.
Basically, this training will habituate the brain to ignore canals information Specifically, the brain usually processes vestibular information in two ways: one is to react to the ‘raw’ motion information, the other is to make some additional processing which optimizes the perception of motion. After training, this additional processing will be reduced. In other words, the reflex responses to vestibular sensory signals are maintained (which is good enough for most purposes such as gaze stabilizationand balance), but the ability of the brain to ‘make sense’ out of these signals is reduced. Which is good, because one of the classical causes of motion sickness is aberrant vestibular inputs (which don’t make sense), and schematically, after training the doesn’t care about it.
In practice, the suceptibility to motion sickness can be reduced this way. However, it can never be totally suppressed.