The 29th ESA parabolic flight campaign
(Mérignac, Bordeaux - France 10th to 21th March 2002)

a300 ZeroG

It suggests self-selection by less motion susceptible volunteers for zero-g flights. Even in intrinsically less motion sickness susceptible individuals, pharmacological protection is far from 100% complete.
The autonomic nervous system response of motion stimulation and the demonstrated association between reported malaise level support the hypothesis that training individuals by electrophysiological biofeedback is an appropriate approach to the treatment of space motion sickness (P.S Cowings 1990)