Baroreceptor stimulation induces cortical inhibition. With blood not drawn by gravity from the upper to lower body, adopting a less upright posture leads to increases in thoracic blood volume and baroreceptor stimulation. Consistent with these effects are observations of cortical activity being inhibited when reclining or tilted head-down. As with less upright postures, in zero gravity there is a redistribution of blood towards the upper body that stimulates baroreceptors. Effects associated with this stimulation could be expected to facilitate an inhibition of cortical activity during zero gravity, as recently reported to occur during parabolic flight (Schneider et al., 2008. What happens to the brain in weightlessness? A first approach by EEG tomography. NeuroImage 42, 1316-1323).