Body sway modulation by hypnotisability and gender during low and high demanding postural conditions.

The cognitive trait of hypnotisability, associated with the proneness to accept suggestions, exhibits several physiological correlates including the modulation of sensorimotor integration and, in particular, of postural control. In this respect, we have shown that, at eyes closure, healthy subjects with high hypnotisability scores (highs) having their feet 2 cm apart show larger and faster body sway with respect to low hypnotizable individuals (lows). The aim of the present study was to investigate whether hypnotisability modulates body sway during slightly more demanding and very difficult postural conditions such as feet together bipedal posture and one legged stance, respectively. Stabilometric variables were studied: the body Centre of Pressure (CoP) Area and mean Velocity, the CoP mean position (Xmean, Ymean) and its variability (SDx, SDy) in the frontal and sagittal planes were acquired in 18 highs (9 females) and 18 lows (9 females). Results showed that the previously observed lows’ smaller and slower body sway was not present any longer. Nonetheless, hypnotisability interacted with gender in the modulation of the variability of the CoP movement in the frontal plane during both the bipedal, feet together posture and one legged stance, as significant gender differences were observed only among lows. In conclusion, results confirm a role of hypnotisability in sensorimotor integration and support the relevance of hypnotic assessment in clinical settings, as hypnotisability may be responsible for part of the postural variability.