Experimental Study of Adaptation and Postural Control after Sleep Deprivation

Abstract: This thesis investigates the influence of sleep deprivation on the human's postural control and conceptions of adaptation. Seventeen subjects were investigated with posturography after 24 h and 36 h of sleep deprivation, and a control posturography trial was performed either one week before or one week after the sleep deprivation trials. Stabilizing torques and forces were recorded by a force platform and the body sway was recorded by a 3D ultrasonic positioning system. Stimulation according to a pseudo random binary sequence (PRBS) was applied using two vibrators attached to the calf muscles of the subjects. Posturographic tests were performed with eyes open and eyes closed. Subspace based modeling was used to assess postural control after sleep deprivation. Also, quantitative variance and correlation analysis were applied to the recorded data. The results of the investigation showed that it is possible to identify MIMO models with stimulus as input signal and torques and body sway as output signals. When body sway is characterized by the variance of the position data, statistical evidence was found for an increase of body sway after 24 hours of sleep deprivation. Also, sleep deprivation impairs postural adaptation.