The description of the postural responses in Parkinson's disease patients when visual information changes from a stable to a moving visual field analyzing the impact on balance in these patients. Methods (Clinical):Limits of Stability, Body center of pressure and balance functional reserve were measured by means of the force platform in 24 Parkinson´s patients in stages 1 and 2 of the Boher classification and 19 volunteers as a control group. Both groups were stimulated with 1-Static visual field and 2-horizontal optokinetic stimulation using a virtual reality system. Postural responses were analyzed using the inverted pendulum as mathematical model. Results:While the control group didn't show significant differences on the postural control between the two sensory conditions (COP p=0.0017, BFR p=0.0025), Parkinson's patients presented significant differences in the area of the center of pressure and the balance functional reserve values between static visual field and optokinetic stimulation. (COP p=0.0017, BFR p=0.0025). Conclusions:The results support the hypothesis about the influence of the changes in the visual information in triggering balance control disorders in Parkinson's patients. It is discussed the interest of these fact in the assessment and the rehabilitation programs of this disease. Braz J Otorhinolaryngol. 2011;77(5):651-5. ORIGINAL ARTICLE BJORL

(1) GV in CG was lower in DT than with EN (p = .019). (2) GV was faster in CG with EN compared with the three conditions in CIU (EN, p = .006; DT, p = .0001; CI-OFF, p = .03). (3) CIU had slower GV walking with EN (p = .037) and with DT (p = .022). (4) Dividing the CIU sample by age, the acoustic information generates a slower gait for those implanted after 3 years old.

BVH patients showed higher values of EC of the COP signal measured in arbitrary units compared with the control group (conditions 1 and 2). None of the BVH patients could perform the test in condition 3. BVH patients had increased EC in the frequency band between 0.1 and 0.78 Hz when the visual information was canceled (condition 2).

In this study a simple model of the postural control system is implemented and its parameters are adjusted to explain the differences between Parkinson's disease patient's measures and healthy young adult's measures by performing simulations of spontaneous sway with center-of-pressure traces. An optimization procedure was performed varying four parameters of the model. The best adjustment obtained was when the proportional and derivative factors where the same as for healthy young adults and noise level gain and force feedback gain varied independently. Differences in the latter parameter can be explained because of insufficient and slowed force production necessary to counteract perturbations in Parkinson's disease patients while the former may be due to noise in the sensory system that estimates the vertical deviation angle and/or perturbations in the execution of the movement.

Conclusions The assessment of postural responses (PR) based in a feedback control system model shows selective gains in different bands of frequencies adaptable with child development. Objective PR characterization of pre-lingual cochlear implant users (CIU) in different sensory conditions. Methods Total energy consumption of the body's center of pressure signal (ECCOP) and its distribution in three bands of frequencies: band 1 (0-0.1 Hz), band 2 (0.1-0.7 Hz), and band 3 (0.7-20 Hz) was measured in a sample of 18 CIU (8-16 years old) and in a control group (CG) (8-15 years old). They were assessed in a standing position on a force platform in two sensory conditions: 1 = Eyes open. 2 = Eyes closed and standing on foam. Results In condition 1, total ECCOP of PR and its proportion of energy consumption in the three bands of frequencies were similar between CIU and CG (p > 0.05). In condition 2, CIU have significantly higher ECCOP, mainly in high frequencies (bands 2 and 3) (p < 0.05). ECCOP values decreased with age also, mainly in bands 2 and 3. This behavior is interpreted in the control system model proposed as an adaptation process related with child development.