Postural control

Balancing sensory inputs: Sensory reweighting of vision and ankle proprioception during a bipedal posture task

Submitted by Rakshatha Kabbaligere
Multisensory integration is driven by a process of sensory reweighting during which each input is assigned a weight depending on the current functional state of a particular sensory system, the task itself and the context in which it is being performed. The primary aim of this study was to determine which of the two inputs between ankle proprioception and vision is upweighed during a postural control task when the two inputs provide conflicting information pertaining to direction of body sway. Achilles tendon vibration and visual flow were used to create sensory conflict, which produced center of pressure (COP) sway in opposite directions when applied independently. The baseline conditions (1) consisted of eyes open quiet stance condition, eyes closed with vibration applied on the Achilles tendons (2) and eyes open with visual flow (3). The experimental condition simultaneously combined vibration and visual flow. COP excursions were recorded in 10 healthy young adults to evaluate the magnitude and direction of sway produced by vibration and/or visual flow. Additionally, lower body joint kinematics were evaluated to understand the multi-segmental strategies and their adaptation to the various sensory manipulations. The results showed that visual flow moderated the extent of backward COP and ankle angular displacement produced when vibration was applied independently. Additionally, visual flow was also found to reduce the extent of predominant hip strategy generated by ankle vibration. The findings show that visual input plays a significant role in maintaining stability and that ankle proprioception is downweighed during conflicts between vision and proprioception. This has important implication for balance training using controlled visual flow in patients with balance disorders and elderly.
Listed In: Biomechanics, Neuroscience, Posturography 




  

          
Auditory Cues on Postural Control in Parkinson's Disease: A Pilot Study 

    
        

      Submitted by Wannipat Buated
    

    
          

        
        

                            

        

          Objective: To evaluate the effect of auditory cues toward postural control in patients with Parkinson's disease (PD).
Background: Auditory cues have been proved to be one of rehabilitation strategies for PD [1]. Most of Parkinson's Disease patients present postural instabilities regarding the severity of the disease [2, 3]. Rhythmic Auditory Stimulation (RAS) has been justified to be a standardized neurological motor therapy (NMTs) in PD, which cue-ing benefits may be associated with the activation of cerebellum-thalamic-cortical circuitry [4]. A potential method to stimulate the putamen that might help regulate PD brain's circuits could be providing music as a rhythmical cue [4]. A distinct manifestation in PD is also the arm swing reduction [5] which limits the capability of maintaining balance. It is rare to explore the static standing balance in Parkinson's Disease. 
Methods: 5 idiopathic PD patients (5 female) aged 72.6 ± 2.51 years, duration of the disease 15 ± 1.22 years (mean ± SD), H&Y 2.5-3 participated in this study. They were recruited from Yawata Medical Center, Ishikawa, Japan in June and November, 2014. The subjects were instructed to stand on the balance platform (Nintendo Wii Fit) and swing arm; Alternation (Alt) and Synchronization (Syn) in 3 scenarios; with no auditory cues (AC), with AC 5% increased and with AC 5 % decreased. The data were analyzed by Wilcoxon Signed Ranks Test and  the dimensional clustering method [6] on MATLAB. 
Results: Tempo at 95% improved area, RMS and Min ML in Alternation, and decreased the path length in rest 2. Tempo at 105% decreased area and RMS in rest 2 statistically significant. A case with H&Y stage 3 showed poorer postural control in both Antero-Posterior (AP) and Medio-Lateral (ML) directions. Most cases presented the higher Center of Pressure (CoP) displacement in ML direction. AC with arm swing regulated the pattern of CoP trajectories. 
Conclusions: Auditory cues with arm swing - Alternation improved postural control in the PD patients. This concept might be considered clinically to be a rehabilitation program for Parkinson's disease (PD) to improve standing balance. It is a need to enlarge the sample size and develop more rehabilitation programs for improving balance in PD.    


          Listed In: Physical Therapy, Posturography