Balance and Posture in Adults With Cerebral Palsy

• Center of Mass and Center of Pressure [ Time Frame: 4 hours ] [ Designated as safety issue: No ]
  The investigators will measure the movement of the subject's center of mass and center of pressure using a force platform while they are looking at different visual scenes and with slow force plate movements.
  
  

• Muscle activity [ Time Frame: 4 hours ] [ Designated as safety issue: No ]
  Muscle activity (recording using surface electrodes) will be performed while subjects are looking at different visual scenes and with slow force plate movements.
  
  
• Movement of the legs and trunk [ Time Frame: 4 hours ] [ Designated as safety issue: No ]
  Movement of the knee, ankle, hip and trunk (recorded using surface mounted markers) will be performed while subjects are looking at different visual scenes and with slow force plate movements.
  
  
• Visual dependence [ Time Frame: 1 hour ] [ Designated as safety issue: No ]
  Subjects will be seated ina chair, and asked to align a rotating rod to a vertical or horizontal position while receivng conflicting visual information ( a box placed around the rod in an off-center position)
  
  

Individuals with Cerebral Palsy (CP) present with considerable functional heterogeneity, and demonstrate a marked decrease in functional status with age due to the development of disturbances in somatosensory function, secondary neuromuscular impairments, and poor control over the trunk muscles. These factors promote balance instability, result in an increased fall risk, and contribute to lost functional capabilities. Little is known about the progression of neuromotor and somatosensory impairments as individuals with CP age, thus a knowledge gap exists concerning postural control and balance in the adult with CP, particularly which those associated with aging (primary) and those associated with compensatory behaviors. The objective of this proposal is to explore mechanisms behind abnormal motor response in postural control in the adult with CP. We HYPOTHESIZE that somatosensory reliance, as well as muscle passive and active properties, change with aging and functional adaptation. In order to address our central hypothesis, we propose the following specific aims: SPECIFIC AIM 1: To examine the central disturbances of sensory processing and sensorimotor integration that contribute to abnormal postural control in young adults with CP. We will: a) determine the effect of visual dependence on postural control in the adult with CP as directly measured with a test for visual dependence; and b)relate the presence of visual dependence to the effect of disturbances of the visual flow field on the center of mass (CoM) and center of pressure (CoP) responses in the adult with CP; and c) determine the relationship between central disturbances of sensory processing and sensorimotor integration on functional balance as measured by standardized clinical assessments of balance and fall risk. SPECIFIC AIM 2: To examine the peripheral alterations in passive muscle-tendon properties that could contribute to abnormal postural control in young adults with CP. We will determine the effects of a disturbance of the base of support, a disturbance to the visual flow field, and a combined disturbance of the two on joint kinematics,CoP, and CoM responses in the adult with CP using functional principal component (time-series) analyses. SPECIFIC AIM 3: To examine the impaired muscle activation and loss of selectivity over muscle control that contributes to abnormal postural control in young adults with CP. We will determine the effects of a disturbance of the base of support, a disturbance to the visual flow field, and a combined disturbance of the two on the surface electromyographic (sEMG) activity of lower limb and trunk muscles using wavelet analyses. At the conclusion of this study, we will have characterized postural control strategies employed by adults with CP in the presence of somatosensory and biomechanical perturbations. The combination of our innovative methodology to challenge all aspects of the sensorimotor system, with our analytical approach of both time series and wavelet analysis of the data, will allow us to separate the primary dynamic postural deficits from compensatory actions, a critical distinction for optimizing treatment interventions.