Lecture 7 Flashcards
what is the Sensory organization test
- use of different combinations of sensory manipulations which allows for assessment of relative contributions of said systems to postural control
Explain how the sensory organization test (SOT) occurs
6 different conditions
* fixed or sway surface
* normal vision, eyes closed, sway references vision
* vestibular information always remains accurate
Common results of the elderly during an SOT
- Have more trouble with posture
- more sway is seen when inaccurate somato and vision
- altered, more unreliable vestibular system
notice how vision deficits have a bigger impact than somato deficits
Vestibular loss subjects during SOT
- Fall when only information to go off of is vestibular, no normal stimulation to go off of
- Joints are naturally more stiff trying to actively minimize sway during quiet stance, therefore less sway is seen compared to normal subjects when no variables are altered
Each sense provides a _____ to postural control
unique contribution
Changes in sway in different sensory conditions depends on?
Changes in sensory “weights”
How much the CNS relies on it
What is gain
- ratio of output/input of a sensory system
- depends on accuracy as reference for body motion
what may require sensory inputs to be re-weighed to maintain balance control
pathology or changes in the environment
A light touch on the back can
help regain balance
seen in Chiba et. al., 2013
used caloric irrigation to alter vestibular input
T/F, CNS instantaneously reweighs sensory conditions
False, CNS needs time to ID and adapt (reweigh) changing sensory conditions
Re weighing time is ____ with the withdrawal compared to addition of a given sensory input?
SHORTER
1s for taking away
1.5-2s for addition
Why do we move when standing still? (theories)
- Compensate for intrinsic instability due to gravity
- compensation for possible sources of perturbation (respiratory movements)
- Increase leg muscle activity to aid pumping blood back to heart (venous pump theory)
- Variation in joint loading, minimize degeneration
- Augment proprioceptive feedback (generate sensory cues)
passive control model
Intrinsic mechanical properties of muslce, tendons, ligaments contribute to passive corrective torques
Who proposed the passive control model
Winter et. al., 1998
* Sway can be controlled passively by setting level of ankle stiffness by increasing tone of plantar and dorsi-flexors
* Comparisons showed delays between COM and COp to be less than 6ms (too short for feedback)
* sensory info used to set original level of stiffness, sway controlled by mechanical properties
How much is passive torque estimated to contribute to total ankle torque during quiet stance?
94-97%
suggests active torque component still neccesary to generate corrective torque to maintain stance
