Lecture 7

Question 1

what is the Sensory organization test

Answer 1

• use of different combinations of sensory manipulations which allows for assessment of relative contributions of said systems to postural control

Question 2

Explain how the sensory organization test (SOT) occurs

Answer 2

6 different conditions
* fixed or sway surface
* normal vision, eyes closed, sway references vision
* vestibular information always remains accurate

Question 3

Common results of the elderly during an SOT

Answer 3

• 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

Question 4

Vestibular loss subjects during SOT

Answer 4

• 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

Question 5

Each sense provides a _____ to postural control

Answer 5

unique contribution

Question 6

Changes in sway in different sensory conditions depends on?

Answer 6

Changes in sensory “weights”
How much the CNS relies on it

Question 7

What is gain

Answer 7

• ratio of output/input of a sensory system
• depends on accuracy as reference for body motion

Question 8

what may require sensory inputs to be re-weighed to maintain balance control

Answer 8

pathology or changes in the environment

Question 9

A light touch on the back can

Answer 9

help regain balance
seen in Chiba et. al., 2013
used caloric irrigation to alter vestibular input

Question 10

T/F, CNS instantaneously reweighs sensory conditions

Answer 10

False, CNS needs time to ID and adapt (reweigh) changing sensory conditions

Question 11

Re weighing time is ____ with the withdrawal compared to addition of a given sensory input?

Answer 11

SHORTER
1s for taking away
1.5-2s for addition

Question 12

Why do we move when standing still? (theories)

Answer 12

• 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)

Question 13

passive control model

Answer 13

Intrinsic mechanical properties of muslce, tendons, ligaments contribute to passive corrective torques

Question 14

Who proposed the passive control model

Answer 14

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

Question 15

How much is passive torque estimated to contribute to total ankle torque during quiet stance?

Answer 15

94-97%
suggests active torque component still neccesary to generate corrective torque to maintain stance

Question 16

Which freqencies are seen with active and passive control

Answer 16

• Passive are the low frequency movements
• active are the higher frequency movements