Exam 3 Week 14/15 ppt 18 & 19 Balance: Sensory Systems & Balance Testing Flashcards
What are the sensory systems that are used in balance?
•Response to perturbation requires the use of multiple sensory systems
- –Vestibular input
- –Somatosensory System - Proprioception
- –Vision
What is ambient vision?
the same as peripheral vision
What type of vision is the most valuable in balance?
–Peripheral (ambient) vision is the most valuable in balance
explain how ambient vision helps with balance? (5)
–Peripheral (ambient) vision most valuable in balance
- –Provides a principle vertical frame of reference
- –This allows us to easily determin the magnitude of deviation of the head and body from that vertical
- –It also Provides a horizontal frame of reference
- –It Integrates information about horizontals and verticals in the context of gravitational forces
- –This combination is important in maintaining balance
Peripheral (ambient) vision most valuable sensation in maintaining balance. Ambient vision Provides a principle vertical frame of reference and can easily determine the magnitude of deviation of the head and body from that vertical. It also provides a Provides a horizontal frame of reference and how fast the person is approaching the horizontal frame of reference.
Ambient Vision integrates information about horizontals and verticals in the context of gravitational forces which is the integration that is important in maintaining balance
In the context of balance the visual system will determine ____________________.
In the context of balance the visual system will determine the amount of total motion.
how does the brain interpret all motion perceived through vision?
what does this mean?
as self motion
–So visual system not good at differentiating exocentric motion (object motion) from egocentric (self motion)
So in the context of balance the visual system will determine the amount of total motion, but the Brain interprets all motion perceived through vision as self motion and the visual system not good at differentiating exocentric motion (object motion) from egocentric (self motion). This is illustrated when you are stopped at a traffic light next to a large bus or truck. If it moves forward you sense that you are moving backward before you realize that you are not.
what is optical flow?
Wikipedia:
Optical flow or optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer (an eye or a camera) and the scene.
describe Ambient (peripheral) vision
•Ambient (peripheral) vision gives information needed in balance
- –As a person moves the optical flow field radiates outward from a distant central point
- –Optic flow is spatially coincident with the direction of motion
- –It arises from a point that is projected the center of the retina where the distant point is perceived
- –At the peripheral edges of the field of view, the optical flow field is nearly parallel to the line of motion and has been termed “lamellar flow” as opposed to “radial flow”
how is optic flow oriented with the motion?
–Optic flow is spatially coincident with the direction of motion
where does optic flow arise from?
–It arises from a point that is projected the center of the retina where the distant point is perceived
Athe center of the field of view, how is the optical flow field oriented?
what is it called
in a radial manner from the center
It is called radial flow
what is lamellar flow?
–At the peripheral edges of the field of view, the optical flow field is nearly parallel to the line of motion and has been termed “lamellar flow” as opposed to “radial flow”
–The moving environment, particularly as detected the the peripheral visual field, can be perceived as movement by __________.
the individual
We are very sensitive to a moving environment. This can be demonstrated by moving the visual surround around the individual
what will happen if our visual sense interprets the moving environment as movement of thd individual?
Postural adjustments will occur as a result of this movement of the surrounding enviroment and this can be Simulated by moving room experiments
If the person stands but the walls of the room are moved around the subject, what will happen to postural sway?
–Increased Postural sway produced
If a room is moved forward around the person, how will the person perceve it and what will happen?
If the room is moved forward, the person will perceive a backward motion and contract muscle to pull themselves forward
If a room is moved backward around the person, how will the person perceve it and what will happen?
Conversely if the room is moved backward, the person will perceive a forward motion and contract muscle to pull themselves backward
•Active movement & vision: Is there a difference in how the environment is perceved when the person is moveing through it actively (walking) vs passively (sitting)?
if so, explain
But if you are actively moving through the environment the situation is viewed differently than moving through in a passive manner (sitting with moving field of reference using video).
So more information is gained when active locomotion is involved
is more information gaind through active locomotion or passive locomotion?
more information is gained when active locomotion is involved
what are two visual things that play a role in balance?
- Visual Acuity
- Depth perception (stereopsis)
what is another word for depth perception?
stereopsis
decreased visual acuity _________ risk of falling
increases
decreased depth perception _________ risk of falling
increases
How does visual contrast sensitivity affect balance?
- §Some preliminary evidence suggests that the ability to distinguish varying brightness against a constant background perhaps plays the greatest role in balance
- §Studies have shown that distant contrast sensitivity and depth perception are independent predictors of increased sway in older people
- §In addition poor contrast sensitivity will have add more risk in ambulation as people with poor contrast detection may have less capacity to detect ground-level hazards
There is Some preliminary evidence suggesting that the ability to distinguish varying levels of brightness against a constant background perhaps plays the greatest role in balance. Studies have shown that distant contrast sensitivity and depth perception are independent predictors of increased sway in older people.
In addition poor contrast sensitivity will have add more risk in ambulation as people with poor contrast detection may have less capacity to detect ground-level hazards
How many types of balance testing are there?
–Wide variety of balance tests & description of each beyond the scope of this presentation
CDP
Computerized Dynamic Posturography
what is Computerized Dynamic Posturography?
A balance testing technique:
- –Computerized Dynamic Posturography (CDP) is a testing system that tests for the specific sensory deficits involved in balance disorders
Computerized Dynamic Posturography includes: (4)
- –Isolation and Quantification of orientation inputs from the visual, vestibular and somatosensory systems
- –Isolation and Quantification of central integrating mechanisms for selecting functionally appropriate orientation sense(s)
- –Isolation and Quantification of functionally appropriate movement strategy(s) in a variety of controlled task conditions
- –Isolation and Quantification of motor output mechanisms for generating timely and effective postural movements
hwo is CDP testing performed? (3)
•In CDP testing
- –Patient stands on a movable, dual forceplate support surface within a moveable surround (enclosure)
- –Under control of a computer, the force platform can either move in a horizontal plane (translate), or rotate out of the horizontal plane (yaw)
- –Standardized test protocols have support surface and visual surround motions, during which the patient’s postural stability and motor reactions are recorded
What are three standardized test protocols for CCDP testing?
–Standardized test protocols include:
- §Sensory Organization Test (SOT)
- §Motor Control Test (MCT)
- §Adaptation Test (ADT)
what is the Sensory Organization Test? (2)
•Sensory Organization Test
- –Objectively identifies problems with postural control by assessing the patient’s ability to make effective use of (or suppress inappropriate) visual, vestibular, and proprioceptive information.
- –Patients stand on a support surface that measures postural sway
Objectively identifies problems with postural control by assessing the patient’s ability to make effective use of (or suppress inappropriate) visual, vestibular, and proprioceptive information.
Patients stand on a support surface that measures postural sway
How doe sthe Sensory Organization Test work? (details; 4)
It Controls sensory information
- –Sensory input from the feet and ankles is effectively eliminated through calibrated “sway referencing” of the support surface
- –Visual sensory input is effectively removed by calibrated “sway referencing” of the support surface with the visual surround
- –The support surface tilt and/or visual surround to directly follow the patient’s anteroposterior body sway, eliminating orientation information
- –Utilizes 6 conditions including with and without ankle tilt, with and without vision and with sway referenced vision (distorted vision)
SOT
Sensory Organization Test
How are the 6 SOT test conditions ordered?
from easiest to hardest
SOT: Explain Condition 1:
–Condition 1
- §Eyes open, fixed surface and visual surround
- §So when platform moves horizontally there is normal vision, vestibular & ankle proprioception feedback
SOT: Explain Condition 2
–Condition 2
- §Eyes closed, fixed surface
- §So when platform moves horizontally there is no visual feedback but normal vestibular & ankle proprioceptive feedback
SOT: Explain Condition 3
–Condition 3
- §Eyes open, fixed surface, sway referenced visual surround
- §So when platform moves horizontally there is abnormal visual feedback but normal vestibular & ankle proprioceptive feedback
SOT: Explain Condition 4
–Condition 4
- §Eyes open, sway referenced surface, fixed visual surround
- §So when platform moves horizontally there is normal vision & vestibular feedback but abnormal ankle proprioceptive feedback
SOT: Explain Condition 5
–Condition 5
- §Eyes closed, sway referenced surface
- §So when platform moves horizontally there is no vision, abnormal ankle proprioception & normal vestibular input
SOT: Explain Condition 6
–Condition 6
- §Eyes open, sway referenced surface and visual surround
- §So when platform moves horizontally there is abnormal vision & proprioceptive ankle feedback & normal vestibular feedback
draw/imagine/write-out the 6 SOT testing conditions
This slide summaries the 6 conditions
draw/imagine/write-out the 6 SOT testing conditions with the sensory issues for each of the six conditons in the test.
Here are the six condition with the sensory issues for each of the six conditions in the test. Again you may wish to stop the video to study these.
SOT Condition 1:
Testing Conditions:
Vision
Proprioception
Sensory Issues
Vision
Proprioception
Vestibular
SOT Condition 1:
Testing Conditions:
Vision: Fixed Surround, Eyes Open
Proprioception: Fixed Surface
Sensory Issues
Vision: normal
Proprioception: normal
Vestibular: normal
SOT Condition 2:
Testing Conditions:
Vision
Proprioception
Sensory Issues
Vision
Proprioception
Vestibular
Testing Conditions:
Vision: Eyes Closed
Proprioception: Fixed Surface
Sensory Issues
Vision: None
Proprioception: Normal
Vestibular’ normal
SOT Condition 3:
Testing Conditions:
Vision:
Proprioception
Sensory Issues
Vision
Proprioception
Vestibular
SOT Condition 3:
Testing Conditions:
Vision: Sway Referenced
Proprioception: Fiixed surface
Sensory Issues
Vision: Abnormal
Proprioception: Normal
Vestibular; Normal
SOT Condition 4:
Testing Conditions:
Vision:
Proprioception
Sensory Issues
Vision
Proprioception
Vestibular
SOT Condition 4:
Testing Conditions:
Vision: Fixed surround, eyes open
Proprioception: sway referenced
Sensory Issues
Vision: Normal
Proprioception: Abnormal
Vestibular: Normal
SOT Condition 5:
Testing Conditions:
Vision:
Proprioception
Sensory Issues
Vision
Proprioception
Vestibular
SOT Condition 5:
Testing Conditions:
Vision: Eyes Closed
Proprioception: Sway Referenced
Sensory Issues
Vision: None
Proprioception: Abnormal
Vestibular: Normal
SOT Condition 6:
Testing Conditions:
Vision:
Proprioception
Sensory Issues
Vision
Proprioception
Vestibular
SOT Condition 6:
Testing Conditions:
Vision: Sway Referenced
Proprioception; Sway Referenced
Sensory Issues
Vision: Abnormal
Proprioception: Abnormal
Vestibular: normal
