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Sensory Components of Motor Control
Sensory Components of Motor Control
Touch, propriocep6on, vision, and audi6on are important sources of feedback involved in movement control
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Part I: Touch & Motor Control
• Cutaneous System • Development of Cutaneous System
• Hap6c Percep6on • What types of informa6on do we receive from touch?
• Interes6ng facts about touch?
Cutaneous System
Receiving informa6on from sensory mechanical) receptors located on and under our skin. -‐ pressure -‐ coldness -‐ warmth -‐ pain
Some work fast (Meissner’s and Pacinian corpuscles)
Some work slowly (Ruffiniin’s endings and Merkel disks)
Development of Cutaneous System
First system to develop fully in humans.
Early in life, sensi6vity to tac6le s6mula6on is greatest in the parts of body that we use to explore the world. -‐e.g., Mouth, lips, and tongue in an infant
Hap6c Percep6on is developed via cutaneous system
Being ac6ve and play are very important role in development of hap6c percep6on
Hap6c Percep6on
• Hap6c percep6on is the process of recognizing objects through touch. – It some6mes called ac6ve explora6on. – People can rapidly and accurately iden6fy 3-‐dimensional objects by touch.
• There is close link between hap6c percep6on and body movement.
• Related to propriocep6on and percep6on. – Greatest number of mechanical receptors are in our finger6ps
What type of informa6on do we receive from touch?
Tac6le sensory informa6on helps control movement -‐ The receptors in skin provide informa6on when the skin stretches &during joint movement (extension & flexion) -‐Tac6le sensory informa6on is related to movement accuracy, consistency, and force adjustments for on going movements -‐Assists in one’s es6ma6on of movement distance
Interes6ng Facts about Touch
• Tac6le sensi6vity decrease with age due to the quality and quan6ty of Meissner & Pacinian corpuscles. We will decline as much as 30% in our sensory fiber innova6on causing peripheral neuropathy. – Peripheral neuropathy will cause one to rely upon vision and ves6bular (balance).
– Clients with peripheral neuropathy have significant delays in muscle responses when perturba6ons occur, such as being pushed when one is standing.
Part II: Propriocep6on & Motor Control
• Defini6on • Closed and open loop connec6on • Neural basis of propriocep6on • Types of Proprioceptors • Inves6ga6ng propriocep6on • Role of propriocep6on
Propriocep6on and Motor Control
A\aching meaning (percep6on) to our sensa6ons from our limb, body, and head movements and posi6ons.
Commonly overlooked because vision seems to dominate but provides sensory informa6on about speed, direc6on, loca6on in space of the movement.
Closed and Open Loop Connec6on
Movements where feedback can be used (closed loop control), propriocep6ve feedback plays a significant role in controlling movement.
Movement where feedback is available but cannot be used (open loop control), propriocep6on plays a limited role to control fast, ballis6c movements.
Neural Basis of Propriocep6on
We receive informa6on from afferent neural pathways of CNS that begin in proprioceptors located in our muscles, tendons, ligaments, and joints.
These specialized mechanoreceptors provides us with uninterrupted knowledge about the posi6on of body parts rela6ve to each other and our general body orienta6on in space.
Types of Proprioceptors
Muscles spindles
Golgi-‐tendon organs (GTO)
Joint receptors
Muscle Spindles
A\ached within the fibers of most skeletal muscles
Considered to be the most important mechanoreceptor.
Detects changes in muscle length and velocity of the muscles essen*al to being aware of limb posi*on and movement.
Muscle Spindle fibers are responsible for Rapid Limb Posi6on Correc6on
(A)The muscle spindle is innervated.
(B)A sudden increase in load lengthens the extrafusal muscle and results in muscle spindle firing and transmission of sensory impulses to the spinal cord.
(C)Impluses are sent back to the muscle and causes it to contract and elbow joint returns to original posi6on.
A B C
Golgi Tendon Organ
Posi6oned at the distal and proximal inser6on of skeletal muscle.
Primarily responsible for signaling muscle tension and force of contrac*on.
Fires very quickly and is a protec6ve mechanism
Poor detector of changes in muscle length.
Joint Receptors
Joint capsules and ligaments of all synovial joints are supplied with proprioceptors.
Joint receptors is a collec6ve term because not all joints contain the same type of proprioceptors
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They func6on as a limit detectors that signal extreme joint posi6ons and as a protec6ve mechanism.
INVESTIGATING PROPRIOCEPTION
• Surgical deafferenta6on
• Sensory polyneuropathy pa6ents
• Nerve block technique (Temporary deafferenta6on)
• Tendon Vibra6on technique
ROLE OF PRIOPRIOCEPTION
• Affects movement accuracy • Propriocep6ve feedback influences the 6ming of the onset of motor commands.
• Affects coordina6on of body and limb segments used in the movement – Spa6al-‐temporal coupling between limbs & limb segments (difficulty in replica6on of movements)
– Postural control (swaying and balance) – Ability to adapt to movement situa6ons (use a skill in different or new situa6ons)
Part III: Vision & Motor Control
• Neurophysiology of vision • Neural components of vision • Vision development • Common visual errors • Visual Traits • DVA & Motor Performance • Tracking a visual object • Effects of Aging on Visual Acuity • Changes in Vision • Diabetes & Vision • Binocular & Depth of Vision • Field of Vision • Eye dominance • Coincidence An6cipa6on
Vision
People will use vision to subs6tute for touch and/or propriocep6on when they begin to learn a skill that requires them to rely on touch and/or propriocep6on for successful performance. – E.g keyboarding – E.g.dribbling a ball – E.g.doing a flip in gymnas6cs
Moving Room Experiments
• Lee & Aronson (1974) – Par6cipants stood in a room in which the walls moved toward and away from them but floor did not move.
– Situa6on created a conflict between with two sensory systems?
– When the walls moved, people adjusted their posture tough they weren’t moving off balance. Why?
The Neurophysiology of Vision
• Basic Anatomy – Cornea – Pupil – Iris – Lens – Sclera – Aqueous humor
– Vitreous humor
Neural Components of Vision
• Neural Components – Re6na
• Fovea centralis • Op6c disk
– Rods – Cones
Neural Components of Vision
• Neural Components – Op6c Nerve – Op6c Chiasm
– Visual Field • Nasal part • Temporal part
– Visual cortex
Visual Development Each eye achieves most of it grow prior to birth.
At birth the child is hyperopic; light entering the eye focuses behind the re6na (near sighted).
Eye’s cornea ( grows from 2mm at birth to 12 mm at adulthood.
Re6na (composed of rod and cones) is well developed at birth. -‐Rods make colorless night vision possible -‐Cones make color vision and acuity possible
Macula (that part of the re6na where most of the cones cells are located) is mature around 8 months of life.
Ciliary muscles that control the eye and dilator muscles that control the pupil become func6onal at around 6 months of life.
Visual Traits Visual Acuity:
-‐ degree of detail that one can see -‐ Common way of measuring visual acuity is through sta6c visual acuity tests -‐ Certain visual acui6es have special significance. Some of these are: •20/20 vision is considered normal vision •20/40 vision in at least one eye is required to pass the driving test •20/200 vision or worse is the legal defini6on of blindness -‐ Sta6c visual acuity improves the first 4-‐5 years of life. -‐ First 4-‐5 years of life, vision is of a very low quality but enough for many common tasks.
Visual Abili6es
Dynamic Visual Acuity 1. Ability to see detail in a moving object. 2. Ability of CNS to es6mate the object’s direc6on and
velocity and the ability to catch or hold the object on re6na long enough to detect the object’s detail.
3. Improves from 6-‐20 years of age. 4. Most significant period of 6me of development
seems to be between 5-‐12 years of age. 5. DVA declines amer the age of 25.
DVA Apparatus
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Tradi6onal DVA Assessment
Change the size with a given speed
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Alterna6ve Method
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Size is constant but you increase or decrease the speed
DVA & Motor Performance
DVA is related to: Basketball field-‐goal shoo6ng (Beals, et al, 1971; Morris & Kreighbaum, 1977) Ball-‐catching ability (Sanderson & Whi6ng, 1974 & 78) An exercise warm-‐up at low to moderate level of intensity improves one DVA (Millslagle & Cardwell, 2006).
Visual Tracking of Moving Object Visually retaining the object on forea of the re6na during flight.
Two eye movement: -‐ Tracking slow moving objects we use smooth pursuit (matching speed of the object with eye movement speed) where the performer a\empts to retain the image on the re6na by moving there eyes and head. -‐ Tracking fast moving objects we use saccadic eye movement (detects and corrects differences between the objects loca6on and eye fixa6on on the object) there is li\le head or eye movement.
Infant is not capable of tracking any moving object with their eyes.
By 5 or 6, children can track moving objects only in a horizontal plane.
By 8 or 9, boy or girls can track moving objects such as a balls that travel in a arc.
Binocular & Depth of Vision At birth both eyes operate independently (strab-‐ismus) but diminished by the
3rd month.
Coordinated eye movement, that is, the eyes move in unison is called binocular vision.
Macular images of eyes do not match; disparity between the macular is the primary cue for judging depth.
Depth percep6on usually matures by the age of 6.
Field of Vision
Lateral and ver6cal peripheral vision Lateral peripheral vision is 90 degree (one eye) or 180 degrees
(both eyes) when looking straight ahead. Ver6cal peripheral vision is 47 degrees above and 65 degrees
below when looking straight ahead. The purpose of peripheral vision is to detect mo6on or
movement. Child’s peripheral vision is very limited. Peripheral vision declines gradually declines amer the age of 35
un6l 60 years of age. Amer 60, changes are more rapid. Rapid changes amer 60 are related facial changes that reduce the
size of visual field (It’s 6me for a face lim!)
Eye Dominance
The ability of one eye to lead the other in tasks involving visual tracking and visual fixa6on.
Unilateral dominance are people who are right-‐handed (lem-‐handed) and right-‐eye (lem-‐eye) dominate.
Crossed-‐laterals are people who are right-‐handed (lem-‐handed) and lem-‐eye (right-‐eye) dominate.
Unilateral dominant people seem to be be\er at wider variety of tasks than crossed-‐lateral people.
The best baseball hi\ers are cross-‐lateral people. Most professional baseball players are cross-‐lateral.
Coincidence An6cipa6on Timing
CAT is usually measured with Bassin an6cipa6on 6mer.
Involves tracking an object to a target area then makes a coincident response with the arrival of the object.
Underlying ability to catching, hiqng, and most recep6ve sports (e.g., baseball, tennis, somball, soccer, football, etc)
Dynamic visual acuity is lowly related to coincidence
Many factors affect CAT: • Age • Speed • Viewing 6me • Gender • Age
CAT
Point of Gaze • An eye fixa6on is where the gaze is held on an object or
loca6on within 3 degrees of visual angle for 100 ms or longer. 100ms threshold is the minimum amount 6me needed to recognize or become aware of a s6muli.
• Pursuit tracking occurs when the gaze follows a moving object.
• Saccades occur when the eyes move quickly from one fixated or tracked loca6on to another. We must move our eyes rapidly from one fixed loca6on or object to another. During saccades informa6on is suppressed. We do not perceive a blur as our eye moves nor are we able to see a new objects that appears during a saccade but we do process an object.
• Blinking occurs when the eyelid covers the eye. Blinking is necessary to refresh the cornea and lens to maintain vision. During blinking informa6on is also suppressed.
• Point of gaze is where central vision is fixated at any par6cular moment.
• Eye movement typically initates 70ms before we move the hands to a loca6on.
• Eyes are on the loca6on along 6me before the hands arrive at the target.
Visual Pathways 1. Informa6on is registered on the
eyes re6na 2. Informa6on travels along op6c
nerve 3. Informa6on registered on visual
cortex 4. Once registered, informa6on in
parallel is send to the parietal cortex (dorsal) and along the sides (ventral areas).
5. Once it reaches the frontal lobe it integrates with goals, planned ac6on, and formulates a specific ac6on.
6. Informa6on flow to premotor and primary motor cortex
7. Informa6on is send from the brain to muscles
Vision & Motor Control
• Based on neurophysiological evidence central and perpheral vision operate in parallel.
• Central vision (foveal vision) detects: – 2 to 5 degrees of visual field) – Sta6c objects which are slow moving, responsible for recognizing object presences
• Peripheral vision detects: – Objects and High-‐speed movement around us, provides limb movement direc6on, and perceptually guides movements
Central and Peripheral Role of Vision in Locomo6on & Prehension Skills
Central vision keeps us along the pathway.
Peripheral vision detects visual cues in environment (eg. Bumps in the path, obstacles, other people) by assessing op6cal flow pa\erns (light-‐object reflec6on)
Op6cal flow is the rays of light that strike the re6na of the eye from all parts of the environment.
Op6cal flow is important because it enable use to move through an environment and helps us to achieve ac6on goals)
Role of central & peripheral vision related to prehension tasks.
• Peripheral vision seems to affect the transport phase (reaching for the object) but not the grasp.
• Central vision provides informa6on specific to the object. – But if you block central vision the transport and grasp phases will be affected.
Ways we measure how vision controls movement
• Eye recordings
• Temporal Occlusion
• Event Occlusion
Eye Recorders
VIA
VIA
Temporal Occlusion
Amount of 6me a person requires for visual search. Experimenter determines the 6me period of interest as they relate to the skill performed. Experimenter stops as a predetermined 6me point during the ac6on. Athlete, student, or client makes a response as quickly as possible.
Se\er is seqng to?????
Event Occlusion Used to iden6fy the
specific informa6on a person uses to make the required response.
Parts of the movement are masked so that the observer cannot see selected parts.
If a person performs worse without seeing the part the movement, then the part is a important visual cue used to perform the movement.
VISION ISSUES
1) How do the eyes and hands work together when performing a task?
2) Is their a minimum amount of 6me needed to make a correc6on when hiqng the target or during grasphing?
3) Should I use one eye or both eyes?
4) What type of informa6on is being used to perform ballis6c skills?
How to the eyes and hands work together?
• Vision precedes and guides the hand before it moves to the target and is needed to make movement correc6ons at the end of the movement.
• Point of gaze is measured during eye fixa6on and then calculated to determine the 6ming/loca6on of the hand movement.
– Point of gaze occurs 70 ms before the hand begins to move from their star6ng posi6on.
– Point of gaze arrives at the target 450 ms before the hands arrive so movement correc6ons can occur.
IS THEIR A MINIMUM AMOUNT OF TIME NEEDED TO MAKE A CORRECTION?
Lights on and light off technique is usually used to determine the 6me of correc6on.
– Best es6mate is we need at least 100 to 160 msec of visual informa6on for simple manual correc6ons.
– This issue become apparent when we use visual feedback to correct our movement such as in catching a ball or hiqng a ball.
• If ball speed is too fast or distance the ball travels is too short then movement correc6ons is dependent on ini6al hand posi6on.
Should I use one eye or both eyes?
• Monocular versus binocular vision – Motor control system operates more effec6vely and efficiently when it receives informa6on from both eyes.
– Accuracy and efficiency of movements decrease as the distance to the object increases.
– Monocular vision causes one to underes6ma6ng distance to the object (e.g. shoo6ng with one eye open in hun6ng).
What type of informa6on is being used? • Op*cal variable tau is Time to contact or distance based informa6on
• Tau is amount of 6me remaining un6l the object contacts the person(or vice versa) from a specific distance.
• Tau is predic6ve func6on which allows ac6on ini6a6on and object contact to occur automa*cally at a specific 6me to contact regardless of the speed of the object and person.
– E.g. breaking to avoid hi=ng a car……process *me needed by visual informa*on to brake rather than knowledge of how much distance there is between you and oncoming car.
Part IV: Audi6on, Balance, & Motor Control
Prenatal hearing occurs during the last few months of pregnancy. At birth, the newborn can hear. Auditory development during the first 3 months of life is related to the voice
of parents. Usually, associate with the parent that provides food and comfort. At 4-‐7 months, toddler can recognize tone of the voice which cri6cal for
language development. At 7 months toddler recognize their name and first a\empt of speech occur. At 8-‐12 months, toddler produces recognizable sounds. 1-‐2 years of age, infant recognizes and respond to commands. If any of these above milestones are not demonstrated….hearing impairments
may exist. If hearing impairments are not recognized they will effect language and
speech….
Auditory System
Outer ear Middle ear Inner Ear
Outer Ear
The part that we can see (Pinna).
Protects the tympanic membrane (eardrum) and collects and directs the sound waves through the ear canal.
Middle Ear Mostly filled with air carved through
bone.
The auditory canal connect to the tympanic membrane (eardrum) and eustachian tube.
Eardrum is part of the middle ear.
Eardrum is linked to three moveable bones. -The moveable bones are called ossicles (oss-icles). - The ossicles convert sound waves into mechanical vibrations.
- The occ-icles bones are named by their shape: hammer (malleus) then anvil (incus), and the stirrup (stapes).
Inner Ear • Inner ear is a mess.
• Why because it it like a complex maze of fluid-filled tubes running to temporal bones of the skull.
• The cochlea is snail shaped and responsible for hearing.
• The semicircular canals help maintain balance. Interconnections of the semicircular canals and cochlea called the vestibule contains the sense organs of utricle and saccule which is also responsible for balance.
How do we hear? (Professor’s Opinion)
• Sound waves funnel down through the ear canal and strike the eardrum, causing it to vibrate.
• The vibra6ons are passed to the small bones of the middle ear (ossicles), which form a system of interlinked mechanical levers (hammer, anvil, and s6rrup). Hammer pushes anvil; anvil then pushes the Staple. The staple rocks in and out against the oval window. The vibra6on of oval window then at this point becomes a fluid borne.
• Vibra6ons of the fluid in the inner ear cause hair cells in the cochlear to move. The movement of these hairs are converted to nerve impulses.
• These nerve impluses travel down the auditory nerve (cochlear nerve) to the brain to be processed and interpreted (sound percep6on).
How do we keep our balance?
• The semicircular and ves6bule func6on to sense movement (accelera6on and decelera6on) and sta6c posi6on.
• Three semicircular canals lie perpendicular to each other, one to sense movement in each of 3 spa6al planes (frontal, sagi\al, transverse).
• Sta6c head posi6on is sensed by the ves6bule (utricle & saccule).
• Different head posi6ons produce different gravity effects on the hair cells. • Movement of body causes these hair cells to move.
• The hair cells posi6on and movement create nerve impulses.
• Nerve impulses are carried via the ves6bular nerve to the brain stem, cerebellum, and spinal cord.
• It is not a good system (slow). No direct connec6on like vision to the cortex. Instead body and head posi6on produces a reflex ac6on to produce correc6ve response to trigger legs or arms to catch one’s balance.
The End
• Hope you enjoyed the presenta6on about the contribu6ons the sensory systems play to control voluntary movement.
• I know you did….
