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6.0 Critical Events During Movement Time (MT): The Effect of
Feedback
Feedback defined Making a reflex movement - spinal cord
pattern generators Feedback during voluntary movements
Open loop control (without feedback) Closed loop control (with
feedback) M1, M2, M3 feedback
Case Studies Rob Summers paralyzed at C7/T1 Epidural stimulation
- Why is he able to
stand and make a voluntary movement? Phantom limb/neural
plasticity/mirror box
Outline
Important Terms Feedback defined - Two (2) types
Intrinsic - Extrinsic -
Reflex actions are Use of feedback is
Voluntary actions - 2 types of motor control Closed loop control
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Open loop control -
Motor program control 3
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MT is lkess than approx. 200 ms use of feedbacjk is not
possible
feedback that arises externally from an external source eg.
coach, video, observation of outcome (hit vs miss)
Reflex actions are programmed into the spinal cord and function
automatically at the spinal level in loops use of feedback not
possible
feedback that arises internall from the production of
movement
MT is longer than approx. 200 ms; feedback can be used to modify
the ongoing action
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Reflex Actions
Reflex Action - Lower Limb (Carter p. 116) Reflexes are
Steps In A Reflex MovementExample: Touching a hot surface
1. Hot surface - sensors in finger send signal along sensory
neuron to the dorsal root of spinal cord
2. Forms a reflex arc via interneuron (within the spinal
column)
3. Exits through the ventral motor route
4.
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programmed into the spinal cord
brain and higher level of feedback not involved
fast, automatic loops
30-50s
m1 loop monosynaptic
protects us from danger
Quickly activates the biceps muscle to flex arm and withdraw the
hand (rapid and subconscious (m1 response))
5. sensory input travels to the brain to somatosensory cortex
and higer centres to produce an awareness (M2 response)
6. motor response as a result of awareness of being burned -eg-
look at finger-not part of reflex instead a voluntary movement (m3
response)
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Voluntary Movements
Making A Voluntary
Action
From Kolb & Whishaw (2011) and Vickers (2007)
Efferent
Afferent
Steps In Making A Voluntary ActionReaching out and picking up a
cup
1. Object Identification: The location of the cup is registered
on the retina
2. Feature integration: Features of the cup travel to the back
of the head along the optic nerve to the occipital cortex where
billions of features are registered (V1-V8)
3. Motor planning: Features race, in parallel, along the dorsal
and ventral routes to the frontal cortex
4. The binding problem: Visual & other information combine
with existing knowledge & create motor commands
5.
(Vickers, 2007, p. 24-25)
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motor execution: efferent motor commands to pick up the cup foes
to the motor cortex and the reaching action is initiated
6. efference copy stored: a cop of the intended action goes to
the limbic , basal ganglia, cerebellum
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Efference Copy Demonstration(Demo at Evernote
Efference/Reafference)
Efferent Motor Command
FeedbackAfferentSignal
Leaves a copy
Steps In A Voluntary Action (contd)Example: Reaching out and
picking up a cup
7. Nerve Conduction: Efferent motor neurons take commands to the
ventral nerves of spinal cord
8. Grasping action: Motor neurons send grasp signal to the
muscles of the hand and forearm
9. Afferent feedback: Sensory feedback from sensory receptors in
the fingers exit via dorsal root and back to the brain
10.Efference copy update:
Ventral (Motor) and Dorsal (Sensory) Fibers
3) Afferent sensory
feedbacksignals from muscles to
brain
2) Efferent motor
signals to muscles
1) Efferent motor commands descend
Sensory ganglion root
Spinal cord has both grey and white
matter
Minenges of spinal
cord similar to the brain
1) Afferent sensory feedback ascends
Ventral
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the limbic basal ganglia and cerebellum judges grasp forces
& corrects movement errors
1. somatosensory cortex receives the signals from basal ganglia/
cerebellum that the cup has been grasped, steps 1 to 12 occur in
one RT
12. Additional voluntary motor commands sent and feedback
received in the same way- a continuous motor control loops
closed loop control
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M1, M2 & M3 Feedback
Carter - First & Second Order Touch NeuronsM1 loop and M2
loops
1) First order (M1) neurons
2) Second order (M2) neurons
Propriocep(ve Pathways
M2 & TR - BlueUnconscious pathway (spino-cerebellar) to the
cerebellum - very rapid
Red - M3Conscious pathway through the thalamus to the parietal
cortex and somatosensory cortex
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first order (m1) neurons carry trouch signals from skin to
spinal cord dorsal root
2) second order (m2) neurons travel up the spinal cord along
ascending anterior spinothalamic track
location of critical aspects of motor programs
somatosensory area is center of touch and feeling
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Third Order Neurons (M3) Thalamus to Somatosensory Cortex
Third order neurons ascend from
Somatosensory CortexMirrors motor cortex
Motor Cortex
Somato-sensoryCortex
Somatosensory Cortex Located between parietal
and motor cortex Receives and processes
sensory information from touch, temperature, proprioception
(body position), and pain.
The sensory receptors are located in the skin, skeletal muscles,
bones and joints
Communicates with
Temporal Lobe
Orbitalfrontalcortex
Dorso-lateral prefrontal cortex
Supplementarymotor cortex
Pre-Motor Area &Mirror Neuron System
Motor Cortex
Temporal - Parietal Junction
ParietalCortex
VisualCortex
SomatosensoryCortex
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thalamus to the somatosensory cortex and all other cortical
areas of the brain
the mirror neuron system in terms of sensing movement and
emotion in self and others
passes sensory feedback to motor cortex prior to initiation of
the movement
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Case Study: Rob Summers Rob Summers - Age 23 paralyzed after hit
and run
accident (Injury at C7/T1)
Almost complete loss of voluntary motor function - could move a
finger
"B" rating on the American Spinal Injury Association's
classification system.
Usually A and B rated patients are told they will never stand or
walk again
Received epidural stimulation 2 years after paralysis; treatment
for over a year
Epidural stimulation procedure
http://www.christopherreeve.org/site/c.ddJFKRNoFiG/b.5848659/k.5E06/Reeve_Foundation_Videos.htm?
12 Pairs cranial nerves
(do not connect directly to the spinal cord but to brainstem
31 pairs spinal nerves
connect to the spinal cord
Location of Rob
Summers break C7/T1
Epidural Spinal Stimulationelectrically enabled motor control
16-electrode array was surgically implanted on the dura (L1-S1)
cord segments to permit long-term electrical stimulation
Activated all spinal nerves that controlled the hip, legs and
feet
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Rob Summers Results of Epidural Stimulation
http://www.youtube.com/watch?v=nkeye0qcZ9A 4 min restored - some
functions described -
Why Epidural Stimulation WorkedPossible Reasons
1. Rob still had surviving descending efferent motor nerves -
ie, spine may not have been completely severed
2. Rob sensory nerves (afferent nerves) below the injury were
still intact. Ascending feedback processes intact.
3. Sensory and motor neurons also contain autonomic nervous
system functions
4. Task-specific training with epidural stimulation might
promote plasticity in surviving efferent and afferent fibres.
5. Reorganization in the brain may create new descending and
ascending pathways that allows for new voluntary movements -
neurogenesis & synaptogenesis occurred with stimulation and
training
Neural PlasticityBrain plasticity, cortical plasticity -
brain
changes the structure, function and organization of neurons in
the brain in response to new experiences
Refers to 2 processes: Synaptogenesis - the strengthening or
weakening of
existing nerve connections
Neurogenesis - adding new nerve cells (neurogenesis)During
neural plasticity
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can stand and make voluntary movements when stimulator is
on.
increased sensation in entire body when stimulator is off
overall blood circulation had improved skin/cleared up
regained ability to sweat/hot and cold sensation
improved lung function
can talk normally
restored bladder and bowl function
restored sexual function
cranial vagus nerve is a miced nerve close to the spinal
nerve
strengthens existing connections and or repairs damaged parts
ofr the nervous system
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Ramanchandran (DVD)
Phantom Limb& Neural Plasticity
Phantom Limb Syndrome (p. 102 Carter)
No sensory input from the missing limb; input from adjacent part
of somatosensory takes over and reshapes the sensory map
Ramachandron Discovered Treatment for Phantom Limb: The Mirror
Box
Using a mirror box, reverses the sensation the missing limb is
still there
Amputated limb placed in one side of box and normal limb on
other side
Therapist David Butler -
http://www.youtube.com/watch?v=hMBA15Hu35M
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patient looks at mirror image of normal hand and cognitively
processes the amputated hand
visual input of mirrored hand changes somatosensory cortex &
motor program to acceptance of amputated limb
effective in treating