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 -

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

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)

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

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

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

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

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

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