Lecture Five: Neural Plasticity and Recover of Function

Question 1

MOTOR CONTROL:

ANATOMICAL PROCESS/STRUCTURES

Answer 1

Task example: Reaching to pick up glass of milk
First
• Sensory inputs come in from periphery for: • Body in space information
• Information related to task: how big is glass, how heavy
• Send info to cortex as sensory map, for motor planning to perform action

Second
From sensory map, make a movement plan (parietal lobes, premotor cortex)
• Plan sent to motor cortex: Muscle groups for action are specified
• Plan also sent to cerebellum and basal ganglia: Modify plan to refine the movement
• Cerebellum sends update of movement output plan to motor cortex and to brainstem
Third
Descending pathways from motor cortex and brainstem activate spinal cord networks→spinal motor neurons activate muscles→ reach for glass of milk
• If glass has more milk than you anticipated: spinal reflex pathways compensate for the difference in weight and activate more motor neurons
• Sensory input is evaluated→cerebellum will update movement pattern

Question 2

Neural Plasticity

Answer 2

• Ability of neurons to change function, chemical profile, or structure
• Both changes in synaptic connections, and structural changes in cortical organizations and number of neural connections
• Neural plasticity occurs
  
  • During development
  • During learning process
  • In response to CNS injury

Question 3

CNS and Learning

Answer 3

• The brain is continuously remodeling its neural circuitry to encode new experiences( learning) and enable behavior change
• For each learning event, there is a change in the nervous system that supports the learning to occur
• Learning modifies( changes) the structure and function of neurons in the brain
• This change is evidence of Neural Plasticity- adaptation of brain and neural system to experiences

Question 4

Plasticity: Changes in neural structure and function during learning

Answer 4

Short term learning vs Long term learning

Initial skill phase vs Autonomic skill phase

Question 5

Short term learning

Answer 5

Intercellular level changes occur in the efficiency of synaptic connection

Question 6

Long term learning

Answer 6

Structural changes occur in the organization and number of neural connection

Question 7

Initial Skill Phase

Answer 7

• Increased attentional demands

- Associated with activity in widely distributed areas of the brain, predominantly cortical areas

Question 8

Autonomic Skill Phase

Answer 8

• Task becomes more automatic or habitual- decreased attentional demands
• Associated with decrease in activity on the primary motor cortex and an increase in subcortical motor regions

Question 9

Intercellular level plasticity

Answer 9

Changes between neurons at the synaptic level

Question 10

Network level plasticiy

Answer 10

Changes in patterns of neural activation and cortical remapping/reorganization

Question 11

Synaptogenesis

Answer 11

The formation of synapses between neuron in the nervous

Question 12

Synaptic Pruning

Answer 12

Process of elimination through apoptosis of synapses that are not strengthened through use

Question 13

Synaptic Plasticity

Answer 13

Changes in the strength of connections between synapses, in response to increases or decrease in their activity

Question 14

Recovery of Function after CNS injury

Answer 14

• Spontaneous recovery: Initial or early , not related to external interventions
• Activity-induced recovery: Improvements related to specific activities and training

Question 15

Recovery of Function- Mechanisms

Answer 15

Restorative( Direct), Compensatory( Indirect)

Question 16

Restorative( Direct)

Answer 16

Resolution of temporary changes in neural tissue, and recovery of injured neural tissue after injury

Question 17

Compensatory (Indirect)

Answer 17

Different neural circuits/structures take over the last or impaired function- Plasticity

• Function enabling plasticity: Changes in neural structure that improve motor function
• Function disabling plasticity : changes in neural structure that reduce motor capabilities or sensation

Question 18

Neural systems initial injury: Intercellular level

Answer 18

• Injuries in central and peripheral nervous systems involve damage to axons
  
  • Axotomy - Injury that divides axon in two
  • Results in loss of synaptic connection
  • Also causes damage to adjacent neurons: presynaptic and postsynaptic
• Initial transient impact after injury
  - Diaschisis: Reduction in blood flow and/or metabolism to structurally intact brain areas that are adjacent to site injury, causing further loss of function- may be reversible
  
  • Cerebral edema: Compresses axon and physiological blocks nerve conduction- reduction of edema typically results in restored function to non damages areas

Question 19

CNS Response to Injury: Mechanisms of Recovery

Answer 19

Unmasking silent synapses
Regenerative synaptogenesis/Neural regeneration
Reactive synaptogenesis/Collateral Sprouting

Question 20

Unmasking silent synapses

Answer 20

Structural synapses that are present but have not contributes to function pre-injury (silent) may be unmasked

Question 21

Regenerative Synaptogenesis/Neural Regeneration

Answer 21

Injured axons begin sprouting to reestablish synaptic connections

Question 22

Reactive Synaptogenesis/Collateral Sprouting

Answer 22

Adjacent ( uninjured) axons sprout to innervate synaptic sites that were previously activated by axons that are injured

Question 23

NEURAL SYSTEM RESPONSE TO INJURY: NEURONAL REGENERATION

Answer 23

Severe damage to axon often leads to death of neuron
• Neurogenesis can occur in humans in hippocampus and olfactory bulb
• New neurons extend axons and dendrites, form synapses, integrated into circuits
• Stem cells are the source of neurons in embryo and in adults

Question 24

RECOVERY OF FUNCTION:

STRUCTURAL LEVEL – CORTICAL REORGANIZATION

Answer 24

• Cortex mapping: Corresponding area of brain in somatosensory and motor cortices related to region of body - Cortex maps are dynamic
• Capable of reorganizing after peripheral or central injury
• Adjacent areas of brain extend to cover damaged areas
• Non-dominant pathways (pre-injury) take over functional connections

Question 25

CORTICAL REMAPPING

Answer 25

Typically: Sensory and motor maps in the brain are constantly changing with the type & amount of activation by peripheral inputs
• Rehabilitation/training can strengthen peripheral input for brain plasticity • Each person’s brain mapping is unique

Question 26

RECOVERY OF FUNCTION:

ACTIVATION OF BRAINSTEM LEVEL PATHWAYS

Answer 26

• In stroke patients – corticospinal lesion was found to result in an increased activation of reticulospinal pathways from the brainstem
• Reticulospinal activation both supports and constrains functional recovery
• Increases recruitment of flexor motor neurons to strengthen arm/hand (supports recovery)
• Also constrains recovery, as the increased flexor activation is not balanced with increased extensor muscle activation
• UE flexor synergy is common pattern seen in individuals after CVA

Question 27

NEURAL PLASTICITY

Answer 27

Synaptic connections and cortical remapping are dependent on use/experience

Question 28

PRINCIPLES OF EXPERIENCE-DEPENDENT NEURAL PLASTICITY

Answer 28

1)Use it or Lose it
2) Use it and Improve it
3) Specificity:
Repetition matters
5) Intensity matters
6) Time matters
7) Salience matters
8) Age Matters
9)Transference
10) Interference

Question 29

Use it or lose it

Answer 29

CNS needs to be actively engaged in tasks or will further degrade after injury

Question 30

Use it or Improve It

Answer 30

Skill training is associated with neural plasticity and improvement in function

Question 31

Specificity

Answer 31

Training needs to be specific to skill being learned

Question 32

Repetition Matters

Answer 32

High reps in practice needed to change neural networks

Question 33

Intensity Matters

Answer 33

Sufficient practice volume is need for neural plasticit

Question 34

Time Matters

Answer 34

There are time windows when training is most effective for making use of neural plasticity. Time of onset of rehab matters- don’t wait. Some interventions maybe more effective at particular times in recovery

Question 35

Salience matters

Answer 35

Training need to be meaningful to the individual for plasticity to occur

Question 36

Age Matters

Answer 36

Experience- dependent plasticity potential reduces with age. However, plasticity can still occur, but may be slower to occur and have decreased effects

Question 37

Transference

Answer 37

Plasticity that occurs from training on skill may enhance acquisition of similar skills

Question 38

Interference

Answer 38

Plasticity from learning one behavior may interfere with learning other behavior/skills

Question 39

Neural plasticity and neurodegenerative disease

Answer 39

Experience- dependent principles apply

• Preventive factors: Activity can delay onset, progression of symptoms by strengthening neural connections
• Prolong function
• Neuroprotective: Activity continues to strengthen pathways with use

Question 40

Other considerations for rehab

Answer 40

Enriched Environment enhances synaptic plasticity and functional recovery ( salience, intensity, opportunities for repetition)
-Importance of aerobic exercise for increase blood flow