DPT 754- Neuroplasticity (pt.2)

In rat studies “skilled reach training” was found to cause what?

Reorganization of cortical movement representation.

Results: Significant inc in wrist and digit representation, but not the elbow and shoulder representation.

In rat studies motor skill was found to develop before what?

Structural reorganization and persists w/out continued performance.

Result: Reorganization not evident until 10days of training but once it has occurred, persists w/out training up to 220 days

Animal studies have shown cortical reorganization is associated with?

Inc in synapse number (due to Skilled reach training).

What is the key to structural plasticity?

Skill acquisition, as it has been shown to inc synapse number and size of the cortical map

Does the development of motor skill and plasticity w/in the motor cortex occur at the same time?

No. significant inc in Skill level occur before changes in synapse number, which also occurs before reorganization

Based on animal studies does strength and endurance training induce cortical reorganization?

No, but skill learning does

What should you do to drive neuroplasticity for your patients?

Give them a task to learn

What are the 10 principles of Neuroplasticity?

• Use it or lose it

• Use it and improve it

• Specificity

• Intensity matters

• Repetition matters

• Time matters

• Salience matters

• Age matters

• Transference or generalization

• Interference

What do Animal studies inform us about representation in the infarcted zone?

Movements formerly represented in the infarcted zone do not reappear in adjacent cortical regions w/out post-infarct training.

What allows for substantial retention of the spared hand area?

Rehabilitative training regimen (based off monkey study)

What does the squirrel monkey study regarding forced training inform us about?

That the group who was given the jacket (forced training) performed slightly better than the control group but they still lost over 50% spared hand area.

What can we conclude based off of studies regarding forced training?

It’s not sufficient to drive structural neuroplasticity after stroke.

Does repetitive motor activity alone produce structural reorganization? What instead is required to drive plasticity?

No, motor skill/learning is a prerequisite in driving plasticity

In rats it has been shown that acrobatic training improved functional performance and enhanced homotopic synaptogenesis. What can we do as therapist to create a similar effect with our patients?

The use of obstacle has been shown to challenge neuromuscular control of LE and structural neuroplasticity

What role does social environment play in rehab (based of rat study)?

Can improve sooner and slightly when placed in enriched environment

What efffect would a unilateral lesion to the sensorimotor cortex cause on contralateral homotopic cortex?

Inc in dendritic arborization. Meaning the other side of the brain will be used since affected side isn’t working.

What is “forced use” or “constraint-induced movement therapy”? (Traditional vs. modified)

Traditional:

• 1. Unaffected UE restrained during 90% of waking hours x 2 weeks

• 2. Intensive, graded practice of the paretic upper limb to enhance task-specific use of the affected limb for up to 6 h a day for 2 weeks

• 3. Adherence-enhancing behavioral methods designed to transfer the gains obtained in the clinic/lab to patients’ real-world environment

Modified CIMT:

• 30 min x 3x/week x 10 weeks shaping therapy

• 5 hours x 5x/week of CIMT

Is there evidence for structural plasticity occuring after training?

3% change w/ 0.2% error rates for brain volume changes

What treatment dose is necessary to obtain MRI-detectable structural changes?

• 90min of balance training drove gray matter volume inc

• (0min of balance training over 2 weeks in PD inc gray matter volume

What are possible mechanisms for map changes (neuroplasticity)?

• Resolution of edema and removal of necrotic tissue

• Restitution of damaged pathways

• Modulation of GABAergic intracortical inhibition

• Changes in synaptic efficacy

• Alteration in transcallosal inhibition

• Substitution from ipsilesional parallel pathways

• Activation of ipsilateral (contralesional) pathways

• Long term potentiation

Does cortical representation of a muscle expand with CIMT?

Yes, it does expand and its COG changes

What are synonymous terms for Skill acquisition?

Task novelty

Challenging task

Does intensity matter for neuroplasticity?

No, but training at higher intensities does show a that “challenge” is a key ingredient in driving improvements in fxn

When should rehabilitative strategies begin for post-stroke pts? What do you want to avoid w/ these pts? When is rehab considered safe?

Within first 2 weeks (optimal time still unknown). Avoid rehab within the first 24hrs (especially intensive rehab). Rehab considered safe beyond 24hrs

What does motor priming help facilitate?

Motor learning and improve neuroplasticity

Whats the theory of motor priming?

A prior method of activation is generally more responsive to the accompanying training. Which can enhance LTP-like mechanisms.

Types of motor priming?

• Stimulation-based motor priming

• Movement-based priming

• Pharmacology-based priming

• Mental practice/motor imagery priming

• Sensory priming

What are the 4 categories of stimulation-based motor priming?

• Repetitive transcranial magnetic stimulation (rTMS)

• Transcranial direct current stimulation (tDCS)

• Paired associative stimulation

• Peripheral nerve stimulation (PNS)

What is repetitive transcranial magnetic stimulation (rTMS)?

• Goes through cranium via magnet to stimulate cortical regions

What causes an inc and Dec in excitability in rTMS?

• Increase corticospinal excitability = high-frequency (5–20 Hz) rTMS trains over M1

• Decrease corticospinal excitability = long trains of low frequency rTMS (1 Hz) applied over M1

What is Transcranial direct current stimulation (tDCS)?

Low-intensity direct current (0.5-2 mA) through active electrode on the scalp modulates neuron potentials by altering the conductance of sodium and calcium channels. Mechanism may be due to LTP and LTD

How does Transcranial direct current stimulation (tDCS)

• Anodal current (+) = upregulation of cortical excitability

• Cathodal current (-) = downregulation of cortical excitability

• Diff montages (placement) should be used to stimulate affected area.

What is transcranial direct current stimulation (tDCS)?

Theory of asymmetric hemisphere excitability post stroke. Often ipsi hemi has Dec excitability, while contra hemi has inc excitability. Thus, this method tries to correct for the imbalance between hemispheres but suppressing activity on one side and exciting affected side.

What is paired associative stimulation (PAS)?

• What is transcranial direct current stimulation (tDCS)

• PAS emphasizes the potent interaction of somatosensory input and cortical

  motor circuits

How does PAS work?

• Increased excitability = afferent peripheral volley is timed to arrive prior to the TMS stimulation

• Decreased excitability = afferent peripheral volley arrives just after TMS stimulation

What is movement based priming?

Repetitve or continuous movement that is done to enhance the effect of an accompanying therapy

Why is it best to do bilateral or mirror symmetric movement for movement based priming?

There’s strong evidence that improvement in motor fxn coincides w/ normalization of transcallosal inhibition, resulting in greater balance between the hemispheres

Aerobic exercise promotes neuroplasticity via what?

BDNF

What does BDNF help with? (5)

• Involved in motor learning and post-stroke motor rehabilitation

• Facilitates LTP

• Secreted in the CNS through both a constitutive and an activity-dependent pathway

• Aerobic exercise increases BDNF

• Exercise-induced increases in BDNF benefit cognitive function

What are the 4 main neurotrophic?

BDNF, GDNF, IGF, VEGF

Although aerobic exercise has shown to be beneficial for brain health, we shouldn’t forget about resistance training for which reason?

The positive effect it has by utilizing muscle as an endocrine gland

Does aerobic exercise improve cognitive fxn?

Yes

What can you do for a post stroke pt to “prime” their system?

Can use aerobic exercise for BDNF release. Which will prime motor learning task later in the session.

To induce large positive effects on cognition and BDNF levels, exercise should include? (4)

• Aerobic sessions of >30 minutes

• Training intensities of approximately 70% EHRM

• Frequency of 4 days per week

• Combination of aerobic and resistance exercises

What are mirror movements? Whats the purposed theory for this?

Concomitant activation of a limb that may reproduce voluntary movements on the contralateral homotopic area. Small uncrossed corticospinal pathways in adult humans are thought to underlie this phenomenon

In what instances do mirror neurons fire when observing a task?

When performing a task and observing someone else perform a task (monkey study)

What advantages do mirror neurons provide from an evolutionary standpoint?

Revs up system or help activate downstream motor areas

Does imagining an action, intending to perform an action and execution of an action share the same functional networks in the brain?

Yes

What are the 5 pharmacological agents proposed to enhance motor recovery?

• Amphetamines

• Dopaminergic agents

• Cholinergic agents

• SSRIs

Whats sensory priming?

Modulation of sensory input through sensory stimulation and sensory deprivation

Changes in somatosensory cortex influences what? and why?

Motor cortex due to strong connections btwn these two cortical areas

What are the sensory priming mechanisms? (3)

• Peripheral nerve electrical stimulation

• Vibration of agonist and antagonist muscles

• Sensory deprivation (tourniquet, nerve blocks, anesthetic cream)

What is temporary functional deaffernation?

Dec in intercortical inhibition from the deafferented cortex of the unaffected limb regions will cause the adjacent injured limb region to work harder

What should you consider about the timing of priming? (5)

• Priming should be done in close proximity to the training

• Priming during motor training appears to enhance learning more than priming applied prior to training

• Priming after training does not appear to be effective

• Pre-workout supplements

• Nootropics (drugs, suppose and other substances)