Neuroplasticity

Neuroplasticity

Dr. Michael P. Gillespie

NeuroplasticityNeuroplasticity is the ability of the brain to

change, for better or for worse, throughout the individual’s life span.

It involves forming neuronal connections in response to information derived from experiences in the environment, sensory stimulation, and normal development (Doidge, 2007; Merzenich, 2001; Nudo, 2008).


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NeuroplasticityNeuroplasticity refers to the moldable structure of

the brain and nerves that results from changes in neural pathways and synapses. These changes stem from changes in behavior, environment, neural processes as well as changes from bodily injury.

The brain does change throughout life.


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Neuroplasticity


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Girl Living With Half Her Brainhttp://www.youtube.com/watch?v=2MKNsI5CWoU


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Positive Outcomes of Neuroplasticity New skills

Better cognition

More efficient communication between sensory and motor pathways

Improved function of the aging brain

Slowing down pathological processes

Promoting recovery of sensory losses

Improved motor control

Improved memory

(Mahncke, Bronstone & Merzenich, 2006; Mahucke & Merzenich, 2006; Nudo 2007; Stein & Hoffman, 2003).


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Negative Outcomes of NeuroplasticityDecline in brain functionAltered motor controlImpaired performance of activities of daily livingAmplified perception of pain


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Neuroplasticityhttp://www.youtube.com/watch?v=iAzmyB9PFt4


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Structural Changes in the BrainSynaptic plasticitySynaptogenesisNeuronal migrationNeurogenesisNeural cell death


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Synaptic PlasticitySynaptic plasticity refers to changes in the

strength of connections between synapses.Long-term potentiation (LTP)Long-term depression (LTD)Changes in the number of receptors for specific

neurotransmitters Up-regulation Down-regulation

Changes in which proteins are expressed inside the cell


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Neuroplasticity – Brain RemodelingSteps to remodel the brain based upon

experiences:1. Repetition2. Correct fundamentals3. Authentic environment


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Neuroplasticity – Brain Remodelinghttp://www.youtube.com/watch?v=VvZ-

9ofM7Go&feature=related


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Synaptogenesis & Synaptic PruningThe creation and removal of entire groups of

synapses.This builds and destroys connections between

neurons respectively.


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Neuronal MigrationNeuronal migration is a process whereby neurons

extend from their place of birth to connect to far reaching areas of the brain.


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NeurogenesisNeurogenesis is the creation of new neurons.It largely occurs in the developing brain.Limited neurogenesis occurs in the adult brain.


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Neural Cell DeathNeurons die.This can happen from either damage, over-

excitation, or disease.Natural programmed cell death including

apoptosis also occurs.


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Functional ReorganizationAs the brain develops, certain areas of the brain

become specialized for specific tasks.If your experience changes dramatically or parts

of the brain are damaged, areas previously specialized for a certain function can take on the work of other areas.


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Brain Functions / Brain RegionsContrary to common

understanding, brain functions are not strictly confined to specific fixed locations as identified in this picture.


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Previously Held BeliefsBrain functions were confined to specific fixed

locations of brain tissue.Brain structure is relatively immutable after a

critical period during early childhood.* New research reveals that many aspects of the

brain remain plastic in adulthood. *


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Levels of NeuroplasticityCellular changes (result of learning)Cortical remapping (response to injury)


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Synaptic PruningSynaptic pruning is a neurological regulatory process

that facilitates a change in neural structure by reducing the overall number of neurons and synapses.

The resulting synaptic connections are more efficient.Pruning is believed to represent the learning process.Synapses that are frequently used have strong

connections whereas those that are rarely used are eliminated.

“Neurons that fire together, wire together. Neurons that fire apart, wire apart”.


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Synaptogenesis / Synaptic Pruninghttp://www.youtube.com/watch?

v=tJ93qXXYRpU&feature=related


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Cortical MapsSensory information from certain parts of the body

projects to specific regions of the cerebral cortex.As a result of this somatotrophic organization of

sensory inputs to the cortex, cortical representation of the body resembles a map (or a homonculus).


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The Learning Brainhttp://www.youtube.com/watch?

v=cgLYkV689s4&feature=related


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Homunculus


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Removing Sensory InputsIf a cortical map is derived of sensory input, the

adjacent segments it will become activated by adjacent sensory inputs.

Merzenich’s 1984 study involved the mapping of owl monkey hands before and after amputation of the third digit.Before amputation, there were five distinct areas

corresponding to each individual digit.After amputation of the third digit, the area of the cortical

map formerly occupied by the third digit was invaded by the previously adjacent second and fourth digit zones.

Only the regions bordering a certain area will invade it will alter the cortical map.


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Sensory Site ActivationSensory sites that are activated in an attended operant

behavior increase their cortical representation (Merzenich and William Kenkins (1990)).

When a stimulus is cognitively associated with reinforcement, its cortical representation is strengthened and enlarged (Merzenich and DT Blake (2002, 2005, 2006).

Cortical representations can increase two to threefold in 1-2 days at the time in which a new sensory motor behavior is first acquired and changes are largely finished within a few weeks.


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Phantom LimbsPhantom limbs are experienced by people who

have undergone amputations.Cortical reorganization appears to play an

important role in phantom limb sensation.Mirror box therapy developed by Vilayanur

Ramachandran has shown great promise in treating phantom limb pain.


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Phantom Limb Pain


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Mirror Box A diagrammatic

explanation of the mirror box. The patient places the good limb into one side of the box (in this case the right hand) and the amputated limb into the other side. Due to the mirror, the patient sees a reflection of the good hand where the missing limb would be (indicated in lower contrast). The patient thus receives artificial visual feedback that the "resurrected" limb is now moving when they move the good hand.


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Mirror Visualization Therapyhttp://www.youtube.com/watch?

v=Pe8Y3YETnuY&feature=relmfuhttp://www.youtube.com/watch?

v=hMBA15Hu35M&feature=related


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Spatial CouplingMarian Michielsen suggested that Ramachandran’s

Mirror Box therapy worked by enhancing spatial coupling between limbs.


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Treatment of Brain DamageBrain activity associated with a given function can

move to a different location.This concept allows for the treatment of acquired

brain injury.The adult brain is not hard-wired with fixed

neuronal circuits.Cortical and subcortical rewiring of neuronal

circuits happens in response to training and in response to injury.


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NeurogenesisNeurogenesis is the process by which neurons are

generated from neural stem cells.Recent studies show that neurogenesis occurs in

the adult mammalian brain and can persist well into old age.This appears to occur in the hippocampus, olfactory

bulb, and cerebellum. In the rest of the brain, neurons can dies, but cannot

be recreated.


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Rehabilitation Techniques That Precipitate Cortical ReorganizationConstraint-induced movement therapyFunctional electrical stimulationTreadmill training with body weight supportVirtual reality therapy


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Constraint-induced Movement Therapy (CIMT)This therapy improves upper extremity function in stroke

victims and other victims with central nervous system damage.

The purpose is to combine restraint of the unaffected limb and intensive use of the affected limb.

Types of restraints: Sling Triangular bandage Splint Half glove Mitt


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Constraint-induced Movement Therapy (CIMT)The use of the affected limb is called shaping.Training typically involves restraining the unaffcted

limb and using the affected limb for 90% of waking hours.

Receiving CIMT early (3-9 months post-stroke) results in greater functional gains than receiving delayed treatment (15-21 months post-stroke).

Factors for success of CIMTConcentrated and repetitive practice of the affected limb.The unaffected limb must be constrained 90% of the

waking hours.


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Constraint-induced Movement Therapy (CIMT)


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Constraint-induced Movement Therapy (CIMT)http://www.youtube.com/watch?v=MMTh2hWvB2g


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Functional Electrical StimulationFunctional electrical stimulation uses electrical

currents to activate nerves innervating extremities affected by paralysis resulting from spinal cord injury, head injury, stroke, and other neurological disorders.

Sometimes it is referred to as Neuromuscular electrical stimulation (NMES).


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Functional Electrical Stimulation


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Contralaterally Controlled Functional Electrical Stimulation Stroke Therapyhttp://www.youtube.com/watch?v=boz0HQXQhKg


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Treatment of Learning DifficultiesMichael Merzenich developed a series of plasticity

based computer programs known as Fast ForWord.

The programs consist of seven brain exercises to help with the language and learning deficits of dyslexia.

The software also improved cognitive function in adults with age related cognitive decline (ARCD).


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Chronic PainSome people suffer chronic pain at sites that were

previously injured, but are currently healthy.Chronic pain happens as a result of maladaptive

reorganization of the nervous system both peripherally and centrally.

During the period of tissue damage, prolonged nociceptive input from the periphery to the central nervous system results in somatotopic organization and central sensitization.


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MeditationMeditation has been linked to cortical thickness and the

density of gray matter.Richard Davidson performed experiments with H.H. the

Dalai Lama to examine the effects of mediation on the brain.

Long term and short term practice of meditation resulted in different levels of activity in brain regions associated with qualities such as attention, anxiety, depression, fear, and anger.

Mediation also demonstrated an effect on the ability of the body to heal itself.

Changes in the physical structure of the brain appear to be responsible for these differences.


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Exercise Induced NeuroplasticityAll forms of exercise appear to produce neuronal

changes in the brain; however, different forms of exercise produce changes in different brain regions.

More demanding forms of exercise seem to promote change in more diverse areas of the brain.


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Neuroplasticity & Occupational TherapyLearning and memory are the result of experience

driven alterations of the synaptic structures of neurons.

“Occupational Therapy practitioners set up the circumstances and situations that modify the environment and the degree of challenge for a skill set (just the right challenge) that creates an adaptive response that originates at the cellular and molecular level” (McCormack, 2009).

Neuroplasticity reflects the brain’s ability to grow and change into old age as long as it is engaged in meaningful occupations. This is the basis of occupational therapy (Christiansen & Baum, 2005).


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Types of NeuroplasticityPractice-Dependent PlasticityCompetitive PlasticityPositive PlasticityNegative Plasticity


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Practice-Dependent PlasticityA person performs a task repeatedly to learn or re-

learn a skills set.“The neurons that fire together, wire together”

(Hebb’s concept).http://www.youtube.com/watch?v=5iyodWeFkLEYou can incorporate constraint induced OT as well

to “force” neurons to fire together and “unmask” latent neurons to activate those neuronal pathways.


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Competitive PlasticityUse or disuse of a neuronal pathway will lead to

natural selection of the pathways utilized.“Use it or lose it”The cerebral cortex is constantly remodeling itself

according to influences from the environment (Bear et al, 2007; Mahncke, Bronstone et al, 2006).


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Positive PlasticityCompensatory changes occuring at the cellular

and molecular levels (dendritic sprouting).Temporal changes (speed of action potentials).Release of neuromodulators.Influence of second messengers (i.e. producing

new postsynaptic membrane receptors).Formation of alternative pathways that make new

functional connections in the cortex and tract systems.


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Dendritic Sprouting


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Neurite Outgrowthhttp://www.youtube.com/watch?

v=n_9YTeEHp1E&feature=related


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Negative PlasticityNegative plasticity occurs when dendritic sprouting and

proliferation of postsynaptic membrane receptors results in excessive production of excitatory impulses producing hypertonicity in muscles.

Good motivation and attention release neuromodulators (dopamine and acetylcholine) that promote faster synapses and positive changes in cortical mapping.

Poor motivation and lack of effort produces weak synaptic connections and synapses that are slower. These neurons sometimes undergo apoptosis.

“Neurons that fire out of sync, fail to link” (Bear et al., 2007; Fillipi, 2002; Woolf & Salter, 2000).


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Secondary Neural PathwaysAfter a lesion in the central nervous system, the

usual neuronal pathways are blocked or destroyed.

We can develop secondary neuronal pathways to send neuronal signals around the blockage.

We say that secondary neuronal pathways become “unmasked” and get stronger with use.

This is analogous to a bridge going out. We can take secondary roads. This path may take longer, but shorter paths will be found.


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Compensation If a person loses one sensory modality, other senses can

compensate and take over.Teaching ways to adapt, modify, or change the method to

perform the task.This may involve modifying the environment. It may involve training the family members or caregivers

to assist.Compensation involves the brain’s ability to recruit other

neurons in other regions of the nervous system. It is a form of neuroplasticity and not just a way to modify or adapt.


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Neuroplasticity in Pain SyndromesNeuropathic pain and pain hypersensitivity are

examples of negative plasticity.Activation of nociceptive pathways is the response

of the system to repeated stimuli.


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Neuroplasticity in Repetitive Strain InjuriesComplex bio-psychosocial responses can cause

undesirable outcomes in localized injuries (Nudo, 2007).Therefore, it is necessary to “treat the whole person”.OT practitioners should stimulate practice-dependent

plasticity by facilitating adaptive responses that engage the cerebral cortex.

Mental rehearsals and guided imagery techniques release neuromodulators such as dopamine, norepinephrine, and acetylcholine.

These neuromodulators influence neuroplasticity and the formation of new cortical maps.


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Mechanisms of Neuroplasticity1. Diaschisis – neuronal structures that are anatomically

connected to a lesion or region damaged by stroke undergo reduced blood supply and metabolism.

2. Behavioral compensation – occupational therapy directs the individual’s interaction with the environment to utilize viable neurons surrounding the area of the lesion in order to reorganize their capacity to compensate for damaged neurons.

3. Adaptive plasticity – dendritic growth and angiogenesis occurs near the damaged areas. Dendritic growth is an adaptive response to substitute for the lost function. This is a critical time of OT intervention. Positive plasticity happens through use or doing. Negative plasticity happens through disuse or doing little.


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OT in Cognitive RehabilitationCognitive impairments are an example of negative

plasticity that affects mood and the ability to problem solve. This in turn can reduce motivation.

Interventions used in occupational therapy that stimulate change and repetition are important in strengthening connections between neurons (Meintzschel & Ziemann, 2006).

If the practitioner uses a novel stimulus, it should be followed immediately by some reward or reinforcement. It should be repeated again and again to drive synaptic change.


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Compensatory Cognitive Strategies Changes in environmental structure and support. Visual aids. Checklists. Step-by-step instructions. Remedial cognitive interventions include repetitively practicing

tasks that require specific cognitive functions and challenges. Video games Virtual reality Neurofeedback training

Brain-computer interface technology can deliver repetition, challenge, and motivation rapidly and consistently.


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Neurofeedback Traininghttp://www.youtube.com/watch?v=GJRWYxEEFv0


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Brain Computer Interfacehttp://www.youtube.com/watch?v=ZwuMg0FsKzs


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Neuroplasticity

Documents

adult brain

developing brain

gillespiestructural

regulation changes

changes stem

sensory stimulation

bronstone merzenich

mahucke merzenich