Neuroplasticity

Mr. Phinoj K Abraham (MOTh)Assistant Professor,

SRM College of Occupational Therapy

Neuroplasticity

plastos (plastos) - ‚capable of being molded’

Neuroplasticity: ‘the ability of the CNS to remodel itself’

Neuroplasticity is how we adapt to changing

conditions, learn new facts, and develop new

skills.

It is constantly occurring; the brain is always

changing (Mark Hallet 2005)

Overview

Neuroplasticity

Historical Background

Two Current Concepts

Importance in Rehabilitation

Role of Occupational Therapist

Related Research

Historical Background

Historical Background

Until 1970 : brain structure is relatively immutable in

adulthood.

In the 1960s,

Paul Bach-y-Rita - electrically stimulated chair with 400

vibrating stimulators for congenitally blind.

He Concluded, “We see with our brains, not with our eyes.”

Doidge, Norman (2007)

History Contd…

A tragic stroke that left his 68 year old father paralyzed

inspired Bach-y-Rita to study brain rehabilitation

His brother – a physician- rehabilitated him and he recovered

well

He believed that ‘Under conditions of interest, such as that

of competition, the resulting movement may be much more

efficiently carried out than in the dull, routine training in the

laboratory’

(Franz, 1921, pg.93)

History Contd…

David Hubel and Torsten Wiesel:

Study with kittens

The experiment involved sewing one eye shut and

recording the cortical brain maps

the portion of the kitten’s brain associated with the shut

eye was not idle, as expected. Instead, it processed visual

information from the open eye.

“… as though the brain didn’t want to waste any ‘cortical

real estate’ and had found a way to rewire itself.”

History Contd…

Jenkins & Merzenich (1987) removed monkey’s 1 Peripheral

Nerve , later found that adjacent neurons had started to

respond to the palm.

History Contd…

(Ramachandran V 1992).

“if someone were to lose their right

hand in an accident, they may then have

the feelings of a phantom limb because

the areas in the somatosensory cortex

that are near to the ones of the hand

(the arm and face) will take over (or

"remap") this cortical region that no

longer has input”

Current Concepts

Two current concepts

Enhancement of existing connections

Very active research area; concepts are continually being updated A very active research area; concepts are continully being updated

Formation of new connections

Types of Neuroplasticity

Type Mechanism Duration

1. Enhancement of existing connections

A. Synapse development Physiological ms-1 to hours B. Synapse strengthening Biochemical hours to days

2. Formation of new connectionsA. Unmasking Physiological minutes to daysB. Sprouting Structural days to months

1. Enhancement of existing connections

Increased use of a synapse in existing pathways e.g. learning a new task

Or alternative pathways following damage

Opposite: dendrite atrophy

1 A) Synapse development

Increased afferent input

New synapses evolve leading to increased excitation

+

+

+

1 A) Synapse development Contd…

Ragert et al., 2004

1 B) Synapse strengthening

Effectiveness of a synapse can be increased for at least 3 durations:

1. Seconds and minutes (short-term memory)

2. Hours and days (intermediate-term memory)

3. Months and years (long-term memory)

Such changes can take place at

three cellular locations:

4. Presynaptic terminal

5. Postsynaptic membrane

6. Postsynaptic nucleusKidd et al., 1992

1 B) Synapse strengthening Contd..

Two point discrimination threshold in pianists index finger

R L

Ragert et al., 2004

Comparison of musicians to non-musiciansFindings were long-lasting piano practising resulted in lower spatial discrimination thresholds in the index finger of piano players in comparison to non-musicians.This decrease in threshold was related to the number of hours practised per day (>3 hours), not to the number of years they had been playing

2) Formation of new connections

Unmasking of pre-existing pathways

Sprouting of new pathways

2 A) Unmasking of silent synapses

Possible reasons why some synapses could be ‘silent’

Inhibited by dominant pathwaysToo little transmitterToo few receptorsDon’t fire with other inputs

Unmasking – inhibition of subservient pathway by dominant pathway

Subservient pathway

Parallel pathway; neurons with a comparable role

Dominant pathway++

Unmasking Contd…

Lesion to dominant pathway

Subservient pathway is unmasked

Activity is continued despite lesion

++

2 B). Sprouting

Cell body

Axon

Sprouting occurs following damage or denervation to the nervous system and is the growth of new axons from cell bodies forming new pathways

Sprouting Contd…

lesion

Nerve Growth Factor (NGF)

Following denervation, neurotrophic factors or nerve growth factors are released, they are polypeptides capable of promoting neuronal survival.

INJURY

Sprouting Contd…

lesion

NGF

Neurite induced to sprout by NGF

The release of nerve growth factors stimulates neurites or new axons to sprout and look for the source of the NGF

INJURY

Sprouting Contd…

Cell is re-innervated from alternative stimulus

Sprouting may be a means of recovery; it may also produce unwanted effects For example spinal cord injury patients may

experience strange sensations.

Injury results in cell death

The Role of Occupational Therapy

1. Strengthen and develop normal synapses

2. Guide axonal sprouting

3. Facilitate unmasking of alternative or previously subservient pathways

OT’st need to

How?

Provide positive sensory input i.e. “appropriate handling”

Facilitate “functional” movement

Provide treatment at “optimum” time

Education

Neuroprotective Motor Enrichment Factors affecting Outcomes

NEGATIVE PLASTICITY

POSITIVE PLASTICITY

Stimulation Disuse/ unskilled Intensive, skilledQuality ofsensory input

Noisy. nonspecific Appropriate / specific

Modulation Not challenging Novel & Challenging

Outcome Negative behaviors Positive behaviors

Releted Research

Mirror Therapy for patients with stroke & AmputationRamachandran, Rogers-Ramachandran & Cobb 1995

HypothesisEvery time the patient attempted to move the paralyzed limb, they received sensory feedback (through vision and proprioception) that the limb did not move. This feedback stamped itself into the brain circuit (Hebbian Learning)So even when the limb was no longer present, the brain had learned that the limb (and subsequent phantom) was paralyzed. Often a phantom limb is painful because it is felt to be stuck in an uncomfortable or unnatural position, and the patient feels they cannot move it.

Mirror therapy contd…

Mirror Box

To retrain the brain, and thereby

eliminate the learned paralysis

The patient places the good limb into

one side, and the stump into the

other

It appears as if the phantom limb is

also movingto unclench it from potentially painful positions.

(Ramachandran, Rogers-Ramachandran & Cobb 1995)

Neuroplasticity & Occupational Therapy Research

Ex.

“Examining the Neuroscience Evidence for Sensory-

Driven Neuroplasticity: Implications for Sensory-

Based Occupational Therapy for Children and

Adolescents”Shelly J. Lane and Roseann C.

SchaafAmerican Journal of Occupational Therapy

May/June 2010 vol. 64 no. 3 375-390

Summery

Neuroplasticity is the focus of a growing body of

research with significant implications for neuro-

rehabilitation.

Neuroplasticity - while not a concept unique to

OT - holds tremendous application for neuro-

rehabilitation provided by OTs.

ReferenceBibliography

Neurological Rehabilitation – Umphred Darcy 4th editionPhysiological basis of Rehabilitation

JournalsMirror therapy improves hand function in subacute stroke: a randomized controlled trial. Arch Phys Med Rehabil. 2008 Mar;89(3):393-8.Guest Editorial - Neuroplasticity and rehabilitation assesssed from www.rehab.research.va.gov/jour/05/42/4/pdf/hallet.pdf retrieved on 3-03-12

Net Referenceshttp://en.wikipedia.org/wiki/Neuroplasticity retrieved on 3-03-12 http://en.wikipedia.org/wiki/Mirror_box retrieved on 3-03-12 http://en.wikipedia.org/wiki/Hebbian_learning retrieved on 3-03-12

Thank you..!!