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PLASTICITY AND REHABILITATION

n An end to nihilism

BIO

n Chair and Professor, Department of Communicative Disorders, University of Florida

n In position of needing to generate my salaryn As researcher and cliniciann Scientist at the Brain Rehabilitation Research

Center

THAT LAST IS IMPORTANT

n Our reason for being as researchers is to study treatments

n We do so with a group of SLPS, PTs, OTs, neuropsychologists, and neurologists

OUR BELIEF

n Treatment done according to principles influences the brain and behavior

n Doing nothing can have disastrous consequences

n The rehabilitationists major duty is to develop the best possible behavioral treatments

THE REASON

n The best biomedical advances will have muted effects without behavioral treatments

n Rehabilitationists can see themselves as teachers of cells

n Whether those cells are imported or specially activated

MY COLLABORATORS

n Dr. Leslie Gonzalez-Rothin Dr Steve Nadeaun Dr Bruce Crossonn Dr. Diane Kendalln Dr. Steve Kautz

OUTLINE OF PRESENTATION

n Plasticity definedn Principles guiding rehabilitationn Examples primarily from swallowing where

much of the seminal work has been done in bulbar and language function

n Defining treatment effects

PLASTICITY DEFINED

n Flexibility of neural substrates so that alteration to support function is possible

n Or, Filipek (2000). Brain’s ability to recover function that was lost as result of insult.

n Thus we talk of neuroplastic changes in the anatomy and physiology of intact cortical and subcortical tissues (Nudo et al. 2000)

REFERENCES ON PLASTICITY

n Levin, Grafman (2000). Cerebral Reorganization of Function after Brain Damage. Oxford: Oxford University Press.

n Kolb (1995). Brain Plasticity and Behavior. Mahwah, NJ: Erlbaum.

n Dobkin. The Clinical Science of Neurologic Rehabilitation. Oxford, 2003.

CRITICAL REHAB NOTION

n Plastic change does not occur completely on their own

n The guiding notions of this presentationn PLASTICITY IS USE/EXPERIENCE

DEPENDENTn ALL USE/EXPERIENCE IS NOT EQUAL

CONSIDER THESE STATEMENTS

n “The cortex can preferentially allocate area to represent the particular peripheral in put sources that are proportionally most used”

n “The rules governing this cortical representational plasticity following manipulation of inputs, including learning, are increasingly well-understood”n Buonomano & Merzenich,Annual Review of

Neuroscience, 1998, 21:149-186

HEBB’S RATS

n His rats allow us to think about one more important notion

n He took half his rats home to live in the house with the family

n Then he compared the learning of those and the rats maintained in cages in the lab

n The learning of the home rats was superior

THE LESSON

n Environmental enrichment can increase plasticity

n Experience or use dependent plasticity can be increased by:n The right training n A generally enriched environment

CAJAL’S FOLLY

TWO MISTAKES

n Women have no place in sciencen The adult brain is immutable

OPTIMISM

n During the past two decades, experimental studies in animals and neurophysiological and neuroimaging studies in humans have demonstrated that the adult brain maintains the ability to reorganize throughout life

n Butefisch. The Neuroscientist, 2004, 10:163-173

PRINCIPLES

n I need to thank Jeffrey Klime and Theresa Jones for these

n 10 principles can govern how we think about use dependent plasticity

n Will list each and draw an example or two from a variety of literatures

ONE: USE IT OR LOSE IT

n The brain is precious real estaten As Kleim and Jones say, “failure to drive

specific brain functions through training can lead to the degeneration of that function

n And to the assumption of its neural substrate by some other function

n One of the powerful motivators of rehab

EXAMPLE

n Tape the fingers of braille readers and the finger differentiation disappears

TWO: USE IT AND IMPROVE IT

n Training enhances function whether in development or in rehabilitation

n There is no behavior change without brain change

EXAMPLES

n Constrain induced movement therapyn Weight-supported gait trainingn Lee Silverman Voice Therapy Program

THREE: PLASTICITY IS EXPERIENCE SPECIFIC

n One gets better at doing what one practices

n Cortical and subcortical regions are expanded predictably

n Leads many researchers to argue for skill rather than use dependent plasticity

CONSIDER CORTICAL SWALLOWING AREAS

n We know that electrical stimulation of the pharynx improves swallowing function and expands the pharyngeal representation in cortex

Cortical Areas of Representation

LESSONS

n Training needs to be specific to the function being improved

n Examples of this principles abuse abound in speech rehab

n We have people sticking out their tongues as far as they can

n Yet no speech or swallow activity requires that movement

FOUR: REPETITION MATTERS

n Once is not enoughn How many times is not yet clear for many

behaviorsn But once or twice weekly treatments are likely to

be fecklessn CIMT, depending on protocol, is hours per day

FIVE: INTENSITY MATTERS

n Intensity admits to multiple definitionsn I am using it to refer to effort or loadn Simply moving does not improve performancen Moving with steadily increasing accuracy (skill)

or effort or load will

SIX: TIME MATTERS

n the young brain is more plastic than the oldn But the old is not immutablen Age should not be a factor in the decision to

treat

SEVEN: SALIENCE MATTERS

n By this I mean purposen Reaching for a purpose is different from simply

reachingn Salience is especially important in

communication therapy

EIGHT: TIME MATTERS

n Different forms of plasticity occur at different times during training

n Even the placebo effect is accompanied by changes in brain

n Early effects may be result of unmaskingn Later from changes at the synapsen Consider mechanisms of plasticity briefly

MECHANISMS OF PLASTICITY

n Unmaskingn Vicariationn Synaptogenesis

UNMASKING

n The mechanism of using previously existing connections

n In other words other ways of supporting the activity are revealed when a lesion occurs

n May explain some reasonably rapid changes in behavior after insult

n For example ipsilateral fibers, while less numerous may support function impaired by loss of contralateral fibers

VICARIATION

n Mobilization of a region connected to the damaged substrate (Benton and Tranel, 2000).

n Can be adjacent, homologous on the other side of the brain, or at a distance as in the subcortical region in the case of cerebral injury

n Probably associated with later plastic change, however

EXPERIMENTAL ISSUE

n Whether reasonably quick improvement is a function of this mechanism or of unmasking

n Or whether experience (treatment) is necessary

SYNAPTOGENESIS

n Growth of new connectionsn Almost inevitably is experience or use

dependentn Almost inevitably requires extensive, intensive

stimulation

ONE MORE NOTION

n Excitotoxic effects of exercise in animals have been documented

n Extreme exercise can extend the ischemic lesion in experimentally lesioned mice

n However absence of activity can extend this period of vulnerability

n So the right amount of exercise acutely may be key

A USEFUL REFERENCE

n Kozlowski et al.Journal of Neuroscience. 1996, 16:4776-4786

NINE: TRANSFERENCE

n As Kleim and Jones say, “Plasticity that occurs in response to one training experience can enhance the acquisition of similar behaviors

n This is in part basis for generalization which is orderly

TEN: INTERFERENCE

n Again, according to them, “Plasticity that occurs in response to on training experience can interfere with the acquisition of other behaviors

n May be in part the explanation for treatment induced perseveration

THE GOOD NEWS

n Plasticity even in the adult, damaged brain is possible

n Cynicism about rehab is totally unjustifiedn The cynic can only be at home in Jurassic Parkn But it does not occur maximally in the absence of

systematic, goal directed stimulation (therapy)