Download Cognitive Handout 2 - Connecticut Speech-Language

4/25/17
Using Brain Plasticity to
Facilitate Rehabilitation
Sarah A. Raskin
Connecticut Speech Language Hearing Association
[email protected]
Structural Basis of Brain
Plasticity
What is learning?
Learning involves physiological brain
changes
A recovering brain is in a dynamic and
plastic state
We know from non-injured brains that
experience causes brain changes,
including cognitive improvement
New treatments have been designed
with plasticity in mind
The Nature of Learning
Learning refers to the process by which experiences
change our nervous system and hence our behavior.
We refer to these changes as memories.
Experiences are not “stored”; rather, they change the way
we perceive, perform, think, and plan.
They do so by physically changing the structure of the
nervous system, altering neural circuits that participate in
perceiving, performing, thinking, and planning.
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Structural Basis of Brain Plasticity
But what is plasticity?
At the neural level, learning is associated
with changes that take place at the synapse
Can refer to any change from the
molecular level
to synaptic change
to cortical reorganization
to behavior
Neurons that wire together
fire together
The Hebb Rule
Donald Hebb argued that synapses that are
active at the same time are strengthened
over time
Implies that repeated neural activity will
produce physical changes in the nervous system
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Experience Based Changes
Neurogenesis in brain regions when
songbirds learn new songs
Nottebohm, 1985
Experience Based Changes
Rats in enriched environments
heavier brains with new granule cells
higher levels of some neurotransmitters
more nerve cell connections
increased neuronal branching
performed better on learning tasks
Kempermann, Kuhn, & Gage, 1997
Experience Based Changes
Experience Based Changes
Participation in a
learning task alone
leads to new
neurons generated
by stem cells
Gould et al., 1999
This was true compared to both animals in an impoverished
environment and animals in a social environment
Kempermann, Kuhn, & Gage, 1997
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Adult Brains Can Grow New
Cells
New nerve cells in the hippocampus of humans
Cortical Plasticity
New nerve cells in the hippocampus of
adult humans are functional
Eriksson, 1998
Gould & McEwan, 1998
Cortical Plasticity
Before:
Reorganization
Perceptual Reorganization has been shown
in all sensory modalities
The organization can be modified by
damage, pharmacologic intervention, or
change in the sensory environment
After:
Kaas, Merzenich, Killacky, 1983
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Sign Language
Braille Reading
Although sign
language is a visual
and motor process,
it is processed in the
same language
areas used for
speech in hearing
individuals
Reorganization of sensory cortex
Reorganization of cortex
Increased representation for fingers of
string musicians Ebert et al., 1995
The representation of the fingers of
blind Braille readers who use several
fingers simultaneously to read was both
enlarged and disordered; a perceptual
disturbance in which the subjects could
not discriminate which of their fingers
was being touched
Sterr et al., 1998
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Changes in hippocampus in
London taxi drivers
The more demanding the task
Performed by that area, the more
Complex the cells and the networks
And the change correlates with
time spent as taxi driver
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Plasticity after Injury
The percent prevalence of low idea density in early life autobiographies by
late life cognitive state for 180 participants in the Nun Study.
Sensory or Motor Training and Plasticity
Manipulating Experience Experimentally
Ramachandran (1993)
Indirectly measured the cortical maps in
individuals with limb amputations
When the face was stroked softly with a cotton
swab, amputees reported sensations of being
touched in the amputated hand
May explain “phantom limb” pain
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Reorganization of sensory
cortex
Human studies with amputees
Recovery from damage to the
brain
So what happens when someone is
recovering from brain injury?
Elbert, et al., 1994
Theories of Restoration
Vicariance due to equipotentiality
Redundancy
Functional substitution
Recovery from diaschisis (posttraumatic neural depression)
Theories of Restoration
Vicariance due to equipotentiality
Different brain parts can do the same job
Redundancy
Functional substitution
Recovery from diaschisis
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Theories of Restoration
Vicariance due to equipotentiality
Different brain parts can do the same job
Redundancy
Some parts already did the same job
Functional substitution
Recovery from diaschisis
Theories of Restoration
Vicariance due to equipotentiality
Different brain parts can do the same job
Redundancy
Some parts already did the same job
Functional substitution
A new region can learn to do the job
Recovery from diaschisis
Swelling, shock, etc.
Other injury-induced plasticity
Collateral growth or sprouting
Not always adaptive
So a recovering brain is in a very plastic
and dynamic state
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Can we use this to design
training?
Environmental Therapy
Rats were given hippocampul damage
leading to deficits in new learning
Exposure to a complex and enriched
environment for one month was
sufficient to enhance and sustain
recovery compared to an impoverished
environment
Will et al., 1990
Environmental Therapy
The problem is defining enriched
environments for people
And defining the numbers of hours
required
Kolb et al., 2011
Reorganization of sensory
cortex-specific training
First mapped out parts of sensorimotor
cortex active when a finger stimulated
Cut the nerve fibers to that finger
Same areas of cortex now become
active when a different finger is
stimulated within hours
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Reorganization of sensory
cortex
Now, once again map out receptive
fields
Extensive training with rotating disk
Cortical fields enlarged for the trained
finger which endured for some time
Structural Basis of Brain Plasticity
Sensory or Motor Training and Plasticity
Manipulating Experience Experimentally
Nudo and colleagues (1997)
Had monkeys retrieve food from small or large
food wells
Small wells required dexterous movements of one or
two fingers, whereas the monkeys could put their
entire hand in the large wells
The digit representation on the motor cortex was
larger for animals that had to retrieve food from
the smaller wells
Effect of Motor Practice
Lasted up to 8 weeks
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Constraint Induced Movement
Therapy
The animals with cortical damage
recovered more quickly after training
with small wells
Has been used with success in patients
with stroke, brain injury, spinal cord
injury and hip replacement
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Sensory Reorganization
Individuals with cortical blindness who
were given intensive training
dramatically enlarged their visual fields
Unclear whether due to stimulation of
neurons in the blind spot, neurons from
other regions or islands of spared
neurons in the injury zone
Zihl, 1990
Cortical Plasticity
Cognitive Tasks
Reorganization can also occur with
practice on a cognitive task with
humans
PET study during naïve and practiced
performance of a simple verbal task--saying an appropriate verb for a visually
presented noun
Cortical Plasticity
Reorganization
During naïve performance areas most activated
were the anterior cingulate, left prefrontal and left
posterior temporal cortices
During practiced performance they were insular
cortex, left medial extra-striate cortex
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Cortical Plasticity
Reorganization
Reorganization can also occur after practice with a
cognitive task in humans
General Principles of Plasticity
Changes in the brain require repetition
The brain can be altered by a wide range of
experiences
Training must be aware of the specific systems
being trained and the ways that system
responds to training
Experience-dependent changes interact
Kolb, B., Cioe, J. & Williams, P. (2011) Neuronal
organization and change after brain injury. In: Raskin,
S. (ed) Neuroplasticity and rehabilitation. Guilford Press:
NY.
Raichle, Fiez, Videen, MacLeod, Pardo, Fox, & Petersen, 1994
Cognitive Rehabilitation
Future Directions
There is some evidence that cognitive
rehabilitation techniques that are
intensive and take place over many
months lead to changes in brain
function
Sohlberg & Posner, 1998
Raskin & Buckheit, 1998
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Brain-Computer Interface
Brain Gate
Or a computer mouse
Virtual Reality
Cognitive Rehabilitation
The process of relearning skills that
have been lost or altered as a result of
damage to brain cells or altered brain
chemistry. If skills cannot be relearned,
then new ones have to be taught.
Malia, 2014
Rizzo, et al. (2010)
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Approaches to Treatment
Environmental Modifications
changing the environment to alleviate the
need for the deficient function
Compensation
making up for what is deficient by some
external means
Approaches to Treatment
Direct Interventions
Functional Skills Training
Behavior Modification
Medications
Process-specific Training
Direct Intervention
attempting to retrain specific impaired
cognitive functions
Aim of Cognitive Rehabilitation
To improve the ability to carry out
everyday tasks.
Impact on real life
Improve quality of life
Approaches
Cognitive-Didactic (bottom-up)
Functional-Experiential (top-down)
Integrative Holistic—training skills in a
hierarchical manner while ensuring
these skills generalize to daily life
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First Plan for Generalization
Actively plan for generalization from the
beginning
Identify reinforcements in the natural
environment
Program common stimuli between
training and the real world
Use sufficient examples in therapy
Select a method for measuring
Sohlberg & Raskin, 1996
generalization
Levels of Generalization
Level I: Improvement on treatment
tasks
Level II: Improvement on related
neuropsychological tests
Level III: Improvement in daily life
(Gordon, 1987)
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