Contrary to common ideas as expressed in this diagram, brain functions are not confined to certain fixed locations.
Neuroplasticity, also known as
brain plasticity, is an
umbrella term that encompasses both
synaptic plasticity and
non-synaptic plasticity—it
refers to changes in neural pathways and synapses which are due to
changes in behavior, environment and neural processes, as well as
changes resulting from bodily injury.
[1]
Neuroplasticity has replaced the formerly-held position that the brain
is a physiologically static organ, and explores how - and in which ways -
the brain changes throughout life.
[2]
Neuroplasticity occurs on a variety of levels, ranging from cellular
changes due to learning, to large-scale changes involved in
cortical remapping
in response to injury. The role of neuroplasticity is widely recognized
in healthy development, learning, memory, and recovery from brain
damage. During most of the 20th century, the consensus among
neuroscientists was that brain structure is relatively immutable after a
critical period
during early childhood. This belief has been challenged by findings
revealing that many aspects of the brain remain plastic even into
adulthood.
[3]
Hubel and
Wiesel had demonstrated that ocular dominance columns in the lowest neocortical visual area, V1, were largely immutable after the
critical period in development.
[4]
Critical periods also were studied with respect to language; the
resulting data suggested that sensory pathways were fixed after the
critical period. However, studies determined that environmental changes
could alter behavior and cognition by modifying connections between
existing neurons and via neurogenesis in the hippocampus and other parts
of the brain, including the
cerebellum.
[5]
Decades of research
[6]
have now shown that substantial changes occur in the lowest neocortical
processing areas, and that these changes can profoundly alter the
pattern of neuronal activation in response to experience.
Neuroscientific research indicates that experience can actually change
both the brain's physical structure (
anatomy) and functional organization (
physiology).
Neuroscientists are currently engaged in a reconciliation of critical
period studies demonstrating the immutability of the brain after
development with the more recent research showing how the brain can, and
does, change.
[7]
Neurobiology
One of the fundamental principles of how neuroplasticity functions is linked to the concept of
synaptic pruning, the idea that individual
connections within the
brain
are constantly being removed or recreated, largely dependent upon how
they are used. This concept is captured in the aphorism, "neurons that
fire together, wire together"/"neurons that fire apart, wire apart." If
there are two nearby neurons that often produce an impulse
simultaneously, their
cortical maps
may become one. This idea also works in the opposite way, i.e. that
neurons which do not regularly produce simultaneous impulses will form
different maps.
Cortical maps
Cortical organization, especially for the
sensory systems, is often described in terms of
maps.
[8]
For example, sensory information from the foot projects to one cortical
site and the projections from the hand target in another site. As the
result of this somatotopic organization of sensory inputs to the cortex,
cortical representation of the body resembles a map (or
homunculus).
In the late 1970s and early 1980s, several groups began exploring the impacts of removing portions of the
sensory inputs.
Michael Merzenich,
Jon Kaas and Doug Rasmusson used the cortical map as their
dependent variable.
They found—and this has been since corroborated by a wide range of
labs—that if the cortical map is deprived of its input it will become
activated at a later time in response to other, usually adjacent 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,
one corresponding to each digit of the experimental hand. Sixty-two days
following amputation of the third
digit, the area in the
cortical map
formerly occupied by that digit had been invaded by the previously
adjacent second and fourth digit zones. The areas representing digit one
and five are not located directly beside the area representing digit
three, so these regions remained, for the most part, unchanged following
amputation.
[9]
This study demonstrates that only those regions bordering a certain
area will invade it to alter the cortical map. In the somatic sensory
system, in which this phenomenon has been most thoroughly investigated,
JT Wall and J Xu have traced the mechanisms underlying this plasticity.
Re-organization is not cortically
emergent, but occurs at every level in the processing hierarchy; this produces the map changes observed in the cerebral cortex.
[10]
Merzenich and William Jenkins (1990) initiated studies relating
sensory experience, without pathological perturbation, to cortically observed plasticity in the
primate somatosensory system, with the finding that sensory sites activated in an attended
operant behavior increase in their cortical representation. Shortly thereafter, Ford Ebner and colleagues (1994) made similar efforts in the
rodent whisker barrel cortex
(also somatic sensory system). These two groups largely diverged over
the years. The rodent whisker barrel efforts became a focus for Ebner,
Matthew Diamond, Michael Armstrong-James, Robert Sachdev, Kevin Fox and
great inroads were made in identifying the locus of change as being at
cortical
synapses expressing NMDA receptors, and in implicating
cholinergic inputs as necessary for normal expression. However, the rodent studies were poorly focused on the
behavioral
end, and Ron Frostig and Daniel Polley (1999, 2004) identified
behavioral manipulations as causing a substantial impact on the cortical
plasticity in that system.
Merzenich and DT Blake (2002, 2005, 2006) went on to use cortical implants to study the evolution of plasticity in both the
somatosensory and
auditory systems. Both systems show similar changes with respect to
behavior. When a stimulus is cognitively associated with
reinforcement,
its cortical representation is strengthened and enlarged. In some
cases, cortical representations can increase two to threefold in 1–2
days at the time at which a new sensory motor behavior is first
acquired, and changes are largely finished within at most a few weeks.
Control studies show that these changes are not caused by sensory
experience alone: they require learning about the sensory experience,
and are strongest for the stimuli that are associated with reward, and
occur with equal ease in operant and classical conditioning behaviors.
An interesting phenomenon involving cortical maps is the incidence of
phantom limbs. Phantom limbs are experienced by people that have undergone
amputations
in hands, arms, and legs, but it is not limited to extremities.
Although the neurological basis of phantom limbs is still not entirely
understood it is believed that cortical reorganization plays an
important role.
[11]
Norman Doidge,
following the lead of Michael Merzenich, separates manifestations of
neuroplasticity into adaptations that have positive or negative
behavioral consequences. For example, if an organism can recover after a
stroke to normal levels of performance, that adaptiveness could be
considered an example of "positive plasticity". Changes such as an
excessive level of neuronal growth leading to
spasticity or
tonic paralysis, or an excessive release of
neurotransmitters
in response to injury which could kill nerve cells, would have to be
considered "negative" plasticity. In addition, drug addiction and
obsessive-compulsive disorder are deemed examples of "negative
plasticity" by Dr. Doidge, as the synaptic rewiring resulting in these
behaviors is also highly maladaptive.
[11][12]
A 2005 study found that the effects of neuroplasticity occur even
more rapidly than previously expected. Medical students' brains were
imaged during the period when they were studying for their exams. In a
matter of months, the students' gray matter increased significantly in
the posterior and lateral parietal cortex.
[13]
Applications and example
Treatment of brain damage
A surprising consequence of neuroplasticity is that the brain
activity associated with a given function can move to a different
location; this can result from normal experience and also occurs in the
process of recovery from brain injury. Neuroplasticity is the
fundamental issue that supports the scientific basis for treatment of
acquired brain injury with goal-directed experiential therapeutic programs in the context of
rehabilitation approaches to the functional consequences of the injury.
The adult brain is not entirely "
hard-wired" with fixed
neuronal circuits.
There are many instances of cortical and subcortical rewiring of
neuronal circuits in response to training as well as in response to
injury. There is solid evidence that
neurogenesis (birth of brain cells) occurs in the adult, mammalian brain—and such changes can persist well into old age.
[3] The evidence for neurogenesis is mainly restricted to the
hippocampus and
olfactory bulb, but current research has revealed that other parts of the brain, including the cerebellum, may be involved as well.
[5]
In the rest of the brain, neurons can die, but they cannot be
created. However, there is now ample evidence for the active,
experience-dependent re-organization of the synaptic networks of the
brain involving multiple inter-related structures including the cerebral
cortex. The specific details of how this process occurs at the
molecular and ultrastructural levels are topics of active neuroscience
research. The manner in which experience can influence the synaptic
organization of the brain is also the basis for a number of theories of
brain function including the general theory of mind and epistemology
referred to as
Neural Darwinism and developed by immunologist Nobel laureate
Gerald Edelman.
The concept of neuroplasticity is also central to theories of memory
and learning that are associated with experience-driven alteration of
synaptic structure and function in studies of
classical conditioning in invertebrate animal models such as
Aplysia. This latter program of neuroscience research has emanated from the ground-breaking work of another Nobel laureate,
Eric Kandel, and his colleagues at
Columbia University College of Physicians and Surgeons.
Paul Bach-y-Rita, deceased in 2006, was the "father of sensory substitution and brain plasticity."
[14] In working with a patient whose vestibular system had been damaged he developed BrainPort,
[15] a machine that "replaces her vestibular apparatus and [will] send balance signals to her brain from her tongue."
[11]
After she had used this machine for some time it was no longer
necessary, as she regained the ability to function normally. Her
balancing act days were over.
[16]
Plasticity is the major explanation for the phenomenon. Because her
vestibular system was "disorganized" and sending random rather than
coherent signals, the apparatus found new pathways around the damaged or
blocked neural pathways, helping to reinforce the signals that were
sent by remaining healthy tissues. Bach-y-Rita explained plasticity by
saying, "If you are driving from here to Milwaukee and the main bridge
goes out, first you are paralyzed. Then you take old secondary roads
through the farmland. Then you use these roads more; you find shorter
paths to use to get where you want to go, and you start to get there
faster. These "secondary" neural pathways are "unmasked" or exposed and
strengthened as they are used. The "unmasking" process is generally
thought to be one of the principal ways in which the plastic brain
reorganizes itself."
[11]
Randy Nudo's
group found that if a small stroke (an infarction) is induced by
obstruction of blood flow to a portion of a monkey’s motor cortex, the
part of the body that responds by movement will move when areas adjacent
to the damaged brain area are stimulated. In one study, intracortical
microstimulation (ICMS) mapping techniques were used in nine normal
monkeys. Some underwent ischemic infarction procedures and the others,
ICMS procedures. The monkeys with ischemic infarctions retained more
finger flexion during food retrieval and after several months this
deficit returned to preoperative levels.
[17]
With respect to the distal forelimb representation, "postinfarction
mapping procedures revealed that movement representations underwent
reorganization throughout the adjacent, undamaged cortex."
[17]
Understanding of interaction between the damaged and undamaged areas
provides a basis for better treatment plans in stroke patients. Current
research includes the tracking of changes that occur in the motor areas
of the cerebral cortex as a result of a stroke. Thus, events that occur
in the reorganization process of the brain can be ascertained. Nudo is
also involved in studying the treatment plans that may enhance recovery
from strokes, such as physiotherapy, pharmacotherapy and electrical
stimulation therapy.
Neuroplasticity is gaining popularity as a theory that, at least in
part, explains improvements in functional outcomes with physical therapy
post stroke. Rehabilitation techniques that have evidence to suggest
cortical reorganization as the mechanism of change include
Constraint-induced movement therapy,
functional electrical stimulation, treadmill training with body weight support, and
virtual reality therapy.
Robot assisted therapy
is an emerging technique, which is also hypothesized to work by way of
neuroplasticity, though there is currently insufficient evidence to
determine the exact mechanisms of change when using this method.
[18]
Jon Kaas, a professor at
Vanderbilt University,
has been able to show "how somatosensory area 3b and ventroposterior
(VP) nucleus of the thalamus are affected by long standing unilateral
dorsal column lesions at cervical levels in macaque monkeys."
[19]
Adult brains have the ability to change as a result of injury but the
extent of the reorganization depends on the extent of the injury. His
recent research focuses on the somatosensory system, which involves a
sense of the body and its movements using many senses. Usually when
people damage the somatosensory cortex, impairment of the body
perceptions are experienced. He is trying to see how these systems
(somatosensory, cognitive, motor systems) are plastic as a result of
injury.
[19]
One of the most recent applications of neuroplasticity involves work done by a team of doctors and researchers at
Emory University, specifically Dr.
Donald Stein (who has been in the field for over three decades)
[20]
and Dr. David Wright. This is the first treatment in 40 years that has
significant results in treating traumatic brain injuries while also
incurring no known side effects and being cheap to administer.
[21]
Dr. Stein noticed that female mice seemed to recover from brain
injuries better than male mice. Also in females, he noticed that at
certain points in the estrus cycle females recovered even more. After
lots of research, they attributed this difference due to the levels of
progesterone. The highest level of progesterone present led to the
fastest recovery of brain injury in these mice.
They developed a treatment that includes increased levels of
progesterone injections to give to brain injured patients.
"Administration of progesterone after traumatic brain injury
[22]
(TBI) and stroke reduces edema, inflammation, and neuronal cell death,
and enhance spatial reference memory and sensory motor recovery."
[23]
In their clinical trials, they had a group of severely injured patients
that after the three days of progesterone injections had a 60%
reduction in mortality.
[21]
Sam* was in a horrific car accident that left him with marginal brain
activity; according to the doctors, he was one point away from being
brain dead. His parents decided to have him participate in Dr. Stein’s
clinical trial and he was given the three-day progesterone treatment.
Three years after the accident, he had achieved an inspiring recovery
with no brain complications and the ability to live a healthy, normal
life.
[21]
Stein has done some studies in which beneficial effects have been
seen to be similar in aged rats to those seen in youthful rats. As there
are physiological differences in the two age groups, the model was
tweaked for the elderly animals by reducing their stress levels with
increased physical contact. During surgery, anesthesia was kept at a
higher oxygen level with lower overall isoflurane percentage and "the
aged animals were given subcutaneous
lactated ringers solution post-surgery to replace fluids lost through increased bleeding."
[24] The promising results of progesterone treatments "could have a significant impact on the clinical management of TBI."
[24]
These treatments have been shown to work on human patients who receive
treatment soon after the TBI. However, Dr. Stein now focuses his
research on those persons who have longstanding traumatic brain injury
in order to determine if progesterone treatments will assist them in the
recovery of lost functions as well.
Vision
After decades in which the assumption that
binocular vision, in particular
stereopsis,
had to be achieved in early childhood lest it could never be gained, in
recent years the successful improvements in persons with
amblyopia,
convergence insufficiency or stereo vision anomalies have become prime examples of neuroplasticity; binocular vision improvements and
stereopsis recovery are now active areas of scientific and clinical research.
[25][26][27]
Treatment of learning difficulties
Michael Merzenich developed a series of "plasticity-based computer programs known as
Fast ForWord." FastForWord offers seven brain exercises to help with the language and learning deficits of
dyslexia.
In a recent study, experimental training was done in adults to see if
it would help to counteract the negative plasticity that results from
age-related cognitive decline (ARCD). The ET design included six
exercises designed to reverse the dysfunctions caused by ARCD in
cognition, memory, motor control, and so on [9]. After use of the ET
program for 8–10 weeks, there was a "significant increase in
task-specific performance."[9] The data collected from the study
indicated that a neuroplasticity-based program could notably improve
cognitive function and memory in adults with ARCD.
Neuroplasticity during operation of brain-machine interfaces
Brain-machine interface (BMI) is a rapidly developing field of
neuroscience. According to the results obtained by Mikhail Lebedev,
Miguel Nicolelis and their colleagues,
[28]
operation of BMIs results in incorporation of artificial actuators into
brain representations. The scientists showed that modifications in
neuronal representation of the monkey's hand and the actuator that was
controlled by the monkey brain occurred in multiple cortical areas while
the monkey operated a BMI. In these single day experiments, monkeys
initially moved the actuator by pushing a joystick. After mapping out
the motor neuron ensembles, control of the actuator was switched to the
model of the ensembles so that the brain activity, and not the hand,
directly controlled the actuator. The activity of individual neurons and
neuronal populations became less representative of the animal's hand
movements while representing the movements of the actuator. Presumably
as a result of this adaptation, the animals could eventually stop moving
their hands yet continue to operate the actuator. Thus, during BMI
control, cortical ensembles plastically adapt, within tens of minutes,
to represent behaviorally significant motor parameters, even if these
are not associated with movements of the animal's own limb.
Active laboratory groups include those of
John Donoghue at Brown,
Richard Andersen at Caltech,
Krishna Shenoy at Stanford,
Nicholas Hatsopoulos of University of Chicago,
Andy Schwartz at
University of Pittsburgh,
Sandro Mussa-Ivaldi at Northwestern and
Miguel Nicolelis
at Duke. Donoghue and Nicolelis' groups have independently shown that
animals can control external interfaces in tasks requiring feedback,
with models based on activity of cortical neurons, and that animals can
adaptively change their minds to make the models work better. Donoghue's
group took the implants from Richard Normann's lab at Utah (the "Utah"
array), and improved it by changing the insulation from polyimide to
parylene-c, and commercialized it through the company
Cyberkinetics. These efforts are the leading candidate for the first human trials on a broad scale for motor cortical implants to help
quadriplegic or
locked-in patients communicate with the outside world.
Sensory prostheses
Neuroplasticity is involved in the development of sensory function.
The brain is born immature and it adapts to sensory inputs after birth.
In the auditory system, congenital hearing impairment, a rather frequent
inborn condition affecting 1 of 1000 newborns, has been shown to affect
auditory development, and implantation of a sensory prostheses
activating the auditory system has prevented the deficits and induced
functional maturation of the auditory system
[29]
Due to a sensitive period for plasticity, there is also a sensitive
period for such intervention within the first 2–4 years of life.
Consequently, in prelingually deaf children, early
cochlear implantation as a rule allows to learn mother language and acquire acoustic communication.
[30]
Phantom limbs
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.
The experience of
Phantom limbs
is a phenomenon in which a person continues to feel pain or sensation
within a part of their body which has been amputated. This is strangely
common, occurring in 60-80% of amputees.
[31] An
explanation
for this refers to the concept of neuroplasticity, as the cortical maps
of the removed limbs are believed to have become engaged with the area
around them in the
postcentral gyrus.
This results in activity within the surrounding area of the cortex
being misinterpreted by the area of the cortex formerly responsible for
the amputated limb.
The relationship between phantom limbs and neuroplasticity is a
complex one. In the early 1990s V.S. Ramachandran theorized that phantom
limbs were the result of cortical remapping. However, in 1995 Herta
Flor and her colleagues demonstrated that cortical remapping occurs only
in patients who have phantom pain.
[32]
Her research showed that phantom limb pain (rather than referred
sensations) was the perceptual correlate of cortical reorganization.
[33] This phenomenon is sometimes referred to as maladaptive plasticity.
In 2009 Lorimer Moseley and Peter Brugger carried out a remarkable
experiment in which they encouraged arm amputee subjects to use visual
imagery to contort their phantom limbs into impossible configurations.
Four of the seven subjects succeeded in performing impossible movements
of the phantom limb. This experiment suggests that the subjects had
modified the neural representation of their phantom limbs and generated
the motor commands needed to execute impossible movements in the absence
of feedback from the body.
[34]
The authors stated that:"In fact, this finding extends our
understanding of the brain's plasticity because it is evidence that
profound changes in the mental representation of the body can be induced
purely by internal brain mechanisms--the brain truly does change
itself."
Chronic Pain
Main article:
Chronic pain
Individuals who suffer from chronic pain experience prolonged pain at
sites that may have been previously injured, yet are otherwise
currently healthy. This phenomenon is related to neuroplasticity due to a
maladaptive reorganization of nervous system, both peripherally and
centrally. During the period of tissue damage,
noxious stimuli and
inflammation cause an elevation of nociceptive input from the periphery to the central nervous system. Prolonged
nociception from periphery will then elicit a neuroplastic response at the cortical level to change its
somatotopic organization for the painful site, inducing
central sensitization.
[35] For instance, individuals experiencing
complex regional pain syndrome
demonstrate a diminished cortical somatotopic representation of the
hand contralaterally as well as a decreased spacing between the hand and
the mouth.
[36] Additionally, chronic pain has been reported to significantly reduce the volume of
grey matter in the brain globally, and more specifically at the
prefrontal cortex and right
thalamus.
[37]
However, following treatment, these abnormalities in cortical
reorganization and grey matter volume are resolved, as well as their
symptoms. Similar results have been reported for phantom limb pain,
[38] chronic low back pain[39] and
carpal tunnel syndrome.
[40]
Meditation
A number of studies have linked meditation practice to differences in
cortical thickness or density of gray matter. One of the most
well-known studies to demonstrate this was led by
Sara Lazar, from Harvard University, in 2000.
[41] Richard Davidson, a neuroscientist at the
University of Wisconsin, has led experiments in cooperation with the
Dalai Lama
on effects of meditation on the brain. His results suggest that
long-term, or short-term practice of meditation results in different
levels of activity in brain regions associated with such qualities as
attention,
anxiety,
depression,
fear,
anger,
the ability of the body to heal itself, and so on. These functional
changes may be caused by changes in the physical structure of the brain.
[42][43][44][45]
Fitness and exercise
In a 2009 study, scientists made two groups of mice swim a water
maze, and then in a separate trial subjected them to an unpleasant
stimulus to see how quickly they would learn to move away from it. Then,
over the next four weeks they allowed one group of mice to run inside
their rodent wheels, an activity most mice enjoy, while they forced the
other group to work harder on minitreadmills at a speed and duration
controlled by the scientists. They then tested both groups again to
track their learning skills and memory. Both groups of mice improved
their performances in the water maze from the earlier trial. But only
the extra-worked treadmill runners were better in the avoidance task, a
skill that, according to neuroscientists, demands a more complicated
cognitive response.
[46]
The mice who were forced to run on the treadmills showed evidence of
molecular changes in several portions of their brains when viewed under a
microscope, while the voluntary wheel-runners had changes in only one
area. "Our results support the notion that different forms of exercise
induce neuroplasticity changes in different brain regions," Chauying J.
Jen, a professor of physiology and an author of the study, said.
[47]
Human echolocation
Human echolocation is a learned ability for humans to sense their environment from echoes. This ability is used by some
blind people to navigate their environment and sense their surroundings in detail. Studies in 2010
[48] and 2011
[49] using
Functional magnetic resonance imaging
techniques have shown that parts of the brain associated with visual
processing are adapted for the new skill of echolocation. Studies with
blind patients, for example, suggest that the click-echoes heard by
these patients were processed by brain regions devoted to vision rather
than audition.
[50]
Etymology
Plasticity was first applied to behavior in 1890 by
William James in
The Principles of Psychology,
[51] though the idea was largely neglected for the next fifty years
[citation needed]. The first person to use the term
neural plasticity appears to have been the Polish neuroscientist
Jerzy Konorski.
[52]
Given the central importance of neuroplasticity, an outsider would be
forgiven for assuming that it was well defined and that a basic and
universal framework served to direct current and future hypotheses and
experimentation. Sadly, however, this is not the case. While many
neuroscientists use the word neuroplasticity as an umbrella term it
means different things to different researchers in different subfields
... In brief, a mutually agreed upon framework does not appear to exist.[53]
History
Proposal
Until around the 1970s, an accepted idea across neuroscience was that
the nervous system was essentially fixed throughout adulthood, both in
terms of brain functions, as well as the idea that it was impossible for
new
neurons to develop after birth.
[54]
In 1793, Italian anatomist Michele Vicenzo Malacarne described
experiments in which he paired animals, trained one of the pair
extensively for years, and then dissected both. He discovered that the
cerebellums of the trained animals were substantially larger. But, these
findings were eventually forgotten.
[55] The idea that the brain and its functions are not fixed throughout adulthood was proposed in 1890 by
William James in
The Principles of Psychology, though the idea was largely neglected.
[51]
Research and discovery
In 1923,
Karl Lashley conducted experiments on
rhesus monkeys
which demonstrated changes in neuronal pathways, which he concluded to
be evidence of plasticity, although despite this, as well as further
examples of research suggesting this, the idea of neuroplasticity was
not widely accepted by neuroscientists. However, more significant
evidence began to be produced in the 1960s and after, notably from
scientists including
Paul Bach-y-Rita,
Michael Merzenich along with
Jon Kaas, as well as several others.
[54][56]
In the 1960s,
Paul Bach-y-Rita
invented a device that allowed blind people to read, perceive shadows,
and distinguish between close and distant objects. This "machine was one
of the first and boldest applications of neuroplasticity."
[11]
The patient sat in an electrically stimulated chair that had a large
camera behind it which scanned the area, sending electrical signals of
the image to four hundred vibrating stimulators on the chair against the
patient’s skin. The six subjects of the experiment were eventually able
to recognize a picture of the supermodel Twiggy.
[11]
It must be emphasized that these people were congenitally blind and
had previously not been able to see. Bach-y-Rita believed in
sensory substitution;
if one sense is damaged, your other senses can sometimes take over. He
thought the skin and its touch receptors could act as a retina (using
one sense for another
[57]).
In order for the brain to interpret tactile information and convert it
into visual information, it has to learn something new and adapt to the
new signals. The brain's capacity to adapt implied that it possessed
plasticity. He thought, "We see with our brains, not with our eyes."
[11]
A tragic stroke that left his father paralyzed inspired Bach-y-Rita
to study brain rehabilitation. His brother, a physician, worked
tirelessly to develop therapeutic measures which were so successful that
the father recovered complete functionality by age 68 and was able to
live a normal, active life which even included mountain climbing. "His
father’s story was firsthand evidence that a ‘late recovery’ could occur
even with a massive lesion in an elderly person."
[11] He found more evidence of this possible brain reorganization with
Shepherd Ivory Franz's work.
[58]
One study involved stroke patients who were able to recover through the
use of brain stimulating exercises after having been paralyzed for
years. "Franz understood the importance of interesting, motivating
rehabilitation: ‘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)."
[59] This notion has led to motivational rehabilitation programs that are used today.
Michael Merzenich
is a neuroscientist who has been one of the pioneers of neuroplasticity
for over three decades. He has made some of "the most ambitious claims
for the field - that brain exercises may be as useful as drugs to treat
diseases as severe as schizophrenia - that plasticity exists from cradle
to the grave, and that radical improvements in cognitive functioning -
how we learn, think, perceive, and remember are possible even in the
elderly."
[11] Merzenich’s work was affected by a crucial discovery made by
David Hubel and
Torsten Wiesel
in their work with kittens. The experiment involved sewing one eye shut
and recording the cortical brain maps. Hubel and Wiesel saw that 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. It was"… as though the brain didn’t want to waste any ‘cortical
real estate’ and had found a way to rewire itself."
[11]
This implied neuroplasticity during the critical period. However,
Merzenich argued that neuroplasticity could occur beyond the critical
period. His first encounter with adult plasticity came when he was
engaged in a postdoctoral study with Clinton Woosley. The experiment was
based on observation of what occurred in the brain when one peripheral
nerve was cut and subsequently regenerated. The two scientists
micromapped the hand maps of monkey brains before and after cutting a
peripheral nerve and sewing the ends together. Afterwards, the hand map
in the brain that was expected to be jumbled was nearly normal. This was
a substantial breakthrough. Merzenich asserted that "if the brain map
could normalize its structure in response to abnormal input, the
prevailing view that we are born with a hardwired system had to be
wrong. The brain had to be plastic."
[11]
See also
Trauma:
References
- Jump up ^ Pascual-Leone,
A., Freitas, C., Oberman, L., Horvath, J. C., Halko, M., Eldaief, M. et
al. (2011). Characterizing brain cortical plasticity and network
dynamics across the age-span in health and disease with TMS-EEG and
TMS-fMRI. Brain Topography, 24, 302-315. doi 10.1007/s10548-011-0196-8
- Jump up ^ Pascual-Leone,
A., Amedi, A., Fregni, F., & Merabet, L. B. (2005). The plastic
human brain cortex. Annual Review of Neuroscience, 28, 377-401. doi
10.1146/annurev.neuro.27.070203.144216
- ^ Jump up to: a b Rakic, P. (January 2002). "Neurogenesis in adult primate neocortex: an evaluation of the evidence". Nature Reviews Neuroscience 3 (1): 65–71. doi:10.1038/nrn700. PMID 11823806.
- Jump up ^ Hubel,
D.H.; Wiesel, T.N. (February 1, 1970). "The period of susceptibility to
the physiological effects of unilateral eye closure in kittens". The Journal of Physiology 206 (2): 419–436. PMC 1348655. PMID 5498493.
- ^ Jump up to: a b Ponti,
Giovanna; Peretto, Paolo; Bonfanti, Luca; Reh, Thomas A. (2008).
"Genesis of Neuronal and Glial Progenitors in the Cerebellar Cortex of
Peripuberal and Adult Rabbits". In Reh, Thomas A. PLoS ONE 3 (6): e2366. doi:10.1371/journal.pone.0002366. PMC 2396292. PMID 18523645.
- Jump up ^ Chaney, Warren, Dynamic Mind, 2007, Las Vegas, Houghton-Brace Publishing, pp 33-35, ISBN 0-9793392-0-0 [1]
- Jump up ^ Chaney, Warren, Workbook for a Dynamic Mind, 2006, Las Vegas, Houghton-Brace Publishing, page 44, ISBN 00979339219 [2]
- Jump up ^ Buonomano, Dean V.; Merzenich, Michael M. (March 1998). "CORTICAL PLASTICITY: From Synapses to Maps". Annual Review of Neuroscience 21: 149–186. doi:10.1146/annurev.neuro.21.1.149. PMID 9530495.
- Jump up ^ Merzenich, M.M.; Nelson, R.J.; Stryker, M.P.; Cynader, M.S.; Schoppmann, A.; Zook, J.M. (1984). "Somatosensory Cortical Map Changes Following Digit Amputation in Adult Monkeys". Journal of Comparative Neurology 224: 591–605.
- Jump up ^ Wall,
J.T.; Xu, J.; Wang, X. (September 2002). "Human brain plasticity: an
emerging view of the multiple substrates and mechanisms that cause
cortical changes and related sensory dysfunctions after injuries of
sensory inputs from the body". Brain Research Reviews (Elsevier Science B.V.) 39 (2–3): 181–215. doi:10.1016/S0165-0173(02)00192-3. PMID 12423766.
- ^ Jump up to: a b c d e f g h i j k Doidge, Norman (2007). The Brain That Changes Itself: Stories of Personal Triumph from the frontiers of brain science. New York: Viking. ISBN 978-0-670-03830-5.
- Jump up ^ Interview with Merzenich, 2004
- Jump up ^ Draganski et al. "Temporal and Spatial Dynamics of Brain Structure Changes during Extensive Learning" The Journal of Neuroscience, June 7, 2006, 26(23):6314-6317
- Jump up ^ "Remembering Leaders in the Field of Blindness and Visual Impairment." National Center for Leadership in Visual Impairment. Salus University. 20 Nov. 2008
- Jump up ^ "BrainPort, Dr. Paul Bach-y-Rita, and ... - Mind States - tribe.net". Mindstates.tribe.net. 2005-03-30. Retrieved 2010-06-12.
- Jump up ^ "Wisconsin Alumni Association - Balancing Act". Uwalumni.com. Retrieved 2010-06-12.
- ^ Jump up to: a b Frost, S.B.; Barbay, S.; Friel, K.M.; Plautz, E.J.; Nudo, R.J. (2003). "Reorganization of Remote Cortical Regions After Ischemic Brain Injury: A Potential Substrate for Stroke Recovery". Journal of Neurophysiology 89 (6): 3205–3214. doi:10.1152/jn.01143.2002. PMID 12783955.
- Jump up ^ Young J. A., Tolentino M. (2011). "Neuroplasticity and its Applications for Rehabilitation". American Journal of Therapeutics 18: 70–80.
- ^ Jump up to: a b Jain,
Neeraj; Qi, HX; Collins, CE; Kaas, JH (October 22, 2008). "Large-Scale
Reorganization in the Somatosensory Cortex and Thalamus after Sensory
Loss in Macaque Monkeys". The Journal of Neuroscience 28 (43): 11042–11060. doi:10.1523/JNEUROSCI.2334-08.2008. PMC 2613515. PMID 18945912.
- Jump up ^ "Coulter Department of Biomedical Engineering: BME Faculty". Bme.gatech.edu. Retrieved 2010-06-12.
- ^ Jump up to: a b c Stein, Donald. "Plasticity." Personal interview. Alyssa Walz. 19 Nov. 2008.
- Jump up ^ Traumatic Brain Injury (a story of TBI and the results of ProTECT using progesterone treatments) Emory University News Archives
- Jump up ^ Cutler,
Sarah M.; Hoffman, Stuart W.; Pettus, Edward H.; Stein, Donald G.
(October 2005). "Tapered progesterone withdrawal enhances behavioral and
molecular recovery after traumatic brain injury". Experimental Neurology (Elsevier) 195 (2): 423–429. doi:10.1016/j.expneurol.2005.06.003. PMID 16039652.
- ^ Jump up to: a b Cutler,
Sarah M.; Cekic, Milos; Miller, Darren M.; Wali, Bushra; VanLandingham,
Jacob W.; Stein, Donald G. (September 24, 2007). "Progesterone Improves
Acute Recovery after Traumatic Brain Injury in the Aged Rats". Journal of Neurotrauma 24 (9): 1475–1486. doi:10.1089/neu.2007.0294. PMID 17892409.
- Jump up ^ Dominick M. Maino: Neuroplasticity: Teaching an Old Brain New Tricks, Review of Optometry, January 2009
- Jump up ^ Indu
Vedamurthy; Samuel J. Huang; Dennis M. Levi; Daphne Bavelier; David C.
Knill (27 December 2012). "Recovery of stereopsis in adults through
training in a virtual reality task". Journal of Vision 12 (14). doi:10.1167/12.14.53. Article 53
- Jump up ^ Robert
F. Hess; Benjamin Thompson (February 2013). "New insights into
amblyopia: binocular therapy and noninvasive brain stimulation". Journal of AAPOS 17 (1). pp. 89–93. doi:10.1016/j.jaapos.2012.10.018.
- Jump up ^ Lebedev,
Mikhail A.; Carmena, Jose M.; O'Doherty, Joseph E.; Zacksenhouse,
Miriam; Henriquez, Craig S.; Principe, Jose C.; Nicolelis, Miguel A. L.
(May 11, 2005). "Cortical Ensemble Adaptation to Represent Velocity of an Artificial Actuator Controlled by a Brain-Machine Interface". The Journal of Neuroscience 25 (19): 4681–4693. doi:10.1523/JNEUROSCI.4088-04.2005. PMID 15888644. Retrieved 2010-01-31.
- Jump up ^ Kral A, Sharma A (2012). "Developmental Neuroplasticity after Cochlear Implantation". Trends Neurosci 35 (2): 111–122.
- Jump up ^ Kral A, O'Donoghue GM. Profound Deafness in Childhood. New England J Medicine 2010: 363; 1438-50
- Jump up ^ Beaumont,
Geneviève; Mercier, Pierre-Emmanuel, Malouin, Jackson (2011).
"Decreasing phantom limb pain through observation of action and imagery:
A case series". Pain Medicine 12 (2): 289–299. doi:10.1111/j.1526-4637.2010.01048.x.
- Jump up ^ Flor H, Elbert T, Knecht S, Wienbruch C, Pantev C, Birbaumer N et al. (1995). "Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation". Nature 375: 482–484.
- Jump up ^ Flor H, Cortical Reorganization And Chronic Pain: Implications For Rehabilitation, J Rehabil Med, 2003, Suppl.41:66-72
- Jump up ^ Moseley,
Brugger, Interdependence of movement and anatomy persists when amputees
learn a physiologically impossible movement of their phantom limb,
PNAS, Sept 16, 2009,[3]
- Jump up ^ Seifert,
F. & Maihöfner, C. Functional and structural imaging of
pain-induced neuroplasticity. Current Opinion in Anaesthesiology 2011;
24: 515–523.
- Jump up ^ Maihöfner
C., Handwerker H.O., Neundorfer B., Birklein F. Patterns of cortical
reorganization in complex regional pain syndrome" Neurology 2003; 61:1707–1715.
- Jump up ^ Apkarian A.V., Sosa Y., Sonty S et al. (2004). "Chronic back pain is associated with decreased prefrontal and thalamic gray matter density". J Neurosci 24: 10410–10415.
- Jump up ^ Karl A., Birbaumer N., Lutzenberger W. et al. (2001). "Reorganization of motor and somatosensory cortex in upper extremity amputees with phantom limb pain". J Neurosci 21: 3609–18.
- Jump up ^ Flor H., Braun C., Elbert T., et al. Extensive reorganization of primary somatosensory cortex in chronic back pain patients. Neurosci Lett 1997;224:5–8.
- Jump up ^ Napadow V., Kettner N., Ryan A. et al. (2006). "Somatosensory cortical plasticity in carpal tunnel syndrome: a cross-sectional fMRI evaluation". Neuroimage 31: 520–530.
- Jump up ^ Lazar,
S.; Kerr, C.; Wasserman, R.; Gray, J.; Greve, D.; Treadway, Michael T.;
McGarvey, Metta; Quinn, Brian T. et al. (2005-11-28). "Meditation
experience is associated with increased cortical thickness". NeuroReport 16 (17): 1893–97. doi:10.1097/01.wnr.0000186598.66243.19. PMC 1361002. PMID 16272874.
- Jump up ^ Lutz, A.; Greischar, L.L.; Rawlings, N.B.; Ricard, M.; Davidson, R. J. (2004-11-16). "Long-term meditators self-induce high-amplitude gamma synchrony during mental practice". PNAS 101 (46): 16369–73. doi:10.1073/pnas.0407401101. PMC 526201. PMID 15534199. Retrieved 2007-07-08
- Jump up ^ Sharon Begley (20 Jan 2007). "How Thinking Can Change the Brain". Wall Street Journal.
- Jump up ^ Davidson, Richard; Lutz, Antoine (January 2008). "Buddha's Brain: Neuroplasticity and Meditation". IEEE Signal Processing Magazine
- Jump up ^ Chris Frith (17 February 2007). "Stop meditating, start interacting". New Scientist.
- Jump up ^ Liu Yu-Fan, Chen Hsuin-ing, Wul Chao-Liang, Kuol Yu-Min, Yu Lung, Huang A-Min, Wu Fong-Sen, Chuang Jih-Ing, Jen Chauying J. et al.
(2009). "Differential effects of treadmill running and wheel running on
spatial or aversive learning and memory: Roles of amygdalar
brain-derived neurotrophic factor and synaptotagmin I.". Journal of Physiology 587 (13): 3221–3231. doi:10.1113/jphysiol.2009.173088.
- Jump up ^ Gretchen Reynolds (16 September 2009). "Phys Ed: What Sort of Exercise Can Make You Smarter?". New York Times.
- Jump up ^ Human Echolocation, Journal of Vision August 13, 2010 vol. 10 no. 7 article 1050 http://www.journalofvision.org/content/10/7/1050.abstract
- Jump up ^ Neural Correlates of Natural Human Echolocation in Early and Late Blind Echolocation Experts,PLoS One, May 25, 2011, doi:10.1371/journal.pone.0020162, http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0020162
- Jump up ^ Thaler,
L; Arnot, S.R., Goodale, M.A (2011). "Neural correlates of natural
human echolocation in early and late blind echolocation experts". Public Library of Science 6 (5).
- ^ Jump up to: a b "The Principles of Psychology", William James 1890, Chapter IV, Habits
- Jump up ^ LeDoux, Joseph E. (2002). Synaptic self: how our brains become who we are. New York, United States: Viking. p. 137. ISBN 0-670-03028-7.
- Jump up ^ Shaw, Christopher; McEachern, Jill, eds. (2001). Toward a theory of neuroplasticity. London, England: Psychology Press. ISBN 978-1-84169-021-6.
- ^ Jump up to: a b Meghan O'Rourke Train Your Brain April 25, 2007
- Jump up ^ Rosenzweig, Mark R. (1996). "Aspects of the search for neural mechanisms of memory". Annual Review of Psychology 47: 1–32. doi:10.1146/annurev.psych.47.1.1. PMID 8624134.
- Jump up ^ Brain Science Podcast Episode #10, "Neuroplasticity"
- Jump up ^ "Wired Science . Video: Mixed Feelings". PBS. Retrieved 2010-06-12.
- Jump up ^ "Shepherd Ivory Franz". Rkthomas.myweb.uga.edu. Retrieved 2010-06-12.
- Jump up ^ Colotla, Victor A.; Bach-y-Rita, Paul (2002). "Shepherd Ivory Franz: His contributions to neuropsychology and rehabilitation". Cognitive, Affective & Behavioral Neuroscience 2 (2): 141–148. doi:10.3758/CABN.2.2.141.
Further reading
- Pinaud, Raphael; Tremere, Liisa A.; De Weerd, Peter, eds. (2006). Plasticity in the visual system: from genes to circuits. New York: Springer. ISBN 978-0-387-28190-2.
- Pinaud, Raphael; Tremere, Liisa A., eds. (2006). Immediate early genes in sensory processing, cognitive performance and neurological disorders. New York: Springer. ISBN 978-0-387-33603-9.
- Begley, Sharon (November 5, 2004). "Scans of Monks' Brains Show Meditation Alters Structure, Functioning". The Wall Street Journal (Washington D.C.). p. B1.
- Donoghue, John P. (2002). "Connecting cortex to machines: recent advances in brain interfaces". Nature Neuroscience 5: 1085–1088. doi:10.1038/nn947. PMID 12403992. Retrieved 2010-02-01.
- Flor, H. (July 2002). "Phantom-limb pain: characteristics, causes, and treatment". The Lancet Neurology (Elsevier) 1 (3): 182–189. doi:10.1016/S1474-4422(02)00074-1.
- Ramachandran, Vilayanur S.; Hirstein, William (1998). "The perception of phantom limbs. The D. O. Hebb lecture" (PDF). Brain 121 (9): 1603–1630. doi:10.1093/brain/121.9.1603. PMID 9762952. Retrieved 2010-01-31.
- Cohen, Wendy; Hodson, Ann; O'Hare,
Anne; Boyle, James; Durrani, Tariq; McCartney, Elspeth; Mattey, Mike;
Naftalin, Lionel et al. (June 2005). "Effects of Computer-Based
Intervention Through Acoustically Modified Speech (Fast ForWord) in
Severe Mixed Receptive-Expressive Language Impairment: Outcomes From a
Randomized Controlled Trial". Journal of Speech, Language, and Hearing Research 48 (3): 715–729. doi:10.1044/1092-4388(2005/049).
- Giszter, Simon F. (January 2008). "SCI: Present and Future Therapeutic Devices and Prostheses". Neurotherapeutics (Elsevier) 5 (1): 147–162. doi:10.1016/j.nurt.2007.10.062. PMC 2390875. PMID 18164494.
- Mahncke, Henry W.; Connor, Bonnie B.;
Appelman, Jed; Ahsanuddin, Omar N.; Hardy, Joseph L.; Wood, Richard A.;
Joyce, Nicholas M.; Boniske, Tania et al. (August 15, 2006). "Memory
enhancement in healthy older adults using a brain plasticity-based
training program: A randomized, controlled study". Proceedings of the National Academy of Sciences of the United States of America 103 (33): 12523–12528. doi:10.1073/pnas.0605194103. PMC 1526649. PMID 16888038.
- Stein, Donald G.; Hoffman, Stuart W. (July/August 2003). "Concepts of CNS Plasticity in the Context of Brain Damage and Repair". Journal of Head Trauma Rehabilitation 18 (4): 317–341. doi:10.1097/00001199-200307000-00004. PMID 16222128.
- Nudo, Randolph J.; Milliken, Garrett
W. (1996). "Reorganization of Movement Representations in Primary Motor
Cortex Following Focal Ischemic Infarct in Adult Squirrel Monkeys". Journal of Neurophysiology 75 (5): 2144–149. PMID 8734610.
- Wieloch, Tadeusz; Nikolich, Karoly (June 2006). "Mechanisms of neural plasticity following brain injury". Current Opinion in Neurobiology 16 (3): 258–264. doi:10.1016/j.conb.2006.05.011. PMID 16713245.
- Videos
- Other readings
- Chorost, Michael (2005). Rebuilt: how becoming part computer made me more human. Boston: Houghton Mifflin. ISBN 0-618-37829-4.
External links
No comments:
Post a Comment