Download BRAIN REPAIR YOURSELF SUMMARY

Kognitionsvetenskap
(Neurokognition)
VT 2011
BRAIN REPAIR YOURSELF
By Fred H. Gage
SUMMARY
By Natalia
This article is devoted to the one of the neuroscience’s greatest discoveries:
neurogenesis – the birth of new neurons in the brain of adult birds, primates, and humans. For
almost 100 years of neuroscience’s history, the idea that the brain doesn’t change in the adult
brain dominated.
In nineties of the 20th century scientists have discovered that brain actually does
change: new cells and new connections are formed throughout lifetime. The author believes
that such plasticity offers a possible self-repair mechanism in cases of neurological diseases
and injuries or an enhancing mechanism to improve healthy brain’s abilities to think and feel.
The birth of a new brain cell is a process, not an event. Multipotent neural stem cells
divide periodically in the brain, in two main areas: the ventricles and the hippocampus. In
order to develop, either into a neuron or a glia cell, a given stem cell migrates out from the
area of influence of the other multipotent stem cells. Researchers have found, that cells that
are destined to become neurons, travel from the ventricles to the olfactory bulb. Only half of
cells will survive. It takes more than one month for a new neuron to grow up and learn how to
function and build active connections with surrounding cells. Whether the young cell becomes
neuron or glia (astrocyte, oligodendrocyte) cell depends on where in the brain and when that
young cell ends up. Mentioned-above processes are governed by naturally occurring
molecules called growth factors. Each step is regulated by different growth factors. For
example, the factor named notch as well as bone morphogenetic proteins influence either new
cell becomes neuron or glia cell. Nowadays these growth factors are under intensive research.
Scientists anticipate that in the future they will learn how to control and regulate neurogenesis
and environmental stimuli directly anywhere in the brain, not in a laboratory. By directing
neurogenesis, scientists hope to develop therapies that can prompt the brain fix itself in case
of disease or injury.
The author mentions neurological diseases such as stroke, depression, Alzheimer’s,
Parkinson’s, epilepsy, MS, ALS, even glioma and spinal injuries which could be ameliorated
by stimulating neurogenesis.
After a stroke, through the neurogenesis in the hippocampus, the brain attempts to
repair itself by building new neurons, and heal damaged area. Most of the new cells die but
some migrate to the damaged area and develop into mature neurons. The amount of the
surviving neurons is not sufficient to restore all the damage after a major stroke, but it is
believed to be sufficient enough to repair the consequences from a small stroke. Research
shows that epidermal growth factor and fibroblast growth factor might enhance repair process.
The problem is that those molecules are too large in size to be successfully transported
through the blood-brain barrier towards and into the certain brain areas.
Depression is believed to be caused by two main factors: genetic predisposition, and
chronic stress. It is known, that stress restricts the number of newly generated neurons in the
hippocampus. It has been found that available antidepressants, such as Prozac, increase
neurogenesis in experimental animals, moreover, it usually takes around one month to elevate
mood, using these drugs, the same time, is which required for neurogenesis. That has led to
the idea that depression might be partly caused by a decrease in neurogenesis in the
hippocampus. Imaging studies show, that chronically depressed patients have shrunken
hippocampus, and long term use of antidepressants boost neurogenesis in the rodents’
hippocampus.
Increasing neurogenesis might help patients with Alzheimer’s disease. Recent studies
show that genetically engineered mice which contained human genes that predispose to
Alzheimer’s, exhibited disorders in neurogenesis. There are two kinds of mutant genes: one
variation reduces the amount of the neurons in the hippocampus, and the other one reduces
the amount of dividing cells, and therefore the amount of the surviving neurons. Author hopes
that certain growth factors can fight this trend, and may be useful in fighting the disease.
One of the biggest challenge, scientists face now, is to learn more about how the
specific growth factors work and influence neurogenesis at each step of the process: the birth,
the migration to the right place in the brain, the development and maturation of newborn cells
into fully functional neurons, building active connections. In author’s opinion it is also
important to learn about where the good balance of the amount of neurogenesis production
lays – to find optimum level in stimulating neurogenesis.
In case of depression, when the reduced cell division results in cell loss, the goal is to
find a drug or develop a therapy, which increases cell proliferation. In case of some forms of
epilepsy, scientists speculate that the problem is that newborn cells migrate to wrong
locations, remain immature and contribute to miswirings in the brain, which in turn, cause
seizures. The solution here would be to learn how to redirect neurons’ migration to the right
locations. In case of the brain cancer called glioma, scientists believe that neural stem cells
originate the process where glial cells proliferate and form deadly, rapidly growing tumors.
Treatment might come from natural substances which regulate the division of those stem
cells. Identification of the growth factors which stop neural cells from dying, as well as those,
which help immature cells to grow healthy and build active connections with mature
functional neurons.
Diseases such as Parkinson’s, Huntington’s, ALS, might be the easiest targets to begin
with, due to their nature: very specific types of cells, located in the specific brain areas, die
and cause motor or cognitive symptoms. In case of MS, ALS, spinal cord injury the right
strategy may be to influence neural stem cells to grow into glial cells called
oligodenderocytes,
which
insulate
the
long
axons
between
neurons,
supporting
communication between the neurons, preventing the electrical signals from dissipating.
However, the author proposes solution which is available already to everyone today.
The experience can regulate the rate of stem cell division, the survival rate of the newborn
cells in hippocampus. Research shows, that if the adult mice are moved to the more complex
and more physically and mentally challenging environments, they will experience a
significant increase in neurogenesis. The author also emphasises that the best ways to enhance
brain function might not involve drugs but life style and habits changes. Brain, like many
other organs, responds positively to exercise, a good diet, and enough sleep.
The author also shares his vision of the future, when neurogenesis could be induced in
a controlled manner anywhere in the brain, and selective drugs could stimulate necessary
steps of neurogenesis to target specific diseases. These pharmacological therapies could be
combined with physical therapies which enhance neurogenesis and stimulate particular brain
areas to integrate with newly developed cells. The knowledge of positive correlation between
neurogenesis, exercise, and increased mental activity might motivate people to enhance their
natural ability to repair the brain, and to reduce their risks of neural disorders by changing to
healthier lifestyles and choosing mentally and physically challenging activities. He also
supposes that future architects and designers could incorporate the knowledge that
surrounding environment can affect the wiring in the brain into their work, providing people
with homes and workplaces with enriched environments, which stimulate brain function.