an organ that is plastic
this organ it weighs only 1 kg 5
not much compared to
our total mass
and yet he is very greedy then
if they consume about 20% of
the energy we produce each
day and it was even 50% of that
energy
when we were kids besides being
greedy this organ he is very
complex so complex that nobody
do not really understand it today
so we were still two three
stuff we know for example that it is
composed of about 200 billion
cells that are very carefully
organized between them so how
exactly is exactly what we
not understand anyway the
consequence of this organization it is
that this body he has so to speak
super powers that to make us laugh
to make us love to learn
to make us create or more modestly to
priori in any case sleep eating and
move
obviously you’ve understood this
organ it is our brain that we
can define as being greedy
complex but also plastic why
but because with its 200 billion
cells of which only 100 billion
would be neurons the brain to the
task of making sure that we at
every moment we are at our best
adapted to the situation we are
living
and for that we have our brains since
the day of our birth or even
a little bit before and yet if we
plunge back to that moment force is to
to find that we may not have
to the best of our ability and
was not able to do
to express very much something very
interesting
so we might think that our
brain was then not at all
performing
in reality she was mostly
extremely immature particularly
immature by the way if we compare
with that of our cousins the primates
so we often compare it at this time
there to a sponge that absorbs everything
who passes but more precisely that
would look like a ball of dough to
very malleable modeling and so very
plastic then we from the first
moments of our life we have
actually used this immaturity
which is synonymous with plasticity and that
it was a chance because as soon as
first experiences of our life
from the first novelties our
brains generated thousands of
new connections the synapses between
the billions of neurons that the
constitute and what will offer a
number of exchange possibilities
between these neurons that literally goes
grazed the infinite is the consequence is
that we are capable
to learn a lot of things so
in the first months at the engine level
for example we were able
to intentionally catch an object
like this little flower and then there you
liked to wait two to three months of
more so that we are able to
let go of this object just as
intentionally and then we learned
to walk some their age to football and
at the cognitive level too we went
developed at three months we started
to tweet to communicate and then we have
learned to speak we learned to read on
learned to count and then well
obviously so much more so
clearly in the first moments of
our life our brain is
completely open to full of
new experiences and the
consequence is that we learn
a lot of things
so now what’s going on
once an adult then some
people maybe some of
you think that once in your thirties
passed into our brain it becomes a
little more lazy than he a little
more rigid but ultimately it’s
maybe not so well
so it’s true that some
learning will be more laborious a
once we are grown up for example our
brain is more willing to make us
to learn Sanskrit at age 4 at age 40
it’s undeniable but we are
also more able to solve a
differential equation at 20 years
than two years old if ever we are able
to solve forever an equation
differential is still something else
in reality it is an idea that is
wrong with age our brain does not
not that losing his abilities losing his
neurons and loses its synapses
it’s an idea that’s skewed that has
had for a very long time the head
hard enough and it was even a dogma in
neuroscience and a dogma and no it’s
not by anyone but by this man
who is a spanish scientist santiago
ramon y cajal this is probably one of
who contributed the most to the
contribution of the brain he has during
years carefully studied the
structure of the nervous system he has
does magnificent inscription that
still do schools today and
in among these contributions he
determine the existence of neurons
like the one who drew it here as
being the structural unit and
functional nervous system what
was probably worth to him the reason
Nobel Prize in Physiology and Medicine
in 1906 he shared with Italian
camillo cole j
ramon y cajal written in 1928 in the
adult centers the nerve pathways are
finite fixed things is immutable all
can die but nothing can happen
regenerate
yet at the same time a woman
alice hamilton who will become moreover
the first female professor at harvard
observe the presence of what seems
to be new cells in the
brain of adult rats but there is
had no proof that these cells
were neurons so this
observation fell into oblivion
it took decades the
60s so that jo zette apps man
put the cover back is he too
observed what really seems to be
new neurons in the brain of
adult rats and he thinks
that indeed the brain keeps
this ability to generate
neurons of this neuro genesis but
that would have been limited to only two
brain regions including the hippocampus
the hippocampus is this structure that
is here tucked into no temporal love and
which is necessary for us
learn and we ourselves
horizons ie without
hippocampus one is unable to form
new memories
so the fact that there could be the
continuous birth of neurons in the
region that controls the formation of
memories it’s still a little bit
intriguing but works date man
were largely ignored and then a
little bit also considered as
heretic since it was going to
against the dogma of santiago ramon y
cajal but other observations have
continued to weaken this particular dogma
those realized by elisabeth gould
which will eventually determine in 1998 that it
is there the presence of new
neurons for sure in the hippocampus
of adult primates and it’s this same
year that the double-top for good of
researchers had the idea to study the
brain of five patients who died
following a cancer and who had
previously received the injection of a
molecule that helps to track the
cell proliferation and so
since following the amplification of
tumors well these researchers have
found this molecule in
neurons of the hippocampus of his patients
that is to say that the man
adult is still able to generate
drones in his hippocampus
that means me and you we
are still producing a
road not us
hippocampus the oldest person of
this study was 72 years old too
we could find the new neurons
in his hippocampus that means that
this neurogenesis is even at a
old age what does it matter
represents how many neurons leave
finally in our seahorses and
redon to answer this question
there are researchers who have an idea
pretty awesome
it turns out that between 1955 and 1963 to
united states it’s the cold war with
all the nuclear tests that are going
with whom will cause a very strong
increase in the concentration of
carbon 14 in the atmosphere and
researchers had the idea to go
measure the carbon 14 present in
dna neurons that are born during
this period in order to date them as
we would do it with a fossil shown
very accurate and so thanks to that they
could estimate the daily birth
hippocampal neurons in our 2400
per day
1400 new neurons in our
seahorse a day that means little
almost 60 per hour while it is
clear the dogma has fallen well ramon y
cajal on it anyway had
wrong since we produce new ones
neurons
every day among 400 it’s great but
it’s not much compared to 100
billion
so can we do anything
thing to improve this
neurogenesis but it’s simple the
parameters the main parameters
that can improve and
to optimize the neurogenesis they are
super simple to implement in our
life since it is 1 activity
physical and 2 cognitive activity
but these parameters are
interdependent and so it takes
necessarily they are
complementary and it is necessary
necessarily have both exercised
both to optimize our
neurogenesis if I place a wheel in
the rodent cage you have it all
observed they will rush in
and will start running lassabe acer
the mans well we will observe in
the seahorse of these animals over
new cells that forms in
their hippocampus only in the hippocampus
animals that did not have a wheel
but only 10% of these cells are
survive long-term
they will have the chance to become
real mature and functional neurons
so we say that physical activity
allows the proliferation of new
cells but does not allow their survival
so what can we do to
to keep these cells and make them
neurons it’s extremely simple it
must use it
you have to learn you have to see new
experience one must mix with
congeners in other words it takes
enrich our environment and that’s
donald m who did in the 40s
the first observation of these effects
beneficial of so-called
today the environment enriched everything
because they brought back the
laboratory rats at his home so he
has fun with his children and has
preview that his rattles to those who
had played with children well
he was much more successful
then in laboratory tests
like finding the exit of a labyrinth
and we know today that animals
that are placed in an environment
enriched which simply consists of
place a large group of animals in
large cages with tons of objects
we will change regularly
well these animals there in reality they
do not have more new cells that
is formed in their hippocampus
but the proportion of these cells that
will survive long-term become
true mature neurons that works
she will be greatly increased so
if I resume
you need to have an activity
physical to generate a lot of
new cells in your
seahorses and then two have a
intellectual and social activity of
so that these little cells
and the chance to become leases
nature neurons and officials who
will allow your hypocrisy as much
to work better it is necessary
for learning abilities and
of memory and especially this
called spatial memory and the
memory for textual so basically it’s
through your mortgage or also a
little bit certainly with your
phone that you will find where
you park your car out
from here then me personally I
will take the subway but I’m going to
actually use the level as for
find there the nearest station
so that’s the space memory the
contextual memory that’s all
just memorize everything that
is the context of an event
of our life then smells them
colors temperature sensations
we had at that time all that
it’s part of the context and
the hippocampus rating for that and so to
every moment in our seahorse
we have new cells that form
and it turns out that these cells its
neurons that are immature at first are
precisely particularly plastic
that is, they will
especially answer that one
stimulation more than the others so in
big there now i’m trying to
solicit more particularly in
your seahorses neurons that are
born two weeks ago and who
are even more numerous if you have
physical activity
and where it’s great hic it’s
crazy even if it’s not completely
prove that these same neurons this
are these same neurons that are
reactive round the day you
remember this presentation here of which
clearly the manipulations that
improve our new
genesis should be able to
enable the improvement of our
learning and
memory and there is a condition for
which these abilities are strongly
damaged you know all this is
Alzheimer’s disease so the mesh
of Alzheimer’s is a disease
neurodegenerative is the brain undergone
damage that is dramatic
with the loss of thousands of neurons
especially in the seahorse
hence the problems of memory and
estimate in France today at 900
thousand the number of cases of the disease
of azheimer 35 million in the world and
the oms believes that if nothing is done in
2030 65 million people will be
with Alzheimer’s disease
but is it likewise in these
extremely difficult conditions where
the brain have suffered damage that
are very heavy do they have
everything is always proof of ability
of adaptation is what he always does
proof of plasticity and do we
could not use these resources there
this plasticity to fight against this
type of pathology and so for
start answering that here at
toulouse we placed mice in a
enriched environment as I wanted
show just now but these mice
are a bit special since she
expresses a modified gene that will make
than inevitably
they will develop the disease
of Alzheimer’s with age and the question
we asked ourselves, is that what he
there is a period in the life of these
animals
that is to say a moment in the course
of pathology or being
subjected to very strong stimulation
sensory and social could
compensate for the damage related to the
pathology and so we simply
place these animals in an environment
enriched for ten weeks their
life only before and after these 10
weeks
they were in their cage a little
more sad lab but all
the mice were not the same age at
moment put them in the environment
stimulant some had three months
so it’s very young still have it
no sign of the disease
others were five months old
we start to see the first
disorders related to the pathology and then
Lastly
had ten months so there are enough
aged and she shows both
behavioral disorders and disorders
neuro pathology that looks like this
seen in Alzheimer’s patients
proved and to our surprise
we observed that animals that
had been placed for ten weeks
only in the enriched environment
at the age of three months and 5 months
well these animals there once they are old
behave exactly like mice
who did not have the pathology so the
simple done for a short time
of their life to have very strongly
boost their cognitive abilities and
their social abilities finally
enough to suppress the expression
behavioral pathology then
is that the beneficial effect of
the enriched environment here has gone
by improving the
neurogenesis or is it related
to stimulation of another type of
plasticity of our brain that’s it
what we are looking for today
determine but anyway we
is absolutely not at the end of our
surprises as to the capabilities of our
brain its plasticity abilities and
you understood him what he is
important to do is the curious that
undeniably where you are since
you are here today you have to get
serve as our brain and we can
probably eventually understand further
better how they work and
find ways to solicit this
plasticity for our brains to be
stronger more performant all our
life and above all more resistant to
pathologies and waiting for us
understand all this the message it is
simple use your brain be
curious go run go dance go
see your friends because your brain to
all this he is still plastic
that’s very good news
so enjoy it
[Applause]
”
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