hey Vsauce Michael here if you have a
watch or a clock nearby take a look at
it's our hand
it moves completing a trip all the way
around twice a day its motion is too
slow to see but try really look at right
now watch how far it travels in one
second okay
one Mississippi done that's it
see how far it moved well if this watch
was the Milky Way that would be about
how far we have traveled in our solar
system around our galaxy since the
invention of writing since the beginning
not of time but of our history it's a
very small distance unnoticeable for
most of humanity's existence
there hasn't been writing physical
recordings of events or ideas today of
course we have writing and we have many
different ways to physically store data
we even now have digital ones but before
writing was invented all humans had was
biological storage memories there was no
eiga pedia no phone book no library but
what there was was old people
of everyone around they've experienced
the most heard the most things had the
most thoughts even today with all this
stuff around the oldest among us remain
the libraries of things that physical
and digital libraries either don't
haven't been or can't yet Chronicle
Aeschylus famously said that memory is
the mother of wisdom but like all
storage formats individuals don't last
forever
these can be lost we can die these can
obsolesce they can still be around but
have no way to be played back or read
they can be abandoned ignored these can
also just wear out just as we can forget
or develop dementia dementia involves a
decline in cognitive skills used to
perform everyday activities 60 to 80
percent of dementia cases are
Alzheimer's the disease is associated
with the accumulation of plaques and
tangles in the brain changes accompanied
by damage to brain cells and their death
the older a person is the more likely
they are to have developed Alzheimer's
but Alzheimer's is not a part of normal
aging symptoms of Alzheimer's disease
include a decrease in the ability to
think and remember confusion about time
and place new difficulties speaking and
writing changes in mood and personality
as we fight against other diseases and
live longer lives Alzheimer's looms on
the horizon as if waiting for us to pass
the test of other challenges as a cause
of death from 2000 to 2013 many things
decreased but Alzheimer's has grown
stopping it preventing it postponing its
development in our brains long enough
that we at least die of something else
with our memories is a real goal we can
achieve your brain fits inside this
thing your skull specifically this part
back here called the brain case or the
arrow cranium it's a bone fortress
protecting an inner sanctuary called the
cranial cavity your brain sits right
here except it doesn't really sit so
much as it swims you see the brain is
incredibly fragile soft and gooey model
or toy brains tend to be made out of
rigid plastic and actual specimens used
in dissection tend to be a rubbery
because they've been affected by
chemicals like formaldehyde but real raw
fresh brains right out of someone's
brain case are soft like soft tofu
holding one like this for too long will
leave a lasting and shaped depression
for that reason the brain has to float
so it doesn't crush itself under its own
weight but it doesn't float in water
instead it floats in a special liquid
your body makes called
cerebrospinal fluid now this isn't a
whole brain this is just the cerebrum
the largest part of the brain it plays a
key role in language thought abstract
thinking awareness consciousness it
thinks it's a pretty big deal literally
it's the part of you that does speaking
anyway the outside of the cerebrum is
called the cortex cortex means bark like
tree bark or a ride or a husk if I tear
off one of the temporal lobes we can
take a closer look at this rind it's
painted in maroon here you can see its
extent it's only about two to four
millimeters thick it's often called grey
matter because it appears pinkish
yellowish gray in a real brain beneath
it is the white matter white because
although grey matter contains a lot of
cell bodies the white matter contains
mainly axons that are myelinated that
send messages from grey matter to gray
matter locations myelin is a whitish
material that insulates electric
messages allowing them to move faster
and fast they do move signals travel
through axons at up to 432 kilometers
per hour
that's 275 miles per hour about the top
speed of the fastest production car in
the world you can say this car literally
travels at the speed of thought but
that's slow compared to the speed of
electricity through a conductor which is
closer to 50 to 99% the speed of light
anyway
the brain is very wrinkly and that's
because a wrinkled shape allows more
cerebral cortex to fit into a smaller
container if we could take this entire
line all of your cerebral cortex flatten
it out it would be well about like this
it would be about 2 to 4 millimeters
thick and have an area equivalent to a
square 50 centimeters by 50 centimeters
about 20 by 20 inches obviously you
can't fit this shape into this shape
unless you crumple it up and now we're
getting somewhere
when we crumple the brain up we get
folds the folds are called gyri Cingular
gyrus and the crevices are called sulci
singular sulcus about two thirds of your
cerebral cortex is buried deep within
sulci out of view as for memories well
every time you learn something new or
memorize something new your brain
doesn't gain another wrinkle or anything
like that instead memories appear to be
more about connections relationships and
patterns formed by connected neurons
when neurons fire together again and
again rehearse their connections and
bonds become stronger they become more
likely to fire together again to be
recalled roughly that might be how
memory works and it's a helpful way to
think about some interesting phenomena
like the fact that it's quite difficult
to list off the name of every book
you've ever read that's like really
difficult but if someone were to just
name book titles you could effortlessly
tell them whether or not you read the
book hearing the title likely excites
neuron connections more directly
involved with the connections associated
with your memory of having read that
title
than a mere prompt to name some books
you've read when brain cells and their
connections are damaged blocked
compromised or killed memories conveyed
and the formation of new memories can be
hampered learning how this happens in
Alzheimer's isn't just important for
those diagnosed but also for all of us
interested in memory in one to five
percent of Alzheimer's cases genetic
differences can be identified but the
cause of most cases is still mostly
unknown a number of hypotheses and
observations exist for example we know
that 15% of individuals with Down
syndrome who live 40 years or longer
develop Alzheimer's disease and 50 to 70
percent of those who live to 60 do down
syndrome is caused by the presence of
all or part of a third copy of
chromosome 21 we still have a lot to
learn but chromosome 21 is also involved
in the plaques found in the brains of
people with Alzheimer's within this
chromosome are the genetic instructions
for the production of a protein called
amyloid precursor protein or AP P a P P
seems to play a role in neural growth
and repair it's found on cells
throughout the entire body it's
processed by the body in different ways
most often an enzyme called alpha secret
tastes Cleaves it into SA P P alpha and
C 83 less often an enzyme called beta
secret ace snips a P P a bit higher up
releasing a smaller fragment called
s a P P beta a third enzyme can
gamma-secretase and cleave AIC DOA
leaving p3 if alpha secret tastes active
first and beta-amyloid if beta secret
tastes acted first the normal function
of beta amyloid isn't exactly known yet
it may play an important role in healthy
brain function but if too much is made
or maybe if too little is cleared away
too slowly or if the protein folds in
the wrong ways fragments can stick
together creating oligomers groups of a
few pieces say four or five these
oligomers can then stick to other
oligomers and become larger structures
called plaques the effect oligomers and
plaques have on brain cells and brain
health is being studied oligomers may be
more toxic they may allow unregulated
ion flow into neurons causing their
deaths what we do know is that
Alzheimer's disease is associated with
these plaques in the brain as well as
another protein related anomaly tangles
a protein called tau stabilizes
microtubules in brain cells like
railroad ties holding tracks together
the tracks that guide nutrients and
other molecules throughout the cell in
many neurodegenerative diseases tau
proteins become abnormally sticky and
tangled with other tau proteins
compromising the delivery network we do
know some factors associated with
increased or decreased risk but their
exact relationships with cognitive
decline aren't all certain things
associated with a reduced risk for
Alzheimer's disease include physical
activity a heart-healthy diet learning a
second language later in life being
social frequently interacting with
people protecting your head and
intellectual activities like crossword
puzzles playing instruments reading
board games education such activities
may improve overall brain health and
cognitive skills
with a brain more resilient to damage
should it come whatever the case there's
a lot more we can learn it is incredible
and exciting and a little scary to
realize how much more we have to learn
about the brain we know more about the
orbital mechanics of distant binary
stars than we do about the very
mechanisms we use to know about them in
the first place
inner space is as mysterious and deep as
outer space and of course between the
two one doesn't even care if we exist
while the other well the other is us the
wobbly gel in our heads
no stiffer than a good booger is fragile
and still very much of a scientific
frontier
it looks like soft meat but it can not
only think reason feel remember and lie
it can also care for other people and
the goopy wrinkled things inside their
skulls it can be patient with them see
them as people no matter how they change
whether by growing up
or growing way up supporting research
caregivers and those diagnosed is
something we can all do so thank you and
as always thanks for watching
terry pratchett famously said that right
now the sword that will defeat
Alzheimer's is probably made of gold
donations resources for the last few
years
Vsauce has donated to and supported the
Alzheimer's Association they are great
people and they helped me a lot with
this video I've included links to them
in the video's description