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
