Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, I'm
Speaker 1: Christian Sager, and welcome to brain stuff. A lot of
Speaker 1: things are easy to remember. My high school graduation, for instance,
Speaker 1: or my first summer job, or that time I got
Speaker 1: arrested for emptying a bunch of jello packets into Brian
Speaker 1: Kranston's gas tank. It's it's a long story, but it
Speaker 1: doesn't take a scientist to notice that adults don't generally
Speaker 1: remember things that happened before the age of about three
Speaker 1: or four. Why is that, well, why can't we remember
Speaker 1: the earliest events in our lives up to an including birth. Okay,
Speaker 1: here's an experiment. Try to remember what happened the last
Speaker 1: time you ate a burrito? Where were you? Who was
Speaker 1: with you? Was the burrito full of spiders? These kind
Speaker 1: of memories, being able to recall details of a particular
Speaker 1: event in the past, are called episodic memories. A person
Speaker 1: at age sixty will usually have some episode memories from
Speaker 1: age thirty. She might not get all the details right,
Speaker 1: but she will be able to recall some events and
Speaker 1: explain what happened. But if you take that same person
Speaker 1: at age thirty and ask her to describe something that
Speaker 1: happened to her during her first year of life. You'll
Speaker 1: typically get nothing at all. Sigmund Freud referred to this
Speaker 1: whole in our memory as childhood amnesia or infantile amnesia.
Speaker 1: Freud being Freud explained it by saying we needed to
Speaker 1: repress memories from infancy because of their inappropriate or traumatic
Speaker 1: sexual content. But sometimes a blank is just a blank,
Speaker 1: and contemporary scientists don't tend to throw in with Freud
Speaker 1: on this one. Another hypothesis that used to be popular
Speaker 1: says that babies can't form episodic memories until they develop
Speaker 1: certain cognitive capacities, like language. But there's a major problem
Speaker 1: with the language based hypothesis. Experiments have shown that animals
Speaker 1: like mice also display both long term memory and infantile amnesia.
Speaker 1: Since childhood amnesia across his species lines, it is probably
Speaker 1: something to do with brain biology rather than language. One
Speaker 1: possible answer would be to say that baby brains simply
Speaker 1: can't make memories. It's true that memory and coding isn't
Speaker 1: as efficient in infant brains as it is in the
Speaker 1: brains of older children or adults, possibly because the prefrontal
Speaker 1: cortex of a baby's brain hasn't reached maturity yet, but
Speaker 1: recent studies have shown that very young children can form
Speaker 1: some memories, leading scientists to think it's not that we
Speaker 1: don't make memories early in life, but that after a
Speaker 1: certain point we can't access them. The memories are made,
Speaker 1: but something happens to them they get erased or put
Speaker 1: behind some kind of memory blockade. Patricia Bauer and Marina
Speaker 1: Larkina of Emory University have led research on this hypothesis.
Speaker 1: For example, in one study, researchers recorded children at age
Speaker 1: three describing a recent event, like a trip to a
Speaker 1: theme park. Years later, the researchers followed up with these
Speaker 1: same children to see how much they remembered, and at
Speaker 1: ages five, six, and seven, the children could recall more
Speaker 1: than sixty of the earlier events, but by ages eight
Speaker 1: and nine, their recall was less than More research of
Speaker 1: this kind is needed, but this looks like watching the
Speaker 1: onset of childhood amnesia as it happens. Another recent study
Speaker 1: has considered the role of neurogenesis in the hippocampus. The
Speaker 1: hippocampus is a part of the brain that's crucial for
Speaker 1: creating and storing episodic memories. If you don't have either
Speaker 1: of your hippocampy, you could end up like that guy
Speaker 1: in Memento, unable to make new episodic memories. Neuroscientists Shina
Speaker 1: Jocelyn and Paul Franklin have proposed a theory that childhood
Speaker 1: amnesia happens because of rapid formation of new cells in
Speaker 1: the hippocampus when children are young. This is known as
Speaker 1: hippocampal neurogenesis. Basically, while your brain is manufacturing lots of
Speaker 1: the cells you will use to make memories for the
Speaker 1: rest of your life, it wipes away or obscures the
Speaker 1: memories you already created as a young child. Check out
Speaker 1: the brainstuff channel on YouTube, and for more on this
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