Hi, I'm Michael Corayer and this is Psych
Exam Review. In this video we're going to
begin looking at the biology of memory.
Now in a previous video I mentioned that
memory is really complex and the models
that we have are very simplified and so
when we talk about biology here, remember
that we're just scratching the surface.
There's a lot more detail and in fact
there's a lot that's still not well
understood. In the previous video we
talked about the relationship between
emotion and memory and this makes sense
because we have strong emotional
experiences, it makes sense that we would
want to remember these. We want to learn
from them. So if you have a strong
negative emotional reaction like fear
you probably want to form a memory of
this so you can hopefully avoid a
similar situation in the future. Based
on this it shouldn't be a surprise that
the parts of the brain involved in
emotion are also involved in the
formation of memory. This brings us to
the limbic system and the part of the
limbic system that seems to be
especially important for forming new
long-term memories is the hippocampus.
You might recall that hippocampus comes
from the Greek for "seahorse" and it's
this curled structure. You have two
hippocampi, you have one on each side of
your brain. Some of the first
evidence for the role of the hippocampus
on memory formation comes from a famous
patient known as patient H.M., whose real
name was Henry Molaison. What
happened with patient H.M. was that he had
surgery to stop seizures and this
involved removing the hippocampus from
both sides of his brain, a hippocampectomy
and the result of this surgery was
that the seizures were reduced but
H.M. couldn't form new long-term memories.
His sensory memory was intact and his
short-term memory was intact, so he could
repeat a list of words for instance but
he couldn't move those words to
long-term memory. He couldn't remember
them a few minutes later. In fact he
couldn't remember that you had asked him
to remember a list of words.
This shows us that the hippocampus seems
to be crucial for forming new memories.
Now what HM suffered from is referred to
as anterograde amnesia and this refers
specifically to inability to form new
memories but H.M.'S previous memories
were intact. He could remember things
from before the surgery and so this
shows that the hippocampus might be
crucial for forming new memories but it's
not where memories are stored. It's not
the case that if you remove the
hippocampus you forget everything that
you had previously experienced. Another
interesting thing is that the
hippocampus doesn't seem to be involved
in procedural memories because HM could
still form new procedural memories.
If you give him a physical task and
he practiced it, he could get better at
it. For instance you could have a task
like trying to draw a picture, copy a
picture, looking into a mirror. This is
very hard to do, to look into a mirror
while you draw, but with practice you can
get better at it. So if HM were to
practice this task, he would get better
at it but if you asked him he wouldn't
remember practicing it. Another
patient with similar damage is patient
E.P. and I'll post a link in the video
description where you can find an interview
with E.P. We can see him interacting with
these interviewers. Now these are people
that he has met hundreds of times and
yet he can't remember their names but he
does show some sort of emotional
reaction to them. He seems like the
previous experiences have been positive
right? He seems warm and friendly to
them even though he thinks he doesn't
remember meeting them before so this
shows us this separation in long-term
memory between our explicit memory,
declarative memory, and our implicit
memory or non declarative memory.
Another famous case of memory loss is a
man named Clive Wearing and Clive Wearing
is considered to have one of the worst
cases of memory loss that's ever been
recorded. This is because Wearing
suffers from anterograde amnesia but he
also suffers from retrograde amnesia and
this refers to loss of previous
memories. In Clive Wearing's
case, he can't form new memories but he
also can't remember his past. He doesn't
remember things from his childhood or
really much of anything about his
previous life. He has some memories, he
can recognize his wife, in fact he shows
a strong emotional reaction to her each
time he sees her because he doesn't
remember that he's just seen her a few
minutes before. I'll post a link in
the
description where you can see some video
of Clive Wearing but an interesting
thing here is his procedural memories
are intact. He's lost his old
episodic memories and his old semantic
memories but he hasn't lost his
procedural memory. He can still play the
piano, obviously he can still walk and
he can still talk, so actually he still
has his memory for word meanings, and
things. He can understand and carry on a
conversation but within, you know, 30
seconds he's forgotten what you're
talking about, what you've been talking
about for the past few minutes, right? So
it's a very severe case of memory loss
and it helps to demonstrate these
different types of memory; that things
are not, you know, there's not one memory
area of the brain that stores everything
but the things are distributed and
certain types of damage can affect some
types of memory and not others. Ok, in
the next video we'll take a look at the
neural basis of memory. We'll look at how
chemical signaling between neurons might
play a role in the formation of memories.
Ok, I hope you found this helpful, if so,
please like the video and subscribe to
the channel for more. Thanks for watching!