I’m going to show you a series of numbers, and you need to recall them when I ask.
Ready?
6,3,4,7,1,5,2.
This is a picture of my dog, who in my opinion is ridiculously good looking.
Do you remember the series of numbers?
If you got all 7, in the right order, your working memory is, well, working.
But there’s someone who would have trouble repeating those numbers.
He’s renowned for having a terrible memory.
This is Henry Molaison, also known as Patient H.M., one of the most famous patients in brain
science.
As a child, H.M.
hit his head and began having seizures.
They became worse and worse as he got older.
When he was 27, H.M. had surgery and the part of his temporal lobe that included his hippocampus
was sucked out of his head.
It was the early 1950s and no one was certain what would happen next.
H.M.’s seizures stopped, but he became forgetful.
He couldn’t retain some information and couldn’t recall the few years before the
surgery.
Researchers were puzzled–he remembered some things, but not others.
So they studied H.M. to try to piece together his behaviour.
Without his hippocampus, H.M.
couldn’t couldn’t store declarative memories — our memories for facts like a phone number
or dog breed.
But he could retain procedural memories — those for learning a skill, like riding a bike.
H.M.
kept repeating a task where, only using a mirror to see the reflection of his hand,
he’d draw a shape in between two lines.
His motor skills doing the task kept improving, even though he had no memory of completing
it before.
Researchers discovered there were these different types of memory.
And that they relied on different areas of our brain.
When we form declarative memories, the information travels to the hippocampus before it’s consolidated
and permanently stored.
And when we form procedural memories, they rely on other areas, the cerebellum and basal
ganglia.
Without a hippocampus, H.M.
was missing a pretty important piece.
The case of H.M.
helped us understand the nature of memory, that there are different types of it that
rely on different parts of your brain.
His brain was such a big deal that in 2009, after he passed away, it was cut up into 2,401
paper-thin slices and reconstructed into a 3D model.
It’s over 60 years since he first had his hippocampus sucked out of his brain and we’re
still learning from H.M.
And one last thing!
Do you remember that series of numbers?
Go on…
If you forgot, 6,3,4,7,1,5,2.
And don’t worry.
H.M wouldn’t even remember being asked in the first place.
And um, here’s another picture of my dog.
In case you remembered that.
And maybe wanted to see her again.
So good looking.
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