Kind: captions
Language: en
This sea snail called a pleia is
somewhat of a celebrity at least in the
world of memory research. It was this
lowly snail that revolutionized the way
neurobiologists like David Glansman
think of memory. But how do you give a
snail a memory? We're going to give it a
few shocks, but don't worry, it's not
going to harm the animal. It's not going
to produce any long-term damage.
Wow.
Giving it electrical shocks teaches the
alesia that the world is a dangerous
place.
How do we know it's actually learned?
We look at a reflex.
Touch the siphon of an alesia and it
triggers a defensive withdrawal reflex
here.
And I'm just going to touch the siphon
like that.
And there you see that's the reflex.
This reflex can tell scientists if the
snail has formed the memory.
The longer the gill and siphon remain
retracted, that's an indication that
it's learned what we taught it.
An aia that hasn't been given any shocks
will respond with a short-lived
contraction.
There it's out.
So what was that? 11 seconds. All right.
But an alesia that was taught to be on
guard responds much differently.
Now there's the reflex. Now, point is
that it stays tucked.
So, this guy's on a high state of alert
here.
Yeah. So, you see this siphon's just
starting to come out now.
And at 45 seconds, so it's four times as
long as the naive animal
and it's learned that there's a danger
in its environment. That's what it's
learned.
This learning is observed in its change
behavior. But scientists can also see
signs of memory in Alesia's legendary
brain. Let's just say this sea snail is
neurologically wellendowed.
It has very large, huge, some of the
biggest neurons in the world.
Its few but gigantic neurons inspired
researchers to essentially create an
allegia mini brain out of a sensory
neuron and a motor neuron. We take those
out of the animal and we put them into
cell culture and they grow together and
then we have a mini circuit, a neural
circuit.
Scientists can see on a cellular level
what happens is the mini brain forms a
memory. So what is happening?
Basically we see two things. The
syninnapse between the sensory neuron
and the motor neuron gets stronger.
When the snail gets zapped with
electricity, the neurons start
communicating differently, sending more
stronger chemical signals and receiving
more signals. This change, which can
happen quite quickly, but doesn't last
forever, corresponds to short-term
memory. but administer the shocks over a
longer period of time and the two
neurons physically change as the snail
learns.
Anatomically, we actually see the growth
of new synaptic connections between the
sensory and motor neuron.
And it's this physical change in the
neurons that is long-term memory. As the
snail learns over time, its brain is
making more and more connections so that
even when the snail gets a break from
the shocks, it will still remember them.
Besides training sea snails to be on a
high state of alert, the research on
agia has been integral in understanding
learning and memory and not just for
snails.
When you're looking at these changes in
a plesia, you're basically looking at
the bedrock of learning. Those same
processes take place in our brains.
And with the advancements in memory
research that a pleasure has already
inspired, it is most likely going to
remain in the spotlight for decades to
come.