3 lecture 7

Question 1

what is memory

Answer 1

a change in the number or strength of synaptic connections

Question 2

what makes a neutron look bumpy

Answer 2

synapses often occur on “spines”, tiny extensions on the dendrites –Spines make the neuron look bumpy

Question 3

are the spines permanent

Answer 3

These spines and synapses can come and go, appear and disappear, depending on their input (connections to other cells)
–if there’s a lot of input, they might increase in size or become stable (less likely to disappear) –if there’s only a little or no input, they might shrink or disappear

Question 4

does learning impact the number of stable spines

Answer 4

yes, it increases them

Question 5

where does Synaptic plasticity (spine stabilizing, etc) happen

Answer 5

anywhere

Question 6

what is stored in the hippocampus

Answer 6

Specifically, decades of research support the idea that episodic memories are formed and stored in the hippocampus

Question 7

what is Episodic memory

Answer 7

A memory of autobiographical events, things that happened to you Involves What, Where and When

Question 8

what is semantic memory

Answer 8

things you remember but didn’t experience, for example, if you remember that Eric Knudsen studied owls with goggles on or Diego Velazquez painted “las meninas” in 1656, that is semantic memory

Question 9

Why do we think episodic memory is in the hippocampus

Answer 9

Accidental experiments (patient HM)
Size of hippocampus
Lesions (removal) of the hippocampus
Monitor activity during learning
and memory

Question 10

who is patient HM

Answer 10

Henry Gustav Molaison or HM
Suffered severe epilepsy which was localized to his medial temporal lobe, where the hippocampus is
William Beecher Scoville, a Harvard neurosurgeon removed HM’s hippocampal region (and some neighboring structures).
This surgery cured HM of his epilepsy

but

He lost his memory of personal events that happened in the few years just prior to the surgery AND
He was subsequently unable to form new episodic memories
Thus, he was left mostly with long-term semantic knowledge of events prior to 1953
So that tells us something about the role of the hippocampus in episodic memory, but clearly there’s more that we need to know

Question 11

what is the theory about the correlation between the hippocampal size and episodic memory

Answer 11

studied in birds;
The idea is, animals that naturally perform tasks that rely heavily on the hippocampus ought to devote more of their brain to the hippocampus
–Either through use or evolution, the hippocampus should be larger in animals that use it a lot than in animals that don’t use it as much

Question 12

what is spatial memory

Answer 12

We call this use of geographic location and spatial cues SPATIAL MEMORY

Question 13

what bird has a quit large hippocampus compared to other births

Answer 13

the humming bird

Question 14

The function of the hippocampus has been studied a lot in food-caching in birds, how is this done

Answer 14

these are birds that collect food and hide it in order to eat it later
–kind of like squirrels
The parids collect small seeds or insects and hide them in the bark of trees in tiny holes that they make with their beaks
The corvids collect larger seeds, nuts and insects and hide them in holes in the ground that they dig with their beaks
This “caching ” or hiding of food potentially requires a map of the environment as well as memory of the locations where the food is cached

Question 15

what is the correlation that has been found between birds and the hippocampus size

Answer 15

birds that store food have a larger hippocampus than those that do not store food

Question 16

how do we know that the hippocampus size is experience dependent

Answer 16

Hippocampus size is also related to spatial ability in humans:
Work by Eleanor Maguire found that London taxi drivers have larger hippocampi than non-taxi drivers
And, the size of the hippocampus increases with time on the job –the more time they spend learning to navigate the city, the
larger their hippocampus is
So in this case, hippocampus size is experience dependent

Question 17

Some of the earliest demonstrations of the role of the hippocampus in spatial memory came from studies using what

Answer 17

the Morris water maze

Question 18

how was the the Morris water maze experiment conducted

Answer 18

With brief training (or after showing them the position of the platform)
–Rats can use local or room cues to navigate from any spot over to the platform –However, after training, rats with hippocampal lesions still take a long route to find the platform
In addition, Morris also removed the platform then tested to see how often rats would cross the pool and where they seemed to look
Control rats spent most of their time where the platform used to be
Lesioned rats did not
Instead, the lesioned rats searched all four quadrants for similar amounts of time
In fact, they made as many crosses of the quadrant boundaries as intact rats, they just visit all quadrants equally

Question 19

The hippocampus is larger in individuals or species that tend to do more what

Answer 19

“spatial” tasks

Question 20

Removing the hippocampus does what

Answer 20

impairs spatial learning and memory

Question 21

How do we look at activity

Answer 21

EEG, PET, fMRI and electrophysiology

Question 22

how is the PET scanner used for this

Answer 22

In 1998, Eleanor McGuire and colleagues had people go into a PET scanner and navigate around a virtual world
They found that hippocampal activity
How much it increased depended on whether they were good at navigating
people that were more accurate had more acidity than people that got lost
This result was pretty exciting, but it still leaves the question of how the hippocampus works? What exactly are those cells doing? How is a map of the world encoded in your hippocampus?

This is where we need higher resolution

Question 23

what are Place cells

Answer 23

They discovered that certain cells are active at certain spots in the space (red dots
And other cells are active at other spots

Question 24

how do place cells respond/activate

Answer 24

It turns out that, as a group, place cells respond to an entire environment, with each cell responding to just a tiny part

Question 25

what provides the start of a code for spatial memory

Answer 25

pattern of activity provides the start of a code for spatial memory

Question 26

what animals have this code for spatial memory

Answer 26

rats and bats

Question 27

what do place cells prove

Answer 27

Our goal here isn’t to solve the code
Rather, we want to
–verify that the hippocampus is indeed one place that stores episodic memory
–get a very basic idea of how we know that memory is there and how that memory is encoded
So what we’ve covered on place cells will suffice

Question 28

Place cells are for what

Answer 28

are part of the code for navigating and remembering the environment
What makes you remember something

Question 29

what is conditioning

Answer 29

to associate a place and an event, then test to see if they if they remember the association
We mentioned at the beginning that it can be difficult to ask animals about their “autobiographical” memories
We can do this through a behavioral training method called CONDITIONING

Question 30

Activity of cells in the hippocampus provide us with what

Answer 30

very detailed information on the role of the hippocampus in navigation
–there is clearly a very complex code that helps you to remember and navigate around a familiar place

Question 31

how do we study “what” and “where”

Answer 31

using conditioning

Question 32

how does conditioning work

Answer 32

In general conditioning works like this: Seeing food makes a dog salivate
But, hearing a bell (neutral stimulus, NS) does nothing
During conditioning, the dog learns the pairing of the bell and food (the bell predicts that food is coming)
After conditioning, just hearing the bell will make the dog salivate
But you can “condition” other things, like a place and event instead of a sound and food

Question 33

what is the experiment with a mouse and conditioning

Answer 33

Put a mouse in a blue room, it will wander around and explore
While it’s in the blue room, let’s say you give a mild foot-shock, then return it to its home cage
.
.
. foot-shock (even if you don’t give one) .
.
Later on, when you put the mouse back into the blue room
It will behave as though it expects there to be a
That is, it will act scared
What do mice do when they’re scared? They freeze i.e. they stand very very still

This means mice can quickly learn to associate
.
a place (blue room)
with an experience (foot shock)
.
and demonstrate that they remember the experience (freezing) to the place (“where” = blue room)
Conditioning
. (“what”= foot shock) by displaying a conditioned response
.
This is known as Fear Conditioning

Question 34

what can the hippocampus learn with regards to conditioning

Answer 34

The hippocampus can learn these sorts of associations

like conditioning and fear conditioning

Question 35

in general, can you have animals generate a memory

Answer 35

You can also have animals generate a memory by giving them particular experiences, then look at their behavior or gene expression

Question 36

how do we test “when”

Answer 36

In order to test whether birds have episodic-like memory, Nicki Clayton did several experiments with Western Scrub Jays
Scrub jays are a species of corvid that also includes
–ravens, crows, jays, jackdaws, nutcrackers

Question 37

what are corvids

Answer 37

The corvids collect larger seeds, nuts and insects and hide them in holes in the ground that they dig with their beaks

Question 38

how was the experiment conducted to connect Episodic memory: spatial memory and time

Answer 38

look back at lecture to explain experiment (lecture 18 November 23, 2017

Question 39

what was the conclusion of the Episodic memory: spatial memory and time experiment

Answer 39

to avoid the decayed worms, birds need to remember WHAT they cached WHERE and WHEN

This means that scrub jays could remember:
“What” was cached “where” (locations of worms vs. nuts)
i.e. spatial memory
AND
“When” those items were cached (and therefore whether they would still be edible)
This has the hallmarks of episodic memory