Okay. So now that we’re
talking about memory,
let’s talk about what’s actually happening
at the synaptic level in your brain.
So what I’m referring to is, in our
brain we have synaptic connections
between neurons or cells and they
happen everywhere in your brain.
But we’re going to focus on the
ones that are specific to memory.
Now, there’s a process
called “neural plasticity”.
And that refers to the malleability
of the brains pathways and synapses.
So, what does that
mean in English?
That means that pathways
are not static and that
the communication between neurons
is actually a dynamic process
and it can actually
change over time.
And it can change in relation
to activation or stimulation.
So, the connection or
synapses in the brain
are constantly being
modulated over time.
And that’s what you want.
You don’t want it so that all
the connections are static
and are set for life and
you aren’t able to adopt.
You want the exact opposite.
You want to be able to
adapt to new situations.
You want to be able to require and
change based on, say, new memories.
Now, how does memories applied
to synaptic connections?
Well, the working model is that
when a new memory is formed,
neurons will increase.
And so, it kind of makes sense.
If you are trying to remember something
or if you’re trying to repeat a word
or if there’s a certain
concept that you’re repeating
over and over and over and you
want to acquire to memory,
you’re going to want your neurons in
your brain to encode that information.
So one way they can do that
is to increase communication
between themselves through
this synaptic connection.
Now, when a brain injury
occurs, neurons will
reorganize in attempt to
compensate and adjust.
Again, we’re back to that
phenomena of us trying to
understand the brain through
injury or insult, right?
So, what we’re saying here is, say,
you have a stroke or a trauma,
you know, a gunshot wound
to the head or you’re
Phineas Gage and a tamping
iron has gone through.
The neurons that were damaged were connected
and were communicating something.
It could have been a memory.
It could have been a task.
And so, thanks to
neurons can reorganize, readjust and
try and pick up some the slack.
So, we also have the formation
of new neurons in the brain
and this is called
And it’s not everywhere.
We know for a fact in areas like the
spinal cord and other parts of the
central and peripheral nervous
system, you don’t get regeneration.
But the brain was fortunate enough
to actually have neurogenesis.
So, specifically in the areas like
the hippocampus and cerebellum.
This has been illustrated.
So, getting, applying this information
that we just figured out here,
we’re going to talk about how this
applies to memory and learning.
And I’ve already alluded to when you’re
trying to kind of code a memory,
you want these two
neurons to communicate.
So there’s a saying that we say, “What
fires together, wires together.”
So the more that neurons fire together
at the same time or communicate,
the tighter the connection.
So there’s no actual physical connection
but we use that analogy of wires.
So, as they fire together,
they form associations.
So, same thing with the network
that we were talking about,
about the nodes and the network,
that network of meanings
or memories or content,
the more that these nodes
the tighter the associations and more
meaningful and deeper the connections.
So, it’s not a coincidence that this
network idea and the idea that,
you know, the synaptic network is really a
network of neurons are so similar because
they’re essentially were trying
to illustrate the same thing.
And so, having a model that reflects
actual, physical organization makes sense.
So, the associations or
neural nets or patterns
of activation may represent
formation of memory.
So again, it’s not that neuron
A is talking to neuron B
and that equals the memory
associated with your address.
That’s not what
we’re saying here.
We’re saying that there’s actually
the formation of a network
or a neural net which is very
similar analogist to the
network that we were talking
about prior to the nodes.
And so, when you’re
trying to form a memory,
you might be actually
activating a neural net.
And so, you can exactly pinpoint a specific
memory because it’s a diffused network.
And this is actually a good
thing because it allows
for it to be dissipated and kind
of contain in various spots of
the brain as opposed to just being
targeted in one exact spot.
So, neurological evidence for the network
model of memory in retrieval context and cue
is proving this looking at
things like neuroimaging,
and you look at how you activate
and what affect that has.
So, frequency of activation
in neural nets and emotional
input can determine the
strength of associations.
The more you fire a neural net,
the more that it validates itself
and the stronger the association.
You can even layer in
things like emotional input
and that can even impact the
strength of the associations.
So, we’re going to take a look
at some actual sections here.
So, the images that you are seeing here
are one on the left, one of the right.
One being a section of a stimulated
brain and one of an unstimulated brain.
So what do you notice?
So, the one on the left
is highly innervated.
It’s a got a lot of networks,
a lot of branching
and we see a lot of
those little processes.
That is a really diverse,
well-connected neural net or network.
As opposed to the one on the
right, we see there’s --
the connections are
That’s not a very strong network
or it’s a developing network,
and it hasn’t been
stimulated much, right?
So you can see, the more you stimulate, the
more you learn, the more you interact,
the more memories are going to
get encoded, the more connected
and the greater degree
of inner connectivity
of those neurons or that
network, that neural net.
Now, we’re going to get into a
process of something called “LTP”,
which stands for
and this occurs after brief
periods of stimulation,
you see an increase in the synaptic
strength between those two neurons.
So, this is kind of near and dear
to my heart because I have done
quite a bit of research at the
bench with this model of LTP
and have actually done it
where you initiate LTP.
A lot of times in research, it’s done in
areas that are associated with memory.
So, in the research that I’ve
done and research that most do,
it’s in the area of
And the idea is we want
to create a model of
what we believe memory
formation might look like.
And we then try and validate this with
what we’re seeing in the actual brain.
So the idea is this.
If I hear your name
for the first time,
so you tell me your name and
you’re like, your name is Rita.
Hi Rita, nice to meet you!
Now, I need to
encode that memory.
So how am I doing that?
Well, it’s going to the steps of
we’ve already discussed before.
So it’s going to go in.
It’s going to go
through the buffer.
It’s going to go in to short-term
memory, and eventually, it’s going to
get to long-term memory at which
point we’ve encoded into our brain.
how are the neurons going
to actually do this?
Well, when they
hear the name Rita,
it will activate a group of neurons
which have formed a neural net.
And that neural net
will start to fire.
And this rapid stimulation
of that network is encoding.
It’s the actual encoding
process of the name Rita.
So, think of it of being shocked for a
brief, brief period and that represents us,
literally type, if you want to use an
analogy of us typing in to our brain Rita,
and that is the neurons firing.
that happens once and it increases
the connection between your neurons.
So, once that happens,
we have a more robust
to a given stimulus.
So the next time I hear the term
Rita or I’m asked and prompted,
“What’s her name,” or
“Do you know her name?”
Those neurons will fire
and fire more robustly
because they have a
pretty good connection.
That is due to the brief
period of stimulation
of when we’re actually
encoding the name Rita.
So, once LTP has occurred, the subsequence
threshold for firing is lower,
therefore it’s easier to fire.
Again, the more you repeat something,
the easier it is to remember.
And the more often you
the easier it is to keep
it in long-term memory.
So LTP is a process or a
model that we can say to
explain how we are increasing the
synaptic strength between two neurons
or within a neural net and
response to us encoding a memory.
So LTP is loosely thought to be a
model to explain memory consolidation.
And it also can create
new synaptic connections
and increase dendritic
branching at synapses.
So that previous diagram that
it show with all the branching,
that increase branching can
be when areas are stimulated,
i.e. learning new memories, i.e.
consolidating memories to the process
of long-term potentiation, LTP.
So, let’s look at this
in terms of a diagram.
And as you can see here,
we’re going to go
through a couple of steps
of what it looks like.
So the first diagram is showing a
presynaptic neuron, a postsynaptic neuron.
We have the synaptic cleft.
And we have vesicles
filled with transmitter.
So we’re just kind of reviewing a
little bit of the biology that
you’ve probably studied to death, but we’re
just going to go pretty quickly here.
So the presynaptic neuron is going to
get a signal coming down the axon.
So it’s action potential.
It’s going to trigger release of
a transmitter across the cleft
and it’s going to interact with
the postsynaptic receptor.
So you can see the little dots
and the cleft are representing
the transmitter binding to
the postsynaptic receptor.
Now, if you look at the
next figure to the right,
we’re going to see all
of these interacting
and you’re seeing the
propagation of the response.
in periods of LTP or rapid stimulation,
this is going to get strengthened.
And you can see in the third box we have
quite a bit of transmitter being released
and that is us strengthening
Okay. Now, in the final response,
you can see that we have
stimulation coming and you have --
it’s much easier to get a release of
transmitter because we’ve initiated LTP,
and therefore, not a lot
of stimulation is required
to initiate a fairly
So that is over viewing
the process of LTP.