2. What we will cover
• Review anatomy of structures involved in memory
• Explain how Short- term memory works
• Understand the concepts of consolidation and long-
term potentiation
• Understand how amnesia emerges and list its causes
3. From our previews lecture on the
Limbic system:
• We examined HM’s case and realised that the
Limbic system is necessary for the transfer of
experience into long- term memory and for its
easy recall (even though it is not where
memories are stored)
• Try talking yourself through the Papez circuit
on the next slide:
4. Work out the sequence in which
different structures are involved in
Papez’s Circuit
7. Introductory concepts
• Imagine you receive a hard blow on your head
enough to render you unconscious:
• You will lose memory about what happened a
few minutes before the insult and will (of
course!!!) not make any new memories while
you are unconscious
• However, you will not have lost either your
ability to recall past memories or make new
ones!
8. So, what’s your point?
My point is twofold:
a) You require CONSCIOUSNESS to make new
memories
b) Short term memory can be disrupted by
insults that affect the ongoing electrical
activity in your brain.
If you disrupt that = no transfer to Long- term
memory.
9. So, what’s the point of all that???
• Short- term memory (STM) is a product of on-
going electrical activity in your brain
• Long- term memory (LTM) requires
consciousness to be created from STM and is
stored in a more reliable form=
modification of synapses.
10. Quiz
What is the name of the process where
information stored in STM is transferred to LTM?
See next slide
12. Key facts about consolidation
• Needs consciousness
• Arousal is important (likely in the form of
Noradrenaline; the reason why you may remember
every detail of an exciting encounter but none about this
lecture!)
• Make sure you are confident at defining
consolidation before moving on!
13. Mechanisms that optimize
consolidation- Part 1: the phonological
loop
Language is very important:
We engage in an internal monologue when
presented with new information that can be
articulated, ie instructions (go buy bread, milk and cheese,
remember number 123124523, the bones of the hand are the
scaphoid, lunate…)
Constantly repeating these instructions in our
head extends our STM and allows effective
consolidation
14. An experiment (of sorts): Read the number in the first box,
and follow the instructions, then go to the next slide and see if
you can remember the number given!
Input: Remember
this number
47863159144
Phonological store:
Now you are
encoding these
numbers as
electrical activity,
relating to how they
sound ‘four,
seven…’
Articulatory
process:
Now you are
actually ‘saying’
them, either out
loud or in ‘your
brain’, repeat it
for at least 30
seconds
15. Now look again at this number(a
different one)
79018523364
Close your eyes IMMEDIATELY and keep them
closed for 30 seconds, DO NOT practice the
number, you only have ONE go at remembering it.
And go to the next slide (hopefully you’ve read this
before indefinitely closing your eyes).
16. How well did you do?
• Yeap I know, you did much better when you
had the chance to rehearse the information
• This ability, conferred by the phonological
loop allows you to consolidate better as well
as enhance your STM!
17. Part 2: The visuospatial sketchpad
This encodes all the information that cannot be coded verbally
It is not as good as the phonological loop, as the lack of the
ability to articulate or verbally code these information, means
that we cannot rehearse it!
Less rehearsal, makes for an embarrassing performance!
No experiment for this one I’m afraid, look at Dr Millar’s lecture on the
slide with the pig drawing and you will see what I mean.
18. Therefore
STM can either be rehearsed in the phonological
loop or roughly mapped out in the visuospatial
sketchpad, before being either discarded or
consolidated as LTM
19. The anatomical location of the
phonological loop
• It requires the
a) Dorsolateral frontal lobes- they provide the
attention required to perform the rehearsal
b) Wernicke’s area to store the ‘sound’ of what
you want to remember
c) Broca’s area to perform the articulatory process
(think about saying it or actually saying it)
d) The arcuate fasciculus to connect Wernicke’s
and Broca’s
20. Try and label the structures mentioned
in the previous slide
22. • The phonological loop is more prominent on
the LEFT frontal lobe
• The visuospatial checkpad is more on the
RIGHT frontal lobe
23. What happens if you lose the
phonological loop?
• Damage to the left dorsolateral frontal lobe,
leaves you with decreased digit span
memory, so the lack of the ability to rehearse
a long number, makes you worse at recalling
it!
• Also deficits in attention (and exhibition of
perseverance)
24. Ok got it!
• So we have STM that is formed by loops of
electrical activity mostly in the frontal lobes,
mediated either by the phonological loop (for
stuff we can verbalise) and the visuospatial
sketchpad (for stuff we cannot).
• Then if it is to be put into LTM, consolidation
happens.
• So, how does consolidation happen???
25. As we said before:
• Consolidation= Synaptic modification,
permanent.
• One of the main mechanisms of consolidation
is Long- Term Potentiation
27. Fire and Wire- LTP
• That’s the main concept: Synapses that fire
together, wire together
• If a neuron receives high frequency stimulation
delivered at the same time by several axons, then
its response to future stimulation by those axons
is enhanced!
• In other words, they fired together so now they
are wired together!
28. How does the ‘wiring’ take place in
LTP?- draw a diagram while reading
this outline
1) Glutamate released from pre-synaptic neuron
2) Glutamate binds to AMPA receptors in post-
synaptic neuron that ‘opens up’ to let Na+ ions
in
3) If the release of glutamate is ‘strong’ enough the
NMDA receptor loses the Magnesium ion that
acts as a sort of ‘gate-keeper’
4) Glutamate binds to the NMDA receptor and
BOTH Na+ and Ca2+ enter the post synaptic
neuron
29. This is what your diagram should look
like, try talking it through and explain
to yourself or a colleague
30. Then?
• Then all the Calcium that comes in starts
doing fancy stuff so that in the future the
post- synaptic neuron can be activated more
easily, such as increasing how many glutamate
receptors it has on its surface and changing its
shape so that current flows more easily
through it
• Therefore these two neurons fired together
and now they are better wired together!!!
31. So where are memories kept stored
using this mechanism?
• One memory is stored in many different
locations in the association cortices, and it
becomes conscious when a pattern of
neuronal activity occurs, ie when all the ‘right’
neurons in different places fire up in a specific
order!
32. Thinking of an apple
• Eliciting your memory of an apple, possibly
parts of your visual association cortex lights up
to remind you of what it looks like, then
maybe the olfactory or gustatory areas to
remind you of what it smells and tastes like
etc
• All these combined together give you the
conscious experience of ‘remembering’ an
apple!
33. How do memories end up in the right
places in our brain? And how do we
retrieve them?
• The limbic system seems to be important in
directing in what association cortex each bit of
the memory should be stored
• The hippocampus and the amygdala as well
as the thalamic nuclei (rem the Papez circuit)
seem to be important in retrieving these
memories
34. Summary!- go back and answer these
questions
1) STM- what structures are involved? What is
the phonological loop and what is its
significance?
2) LTM- what structures are involved? What is
consolidation? What is LTP?
35. Amnesia: Types
PROFOUND MEMORY LOSS
1) Anterograde= new events not transferred in
LTM (case of HM)- (problem with consolidation)
2) Retrograde= inability to recall events that
happened before the onset of the amnesia, but
can form new memories
3) Dissociative= selective blocking out of traumatic
memories
36. Amnesia: Aetiology
Anything that disrupts consciousness or the
integrity of the structures of the areas involved
in memory:
1) Trauma
2) Infection- meningitis, encephalitis
3) Electrolyte imbalance
4) Degeneration- eg due to alcohol
5) Psychogenic etc etc etc
