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Lecture 5

PSY270H5 Lecture Notes - Lecture 5: Synapse, Interference Theory, Memory Consolidation

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Christine Burton

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Long term memory – Lecture 5
Memory consolidation
Encode: placing info in the memory (refer to cognition)
Consolidation refer more to what is happening in the neuronal level.
o Putting info in the memory at the neuronal level
Three types of consolidation :
oSynaptic consolidation occurs at the neuronal level and is fast-acting
What happen btw neurons
oSystems consolidation involves multiple brain structures and can take decades
Consolidating memory across different brain areas
oReconsolidation occurs when a memory is reactivated but over a much shorter time
Already the person has consolidated the memory we retrieved the memory and
we have to reconsolidate the memory
Each time we retrieve the memory memory become susceptible to including
new information
Each time we retrieve can change the memory and may include the wrong
Synaptic Consolidation
Long-term potentiation(LTP) increases the sensitivity of post-synaptic neurons by causing
structural changes more receptors at the post synaptic cell
In LTP :
oLTP is a lasting structuring change btw the adjacent neuron
oPost synaptic cell develops more receptors
oPost synaptic cell become sensitive to input from pre-synaptic cell
oSo info coming from the pre-synaptic cell doesn’t have to
be strong
oSo even with low signal can cause the post synaptic cell
more active
oIn here LTO occurs only between two cells
Systems Consolidation
In here LTP can occur cross number of different brain areas
Hippocampus imp in consolidating memory
How does system consolidation work ?
oConsolidation require hippocampus
oHippocampus is not needed for the retrieval
oHippocampus is only needed for LTP and storage of memory
oHippocampus acts as a scaffold
oMemory is stored in the cortex Memory is consolidated in the cortex
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oAt synaptic level LTP can explain simple learning
oMore elaborated learning hippocampus is needed and LTP
oInformation is not stored in the hippocampus
Formation of long-lasting stable memories requires more than a local cellular response
Medial temporal lobe is particularly important for systems consolidation
Standard model of consolidation is hippocampal-dependent, but retrieval is hippocampal-
Systems Consolidation
Hippocampus binds information across different
cortical areas – over time, cortical connections are
Why do we forget?
Serial position curve Number of items recalled and the list position
Item that occurred in the beginning of the list primacy effect
oDuring primacy effect items are remembered well
Item that occurred in the end of the list recency effect
o Items the occurred in the end are remembered well
Remembering is bad when there are words in the middle of the list
Explanation :
oWe have separate memory system
Long term memory
Short term memory
oHow are we able to remember the items in the beginning ?
Due to STM and rehearsal
Items at the beginning have more rehearsal
Rehearsal lead to better long term memory and thus remembering the items in
the beginning
oLess opportunity to remember items in the middle
oRecency effect:
Items are still active in STM
So we are able to remember recent items better due to STM
oPrimary and recency effects can be dissociated we can remove one and not remove the
other they involve separate memory system
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Why do we forget?
Evidence that primacy and recency
effects involve separate memory
systems comes from observation that
we can eliminate one with the other
Poor memory for items in the middle can be explained by decay theory and interference
What would happen if after the presentation of the last item, you were instructed to count from
backwards ?
oRecency effect would be reduced
oBecause we are not rehearsing the recent item
oWe already rehearsed the 1st items by the time we get to the last item
oIncrease the delay and can not rehearse recency effect goes away
What happen when increase the number of words per min?
oLess rehearsal
oReduce the primacy effect
oRecency effect is not affected
There are other factors which affects the memory
Interference other information which affects the retrieval of the information
oInformation is in the memory but ind is unable to retrieve the information
oWe forget the middle items because there is retro and proactive interference
So more likely to forget
o1st item/early items no proactive info
oLast items no retroactive interference
Two types of interference :
oRetroactive interference (RI): inhibitory effects of new information on old information
New information get in the way of retrieving the old information
oProactive interference(PI): inhibitory effects of old information on new information
Old information get in the way of retrieving new information
Past memories inhibit an individual's full potential to retain new memories
Problem with the Proactive interference :
Old information get in the way of new information
Why do we have Proactive interference sometimes and sometimes we do not?
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