L6 Sleep and Memory Consolidation

Question 1

When is it important to sleep?

Answer 1

Important to sleep before learning as will improve concentration and learning abilities
Also important to sleep after learning to consolidate the learning

Question 2

Why is the relationship between sleep and memory complex?

Answer 2

Because there are several different memory stages (encoding, consolidation, association, recall, reconsolidation, erasure) and different sleep stages
As well as memory types

Question 3

What is the dual process model?

Answer 3

States that specific sleep stages are associated with a specific type of memory
PPs tested using the night half paradigm - tested after different stages of sleep
- 1st group went to sleep and were woken up after they’d had more SWS and then tested
- 2nd group had to stay up and go to sleep later so they had more REM sleep and then were tested
SWS associated with declarative memory
REM associated with non-declarative memory

Question 4

How has research added to the dual process model?

Answer 4

States that stage 2 is important for motor tasks

Question 5

What are the problems with the dual process model?

Answer 5

It seems too simplistic
Doesn’t consider influence of other stages of sleep
What about memories which have a declarative and non-declarative component?

More research was done which lead to the Two Step Model

Question 6

What is the Two Step Model?

Answer 6

Looked at sleep stages collectively and focused on the cycling from N-REM to REM
Step 1: Non-adaptive memories are weakened during SWS
Step 2: Adaptive memories are integrated in REM sleep

SWS filters out all the nonsense, important stuff integrated with existing memories in REM sleep
It is important to filter out unimportant memories that don’t serve any function

Question 7

What are the strengths of the Two Step Model?

Answer 7

It is supported by animal AND human evidence
Sleep stages are not viewed in isolation
Cyclic structure of sleep is important

Question 8

What are the limitations of the Two Step Model?

Answer 8

Difficult to test directly

What are the exact functions of each sleep stage?

Question 9

What is the Active System Consolidation Model?

Answer 9

Born et al., 2006
Integrates aspects of the DPM and TSM, it is interested in individual stages and also the cycling
Lots of supportive evidence
Is the key model for memory consolidation

Question 10

How do we learn memories according to the ASCM?

Answer 10

Initial learning phase, encode representations in the brain from information
With a latter retrieval stage where memories are reactivated and brought into consciousness
Have to go through period of consolidation, will undergo some whilst awake but majority takes place during sleep

Question 11

What happens at the level of the brain when encoding memories according to the ASCM?

Answer 11

When first encoded they are represented in both the hippocampus and the neocortex. When a memory has undergone very little consolidation it is thought that the hippocampus via hippocampal-neocortical connections binds together with the neocortex to bring memory to consciousness
Need these connections to bring memory back

Question 12

What role does sleep play in this consolidation of memories in the brain according to the ASCM?

Answer 12

During SWS there are slow oscillations which are thought to drive reactivations and help with reorganisation
SWS helps to replay these newly learned memories
Results in hippocampal-neocortical connections weakening and cross-cortical connections strengthening
Recalling memories at a later stage no longer depends on the hippocampus and can go directly to neocortex
SWS is the driver for transfer to the LTM
REM important for integrating memories with existing memories and strengthening synaptic connections

Question 13

What is targeted memory reactivation (TMR)?

Answer 13

Can manipulate what you replay in your sleep
Can be triggered by specific sounds or smells
If sounds/smells present during learning phase are presented again in SWS - memories are reactivated more specifically and therefore more likely to retrieve at recall phase

Question 14

How did Rasch et al. (2007) study TMR?

Answer 14

PPs carried out a task involving learning card locations followed by a test phase
During training were exposed to a smell of a rose
They then went to sleep and during SWS they were exposed to smell of the rose again
2 groups: either exposed to smell of a rose or a bear (control)
When they were tested the rose group performed significantly better

Question 15

How do we know it was specifically the rose that caused this effect?

Answer 15

Additional controls used so findings are very reliable
Looked at only presenting smell during SWS and not learning - found no significant difference in performance between this and the control
Did the same with learning and REM sleep instead and again found no significant difference
This tells us its specific to learning & SWS
This looked at behavioural evidence

Question 16

What was the physiological evidence from Rasch et al.’s (2007) replication?

Answer 16

Used fMRI
When odour was presented, the hippocampus lit up
The hippocampus reactivates the memories associated with that specific smell

Question 17

What was seen when sound was used instead of smell?

Answer 17

Rudoy et al. (2009)
PPs shown objects each accompanied by a corresponding sound e.g. cat with a meow
Then took a nap, during SWS they were played half of the sounds
They then had a test phase, cued sounds showed less decline in memory (less error) and non-cued sounds showed a greater decline in memory

Question 18

What are some potential real world applications for Rasch et al.’s research?

Answer 18

Revision techniques
Memory problems e.g. Alzheimer’s
Older age (natural decline in memory)

Question 19

What happens to memory and sleep relationships in older age?

Answer 19

SWS starts to decline from the age of 30 onwards, which will affect memory consolidation
Electrical activity in the SWS is no longer synchronised - some kind of misalignment
The size of the slow waves are smaller
Get less sleep spindles in SWS - must be important for memory consolidation (Helfrich et al., 2018)

Question 20

What are some reasons for this poorer sleep in old age?

Answer 20

Degeneration of neurons - causing change in body’s internal clock
Degeneration of medial frontal cortex - important for generating SWS
Medication & comorbidities
Pain
Weaker bladder

Question 21

What is the relationship between sleep and false memories?

Answer 21

Research is relatively new here but SD increases the formation of false memories
Research is mixed as some have found that sleep itself can increase the formation of false memories so research is still on going
Has implications for EWT

Question 22

What did Jenkins and Dallenbach (1924) find?

Answer 22

That memory recall of nonsense syllables was better when the retention period was spent in sleep rather than wakefulness (this was independent of retention period duration)
Findings were consistently replicated by other authors with more solid methodological control procedures

Question 23

What did animal studies find about REM?

Answer 23

Was originally focused on REM sleep being involved with active consolidation
several animal studies using drugs or the swimming pool technique to selectively deprive animals of REM sleep showed consequential memory impairment
BUT the learning might deteriorate due to the intense stress provoked by the REM deprivation studies themselves

Question 24

What evidence has been found with the DPM?

Answer 24

A perceptual learning task (equivalent to procedural memory) was usually improved by sleep but isn’t following REM SD
But inconsistencies appeared such as there being a positive effect of REM sleep in declarative memory tasks
Contradicting evidence reflects the difficulty of attributing specific psychological properties to single sleep components