Sleep & Memory

Question 1

What is memory consolidation, and who defined it?

Answer 1

Memory consolidation is the process by which new memories are integrated unto longterm stores (Squire et al., 1984)

Question 2

What is the dual process hypothesis?

Answer 2

Slow wave sleep supports declarative memory consolidation and REM supports Procedural memory consolidation

Question 3

Who created the dual process hypothesis?

Answer 3

Borbely (1981)

Question 4

Who conducted the main partial sleep deprivation study, investigating the night-half paradigm?

Answer 4

Plihal and Born (1997)

Question 5

How did Plihal and Born (1997) investigate the role of SWS and REM in consolidation?

Answer 5

• Participants were split into 4 groups
• they either partook in a complex declarative learning task (like learning word pairs), or a simple procedural task (like mirror tracing)
• participants were then retested after a period of early sleep (SWS) or after late sleep (REM)

Question 6

What did Plihal and Born (1997) find?

Answer 6

• declarative memories were best consolidated after SWS
• procedural memories were best consolidated after REM

Question 7

What are the limitations of Plihal and Born’s (1997) sleep study?

Answer 7

• partial sleep deprivation may not fully isolate specific sleep stages
• re-awakenings may induce stress, effecting participants’ abilities to recall information
• ‘simple’ and ‘complex’ tasks may not be the best way to isolate declarative and procedural memory, making the results harder to interpret and compare
• early sleep deprivation studies used unrelated word pairs, while recent ones use related word pairs, highlighting that learning task characteristics may influence consolidation
• fails to investigate differences in consolidation between semantic and episodic declarative memory

Question 8

Who suggested that investigating consolidation of episodic and semantic declarative memories could allow for a deeper understanding of the role SWS and REM play in memory consolidation?

Answer 8

Walker and Stickgold (2004)

Question 9

Who created the active system consolidation theory?

Answer 9

Muller and Pilzecker, 1900

Question 10

What is the Active System consolidation theory?

Answer 10

During SWS, the hippocampus is reactivated and new declarative memories are redistributed to the neocortex via neuronal networks

Question 11

How are new declarative memories transferred from the hippocampus to the neocortex?

Answer 11

• Slow oscillations: low frequency, high amplitude waves
• Sleep Spindles: short bursts of high frequency waves
• Hippocampal sharp-wave ripples: fast waves associated with memory reactivation

Question 12

Who identified coordination between slow oscillations, spindles and ripples during SWS, representing the hippocampal reactivation and transference of memory?

Answer 12

Marelli et al., (2013)

Question 13

How have studies shown the correlation between slow oscillations associated with SWS and declarative memory consolidation?

Answer 13

studies have manipulated slow oscillations during NREM using transcranial electrical stimulation, with results showing improved declarative memory consolidation

Question 14

Who identified that age differences affect how well declarative memory is consolidated during SWS?

Answer 14

Rauchs et al., 2022

Question 15

What are the limitations of the active system consolidation theory?

Answer 15

• age affects consolidation
• when SWS is eliminated via deprivation, consolidation of declarative memory doesn’t stop, it just occurs less effectively suggesting that other mechanisms are at play

Question 16

What does historical research suggest about the role of REM in procedural memory consolidation?

Answer 16

• REM has been considered to be the most important sleep stage due to the increased brain activity
• studies such as Plihal and Born’s show procedural memories are best supported by REM

Question 17

Who suggested that impaired consolidation of procedural memories after REM could be due to stress from sleep deprivation?

Answer 17

Born and Gais (2000)

Question 18

Who investigated the effect of REM-suppressing drugs on procedural memory consolidation?

Answer 18

Walker and Stickgold (2004)

Question 19

What did Walker and Stickgold (2004) find in their meta-analysis of 19 studies investigating REM suppression and procedural memory consolidation?

Answer 19

• the reviewed studies showed REM suppression had no effect on procedural learning
• none investigated the degree of rem suppression
• none retested memory after the sleep period
• this implies that the studies provide no relevant information regarding Procedural memory consolidation

Question 20

Who found a significant correlation between REM duration and procedural memory recall?

Answer 20

Fischer et al. (2002)

Question 21

Despite the relationship between REM duration and procedural recall found by Fischer et al. (2002), what did later studies find?

Answer 21

Later studies using functional magnetic resonance imaging (fMRI) failed to replicate the results

Question 22

What sleep stages do recent research show as being most important for procedural memory recall?

Answer 22

• SWS
• non-REM (NREM), sleep stage 2 (N2)

Question 23

What are the limitations of REM sleep deprivation studies?

Answer 23

• results could be attributed to the proportion of N2 sleep experienced during the late night testing periods rather than REM
• while early studies highlight REMs significant role in procedural memory consolidation, recent research utilising brain imaging fails to support this notion