sleep & memory

Question 1

what happens during sleep?

Answer 1

(1) memory is strengthened and consolidated, (2) assimilated/integrated into memory networks

Question 2

consolidation

Answer 2

process of concverting learning into a long-term memory
* fast process
* declarative and procedural memory

Question 3

stages of sleep

Answer 3

• sleep follows a 90 min cycles of alternating REM (dreams) and non-REM (4 stages)
• REM sleep:
  * dream stage
• NON-REM sleep:
  * divided into 4 stages
  * stages 3 and 4 comprise slow wave sleep (SWS)
  * new data indicates different parts of brain can be in different stages of sleep simultaneously
• the percentage of REM increases, and of SWS (slow wave sleep) (NREM stages 3-4) decreases, during the course of sleep

Question 3

what is SWS?

Answer 3

NREM stages 3 and 4
- if you put electrodes on the scalp, stages 3 and 4 have much slower waves

Question 4

why does sleep help facilitate memory?

Answer 4

memories are replayed during sleep

Question 5

REPLAY in sleep

Answer 5

memories are reactivated/re-engaged during sleep and strengthening it as a result

Question 6

memories are “replayed” during sleep
- place field and place cells

Answer 6

• studies of place field activity in hippocampal neurons

place field - area in which neurons fire

place cells - population of neurons that fire differentially to different locations in space
* fire in a relational manner (WRT to cues in environment)

Question 7

replay (Skaggs & McNaughton, 1996)
- rats in triangular track

Answer 7

rodents run in a triangular track with electrodes implanted in brain

FINDINGS:
- cell 1 responds to a specific location
- cell 2 fires before cell 1 while running in track

–> show that a temporal bias begins while on track

while rats go to sleep, cells continue to fire with a temporal bias

Question 8

replay definition

Answer 8

neural firing patterns that mirror neural firing patterns during a task –> replicated in next period of sleep replay is important for memory consolidation

Pleiffer & Foster (2013)
- rats learn spatial layout of environment
- learn where ‘home’ is after many trials
- neurons fire BEFORE rat moves

Question 9

transitive inference

Answer 9

learn series of pairs (A>B, B>C) and realize that a hierarchy exists (relational network: A>B>C)

• builds RELATIONAL NETWORK
• rats with no hippocampus did well with premise pairs but performed worse with transitive pairs

**HIPPOCAMPUS IS NECESSARY FOR TRANSITIVE INTERFERENCE (i.e. to form memory networks)

Question 10

transitive inference and sleep

Answer 10

• there was no evidence for the development of transitive inference after the short (20 minutes) delay; but strong transitive inference performance following time delays of either 12 to 24 hours
  *suggests that building relationship between pp takes time
• longer-range transitive inference (two degrees vs one degree of item separation) was seen only after sleep (12-hour sleep or 24-hour groups)
• sleep benefited the longer-range connections
  –> Better established hierarchy

Question 11

two stage model of sleep and consolidation

Answer 11

• After encoding of a declarative memory two things happen:
  –> Stage 1: consolidation of new declarative memories while keeping individual representations separate
  · Preferential to SWS (hippocampus)

–> Stage 2: consolidated memories are integrated into rich associative networks
· Preferential to REM sleep (cortex)

— hippocampus allows binding of arbitrary information quickly and independently from things already known

— cortex identifies overlapping information and updates semantic network

Question 12

motor skill learning

Answer 12

TASK:
- participants learn a sequence they have to type

RESULTS:
significant correlation between performance improvement and amount of time spend in NON-REM stage 2 in 4th quarter of night
- procedural memory benefits of stage 2 NON-REM sleep

Question 13

encouraging memory replay during sleep: odor experiment

Answer 13

smelling roses (during SWS) while sleeping helped cue replay when smelling roses during exam

–> context specificity can help enhance memory during sleep too

Question 14

specificity of sleep enhancing effects (Rudoy et al 2009)

can u cue specific memories during sleep & enhance those specific memories later on?

Answer 14

Learn location of items on the grid - each item was paired with a sound

THERE WAS A BENEFIT W SLEEP!

sound cues presented during sleep prompted preferential processing of corresponding object-location associations and improved memory

Question 15

specificity of sleep enhancing effects (Hu et al 2015)

Answer 15

1) used counter-bias training to reduce implicit social bias
2) reactivate that training (play sound from training) during sleep to enhance the effect

RESULT:
- bias reduced

Question 16

Patient FL

Answer 16

• has psychogenic anterograde annesia due to a car accident
• memory for each day disappears after a night of sleep

no structural brain damage (not of organic nature)

SCENE LEARNING (DECLARATIVE) TASK:
- exhibited evidence that memory is accumulating day-to-day, regardless of what she reports

MIROR TRACING (PROCEDURAL) TASK:
- did worse on 2nd day than on 1st which suggests she is not faking it

IS SHE FAKING IT?
- unusual functional amnesia who form is shaped by how she imagines memory to work