Declarative Memory Consolidation and Sleep

Kimberly FennCognitive PsychologyPsych 200January 13, 2011

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Longterm Memory

Declarative Memory

Memory for facts,information, and events

Procedural Memory

Memory for skills, habits,and conditioning

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Traditional Memory Models

Short TermStore

Long TermStore

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After initial acquisition, memory remains in aweak or malleable state, susceptible to loss due tointerference or decay

Current Memory Models

Long TermStore

ConsolidationShort Term

Store

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Consolidation: the process by which memories arestrengthened and stabilized, increasing resistanceto interference and decay

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Absence of Sleep

• Impaired working memory• Decreased arousal• Increased RT to stimuli• Real-world consequences▫ Car accidents

▫ Comair Flight 5191 crash▫ Exxon Valdez oil spill

Why Sleep?

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• Proposed mechanism of consolidation: Offlineprocessing▫ Your brain “works on” information without any effort by

you

• Sleep provides a physiological state during which offlineprocessing can occur

Why Sleep?

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Procedure: Paired Associates Task

• Participants studied 40 word pairs

• Cued Recall Test – 40 word pairs▫ Feedback given on every trial

Error Correct response

• Trained to criterion: 60% correct

• Delayed cued recall test – 12 hours aftertraining

CAMP - TRAILBOOK - STORYCAT - TAILGLACIER - SNOWTOAST - EGGTEAM - CREWGALE - WINDANIMAL - FOX

Consolidation of declarative memory duringsleep

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Design

Day 1 Day 2

9:00 21:00 9:00

WakeStudyTest I

Test II

SleepStudyTest I

Test II

Wa

kin

gIn

terv

al

Sle

ep

Inte

rva

l

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Recall PerformanceN

umbe

r of c

orre

ctly

reca

lled

wor

d pa

irs

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No Evidence of Circadian or Diurnal differences inperformance

Rec

all P

erfo

rman

ce T

est I

Run

s to

Crit

erio

n

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Declarative Memory and Sleep

• Recall of information is better after sleep than it wasprior to sleeping

• This effect is specific for an interval that includes sleep▫ No improvement is seen after waking

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A Memory Test….

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• Bed• Rest• Awake• Tired• Dream• Wake• Snooze• Blanket• Doze• Slumber• Snore• Nap• Peace• Yawn• Drowsy

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Declarative Memory and Sleep

• Sleep improves recall of paired associates

• This effect is specific for an interval that includes sleep▫ No improvement is seen after waking

• Does sleep simply strengthen a memory trace?

• Can sleep change the way that a memory is stored orthe ability to use a memory?

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Recall…

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Did you see the word snooze?

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Did you see the word dream?

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Did you see the word lamp?

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Did you see the word sleep?

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The List Bed Rest Awake Tired Dream Wake Snooze Blanket Doze Slumber Snore Nap Peace Yawn Drowsy

If you remembered seeing theword Sleep then youexperienced a false memory

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Does sleep affect the formation of false orillusory memory?

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• Sleep may promote associative generalization▫ Increased false memory

• Sleep may consolidate or strengthen truememory or prune false memory▫ Reduced false memory

False Memory and Sleep

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3 Studies with sleep manipulation

• DRM lists presented either Visually or Auditorally

• Visual recognition test▫ Studied items▫ Critical Lures▫ Unrelated Lures

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SLEEPBedRestAwakeTiredDreamWakeSnoozeBlanketDozeSlumberSnoreNapPeaceYawnDrowsy

Correct memory(Studied items)

Critical Lure

Day 1 Day 2

Condition 10:00 22:00 10:00

12 HourWake

Study Test

12 HourSleep

Study Test

Wa

kin

gIn

terv

al

Sle

ep

In

terv

al

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Results: Collapsed across experiments

**

*

* p< .05 compared to wake

** p < .01 compared to wakeFenn, et al., 2009

*

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• Sleep reduces false memory without correspondingreduction in correct memory

• Sleep may be enhancing memory for the source ofthe information

False Memory and Sleep in the DRM Paradigm

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Is sleep strengthens an original memory, can itincrease resistance to misleading information?

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ProcedureI. StudySs watch film of two-car accident.

II. MisinformationSs estimate speed of cars when the cars ...

a) “smashed into each other”or

b) “hit each other”

Misinformation Effect

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41 mph

34 mph

1 week later: “Did you see brokenglass?”

“smashed” Ss “hit” Ss

% yes (incorrect) 32% 14%

(Loftus & Palmer, 1974)

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Misinformation and Sleep

• Procedure1. Video of robbery2. Misleading information

Questions about film

3. Recognition test Appeared in the film

Appeared only in questions (suggested memory)

Unrelated lures

• Two factors▫ Retention interval▫ Timing of misinformation

“At the beginning of the scene, a young man dressed injeans, a t-shirt and gloves entered the house. Did heappear to be in a rush when he entered?"

"Let’s begin at the start of the scene again. At the beginningof the film clip, the young man who entered the house wasdressed in jeans, a t-shirt and gloves. What color were thegloves?"

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9:00 21:00 9:00

Movie

Wake

Sleep

MisinformationTest

Movie MisinformationTest

Condition I: “Test”Condition II: “Movie”

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Correct Recognition

Prop

ortio

n H

its

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False RecognitionPr

opor

tion

Fals

e R

ecog

nitio

n

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Misinformation and Sleep

• Sleep can have both positive and negative effects onmemory

• Sleep can protect memory from reconstruction▫ When misinformation occurs after sleep, participants are better able to

identify studied information and reject suggested information

• Sleep may increase false memory and increase memoryreconstruction▫ When misinformation occurs prior to sleep, false information may get

consolidated with veridical memory

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If sleep can increase resistance to misleading information,will sleep deprivation decrease resistance ?

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Sleep Deprivation

• Reduces working memory capacity

• Reduces frontal lobe function

• May reduce ability to acquire information

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Memory Susceptibility and Sleep Deprivation

• Procedure1. View pictures that depict a story2. Misleading information

• Read sentences that tell the same story, with false information

3. Multiple choice test4. Source test

• Independent Variable▫ Sleep vs. Sleep deprivation

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…She showed her friend the new South Park DVD.Her friend very much approved of her selection…

…She showed her friend the new South Park DVD.Her friend did not approve of her selection….

How does her friend react to her DVDselection?

a)He seems pleasedb)He seems displeasedc)He seems neutral

Source Test• I saw it in the pictures only• I saw it in the narrations only• I saw it in both and they were the same• I saw it in both and they conflicted with each other• I guessed

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22:00 00:00

Sleep

Lab ArrivalSet up for PSG

Lights Out

02:00 06:00 08:00 10:00

Lights On

Encoding PhaseMath Learning Task

MisinformationTest

48 hrs

10:00

Math TestFree Recall Test

Sleep Deprivation

MoodAssessments

Snack

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Correct memory for story elements

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False memory for suggested information

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“Robust” False MemorySource Test• I saw it in the pictures only• I saw it in the narrations only• I saw it in both and they were the same• I saw it in both and they conflicted with eachother• I guessed

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• Memory performance is worse after sleep deprivation

• Correct memory for studied information is lower thanafter a full night of sleep

• Sleep deprivation increases susceptibility to misleadinginformation

Memory Susceptibility and Sleep Deprivation

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Overall: Sleep and Memory

• Sleep can improve declarative memory for studied information

• In some cases, sleep may also decrease false memory or increaseresistance to misleading information

• Sleep deprivation decreases memory performance for studiedinformation

• Sleep deprivation increases susceptibility to misleading information

Sleep is important. Study early. DoNOT pull an all-nighter before anexam! You will perform worse.

45Thank you

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