history and background sleep states and...
TRANSCRIPT
1
Sleep States and Memory
Dr. Carlyle Smith
Dept. of Psychology
Trent University
Peterborough, Ontario
History and Background
• Two experimental designs have been usedextensively to study the relationship ofsleep to memory processes.
• 1) Learn Task - Observe Sleep - Retest• 2) Learn Task - Deprive Sleep - Retest
Animal Studies
• Training was done with rats in a 2-wayshuttle shock avoidance task.
• Animals were given 50 trials/day for twoconsecutive days.
• Sleep recording took place both beforeand for many days after the end oftraining
50 TRIALS PER DAY FOR 2 DAYS
MINUTES OF REM SLEEP RELATIVE TO BASELINE FOR LEARNING AND NON-LEARNING ANIMALS
Days
TD1 TD2 PTD1 PTD2 PTD3 PTD4 PTD5 PTD6 PTD7
REM
in Minutes from
Baseline
-10
0
10
20
30
Learning AnimalsNon-learning ControlsBaseline
Early Human Work
• In a study done in a practical setting, weexamined the changes in sleeparchitecture that might occur aftersubstantial learning in a real lifesituation.
• We examined the sleep of students beforeand after exams without typifyingmemory systems
REM Sleep Changes After Exams
• We sleep recorded 4th year HonoursPsychology students in the summer, whenthey were not taking classes of any kind.
• We recorded these same subjects 3-5days after their last Christmas exam inDec.
• We then recorded them again the nextsummer, when they again were nottaking courses of any kind.
2
Exam Study Con’t ….• Control subjects were same age
individuals that had been in Honours,and were now in tech or teachingassistant positions.
• Their intent was eventually to go on tograd school, but they were consolidatingdebts, waiting for a partner to finish, etc.
• They were sleep recorded in Summer 1,at Christmas and during Summer 2 aswell.
MEAN TOTAL NUMBER OF REMS FOR LEARNINGSTUDENTS AND FOR NON-LEARNING CONTROLS
Summer 1 Xmas Summer 2
Me
an
To
tal N
um
be
r of R
EM
s
200
400
600
800
1000Learning Controls
*** *
DISTRIBUTION OF REMS IN EACH REM PERIOD FOR LEARNING AND CONTROL SUBJECTS AFTER CHRISTMAS EXAMS
REM Period
1 2 3 4 5
Num
ber of RE
Ms (from
Baseline)
-100
-50
0
50
100
150
200
250
300
LearningControls
*
REMS DENSITIES FOR LEARNING AND NON-LEARNING CONTROL GROUPS FOLLOWING CHRISTMAS EXAMS FOR THE LEARNING GROUP
REM Period
1 2 3 4 5
Mean
RE
M D
ensities (fro
m b
aseline)
-2
0
2
4
6
8LearningControls *
Appetitive Bar Press Task
• We examined (Smith&Wong, 1991)changes in sleep after extended training inSkinner box with increasing levels ofdifficulty
• 1 Magazine (M), 3 Simple Bar press (A),FR -10 sched (2 days) and then 3 days witha difficult sequential operant (SO).
Con’t...
• There were two bars to press.
• During the Sequential Operant, reward wasonly given when rats could “move” the lighton a 3 x 3 matrix from upper left to lowerright - after which they got a pellet
• This required alternate bar presses or 2 leftbar, 2 right bar.
• Deviations reset the program.
3
Con’t...
• Only some rats learned the task. We calledthem Fast Learning
• Some rats could not learn and extinguished.Called Slow Learners
• Non-learning rats were not trained.
• FRC controls pressed at the FR-10 levelinstead of changing to SO task
Minutes of REM Sleep For Each of the Groupsfrom Pre - Training Mean Baseline REM
BAR PRESS CONDITION
M A1 A2 A3 FR1 FR2 SO1 SO2 SO3
RE
M S
leep in minutes
-10
0
10
20
30
FL - fast learningFRC - FR ControlSL - Slow learningNL - Did not learnMean Baseline REM
Human Studies
• The progress in using human subjectshas paralleled the progress in theunderstanding of memory itself.
• Different kinds of memory are nowbelieved to exist.
• The two main types of memory are -– 1) declarative - often explicit
– 2) procedural - often implicit
Declarative Memory and Sleep
• Declarative learning does not seem to berelated to any stage of sleep.
• Sleep deprivation following acquisition ofa paired associates task did not impairmemory for this task 1 week later
• Sleep deprivation did not impair recallfor of a set of memorizedneuroanatomical structures.
0102030405060708090
RE
MD
Stag
e 2
Aw
Con
trol
s(L
)
Con
trol
s(H
)
TrainingRe-Test
Effect of Sleep Deprivation on Memoryfor Neuroanatomical Structures
No differences% Correct
Cognitive Procedural Learning
• Cognitive procedural learning is one typeof procedural learning.
• This type of learning requires the learnerto develop a new cognitive strategy inorder to solve the problem (e.g. Tower ofHanoi).
4
Cognitive Procedural Memoryand Sleep
• Cognitive procedural tasks appear torequire REM sleep for most efficientlearning
• Sleep following acquisition of the Towerof Hanoi and Mirror Trace tasks shows amarked increase in number of REMs andREM density.
• There is no change in the amount ofREM sleep (minutes) or any other stage.
0
200
400
600
800
1000
1200
1400
1600
1800
PRE POST
TESTCONTROL
Total Number of REMs
REMs
*p < .0001
Night 2 Night 3
0
2
4
6
8
10
12
14
16
18
PRE POST
TestControl
*
Night 2 Night 3
REM DENSITIES
p < .0002
5
0102030405060708090
100110120
PRE POST
TESTCONTROL
Total REM Sleep
Minutes
Night 2 Night 3
No Differences
0
5
10
15
20
25
PRE POST
TESTCONTROL
% REM Sleep
%
Night 2 Night 3
No Differences
IQ Groups
• The test groups were separated in termsof High (HiQ; X=125.8), Medium (MedQ;X=114.7) and Low IQ (LoQ = 102.5).
• Controls were a mix of all levels @ X=108.3 (n=6/group, N=24)
• The higher the IQ score, the better werethe learning scores for the tasks.
IQ Con’t...
• The higher the IQ score, the greater wasthe number of post training REMs andthe larger was the REM Density measure.(HiQ>MedQ>LoQ).
• The intensity of REM sleep was alsocorrelated with success in taskacquisition and re-test.
TOTAL NUMBER OF REMS BEFORE AND AFTER TRAINING ON THE TOWER OF HANOI AND MIRROR TRACE TASKS
Nights
Baseline Post-training
Mean
Nu
mb
er of R
EM
s
0
500
1000
1500
2000
2500
LoQMedQHiQControls
***
**
IQ Con’t...• There was no correlation between
“native” REM intensity and IQ or taskscores.
• The largest REM intensity responseswere exhibited by Ss with the highest IQand the highest acquisition and re-testscores.
• Post-training REM intensity may be abiological marker for learning potential
6
NUMBER OF RAPID EYE MOVEMENTS FOR COMBINED TRAINED AND NON-TRAINED CONTROLS AT EACH REM PERIOD
REM PERIOD
1 2 3 4
Num
ber of Rapid Eye M
ovements
100
200
300
400
500
600
700
800
Combined TrainedNon -Trained Controls
PERCENTAGE REM FOR TEST AND CONTROLSAS A FUNCTION OF NIGHT
NIGHT 1 AND NIGHT 2
PE
RC
EN
TA
GE
RE
M
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30 TESTCONTROLS
Selective REM Deprivaiton
• Selective REM sleep deprivationfollowing acquisition of the Tower ofHanoi or a complex Logic Task results inmarked memory loss on re-test one weeklater.
• NREM awakened controls were notimpaired on these tasks.
Tower of Hanoi TaskImprovement after sleep deprivation
Groups
Controls (HC)
TSD REMD Controls (R)
NREM Awakening
Savings S
coresP
re - Post (# of M
oves to Solution)
-10
-5
0
5
10
15
20
25
**
*
Alcohol Ingestion
• One common type of behaviour oncampus is to work hard during the day,drink hard in the evening and then fallinto bed.
• Alcohol is know to induce a reduction innumber and density of REMs wheningested in moderate amounts (as few as3 drinks) just prior to bedtime.
Alcohol Con’t...
• After an acclimatization night in the sleeplab., we trained students in both adeclarative (Paired Associates) and acognitive procedural (Logic) task(Alcohol Night 1) .
• They then drank 3-5 drinks of vodka(1 1/4 oz/drink) and orange juice andthen went to bed (0.7g/Kg.).
7
Alcohol con’t...• Another group drank orange juice alone
after learning (OJ Night 1)
• A third Control group drank nothing (CNight 1).
• All groups slept a second night with nodrinking.
• On Night 3, the OJ group of Night 1drank alcohol, while the alcohol group ofNight 1 drank OJ.
% CORRECT PAIRED ASSOCIATE RESPONSES BEFORE AND AFTER ALCOHOL CONSUMPTION
Before and After Alcohol Consumption
PRE POST
% C
orrect Paired Associates
10
20
30
40
50
60
70
80
90
100
ALN1ALN3Controls
% CORRECT WFFs BEFORE AND AFTER ALCOHOL CONSUMPTION
PRE POST
% C
orre
ct W
ffs C
on
stru
cte
d
20
40
60
80
100
ALN1ALN3Controls
**
Experiment 2
• Was this an alcohol or a sleep effect?
• Trained subjects on Tower of Hanoi andPursuit Rotor at 4 PM in the afternoon.
• One group (Aft - Alcohol) then drankimmediately (0.9g/Kg) after learning andwent to bed 5 hours later.
• One group drank just before bed (Eve -Alcohol).
NUMBER OF MOVES TO SOLUTION ON THE TOWER OF HANOI TASK
PRE POST
Num
ber of Moves to S
olution
0
20
40
60
80
100Evening - AlcoholAfternoon - Alcohol
*
Pursuit Rotor Target Times for AFT- EtOH and EVE- EtOH Groups Before and After Alcohol Ingestion
Alcohol Condition
PRE POST
Mean N
umber of S
econds on Target
60
80
100
120
140
160
EVE-EtOHAFT- EtOH
*
8
Sleep Effects
• REM sleep was similarly modified inboth experiments.
• Both number of minutes of REM sleepand number of REMs were reduced inthe first half of the night in study 1.
• The density of REMs was reduced in thefirst half of the night in study 2.
Conclusions
• Even moderate alcohol ingestion prior tobedtime can modify sleep architecture,particularly REM sleep in the first half ofthe night.
• Moderate alcohol ingestion at bedtimecan induce memory loss the night oflearning AND/OR 2 nights after theoriginal learning has taken place.
Conclusions con’t...
• Interference with normal REM sleepeither the same night, or two nights afteracquisition of procedural material canresult in memory deficits of 20-40%.
• Alcohol at bedtime can impair memoryfor both cognitive procedural and motorskills tasks.
Conclusions Con’t ...• The REMs results implicate the PGO
system of the pons in efficient memoryconsolidation
• Animal studies (Datta et. al., 2000)support this theoretical position, sincethey have observed increases in P wave(PGO) activity in the rat followingsuccessful acquisition of the 2-way shuttleavoidance task