Sleep and Cognition Flashcards
Memory consolidation:
1- what did the German Psychologists Müller and Pilzecker 1900 propose?
2- what is needed to support new learning and create new memories?
3- support from studies on …….
1- German Psychologists Müller and Pilzecker 1900 proposed that a process known as consolidation takes place in order for memories to be maintained in our brains (fixed, become permanent)
2- A period of time is needed for the chemical and anatomical changes to take place in the brain to support new learning and create new memories
3- Support from studies on amnesia, with patients having problems with memory when the hippocampus and nearby areas are damaged (HM removed hemisphere- lost ability to remember long term info, couldn’t consolidate or store info)
sleep and plasticity:
1- what do the majority believe sleep contributes to
2- what have several studies found?
3- however what do some argue?
1- Although some disagree, the majority believe that sleep contributes to the plasticity of the brain
2- Supported by several studies, showing worse performance in learning after sleep deprivation
3- However, some argue that these deprivation-induced changes are not due to suppression of plasticity during sleep but due to activation of stress systems in the brain (Siegel, 2001)
Pavlides and Winson (1989)
Study and findings
- Recorded from ‘place cells’ (cell in the hippocampus which activate themselves or fire when an animal is in a particular location) in the CA1 area of the hippocampus, while rats were awake and exploring, drowsy and during sleep.
- Observed significant increases in firing rate during subsequent sleep but not waking
- there were significant increases in the firing rate during all sleep states following exposure
- Suggestive of LTP and information processing during sleep following learning
What have studies in drosophila suggest?
Paul Shaw’s group 2006 - Science
- Drosophila show increased number of synapses and enlargement of regions involved in information processing following exposure to enriched environments, including social environments
- Flies in a socially-enriched environment (30+ flies) display more sleep during the daytime (60min vs 15min bouts) compared to flies in impoverished social environment (individually housed)
- Manipulated space (bigger vs smaller vials), reproductive state, mixed vs single sex and overall activity using the infrared beam breaks - No differences were found
Drosophila in enriched vs impoverished environment
Animals in enriched environment slept more during th day than animals in the impoverished
Enriched Environments and Sensory Input in Drosophila:
1- what was manipulated/ looked at
2- result in blind flies
3- what is another factor which abolished the effect of enriched environments
4- what did not result in any changes in sleep
1- Selectively manipulated vision, olfaction and audition and looked at sleep after exposure to enriched social environments
2- Blind flies failed to show a change in sleep following exposure to enriched environment (norpA mutants) however restoring vision restored the effect. (Blindness due to rearing in darkness also resulted in lack of change in sleep)
3- A compromised sense of smell (retained visual acuity) also abolished the effect of enriched environments (smellblind mutants)
4- However, auditory cues did not result in any changes in sleep
Ganguly-Fitzgerald, Donlea and Shaw, 2006
Finding
No effect of space, reproductive state and activity
Daytime sleep in wild-type and NorpA mutants after exposure to increasingly larger groups - finding: increase in C-S
The information the flies were processing was visual info about other flies placed in the same tubes as them and this was causing increases in sleep during the day time. Increase info in visual system.
Initial findings Moving towards Systems consolidation
Wilson and McNaughton 1994
Study and findings
Performed simultaneous recordings from multiple hippocampal place cells in rats during a spatial task and in SWS preceding and following the task
Cells that fired together when the animal occupied a particular location showed an increased tendency to fire together during subsequent sleep compared to sleep episodes preceding the behavioral tasks
Cells that were inactive during behavior did not show this increase
Wilson and McNaughton 1994
First set of compelling evidence that experience-dependent replay takes place in the hippocampus during subsequent sleep
”During subsequent SWS, synaptic modification within the hippocampus itself is suppressed and the neuronal states encoded within the hippocampus are ‘played back’ as part of a consolidation process by which hippocampal information is gradually transferred to the neocortex”
- red lines- ones firing when animal is exploring the maze
- same cells that were active before are active again when the animals were sleeping
- animals were replaying info
- but gradually feeding info into cortex
Sharp-Wave Ripples (Buzsaki, 1992)
Describe the different waves
Theta waves in CA1 when animals are moving, exploring, rearing and sniffing
Sharp waves replace theta waves in CA1 when animals are immobile, drinking, eating and grooming – An alert but still animal
when animals are active/ exploring there is theta waves in their hippocampus but when they are stopping to sleep/ grooming there are sharp waves. These are accompanied by rapid firing called ripples.
Sharp Wave Ripples (Buzsaki 2015)
1- what do sharp waves show?
2- how are neurons organised
3- hypothesised to serve as?
1- Sharp waves show fast oscillatory pattern known as “ripples”
2- Neurons are sequentially organized although they fire quite fast
3- Hypothesized to serve as a mechanism to transfer information from the hippocampus to the neocortex for long-term storage – systems consolidation
systems consolidation definition
storing info for longer term in other areas of the brain
What is the “Two-Stage” memory consolidation model?
Neocortex (provides HIP with novel information during learning (theta waves) →← Hippocampus (transfers modified content back to the CX for storage (SPW-Rs)
What else is true?
- There is also evidence that synapses are downregulated during sleep, especially SWS
- Synaptic homeostasis hypothesis (Tononi & Cirelli 2014), where memory traces that are thought to be unnecessary are removed:
— synaptic pruning during sleep helps to reinstate the brain so that it can be able to function and learn again the next day
— this may be an important function of sleep (especially SWS)
T & C propose that when we are asleep besides the info being encoded and saved for later use there is also down regulation or removal of stuff we don’t need.
Synaptic Homeostasis Hypothesis of Sleep
(Tononi and Cirelli, 2020)
Argue for sleep dependent down-selection of neurons that fail to fire together during REM sleep
Evidence that SPW-Rs reduce recent memory- irrelevant neuronal activity
- when you go to sleep- brain will start to tease out info
- important info kept and stored for longer term use
- process that tales place during NREM sleep (sharp wave ripples important)
Synaptic Homeostasis Hypothesis of Sleep
(Tononi and Cirelli, 2020) MODEL
Most synapses weaken with sleep → ongoing learning, independent of specific tasks → most synapses strengthen with wake → sleep-dependent synaptic down-selection
Learning and memory in animals sum
Studies in animals find a strong association between learning during wakefulness and subsequent sleep, implicating both NREM and REM sleep
Two theoretical Perspectives on the role of Sleep in L&M
Dual process hypothesis: NREM and REM serve learning and memory but facilitate separate types of memories
(different types of sleep support different types of learning)
Sequential hypothesis: Both NREM and REM facilitate learning and memory in a complementary way, first NREM and then REM benefit learning in the order that they occur
Two theoretical Perspectives on the role of Sleep in L&M MODEL
LTM split into two bits of information: Explicit (conscious) and implicit (not conscious)
Explicit is then split into episodic (personal events) and semantic (facts, knowledge)
Implicit is split into priming, procedural memory and conditioning
(declarative (explicit)- info we receive when we’re consciously thinking about things
implicit- can becoming automatic)
Dual Process Hypothesis:
1- what does evidence support the role for?
2- what has REM sleep been more closely associated with?
3- what has NREM been associated with?
1- Evidence supports role for both REM sleep and SWS in learning and memory but for different types of material
2- REM sleep has been more closely associated with the enhancement of non-declarative (implicit) tasks (eg. dancing, learning how to drive)
3- NREM has been associated with the enhancement of declarative (explicit) memories
Slow-wave sleep and learning
Findings of wake vs nap in improvement
Participants learned a declarative learning task (list of paired words) and a nondeclarative learning task (mirror tracing). After a nap that included just slow-wave sleep, only participants who learned the declarative learning task showed improved performance, compared with participants who stayed awake.
declarative is benefiting from SWS but non declarative is not benefiting at all
Wordstem Priming Task and Spatial Rotation Task (Plihal and Born, 1999)
Study and background
- An implicit wordstem priming task:
- Given a list of 52 words to rate based on their melodious sound for 3 min. Then had a 5-min break and then were given word stems (beginning of word) (26 from previous list and 26 new ones) i.e. ’ho’ from ‘hotel’ and they had to complete with the first word that came to mind.
- Priming is implicit (non-declarative) and amnesiacs perform well in it
- Performance at the priming task is expected to be impaired by loss of REM sleep (later in the night)
(word task is implicit in this task but usually it is not)
Wordstem Priming Task and Spatial Rotation Task (Plihal and Born, 1999)
Study and background
Wordstem priming:
early: sleep group had an increased loss of priming compared to wake group
late: wake group had an increased loss of priming compared to sleep group
Mental spatial rotation:
early: sleep group did much better in recalling items compared to wake group
late: not much difference between sleep and wake
Their suggestion is that there is learning that benefits from particular type of sleep. In line with dual hypothesis
Motor skills
(Walker et al., 2002)
- Motor skills (tapping) such as those needed for musical instruments or sports such as gymnastics involve complex sequences of movements that show further improvement after the time of practice
- Musicians often are stuck on a part and after sleep can play it effortlessly
- Participants taught a number sequence 4—1—3—2—4 get ~60% faster after 5-6 min of practice but then reached a plateau
– After 12 hours the same participants were tested for just 1min.
– When training was in the morning and testing in the evening, performance was stable
– When training was in the evening and testing in the morning, after a night of sleep, they were 15-20% faster and they made fewer errors
Effects of sleep on Motor Skill Learning
(Walker et al 2002)
Results
All show that when retesting after sleep, there is a significant improvement in performance
practice with sleep → beneficial
Improvement was dependent on the amount of NREM2 sleep
Word Lists and Recall (Payne et al., 2009)
Study and findings
- Tested 20m or 12h later for recall or recognition
- All participants forgot 30-40% of the words on the list (compared to the 20m performance)
- Those that spent a day awake before testing “forgot’ 20%
- Those who got a night of sleep before doing the test in the morning “remembered” 5-10% more of non-presented words
- Sleep selectively stabilized and even enhanced the false memory of these words (title words) while forgetting the actual words on the lists
words on list included: nurse, sick, lawyer, medicine, health, hospital, dentist, physician, ill, patient, office, stethoscope
more than 50% of the participants reported seeing Doctor on the list
What is the point of these false memories?
1- what could be more beneficial to remember
2- what does our brain do?
3- know as what?
4- what didSara Mednick’s study (Cai, et al., 2009) show?
1- Perhaps beneficial to remember the gist rather than the exact information. Research on sleep and memory suggests that sleep goes beyond consolidation, and into memory evolution
2- Our brain does not merely store information but also transforms and restructures information so that insights, abstractions and inferences can be made
3- Known as an “aha” moment, a flash of insight in which the solution to a problem appears (either during dreaming or quiet wakefulness)
4- Sara Mednick’s study (Cai, et al., 2009) with the Remote Associates Task showed that a nap helped participants figure out the single word that linked three others together
info we connect with other info already existing within our brains. Problem solving/ creativity.
The Deese Roediger McDermott Effect
Word lists and check memory
Experimental design
Cai et al 2009
- Subjects were administered the creative problem-solving test in the morning and then a word analogy (eg. hard/ easy) priming task.
- After an intervening polysomnographically recorded sleep or quiet rest period, subjects were tested on the three prior exposure conditions: repeated exposure (white box), primed exposure (grey box), or no exposure (black box).
- Memory tests for the analogy solutions followed.
Priming Associative Networks
Remote associates task vs analogies
RAT:
COOKIES, SIXTEEN, HEART: ______
KEEL, SHOW, ROW: ______
Analogies:
CHIPS: SALTY; CANDY: S_________
FAST: SLOW; HARD: E_______
Priming Associative Networks
(Cai et al 2009)
Results
REM sleep facilitates the use of prior information for creative problem solving. Subjects who had REM sleep displayed a significant improvement above NREM and quiet rest groups (P= 0.047, 1-way ANOVA and post hoc analysis). Strikingly, although the quiet rest and NREM nap groups received the same priming, they displayed no improvement on the primed RAT items, whereas the REM group improved by almost 40% above the morning performance (Cai et al 2009)
“REM sleep and not incubation”
Impact of lack of sleep on vigilant attention
1- what is the best way to assess the impact of sleep loss?
2- what is vigilant attention also known as?
3- what do people frequently underestimate?
4- what are there individuals differences in?
- The best way to assess the impact of sleep loss is through tracking moment-to-moment changes in brain function (EEG and fMRI) and behavioral markers such as the psychomotor vigilance test (PVT)
- Sustained attention
- People frequently underestimate decrements in behavioral performance because of sleep loss
- There are individual differences in vulnerability to sleep loss and neurobehavioral consequences (some people may be more affected than others)
Impact of lack of sleep on vigilant attention
1- what lead to dose-dependent declines in vigilant attention, reaching levels comparable to?
2- what does this degradation in vigilant attention also involve
3- when are the greatest deficits found?
1- Chronic restriction of sleep resulted in dose-dependent declines in vigilant attention, reaching levels comparable to 2-3 nights without any sleep (Basner et al 2013; Belenky et al 2003)
2- This degradation in vigilant attention also involves deficits in selective attention, orienting to sensory events, and executive functions - very reliable consequences of sleep loss
3- The greatest deficits are found during the circadian night
Psychomotor Vigilance Test (PVT)
1- what is the test?
2- what does the standard test measure?
3- Sleep Deprivation induces reliable changes in PVT performance as seen in _______
1- Gold standard of behavioural alertness – computerised reaction time task (press a key as fast as you can when you see a stimulus, measuring accuracy and latency)
2- The standard 10min PVT measures sustained or vigilant attention by recording response times (RT) to visual or auditory stimuli that occur at random inter-stimulus intervals (ISI, 2-10s) including a 1s feedback period during which the RT to the last stimulus is displayed
3- Sleep Deprivation induces reliable changes in PVT performance as seen in:
– Overall slowing of RTs
– Steady increase in the number of errors of omission
– Modest increase in errors of commission (responses without a stimulus)
– Decrements in performance get worse as task duration increases (time-on-task)
– Sensitive to homeostatic and circadian influences
PVT performance in sleep deprived and non-sleep deprived controls
(Basner and Dinges, 2011)
Both started off well but as time progresses they all have this upward trend but the people who are well slept kept their mistakes low compared to sleep deprived
getting worse the longer you stay awake
Psychomotor Vigilance Test:
1- in a typical study, what happens to PVT reaction times and what time does this happen?
2- what time of night does impairment become most prominent?
3- fastest and slowest 10% implications?
4- what also has negative effects on performance?
1- In a typical study, PVT RTs begin to slow around 16h of wakefulness and degrade further across the night
2- Impairment becomes most prominent during the early morning hours
3- The fastest and the slowest 10% are significantly slower, with the slowest 10% disproportionately affected compared to the fastest. Thus, not only the average or typical responses are affected but also those that are the “worst” or “best” performers
4- Sleep restriction of only a few hours also has negative effects on performance
Cajochen, et al (1999)
A: Time courses of core body temperature, endogenous plasma melatonin, mean eye blink rate per 30-s epoch during Karolinska drowsiness test (KDT), incidence of slow eye movements (SEMs, percentage of 30-s epochs containing at least 1 SEM/5-min interval), and incidence of stage 1 sleep (percentage of 30-s epochs containing at least 15 s of stage 1 sleep per 5-min interval) are shown, averaged across 10 subjects ± SE.
B: Time course of subjective sleepiness as assessed on Karolinska sleepiness scale (KSS; highest possible score = 9, lowest possible score = 1), psychomotor vigilance performance [mean, median, 10% slowest and fastest reaction times in ms (logarithmic scale)], cognitive performance (numbers of attempts in 4-min 2-digit addition task), and memory performance (number of correct word pairs in probed recall memory task) are shown averaged across 10 subjects ± SE.
What were found for each of these conditions?
All data were binned in 2-h intervals and expressed with respect to elapsed time since scheduled waketime. Vertical reference line indicates transition of subjects’ habitual wake- and bedtime.
A:
- Core body temp: circadian rhythm (temp increased in day, decreased in evening)
- Plasma melatonin: opposite to core body temp (don’t have melatonin in day but goes up in evening)
- Eye blink rise: increase in blinking during the day
- Slow eye movements: sharp rise at night time
- Stage 1 Sleep: more likely to occur later in the day
B:
- Karolinska Sleepiness Scale: more sleepy during the night
- Psychomotor Vigilance Performance: 10% fastest were not as affected by circadian change (had fastest ms), median reaction time was the next quickest, mean reaction time was the second slowest, 10% slowest reaction time was the slowest (had the highest ms)
- Cognitive throughput: smaller number of attempts at night time
- Probed recall memory test: % of correct pairs decreased at night- peaked during the day
Hudson, Van Dongen and Honn, 2020
Study and findings
Twenty-six participants assigned in SD or control group
The mean number of lapses or errors (not responding in time) in those with regular sleep (in blue) and those sleep-deprived (in red), with a night of recovery sleep showing a decent recovery in performance. When having a recovery- they bounced back.
The long grey bars indicate night-time sleep whereas the short grey bars indicate night-time without sleep for those in the sleep-deprived group
Reported not sleepy!
Hudson, Van Dongen and Honn, 2020
Performance across 8 days
N= 90
Errors in the PVT as a function of time in bed (TIB) after 8 consecutive days of tracking performance, with those who spent less TIB performing worse than those with more TIB
restricted of sleep = more mistakes
only having 4.2 hours / day compared to 8.2 hours / day was significantly worse
Effects of sustained sleep restriction and prior wake extension on vigilant attention
There seems to be an accumulative affect- however much you slept before will have an impact on later
this effect was seen in both prior habitual sleep and prior sleep extension
What is another effect of sleep deprivation on vigilance
Performance instability (unpredictability of when people are performing okay)
This performance variation is not gradual or linear or predictable, it occurs randomly as the time-on-task increases
This unpredictable nature makes fatigue very dangerous, especially in safety-critical operations
PVT Responses from a Single Subject
(Satterfield BC and Van Dongen HPA 2013 from Grandner 2019)
Raw PVT RTs from a single subject collected over the course of a 62h SD period.
PVT performance is shown at 5h wake and then after 24h each time.
RTs become longer and more variable as a function of both time-on-task and time awake
False starts (black diamonds) also increase
Gray Diamonds = mean RT+SD
big lapses when they are not paying attention can happen at any point. Random moments where they can be zoning out.
Individual differences
1- what varies across individuals?
2- perhaps it is possible to identify ____
3- use of ____
4- what was sleep loss found to be associated with?
1- Cognitive impairment during sleep loss varies across individuals
2- Perhaps it is possible to identify those resilient and those vulnerable
3- Use of biomarkers such as genetic polymorphisms i.e. subjects homozygous of a DAT1 10 repeat variant were more resilient to time-on-task effects compared to the 9-repeat variant (Satterfieldet al, 2017)
4- Sleep loss was found to be associated with lower fronto-parietal activation
Time-on-task performance for the DAT genotype groups across 38h of total SD
(Satterfield et al, 2017)
9R are more susceptible than others
10/10 are fairly consistent
9R show an increase in RT between 03:00 to 18:00
Executive functions: Harrison, Horne and Rothwell (2020)
study and findings
- Normal aging affects the pre-frontal cortex which displays the greatest cortical volume reductions with age
- Compared young adults SD for 36h with non-SD groups (young, middle-aged and old) on neuropsychological tests oriented on the PFC
- All tests showed decline with age
- 36hrs of SD in young adults (19-27y) produced an outcome similar to that of old participants (66-85y) in the Hayling task (response inhibition eg. stroop task)
Executive functions
1- list some higher cognitive functions
2- functions that rely heavily on the ____
1- Several higher cognitive functions; ability to sustain attention while suppressing distractors, inhibit inappropriate actions, switch tasks, shift mental sets, cognitive flexibility, planning, decision-making, etc
2- Functions that rely heavily on the PFC which is sensitive to sleep loss - metabolic activity within the vmPFC is significantly reduced even after a single night of sleep loss (Thomas et al., 2000)
Cognitive Control
1- what is it?
2- what does it allow?
3- what did Haavisto et al 2010 find?
- The ability to regulate and coordinate thoughts and actions in-line with behavioral goals or changes in situational demands
- Allows balance between cognitive stability (actively focus and maintain focus on a task) and cognitive flexibility (update information when new information becomes available and suppress irrelevant information) i.e. avoid hitting a deer/fox while driving
- Haavisto et al 2010 – multi-tasking performance after sleep restriction over 5 nights, 4hrs vs 8hrs of sleep
– Found that sleep restriction impaired the ability to multi-task as a function of the number of days of sleep restriction, with performance degrading further as time-on-task increases
– It took 2 nights of recovery sleep for their performance to recover
– Implications for safety-critical operations require switching between tasks i.e. airline pilots, truck drivers, medical personnel, military personnel etc
Multitasking Task (Haavisto et al 2010)
on total sleep time:
many tasks eg. verbal/ maths. SR group started off the same but then their performance started to drop the more that they were restricted. When they had the opportunity to sleep more their performance bounced back.
on number of lapses:
control had a consistent number of about 1 lapse whereas SR had increased number of lapses reaching its peak at SR3 with 4 lapses then it declined again, reaching back to control at R2.
total multitask score:
control consistently had had score, SR scores decreased at SR2- SR5
Killgore et al 2012- what is the task they examined?
- Iowa Gambling Task (computerised) studies demonstrated that lack of sleep is associated with a pattern of performance similar to those with lesions in the vmPFC (eg. they might go for quick rewards instead of wait for benefits in LT)
- Sleep deprivation is associated with a change in decision-making strategy that favours short-term over long-term gains.
Killgore et al 2012
study and findings
- 54 healthy volunteers (18 to 36 y) took part
- Randomly assigned to one of four double-blind drug conditions:
– caffeine 600 mg (n = 12),
– dextroamphetamine 20 mg (D-AMPH, n = 16),
– modafinil 400 mg (n = 12),
– placebo (n = 12)
Findings:
- Sleep deprivation was associated with a significant decline in decision-making performance on the IGT at the circadian nadir relative to rested baseline.
- sleep-deprived individuals became progressively more shortsighted in their decision-making approach in the early morning hours, tending to prefer risky short-term gains at the expense of incurring long-term losses, an effect that was most evident during the latter half of the task
- Administration of caffeine, D-AMPH, or modafinil 90 min prior to the IGT on the second night of sleep deprivation had essentially no effect on decision-making performance, despite an improvement in psychomotor vigilance speed and reduced subjective sleepiness ratings following administration.
- IGT performance was restored to a normal rested pattern of advantageous decision-making following one night of recovery sleep (i.e., 12 h time in bed).
– ability to make decisions were comprised and they made more risky decisions
– caffeine- cured sleepiness, decision making capability did not improve at all.
