Sleep Dr Magda Osman Room 2.25 Office hours Mondays

Do you think it is possible to learn new things while sleeping? A. Yes B. No C. Unsure

Learning outcomes  1. Have a basic understanding of the different biological processes associated with sleep  2. Understand the different methodological techniques used to examine the phenomena offline learning/problem solving/decision-making (e.g. learning while sleeping)  3. Understand the term consolidation

Do we need to sleep to function? What research tells us about the need for sleep  Biological Rhythms  Many parts of the brain remain active during sleep  Sleep and dreams serve biological and cognitive functions: 1. Sleep is an actively regulated function – not passive or 2. Sleep is the reorganization of neural activity rather than the cessation of it

Biological Rhythms  Circadian rhythms (24 hr cycle) Sleep/wakefulness cycles Entrainments – physiological Behaviours adjusted to the environment- This means you can train a person to behave Outside of the normal 24hr cycle.

Biology behind CRS  CRS is linked to differences Patterns of brain activity Hormone production, Cell regeneration  Hormone production Many hormones are secreted at different rates at different times of the day and night.  E.g., cortisol (steriod hormone) produced by the adrenal cortex. Serum cortisol concentrations rapidly increase in the early morning hours, gradually decrease during the day.  It is used for increasing blood sugar levels and changing metabolic rates

Why do we have CRs ?  If you put a person in a room without any access to daylight, clocks or any other indicators of the passage of time, Would still approximate a period of activity and rest that corresponds to a CR clock i.e hrs? Yes (Kleitman, 1939)  Kleitman was the first to demonstrate this by examining the endogenous behaviors of peoples sleep and wake patterns while living in a cave  Circadian rhythms are important in determining the sleeping and feeding patterns of all animals, including human beings

Control of CRs  Sleep/Wake cycles is controlled by the suprachiasmatic nucleus (SCN)  It is the master control center located in the hypothalamus, and is responsible for acting as your body’s internal pacemaker (i.e. key regulator).

suprachiasmatic nucleus (SCN)

How does the SCN work?  As the sunlight decreases at the close of the day, the visual system sends signals to the SCN.  Next, the SCN sends signals to the pineal gland to increase the produce of the hormone melatonin. This hormone increase helps reduced activity and makes you feel increasingly sleepy.  The SCN isn’t only dependent on signals from the retina to regulate wake/sleep patterns - neurotransmitter GABA excite the dorsal but inhibit the ventral section of the SCN

Cycles of Sleep stages (REM/NREM)

Description of Brain waves  Brain waves have two parameters: Frequency – the number of waves per second measured in Hertz (Hz) Amplitude – the height of the waves, measure in EEG recordings as microvolts (μV)  Types of Brain Waves Beta waves 14-30Hz <20 μV Alpha waves 8-13Hz μV Theta waves 4-7Hz 20μV Delta waves 0.5-4Hz μV

Brain Waves in sleep  Waking Low amplitude, high frequency  Stage 1 Mostly theta waves  Stage 2 Sleep spindles – brief periods of high amplitude, high frequency  Stage 3 Delta waves  Stage 4 (SLOW WAVE SLEEP) Mostly delta waves  REM Exactly like stage 1, but with REM

What happens during REM?  Decreased threshold of awareness of external events  Autonomic arousal (heart rate, digestion, salivation etc…)  Vestibular activation (spatial orientation, sense of balance, movement)  Genital arousal The functions of these states of arousal are still not clear

Speculation NREM & REM behavioral associates Hobson (2005) Nature, Vol 437

Evolution of sleep  Rest but no sleep Amphibians, fish  Non-REM sleep only Lower reptiles  Minor REM phases Cameleons, crocodiles, birds (when fledglings)  REM and Non-REM All placental mammals

Do you think that the presence of REM sleep in species indicate higher intelligence? A. Yes B. No C. Unsure

Psychological Factors associated with sleep 1. Facilitation through sleep 2. Impairment through deprivation

Facilitation/impairment of cognitive processes through sleep  Processes thought to occur during sleep Learning Problem Solving  Processes thought to be impaired by sleep disruption Attention & Memory Decision Making

Learning while sleeping I  Offline learning: Can sleep enhance learning so that we perform better than if we were awake the whole time? Yes, demonstrated in motor learning, memory recall, perceptual-motor tasks  Demonstrated using Associative learning tasks, after sleep learning shows offline consolidation of knowledge acquired during training – i.e. a reorganization of representations (Walker & Stickgold, 2004; Schonauer, Gratsch & Gais, 2015).  Why? Consolidation benefits. That is overnight there is neural reorganization of memory which resulting in more efficient storage of information, affording improved next-day recall (Gais, Molle, Helms, & Born, 2002).

Learning while sleeping II Sleep before learning also appears to be critical for brain functioning, which in turns mental functioning Memory? Specifically, one night of sleep deprivation markedly impairs hippocampal function – a brain region associated with memory  imposing a deficit in the ability to commit new experiences to memory. Learning? The effects of sleep on learning suggest that there are unconscious processes that are operating which still remain active during sleep (Walker & Stickgold, 2006) and can even be used to unlearn social prejudices (Hu et al, 2015).

Problem solving and sleep I  Wagner, Gais, Haider, Verleger, & Born, (2004)  Task

Problem solving and sleep II Wagner, Gais, Haider, Verleger, & Born, (2004)  There is an advantage of sleep, it helps mental restructuring This leads to speed of discovering the rule to the problem solving task.  Sleep reconsolidation is either reprocessing (rehearsing) memories made during the day, or re- organizing memories gained during the day, - if the latter then this suggests that implicit learning and problem solving is being carried out while we sleep.

How convinced are you that the Wagner et al (2004) study shows evidence of offline problem solving? A. Really convinced B. Reasonably convinced C. Not sure D. Unconvinced

Decision Making and Sleep deprivation  Dickinson & Drummond (2008) Two bingo cages are each filled with six colored balls: Cage A (4 green 2 red) Cage B (3 green, 3 red) Six draws (with replacement) To select a cage a die was rolled  1-2 meant Cage A, 3-6 Cage B  People didn’t see the die roll or the balls being drawn from the cages  People had to guess which cage the ball was likely to be drawn from, just from the odds.

 There is evidence to suggest that some types of decision making behavior (Bayesian updating) are resilient to sleep deprivation (at least 22 hrs sleep deprived) (Dickinson & Drummond, 2008).  There were no differences in performance accuracy  There were differences in decision strategy – if sleep deprived, people paid less attention to new information when forming their estimates of likelihood of cage draw Decision Making and Sleep deprivation

Learning & Performance – shift patterns I  Many people work different day/night work patterns such as shift intervals (rotas) during nights (e.g., 6hrs, 8hrs, 12hrs)  Applied research has examined the effects of different shift patterns (policemen, nurses, firemen) on: physical measures (heart rate, blood pressure, actigraph – measuring motor movements), neurobiological (EEG- measuring electrical brain activity) Cognitive measures of behaviour (Visual search task, Choice response task, Motor pursuit task, Recall-Memory tests, Psychomotor Vigilance device – measuring sustained arousal and attention).

Learning & Performance – shift patterns II  Can we connect sleep disruption to performance in occupations involving shift work? For instance, are there differences to physical states, alertness, stress, mood and impaired cognitive functioning (e.g., memory recall, decision making, perceptual-motor processing?  Not clear that there are differences – though controversial Studies of shift workers in the Medical, Naval, Aerospace, Industrial and Military domain show mixed findings 1. Extending nightly shift work from 8-12 hours - unclear 2. Reducing it from 12-8 hours, or alternating between day and night shifts (Driscoll et al, 2007; Smith, Folkland, Tucker & Macdonald, 1998) - unclear

Learning & Performance – shift patterns III  Rouch, Wild, Ansiau and Marquie’s (2005) study of 3000 workers, Long term shift worker showed decrements in memory (free recall, recognition), attention (Digit span tests) and forced choice reaction time tasks.  But, Washburn’s (1992) study on nurses and Peacock, Glube, Miller, & Clune’s (1989) study on police officers Both claims that while fatigue increased at the end of night shift, performance and alertness increased. How is that possible? Motivation and free time or periods of inactivity before the end of the shift may account for these findings. For instance, approaching the end of a shift may lead to compensatory strategies which generate a boast in performance which reduce the detrimental effects of fatigue (Muecke, 2005).

Methodological issues with offline learning studies 1. Problematic averaging methods used in the data to reveal sleep effects 2. Biased by time-of-day testing  which can often artificially enhance the benefits of sleep as a result of the gradual build up of amassed fatigue effects through repeated or concentrated training periods in day testing not preceded by sleep Rickard, Cai, Rieth, Jones, & Ard (2008) show that these two factors undermine the reliability of demonstrations of offline learning/problem solving/decision-making

Methodological issues with shift pattern studies  1. Before-after designs performance on cognitive tests are used as dependent measures - often fail to use the same cohort of participants before the change in shift to those taking part after a shift.  2. Shift length many studies don’t control for the length of the shift, and time at which shifts start (Driscoll et al, 2007).  3. Cross comparisons – details of task Many studies fail to detail the actual requirements of the professionals during shift work which is important for cross comparisons. i.e. physical (firefighting) v.s sedentary jobs (traffic control)

What can we conclude? There are limits to what we can conclude: 1. It isn’t clear yet that offline learning really takes places 2. It isn’t clear yet that there is a re-organization of representations during sleep (i.e. that we can learn new things, make new decisions, solve problems while we sleep) 3. What is clear is that we can adapt, and that shift work suggests that we can compensate cognitively to different sleep patterns

Which of the following statements are you more convinced by? A. Sleep stabilizes representations in memory acquired during wakefulness B. Sleep reorganizes representations acquired during wakefulness C. As yet, it isn’t clear what sleep does to representations

Is there is good evidence for learning while sleeping?