Transcript Consciousness & Causality

Sleep
Dr Magda Osman
Room 2.25
Office hours Mondays & Tuesday
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

Sleep is an actively regulated function – not passive
or

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.

Ultradian rhythms (repeat within 24hr cycles)


REM/NREM cycles
(Jouvet, Michel, & Courjon, 1959)

They called it paradoxical sleep because it was so close to
wakefulness
Circadian Rhythms (CRs)

Adaptation - Humans have adapted to the environment.

Circadian rhythms, circa (“about”) and dies (“day”).

They are internal cycles, built into the central nervous system.
Circadian activities include sleeping and waking

A circadian rhythm is a 24 hour cycle in the physiological
processes of many organisms including plants, animals, fungi and
even bacteria (cyanobacteria).

Though CRs are endogenously (internally regulated), they can be
modulated by external cues such as sunlight and temperature.
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. 24.5 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
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
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 all work?
How does it all 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
Alpha waves 8-13Hz
Theta waves 4-7Hz
Delta waves 0.5-4Hz
<20 μV
20-100 μV
20μV
20-200μV
Brain Waves in sleep

Waking


Stage 1



Delta waves
Stage 4 (SLOW WAVE SLEEP)


Sleep spindles
– brief periods of high amplitude, high frequency
Stage 3


Mostly theta waves
Stage 2


Low amplitude, high frequency
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


Non-REM sleep only


Lower reptiles
Minor REM phases


Amphibians, fish
Cameleons, crocodiles, birds (when fledglings)
REM and Non-REM

All placental mammals
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 enhances 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).

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)
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 reorganizing memories gained during the day,

- if the latter then this suggests that implicit learning and problem
solving is being carried out while we sleep.
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.
Decision Making and Sleep deprivation

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
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.
2.
Extending nightly shift work from 8-12 hours - unclear
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.
Similar findings were reported in shift workers at a nuclear power plant and miners
(Ferguson, Paech, Dorrian, Roach & Jay, 2011; Smith, Todderdell & Folkard, 1995).
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.
Why?


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 sleep studies

Despite the apparent benefits of sleep on both procedural and
declarative memory, learning, and problem solving

Rickard, Cai, Rieth, Jones, & Ard (2008) show that many
demonstrations of offline learning are an artifact of two
factors:
1.
2.
the type of averaging methods used in the data to reveal sleep
effects
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
Methodological issues with shift pattern studies I

1. before-after designs


with performance on cognitive tests 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,
the shift combinations, speed of rotation and direction
of rotation (night to day, day to night), all of which
have been shown to influence experiences of fatigue,
mood, and work performance (Driscoll et al, 2007).
Methodological issues with shift pattern studies II

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.
E.g. fire fighters have physically demanding tasks where as air
traffic controllers are fairly sedentary in their jobs, but both need to
be alert and vigilant.
4. Cross comparison – details of physical activity


Many studies don’t control for physical activity in the profession.
E.g. Lambourne & Tomporowski (2010) show that running leads to
more impaired performance than cycling, and in general there is an
inverted U-curve between amount of exercise and cognitive
efficiency. Low to moderate aerobic exercise facilitates performance
whereas moderate to high aerobic exercise decreases performance.
What can we conclude?

Sleep does impact on psychological an physiological
behaviors



Sustained disrupted sleep does tend to impair attention, leads to weight gain,
depression, diabetes
The link between sleep and additional cognitive processing is still
controversial, there is no clear evidence that sleep does in fact lead to off –
line learning, the benefits of sleep are simply sustaining cognitive function,
rather than facilitating offline processing.
Why is it the case that only mammals tend to show REM
and NonREM based sleeping patterns - Is this a reflection
of intelligence and consciousness?
Is there is good evidence for
learning while sleeping?