The relation of eye movements during sleep to dream activity: An objective method for the study of dreaming.

Dement & Kleitman (1957)

SLEEP It is an interesting topic and it has been

usually studied by medicine.

The better way to investigate this issue, is using electroencephalography (EEG) measuring brain activity during sleep.

This usually gives an idea of the “structure” of sleep during the night.

SLEEP1. NREM SLEEP (9-130 mins)

Each stage

STAGE 1: (hypnagogic stage)•Transition state between

being awake and sleeping. • Eyes move more slowly • Muscle activity and heart rate

slow down. • Light sleep where you can be

awakened easily• Relaxation stage drowsiness

STAGE 2:• Movement stops • Brain waves become slower

with an occasional burst of rapid brain waves.

•At this point, the body prepares to enter deep sleep.

SLEEPSTAGE 3- Extremely slow brain waves (delta waves)

-Combined with smaller, faster waves called theta waves.

STAGE 4- Deepest sleep. - No eye movement or muscle activity - Brain produces more delta waves than theta waves. - In Stage 4, some may experience sleepwalking or night terrors.

REM SLEEP (rapid eye movement)

STAGE 5- Breathing becomes more rapid- Eyes move rapidly - Muscles are temporarily paralysed. (to protect from acting out) Heartbeat may increase and muscles may experience occasional muscular twitches. - REM usually takes place 90 minutes after falling asleep.

Normal sleep cycle: Stages 1, 2, 3, 4, 3, 2, REM

BACKGROUND AND CONTEXT

Dreaming and sleep are closely related, but only recently it’s been studied scientifically.

It is a very interesting topic, and has caught the attention of many scientists.

Sleep deprivation one of the ways of studying sleep.

BACKGROUND AND CONTEXT

Scientific study of dreams physiological variables using a reliable scientific method to determine exactly when dreaming occurs.

Self report there is no other way of proving dreaming occured.

Self reports + physiological techniques to measure phenomena reliable and objective

BACKGROUND AND CONTEXT

Aserinsky + Kleitman first to study relationship between REM and sleep

They discovered that high dream recall in participants woken up during REM.

They confirmed the relationship between

REM + SLEEP + DREAMING

BACKGROUND AND CONTEXT

They also discovered that there was a cyclic process depth of sleep changed during the night

AIM AND NATURE This study shows the results of

a rigorous testing of the relationship between eye movement and dreaming.

Hypotheses:1. There is a significant

relationship between REM/NREM sleep and dreaming, such that (based on previous research).

REM sleep is associated with dreaming and NREM, isn’t.

AIM AND NATURE 2. There is a significant

positive correlation between the subjective estimate of the duration of dreams, and the length of eye movement period prior to awakening.

3. There is a significant association between the pattern of eye movement and the content of the dream. Eye movement reflects the visual experience of the dream.

METHOD / DESIGN 7 adult males / 2 adult females Studied under controlled lab

conditions 1 night in the sleep lab being woken

at various intervals

Physiological recordings were made of: Changes in corneoretinal potential

fields as the eyes moved Brainwaves (as a criterion of depth

of sleep)

METHOD / DESIGN Two or more electrodes

were attached near the eyes

Two or three attached to the scalp.

Participants were woken by the ringing a doorbell near the bed for them to wake up.

METHOD / DESIGN Participants had to speak

into a recording device near the bed and say: Whether or not they had

dreamt If they could, relate the

content of the dream

No communication between participants and the experimenter until it had been judged that the participant had been dreaming.

How did they know participants had really dreamt?

They had to give a coherent, fairly detailed description of dream content.

Only then the experimenter could enter the room and ask for details.

Participants didn’t know if they were woken from a REM or NREM sleep.

RESULTS/ FINDINGS REM sleep basically had low voltage relatively

fast EEG pattern.

RESULTS/ FINDINGS In between REM periods EEG indicated

deeper sleep They were either

High voltage Slow activity Or frequent

No REMs were observed during the initial moments of sleep

RESULTS/ FINDINGS REM uninterrupted periods lasted between 3-50

minutes (mean 20) They tended to increase the later in the night they

occurred

The eyes didn’t move with a constant pattern they occurred in bursts of 1, 2 to 100 movements

A single movement lasted 0.1-0.2 seconds and followed by a fixation pause of varying duration.

RESULTS/ FINDINGS The REM periods occurred quite frequently during the night

average every 92 minutes.

Awakenings during the night:

Despite the awakenings, sleep was similar to uninterrupted sleep.

HOURS %First 2 hours 21Second 2 hours

29

Third 2 hours 28Fourth 2 hours

22

RESULTS/ FINDINGSHYPOTHESIS 1 Participants uniformly showed a high incidence of dream recall

following REM awakenings, and a low incidence following NREM awakenings.

When REMs stopped, the incidence of dream recall dropped dramatically. Within 8 mins after REM ended in 17 awakenings 5

dreams were recalled Within more than 8 mins after NREM 132 awakenings 6

dreams were recalled.

RESULTS/ FINDINGS Participants were more confident

they hadn’t dreamed, after NREM

When aroused during deep sleep they were confused and they felt they must’ve been dreaming but they didn’t remember the dream.

When participants couldn’t recall a dream following REM sleep, this was usually in the first two hours.

RESULTS/ FINDINGS HYPOTHESIS 2

Participants were woken after 5 or 15 mins after REM, and based on their recall of the dream, they had to decide which was the correct duration.

All but one could do this accurately

Significant correlation between minutes of REM and lengths of dream narratives (words)

RESULTS/ FINDINGS HYPOTHESIS 3 it was hard to

know the direction in which Ps were looking when dreaming.

They were woken up as soon as a pattern of eye movement persisted for at least a minute. Mainly vertical Mainly horizontal Vertical and horizontal Very little or no movement.

RESULTS/ FINDINGS Of 35 awakenings only 3

periods of only vertical or only horizontal.

There were several dreams and usually eye movement corresponded to what was happening in the dream.

In participants with mixed movements usually they were looking at a moving object close to them.

CONCLUSIONS Each of the 9 participants had regularly

REM periods during the night.

As predicted:

1. High incidence of dream recall ocurred when participants were woken up after REM. Low for NREM.

2. When a series of awakenings ocurred either 5 or 15 minutes after REMs had began, participants judged the correct dream duration very accurately.

3. The pattern of REMs was related to the visual imagery of the dreams.

Recording REMs during sleep objective measure of dreaming.

EVALUATION: Methodological issues

Beaumont being woken from NREM dream may lead to forgetting more than with REM

In REM sleep the brain is more active

This could be a major confounding variable that could make all these results to be questionable easily.

Herman there is no considerable difference in dream report between REM and NREM.

Foulkes: saying that REM=dreaming and NREM = non dreaming oversimplification

Although only 5-10% of NREM sleepers reported dreaming, 70% could report dream like impressions.

Besides, dreaming is also established to occur during the hypnagogic period and daydreaming.

Theoretical issues One of the great questions of

psychology is “is dreaming useful?/necessary?”

Should sleep be seen as active or passive?

Sleep is an active process not a consequence of neuronal fatigue.

The brain of a sleeping person is almost as active as the one from a person who’s awake.

SLEEP IS AN ACTIVE PROCESS

Theoretical issues Evidence has been been found for the relationship

between REM sleep and dreaming rem rebound phenomenon.

REM rebound: When people are deprived from REM sleep, the next night they “make up” for it. Compensation.

Dement: when participants were deprived from REM sleep irritable, nervous, unable to concentrate, paranoid, hallucinations, etc.

These symptoms were very possibly, consequence of Dement’s own expectations he told the Ps that this experiment could have consequences and had an available psychiatrist.

Theoretical issues Dement replicated the study and

found no evidence for psychiatric impairment in REM deprived Ps.

He also found evidence for the REM rebound

Then, possibly REM and dreaming are the most important functions of sleep.

Subsequent research 1990’s There was a change in the vision of

dreaming and REM. Dreaming appeared to be a continuous process

that also occurred during NREM periods.

NREM dreams shorter and more rationally constructed.

REM dreams more emotional and more detailed.

Subsequent research Researchers

questioned if really REM was necessary for dreaming to take place

At some point, REM sleep was linked to a brain structure called PONS (research with kittens)

Subsequent research But, evidence: people with problems in PONS

dreamt anyway.

Or people who said they had never dreamed, but had an intact pons, even though they went through REM phases.

But they had lesions in other brain structures. What is clear for this research Dream takes place independently of REM and the pons.

Subsequent researchHobson’s Activation-Synthesis

model: “REM-ON” area located in the pontine

reticular formation ACTIVATION REM sleep

This prevents most sensory information from reaching the brain.

The switch from the motor cortex is switched off, causing the person to be paralysed during REM sleep.

Other structures associated to memory and emotion are activated

In summary When REM sleep occurs:

REM-ON area: Activation (ON)

Motor cortex OFF

Memory and emotion structures ON (probably hippocampus and amygdala)

Subsequent research Dreaming occurs when these systems

activate simultaneously and are syntethized similar to a waking brain

In a waking brain

+ + + +

SENSORY INFORMATION

MOTOR INFORMATION

EMOTIONAL INFORMATION MEMORY

SENSE OF

REALITY

This information is presented in an ordered way when we are awake

Subsequent research In dreams information doesn’t

follow a logic order weird dreams The internal processes involved

in dreaming are random.

Dreams normally involves activity from the visual and motor systems.

Many dreams could be understood based on body experience erotic dreams, flying, etc, related to certain organs.

Subsequent research Reverse learning

(Crick&Mitchison) we dream in order to forget.

A complex associational network overloaded of incoming information creation of false thoughts.

These thoughts might be outdated but persistent.

REM sleep could be erasing those thoughts (unlearning)

Subsequent research Crick & Mitchison

trying to record our dreams isn’t a good idea. They are ideas we’re trying to get rid of!

This model only applies to bizarre dream content. And what about narrative?

This is better understood as dreaming to reduce fantasy or obsession.

Subsequent research The activation-synthesis

model refers to the where but not to the why or what for.

Here is where psychological (psychodynamic) perspectives come into play Freud

Freud’s theory of dreams

1900 The interpretation of dreams (S.Freud)

“Todo sueño es cumplimiento de deseo”.

Dream usually manifest certain ideas or experiences that weren’t elaborated during the day (restos diurnos)

2 types of content: Manifest content: the story or

narration itself Latent content: the meaning

(underlying)

Applications and implications

In animals, REM sleep may have evolved to access repeatedly the information useful for survival (location of food, etc)

To mantain sleep movement had to be suppressed (motor neurons) otherwise you wake up!

Eye movement wasn’t enought to wake up, so there is still access to visual information that, combined with past experience strategy for behaviour.

It might be adaptive

Applications and implications

In humans… It could be that the crucial

information for survival is the basic information in the unconscious.

We have language, animals don’t. Information is basically visual we inherited it?

But this information for us, could be useful. That’s why we remember dreams.

We dream more under stress related to difficulties. They are EMOTIONAL.

Applications and implications

Usually in mood disorders, there are alterations of sleep.

Babies have more REM sleep this suggests that maybe one of the functions of brain activation is the developing of the brain itself.