Brain and Motivational States:Sleep and Dreams, Characteristics of sleep

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Neurological Basis of Behavior (PSY - 610)

Lesson41

Brain and Motivational States

Objectives:

To familiarize the students with the

Brain and motivational states.

Neurophysiology and biorhythms, Sleep and awakening cycles, Dreams, Sleep

disorders.

Sleep and Dreams

One of the most important motivated behaviors (ask someone who has not been able to sleep. Eminent

researchers such a Moruzzi and Magoun, Jouvet, Asertinsky and Klietman, Dement and Klietman have

contributed to the study of sleep and have tried to answer the questions of the enigma called sleep.

What is sleep? What is the function of sleep?

Sleep is certainly one of the most interesting and intriguing behaviors (or lack of it). Sleep has very

species- specific behavior patterns. Some animals sleep for 2/3rds of their life like the cats, and some

animals are light sleepers (the horse and the cows). Further the birds sleep with their beak tucked in

their feathers, and the dogs and cats sleep all curled up.

Sleep is cyclic (it follows a circadian rhythm: a day/light cycle). And you feel sleepy the same time

every night and wake up same time every morning.

Sleep is purposive- It has survival value and fulfill the system's needs (try sleep deprivation to see how

bad one feels and performs)

Sleep is also purposive that each time an animals needs to sleep it would seek its own location (or bed,

or pillows or direction)

Sleep has a high priority for survival

Sleep is one of the Circadian- Zeitgebers one of the biological rhythms which has an important

influence on behavior.

Our sleep is governed by our Internal clocks and each one of us has a unique Rhythm there are day

persons who are early to bed and early to rise and then there are the evening types who like to go to

sleep late and then wake up late. Their functional and behavioral peak is at around afternoon. How does

one determine their clock or is it biologically determined?

Though we do have a strong focus on the day training where everyone ahs to start working in the

morning- going to school and then sleep early for school net day. It appears that these external cues do

place a restriction on the biologically preferred (entrained) clock.

An experiment was carried out on volunteer students to a sleep study. These students had to live on the

site and each one was assigned a sound proof room with no windows or any other cues as to the time of

the day. There were no clocks, no newspapers delivered, and no breakfast, lunch and dinner timings.

The students could ask for the newspaper and breakfast or other meals when they so wanted. The aim

was to allow each to have free floating sleep periods. Their sleep patterns/cycles were noted before the

experiment began and during the experiment. It was noted that at the end all except one or two had 24

hour cycles, these two exceptions had cycles of >24 hours! Most interestingly there were some who had

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entirely reversed during free cycles! These had a cycle in which they stayed alert and awake during the

night and slept during the day--indicating that this was their natural cycle.

The Question still remains, why spent 1/3rd of life in sleep? About 25-30 years

It appears that sleep is non adaptive. It leaves you vulnerable for predators and enemies. It is well

known that hunters sleep deep while the hunted cannot do so.

However, sleep deprivation affects cognitive and emotional responses. It reduces attention to stimuli,

affects memory and sleep deprivation has been used as torture (by not allowing them to sleep). We

would keep coming back to this question again and again!

Characteristics of sleep

Sleep is species specific all animals are similar in some cases and different in others when they sleep:

though similar still different (birds, horses, lions)

Home territory important for sleep for all animals why? The home territory is important for sleep. Even

humans like to have their own bed, or bedding or own direction, animals have their own nests, and dens

or anywhere which is home to them? Why? It has survival value- safety and security of home would

ensure that falling asleep would be safe and comfortable and not get you killed.

Periodicity: cyclic nature of sleep. As we have already seen, sleep has a very formal cycle of 24 hours

and within this cycle are several cycles per night. This is the same for all animals. However, infants

have sleep which is polycyclic and polyphasic (they sleep and awake during the day and night- this is

because their circadian rhythm has not been trained yet), and adults are monocyclic and monophasic.

One time day (however there were many like Einstein and Leonardo Da Vinci who were polycylic and

had short sleep cycles but many of them).

Function of sleep:

The most obvious answer is to rest because you get up refreshed after a good nights sleep, or even a

nap but brain never rests!

There are many explanations given as to why one sleeps. There is the memory consolidation theory

which states that we sleep so that consolidation of memories can take place, especially during the REM

period. For young infant and growing children (especially) there appears to be sensory motor practice

during REM sleep. It also seems that REM sleep is important and needed for repair of any damage to

cells. This is continual work ongoing

Electrophysiology of Sleep.

Asertinsky and Klietman, Dement and Klietman, Jouvet, and earliest reports by Hess (1931) showed

that the sleep has very formalized stages which can be distinguished on the basis of the electrical

activity of the brain

Asertinsky and Klietman recorded EEG, EMG, and Oculomotor (EOG) movements and reported the

following changes in brain and muscular electrical activity where a person was set up with electrodes to

sleep in a sleep laboratory, and these electrodes were attached to an oscilloscope and a polygraphic

recording device which recording the stages through which the brain electrical changes moved.

Interestingly, this is a consistent pattern seen across all animal species

Based on EEG patterns we can see the distinct stages and how the sleeper moves form one stage to

another.

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In the Awake state the brain has -Beta-waves which are very high frequency low voltage low

amplitude. This means these are highly active state-the height of the waves is short and there is 12-

18 cps.

As awakes person relaxes and slows down, the brain enters Stage 1-- Alpha--waves start emerging

these are slower with lower frequency and the voltage is higher, these are about 8-12 cps.

As the person goes into a deeper state of sleep he enter Stage II-comprising of Delta waves are

about--1-4 cps really slow but high voltage waves (even slower, low freq, height of waves

increased) these are interspersed with sleep spindles of 13-15 cps and K complexes). So every now

and then there is a spurt of high frequency low amplitude waves.

Following this stage the person goes into a deeper stage the Stage III--this is known as deep sleep.

Here we see delta wave largest and slowest of slow waves 1-2 cps. It is difficult to wake a person up

in this stage. The sleep waves are really slow, with high amplitude/voltage.

The Stage IV of sleep waves slow waves and more and more Delta waves which are really slow and

large in height. It appears as if the person is in a coma

Suddenly there is change in electrical activity. If we just look at the brain EEG we see Awake like

pattern of Stage I sleep with theta waves but there is loss of muscle tone in the neck, and there is

rapid eye movement: This is REM sleep or Rapid Eye Movement sleep. It is also called PS or

paradoxical sleep disappearance of tonic activity in muscles especially neck. The person appears

paralyzed, except for the eyes (there is a good reason for this : If you were doing all the things you

were dreaming about, you would hurt yourself... therefore the body is under the control of the pons

and there inhibition of all movement).

This is a 90-minute cycle and there are repeated cycles of 90 minutes. Every 90 minutes the person

wakes up and then goes to sleep again however, there is more and more REM sleep towards morning

(out of the 90 minutes REM is for a few minutes towards the early part of the cycle, but towards the

morning it increases.

The REM sleep is the sleep during which you dream. When people are woken up during this stage,

80% report that they have been dreaming (Hartmann 1967).

Dreams are difficult subject: but there have been theories of why dream occur and during REM sleep.

Freud talked about dream expresses unconscious desires, but there have been primitive tribes who

actually train their young to fight their foes in dream (face an anaconda). The research on dreams is an

active area (please refer to Dreaming: Journal of the association of the study on dreams)

What if you deprive someone of sleep? You know that this has an adverse effect on functioning. But

REM sleep if deprived has disastrous consequences to the point of psychotic like features.

Can you train to sleep more or less? Yes you can. Da Vinci was a very prolific artist, architect, and

scientist, writer he had trained himself to sleep every 4 hours sleep for 15 minutes and then he would

wake up fresh to work

Napping it is polyphasic (similar to the sleep of babies and young children) Einstein used to take short

naps and his sleep need was satisfied

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Sleep disorders:

There are several sleep disorder, the most common of which is insomnia (which we all have gone

through at some point in time), or hypersomnia where you want to sleep ( and I know many young

people who go through these stages. This is related to hormonal states and even body energy levels

Sleep apnea:

People suffering form this disorder keeps waking up during the night because they cannot breathe. They

stop breathing and therefore wake up repeatedly. This is due to loss of contraction of the diaphragm

which occurs when involuntary control of sleep takes over (remember in REM all muscles are

paralyzed!). One patient woke up 360 times a night--n o wonder he reported being tired during the

day!! There are surgical procedures such as tracheotomy which help patients who have a severe form of

this disorder

Nocturnal myoclonus: is the twitching of legs at night or Restless legs where one person keeps waking

up because of the legs twitching involuntarily

Narcolepsy: is also known as REM attack. This is a very serious as well as an interesting disorder. In

this disorder, the person moves directly form the waking state into the REM sleep. The body loses tone

and the person becomes flaccid-REM attacks are sudden and can be dangerous. Especially if the person

is driving a car or doing some heavy machinery work. Amphetamine is used for treating patients

suffering form this disorder

Sleep paralysis:

When you wake up but feel unable to move upon waking up. The muscles are still under the inhibitory

control of pontine gigantocellular nuclei which stop the body from moving during REM sleep.

Brain correlates:

Jouvet has identified the Raphe nuclei as the critical are in sleep. Jouvet lesioned the Raphe nuclei of

cats, destroying about 80% of serotonin. This led to Insomniac cats. Similarly PCPA also reduced sleep

of cats for over 200 hours.

Moruzzi and Magoun (1949) showed that if the Reticular Formation (now known as the Reticular

Activating system) of animals are electrically stimulated it leads to desynchronization of all electrical

activity of the brain. Sleep animals wake up, awake becomes alert

The Locus Coeruleus containing Noerepinephrine is also important in sleep and awakening. Animals

with Lesion in the locus coeruleus spent more time in sleep

The Pontine nuclei are important because of their involvement in REM sleep. There is a group of cells

known as the Gigantocellular Tegmental field (FTG: Giant cells of the tegmentum) which control the D

sleep. Animals can sleep but the sleep is restricted to slow wave sleep.

Thus, we have seen that sleep is very important, and we are still waiting to find out why we sleep! Sleep

is an important motivated and survival behavior

References:

1. Carlson N.R. (2005) Foundations of Physiological Psychology Allyn and Bacon, Boston

2. Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore

3. Bloom F, Nelson and Lazerson (2001), Behavioral Neuroscience: Brain, Mind and Behaviors (3rd

edition) Worth Publishers New York

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4. Bridgeman, B (1988) The Biology of Behavior and Mind. John Wiley and Sons New York

5. Brown,T.S. and Wallace.(1980) P.M Physiological Psychology

Academic Press New York

6. Mogensen, G.J. (1977) The Neurobiology of Behavior. Lawrence Erlbaum Associates

Note: References 2, 5, 6 more closely followed in addition to the references cited in text.

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