🎯 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 🌀.
🔄 Characteristics of Sleep
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 animal 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? 🧬❓
🔬 Free-Floating Sleep Cycles Experiment
Though we do have a strong focus on the day training where everyone has 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 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
🌍 Species Specific
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
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
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 polycyclic 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 night sleep ⚡, or even a nap 💤– but brain never rests! 🧠⚡❌
📚 Theories of Sleep Function
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 🐾🧬.
📊 Stages of Sleep Based on EEG Patterns
⚡ Awake State
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 (cycles per second) 📊.
🌊 Stage 1 - Alpha Waves
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 📊.
💤 Stage II - Delta Waves with Sleep Spindles
As the person goes into a deeper state of sleep he enters 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 ⚡⬆️.
😴 Stage III - Deep Sleep
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 ⚡⬆️.
💤 Stage IV - Deepest Sleep
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 💀😴.
👁️ REM Sleep - Paradoxical Sleep
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 their inhibition of all movement 🚫💪).
🔄 The 90-Minute Sleep Cycle
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 ⬆️).
💭 Dreams
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 📚💭).
🚫 Sleep Deprivation Effects
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 ⚠️👁️🚫💤😵.
⏰ Training Sleep Patterns
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 💤✅.
⚠️ Sleep Disorders
There are several sleep disorders ⚠️😴, 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
Sleep Apnea: People suffering from 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 😵—no 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
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
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
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 of Sleep
🏥 Raphe Nuclei and Serotonin
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 ⏰⬆️.
⚡ Reticular Activating System
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 ⚡👁️.
🧪 Locus Coeruleus and Norepinephrine
The Locus Coeruleus 🧠 containing Norepinephrine 🧪 is also important in sleep and awakening 😴⏰. Animals with Lesion in the locus coeruleus 🧠⚠️– spent more time in sleep 😴⬆️.
🧠 Pontine Nuclei and REM 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 🌊😴.
💤 Conclusion
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
- Carlson, N. R. (2005). Foundations of physiological psychology. Pearson Education New Zealand.
- Pinel, J. P. (2003). Biopsychology. (5th ed). Allyn & Bacon Singapore.
- Bloom, F., Nelson., & Lazerson. (2001), Behavioral Neuroscience: Brain, Mind and Behaviors. (3rd ed). Worth Publishers New York
- Bridgeman, B. (1988). The Biology of Behavior and Mind. John Wiley & Sons, New York
- Brown, T.S. & Wallace, P.S. (1980). Physiological Psychology. Academic Press, New York
- Mogensen, G. J. (1977). The Neurobiology of Behavior. Lawrence Erlbaum Associates