PSYCHOPHYSIOLOGY OF SLEEP AND DREAMS, Lecture notes of Psychopedagogy

Download PSYCHOPHYSIOLOGY OF SLEEP AND DREAMS and more Lecture notes Psychopedagogy in PDF only on Docsity! PSYCHOPHYSIOLOGY OF SLEEP AND DREAMS Definition • Sleep is a readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbence and immobility. It interrupts wakefulness periodically in vertebrate organisms Types of Sleep ▪ Sleep ▪ periodic, natural, reversible loss of consciousness ▪ Sleep Stages 1. Stage 1 – 4 2. Stage 4 is known as Deep Sleep and the stage where sleepwalking and sleeptalking occur. It’s difficult to wake someone up from Stage 4 sleep. ▪ REM (Rapid Eye Movement) Sleep Stage 1 Stage 1 is the beginning of the sleep cycle, and is a relatively light stage of sleep. Stage 1 can be considered a transition period between wakefulness and sleep. In Stage 1, the brain produces high amplitude theta waves, which are very slow brain waves. This period of sleep lasts only a brief time (around 5-10 minutes). If you awaken someone during this stage, might report that they weren't really asleep Phase one begins as soon as the sun sets, when the pineal gland starts to release melatonin, a hormone released in the absence of light and responsible for making us sleepy. Stage 3 Deep, slow brain waves known as delta waves begin to emerge during stage 3 sleep. Stage 3 is a transitional period between light sleep and a very deep sleep. After Phase two is over, the sleeper falls into a deeper sleep. During this stage, the sleeper falls deeper into phase three which lasts about 5 to 15 minutes Stage 4 Stage 4 is sometimes referred to as delta sleep because of the slow brain waves known as delta waves that occur during this time. Stage 4 is a deep sleep that lasts for approximately 30 minutes. Bed-wetting and sleepwalking are most likely to occur at the end of stage 4 sleep ,at which the first dream occurs stage 5 Most dreaming occurs during the fifth stage of sleep, known as rapid eye movement (REM) sleep. REM sleep is characterized by eye movement, increased respiration rate and increased brain activity. REM sleep is also referred to as paradoxical sleep because while the brain and other body systems become more active, muscles become more relaxed. Dreaming occurs because of increased brain activity, but voluntary muscles become paralyzed = Measuring sleep activity iar ee E ‘ “ t lele sy ra eS Gad AA Pe * { : ie _ tow The : | . f Left eye movements ‘, i} mertaseepiel Vy A Met dg Py ne te Right eye movements Se nw . 1 - te EMG (muscle tension) EEG (brain waves) a HE af ca eels Brain Waves and Sleep Stages ▪ Alpha Waves ▪ slow waves of a relaxed, awake brain ▪ Delta Waves ▪ large, slow waves of deep sleep ▪ Hallucinations ▪ false sensory experiences REM Sleep ▪ REM (Rapid Eye Movement) Sleep ▪ vivid dreams/ bizarre imagery ▪ Tonic immobility / active brain ▪ “paradoxical sleep” • muscles are generally relaxed, but other body systems are active ▪ Blind individuals experience this ▪ Erections A)Physiological characteristics • EEG activity (Figure, 7): For all practical purposes, the electro-enecphalogram (EEG) defines the presence of NREM sleep in the human. It has been possible to describe four EEG stages according to the depth of sleep. Stage I EEG; consists of a mixture of low voltage irregular relatively fast (more than 14 c/sec.) waves. This stage corresponds to light sleep. Stage 4; consisting of high voltage slow wave activity (below 3 c/sec.) coincides with the maximum depth of sleep. The latter stage occurs mostly in the early hours of the night. • Oculomotor activity: The eyeball activity during NREM sleep is characteristically slow and pendulous side to side movement. The appearance of these slow oscillations of the eyes is parallel to the abrupt transmission from wakefulness to sleep. Psychologically, it corresponds to the change of mental content from the conceptual mode of thinking to the perceptual mode, i.e., from ideas to images. This is called hypnagogic imagery. • Level of consciousness and attention : The onset of sleep is associated with an abrupt and generally diminishing level of consciousness. The depth of sleep varies throughout the night sleep. Periods of deep sleep are interrupted by short intervals of light sleep. The pattern of variation of sleep depth is characteristically individual and more or less constant from night to night. • Attention is diverted first from the external environment to preoccupation and uncontrolled imaginative thinking. The moment one enters sleep, the thoughts are transformed into images and attention to external environment is lost completely. • Sensory responsiveness :Sleep is marked by abrupt change in sensory responsiveness. External stimuli lose their significance and cannot be perceived. However, selective response to some relevant and important stimuli may occur, e.g., the mother is immediately awakened by the cry of her infant, inspite of deep sleep and does not respond to other stimuli. II-REM Sleep This type of sleep is also called dreaming, paradoxical, fast. A) Physiological characteristics • Cardiovascular activity :The heart rate accelerates slightly, blood pressure rises, peripheral vasoconstriction and increase in the cerebral blood flow occurs . • Respiratory activity :Respiration becomes more rapid and irregular, together with episodic shallow respiratory movements. There is also an increase in O2 consumption during REM sleep. • G.I.T activity :Slight elevation of gastric acid secretion and dramatic rise in peptic ulcer patients, occur in REM sleep. • Genito-urinary activity :Decrease in urinary output penile erection and emissions occur during REM sleep. • Skin changes :Decrease of the skin resistance is recorded. • Muscular activity :REM sleep is characterized by the presence of peripheral twitching movements of the limbs and facial muscles together with inhibition of the muscle tone between the twitches. Reflexes are also suppressed • Dream experiences during REM sleep appear to be more vivid, complex, associated with emotional experiences and variable, than those during NREM sleep and easily recalled. The dream content can be influenced by external stimuli, pre-sleep experience, certain chemical agents and hypnosis. • In young adults, REM sleep, interrupts NREM sleep on the average of once every 90 minutes, lasts approximately 20 min. and accounts for 20 to 25% of the total sleeping time. In the cat, dreaming periods last about seven min. and NREM sleep 10- 20 min. The periods devoted to dreaming sleep vary according to age. In the immediate neo-natal period in humans, REM sleep occupies 50% or more of the total sleeping time. • Therefore, the infant, sleeping most of the day, experiences about 4-8 times as much dreaming sleep as the adult. An even greater percentage of REM sleep occurs in the premature infant. This suggests that the fetus spends all his time in dreaming sleep II-REM Sleep A.Neuro-anatomical mechanism: REM sleep seems to depend on the integrity of a sleep center located in the pontine RF since lesions here abolish it totally. A.Biochemical mechanism: REM is relatively constant from day to day in contrast to NREM sleep, which is variable in duration. Certain compounds increase REM sleep, such as tryptophan, 5 HTP (serotonin) and, LSD. Monoamine compounds and compounds that affect monoamine metabolism will selectively block REM sleep, e.g., Dexedrine, parnate and reserpine. Sleep Deprivation ▪ Effects of Sleep Loss ▪ fatigue ▪ impaired concentration ▪ depressed immune system ▪ greater vulnerability to accidents Sleep Deprivation 2,400 2,700 2,600 2,500 2,800 Spring time change (hour sleep loss) 3,600 4,200 4000 3,800 Fall time change (hour sleep gained) Less sleep, more accidents More sleep, fewer accidents Monday before time change Monday after time change Accident frequency Comparison between Psychophysiological Characteristics of NREM and REM Sleep (table, 2)