theta&quot; activity , which is typical of drowsiness and the lightest sleep (stage 1). In contrast, &quot;beta&quot; activity , typically 15-25 Hz, consists of fast waves of low amplitude that are foundmostly in the waking, alert cerebrum. &quot;Alpha&quot; EEG activity is in the range 8-11 Hz, and appears during relaxed wakefulness, when there is little or no visual input (especially when the eyes are shut or staring at a blank wall). There are some other, more transient EEG activities found only during sleep, such as &quot; K complexes&quot; and &quot;spindles &quot;, which are both most evident in stage 2 sleep. The former seems to be associated with brief arousals often in response to external stimuli , and the latter, probably more with the the brain's active blocking of arousals .
The test entails the simultaneous recording of the electrical activity of the brain ( EEG ), eye movements (EOG), skeletal muscle activation ( EMG ), and heart rhythm ( ECG ). In the 1970s , respiratory airflow and respiratory effort indicators were added along with peripheral pulse oximetry following the identification of the sleep disorder Sleep apnea . Polysomnography is used to diagnose many types of sleep disorders including narcolepsy, restless legs syndrome, REM behavior disorder, parasomnias, and sleep apnea.
The locus coeruleus (situated in the brainstem) is responsible for the paralysis, and the destruction of this area in cats produces &quot;REM sleep without atonia&quot; (Morrison, 1983)
Assessment of chronotype using the MCTQ database (N≈25,000). (A)Age distribution within the database. (B) Distribution of chronotypes. (C) Age-dependent changes in average chronotype (±SD) are highly systematic (except for the age groups of 19, 21,22, and 23, all other age-dependent averages ± SD are significantly different from that of age group 20; t-test, p < 0.001). (D) Age-dependent changes of chronotype are different for males and females (filled circles and black line: females; open circles and gray line: males). Gray areas indicate significant male–female differences (t-test, p < 0.001).
Hypnograms demonstrating typical sleep characteristics in young adults and elderly persons. Compared with young adults, the elderly tend to have delayed sleep onset, fragmented sleep, early-morning awakening and decreased time in sleep stages 3 and 4. (REM=rapid eye movement)
Sleep Apnea: repetitive episodes of complete or partial airway obstruction. The most common complaints are excessive daytime sleepiness and frequent awakenings, but there can also be associated bruxism (grinding of teeth), dry mouth on awakening, morning headaches, erectile dysfunction, memory deficits, and snoring. Restless Leg Syndrome: itching or burning sensation in the legs which occurs when the patient is relaxed, particularly when trying to go to sleep. This is followed by movement of the legs with relief of the sensation. Kidney problems are an important cause of restless legs syndrome, and prevalence may be as high as 40% Arousal Disorders: occur in non-REM sleep, especially in the deeper stages (slow wave sleep). Confusional arousals (“sleep drunkenness”) consists of confusion, sometimes accompanied by stumbling and slurring, on awakening and can last for several minutes. Sleep Wake transition: These disorders usually occur as the person is falling asleep or waking up. Examples include sleep starts (sudden sometimes violent jerking on falling asleep) and sleep talking (“somniloquy”). Head banging (rhythmic movement disorder) REM Sleep : Sleep paralysis occurs when the normal paralysis present during REM persists into wakefulness, called Cataplexy. hypnic hallucinations are dream images that persist into wakefulness. REM sleep behavior disorder also consists of the absence of normal paralysis during REM sleep. Because muscles remain functional, these patients can move about as they dream.
Increased cell division rates are also observed towards the send of the sleep period, but these seem to be controlled by an circadian oscillator rather than GH surges, that are due to sleep, as in sleep deprived patients, the cell division occurs at around the same period.
All error bars represent s.e.m. See the text for further details. Green bars, performance without intervening sleep or without sleep on the first post-training night. Dark red bars, performance after normal sleep. Visual: After consolidation takes place during this first post-training night, no improvement is seen throughout the second day (Fig. 3a). But additional nights of sleep produce further improvements (Fig.3c). Thus, the sleep-dependent process of memory enhancement continues for at least 48–96 hours, an order of magnitude longer than the time thought to be required for the stabilization component of consolidation. Motor: subjects improve over a night with sleep, but not over an equivalent period of daytime wake (Fig. 3g)16. As with the visual discrimination task’s nap studies, training on the task alters subsequent sleep16, in this case leading to a localized increase in the strength of SWS-associated EEG slow waves recorded over portions of the right parietal cortex implicated in task performance of this task (Fig. 3j)21, and this increase correlates with subsequent sleep-dependent improvement in performance ( r 0.86, P 0.005; Fig. 3h)9
Evolution of sleep
Patterns and Functions of Sleep Gaurav Moghe Department of Biochemistry The Maharaja Sayajirao University of Baroda Presentation for 4 th SERC School in Chronobiology, 2006 Annamalai University
SOME FACTS ABOUT SLEEP <ul><li>Sleep has been regarded “sacred” in many cultures. </li></ul><ul><li>Most higher organisms show sleep or sleep-like behavior. </li></ul><ul><li>In humans, sleep deprivation causes many health and behavior related problems. </li></ul>
QUESTIONS <ul><li>How to “define” sleep? </li></ul><ul><li>Do all organisms sleep? </li></ul><ul><li>How does our own sleep pattern develop after birth? </li></ul><ul><li>Why do we spend 1/3 rd of our lives sleeping? What is the “function” of sleep? </li></ul>
STAGES OF SLEEP <ul><li>Sleep has been traditionally judged by behavioral criteria: </li></ul><ul><li>1. Minimal movement </li></ul><ul><li>2. A typical sleep posture </li></ul><ul><li>3. Reduced responsiveness to ext. stimuli </li></ul><ul><li>The event of sleep has been physiologically classified into 2 types </li></ul>REM NREM
Polysomnographic record of REM sleep. Red Box:EEG
Distribution of some key sleep regulating neuronal populations plotted on the saggital section of the rat brain Nature, Oct 2005
AMPHIBIANS, REPTILES AND BIRDS <ul><li>Amphibians and Reptiles have a primitive nervous system that does not generate the same electrophysiological patterns as higher brains of mammals and birds. </li></ul><ul><li>29 bird species have been shown to “sleep” with one of the two eyes closed. </li></ul><ul><li>It is suspected that some birds sleep aloft during transoceanic flights </li></ul>
SLEEP IN CETACEANS EEG of adult beluga EEG Of Beluga vs Rat Nature, Oct 2005
SLEEP IN INSECTS AND OTHER INVERTEBRATES <ul><li>Correlates of sleep have been demonstrated in </li></ul><ul><li>1. Drosophila ( Molecular markers ) Science, March 2000 </li></ul><ul><li>2. Crayfish ( Slow wave activity ) PNAS, Aug 2004 </li></ul><ul><li>3. Cockroaches, wasps </li></ul>
WHAT DOES ALL THIS TELL US? <ul><li>All higher animals HAVE TO sleep. </li></ul><ul><li>The pattern of sleep may vary according to the ecological niche of the organism </li></ul><ul><li>The NEED for Sleep may have some physiological correlate. </li></ul>
INFANCY TO OLD AGE <ul><li>Sleep events tend to be fragmented in infancy and in old age </li></ul><ul><li>A normal sleep pattern exists for most period of our lives. </li></ul><ul><li>How this sleep pattern develops is an interesting aspect to study. </li></ul>
Shows 4388 points of data collected over 616 days for Beatrix Valentina MacNeill
ADOLESCENT SLEEP PATTERNS Current Biology, 2004
Comparison of sleep cycles in young and elderly NEJM, 1974
DISORDERS DUE TO SLEEP RELATED PROBLEMS <ul><li>Sleep Apnea </li></ul><ul><li>Restless Leg Syndrome </li></ul><ul><li>Insomnia </li></ul><ul><li>Arousal Disorders </li></ul><ul><li>Sleep-Wake transition disorders </li></ul><ul><li>REM Sleep associated parasomnias </li></ul>
THEORIES OF FUNCTION <ul><li>The theories that have been proposed are: </li></ul><ul><li>Wear and Tear of the body </li></ul><ul><li>Memory Consolidation </li></ul><ul><li>Ecological niche theory </li></ul>
WEAR AND TEAR HYPOTHESIS Baseline sleep Deprivation Sleep after deprivation JPN, 1991 GH LEVELS
MEMORY CONSOLIDATION THEORY <ul><li>Sensory memories are consolidated during REM or Deep Sleep. </li></ul><ul><li>Sleep Deprivation led to poor performance in specific tasks, in 3 studies, and improved after a period of sleep: </li></ul><ul><li>1) Visual texture discrimination task </li></ul><ul><li>2) Motor sequence learning task </li></ul><ul><li>3) Motor adaptation learning task </li></ul><ul><li>The improvements showed strong correlations to specific stages of sleep and specific regions in the brain </li></ul>
Visual Texture discrimination Motor adaptation learning
SOME OTHER SUPPORTS <ul><li>Zebrafinch </li></ul><ul><li>Rats </li></ul><ul><li>Sheep </li></ul><ul><li>Fetal and Neonate psychology </li></ul>
ECOLOGICAL NICHE THEORY <ul><li>Predator-Prey relationships affect the patterns of sleep </li></ul><ul><li>Evidences proposed include: </li></ul><ul><li>1) Newborns sleep more than adults </li></ul><ul><li>2) This pattern is reversed in aquatic mammals </li></ul><ul><li>3) Distinct correlation between predator-prey status and sleep periods </li></ul><ul><li>But is this logic sufficient to explain why humans spend 1/3 rd of their lives sleeping? </li></ul>
FUTURE DIRECTIONS <ul><li>Are sleep-like states present in lower organisms, esp those that don’t have a “nervous system”? </li></ul><ul><li>What are the cytological and molecular aspects of memory consolidation? </li></ul><ul><li>How can the harmful effects of sleep deprivation be prevented? </li></ul>