1) Sleep is exhibited by most higher organisms and has been physiologically classified into REM (rapid eye movement) and NREM (non-REM) sleep stages.
2) The amount of daily sleep varies across mammal species from over 13 hours in lions to under 2 hours in giraffes. Evidence also suggests that some birds and marine mammals sleep with one eye open or while floating.
3) Studies in insects and other invertebrates have found correlates of sleep such as slow wave brain activity, indicating the need for sleep is phylogenetically widespread. The pattern of sleep depends on an organism's ecological niche.
2. 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
12. SLEEP PERIODS IN MAMMALS Mammals Daily sleep period (in hours) Laboratory Rat 13 Cat 12.5 Humans 8.0 Baboons 9.4 Lions 13.5 Elephants 3.1 Giraffes 1.9 Birds 30 min
22. Comparison of sleep cycles in young and elderly NEJM, 1974 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
theta" activity , which is typical of drowsiness and the lightest sleep (stage 1). In contrast, "beta" activity , typically 15-25 Hz, consists of fast waves of low amplitude that are foundmostly in the waking, alert cerebrum. "Alpha" 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 " K complexes" and "spindles ", 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 "REM sleep without atonia" (Morrison, 1983)
Assessment of chronotype using the MCTQ database (Nâ25,000). (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 maleâfemale 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 (âsleep drunkennessâ) 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 (âsomniloquyâ). 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 48â96 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 taskâs 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
