What Is Déjà Vu And Why Does It Happen?

Have you ever experienced a sudden feeling of familiarity while in a completely new place? Or the feeling you’ve had the exact same conversation with someone before? This feeling of familiarity is, of course, known as déjà vu (a French term meaning “already seen”) and it’s reported to occur on an occasional basis in 60-80% of people. It’s an experience that’s almost always fleeting and it occurs at random. So what is responsible for these feelings of familiarity? Despite coverage in popular culture, experiences of déjà vu are poorly understood in scientific terms. Déjà vu occurs briefly, without warning and has no physical manifestations other than the announcement: “I just had déjà vu!” Many researchers propose that the phenomenon is a memory-based experience and assume the memory centres of the brain are responsible for it. Memory Systems The medial temporal lobes are vital for the retention of long-term memories of events and facts. Certain regions of the medial temporal lobes are important in the detection of familiarity, or recognition, as opposed to the detailed recollection of specific events. It has been proposed that familiarity detection depends on rhinal cortex function, whereas detailed recollection is linked to the hippocampus. The randomness of déjà vu experiences in healthy individuals makes it difficult to study in an empirical manner. Any such research is reliant on self-reporting from the people involved. Glitches In The Matrix A subset of epilepsy patients consistently experience déjà vu at the onset of a seizure — that is, when seizures begin in the medial temporal lobe. This has given researchers a more experimentally controlled way of studying déjà vu. Epileptic seizures are evoked by alterations in electrical activity in neurons within focal...

Too Hot To Sleep? Here’s Why

Bushfires are quite appropriately dominating our nation’s concerns during the current Australian heatwave. But for many, the struggle to sleep through soaring temperatures is a personal inferno that dominates conversation around offices and homes across the country. Sleep and body control of temperature (thermoregulation) are intimately connected. Core body temperature follows a 24-hour cycle linked with the sleep-wake rhythm. Body temperature decreases during the night-time sleep phase and rises during the wake phase. Sleep is most likely to occur when core temperature decreases, and much less likely to occur during the rises. Our hands and feet play a key role in facilitating sleep as they permit the heated blood from the central body to lose heat to the environment through the skin surface. The sleep hormone melatonin plays an important part of the complex loss of heat through the peripheral parts of the body. MORE: Heatwave: How To Cope With Australia’s Extreme Summer Temperatures At sleep onset, core body temperature falls but peripheral skin temperature rises. But temperature changes become more complex during sleep as our temperature self-regulation varies according to sleep stage. Research has shown how environmental heat can disturb this delicate balance between sleep and body temperature. An ambient temperature of 22˚ or 23˚ Celsius is ideal. Any major variation in this leads to disturbance of sleep with reduced slow wave sleep (a stage of sleep where the brain’s electrical wave activity slows and the brain “rests”), and also results in less dreaming sleep (rapid eye movement or REM sleep). Indeed during REM sleep, our ability to regulate body temperature is impaired so in a clever sort of...

What Is Fatigue? What Causes Fatigue?

Fatigue, also referred to as tiredness, exhaustion, lethargy, and listlessness, describes a physical and/or mental state of being tired and weak. Although physical and mental fatigue are different, the two often exist together - if a person is physically exhausted for long enough, they will also be mentally tired. When somebody experiences physical fatigue, it means they cannot continue functioning at their normal levels of physical ability. Mental fatigue, however, is more slanted towards feeling sleepy and being unable to concentrate properly. Fatigue is a symptom, rather than a sign. A symptom is something the patient feels and describes, such as a headache or dizziness, while a sign is something the doctor can detect without talking to the patient, such as a rash. Fatigue is a non-specific symptom, i.e. it may have several possible causes. Mental and physical fatigue Physical fatigue - the person's muscles cannot do things as easily as they used to. Climbing stairs or carrying laden supermarket bags may be much harder than before. Physical fatigue is also known as muscle weakness, weakness, or lack of strength. Doctors usually carry out a strength test as they go about diagnosing and trying to find out the causes of individual cases of physical fatigue. Psychological (mental) fatigue - concentrating on things has become harder. When symptoms are severe the patient might not want to get out of bed in the morning, or perform his/her daily activities. Mental fatigue often appears together with physical fatigue in patients, but not always. People may feel sleepy, have a decreased level of consciousness, and in some cases show signs similar to that of an intoxicated state. Mental fatigue may be...

Severe Sleep Loss Affects Immune System Like Physical Stress Does

Sleep deprivation and physical stresshave similar effects on the immune system of human beings, researchers from the Netherlands and the United Kingdom reported in the journal SLEEP. Both physicalstress and severe sleep loss jolt the immune system into action, the authors explained. The scientists , from Erasmus MC University Medical Center Rotterdam, and the Faculty of Health and Medical Sciences at the University of Surrey, United Kingdom, compared the number of white blood cells in 15 healthy young adult males who were subjected to normal sleep and severe sleep loss. The greatest impact was on granulocytes - types of white blood cells - which lost their day-to-night time rhythmicity as numbers shot up, especially during nighttime. Lead author, Katrin Ackermann, PhD, said: "Future research will reveal the molecular mechanisms behind this immediate stress response and elucidate its role in the development of diseases associated with chronic sleep loss. If confirmed with more data, this will have implications for clinical practice and for professions associated with long-term sleep loss, such as rotating shift work." The authors explained that prior studies had found a link between lack of sleep and the development of certain diseases and conditions, such as high blood pressure (hypertension),diabetes and obesity. Other studies have demonstration that adequate sleep helps keep the immune system working properly, and that long-term sleep loss is a major risk factor for immune system problems. The 15 young men were made to follow a strict routine of eight hours sleep every day for one whole week - their white blood cells were categorized and measured. Within 90 minutes of waking up, they were exposed to 15+ minutes of outdoor light. They were not allowed to...

Sleep Apnea Has Higher Risk Of Cancer Mortality

University of Wisconsin School of Medicine and Public Health released a study today showing that those suffering from sleep apnea appear to have an increased risk of cancer mortality.  Previous studies have linked the sleep disordered breathing (SBD) problems to hypertension, cardiovascular disease, depression and earlier death, but this is the first to find a link tocancer. Lead author Dr. F. Javier Nieto, chair of the Department of Population Health Sciences at the University of Wisconsin School of Medicine and Public Health commented that the study had subjects with severe SBD had five times higher incidence of cancer deaths, more than just a statistical anomaly. Previous studies in animals have shown similar results, while other studies have linked cancer to possible lack of oxygen or anaerobic cell activity over long periods of time, therefore, it's possible poor breathing fails to oxygenate the cells sufficiently. Dr. Nieto, an expert in sleep epidemiology continued: "Clearly, there is a correlation, and we are a long way from proving that sleep apnea causes cancer or contributes to its growth ... But animal studies have shown that the intermittent hypoxia (an inadequate supply of oxygen) that characterizes sleep apnea promotes angiogenesis-increased vascular growth - and tumor growth. Our results suggest that SDB is also associated with an increased risk of cancer mortality in humans." Dr. Nieto presented his study at the American Thoracic Society 2012 International Conference in San Francisco on May 20th. His study was supported by the National Institutes of Health's the National Heart, Lung, and Blood Institute (NHLBI), the National Institute on Aging, and the former National Center for Research Resources. Dr. Susan B. Shurin, acting...
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