Artificial neural networks are modeled from the biological neural networks that make up our brains; they are used to enable computers to learn similarly to how our brains learn. For example, we learn to differentiate concepts over time by repetition, after seeing so many varieties of trees and of flowers, we learn what is the template of a tree, and can recognize trees in the future even if it is a new variety. An artificial neural network acts in similar fashion; connections between artificial neurons become strengthened over time if they are frequently activated together, in what's termed "Hebbian" learning.
Rapid eye movement sleep (REM sleep, REMS) is a unique phase of mammalian sleep characterized by random movement of the eyes, low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. This phase is also known as paradoxical sleep (PS) and sometimes desynchronized sleep because of physiological similarities to waking states, including rapid, low-voltage desynchronized brain waves. Electrical and chemical activity regulating this phase seems to originate in the brain stem and is characterized most notably by an abundance of the neurotransmitter acetylcholine, combined with a nearly complete absence of monoamine neurotransmitters histamine, serotonin, and norepinepherine. The cortical and thalamic neurons of the waking or paradoxically sleeping brain are more depolarized--i.e., can "fire" more readily--than in the deeply sleeping brain. The right and left hemispheres of the brain are more coherent in REM sleep, especially during lucid dreams. REM sleep is punctuated and immediately preceded by PGO (ponto-geniculo-occipital) waves, bursts of electrical activity originating in the brain stem. These waves occur in clusters about every 6 seconds for 1–2 minutes during the transition from deep to paradoxical sleep.
Foregoing a good night's sleep may wreck the brain's ability to make new memories. A new study from Johns Hopkins University School of Medicine demonstrated that a key purpose of sleep is to recalibrate the brain cells responsible for learning and memory, solidifying lessons learned for when the sleeper is awake. Using a mouse model, the researchers discovered several important molecules that govern the recalibration process, as well as evidence that sleep deprivation, sleep disorders and sleeping pills can interfere with the process. Graham Diering, Ph.D., the postdoctoral fellow who led the study, explained that the results from the mouse study can be used to make determinations about the human brain. "Our findings solidly advance the idea that the mouse and presumably the human brain can only store so much information before it needs to recalibrate," he said in a statement.
Oneirology (/?n??r?l?d?i/; from Greek???????, oneiron, "dream"; and -?????, -logia, "the study of") is the scientific study of dreams. Current research seeks correlations between dreaming and current knowledge about the functions of the brain, as well as understanding of how the brain works during dreaming as pertains to memory formation and mental disorders. The study of oneirology can be distinguished from dream interpretation in that the aim is to quantitatively study the process of dreams instead of analyzing the meaning behind them. The first recorded use of the word was in 1653.[citation The field gained momentum in 1952, when Nathaniel Kleitman and his student Eugene Aserinsky discovered regular cycles.
Two years ago, scientists in Japan reported the discovery of a mouse that just could not stay awake. This creature, which had a mutation in a gene called Sik3, slept upwards of 30 percent more than usual: Although it awoke apparently refreshed, it would need to snooze again long before its normal lab mates' bedtime. It was as if the mouse had a greater need for sleep. Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences. Now, after examining the brain chemistry of sleep-deprived mice and the ones with the Sik3 mutation, a second research group at the International Institute of Integrated Sleep Medicine at the University of Tsukuba has identified tantalizing differences in the state of 80 proteins that well-rested, normal mice do not share.