Describe the research in Psychology|Legit essays

Posted: March 3rd, 2023

In 1-2 pages, summarize the journal article. Describe the research/study conducted. Summarize the results/key findings. Explain future implications of the findings.


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Sleep remains one of the least understood phenomena in biology—even its role in synaptic plas- ticity remains debatable. Since sleep was recognized to be regulated genetically, intense research has launched on two fronts: the development of model organisms for deciphering the molecular mechanisms of sleep and attempts to identify genetic underpinnings of human sleep disorders. In this Review, we describe how unbiased, high-throughput screens inmodel organisms are uncov- ering sleep regulatory mechanisms and how pathways, such as the circadian clock network and specific neurotransmitter signals, have conserved effects on sleep from Drosophila to humans. At the same time, genome-wide association studies (GWAS) have uncovered �14 loci increasing susceptibility to sleep disorders, such as narcolepsy and restless leg syndrome. To conclude, we discuss how these different strategies will be critical to unambiguously defining the function of sleep.

Sleep remains one of the big mysteries in biology. As a state that

seemingly freezes all productive activity and puts animals in

danger of being caught by predators, sleepmust serve an impor-

tant purpose because it has survived many years of evolution.

Nevertheless, the function of sleep and the molecular processes

that produce the need to sleep both remain elusive (Frank, 2006;

Mignot, 2008). In the past decade, researchers have made prog-

ress in addressing fundamental questions regarding sleep, and

several clinical centers have even established sleep as an inde-

pendent medical discipline. Major advances include the identifi-

cation of molecules regulating sleep (Allada and Siegel, 2008;

Andretic et al., 2008a; Cirelli, 2009; Crocker and Sehgal, 2010)

and the realization that sleep disorders are extremely common

and numerous. These disorders include insomnia, breathing

disturbances during sleep (i.e., sleep apnea), movement

disorders during sleep (i.e., restless leg syndrome, periodic leg

movements), and sleep-wake state dissociation disorders (i.e.,

narcolepsy, rapid eye movement [REM] sleep behavior disorder,

sleep walking).

It is now clear that sleep is genetically controlled. Although

environmental factors can impact the duration and intensity of

sleep, genetic regulation is borne out by the heritability of sleep

traits (Ambrosius et al., 2008; De Gennaro et al., 2008), the iden-

tification of specific genetic polymorphisms that affect these

traits (Maret et al., 2005; Tafti et al., 2003), and the existence of

familial sleep disorders. Genetic model systems—zebrafish, fruit

flies, and worms—were recently developed for studying sleep,

and they are starting to reveal the molecular underpinnings of

sleep (Allada and Siegel, 2008; Andretic et al., 2008a; Cirelli,

2009; Crocker and Sehgal, 2010). Some researchers may ques-

tion the relevance of these model organisms for mammalian

sleep. However, we contend that the function and regulation of

sleep are likely conserved through evolution, and thus, it would

194 Cell 146, July 22, 2011 ª2011 Elsevier Inc.

be strange to restrict sleep research to only a few species. For

example, some would argue that the worm sleep model, which

consists of developmental periods of low activity (i.e., quies-

cence), is dramatically different from human sleep, but we note

that characteristics of sleep vary greatly even among different

mammalian species. Indeed, the genetic model systems for

studying sleep may not recapitulate all aspects of human sleep,

but the prediction is that some key features will be conserved. As

we describe in this Review, molecular and genetic studies in

these model systems are, in fact, beginning to uncover regula-

tory mechanisms underlying sleep, which are conserved from

worms to mammals.

Molecular Insights from Animal Models The idea of using model systems to understand a biological

process of interest is clearly not new. However, until about

a decade ago, studies of sleep were primarily restricted to a

few mammalian and avian species. This restriction was partially

because sleep was defined on the basis of altered brain electri-

cal activity, recorded through electroencephalograms (EEGs),

and this definition was not easily applied to other animals.

EEGs reveal three major states of behavior: wake, rapid eye

movement (REM) sleep, and non-REM (NREM sleep). In hu-

mans, REM and NREM sleep occur in 90 min cycles through a

night of sleep. NREM sleep is divided into stages 1–3, which

together with REM constitute the normal ‘‘sleep architecture.’’

Furthermore, human sleep is mostly consolidated into a single

period during the night. This phenomenon is observed in only

a few other mammals that, compared with humans, have less

consolidated sleep and wake periods, which alternate during

the day and night. Slow wave sleep is the deepest stage of

sleep, and this occurs during stage 3 of NREM. Many brain

areas are active during REM sleep; thus, the quiescence in



neural activity typically associated with sleep actually occurs

during NREM sleep.

Although the EEG definition of sleep, which is based upon

electrical activity patterns at the cortical level, precluded its

study in animals that do not have a well-defined cortex, pioneer-

ing efforts of a few researchers identified sleep-like states in

several species of fish, reptiles, amphibians, and even some

invertebrates, such as cockroach, bees, and octopus (Campbell

and Tobler, 1984). These researchers proposed specific behav-

ioral criteria to define sleep, but such practice was not widely

accepted. What eventually changed the field was the realization

that other fields hadmade rapid progress by using simple animal

models (Hendricks et al., 2000b). In particular, circadian biology

was often cited as an example of a field in which molecular

mechanisms identified in flies and fungi turned out to be

conserved in humans (Hendricks et al., 2000b). Thus, sleep

researchers developed simple animal models by using primarily

the criteria for


The article highlights the progress made in the last decade regarding the understanding of sleep’s fundamental questions, such as its molecular processes and the purpose it serves. Researchers have identified molecules regulating sleep, and sleep disorders are now recognized as common and numerous. It is now clear that sleep is genetically controlled, and genetic model systems have been developed for studying sleep. These systems are starting to reveal the molecular underpinnings of sleep, which are conserved from worms to mammals. The research conducted is essential in defining the function of sleep and provides new insights into the regulation of sleep. In the future, this research could help identify new treatments for sleep disorders and aid in developing methods to regulate sleep patterns in individuals with disrupted sleep.

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