Finally, what is the evolutionary purpose

The gap

Evidence profile

Sourced from the future-work section and future work and discussion of the source papers, classified as general, drawn from work published between 1979 and 2026, spanning 3 journals. Those papers have been cited 324 times in total.

Supporting evidence — 3 representative gaps

• Sleep in Young and Old Rats (1979) · Journal of Gerontology · doi

  The study suggests that further research is needed to understand the underlying mechanisms of sleep patterns and aging. The research could be extended to investigate the effects of aging on sleep patterns in other animal models. The study notes that recording at intervals over the life span in individual animals could provide more insights into sleep patterns and aging.

  generalfuture-work section
  Keywords: study suggests further research needed understand underlying mechanisms
• The Biology of REM Sleep (2017) · Current Biology · cited 324× · doi

  Even though REM sleep was only identified as a distinct behavioural state in the early 1950s, considerable progress has been made in understanding its mechanisms and functions, with most of this headway being made within the past decade. And while it is undeniable that many of these advances in our understanding of REM sleep biology link to the development of new technologies (e.g., chemo- and opto-genetics), we would argue that it is the combinatorial application of these newer techniques with more classical approaches (e.g., functional anatomy, unit recording, and cellular imaging) that has truly enabled the effective probing and elucidation of the delimited circuits that drive REM sleep and, in turn, revealed how these circuits influence the function and activity of brain structures associated with learning, memory and motor control. Although scientists have made important progress in identiits fying REM sleep mechanisms and elucidating some of biological functions, many important questions remain. For example, is REM sleep actually present in all animals? While many biologists believe that sleep is a universal behaviour, we have only studied and identified sleep in a small fraction of all existing animal species. Understanding sleep biology across species, is important because such insight could provide new clues about the potential functions of REM sleep. For example, does REM sleep serve the same function in all animals? including differences, Although REM sleep appears important for certain types of learning and memory, it remains virtually unknown how REM sleep actually facilitates plasticity and learning. While recent evidence indicates that theta activity during REM sleep (Figure 1) is critical for facilitating motor learning, it remains unknown how or why theta activity promotes memory-related plasticity. It also remains unclear if REM sleep serves the same biological function(s) across the lifespan. For example, why are REM sleep amounts typically higher in young and developing animals than in older ones? These age-related differences in REM sleep amounts suggest that REM sleep function may vary across an animal’s lifespan, but what those potential functions are remains unclear. While some of the circuits underlying REM sleep generation have been identified, the full extent of REM sleep circuits remains R1244 Current Biology 27, R1237–R1248, November 20, 2017 unidentified. For example, it was only within the last several years that neuroscientists identified that structures beyond the brainstem (e.g., MCH cells in the hypothalamus) also play a critical role in modulating REM sleep. It also remains unclear how circuits that control REM sleep communicate with those that promote wakefulness and non-REM sleep. And this is a critical question in science and medicine because changes in REM sleep control are associated with some of the symptoms in narcolepsy (e.g., cataplexy).

  generalfuture workevidence 5/5
  Keywords: sleep remains identi functions circuits function learning important example made biology activity memory control animals
• Looking back: tracing the origins of sleep across the animal kingdom (2026) · Frontiers in Neuroscience · doi

  Finally, what is the evolutionary purpose of energetically expensive REM sleep activity (Mishra and Colgin, 2019) during the quiescent period? The subdivision of sleep architecture into NREM and REM sleep states complicates the element of energy conservation proposed by Freiberg and remains an open question.

  generaldiscussionevidence 5/5
  Keywords: sleep finally evolutionary purpose energetically expensive activity mishra colgin quiescent period subdivision architecture nrem states

Questions about this gap