Why we sleep and why we dream are questions we’ve asked since the beginning of recorded history. From ancient Egyptian Sleep Temples to classical Greco-Roman poems and philosophies, these artifacts illuminate how understanding ourselves and the world around us drives our endless quest for good rest and good health. And through the ages, as ideologies evolved and nature’s mysteries were slowly solved, the link between slumber and neural activity began to take form.

A Sleep Renaissance

In the 17th century, philosophers and scientists alike started to theorize about (and attempt to visualize) the structure and functions of the human brain. Not long after Shakespeare penned his famous play chronicling Macbeth’s haunted, sleepless nights (while The Bard himself feverously wrote and suffered through long stretches of insomnia), across the English Channel, famous French philosopher and mathematician Rene Descartes began documenting his theory of mind-body dualism (Thorpy, Sleep Medicine: A Comprehensive Guide to Its Development, Clinical Milestones, and Advances in Treatment, Springer, 2015).

Influenced by Plato and other classical thinkers, Descartes’ philosophy posits that the mind and the body are separate entities. The mind has consciousness, intelligence, and self-awareness, but no physical form (Thorpy, Springer, 2015). He created a model for his vision of a brain at sleep, where nerves become relaxed and ventricles dilated to allow for dreaming.

English physician William Harvey’s discovery that the heart pumped blood to the rest of the body laid the groundwork for fellow physician Thomas Willis to document the most accurate account of the nervous system to date in his 1667 book Pathologiae Cerebri (Monteiro et al., Brazilian Journal of Psychiatry, vol. 44, no. 3, 2022). A contender for the title of “father of modern neurology,” Willis made significant contributions to contemporary understanding of brain disorders and their treatments. And while his peers rightfully questioned his hypothesis that “animal spirits” caused changes in the brain that influenced dreaming, the ways that he thought of the brain and its behaviors was not unlike our modern understanding of nerve impulses (Monteiro et al., Brazilian Journal of Psychiatry, 2022).

The Brain Takes Center Stage

French physicist (or as he was labeled in the early 18th century, “natural philosopher”) Jean-Jacques d'Ortous de Mairan conducted the first scientific experiments to document biological circadian rhythms in 1729. Fascinated with how flowers open in the morning and close in the evening, he recorded how their patterns and growth continued even in the absence of sunlight (Society for Research on Biological Rhythms, Sept. 23, 2019). The realization that living organisms (from plant life to people) have circadian rhythms, or “internal clocks,” independent from their environments was a leap forward in how scientists and philosophers thought about sleep patterns and brain behavior.

Curiosity about human anatomy and the mind continued to captivate the scientific community at the turn of the 19th century. In 1809, Italian anatomist Luigi Rolando conducted a series of studies on birds and other animals that helped confirm the previously theoretical connections between areas of the brain and sleep. His tests revealed that removing the cerebral hemisphere induced a sleep-like state, setting a foundation for future research and discovery (Kushida, History of Sleep Physiology and Medicine, Chest, 2011).

And while her name is not as widely known as some of her contemporaries, Maria Mikhaĭlovna Manàsseina was born in 1841 and become one of the first women in Europe to graduate with a degree in medicine. Her revolutionary sleep deprivation studies showed that the negative impacts of sleep loss begin in the brain and that sleep, as long suspected, is indeed essential for maintaining health and life (Palagini, Antrobus & Kay, Research Directions: Sleep Psychology, Cambridge University Press, 2023). Her work inspired others around the globe to continue in her footsteps.

A Lightbulb Moment in Sleep History

The first technological disrupter to our collective circadian rhythms entered the scene in October of 1879, when American inventor Thomas Edison perfected the design of the first incandescent lightbulb for commercial use. While light bulbs existed before Edison’s contribution, electricity wasn’t available to large segments of the population prior to his patented system for widespread distribution (Harvard Medical School Division of Sleep Medicine, updated Oct. 1, 2021). Over the next fifty years, as more households gained access to electricity, they experienced increased exposure to artificial light. As a result, their brains were tricked into thinking that daylight lasted longer – stimulating neural activity and suppressing melatonin levels that help us fall asleep (Harvard Medical School Division of Sleep Medicine, 2021).

The Age of Enlightenment brought tectonic shifts in intellectual and cultural thought, as scientific discovery crept ever closer to the identification of sleep stages and the role of Rapid Eye Movement (REM). This single discovery would become a game-changing moment in our understanding of dreams, cognition, and the power of a great night’s sleep.

FAQs

Who first studied biological circadian rhythms?

French scientist Jean-Jacques d'Ortous de Mairan is generally credited with conducting the first controlled experiments demonstrating circadian rhythms in 1729 when he observed plant movements continuing in constant darkness.

Why is Thomas Willis important in sleep history?

Willis helped establish the scientific study of the brain and nervous system, laying groundwork for modern neuroscience and later sleep research.

Did scientists understand dreaming before REM sleep was discovered?

Yes. Philosophers and physicians such as Descartes and Willis proposed biological explanations for dreaming centuries before REM sleep was identified in the twentieth century.

How did electric lights change human sleep?

Widespread electric lighting increased exposure to artificial light after sunset, reducing dependence on natural daylight cycles and influencing sleep schedules and circadian rhythms.

Sources

Thorpy, Michael. "Sleep in the Seventeenth and Eighteenth Centuries." In Sleep Medicine: A Comprehensive Guide to Its Development, Clinical Milestones, and Advances in Treatment. Springer Science+Business Media, 2015. DOI: 10.1007/978-1-4939-2089-1_11 https://einstein.elsevierpure.com/en/publications/sleep-in-the-seventeenth-and-eighteenth-centuries-2/ This scholarly historical review discusses Descartes, Shakespeare, early sleep theories, William Harvey, Thomas Willis, and Jean-Jacques d'Ortous de Mairan’s contributions to sleep science.

Monteiro, Fernanda C.; Nardi, Antonio E.; Gomes, Marleide M. "The 400th Anniversary of the Birth of Thomas Willis (1621–1675): An Invaluable Contributor to Neuroscience." Brazilian Journal of Psychiatry. Vol. 44, No. 3, 2022. PMCID: PMC9169470. Published by Associação Brasileira de Psiquiatria. https://pmc.ncbi.nlm.nih.gov/articles/PMC9169470/ Reviews Willis' role in developing clinical neuroscience and neurological anatomy.

Sobel, Jonathan. "The Birth of Chronobiology: A Botanical Observation." Society for Research on Biological Rhythms. September 23, 2019. Published by SRBR. https://srbr.org/the-birth-of-chronobiology-a-botanical-observation/ Explains de Mairan's 1729 experiment and its role in establishing the existence of endogenous circadian rhythms.

Palagini, Laura; Antrobus, John S.; Kay, Daniel B. "The Connection Between Dreaming, the Brain and Mental Functioning: Where Are We Now?" Research Directions: Sleep Psychology. Cambridge University Press. Published November 8, 2023. https://srbr.org/the-birth-of-chronobiology-a-botanical-observation/ Provides historical context for dream science and discusses Maria Manasseina's pioneering sleep research.

Harvard Medical School Division of Sleep Medicine. "Why Sleep Matters: Historical and Cultural Perspectives of Sleep." Reviewed October 1, 2021. Published by Harvard Medical School. https://sleep.hms.harvard.edu/education-training/public-education/sleep-and-health-education-program/sleep-health-education-101 Discusses major milestones in sleep research, artificial lighting, and circadian disruption.