Behind the Veil of Hypnagogic Sleep
In the mid-1800s, August Kekulé and other German chemists were making great strides in solving puzzles in structural chemistry. One, however, remained unsolved: the structure of the compound benzene. It was a question that Kekulé was again considering as he sat one day in front of the fireplace in his apartment in Ghent, Belgium.
He had had inklings earlier of what benzene might look like, but that day, as he dozed, images hinting at its structure appeared in his mind’s eye. He later wrote that he saw dancing atoms beaded together along an invisible string, “twisting in snake-like motion.” The atoms morphed into an ouroboros: a snake that wrapped itself into a circle, eating its own tail.
The vision was epiphanic. Kekulé realized that benzene’s structure must consist of a ring of carbon atoms, each with a hydrogen atom attached. That revelation would transform scientists’ understanding of biochemistry and allow for advances in many fields, including pharmaceuticals development.
The period of repose cascading into sleep that Kekulé experienced is called hypnagogia, and it’s widely thought of as a sweet spot for creativity, a concept recently explored in a study reported by scientists at the Paris Brain Institute at the Sorbonne Université in Science in December 2021. Scientists and innovators like Kekulé, Albert Einstein, and Thomas Edison have transited this cerebral pathway in search of solutions to problems. Artists and musicians have siphoned ideas from hypnagogic hallucinations and channeled them into their work. And some writers have experienced what are sometimes referred to as linguistic intrusions during hypnagogia: Vladimir Nabokov references in his memoir Speak, Memory, “a kind of one-sided conversation […] a neutral, detached, anonymous voice,” during an onset of drowsiness.
On an electroencephalogram, electrical activity during a hypnagogic state looks most similar to electrical activity during the fourth stage of sleep — known by its acronym, REM, due to its signature rapid eye movements. The electrophysiological and phenomenological resemblances between hypnagogia and REM sleep are unexpected. When a person is awakened during stage 1 sleep, a period during which most hypnagogic hallucinations occur, they typically don’t even realize they’ve been asleep. By contrast, REM sleep is the deepest stage of sleep and is fertile ground for intense, more narrative-driven dreams.
There’s yet another similarity between hypnagogia and REM sleep. “Hypnagogia involves a lot of activity in the secondary visual cortex,” explains Dierdre Barrett, an HMS lecturer on psychology, part-time, in the Department of Psychiatry at Cambridge Health Alliance, who also teaches courses on dreaming at HMS and in Harvard’s Freshman Seminar Program. Although the primary visual cortex handles basic image processing when we’re awake, the secondary visual cortex interprets and makes meaning of that data during all stages of sleep — and is especially active during hypnagogia and REM sleep.
In fact, hypnagogia, characterized by some scientists as covert REM, is increasingly considered to be a gateway to understanding and managing dreams themselves — which have historically been difficult to study.
“It’s very hard to put dreams on a microscope slide,” says Adam Haar Horowitz, a postdoctoral student at the MIT Media Lab who is also on the advisory board for the Center for Law, Brain, and Behavior at Massachusetts General Hospital. To attempt to better decipher dream activity, Horowitz, along with a team of engineers and scientists at the MIT Media Lab, developed a tool called Dormio. This glove-like device is designed to augment and influence hypnagogic hallucinations; it seems to help bring dreams into focus.
Horowitz and his primary advisor, Pattie Maes, a professor in MIT’s Program in Media Arts and Sciences, and his PhD thesis advisor, Robert Stickgold, an HMS professor of psychiatry at Beth Israel Deaconess Medical Center, are part of a new league of researchers who consider hypnagogia a means for finding clues to several basic science questions they’re tackling, such as how memories form and what parts of the brain generate visual imagery. Uncovering answers to such questions could lead to treatments that would provide a better quality of life for people who have sleep-related difficulties or disorders and are, as Horowitz puts it, “in need at night.”
Perhaps the most well-known study related to hypnagogia is one that Stickgold conducted in 2000. For the study, Stickgold and colleagues asked five people with amnesia and twelve novice players of the online puzzle game Tetris to play it for several hours over the course of three days. During the nights following long Tetris sessions, the researchers woke the players repeatedly during stage 1 sleep. Three-quarters of the novice players reported that as they drifted off to sleep, they saw images of falling and rotating Tetris pieces. Remarkably, the three people with amnesia said they saw images “like blocks” that were “turned on their side,” though they did not recall having seen similar falling blocks while awake. The researchers determined that the finding suggested that hypnagogic hallucinations do not require the activation of personal or experiential memory or of fact-based memory.
Cognitive constraints are loosened in hypnagogia, but not quite as much as in REM sleep. A smidge of ordinary logic remains. “You’re a different person as you enter sleep onset — you have shifts in the way the brain associates information,” Horowitz says, “but you retain elements of your waking self. You can watch these brain changes happen, watch these hypnagogic microdreams as if from a distance, and with practice, you can change elements of their content.”
Leveraging this characteristic, the Dormio tool plays recordings of people’s own voices to them as they fall asleep, with the aim of influencing the content of their hypnagogic hallucinations. After a handful of sleep sessions using the tool, Horowitz has found that people are often much more attuned to hypnagogic experiences and possibly able to manipulate them unaided.
The process is called targeted dream incubation; Horowitz hopes it might one day help veterans and others suffering from post-traumatic stress disorder and associated nightmare disorder. Horowitz, Stickgold, and research collaborators at the U.S. Veterans Affairs Finger Lakes Health Care System, the Université de Montréal, and MIT are investigating whether repeated use of the Dormio device instills a sense of agency and control over dream content, a phenomenon known as dream-related self-efficacy, in people with moderate nightmare disorder. Because studies involving veterans have shown that a perceived lack of control over dreams is correlated with higher insomnia symptoms, a boost in self-efficacy could be a boon to the overall mental health of those experiencing these difficulties.
Horowitz bases this hope in part on work by Michael Nadorff, an associate professor in the clinical psychology program at Mississippi State University. Nadorff researches the intersection of sleep disturbance and suicide risk. “From Nadorff’s work,” says Horowitz, “we learned that among many symptoms of psychological distress, nightmare frequency was the one factor that significantly differentiated between participants who had no suicide attempts and those who had made single and multiple attempts.”
Michelle Carr, a postdoctoral associate in the Department of Psychiatry at the University of Rochester, who has collaborated with Horowitz on several projects including the self-efficacy studies, thinks psychiatrists and others who study mental health should become part of a dream engineering movement. To that end, she organized the Dream x Engineering workshop at the MIT Media Lab in 2019.
Carr maintains that dream engineering that allows for lucid dreaming — that is, the state of being aware that you’re dreaming — could be another viable path toward healing.
“When you wake up from a lucid dream, you actually have a more positive mood in the morning,” she wrote in Aeon, a digital magazine of ideas, philosophy, and culture, in 2021. “This is in contrast to the distress that often comes with waking up from a nightmare.”
Clinical applications for hypnagogia are increasingly being suggested and explored. Barrett, for example, points out that hypnagogic hallucinations are often accompanied by sleep paralysis in people with narcolepsy, and because they are frequently jerked in and out of deep sleep, terrifying episodes of hypnagogia can occur for them during a time when their body is immobile. Insights into hypnagogic processes could lead to treatment protocols that might allow people with narcolepsy to better manage their condition.
On the more artistic end of the therapeutic spectrum, Horowitz describes a poet who is experiencing a visual disorder that prevents reading. The poet had already lost much of his ability to read when he turned to Horowitz as part of his learning to cope with his loss by working more purposefully with his dreams. This effort, according to Horowitz, also offers clinical relevance. “It’s a person trying to understand and work with the onset of disability, using dreams to make worlds that offer alternatives to the waking experience,” he says, and, as such, is “extremely meaningful” as an example of the possibilities of Dormio.
The Mind’s Eye
Renowned sleep researcher Rosalind Cartwright, who died in 2021 at the age of 98, coined the concept of the “24-hour mind” in her 2010 book of the same name. It’s an intriguing idea, this proposition that our identities are not just active and evolving while we’re awake but during slumber, too.
Researchers like Horowitz, Barrett, and Carr think that with more exposure to hypnagogic imagery, we might see ourselves in new ways and that, with increased comfort about the possibilities of hypnagogic imagery, society might become more receptive to dream sharing, or to interrogating mental health through the lens of the brain’s neurological nocturnes. Or at the very least, drawing attention to our hypnagogic personas may bring us newfound ideas that we can act on when we wake. For Barrett, who paints many of her dreams and hypnagogic hallucinations, hypnagogia has not only enriched her life — it’s defined her entire career.
“Things like the hypnagogic state are helpful, not just because they’re wiser than our waking thinking,” she says, “but because they’re different from it.”
Allison Eck is the executive communications manager in the HMS Office of Communications and External Relations.
Images: Maya Rucinski-Szwec (top gif); Deirdre Barrett (courtesy of Barrett); John Soares (Adam Horowitz)