What 4,000 years of hallucinations have taught us about our brain

Over the past 40 years, many of my students have shared their personal experiences with hallucinogenic drugs. They are typically more fascinated, than frightened, by the experience. About 60 years ago the scientist C.H.W. Horne commented that “It is remarkable that one characteristic which seems to separate man from the allegedly lower animals is a recurring desire to escape from reality.” He was referring to the widespread use of hallucinogens by young people during the middle of the last century. What is even more remarkable, in my opinion, is how long humans have been documenting their use of hallucinogens. Cultures and religious rituals have been developing around the use of hallucinogens probably for as long as humans have been consuming the plants, fungi, and animals that evolved around them.

Imagine that the year is 2000 BCE and you are wandering around a region of the world that would one day be known as Central and South America. You are foraging for something safe to eat and come across a small yellowish mushroom that would one day be called Psilocybe Mexicana. We now realize that this mushroom contains the hallucinogen psilocybin. Indeed, psilocybin is present in about 75 different species of mushrooms, so there was a good chance that someone, one day, would stumble onto a mushroom containing it.

Eating this mushroom produced a stomachache that lasted for about thirty minutes and then something truly mystical occurred. You saw things that you had never seen before, images that could only be due to the intervention of a god (or goddess, depending upon your local traditions). You began sharing your collection of mushrooms with others and everyone marveled at the amazing mystical visual experiences. We now know that ultimately, the use of psilocybin-containing mushrooms became an integral part of common religious practice. The mushroom was revered and given the name Teonanacatl, which means “god’s flesh” or “sacred mushroom.” Using this sacred mushroom became an important milestone in the religious path to the spirit world. Mushroom art, sculptures, and images on stones have been discovered throughout the American Southwest, Central America, and South America. They clearly indicate the important role played by this mushroom in the local religions. When Francisco Hernandez invaded these regions in the 1570s he documented the use of these mushrooms and ultimately added them to his own list of medicinal herbs.

The stone carvings provide some insight into the effects that the mushrooms produced in the minds of these primitive peoples. You can imagine the challenge facing someone 4,000 years ago who wished to represent to others what they experienced while visiting their mushroom-inspired spirit world. What if your only tools for representing this experience were stones and bones? Even today, people find it difficult to describe their personal experiences with hallucinogens. It is interesting to consider whether hallucinogens produced qualitatively different experiences in people living 4,000 years ago as compared to people alive today. In 1928, the scientist Heinrich Kluver interviewed people who had used hallucinogenic mushrooms or other naturally occurring hallucinogens. He discovered that these drugs produce a surprisingly similar consensus of seeing geometric images accompanied by altered feelings. Though colors varied, participants consistently reported brightness intensification. Moreover, the apparent size, geometrical shapes, and symmetry were strikingly similar from person to person.

More recently, a study asked a similar question of 500 participants who reported using LSD or mescaline. Once again, these subjects reported seeing vivid swirling colors, sounds that seem to be associated with specific colors, and an intensification of visual perception. Images tended to pulsate and move toward a center tunnel or away from a bright center.

What neuroscientists have discovered by examining ancient artwork and by interviewing people today who use LSD, psilocybin, mescaline, ibogaine, and a host of other hallucinogens is that the basic visual experience has been highly consistent across the last four millennia. The findings reveal a great deal about how our brain responds to these types of drugs. Overall, under a very diverse set of conditions the human visual system responds with a limited number of form constants. The four consistent geometric images reported following use of these drugs include: (1) a latticework, grating, or honeycomb; (2) a cobweb structure; (3) a tunnel or funnel alley; or (4) a spiral image. Our ancestors included all of these designs in their wall carvings.

The fact these visual images are so consistent across time suggest that the human brain has not changed in the past 4,000 years. The architecture and wiring of the visual cortex were the same 4,000 years ago as it is today. The geometric nature of the hallucinations is due to the pattern of neural connections within the visual cortex. Anyone who has seen a migraine aura has witnessed similar geometric shimmering patterns. Taken together, we can conclude that these hallucinogenic drugs uniformly and consistently produce abnormal activation of cortical neurons leading to spontaneous pattern formation within the visual cortex. Thus, hallucinogens alter how our neurons communicate with each other to process visual information in our brain; the result is something that is both familiar (such as an object of worship) and quite bizarre (such as a distortion of the object’s color or appearance).

These investigations teach us a lot about how our brain functions and provide insight into the nature of the religious world of our ancestors. How truly fantastic!

Featured Image Credit: Blurred Lines by Sebastian Muller. CC0 via Unsplash.