A man tries out a virtual reality game inside a Fulldome.pro 360-degree projection dome on opening day of the Electronic Entertainment Expo at the Los Angeles Convention Center on June 13th, 2017. (Photo: David McNew/Getty Images)

For nearly two decades, the Tribeca Film Festival has premiered films by new directors, independent releases from established stars, powerhouse documentaries, and buzzy foreign films. But this year it offered attendees an exhibit a little more befitting of Burning Man than Sundance: an ayahuasca trip.

The festival's virtual reality wing included a VR experience designed to feel like a psychedelic adventure in the Amazon. Virtual psychonauts were invited to ascend upstairs from the VR showroom to a darkened, faux ivy-walled room in Midtown Manhattan, where their VR goggles transported them somewhere in the Amazon, the Cut reports. There, a shaman-like figure guided users into an ayahuasca-drinking ceremony that spiraled into a visions of horrible creatures, beautiful stained-glass cathedrals, and surreally kaleidoscoping geometry. (So much for being transported out of Midtown!) When Leanna Standish, a researcher at the University of Washington School of Medicine, estimated in 2016 that, "on any given night in Manhattan, there are a hundred ayahuasca 'circles' going on," presumably this wasn't exactly what she meant.

Ayahuasca—and its main psychoactive ingredient, DMT (dimethyltryptamine)—is part of a class of hallucinogenic drugs known as psychedelics that also includes LSD and psilocybin mushrooms. These drugs can cause unusual sensory perceptions, hallucinations, and changes in cognition sometimes referred to as "altered states of consciousness."

There's a long history of connection between psychedelic drugs and VR: Mark Pesce, one of the co-creators of Virtual Reality Modeling Language, claims to have come up with the idea for it during an acid trip's "moment of clarity." Like psychedelic drugs, virtual reality allows for a non-passive, three-dimensional experience of immersion in a world that's not quite the same as our usual unaltered reality. Advocates, enthusiasts, and some researchers see both as potentially able to help treat a panoply of mental illnesses—and both occasionally induce projectile vomiting. But do the similarities end there, or can VR technology actually mimic a psychedelic trip and replace drugs in the future?

Virtual reality is an "emotionally evocative technology," says Skip Rizzo, director for medical virtual reality at the University of Southern California's Institute for Creative Technologies, "because we can create these simulated worlds that fool some of the brain, but not the whole brain."

The emotional response provoked by virtual reality experiences is often very similar to what would occur in the corresponding real-world situation, if turned down a notch or two. Walks along virtually simulated steep cliffs or high-strung tightropes often bring elevated heart rates and moistened palms. The amygdala—a core structure of the limbic system that governs the body's emotionally driven fight-or-flight response—mostly reacts as if the visual stimuli are real, but the conscious perception of the frontal lobes knows that what's being experienced is simulated. "It actually has an impact on the brain, which reacts to it as if it's a real thing," Rizzo says, "even though your frontal lobes are saying, 'OK, I'm safe, this is no threat.'"

This real-but-slightly diminished emotional reaction makes VR technology particularly useful for exposure therapy with patients suffering from post-traumatic stress disorder and other anxiety disorders, allowing them to confront their fears in a controlled way. For example, a patient who is too scared of heights to get in an elevator may be able to ease into one made of virtual glass. A doctor can take a combat veteran through a guided tour to revisit their traumas.

Still, the frontal lobe likely has some control over the amygdala's response, according to Manoj Doss, a neuropsychopharmacologist who studies the effects of hallucinogens on the brain at the John Hopkins Psychedelic Research Unit. This is likely why the emotional responses precipitated by virtual experiences are usually somewhat less intense than in situations believed to be real. The memory-centric hippocampus might also play a role in suppressing the amygdala's full emotional response, Doss says.

Scientists don't yet have a great understanding of exactly what is going on in the brain when someone is tripping on a hallucinogenic drug like ayahuasca or LSD—"I don't think anybody does!" Doss says. This is partially because psychedelic neuroscience is a relatively young research field: The first brain imaging of people on psychedelics only began in the 1990s. It's also because most studies have focused on brain scans without behavioral data, a standard that Doss attributes to some leading psychedelic researchers' lack of experimental psychology background, the overwhelming data involved in brain research, and the cost of behavioral studies.

Still, he says, there are a handful of leading theories about what happens during a trip. Many of the hypotheses involve the drugs binding to the brain's serotonin 2A receptors, which makes the corresponding neurons more likely to fire, as if they were flooded with serotonin. One more specific theory involves the drugs' possible effects on the claustrum, a tiny, Serotonin 2A receptor-dense sliver of the cortex that's connected to much of the brain, and which the DNA double-helix-discovering Francis Crick believed to be "the conductor of consciousness."

Another leading theory involves the thalamus, which plays a role in filtering out information that isn't relevant to the brain's current focus of attention. Doss describes its function as facilitating the so-called "cocktail party effect," the brain's ability to focus on a single conversation in a noisy room. "When you're on these drugs, some of that less salient information starts to creep in, making you maybe more distractible," Doss says. "And so one idea is that maybe this filtering is being blunted."

Other popular theories involve ideas about "brain entropy": that psychedelic drugs cause the brain to cycle through a larger number of diverse brain states—patterns of coordinated neural activity—than it would while sober.

And while trip participants often describe divergent effects from different hallucinogens like ayahuasca and mushrooms, currently, brain scientists can mostly only talk definitively about their similarities. "There are probably some differences, but at the moment, we don't really have the resolution. All the studies that have been done looking at these drugs are like 15 subjects," Doss says.

But, insofar as these theories and similarities are understood, can VR realistically recreate a trip? "I hate to say it, and I might sound like an old fart here. But I just don't see it being capable of inducing that [emotional] state to that level that you can get with a big time acid trip," Rizzo says.

The visual and auditory elements of a psychedelic trip are absolutely possible to virtually recreate, according to Jim Blascovich, professor emeritus at the University of California–Santa Barbara, where he directed the Research Center for Virtual Environments and Behavior, but current VR technology is not good at affecting other sensory inputs, like touch. "Tactile stuff is really hard to create by machine and in so-called virtual worlds," he says.

Also difficult to recreate are the perceived cognitive impairments of a trip described by some of the leading theories. For example, if the brain's attention-filtering mechanism is altered by psychedelics, then even an exact recreation of the auditory and visual effects probably won't quite feel like a psychedelic trip. Same goes for entropic brain states and the memory effects of these drugs.

That said, it's not yet clear the extent to which some of the sensory effects of the drugs cause users to trip and how much the experience of tripping causes the sensory effects. "It's a dynamic system; it's difficult to fully disentangle all these things," Doss says, pointing to research documenting the hallucinatory effects of sensory deprivation. This leaves open the possibility that trippy virtual visuals could induce a full-on trip. "There's a little bit of a chicken and egg type problem."

Yet another problem for the fidelity of virtual reality psychedelic trips is that most people, when tripping, don't experience full hallucinations of imagery with no connection to their surroundings (although this has been documented to occur when people trip while wearing eyeshades). Instead, visuals tend to be altered with psychedelic visual patterns. "And there hasn't been a proper perception researcher that's really studied these drugs. So we really don't know the actual patterns that people are experiencing when they have these drugs," Doss says. "Is there a predictable change there, do certain colors pop out more, or all the colors pop out more? We don't know. These are all things that, once better studied, could be used by VR researchers to better mimic certain aspects of the psychedelic experience."

Despite the current knowledge gap, artists like Alex Gray have been able to convey the visuals of a psychedelic trip in a way that many experienced trippers have found highly relatable. For now, though, virtual ayahuasca has apparently not progressed far beyond "the world's most elab­o­rate screensaver," as one participant put it.

Still, Doss suspects that the sensory alterations of a trip are probably personalized, or at least not completely consistent. His description of tripping's individualized nature reminded me of Rizzo's description of virtual reality: "The VR experience is really going to be keyed to the individual user. There are some universal things like fright and surprise that can rattle anybody's cage if you put some of those things in," Rizzo says. But beyond that, "we're getting into the realm of art. Is there a formula for a stimulus package that can affect the brain and really have it be like, 'Oh, man, that is far out?' It can happen, but that's art."