Most readers know writer, journalist and Harvard professor Michael Pollan for his work on the food industry. His book The Omnivore’s Dilemma follows the different ways humans have obtained food through history, and the current tension between agribusiness and the natural environment. He even published a manual on “food rules,” suggesting humans, “Eat food. Not too much. Mostly plants.”

But that wasn’t what Mr. Pollan and writer Tony Horwitz discussed at the Chilmark Community Center on Sunday night as part of the summer Author Series.

“Having written a lot about food, Michael has moved on to a different kind of edible,” Mr. Horwitz told the packed audience. “Psychedelics.”

In an often-humorous interview between Mr. Pollan and his longtime friend, Mr. Horwitz, the author answered questions and shared stories from his new book, How To Change Your Mind, What the New Science of Psychedelics Teaches Us About Consciousness, Dying, Addiction, Depression, and Transcendence.

Part history, part philosophy and part self-discovery, the book centers around the science behind psychedelics, particularly LSD, DMT and psilocybin, known familiarly as “magic mushrooms.” The germ for Mr. Pollan’s book came from a New Yorker article he wrote in 2015 called The Trip Treatment.

Longtime seasonal Aquinnah resident, Mr. Pollan talked about what he called his most personal book yet. — Mark Alan Lovewell

“There’s this Renaissance of research into psychedelics that is picking up where scientists from the 50s and 60s left off,” Mr. Pollan said. “They’re redoing a lot of those trials and it’s yielding some really interesting findings about the self and consciousness.”

Whereas much of the research from the mid-20th century relied on anecdotal evidence and the enthusiasm of a few militant proponents of the drugs, such as Henry and Clare Luce, Cary Grant, Ken Kesey and Timothy Leary, modern brain-imaging technology has allowed scientists to map and monitor the neural impulses of psychedelic users. The research has shown the drugs’ potential therapeutic benefits, including helping with depression and addiction.

“They expected to find an explosion in the brain, but in fact they found the opposite,” Mr. Pollan said. “They found that a very important network of the brain was muffled.”

That network was the Default Mode Network, which connects the cortex to deeper centers of memory, emotion and sense of self. A researcher at Yale examined the brains of people who had meditated for over 10,000 hours and their imaging looked identical to the brains of people on psychedelics.

“It’s a very important part of the brain but also a part of the brain that can torture us,” Mr. Pollan said. He argued that temporarily taking the DMN offline appears to be what’s responsible for the drugs’ therapeutic benefits. When researching for the book, Mr. Pollan called scientists at the National Institute of Health looking for a quotation expressing skepticism or fears about the discoveries.

“I couldn’t find it,” he said.

Unlike Mr. Horwitz, who jokingly told of his youthful escapades at Lucy Vincent Beach, Mr. Pollan had never experimented with the drugs before writing his book. But he knew he couldn’t write about psychedelics having never tried them himself.

“Talking to people who described their experiences, I was intensely curious but I was also a little jealous,” Mr. Pollan said. “I had never had a spiritual experience like that.”

Rather than taking the drugs in his house or while in nature, Mr. Pollan underwent what he called “guided trips” during which experts provide music, sleep masks, and wrote down the subject’s verbal utterances. Mr. Pollan’s most transcendental moment came during a high-dosage psilocybin trip.

“I saw myself as a bunch of exploding Post-It notes,” he said. “It was the complete dissolution of ego. And my ultimate discovery was that if your ego disappears, you can survive. I became more open, and redefined what spirituality was for myself.”

Some trips were worse than others. Mr. Pollan told the story of smoking a high-potency drug extracted from the venom of the Sonoran Desert Toad.

“You take one puff of this and you feel like you are on a rocket ship to the other end of the universe,” Mr. Pollan said. “It was horrible. I will never smoke the toad again.”

Mr. Pollan did say that were psychedelics legal, he would do them every year on his birthday as a form of self-reflection. Until then, Mr. Pollan has decided that he’s taken his last trip.

“I don’t know what I’m going to do next,” he said. “I got the feeling writing this book that anything else I do would be smaller, in some way.”

The most aggressive pushback against the book has come from people who believe that consciousness is a cosmic property, and not a function of the brain.

“The idea that the brain produces consciousness is a hypothesis. A parsimonious one, but a hypothesis,” Mr. Pollan said. “Maybe I’ll look at that.”