Jon Sarkin was working as a chiropractor when he suffered a massive stroke. Afterwards, the 35-year-old became a volatile visual artist with a ferocious need to create, as his brain tried to make sense of the world at large.

"[My artwork is] a manifestation of what happened to me," Sarkin tells Fresh Air's Terry Gross. "I've learned how to visually represent my existential dilemma caused by my stroke."

Sarkin is the subject of Shadows Bright as Glass, a new book by science writer Amy Nutt. The book describes Sarkin's journey from happy-go-lucky doctor to manically-compulsive artist. It also raises larger questions about identity and what makes us each who we are.

"Is it memory? Is it emotion? Is it cognition? Is it personality?" asks Nutt. "I think all of those things play a part in Jon's story."

Sarkin's story began on a hot day in 1988, when he was out playing golf. He felt a throbbing, excruciating pain in his head and heard a ringing in his ears. After surgery, his brain began to swell and bleed. When Sarkin woke up, he was a completely different man.

"His heart stopped twice after his stroke so he has areas all over the brain that were deprived of oxygen," says Nutt. "The primary damage was to his left hemisphere and, in particular, to the left side of the cerebellum."

What research into the left side of the cerebellum has shown is that it carries our associations with sensory systems — that is, how we track movements in the world around us.

"Part of the deficit that Jon has is that his relationship with the environment and the world is literally fresh every moment," explains Nutt. "It's unfamiliar. He experiences the world almost as if it's new, every day. Objects around him, people and movement are experienced in a fresh way, and that is extraordinary for an artist."

Sarkin's art often features words and cross-hatches and images overlapping each other. His paintings, which have a cartoonish Robert Crumb-like quality, have been featured in The New Yorker and The New York Times and now hang in private galleries around the world.

"In essence, it's the continuing journey of who he is," says Nutt. "It's something that Jon has to keep doing. He literally has to keep doing art. It's what defines him and it's who he is."

And what makes Sarkin's case particularly unusual, says Nutt, is that he's able to reflect on who he was before his stroke.

"Jon is that rarest of individuals who was acutely aware and is acutely aware of what he lost and how he changed," she says. "I was fascinated by this aspect of someone knowing they are essentially two selves — a former self and a present self — and how that works."

Copyright NPR 2021.