an unusual aspect of brain chemistry

Its producer, Riviera Farms in the state of Victoria, said it believed its product had been “contaminated with a weed.”

What weed could make spinach hallucinogenic? The health department of the state of Victoria has said that the symptoms suggested “anticholinergic syndrome,” a type of poisoning mainly caused by plants in the Solanaceae family, which includes nightshade, jimson weed and mandrake root.

Anticholinergic plants and drugs inhibit the action of a brain chemical called acetylcholine, which is linked to memory, thinking and the visual system, according to Dominic ffytche, a professor of visual psychiatry at King’s College London, who specializes in visual hallucinations (and who really does lowercase his last name). Acetylcholine can also be lost naturally and is linked to Alzheimer’s, some type of dementias and other neurodegenerative diseases, he said.

Hallucinations caused by a suppression or loss of acetylcholine tend to be “formed,” Professor ffytche said, that is concrete and recognizable, usually taking the form of people, objects and landscapes. This is distinct from “unformed” hallucinations, when people might see shapes, patterns and colors.

Furthermore, hallucinations caused by a lack of acetylcholine are linked to the memory system, so they tend to involve people the sufferer knows or recognizes, he said. “It could be deceased relatives, or people that are vaguely familiar to them in some way.”

Those experiencing more extreme symptoms can have difficulty determining what is real, he said.

“When you lose an understanding that they are hallucinations, they tend to become distressing,” he added. “You become sucked into the story where something bad is going on and people are trying to hurt you or harm you in some way.”

https://www.nytimes.com/2022/12/18/world/australia/spinach-hallucinations.html