In the northeastern United States, a 28-year-old man sees features of his gray tabby cat, Luna, superimposed on human faces after a 2022 medical procedure, home.dartmouth.edu reported.
Karl experiences a rare form of palinopsia, a condition where visual elements persist or reappear long after the initial stimulus is gone. In his case, this phenomenon leads to prosopometamorphopsia, which causes severe distortions in how human faces appear.
The patient’s recurrent visual disturbances began two years ago. Surgeons removed a portion of his right temporal lobe to treat an arteriovenous malformation, a tangle of blood vessels carrying a high risk of brain bleeding. The right temporal lobe manages face processing in the human brain.
According to home.dartmouth.edu, Brad Duchaine—who serves as a professor of psychological and brain sciences and principal investigator of the Social Perception Lab at Dartmouth—noted that Karl observing his cat’s traits in people’s faces and vice versa highlights how memory components can be retrieved to shape ongoing perception.
To understand the distortions, researchers used modern technology to map what Karl experiences daily. Duchaine created a line-drawn sketch and fed it into a large language model to generate photorealistic depictions, according to home.dartmouth.edu.
Karl collaborated directly with the research team to modify the digital images. They published these findings in the journal Cortex.
“AI provides researchers like us with the ability to generate more accurate visualizations of what people are experiencing when they’re having distorted visual perceptions,” Duchaine told home.dartmouth.edu.
“If you know what the person is experiencing, you can much better research what they’re dealing with and try to figure out ways to control it. And now the patient can also take part in that process of creating those visualizations,” Duchaine added.
When investigating Karl’s symptoms, researchers noted historical parallels in neurological literature. Duchaine recalled a 1986 study published in Cortex detailing a woman who saw a passenger’s poodle and subsequently observed the dog’s face on everyone else riding the bus. That patient had suffered a stroke nine months prior.
However, Karl’s condition differs because only specific components of faces transfer between perceptions rather than an entire animal face. Duchaine’s lab studies prosopometamorphopsia extensively and has connected with more than 250 individuals experiencing similar facial distortions.
Many affected individuals receive incorrect psychiatric diagnoses. Some patients report being prescribed antipsychotic medications when they actually suffer from underlying visual processing problems, according to home.dartmouth.edu.
The Dartmouth research team plans to continue working closely with Karl. Additional contributions to the study came from Jennifer Nosker, a neuropsychologist at Brigham and Women’s Hospital, alongside Antônio Mello, Guarini, who is a PhD student in the Department of Psychological and Brain Sciences.
“The use of AI is also helpful for patients who want to convey not just to their healthcare professionals, but to their friends and family, what faces look like to them,” Duchaine told home.dartmouth.edu.
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