After brain surgery, man sees cat's eyes in human faces

Researchers at Dartmouth College and Brigham and Women’s Hospital detailed the case of a 28-year-old man identified as Karl, who lives in the northeastern United States and owns a gray tabby cat named Luna. Two years ago, Karl underwent surgery to remove part of his right temporal lobe due to an arteriovenous malformation, an abnormal tangle of veins and arteries that carries a risk of brain bleeds. Following the operation, Karl developed palinopsia and a form of prosopometamorphopsia, also known as PMO. Because Luna is often the first face Karl sees in the morning, her almond-shaped eyes, enlarged pupils, and stripes frequently appear on human faces he encounters either in person or online later that day, according to Medical Xpress and a Dartmouth College press release reported by New Atlas. Alternatively, if Karl sees a human face first in the day, those features can be transferred onto other people or even back to his cat. Gizmodo reported that Karl can also swap parts of two people's faces. These episodes typically last for several hours and can sometimes persist for an entire day.

Lead author Brad Duchaine, a professor and chair of psychological and brain sciences and principal investigator of the Social Perception Lab at Dartmouth, explained that the right temporal lobe plays a crucial role in facial processing. "This case of Karl seeing his cat's features in human faces and vice versa demonstrates that individual features can be pulled from memory and influence our ongoing perception," Duchaine stated according to Medical Xpress. Duchaine added, "Our brains break faces into components and match them against features stored in memory. Karl's percepts are what happens when that matching goes wrong and a stored feature gets stuck in the face perception system." Medical Xpress noted that Jennifer Nosker, a neuropsychologist at Brigham and Women's Hospital, and Antônio Mello, a Ph.D. student in the Department of Psychological and Brain Sciences, also contributed to the study.

Karl's condition reminded researchers of a similar case reported 40 years earlier in the journal Cortex. In that 1986 study, a 58-year-old woman who had experienced a stroke saw a poodle's face on fellow passengers riding a bus. Karl's case was published last month in the exact same journal, Cortex. Duchaine and Karl then collaborated to modify the images so they accurately matched what Karl had seen. Duchaine noted that this AI approach allows researchers to generate more accurate visualizations of distorted visual perceptions and helps patients communicate their experiences to friends, family, and healthcare professionals. Duchaine's lab has documented about 250 people experiencing face distortions and noted that some individuals have been incorrectly diagnosed with psychiatric problems or given antipsychotics when experiencing visual problems. The research team plans to continue working with Karl in the future.