Extremely Rare Condition Caused Patient to See Faces as Half Melted

An extremely rare condition, known as hemi-prosopometamorphopsia (or hemi-PMO) caused a man “to suffer from a bizarre and highly distressing symptom that makes faces appear half melted” IFLScience.com reports. This condition has only been recorded 25 times in medical history and is caused by some form of brain damage. In this instance, the patient had a lesion in the splenium region of his brain, an area associated with sight.

The patient, nicknamed “A.D.” by the researchers of a recent case study published in the journal Current Biology, first presented with this symptom five years ago. This specific study involved two experiments. In the first, A.D. was presented with images of human faces and non-face images and asked to report on distortions. For 17 of the 20 faces, A.D. saw distortions on the right side of the face, with the facial features usually appearing drooped. Two of the images of faces that did not elicit a distortion showed profile views in which the right side of the face was not visible. A.D. reported no distortion of the non-face images. In the second study, A.D. was asked to report on distortions that he saw in 15 different faces that were presented in a variety of ways (at different in-depth and plane rotations). Regardless of how the faces were presented, A.D. still saw the facial features distorted on the right side of the face. 

“The consistency of the location of A.D.’s distortion demonstrates that faces, regardless of viewpoint or orientation, are aligned to the same template similar to what computer face recognition systems do. In A.D.’s case, the output from that process is disrupted as it is passed from one brain hemisphere to the other due to his splenium lesion,” a release from Dartmouth concludes.