Imagine looking in the mirror and seeing half of your face look like it’s melting away. While this may seem like a scene out of a horror movie, it was the reality for a 59-year-old man nicknamed A.D.
According to the case study, published in the journal Current Biology, the 59-year old was suffering from a rare condition called Hemi-prosopometamorphopsia or, in simpler terms Hemi-PMO.
How did it all start?
Around 6 years ago, while watching television, A.D. noticed all the faces on the screen seemed distorted on one side. When he looked in the mirror, he saw his own face distorted in a similar manner. He reported that features on the right side (from A.D.’s perspective) looked as if they were melting. This affected his life to such an extent that he found it unpleasant to look at faces.
Surprisingly, he did not report these distortions in other parts of the body or in any other object. He had no vision problems or any cognitive impairment. He also had no trouble recognizing faces.
What Caused the Distorted Faces?
Hemi-PMO is a rare and bizarre medical condition with only 25 cases reported in the medical literature. A left splenic lesion seemed to have caused the condition in A.D. The splenium is the posterior portion of the Corpus Callosum.
In Hemi-PMO, patients tend to perceive one half of the face as distorted with features appearing drooping, out of proportion, or swollen. Most cases of Hemi-PMO do not last long and tend to fade out. However, in A.D,’s case, it has persisted for over six years.
What Did the Experiments Reveal?
In the hopes to better study his condition, researchers conducted two experiments on the patient. In the first experiment, A.D. was shown 20 face-images and 20 non-face images such as cars, houses, and other objects. The faces ranged from full left profile to full right profile.
In the second experiment, A.D. was shown 15 frontal views of faces at different planes and orientations.
A.D. did not report any distortion in non-face images. However, in the face-images, he reported seeing a distorted face on the right side in all planes and angles. Even when the faces were shown upside down, the right side continued to look the most distorted.
Almeida et al., Face-Specific Perceptual Distortions Reveal A View- and Orientation-Independent Face Template, Current Biology (2020), https://doi.org/10.1016/j.cub.2020.07.067