Imagine that everyone you see looks like a Picasso portrait. This is the case of this 59-year-old man, suffering from a rare disorder: hemi-prosopometamorphopsia.
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The story begins like a horror film: one day, a 59-year-old man suddenly notices that on television, all faces appear distorted on the right side. He then looks at himself in a mirrormirror and notices with amazement that his own face shows the same distortion: the eye, the nose and the corner of the mouth on the right seem to “hang” as if they were melting. Even stranger: this distortion only concerns faces seen from the front, and remains present even when the face is shown upside down (the distortion then appearing on the left). No other part of the body or any object is subject to any deformation.
This rare condition, called hemi-prosopometamorphopsia (prosopo means “face”), is linked to a lesion in the splenium, the posterior part of the corpus callosum which contains a very large number of fibers connecting the two hemispheres of the brain. Gold, ” every time we see a face, the brain adjusts our representation of that face so that its size, point of view and orientation match those stored in its memory, just like facial recognition systems by computercomputer such as those used by FacebookFacebook And GoogleGoogle », explains Brad Duchaine, professor of psychological and brain sciences at Dartmouth College and co-author of the case study, published in the journal Current Biology. While ” databasedatabase » is intact, which allows the patient to realize that the face is abnormal, the brain is no longer able to match the face with those already recorded.
Faces that turn into monsters
Prosopometamorphopsia can take various forms. A patient whose case is described in the journal Neurology thus recounts seeing the distorted faces “ like those of a monster “, with the left eye extended towards the ear, while the nose seems to be bent towards the left cheek and the mouth towards the chin. Another patient describes a swollen left eyelid. as if she had botched cosmetic surgery “.
In 2014, The Lancet reported the case of a 52-year-old woman suffering from visual hallucinations who saw faces transform into dragons. “ After several minutes, the faces turn black, with long, pointed ears and protruding snouts, reptiloid skin, and huge bright yellow, green, blue, or red eyes. », described the authors. In this case, doctors attributed the disorder to abnormal electrophysiological activity in adjacent regions of the brain specialized in the perception of faces and colorcolor. A StrokeStrokea heart attack, a brain tumor or evenepilepsyepilepsymigraine or illnesses eyepieceseyepieces are also likely to cause illness.
Neglect dyslexia
If prosopometamorphopsia only responds to facial stimuli, other diseases involve different stimuli. Some cases of dyslexiadyslexia by neglect concern, for example, frames of reference centered on words and text processing. Patients “forget” or substitute parts of a word (usually the beginning or end), whether it is written horizontally, vertically, or obliquely.
