The brain regions we use to process faces are located primarily in our occipital and temporal lobes (back of the brain), and it is likely that abnormalities in these regions or the white matter connections between these regions cause PMO. In some cases, damage appears to be restricted to gray matter. Interestingly though, the cause of the majority of hemi-PMO cases is damage to white matter connections that link regions in the two hemispheres. These connections make up part of the corpus callosum and, in particular, the splenium. Below is an image showing the small splenium lesion that caused the hemi-PMO that Patient A.D. experiences (Almeida et al., 2020).
Other forms of metamorphopsia
Perceptual distortions can affect any aspect of our visual experience. In PMO, faces are specifically impacted, but distortions can also have specific effects on other visual categories (e.g., objects, bodies, etc.). If you’re experiencing distortions that affect a particular visual category, we’d be interested in hearing about the distortions you’re seeing.
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If you are experiencing face distortions or similar symptoms, please fill out this form to contact us. We are based in the Department of Psychological and Brain Science at Dartmouth College.