By Siri Hustvedt, from a keynote lecture delivered in Paris at this year’s winter meeting of the Société de Neurophysiologie, to be published in a special issue of Clinical Neurophysiology, “Conversion Syndrome and Its Boundaries.” Hustvedt is the author of several works of fiction and non-fiction. The Blazing World, a novel, will be published in March by Simon & Schuster.

In the mid-1980s Gretchen Van Boemel, director of clinical electrophysiology at the Doheny Eye Institute at the University of Southern California, began seeing dozens of patients complaining of blindness or severely compromised vision. A number of them had already…