This article is taken from the monthly magazine Sciences et Avenir n°947, dated January 2026.
When Alois Alzheimer observed the plaques and degeneration in Auguste D.'s brain in 1906, he effectively signed the birth certificate of a disease that would bear his name. Four years later, for the first time, in a new edition of his seminal treatise on psychiatry, Emil Kraepelin shifted a disorder from psychiatry to neurology. The observation of a lesion justified separating this case from other forms of dementia. This shift was emblematic of the boundary that would long separate "brain" diseases from "mental" disorders. It also reflects the recurring tensions between neurology and psychiatry, a partnership that has always had a tumultuous relationship.
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