Jean Lhermitte (1877-1959) was born in Mont-Saint-Père, Aisne, son of Léon Augustin Lhermitte, a French realist painter. Following his early education at Saint-Etienne, he studied in Paris and graduated in medicine in 1907. He specialised in neurology and became Chef-de-clinique (resident) for nervous diseases in 1908, Chef de laboratoire in 1910, and professeur agrégé for psychiatry 1922. He later became Médecin des Hôpitaux at the “Hospice Paul Brousse”, head of the foundation “Dejerine”, and clinical director at the Salpêtrière Hospital. During World War I, Lhermitte studied spinal injuries and became interested in neuropsychiatry. This led to publications on visual hallucinations of the self. A deeply religious man, he explored the common territory between theology and medicine, and this led him to interesting studies on demonic possession and stigmatisation.

He was one of the pioneers of behavioral neurology, including the field of hallucinations. This article focuses on his work concerning the relationship between hallucinations, sleep, and dreams. From 1910, Lhermitte became interested in sleep and its disorders, particularly narcolepsy and its accompanying symptoms. He also reported on sleep disorders and hallucinations occurring in people with lesions of the diencephalic region (“infundibular syndrome”), and later encephalitis lethargica. In 1922, he described a syndrome of complex, predominantly visual hallucinations in patients with vascular damage to the midbrain, known as peduncular hallucinosis.