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One hundred and 50 years ago, a book entitled Mécanisme de la Physionomie Humaine appeared.1 Initially receiving muted and mixed receptions in both the scientific and artistic press, this work has subsequently been recognised as a groundbreaking treatise which was to have a profound influence on the study of facial expression. It was published in 1862 as a single volume, although it had originally comprised two parts: the Partie Scientifique, which was accompanied by 74 photographs, and the short Partie Esthétique, accompanied by 10 photographs, which followed a few months later.2 A second edition appeared posthumously in 1876, but it was only translated into English in 1990 as The Mechanism of Human Facial Expression.3
The present contribution focuses on a debate which began in the Mécanisme but continues to this day, and concerns facial anatomy and expression. The debate centres on the controversial function of a small eyebrow muscle, the corrugator supercilii, yet the background to the debate originated in Greece 2000 years ago, and illustrates how neuroscience can sometimes be informed by the arts.
Duchenne and his neurophysiological studies on facial expression
The author of the Mécanisme, the ‘eccentric, provincial physician’ Guillaume Benjamin Amand Duchenne (de Boulogne) (1806–1875),4 was destined to become the illustrious French neurologist, and friend and immensely influential colleague and mentor of Charcot at la Salpêtrière in Paris. Among his other contributions to neurology, Duchenne had introduced the technique of ‘électrisation localisée’, localised faradisation. This technique enabled him to study nearly all the muscles in man,5 and from about 1850, when Duchenne first became particularly interested in the neural mechanisms subserving human facial expression, he applied this surface electrical stimulation to individual facial muscles and branches of the facial nerve. Harnessing another novel technique, photography, Duchenne could then capture and produce permanent records of the fleeting facial expressions he …