Who Actually Read Exner? Returning to the Source of the Frontal "Writing Centre" Hypothesis
Résumé
We have translated the most famous text of Sigmund Exner (1846-1926), the one relating to the existence of a localised "writing centre" in the brain. We discuss its relevance to the modern study and understanding of writing and agraphia. In Exner's most famous text, he hypothesised about the eponymous "Exner's Area", a discrete area within the brain that was located in the left middle frontal gyrus, which was dedicated to the function of writing. This text in German, included in a book published in 1881 "Untersuchungen über die Lokalisation der Functionen in der Grosshirnrinde des Menschen" (Studies on the localization of functions in the cerebral cortex of humans), lent itself to passionate debates during the following decades on the possibility of finding a specific writing centre in left middle frontal gyrus. Modern authors still refer back to the evidence cited in this seminal text. However, over the 281 pages of Exner's book, only a few chapters dealt with agraphia. Only four of the 167 case reports in the book explicitly mention agraphia. Although Exner describes the anatomical details of these lesions (from autopsies), none of them had pure agraphia, and only one case had an isolated lesion of the posterior part of the middle frontal gyrus. The small number of patients, the absence of pure agraphia symptoms, and the variation in the anatomy of these lesions are the main reasons why Exner's hypothesis of a writing centre in left middle frontal gyrus has been continually debated until now. More than the seminal publication of Sigmund Exner on agraphia, the diffusion of his theory was partly due to the influence that Exner and his family had within the scientific community at the turn of the 20th century.