La Peyronie and the experimental search for the seat of the soul: neuropsychological methodology in the eighteenth century.

The birth of scientific neuropsychology is traditionally considered to have taken place during the 19th century when disturbances or losses of specific mental functions were systematically correlated with post-mortem findings of localized cerebral pathology. Attempts at localizing psychic functions were of course made earlier, but they were usually not based on scientific observations with one notable and so far neglected exception. At the beginning of the 18th century the French surgeon François Gigot de La Peyronie systematically tried to correlate deficits of mental functions with autopsy findings. The methodological principles he formulated were sound and do not essentially differ from those used in modern scientific neuropsychology. His method was based on the systematic exclusion of those areas of the brain whose lesions are not associated with disruption of the faculties of the soul combined with the careful examination of cases where such association consistently exists. His conclusions were, however, disappointing from the modern point of view and he obviously failed to found a new scientific discipline. The reasons for this failure obviously lay in the dualistic presuppositions which made him look for the unique locus of mind-body interaction instead of localizing specific functions.