Swedenborg and localization theory

Abstract

Present-day concepts of cerebral, localized, motor areas commenced with a set of stimulation experiments with anaesthetised dogs done by two German physicians, Fritsch and Hitzig (1870). Applying weak electrical pulses to exposed cerebral cortex, they were able to evoke muscular contractions in the opposite body half. They varied stimulation intensity, and established its lowest effective magnitude, or threshold strength. This stimulation intensity was selected in order to avoid activation of deep structures, and they could see how muscle groups on different parts of the contralateral body half were activated from different spots on the cortical surface. Similar effects were obtained from roughly the same locations in different animals. Forelimb and facial muscles were activated from spots located lateral to those of hindlimb muscles. In their paper's introductory survey of earlier and contemporary publications, the two authors made it clear that the findings were contrary to established opinion. Neither the possibility of cortical activation, nor cortical localization of function were definitely known to exist, although sometimes surmised. The findings were not accepted immediately, but started a great number of tests internationally, and in short time engendered an atmosphere of electric excitement, to paraphrase Young (1970).