Historical contributions to the modern understanding of function in the central area

OBJECTIVE: To review the historical developments leading to the modern understanding of central area physiological features. METHODS: Important scientific writings related to stimulation and function of the central area were studied, beginning with the first electrolytic battery description. RESULTS: Volta's description of the electrolytic battery provided a reliable tool for mapping cortical function. However, 70 years elapsed before Fritsch and Hitzig convincingly demonstrated an excitable cortex and challenged Flourens' theories of cerebral function. The localization of sensory and motor cortical representations was hampered by difficulties in interpreting responses to stimulation in animals and in relating animal data to the human brain. Nevertheless, by the beginning of the 20th century, the evidence for a separate sensory and motor gyrus within the central area was overwhelming. Pioneering surgeons such as Keen, Krause, Foerster, Frazier, and Cushing demonstrated the motor and sensory areas in human subjects during the course of surgery. CONCLUSION: The interpretation of central area function has evolved from the 19th century view that diffuse areas of the cortex and the limbic system serve motor and sensory functions to the theories of Grunbaum, Sherrington, Campbell, and others at the beginning of the 20th century, who suggested segregated functional regions defined by sulcal and architectonic anatomic features. Subsequently, Penfield and Rasmussen supported the idea of a sensorimotor area in which central area function is not strictly separated by the central sulcus. Modern research using microelectrode recordings and functional imaging indicates localized primary sensory and motor functions defined by architectonic anatomic features.