Nineteenth- and twentieth-century brain maps relating to locations and constructions of brain functions

This article is an outline of the transition in "brain maps" used to illustrate locations of cortical "centers" associated with movements, sensations, and language beginning with images from Gall and Spurzheim in the nineteenth century through those of functional magnetic resonance imaging in the twenty-first century. During the intervening years, new approaches required new brain maps to illustrate them, and brain maps helped to objectify and naturalize mental processes. One approach, electrical stimulation of the cerebral cortex-exemplified by Fritsch and Hitzig in 1870, Ferrier in 1873, and Penfield by 1937-required brain maps showing functional centers with expanded and overlapping boundaries. In another approach, brain maps that linked cortical centers to account for the complex syndromes of aphasia, apraxia, alexia, and agraphia were initially constructed by Baginsky in 1871, Wernicke in 1874, and Lichtheim in 1885, then later by Lissauer in 1890, Dejerine in 1892, and Liepmann in 1920, and eventually by Geschwind in 1965 and others through the late twentieth century. Over that intervening time, brain maps changed from illustrations of points on the cerebral cortex where movements and sensations were elicited to illustrations of areas (centers) associated with recognizable functions to illustrations of connections between those areas that account for complex symptoms occurring in clinical patients. By the end of this period, advancements in physics, mathematics, and cognitive science resulted in inventions that allowed brain maps of cortical locations derived from cognitive manipulations rather than from the usual electrical or ablative manipulations. "Mental" dependent variables became "cognitive" independent variables.