From early arguments between Galvani and Volta in the late 1700s, to later experiments by Helmholtz in the mid-1800s, the scientific examination of the electrical excitability of biological tissues has a rich history (Galvani, 1791; Volta, 1800; Helmholtz, 1842; Hess, 1994), particularly regarding the use of electrical stimulation to induce focused cortical activation, which enabled the discovery of motor maps in different locations of the cortex. This tradition started in the late 19th century when German neuroscientists Fritsch and Hitzig used electrical stimulation in animals to generate crude motor cortex maps, demonstrating contralateral activation of muscles for the first time (Fritsch and Hitzig, 1870). Sir Charles Sherrington, one of the founders of modern neuroscience, later used more focused stimulation to form early maps of ape motor cortex (Brown and Sherrington, 1911). In the 1930s, Wilder Penfield, one of Sherrington’s students extended this work to human motor cortex, as he showed the existence of a spatial map of muscles in the body (Penfield and Boldrey, 1937). His rigorous examination demonstrated that the size of a body part’s cortical representation is proportional to the fine nature of that body part’s movements. Penfield’s work helped popularize the technique of electrical stimulation as a useful tool for extending understanding of the brain (Penfield and Rasmussen, 1950).
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