Brain electric field sense of some types of fish. Each sensory system begins with specialized receptor cells, such as light-receptive neurons in the retina of the eye, or vibration-sensitive neurons in the cochlea of the ear. The axons of sensory receptor cells travel into the spinal cord or brain, where they transmit their signals to a first-order sensory nucleus dedicated to one specific sensory modality. This primary sensory nucleus sends information to higher-order sensory areas that are dedicated to the same modality. Eventually, via a way-station in the thalamus, the signals are sent to the cerebral cortex, where they are processed
Electrical brain stimulation physician Luigi Galvani (1737–1798) that nerves and muscles were electrically excitable. The stimulation of the surface of the cerebral cortex by using brain stimulation was used to investigate the motor cortex in animals by researchers such as Eduard Hitzig (1838–1907), Gustav Fritsch (1838–1927), David Ferrier (1842–1928) and Friedrich Goltz (1834–1902). The human cortex was also stimulated electrically by neurosurgeons and neurologists such as Robert Bartholow (1831–1904) and Fedor Krause (1857–1937). In the following century, the technique was improved by the invention of the stereotactic method by British neurosurgeon pioneer Victor Horsley (1857–1916), and by the development of chronic electrode implants