Localization (Brain Function)

Refers to the concept that different areas of the brain control different aspects of behavior.

Theories of localization first gained scientific credence in the 1860s with Paul Broca's discovery that damage to a specific part of the brain—the left frontal lobe—was associated with speech impairment. Other discoveries followed: in 1874, Carl Wernicke identified the part of the brain responsible for receptive speech (the upper rear part of the left temporal lobe, known as Wernicke's area), and in 1870 Gustav Fritsch and J. L. Hitzig found that stimulating different parts of the cerebral cortex produced movement in different areas of the body. By the beginning of the twentieth century, detailed maps were available showing the functions of the different areas of the brain.

Not all researchers have agreed with theories of localization, however. An influential conflicting view is the equipotential theory, which asserts that all areas of the brain are equally active in overall mental functioning. According to this theory, the effects of damage to the brain are determined by the extent rather than the location of the damage. Early exponents of this view—including Goldstein and Lashley—believed that basic motor and sensory functions are localized, but that higher mental functions are not. There is still controversy between adherents of the localization and equipotential theories of brain function. Some experts advocate a combination of the two theories, while others search for new alternatives, such as that proposed by J. Hughlings Jackson in 1973. Jackson claimed that the most basic skills were localized but that most complex mental functions combined these so extensively that the whole brain was actually involved in most types of behavior.