When charged particles, such as electrons, are accelerated, they generate an electromagnetic (EM) field. Typically, such a field is produced by alternating current in electrical conductors, which can have various frequency ranges (the standard unit of EM frequency being the hertz). Magnetic resonance imaging (MRI) involves the sophisticated use of EM fields to produce images of the body and brain that have a high degree of spatial and contrast resolution. Environmental exposure to low EM fields (e.g., mobile phones, power lines) that are a class of non-ionizing radiation has in recent years led to public concern about their possible deleterious effects on brain functioning among other things. As for the EM fields produced by brain, some neuroscientists have proposed that they might be the basis of conscious awareness, and which is encapsulated in an EM field theory of consciousness. The scientific breakthrough in establishing the existence of EM fields came from the work of James Clerk Maxwell (1831-1879). His extension of the theories of electricity and magnetic lines of force put forward by Michael Faraday (1791-1867), led to the unification of EM field and magnetic field theory. He did so through the medium of four partial differential equations (now referred to as Maxwell’s equations) that expressed the behavior of electrical and magnetic fields and their interrelated nature. In this respect, Maxwell might be considered to have provided the foundations for some of the modern neuroimaging techniques.
See Brain (neuro-) imaging, Magnetic resonance imaging (MRI), Transcranial magnetic stimulation (TMS)