We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
Published online by Cambridge University Press: 05 August 2012
Electromagnetic activity of the brain
The electromagnetic activity of the human brain is governed by the quasi-static theory of Maxwell's equations [229, 284] which, to some extent, decouples the electric from the magnetic behavior. The brain is modelled as a conductive medium with certain conductivity and a magnetic permeability which is equal to the permeability of the air. The brain is surrounded first by the cerebrospinal fluid, then by the skull, and finally by the scalp, all having different conductivities but the same magnetic permeability. In most cases though the brain–head system is assumed to be a single homogeneous medium. A primary neuronal current within the conductive brain tissue excites a secondary induction current and both currents generate an electric potential, which is measured on the surface of the head, and a magnetic flux, which is measured outside, but close to, the head. Recordings of the electric potential concern the theory of electroencephalography (EEG) and recordings of the magnetic flux density concern the theory of magnetoencephalography (MEG). The forward problem of EEG or MEG consists of the calculation of the electric potential or the magnetic induction, respectively, from a complete knowledge of the primary neuronal current. The inverse problem of EEG or MEG consists of the identification of the location and intensity of the neuronal current from the electric potential or the surface of the head, or of the magnetic induction outside the head, respectively.
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
