Frequency-domain localization of intracerebral dipolar sources.

A frequency-domain localization of intracerebral dipolar sources can be carried out basically in the same way as a time-domain localization, since the minimization problems to be solved in the two cases have exactly the same structure. The quantity to be minimized can be interpreted as a sum of residual variances of independent linear minimization problems. In the time domain there is one linear problem per sampling time, whereas in the frequency domain there are two linear problems per frequency. It is demonstrated that algorithms readily available for the solution of the time-domain inverse problem can also be used for the solution of the frequency-domain inverse problem. In this way it is not only possible to localize multiple dipoles, but also to combine information from different epochs and from different frequencies.