LORETA (low resolution brain electromagnetic tomography) is a technique for functional imaging of the human brain. It computes the three dimensional distribution of electric neuronal activity (throughout cortical grey matter) from non-invasive measurements of scalp electric potential differences (EEG: electroencephalogram), with high time resolution in the millisecond range. The non-invasive intracranial time series are used for studying functional dynamic connectivity. The current software implementation is limited to EEG, although LORETA is defined for EEG and MEG (magnetoencephalogram). The standardized and exact versions of LORETA produce images with zero localization error.