Non-invasive scalp measurements of electric potentials (EEG) [as well as magnetic fields (MEG)] can be used for estimating the electric neuronal activity distribution (current density vector field) on the cortex. The methods used here are LORETA, standardized LORETA (sLORETA), and exact LORETA (eLORETA).
Time series of cortical electric neuronal activity computed with LORETA can be used for estimating intracortical functional and effective connectivity. A collection of new methods are included here, especially well-suited for signals from these tomographies:
1. Lagged coherence and lagged phase synchronization.
2. Dynamic intracortical connectivity in terms of senders, hubs, and receivers.
3. Partial coherence fields.
4. Isolated effective coherence.
5. Functional ICA (in the sense of functional data analysis) for discovering generalized functional connectivity across space, frequency, and time.
All these methods and much more are programmed and available in the alpha LORETA-KEY software package.