Phase Sync sums the EEG signal in the 4 channels in the different bands. This is how DMN4C works in BioExplorer (Default Mode Network) with AFZ Pz P3 P4. Sync trains coherence and phase.

Regarding training with the CON Phase Sync design, one of the advantages is that the phase lag calculation is based on the instantaneous values derived from the EEG signal. The principle behind it is quite simple: it checks if two EEG signals, at the specified frequencies, are rising and falling simultaneously. This makes the feedback response much quicker. More elaborate measures, such as coherence and the absolute value of the phase angle, which are used in other designs in the CON category, require a bunch of samples for the calculations to be performed properly.

The measure of synchrony based on instantaneous EEG values was an approach widely used in the early decades of neurofeedback, when there weren’t technologies sophisticated enough to perform coherence calculations in real time. Several classic protocols were developed from this approach and had very good results.

In practice, both training strategies have their place. While the more elaborate calculations provide a more detailed reading of the relationships between two sites, allowing, in theory, for deeper work, the “lighter” approach translates the message in a very direct way so that the brain can easily recognize itself on the feedback mirror.