Brain Wave Coherence

Coherence is the condition of synchrony between the waves generated in different regions or hemispheres of the brain. (Coherence is having waves in phase and of one wavelength)

A prominent feature of a waveform is its frequency. This is the first measure of synchrony. For example: if the left and right occipital lobes are generating Alpha waves of similar frequencies, there is some coherence between them. The second measure to compare two waveforms is the phase angle between them. In the illustration, two sine waves of the same frequency are juxtaposed. One leads the other by a phase angle.

It is too much to ask that Brain Waves be at exactly the same frequency and exactly the same phase angle. A small difference in frequency is allowed. The phase angle can be as much as 90 degrees out of phase.