Coherence is the frequency dependent squared cross correlation between two scalp electrode sites which reflects the degree of phase synchrony between them (Gevins, 1989; Nunez, 1981; Thatcher, Walker, & Giudice, 1987). Coherence values (range: 0 to 1) may be related to the strength and number of synaptic connections (Thatcher, 1994), and thus may reflect the level of connectivity between two EEG recording sites. Power and coherence measures both show changes with development and both are associated with cognitive processing (e.g., Bell & Fox, 1992; Cuevas & Bell, 2011).
