 In comparison with other QEEG measures, such as absolute power or relative power, cordance appears to have a superior correlation  with regional brain perfusion, one of the other standard measures of regional brain activity.Because cordance is derived from EEG signals, assessments of brain function with cordance do not require the use of radioactive tracer molecules, as is the case with some other functional neuroimaging methods (PET or SPECT scanning).Cordance has been applied to studying brain activity in a variety of neurological and psychiatric disorders.