QEEG Cordance

What is Cordance?
                Cordance is a quantitative EEG measure that integrates information from absolute and relative power measures. Cordance is calculated from power using a three step algorithm, which is defined in detail in this 1999 paper from Psychiatry Research Neuroimaging (abstract paper). It is more closely correlated with regional cerebral perfusion (blood flow) than these other two conventional QEEG measures. We developed cordance at the UCLA QEEG Laboratory in order better to study regional brain activity (references), i.e. which areas of the brain are more active or less active under specific conditions.

                Cordance has shown particular use in research in depression (references), including our current research projects.

The Method
                Cordance can be calculated from data collected with any QEEG recording system, using software that we can provide free-of-charge to any academic institution1. This software calculates cordance from QEEG power using an Excel macro. The input for this macro is an Excel spreadsheet containing absolute QEEG power values for a list of bipolar electrode pairs. Cordance requires a minimum of 19 EEG scalp electrodes. We most commonly use a montage with 36 scalp electrodes that is an extension of the International 10-20 system. The electrode pairs that we use are listed here, and are shown graphically in the figure at the right.

                For those users who are recording data with a standard International 10-20 montage, a truncated list of electrode pairs also can be used. Most QEEG systems can export these power values as a tab or space delimited file that can be imported into Excel for processing; please consult your system users' manual, as we are unable to consult on the operation of QEEG systems.

                The output from the Excel macro is spreadsheet containing numerical cordance values that can be graphed, mapped, or used for statistical analysis. For those users who do not have a mapping capability, we do have a limited capacity to help prepare topographic maps; please contact us if you need this assistance.

                If you are conducting research at an academic institution and would like to obtain free cordance software,1 please contact us by e-mail at

References

Background Materials on the Cordance Method

Leuchter AF, Uijtdehaage SH, Cook IA, O'Hara R, Mandelkern M.
Relationship between brain electrical activity and cortical perfusion in normal subjects.
Psychiatry Res. 1999 Apr 26;90(2):125-40. abstract full text

Cook IA, O'Hara R, Uijtdehaage SH, Mandelkern M, Leuchter AF.
Assessing the accuracy of topographic EEG mapping for determining local brain function.
Electroencephalogr Clin Neurophysiol. 1998 Dec;107(6):408-14. abstract full text

Leuchter AF, Cook IA, Mena I, Dunkin JJ, Cummings JL, Newton TF, Migneco O, Lufkin RB, Walter DO, Lachenbruch PA.
Assessment of cerebral perfusion using quantitative EEG cordance.
Psychiatry Res. 1994 Sep;55(3):141-52. abstract full text

Leuchter AF, Cook IA, Lufkin RB, Dunkin J, Newton TF, Cummings JL, Mackey JK, Walter DO.
Cordance: a new method for assessment of cerebral perfusion and metabolism using quantitative electroencephalography.
Neuroimage. 1994 Jun;1(3):208-19. abstract full text

Application of Cordance in Mood Disorders Research

Hunter AM, Leuchter AF, Morgan ML, Cook IA, Abrams M, Siegman B, Debrota DJ, Potter WZ.
Neurophysiologic correlates of side effects in normal subjects randomized to venlafaxine or placebo
Neuropsychopharmacology 2005 Apr;30(4):792-9. epub 2004 Dec 22 [ahead of print] abstract full text

Krell HV, Leuchter AF, Morgan M, Cook IA, Abrams M.
Subject expectations of treatment effectiveness and outcome of treatment with an experimental antidepressant.
J Clin Psychiatry. 2004 Sep;65(9):1174-9. abstract full text

Stubbeman WF, Leuchter AF, Cook IA, Shurman BD, Morgan M, Gunay I, Gonzalez S.
Pretreatment neurophysiologic function and ECT response in depression.
J ECT. 2004 Sep;20(3):142-144. abstract full text

Leuchter AF, Morgan M, Cook IA, Dunkin J, Abrams M, Witte E.
Pretreatment neurophysiological and clinical characteristics of placebo responders in treatment trials for major depression.
Psychopharmacology (Berl). 2004 Jul 14 abstract full text

Cook IA, Leuchter AF, Morgan M, Witte E, Stubbeman WF, Abrams M, Rosenberg S, Uijtdehaage SH.
Early changes in prefrontal activity characterize clinical responders to antidepressants.
Neuropsychopharmacology. 2002 Jul;27(1):120-31. abstract full text

Leuchter AF, Cook IA, Witte EA, Morgan M, Abrams M.
Changes in brain function of depressed subjects during treatment with placebo.
Am J Psychiatry. 2002 Jan;159(1):122-9 abstract full text

Cook IA, Leuchter AF.
Prefrontal changes and treatment response prediction in depression.
Semin Clin Neuropsychiatry. 2001 Apr;6(2):113-20. abstract

Cook IA, Leuchter AF, Witte E, Abrams M, Uijtdehaage SH, Stubbeman W, Rosenberg-Thompson S, Anderson-Hanley C, Dunkin JJ.
Neurophysiologic predictors of treatment response to fluoxetine in major depression.
Psychiatry Res. 1999 Mar 22;85(3):263-73. Erratum in: Psychiatry Res 2000 Jul 24;95(1):87. abstract full text corrigendum

Cook IA, Leuchter AF, Uijtdehaage SH, Osato S, Holschneider DH, Abrams M, Rosenberg-Thompson S.
Altered cerebral energy utilization in late life depression.
J Affect Disord. 1998 May;49(2):89-99. abstract full text

Leuchter AF, Cook IA, Uijtdehaage SH, Dunkin J, Lufkin RB, Anderson-Hanley C, Abrams M, Rosenberg-Thompson S, O'Hara R, Simon SL, Osato S, Babaie A.
Brain structure and function and the outcomes of treatment for depression.
J Clin Psychiatry. 1997;58 Suppl 16:22-31. abstract full text

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last revised: 29 March 2005 iac

1   Cordance is a software algorithm that has been patented by the University of California, but has been implemented in software available free-of-charge to academic researchers. Researchers will be asked to certify that they will use the software for non-commercial research purposes only, and that they will not modify or distribute copies of the software to others.