Cordance

Cordance is a QEEG method, developed in Los Angeles in the 1990s,^{[1] [2]} which combines complementary information from absolute (the amount of power in a frequency band at a given electrode) and relative power (the percentage of power contained in a frequency band relative to the total spectrum) of EEG spectra.^[3]

Cordance is a measure of regional brain activity. It is computed using quantitative electroencephalographic (QEEG) measures of brain wave patterns in an algorithm developed at the UCLA Laboratory of Brain, Behavior, and Pharmacology by Drs. Andrew Leuchter and Ian Cook.

The cordance algorithm includes steps of (a) reattribution of EEG power,^{[4] [5]} (b) spatial normalization of absolute and relative power, and (c) combination of the transformed absolute and transformed relative power to yield the cordance values themselves.

In comparison with other QEEG measures, such as absolute power or relative power, cordance appears to have a superior correlation ^[6] 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. A major area of study has been major depressive disorder, in efforts to develop biomarkers that could help guide treatment.^{[7][8] [9] [10] [11]} This line of work was begun in the mid 1990s at UCLA and is now the subject of replication studies at other medical centers.^{[12] [13] [14] [15] [16]}

References

1. Leuchter, Andrew and Cook,Ian. "Method and Apparatus for determining...". Expired US Patent. US Patent and Trademark Office. Retrieved 24 March 2013.
2. Leuchter, A. (1999). "Relationship between brain electrical activity and cortical perfusion in normal subjects". Psychiatry Research: Neuroimaging 90 (2): 125–140. doi:10.1016/S0925-4927(99)00006-2.
3. Bares, M.; Brunovsky, M.; Kopecek, M.; Novak, T.; Stopkova, P.; Kozeny, J.; Sos, P.; Krajca, V.; Höschl, C. (2008). "Early reduction in prefrontal theta QEEG cordance value predicts response to venlafaxine treatment in patients with resistant depressive disorder". European Psychiatry 23 (5): 350–355. doi:10.1016/j.eurpsy.2008.03.001. PMID 18450430.
4. Cordance. "Cordance Montage Figure 600x600". Wikimedia Commons. Retrieved 24 March 2013.
5. Cordance. "Cordance Montage Figure 3000x3000". Wikimedia Commons. Retrieved 24 March 2013.
6. Leuchter, A. (1999). "Relationship between brain electrical activity and cortical perfusion in normal subjects". Psychiatry Research: Neuroimaging 90 (2): 125–140. doi:10.1016/S0925-4927(99)00006-2.
7. Cook, I.; Leuchter, A. F.; Morgan, M.; Witte, E.; Stubbeman, W. F.; Abrams, M.; Rosenberg, S.; Uijtdehaage, S. H. (2002). "Early Changes in Prefrontal Activity Characterize Clinical Responders to Antidepressants". Neuropsychopharmacology 27 (1): 120–131. doi:10.1016/S0893-133X(02)00294-4. PMID 12062912.
8. Cook, I.; Leuchter, A.; Morgan, M.; Stubbeman, W.; Siegman, B.; Abrams, M. (2005). "Changes in prefrontal activity characterize clinical response in SSRI nonresponders: A pilot study". Journal of Psychiatric Research 39 (5): 461–466. doi:10.1016/j.jpsychires.2004.12.002. PMID 15992554.
9. Hunter, A. M.; Muthén, B. O.; Cook, I. A.; Leuchter, A. F. (2010). "Antidepressant response trajectories and quantitative electroencephalography (QEEG) biomarkers in major depressive disorder". Journal of Psychiatric Research 44 (2): 90–98. doi:10.1016/j.jpsychires.2009.06.006. PMC 2925497. PMID 19631948.
10. Cook, I. A.; Hunter, A. M.; Abrams, M.; Siegman, B.; Leuchter, A. F. (2009). "Midline and right frontal brain function as a physiologic biomarker of remission in major depression". Psychiatry Research: Neuroimaging 174 (2): 152. doi:10.1016/j.pscychresns.2009.04.011.
11. Hunter, A. M.; Leuchter, A. F.; Cook, I. A.; Abrams, M. (2010). "Brain functional changes (QEEG cordance) and worsening suicidal ideation and mood symptoms during antidepressant treatment". Acta Psychiatrica Scandinavica 122 (6): 461–469. doi:10.1111/j.1600-0447.2010.01560.x. PMID 20384600.
12. Horacek, J.; Brunovsky, M.; Novak, T.; Tislerova, B.; Palenicek, T.; Bubenikova-Valesova, V.; Spaniel, F.; Koprivova, J.; Mohr, P.; Balikova, M.; Hoschl, C. (2009). "Subanesthetic dose of ketamine decreases prefrontal theta cordance in healthy volunteers: Implications for antidepressant effect". Psychological Medicine 40 (9): 1443–1451. doi:10.1017/S0033291709991619. PMID 19995475.
13. Bares, M.; Brunovsky, M.; Novak, T.; Kopecek, M.; Stopkova, P.; Sos, P.; Krajca, V.; Höschl, C. (2010). "The change of prefrontal QEEG theta cordance as a predictor of response to bupropion treatment in patients who had failed to respond to previous antidepressant treatments". European Neuropsychopharmacology 20 (7): 459–466. doi:10.1016/j.euroneuro.2010.03.007. PMID 20421161.
14. Bares, M.; Novak, T.; Brunovsky, M.; Kopecek, M.; Stopkova, P.; Krajca, V.; Höschl, C. (2012). "The change of QEEG prefrontal cordance as a response predictor to antidepressive intervention in bipolar depression. A pilot study". Journal of Psychiatric Research 46 (2): 219–225. doi:10.1016/j.jpsychires.2011.09.006. PMID 21937059.
15. Arns, M.; Drinkenburg, W. H.; Fitzgerald, P. B.; Kenemans, J. L. (2012). "Neurophysiological predictors of non-response to rTMS in depression". Brain Stimulation 5 (4): 569–576. doi:10.1016/j.brs.2011.12.003. PMID 22410477.
16. Broadway, J. M.; Holtzheimer, P. E.; Hilimire, M. R.; Parks, N. A.; Devylder, J. E.; Mayberg, H. S.; Corballis, P. M. (2012). "Frontal Theta Cordance Predicts 6-Month Antidepressant Response to Subcallosal Cingulate Deep Brain Stimulation for Treatment-Resistant Depression: A Pilot Study". Neuropsychopharmacology 37 (7): 1764–1772. doi:10.1038/npp.2012.23. PMC 3358746. PMID 22414813.