Comments on: Derived Feedback Metrics such as Z-score Training http://qeegsupport.com/derived-feedback-metrics-such-as-z-score-training/ Quantitative Electroencephalography (qEEG): Information & Discussion Mon, 12 Sep 2011 20:22:48 -0400 http://wordpress.org/?v=2.8.4 hourly 1 By: Jay Gunkelman http://qeegsupport.com/derived-feedback-metrics-such-as-z-score-training/comment-page-1/#comment-58 Jay Gunkelman Fri, 15 Apr 2011 18:09:27 +0000 http://qeegsupport.com/?p=413#comment-58 An abnormal EEG finding can often change coherence. Coherence is a phase stable spatial pattern of a spectral feature, and a focal spectral event will not have the same spatial phase pattern as the normal background rhythmicity does, so it will be an outlier in Z-score space that can be normalized by removing the focal event... not by altering the background coherence. Shifted frequencies cause a background coherence pattern to be mis-read by the database as an aberant pattern, when it may be prefectly normal for the rhythm if it were tuned (frequency adjusted) properly... altering the coherence is not the NF fix in this situation, but rather a re-tuning of the aberrantly shifted frequency. The coherence needs to be understood... and whether to feed it back or not picked based on a real coherence issue, not a distortion due to aberrant tuning or a focal event issue. An abnormal EEG finding can often change coherence. Coherence is a phase stable spatial pattern of a spectral feature, and a focal spectral event will not have the same spatial phase pattern as the normal background rhythmicity does, so it will be an outlier in Z-score space that can be normalized by removing the focal event… not by altering the background coherence.

Shifted frequencies cause a background coherence pattern to be mis-read by the database as an aberant pattern, when it may be prefectly normal for the rhythm if it were tuned (frequency adjusted) properly… altering the coherence is not the NF fix in this situation, but rather a re-tuning of the aberrantly shifted frequency.

The coherence needs to be understood… and whether to feed it back or not picked based on a real coherence issue, not a distortion due to aberrant tuning or a focal event issue.

]]> By: GarySchummer http://qeegsupport.com/derived-feedback-metrics-such-as-z-score-training/comment-page-1/#comment-57 GarySchummer Wed, 13 Apr 2011 17:38:17 +0000 http://qeegsupport.com/?p=413#comment-57 Very good point regarding individuals with peak frequency scores that are atypically high or low. In these cases would you suggest we interpret any coherence deviations with even more caution or disregard them entirely? Many times when I get an abnormal read by the neurologist such as a temporal lobe slowing or sharp epileptiform activity and proceed to normalize these with NFB and then re-Q the second Q shows coherence readings that are very different from what I got when the abnormality was present. Would you say this is an analogous situation? Very good point regarding individuals with peak frequency scores that are atypically high or low. In these cases would you suggest we interpret any coherence deviations with even more caution or disregard them entirely? Many times when I get an abnormal read by the neurologist such as a temporal lobe slowing or sharp epileptiform activity and proceed to normalize these with NFB and then re-Q the second Q shows coherence readings that are very different from what I got when the abnormality was present. Would you say this is an analogous situation?

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