QEEG and Z-Score Training
Since the late 1990s, the development in the field of Neurofeedback has been moving towards individualized therapy. One approach that has emerged in this context is the QEEG – the quantitative EEG. The EEG data collected are compared with those from a standard database. The theory behind this is that certain clinical pictures or symptoms can be identified from the comparison with standard data and the Neurofeedback training can thereby be individualized. The QEEG method is therefore actually in the field of neurodiagnostics, although the diagnostic possibilities are still controversial. Thus, there are currently only a few clinical pictures for which there are first indications of effectiveness of this method.
What does Z-Score mean?
The “Z-Score” is also closely related to the QEEG. The Z-Score is a statistical value that indicates how far the value measured for an individual is from the mean value of a measured comparison group (standard value).
The question repeatedly arises whether there are endophenotypes for neurological disorders, i.e. certain features that can be read in the QEEG and can be used as biological markers, so to speak, to recognize diseases. There are first indications for such endophenotypes, which are determined from various parameters of the QEEG, for example for ADHD, schizophrenia and anxiety disorders.
QEEG and Z-Score Training – the basis for individual Neurofeedback therapy?
It remains questionable to what extent this data can be used for personalized Neurofeedback training. In practice, the Neurofeedback protocols derived from the QEEG generally correspond to the conventional SMR / Beta protocols of classic frequency band training, in which SMR and beta amplitudes are rewarded and slower and faster frequency bands are inhibited.
This may be due to the fact that the diagnostic value, which results primarily from the measurement of event-related potentials in the QEEG and the corresponding calculations, cannot be converted 1: 1 into frequency band training. Although QEEG data are the most useful diagnostic tools for ADHD, a recent study showed no significant differences in the improvement of ADHD symptoms between a control group with placebo feedback and a QEEG Neurofeedback group.
In the treatment of reoccurring migraine attacks, however, Walker (Neuroscience 2011; 42: 59-61) was able to show a drastic reduction in migraine attacks after the QEEG Neurofeedback training.