24 augustus 2010

Neurofeedback with Z scores

look at the library of articles here

Bob Thatcher wrote on the Neuroguide list a very good introductory text::

The physiological mechanism underlying all EEG biofeedback is called "Operant Conditioning" and Eric Kandel was one of the first scientists to study the "subconscious" mechanisms of operant conditioning in the aplysia isolated nervous system. The basic mechanism involves "novelty" of the feedback signal that follows a neural event. Over repeated trials then neurotransmitter output increases resulting in more cyclic AMP and protein kinase A that activates CREB and RNA growth mechanisms that increase the size and number of synapses. Thus, the issue of more than one channel and the neurophysiology of subconscious operant conditioning is a scientifically settled issue (Kandel won a Nobel prize in 2000 for this work – see Kandel's book "In search of Memory" Histead et al, 2009. Learning Substrates in the Primate Prefrontal Cortex and Striatum: Sustained Activity Related to Successful Actions, Neuron 63, 244–253, Brembs, B., Lorenzetti, F. D., Reyes, F. D., Baxter, D. A., & Byrne, J. H. (2002). Operant reward learning in Aplysia: neuronal correlates and mechanisms. Science, 296(5573), 1706-1709, etc.)

What is new is the use of Z scores rather than absolute values to determine the threshold for delivery of the feedback signal. Over the last four years about 300 uses of simultaneous 248 multichannel Z score biofeedback has been shown to be successful in hundreds of patients. There have been several publications showing reduced qEEG deviations and improved clinical outcome in less than 20 sessions and often less than 10 sessions. A partial list of publications is available on the Brainmaster website at:


I hypothesize that one of the reason that multiple Z scores provide fewer sessions and good clinical outcome is because Z = 0 is a type of homeostatic set-point that optimizes the efficiency and coupling in resonant networks. Highly deviant Z scores represent a form of deregulation that results in reduced sensitivity and availability of neural resources to be allocated or synchronized. Another reason is that the use of a Z score simplifies the selection of a threshold to deliver feedback. Without a Z score target of Z = 0 requires users to guess at a threshold, e.g., should I reward theta for values less than 30 uV or less than 20 uV or 10 uV? If one reinforces SMR in a patient with 3 st. dev. Excess SMR is this good? Or should I reward coherence when it is greater than 0.4 or 0.6 or 0.8? ,etc. Coherence and power and phase involve different metrics and are different for different locations, different frequencies, different ages, etc which means that it is difficult to identify deregulation and to determine an optimal threshold. Z scores solve this problem and simplify EEG biofeedback. Finally, changes toward Z = 0 automatically involve the most deviant Z scores which are likely more related to "weak" systems or "loss of function" systems as described by Luria and others. As a consequence Z scores are naturally more targeted toward deregulated neural systems involved in the genesis of the patient's symptoms and complaints.

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