EEG and Brain Connectivity: A Tutorial - Bio-Medical Instruments, Inc.

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again emphasizes the importance of approximation to a Gaussian for any normative QEEG database (Thatcher et al, 2003). The standard concepts underlying the Z score statistic and QEEG evaluations were recently combined to give rise to real-time EEG Z score biofeedback, also referred to as “Live Z Score Biofeedback” (Thatcher 1998a; 1998b; 2000a; 2000b; Thatcher and Collura, 2006; Collura et al, 2009). The use of real-time Z score EEG biofeedback is another method to advance the integration of QEEG and Neurofeedback. The figure below illustrates the differences between raw score EEG biofeedback and real-time Z score EEG biofeedback. Diagram of the difference between standard EEG biofeedback and Z score EEG biofeedback. The top system involves standard EEG biofeedback that relies on raw EEG measures such as power, coherence, phase, amplitude asymmetries and power ratios and an arbitrary and subjective threshold value. The bottom system is the same as the top but with a transform of the raw scores to Z scores and thus a simplification of diverse metrics to a single metric of the Z score in which the threshold is mathematically defined as a movement toward Z = 0. The magnitude of the Z score provides real-time feedback as to the distance between the patient’s EEG and the EEG values in an age matched sample of healthy normal control subjects. There are several advantages of real-time Z score biofeedback including: 1- Simplification by reducing different metrics (power, coherence, phase, asymmetry, etc.) to a single common metric of the Z
score; 2- Simplification by providing a threshold and direction of change i.e., Z = 0 to move the EEG toward a normal healthy reference population of subjects, 4 and 3- improved linkage between patient’s complaints and symptoms and localization of functional systems in the brain. The next three figures show examples of how a symptom check list and QEEG evaluation are linked to give rise to a neurofeedback protocol. Example of a computer generated Symptom Check list in which the clinician first evaluates the patient’s symptoms and complaints using clinical and neuropsychological tools and then enters a score of 0 to 10 based on the severity of the symptoms. Hypotheses as to the most likely scalp locations and brain systems are then formed based on the scientific literature that links symptoms and complaints to the locations of functional specialization. (From NeuroGuide 2.5.7) Modules or “Hubs” are linked to various basic functional systems that are involved in cognition and perception (Hagmann et al, 2009; Chen et al, 4 Simultaneous suppression of excessive theta and reinforcement of deficient beta is achieved by using a absolute Z score threshold, which is a simplification compared to standard raw score EEG biofeedback. For example, if the threshold is set to an absolute value of Z < 2, then reduced theta amplitude and elevated beta amplitude will both be rewarded when the instantaneous EEG event exhibits a Z < 2 theta and beta power value.
Page 1 and 2: (unpublished manuscript - Version 1
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EEG and Brain Connectivity: A Tutorial - Bio-Medical Instruments, Inc.

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