NINETEEN CHANNEL QUANTITATIVE EEG AND EEG BIOFEEDBACK NINETEEN CHANNEL QUANTITATIVE EEG AND EEG...
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NINETEEN CHANNEL QUANTITATIVE EEG
AND EEG BIOFEEDBACK
Robert W. Thatcher, Ph.D.
EEG and NeuroImaging Laboratory, Applied Neuroscience Research Institute., St. Petersburg, Fl
Send Reprint Requests To: Robert W. Thatcher, Ph.D. NeuroImaging Laboratory Applied Neuroscience Res. Inst. St. Petersburg, Florida 33722 (727) 244-0240, firstname.lastname@example.org
Thatcher, R.W. 2
Quantitative electroencephalography (QEEG) is distinguished from visual examination of EEG1 traces, referred to as “non-quantitative EEG” by the fact that the latter is subjective and involves low sensitivity and low inter-rater reliability (Cooper et al, 1974; Woody, 1966; 1968) while the former involves the use of computers and power spectral analyses and is more objective with higher reliability and higher sensitivity (Hughes and John, 1999). The improved sensitivity and reliability of QEEG was first recognized by Hans Berger in 1934 when he performed a QEEG analysis involving the power spectrum of the EEG with a mechanical analog computer (Berger, 1934; Niedermeyer and da Silva, 1995). QEEG in the year 2009 clearly surpasses conventional visual examination of EEG traces because QEEG has high temporal and spatial resolution in the millisecond time domain and approximately one centimeter in the spatial domain which gives QEEG the ability to measure network dynamics that are simply “invisible” to the naked eye. Over the last 40 years the accuracy, sensitive and resolution of QEEG has steadily increased because of the efforts of hundreds of dedicated scientists and clinicians that have produced approximately 90,000 QEEG studies cited in the National Library of Medicine’s database . It is recommended that the reader search the National Library of Medicine database (https://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed) using the key word “EEG” and the few representative citations in this chapter.2 Because of space limitations no reviews of this vast literature will be attempted, instead, the purpose of the present chapter is to briefly describe some of the most recent advances in QEEG as they relate to EEG biofeedback/Neurofeedback.3
Neurological evaluation of space occupying lesions has been correlated with the locations and frequency changes that have been observed in the EEG traces and in QEEG analyses, e.g., lesions of the visual cortex resulted in distortions of the EEG generated from the occipital scalp locations or lesions of the frontal lobe resulted in distortions of the EEG traces arising in frontal regions, etc. However, early neurological and neuropsychological studies have shown that function was not located in any one part of the brain (Luria, 1973). Instead the brain is made up of complex and interconnected groupings of neurons that constitute “functional systems”, like the “digestive system” or the “respiratory system” in which cooperative sequencing and interactions give rise to an overall function at each moment of time (Luria, 1973). This widely accepted view of brain function as a complicated functional system which became dominant in the 1950s and 1960s is still the accepted view today (July 2009). For example, since the 1980s new technologies such as functional MRI (fMRI), PET, SPECT and QEEG/MEG have provided ample evidence for distributed functional systems involved in perception, memory, drives, emotions, voluntary and involuntary movements, executive functions and various psychiatric and psychological dysfunctions. Modern PET, QEEG, MEG and fMRI studies are consistent with the historical view of “functional systems” presented by Luria in the 1950s (Luria 1973), i.e., there is no absolute functional localization because a functional systems of dynamically coupled
1 EEG or the Electroencephalogram is measured from the scalp surface and is produced by the algebraic summation of cortical synaptic potentials. 2 Since approximately 1975 it has been very difficult to even publish studies that only use visual examination of EEG traces. The estimate of 90,000 arises when one uses the search term “EEG” and examines the abstracts to confirm that quantification of EEG was used. It is necessary to use the search term “EEG” and not “QEEG” because the National Library of Medicine indexes articles based on words in the titles and most QEEG studies do not use the term “QEEG” in their titles. 3 While EEG Biofeedback is sometimes referred to as “Neurofeedback” the later term is not specific since many treatments other than EEG may involve neurofeedback. However, in the present chapter these terms are considered synonymous and will be used interchangeably.
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sub-regions of the brain is operating. For example, several fMRI and MRI studies (e.g., diffusion tensor imaging or DTI) have shown that the brain is organized by a relatively small subset of “Modules” or “Hubs” which represent clusters of neurons with high within cluster connectivity and sparse long distance connectivity (Hagmann et al, 2009; Chen et al, 2008; He et al, 2009). Modular organization is a common property of complex systems and ‘Small-World’ models in which maximum efficiency is achieved when local clusters of neurons rely on a small set of long distance connections in order to minimize the “expense” of wiring and shorten time delays between modules (Buzsaki, 2006; He et al, 2009). Also, recent QEEG and MEG analyses have demonstrated that important visually invisible processes such as coherence, phase delays, phase locking and phase shifting of different frequencies is critical in cognitive functions and various clinical disorders (Buszaki, 2006; Sauseng, and Klimesch, 2008; Thatcher et al, 2009a). Phase shift and phase synchrony has been shown to be one of the fundamental processes involved in the coordination of neural activity located in spatially distributed “modules” at each moment of time (Freeman and Rogers, 2002; Freeman et al, 2003; Thatcher et al, 2009a; 2009b). QEEG for Assessment and Neurofeedback for Treatment: A Parent-Child Relationship
This use of the EEG changed dramatically in the 1960s when computers were used to modify the EEG thru biofeedback, referred to today as Neurofeedback (NF). Studies by Fox and Rudell (1968); Kamiya (1971) and Sterman (1973) were a dramatic departure from the classical use of conventional visual EEG and QEEG in that for the first time clinicians could consider treating a disorder such as epilepsy or attention deficit disorders and other mental disorders by using operant conditioning methods to modify the EEG itself. Thus, QEEG and EEG Biofeedback have a “parent-child” relationship in that EEG Biofeedback necessarily uses computers and thus is a form of QEEG that is focused on treatment based on the science and knowledge of the physiological meaning and genesis of the EEG itself. Ideally, as knowledge about brain function and the accuracy and resolution of the EEG increases, then EEG Biofeedback should change in lock step to better link symptoms and complaints to the brain and in this manner treat the patient based on solid science. To the extent the EEG can be linked to functional systems in the brain and to specific mental disorders then EEG Biofeedback could “move” the brain toward a healthier state (i.e., “normalize” the brain) (Thatcher 1998; 1999). Clearly, the clinical efficacy of EEG Biofeedback is reliant on knowledge about the genesis of the electroencephalogram and specific functions of the human brain. The parent-child relationship and inter-dependencies between QEEG and EEG Biofeedback is active today and represents a bond that when broken results in reduced clinical efficacy and general criticism of the field of EEG biofeedback. The traditional and logical relationship between QEEG and NF is to use QEEG to assess and NF to treat based on a linkage between the patient’s symptoms and complaints and functional systems in the brain. This parent/child linkage requires clinical competence on the one hand and technical competence with computers and the EEG on the other hand. Competence in both is essential and societies such as ISNR, SAN, ABEN, ECNS, BCIA, AAPB and other organization are available to help educate and test the requisite qualifications and competence to use EEG biofeedback. The parent/child link is typically optimized by following three steps: 1- perform a careful and thorough clinical interview and assessment of the patient’s symptoms and complaints (neuropsychological assessments are the most desirable), 2- conduct a QEEG in order to link the patient’s symptoms and complaints to functional systems in the brain as evidenced in fMRI, PET and QEEG/MEG and, 3- devise a EEG biofeedback
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protocol to address the de-regulations observed in the QEEG assessment that best match the patient’s symptoms and complaints. This approach reinforces the close bond between parent (QEEG) and child (Neurofeedback) and allows for the objective evaluation of the efficacy of treatment in terms of both behavior and brain function.
Figure one illustrates a common modern quantitative EEG analysis where conventional EEG traces are viewed and examined at the same time that quantitative analyses are displayed so as to facilitate and extend the analytical power of the EEG. Seamless integration of QEEG and Neurofeedback involves two basic steps: 1- visual examination of the EEG traces and 2- Spectral analyses of the EEG traces4. Numerous studies have shown a relationship between the time domain and frequenc