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BRL Technology Development

Development of a Normative and Abnormal QEEG Database and Normative Equations

During 30 years of basic and clinical study, BRL has constructed and maintained the largest EEG, QEEG and ERP database in the world. Support for such endeavors was provided by large research grants from the RANN Program  (Research Applied To National NEEDS) of the National Science Foundation, the Bureau for the Educationally Handicapped (BEH) of the US Office of Education, and the National Institutes of Health, as well as from a number of biomedical instrument companies.

This digitally accessible system contains over 20,000 recordings as well as clinical and demographic information recorded from normal subjects and patients with a wide variety of developmental, neurological, and psychiatric problems, as well as patients undergoing surgery for cardiovascular or neurological disorders. This database consists of digital media encoding raw records as well as extracted quantitative descriptors, and is therefore readily accessible fro retrospective re-evaluation whenever it seems desirable.

From every individual in large cohorts of children, young, mature, and elderly adults ranging from 6 tom 90 years of age, all screened carefully by using neurological, psychological, and psychiatric examinations as well as their social histories, EEG and multimodal ERP (visual, auditory, P300, somatosensory) recordings were made under carefully standardized conditions. A set of about 2000 features was extracted from each of these recordings. These measures displayed extremely lawful development with age. Therefore, using these data transformed to yield Gaussianity, a set of normative equations were constructed to provide the mean value and standard deviations for the distribution of each of these variables as a function of age. These normative equations have been independently confirmed in over 15 countries, and found to be independent of ethnic or cultural influences. The use of Z-values to convert every QEEG feature to standard scores relative to a normative reference has been adopted as standard practice  in QEEG research and clinical studies throughout the world.