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Early work with EEG biofeedback focused on the benefits and working of particular EEG states in contrast to others. Alpha was initially said to be good for relaxation; SMR for epilepsy and attention deficit with hyperactivity; Beta for attention deficit without hyperactivity; and Theta for alcoholism. The majority of researchers and clinicians emphasized what one frequency band could do, rather than paying particular attention to patterns of brain wave activity, how they correlated with treatment outcome, or the implications they had for defining the patient's state of mind. Some early clinical research is suggesting that in addition to the amplitude of a particular frequency or range of frequencies, it is also advisable to notice the per cent of the time that frequency is active, and the relationship among the activities of the different bands. For instance, initial interest in Alpha- Theta EEG training with alcoholics soon became modified when it became clear that a significant proportion of them lost memory, attention, and concentration facility when the lower frequencies were overemphasized in relation to Beta activity. There soon needed to be ways to make Theta evocation contingent on adequate amounts of Beta activity. The idea of ratios sprang up and we now see "high" (5:1 to 2:1) ratios of Theta to Beta power activity signs of loosening of cognitive controls. There is, however, some good rationale for using methods other than simple ratios for looking at relationships among different EEG bands (especially when the band have different widths) which still talk about the effects of relationships among band activity on consciousness. Further, recent information suggests that the more narrowly the band can be defined, down to one Hz, the clearer will be the relationship to consciousness. Much more research is needed to validate, clarify, and extend these concepts.
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