On the self-regulation of the occipital alpha rhythm: control strategies, states of consciousness, and the role of physiological feedback.

In an experiment investigating the self-control of occipital alpha strength, a factorial design was employed with two levels of feedback (available or non-available), three levels of instruction (Cognitive, Oculomotor, and none), and two levels of lighting (on and off), except that the no-feedback-no-instruction group was not run. The Cognitive instructions were based on the strategies reported in the literature: To generate alpha, persons were instructed to relax, "let go", try to feel pleasant and serene, and allow themselves to review pleasant personal experiences; to suppress alpha, persons were instructed to concentrate, try hard, exert themselves mentally, and try to fell anxious or frustrated. The Oculomotor instructions to generate alpha were to visually blur and not focus, and to suppress alpha were to "look" and focus. The results led to the following conclusions: (a) Feedback-augmented enhancement and suppression of occipital alpha strength is always mediated by learned control of oculomotor processes, although sometimes persons are not aware that they are employing this strategy, especially in the case of alpha enhancement; alpha feedback trainees learn to "not look" in order to enhance alpha strength. (b) Whenever Cognitive strategies are successful in producing alpha strength changes, this is due to the fact that they can be efficient mediators of changes in oculomotor processes. (c) Feedback together with simple Oculomotor instructions leads to more successful alpha control than either alone. (d) High or enhanced levels of occipital alpha strength are not invariably accompanied by the "alpha experience", in fact, if a person is not led to expect it, the alpha experience will usually not occur during occipital alpha enhancement feedback. (e) States of nonsensory awareness, such as an absorption in thoughts and feelings, are reliably associated with enhanced occipital alpha strength. This association is what would be expected: Since vision is the dominant sensory modality in humans, it is reasonable that when visual processing is reduced during alpha enhancement feedback that there is also reduced sensory awareness in general and often greater attention to thoughts and feelings. (f) Alpha feedback per se is neither necessary for nor especially facilitative of the achievement of the alpha experience. Thus, if the alpha experience is more likely to occur with alpha feedback than without it, this is due to the special circumstances that make up the feedback situation and not due to alpha feedback per se.