Summary1. The immunocompetence handicap hypothesis (ICHH) proposes that androgen-induced immunosuppression is the mechanism that restricts the expression of exaggerated male ornaments to superior males. Numerous tests of this hypothesis have been conducted on the humoral and cell-mediated components of immunity, with mixed results. Surprisingly, no study so far has addressed whether macrophage phagocytosis, a basic immune function, plays a role in the ICHH. 2. We tested whether the ornament size of male spotless starlings (Sturnus unicolor) is a predictor of in vitro macrophage phagocytosis. We found that a moderate physiological concentration of testosterone (T) induced strong phagocytic inhibition. We found no relationship between ornament size and phagocytic activity in basal conditions. 3. Basal phagocytosis was not significantly predicted by ornament size or original testosterone levels. Contrary to expectations, phagocytosis under a moderate T concentration was negatively related to ornament size. Furthermore, a nonsignificant trend for original T concentration to negatively affect T-medium phagocytosis was also found. 4. Our results provide support to the ICCH and suggest that males with exaggerated ornaments and high T concentrations may counteract the inhibitory action of testosterone by some compensatory mechanism. Possible candidates include the presence of immunoenhancing substances, such as melatonin or antioxidants, or differential receptor activity. These mechanisms should be evaluated when testing the reliability of the ICCH in wild populations.

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Current research and clinical practice employing EEG biofeedback involves a variety of complex instrumentation. This paper describes the conceptualizations involved in the development of such instrumentation and provides a description of different methods, including analog processing, digital processing (spectral analysis), and zero-crossing methodology. The advantages and disadvantages of each methodology are considered, as well as factors relating to difficulty of design, data acquisition, and cost. A detailed description is presented of one system that allows for extraction of a small signal (sensorimotor rhythm) from high-amplitude, mixed-frequency background EEG and provides feedback for this activity in the absence of specific artifacts and EEG frequencies for which specialized circuitry has been developed. Problems related to methods of feedback display are considered.During the past 10 years, there has been a rapid development of methodologies designed to detect and feed back signals derived from the EEG of both human and animal subjects. Work with humans using this methodology began in the late 1960s with the early work of Kamiya (1969) and his colleagues for the control of human alpha (8-to 13-Hz) activity. Since that time, a great many new applications have been developed for EEG biofeedback; for example, controlling intractable epileptic seizures or hyperkinesis (Lubar & Bahler, 1976;Lubar & Shouse, 1976. The assessment of learning disabilities and minimal brain damage (John, 1977) and a variety of other applications, ranging from general relaxation to management of specific psychophysiological disorders, involve EEG analysis for biofeedback training.In this discussion, we look at the various methods that have been developed for abstracting from the complex raw EEG-specific information dealing with frequency, amplitude, or patterns of activity, and we examine the methods used for feeding this activity back to the patient or subject in a meaningful and comprehensible form. We will consider zero-crossing methods, analog and digital processing, spectral analysis, and combined methodologies. Behavioral factors, such as the efficacy of analog vs. digital feedback for learning, the problems of artifact rejection, and a general discussion of the state of the art as far as EEG biofeedbackThe research and the development of the instrumentation described in this paper were supported by grants from the Physicians Medical Education and Research Foundation of Knoxville, the Knox Children's Foundation, the Tom's International Foundation, and the Epilepsy Foundation of America. We would like to thank Teri Albanese and Anne Rediehs for their help in the preparation of this manuscript. methodology is concerned will be included.A related type of neural activity that will not be discussed is the use of the evoked potential. Numerous studies by Donchin and Cohen (1967), John (1977), Regan (1972), and many others have shown that the evoked potential (EP) carries a great deal of specific information related to the transm...