The paper presents theoretical perspectives on beta explain data and to drive future novel hypotheses. EEG and the concept of hyperarousal in insomnia. However, one must first ask whether it is reasonIn their presentation, Perlis et al. review data from able to separate beta EEG activity from other measa number of studies that have shown convincingly ures, and, if so, how this improves our understanding that patients with psychophysiological insomnia have or treatment of insomnia. Do the data presented in increased high frequency activity in their EEG. These this review support the concept that high frequency data, in combination with other data showing elEEG activity, as a measure of arousal, is a) funevated heart rate, body temperature and metabolic damentally independent of other measures of rate in these patients, result in a clear demonstration physiological arousal and is b) a “better” measure of physiological activation in these patients. The than the others? In the review, Perlis et al. present suggested “perspective model” of CNS two reasons why they believe the beta measure is hyperarousal presented appears innovative and fundamentally different from other measures of logically derived from the reviewed studies. physiological arousal: 1) beta activity is not derived Historically, theories of insomnia have reflected from EMG activity and 2) beta activity is associated the classical mind–body dichotomy. Therefore, with cognitive activity. many believe that physiological activation reflects The first point seems to mainly be a defense that increased cognitive activity (as opposed to causing the EEG beta measure reflects more than just an increased cognitive activity). Perlis et al. have chosen increase in muscle tone (which occurs in the same to further divide this dichotomy by differentiating frequency range as beta and would increase with cortical physiological high frequency activity from physiological arousal as beta does). Unfortunately, all other physiological activity. The strength of any none of the reviewed studies controlled for the such heuristic device lies in its improved ability to effect of increased muscle tone. Could it be that the increases in beta activity were artifacts of increased muscle tone? A study cited, but not reviewed by Perlis et al., found that similar increases in beta ∗ Supported by the Centre de recherche Universite Lavalactivity were observed following walking around Robert-Giffard and Fonds de la recherche en sante du Quebec (FRSQ). † Supported by the Dayton Department of Veterans and during mental math [1]. Even larger increases Affairs Medical Center and Wright State University School of in beta activity were observed while clenching fists Medicine. or gritting teeth. What is the case with insomnia Correspondence should be addressed to: Celyne H. Bastien, patients? EMG activity is typically greater in patients Ph.D. Ecole de psychologie, Pavillon F.A.S., suite 1644, with insomnia. Considering that the effect of muscle Universite Laval, Quebec, Quebec, Canada G1K 7P4. Fax: (418) 656-5152; E-mail: celyne.bastien@psy.ulaval.ca activity in the spectral analysis of EEG in insomnia