CLONIDINE-INDUCED CHANGES IN THE SPECTRAL DISTRIBUTION OF HEART-RATE-VARIABILITY CORRELATE WITH PERFORMANCE ON A TEST OF SUSTAINED ATTENTION

Conventional measures of cardiovascular activity correlate poorly with psychological variables and therefore provide imperfect physiological indices of arousal. We have investigated the effects of clonidine upo n the spectral distribution of heart rate variability and upon perform ance on a test of sustained attention. Our findings suggest that activ ity of he central noradrenergic system influences the distribution of heart rate variability in the approximate to 0.1 Hz range. Furthermore , the finding of a strong correlation between the effects of clonidine upon each of these variables supports the use of spectral analysis of heart rate variability in the study of arousal.