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 upon the spectral distribution of heart rate variability and upon performance on a test of sustained attention. Our findings suggest that activity of the central noradrenergic system influences the distribution of heart rate variability in the ~ 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.