Effects of a single cognitive task on power spectra of R-R interval and arterial blood pressure

The present study was designed to examine the effects of a single cognitively demanding task on the R-R interval and systolic blood pressure (BP) power spectra. Ten healthy volunteers were asked to perform an English transcription task for 90 minutes using a word processor, and to read books as a non-task control. The influences of both posture and respiration were controlled in assessing the task effects. Performance of the single cognitive task significantly increased the normalized low-frequency component (% LF) of the BP spectrum following the task, as compared to the non-task control in the sitting position. However, the supine position did not produce the post-task increase in % LF of the BP spectrum. The spectral components of the R-R interval spectrum remained unchanged after the task. These results suggest that the post-task increase in sympathetic activity may be reflected by the BP spectrum under sympathetic predominance in the sitting position.