Effects of mental stress on cardiac and motor rhythms

To identify whether spontaneous cardiac rhythm and voluntary motor rhythm are modified in parallel or influenced separately when imposing mental stress, we recorded simultaneously the two rhythms during finger tapping as a simple model of rhythmical motion in 10 healthy human subjects (6 males, 4 females each). Each subject performed finger tapping with an arbitrary tapping rhythm. Mental stress was given intermittently three times for 10-15 s at intervals of 40 s during tapping for 150 s. Heart rate (HR) and tapping rate (TR) and their variations (standard deviation; SD) during finger tapping with and without mental stress were compared. HR and TR increased significantly in response to mental stress during tapping. After mental stress was ended, HR returned rapidly to the initial level, but TR remained at a higher level. Moreover, SD of TR, but not SD of HR, during tapping was increased by mental stress. The present results indicate that the cardiac and motor rhythms are influenced simultaneously by mental stress. However, a difference was seen about the sustained effect of mental stress on the two rhythms.