THE INFLUENCE OF CARDIAC PHASE ON REACTION-TIME DEPENDING ON HEART PERIOD LENGTH AND ON STIMULUS AND RESPONSE LATERALITY

The aim of this study was twofold: (1) to reinvestigate the question o f cardiac cycle time effect on sensorimotor performance, and (2) to ex amine the dependence of this effect on stimulus and response lateralit y. Thirty-eight right-handed subjects performed a simple visual reacti on time task, where stimuli were presented randomly to the right or to the left of the fixation point, or centrally. Half of the responses w ere given by the right hand, and the other half by the left hand. The stimuli occurred at either 150- or 600-msec delays from the R wave of the electrocardiogram, that is, during the systolic or diastolic part of the cardiac cycle, respectively. For right stimuli and right-hand r esponses, the reaction time was marginally longer for systolic than fo r diastolic stimuli. No such effect emerged for central and left stimu li and for left-hand responding. This result suggested-albeit weakly-t hat the sensorimotor functions of the left cerebral hemisphere might b e influenced to a greater extent by the physiological changes accompan ying cardiac activity than those of the right hemisphere. Additionally , it was shown that in females characterized by long heart periods, th e reaction time was longer for stimuli presented during systole than f or stimuli presented during diastole, but the opposite was true in fem ales with short heart periods. In males, a similar but nonsignificant tendency was found. This result does not contradict the Laceys' (1970) baroreceptor hypothesis. The limitations of this and similar approach es are discussed.