Forearm, chest, and skin vascular changes during simple performance tasks

Momentary changes in vascular variables were examined in four experiments which all induced preparation for an expected stimulus. Response requirements were minimized to permit examination of changes during stimulus presentation unconfounded with overt movement. The hypothesis examined was that vascular changes serve to maximize tissue perfusion at the time of anticipated action. Impedance plethysmographic measures of the chest and forearm were scored both for transit times and amplitude/slope indices. Similar indices were derived from photo-plethysmographic signals from the nail-bed of the thumb. The results suggested that preparatory vascular changes could be divided into an initial expectancy phase started at least 2 or 3 seconds prior to the anticipated events and a specific preparatory phase occurring just prior to and during stimulus presentation. Transit time shortening and maintained vasoconstriction characterized the initial expectancy phase when a finger movement, but not an effortful grip, was the anticipated response. Transit time lengthening and vasodilation generally characterized the specific preparation phase, but are disrupted when a signal inhibiting the response is likely to occur. Decelerative heart rate changes were positively related to the slope of the systolic rise in the chest impedance measure, suggesting that both cardiac and vascular changes may act together. Overall, the results were moderately supportive of the view that the heart and vasculature act together to maximize tissue perfusion at the time of anticipated action.