Abstract
In the present review, at the outset, some basic issues pertaining to finger photoplethysmography have been reexamined : blood vessel architecture and α-adrenergic sympathetic activity in the finger, recording technique and the perturbing factors, and data reduction methods related to the traditional measures (i.e., blood volume and blood volume pulse). Second, application of the Lambert-Beer's law to finger segment in situ was validated and a new measure, normalized pulse volume (NPV), was derived from the law as a superior alternative to the traditional measures. Third, previous findings, mainly on the blood volume pulse, were revaluated in consideration of the different autonomic regulatory mechanisms during passive vs. active coping tasks. Some unresolved issues which need to be clarified in future studies are discussed.
