Quantification of electrodermal activity variation across human fingers: Toward a scientific basis of mudras

Context: Fingertips when mechanically stimulated can elicit varied responses in the human body as in Mudras. Each fingertip is considered as a terminal of one of the ten meridian (or energy) channels. Can meridians be quantified? Aims: Electrodermal activity (EDA) of skin is an easy and inexpensive biosignal to acquire and is considered to be a good indicator of psychophysiological state of human health. Although EDA has been studied before, EDA across fingers has never been studied before, and it could be used to prove or disprove the theory of meridian terminals in the fingers. Settings and Design: This study was a randomized, event-based trials. Materials and Methods: A device to measure EDA of ten fingers simultaneously has been developed. Event-based experiments, involving external stimuli given to the participant due to which there may be an onset of skin conductance response (SCR), were conducted on seven voluntary participants. Continuous decomposition analysis is used to decompose data into continuous tonic and phasic activity. Statistical Analysis Used: Several time domain and frequency domain parameters have been extracted from the EDA and compared against different fingers. Results: The number of SCRs and the latency values of SCRs occurring are varying from finger to finger from 1.029 to 3.5 s. Values of SCR amplitudes and average phasic driver and maximum value of phasic activity are also varying which implies different levels of activity in each finger. Conclusions: It was observed that there is a marked difference across fingers in various metrics used to characterize EDA, and it is likely that fingertips indeed represent the terminal of meridian channels.