Spectral Analysis of Sinus Arrhythmia during Mental Loading

Abstract A technique is presented for digitally processing cardiac intervals to produce the low-pass filtered cardiac event sequence (LPFCES), a regularly sampled (in time) band-limited signal, representing in a standard form the information contained in the cardiac intervals. The technique takes into account the physiological mechanisms of information transfer across the peacemaker, and thereby produces a signal that has a physiological counterpart: autonomic activity converging on the sino-atrial node. Sinus arrhythmia (SA) is then defined quantitatively as those harmonic components of the cardiac event sequence which correspond to the signal that modulates that event sequence (i.e., the converging autonomic activity). SA is scored by calculating the average total power (ATP) of the LPFCES, as well as the contribution of changes in average band power (ABP) of various spectral bands to the ATP changes. This scoring technique is shown to give a reliable indication of mental loading (and possibly reserve capacity) in decision-making tasks. Possible mechanisms of reduced SA with mental loading are explored. Additional informationNotes on contributorsB. W. HYNDMAN Present address; Ergonomics Psychology Laboratory, Zuiderzceweg 10, Amsterdam, The Netherlands.