The weight of the cortical inflow against medullary reflexes as enlightened by spectral analysis of HR and SP waves.

Components of the autonomic drive to the heart were studied in 5 young normals subjected to: 1. sustained lung inflation (SLI) in various postures; 2. mental loading by concentration of attention; 3. face immersion (FI) in cold water under SLI or snorkel breathing, when sitting; 4. superpositions of 1-3 experimental interventions. Recorded were: cardiotachogram (CTG as RR interval) and T-wave amplitude from ECG, ear-lobe photo-plethysmogram, digital impedance rheogram, thermistor pneumogram (PNG). Heart rate (HR) and systolic pressure (SP) data were treated using the Fourier analysis on a M118B microcomputer. Preliminary data-exploration, reported in a previous paper, has verified the capability of the Fourier spectrum to spot in short quasistationary data-series known marks of single interventions and has pointed to the amphotrop nature of SLI and FI maneuvers. Present work approaches the same data from the point of view of the competition between various regulatory menus under combined interventions. The "cortico-cardiac reflex"--HR stabilizing under mental loading versus rest based upon balanced reduction in both respiratory and vasomotor sinus arrhythmia (RSA and VSA, respectively)--appeared now as a middle size actor upon medullary areas; it is overridden, yet not put to silence by the powerful orthostatic reflex; it is comparable (SLI) or major (FI) vis-a-vis of synergic vagal reflexes whose more easily approachable mechanisms could offer it meaningful models. Capacitating this "reflex" in the containment of intricated arrhythmias with extrinsic involvement or in "educating" the benefic vagal prevalence upon the heart should observe these precisions.