A NUMBER OF investigators in studying continuous recordings of autonomic functioning of humans at rest have reported short-lived bursts of sympathetic-like activity.2,3,5,9,11,12,15-20 These atypical fluctuations, appearing as periodic and aperiodic deviations from the mean trend of the record, are denoted spontaneous autonomic activity or background activity (BA). Johnson9 defines this activity as "fluctuations of autonomic response in the apparent absence of external stimulation" (p 415).Spontaneous autonomic activity has been shown to be a reliable characteristic of the individual over time and across different experimental conditions. There is little or no correlation between BA and absolute levels of physiological functioning, and BA in one system is, in general, not predictive of BA in another.The autonomic functions most extensively studied are heart rate (HR) and skin resistance ( SR). Lacey and Lacey11 devised an arbitrary method of quantifying BA in these two systems, later
BOYLE RH, DYKMAN RA, ACKERMAN PT. Relationships of Resting Autonomic Activity, Motor Impulsivity, and EEG Tracings in Children. Arch Gen Psychiatry. 1965;12(3):314–323. doi:10.1001/archpsyc.1965.01720330088012
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