Cry threshold predicts regulatory disorder in newborn infants

Studied the autonomic regulation of 37 infants with a typical cry threshold and 17 infants with a high cry threshold (typical of problems in nervous system function). Infants with a high cry threshold had a longer latency to cry, a shorter first cry sound, and a shorter overall bout of crying. Spectrum analysis of 2 hours of heart rate variability showed that a high cry threshold was predictive of fewer reliable rhythms and a lower power of the basic 40-min rhythm in heart rate. High cry threshold infants also showed fewer startles and changes in behavioral state. Results suggest a high cry threshold predicts disrupted autonomic regulation and poor coordination among rhythmic systems affecting cardiac activity.