Earle L. Lipton

Autonomic function in the neonate. II. Physiologic effects of motor restraint.

&NA; Infants are quieter, sleep more, and have lower heart rates when swaddled under the experimental conditions we employed. When swaddled and experimentally stimulated, some infants show no difference and may even manifest greater responses in heart and respiratory rates than when free to move. Five of the 10 infants responded less when swaddled. Overt motor responses alone do not account for heart‐rate responses to stimulation. Swaddling may prove to be a useful tool in the investigation of parameters of the neonatal nervous system functioning by allowing for more stable conditions during testing. Infants differ considerably in many physiologic parameters under these conditions. These differences are currently under investigation.

Individual differences in autonomic responsivity. Problems of measurement.

&NA; Proposed measures of autonomic nervous system functioning within an individual were reviewed. An important factor in the choice of such measures is the recognition that the magnitude response to stimulation is influenced, to a large extent, by the state of the individual prior to stimulation. From the point of view of informational content, there is little difference between the use of the magnitude change score and response level as the basic response datum when used in conjunction with the initial level. Consideration of the concept of the autonomic lability score as well as the mean response score reveals that neither measure adequately corrects nor compensates for the effect of prestimulus level. Several magnitude measures suggested for the comparison of individuals include the slope of the regression of change score on initial level, variability around this line, a measure of discriminability, and a measure of maximal reactivity. The temporal aspects of the autonomic response are discussed and, because of their lack of dependence on prestimulus level, two measures are extracted for each aspect—the mean and variability.

CARDIOVASCULAR EFFECTS OF THERAPY IN CONGENITAL HYPOTHYROIDISM.

Cardiovascular changes have long been known to occur during the early treatment of hypothyroidism. The responsible factors have not been clearly elucidated. In this study heart rate changes in three cretins were studied in a constant-environment laboratory. Within ten days after the initiation of therapy, cardiac rate increased in the three subjects as did cardiac responsivity to exteroceptive stimuli in two of the infants. Transient, potentially serious arrhythmias were also noted during therapy.