ABSTRACT
It has been argued that a recently developed measure, vagal tone (V), is a significant advancement over other existing methods of assessing the periodic variation in heart rate associated with respiration (respiratory sinus arrhythmia). It has been further suggested that, as a noninvasive measure of vagal nerve efferent activity, V may facilitate the early identification of infants at risk for developmental disabilities. This study addressed the relationship between V and other measures of cardiac activity and behavioral state and the stability of V across repeated measures. Twelve samples of cardiac activity were collected from each of 20 full term infants, 6 samples on each of two consecutive days. V values were derived using a spectral analysis program comparable to Porges' patented MXedit process. Measures of behavioral states were collected by continuous observation. Heart period and heart period variability were highly correlated with V. Variation in V between behavioral states was also detected. Repeated assessments revealed that average V values collected in the same state were not significantly correlated across successive days. This short-term variability both between and within individuals does not support the notion that a single assessment of V can, by itself, be used to identify at-risk infants or predict developmental outcome.
Subject(s)
Arousal/physiology , Heart Rate/physiology , Infant, Newborn/physiology , Vagus Nerve/physiology , Female , Humans , Male , Neurologic Examination , Reference Values , Respiration/physiology , Risk Factors , Sleep Stages/physiology , Wakefulness/physiologyABSTRACT
The vestibular system plays a major role in the expression of early motor behavior. Previous research has cited extensive neural connections between the vestibular apparatus and the motor system. Accordingly, some therapists have implemented programs of supplemental vestibular stimulation to improve motor and cognitive abilities in children with delayed motor development. In the present study a quantifiable regimen of supplemental rotary vestibular stimulation was administered in a cross-over longitudinal design to nonhandicapped and Down syndrome infants. Time constants, considered a measure of habituation in the vestibular system, were derived from postrotary nystagmus. Results indicated that supplemental rotary vestibular stimulation produced no measurable gain in motor ability beyond that evident in control periods. In addition, it was determined that children exhibited greater gains in motor skills in the early phase of the study, regardless of experimental condition. A positive correlation was found between changes in time constant and motor development.
Subject(s)
Down Syndrome/physiopathology , Motor Skills/physiology , Rotation , Vestibule, Labyrinth/physiopathology , Follow-Up Studies , Humans , Infant , Neurologic Examination , Nystagmus, Physiologic/physiologyABSTRACT
Studies on the use of sensory integration therapy with mentally retarded persons were critically reviewed. Experimental design and statistical procedures were found inadequate to support the use of this therapy on an empirical basis. In addition, certain methodological and design problems seriously cloud interpretation of research results on this topic. Alternative explanations of positive outcome as well as equivocal findings among studies appear related, in part, to the conceptual foundation of sensory integration therapy. Recommendations for future directions in research and restraint in application were discussed.
