David H. Crowell

Arousal level in neonates and preschool children under continuous auditory stimulation

Abstract This study compared the relative effectiveness of four continuously presented auditory stimulus conditions in reducing arousal level in neonates and preschool children. The stimulus conditions were no sound, heartbeats, metronome beats, and lullabies. A low arousal level was defined as a pattern of low heart rate, low general motor activity, stable respiration rate, stable heart rate, minimal crying, and rapid onset of sleep. A comparison of the results produced by no sound vs. any sound confirmed the results previously found by Irwin and his students that prolonged auditory stimulation quiets infants. A comparison of heartbeat vs. any other condition contradicted the recent claims made by Salk that the effectiveness of heartbeat in quieting infants is unsurpassed by that of any other sound.

Daytime sleep stage organization in three-month-old infants

Sleep monitoring at 3 months post term of clinically normal term infants, pre-term infants with no demonstrable pathologic clinical signs, and pre-term and term infants with a history of metabolic disorders show that these infants have EEG sleep stages resembling those seen in adults, as well as the adult pattern of sleep stage organization. The presence of NREM stage organization and stage sequencing suggest that sleep regulatory mechanisms are approaching a level of functional maturity in the human infant at 3 months post term. There is a significant relationship between sleep staging at 3 months post term and mental and motor performance at 12 months post term. In light of this, it is hypothesized that early bioelectric maturation may reflect the development of neural mechanisms which are also the substrate for later cognitive and behavioral functioning. Sleep stage organization at 3 months post term may be utilized as a benchmark of CNS development and for research on the pathophysiology of sleep disorders.

Galvanic Skin Reflex in Newborn Humans

Psychophysiological recordings of reactivity to light and sound and to tactile and olfactory stimulation demonstrate that the galvanic skin reflex is an observable and functional mechanism in the 20- to 67-hour-old newborn human.

A method for detecting change in a time series applied to newborn EEG

Abstract An auto-regression model using a step-wise procedure for estimating the parameters has been developed to test for change in the post-stimulus onset EEG of a single subject. A stationary process is assumed for the pre-stimulus data and if there is no significant change, for the post-stimulus region. Change can be detected at any point in the time series giving a measure of response latency and duration. This analysis was performed utilizing the responses of a human newborn to sensory stimulation to demonstrate the applicability of the model for detecting changes in digitized EEG data and relating these to underlying neurophysiological activity.

Heart rate changes to sudden peripheral stimuli in the human during early infancy

Changes of heart rate following sudden peripheral stimuli were investigated in infants at 2 days and at approximately 6 and 11 weeks of age. The 3 forms of stimulation used were auditory (clicks), tactile (a puff of nitrogen on the abdomen), and olfactory (a whiff of acetic acid). The 2-day-old infants exhibited a monophasic acceleration in heart rate to all of the stimuli. The 11-week-old infants had an initial decelerative component in all of their responses. The 6-week-old infants did not consistently exhibit a decelerative or accelerative change in heart rate. The observed differences in pattern that occurred with age are discussed as a function of physiological maturation, increased experience with peripheral stimulation, or differences in state.

Autoregressive representation of infant EEG for the purpose of hypothesis testing and classification

Abstract Frequency characteristics of infant electroencephalograms are represented by autoregressive coefficients and statistically evaluated with standard multivariate techniques. Autoregressive spectral analysis is presented as a quantified and objective technique for testing hypotheses about infant EEG development and, in combination with maturational level. Discrimination between infant EEG spectra for different age levels is demonstrated and clinically abnormal cases are classified relative to age graded reference groups.

An Adaptive Method for Testing for Change in Digitized Cardiotachometer Data

An adaptive method for detecting change in digitized cardiotachometer recordings has been developed which takes into account the nonstationary statistical structure of the data. The digitized data are smoothed to reduce the variance at high frequencies caused by discontinuities inherent in cardiotachometer output. Based on a first-order autoregression, which has been shown to be appropriate for heart rate data, the adaptive procedure uses estimates of the parameters which are most influenced by the recent observations. Decreasing weight is given to past prestimulus data, and the estimates are updated with each stimulus. A test for change is then applied to the poststimulus regions at each time point, yielding a t statistic. The t 2 s can then be averaged to give a test for change over an interval.

Neonatal habituation to electrotactual stimulation

This study was designed to analyze the effect of varying stimulating conditions on neonatal electrotactual threshold during the first 3 days after birth. Data (N = 40) showed significantly increased thresholds from Day 1 to Day 3 with repetition of stimulation. The Day 3 mean threshold of the total group was significantly higher than the mean threshold of the Day 3 control group (N = 9), which had no prior stimulation. This effect was interpreted as habituation, which has developed as some function of stimulus intensity and intertrial interval. The demonstrated permanent incremental results from electrotactual stimulation were considered as substantial empirical evidence to support the notion of habituation as a learning phenomenon.