An attempt to elicit cardiac orienting and defense responses in the newborn to two types of facial stimulation

Testing detectability, attractivity, hedonic specificity, extractability, and robustness of colostrum odor-Toward an olfactory bioassay for human neonates

Human milk odor is attractive and appetitive for human newborns. Here, we studied behavioral and heart-rate (HR) responses of 2-day-old neonates to the odor of human colostrum. To evaluate detection in two conditions of stimulus delivery, we first presented the odor of total colostrum against water. Second, the hedonic specificity of total colostrum odor was tested against vanilla odor. Third, we delivered only the fresh effluvium of colostrum separated from the colostrum matrix; the stability of this colostrum effluvium was then tested after deep congelation; finally, after sorptive extraction of fresh colostrum headspace, we assessed the activity of colostrum volatiles eluting from the gas chromatograph (GC). Regardless of the stimulus-delivery method, neonates displayed attraction reactions (HR decrease) as well as appetitive oral responses to the odor of total colostrum but not to vanilla odor. The effluvium separated from the fresh colostrum matrix remained appetitive but appeared labile under deep freezing. Finally, volatiles from fresh colostrum effluvium remained behaviorally active after GC elution, although at lower magnitude. In sum, fresh colostrum effluvium and its eluate elicited a consistent increase in newborns' oral activity (relative to water or vanilla), and they induced shallow HR decrease. Newborns' appetitive oral behavior was the most reproducible response criterion to the effluvium of colostrum. In conclusion, a set of unidentified volatile compounds from human colostrum is robust enough after extraction from the original matrix and chromatographic processing to continue eliciting appetitive responses in neonates, thus opening new directions to isolate and assay specific volatile molecules of colostrum.

The secretion of areolar (Montgomery's) glands from lactating women elicits selective, unconditional responses in neonates

BACKGROUND

The communicative meaning of human areolae for newborn infants was examined here in directly exposing 3-day old neonates to the secretion from the areolar glands of Montgomery donated by non related, non familiar lactating women.

METHODOLOGY/PRINCIPAL FINDINGS

The effect of the areolar stimulus on the infants' behavior and autonomic nervous system was compared to that of seven reference stimuli originating either from human or non human mammalian sources, or from an arbitrarily-chosen artificial odorant. The odor of the native areolar secretion intensified more than all other stimuli the infants' inspiratory activity and appetitive oral responses. These responses appeared to develop independently from direct experience with the breast or milk.

CONCLUSION/SIGNIFICANCE

Areolar secretions from lactating women are especially salient to human newborns. Volatile compounds carried in these substrates are thus in a position to play a key role in establishing behavioral and physiological processes pertaining to milk transfer and production, and, hence, to survival and to the early engagement of attachment and bonding.

Developmental constraints on the expression of behavioral and heart-rate orienting responses: II. The role of ambient temperature

The effect of ambient temperature on the expression of behavioral and heart-rate orienting responses to a novel olfactory stimulus was examined in rats 1-18 days of age. There was no effect of ambient temperature on the behavioral orienting responses at any age. Ambient temperature did influence the expression of the heart-rate orienting response and did so differentially as a function of age. The implications of these findings for developmental models of attention and cognition are discussed.

Developmental constraints on the expression of behavioral and heart-rate orienting responses: I. The role of cardiosomatic coupling

The ontogeny of behavioral and heart-rate orienting responses to a novel olfactory stimulus was examined in three experiments. The results of Experiment 1 demonstrated that behavioral responses to the olfactory stimulus were observed as early as Day 1, although heart-rate deceleration in response to the stimulus was not observed until Day 9. In Experiment 2, bradycardia was observed in 6-day-old pups if stimulus-elicited motor activity was reduced with haloperidol. Thus, the developmental asynchrony in the expression of behavioral and heart-rate orienting responses was due, at least in part, to cardiosomatic coupling in the very young animal. The results of Experiment 3 demonstrated that although cardiosomatic coupling interferes with the expression of the heart-rate orienting response very early in development, it has increasingly less impact over the course of the preweaning period.

Cardiac and behavioral responses to rocking stimulations in one- and three-month-old infants

Cardiac and behavioral reactions to lateral rocking stimulations were analysed at two different ages (1 and 3 months) and at two speeds of motion for the younger infants. Sixteen 1- and 3-mo.-old infants received 12 10-sec. trials of four complete cycles of vestibulokinesthetic stimulation (rapid rocking) and another group of 10 1-mo.-olds received one complete cycle in the same time period (slow rocking) provided by a motorized cradle. Stimulations were given when infants were in an alert state. Rapid and slow rocking induced similar cardiac responses in younger infants; these responses varied according to the type of motor reaction observed at stimulus onset. Cardiac acceleration was shown with motor activation and cardiac deceleration with motor quieting. In 3-mo.-olds, cardiac deceleration appeared with both types of motor reaction. A strong link between cardiac and behavioral responses in younger infants may prevent the occurrence of the usual simple cardiac index of orienting (heart-rate deceleration). In older infants, cardiac deceleration to rocking stimulation appeared even when it produced concomitant behavioral arousal. Vestibulokinesthetic stimulation is interpreted as having an important homeostatic effect on the young organism.

Effects of sound frequency on behavioral and cardiac orienting in newborn and five-month-old infants

Alert newborn and 5-month-old infants' responsivity to variations in spectral composition of a rattle sound was examined. Each child received four stimulus conditions: low-, mid-, and high-frequency bandpass-filtered rattles and an unfiltered broadband rattle. Stimuli were played through a single loudspeaker laterally positioned, and head orientation and cardiac responses to sound were recorded. Compared to other stimuli, the low-frequency sound elicited less head turning in both age groups, with this effect exaggerated in younger infants. Head orientation toward the mid-frequency, high-frequency, and broadband stimuli did not differ with age. For all conditions, latency and duration of newborns' head turning was longer than that of 5-month-olds. Newborns responded with cardiac deceleration only on trials when they failed to turn. When head turns occurred, an acceleratory cardiac response was obtained. Five-month-olds responded with reliable cardiac deceleration irrespective of head turning toward the sound. Heart rate change did not vary as a function of frequency at either age, suggesting that all stimuli were equally effective in eliciting the infant's attention.