The response of the human newborn to visual movement.
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Previous work in female mice has shown that suckling stimulation is essential for the initiation of male-directed aggression during the immediate postpartum period. The present work examined the importance of this stimulus for the maintenance of aggression during lactation. Surgical excision of nipples (thelectomy) on Postpartum Day 5 accelerates the decline in aggression that ordinarily occurs during the final third of lactation (Postpartum Days 15-21), but does not disrupt the behavior during the middle third of lactation (Postpartum Days 6-12). Thus, both the initiation of aggression during the early postpartum period and the maintenance of the behavior during late lactation are controlled by suckling from young.
By varying the quality and quantity of tactile input that rat dams, between Days 2 and 14 postpartum, received from their pups, we found the following: a) After a 4-hr separation from their litter, mothers continuously display an array of activities, until the onset of nursing, in response to displaced pups and to pups gathered in the nest. b) While the dam hovers over the gathered pups, engaged in an activity such as pup-licking, the young gain access to the dam's ventrum and root for a nipple. c) Pups capable of effective rooting, nipple attachment, and suckling thereby stimulate the dam's immobility (i.e., inhibition of head and limb movements), assumption of the upright crouching posture, and milk ejections. d) Rat dams do not become immobile or crouch in response to pups that are inactive or that are active but incapable of rooting effectively or suckling. e) The likelihood and speed of assuming the quiescent nursing posture, as well as of having milk ejections subsequently, are directly related to the number of effective pups in the nest. We propose that the initiation, maintenance and termination of nursing behavior are related to the spatial and temporal summation of effective ventral somatosensory afferents.
Pregnant Rockland-Swiss (R-S) albino mice consumed significantly more food and water and gained significantly more weight between gestation days 8-17 compared to virgin R-S females maintained in isolation for a comparable period. Postpartum (days 1-10) patterns of ingestion and weight change among thelectomized (nipple-deprived) mouse dams provided with young did not differ significantly from those of virgin animals without young. Sham- and nonoperated dams received suckling stimulation from young and consumed about 100% more food than thelectomized or virgin females (Experiment 1). Pregnancy concurrent with lactation does not increase further the hyperphagic response of female mice. Nipple presence is the principle regulator of postpartum hyperphagia in lactating and simultaneously pregnant-lactating mouse dams (Experiment 2).
This experiment was conducted to determine whether suckling-induced prolactin (PRL) values in chronically food-restricted lactating rats resulted from the inability of their litters to suckle vigorously. Rats were randomly assigned to be fed ad lib (AL) or to be chronically restricted (CR) to 50% of AL before and during pregnancy and lactation. Rats nursed their own litter (own) or a litter of the opposite dietary treatment group (other) for 90-min periods at early or peak lactation. Blood was collected regularly through a catheter implanted several days earlier. Suckling contributed to differences in PRL between AL and CR dams in early lactation as demonstrated by an interaction between dietary treatment and type of litter. However, tests of AL own vs. AL other and CR own vs. CR other were not significant. This is probably because the inattentive behavior of CR dams attenuated the PRL response in this group. At peak lactation, PRL values were related to recovery time from catheter implantation; therefore, determinants of PRL release change over the course of lactation.
To investigate the role of dopaminergic mediation of the positive reinforcing effect of sucrose during development, we tested the effects of the D-1 antagonist, SCH 23390, on the intake of 10% sucrose in 7-, 14-, and 21-day-old rats during independent ingestion (pups lick sucrose from the floor of a beaker) or during continuous intraoral infusion of sucrose. SCH 23390 inhibited intake more in independent ingestion tests than in intraoral catheter tests. At 7 and 14 days this difference was qualitative--SCH 23390 was efficacious in independent ingestion tests, but not in intraoral catheter tests. At 21 days the difference was quantitative--SCH 23390 decreased intake in both tests, but was more potent in independent ingestion tests. SCH 23390 decreased intake during independent ingestion tests without changing latency to eat or time-sampled activity scores at 7 and 14 days, but not at 21 days; thus the inhibition of intake is not accounted for by a generalized motor deficit at 7 and 14 days. Possible explanations for the differential potency include density of reinforcement, pattern of central dopamine metabolism, and interference with the appetitive movements required to maintain contact with the sucrose in the independent ingestion test.
This study tests the proposition that selected behaviors of both mother and infant during feeding are predictors of weight gain during the 1st mth of life. 40 normal mother--neonate pairs were studied, and the target behaviors were examined using an adaptation of the techniques developed by Brown and Bakeman [18]. Aggregate scores of 4 specific maternal and infant behaviors accounted for over 32% of the variance in total weight gain. These findings indicate that the availability of nutrients is not, in itself, a sufficient condition to meet the infant's nutritional needs. Implicit in these findings are the possibilities that infants at risk of failure-to-thrive can be identified, and measures to prevent this syndrome can be introduced.
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The present report describes psychobiological studies of behavior around the time of birth. An adaptive, ecological perspective is presented in which stimulation of the fetus and newborn is purported to instigate adaptive postpartum behavior. Studies describing the perinatal sensory environment are reviewed, with a consideration of emergent sensory function of the fetus. It is asserted that afferent input associated with parturition perturbs the fetus and neonate, producing a general arousal state that facilitates breathing, suckling, and early learning. The view developed herein is that perinatal sensory input induces and canalizes the newborn's behavior, thereby regulating adaptive postpartum function. Deviations in afferent input may alter ontogenetic trajectories and compromise developmental outcome by reducing availability of conditions necessary for adequate postpartum adaptation.
A developmental approach to the study of feeding is proposed that considers social complexity and its biological mediation as core determinants of later ingestive patterns. Evidence is presented for opioid-mediated influences of milk and its major constituents and for nonopioid-mediated channels for contact comfort. Consideration of these factors might help us better understand some of the determinants of human feeding disorders such as bulimia and anorexia nervosa.
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Three neurochemical agents known to arouse ingestion in adult rats were studied in milk-sated rat neonates ingesting fluids away from their dams. All were given intracerebroventricular (ICV) injection. Drinking of both milk and water by 2-day-olds injected with angiotensin II (Ang II) was confirmed. The characteristic adult dipsogenic response, intake of water greater than that of milk, appeared at 8 days. ICV carbachol (Carb), on the other hand, did not elicit drinking before 4 days, despite the fact that these dipsogens (Carb and Ang II) may both affect receptors in the subfornical organ. ICV norepinephrine (NE) increased milk intake beginning at 9 to 10 days, which coincides with the age at which central adrenergic receptors believed to mediate NE's orexigenic effect are appearing in the developing forebrain. NE had no effect on water intake at any age. The effects of all three agents on ingestive behaviors were dose-dependent. These data suggest that the neural systems utilized by Ang II, Carb, and NE are competent for mediation of specific ingestive behaviors before they reach full anatomical and biochemical maturity. Last, NE did not increase milk intake of pups suckling from their dam at any age. The noradrenergic system that is developing in the rat brain during the suckling period appears to be a nascent control of subsequent adult feeding rather than a functioning control of ongoing suckling.
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The nutritive sucking performance of congenitally addicted infants undergoing narcotic withdrawal was used to provide objective measures of adaptive behavior in a series of 50 infants born to mothers addicted either to heroin or methadone. Sucking rates as well as average pressures developed during sucking were significantly reduced for the addicted infants relative to a control group born to normal mothers and a second control group born to toxemic mothers. The subgroup of infants born to methadone-addicted mothers was significantly more depressed with regard to sucking behavior than the infants of heroin-addicted mothers. Furthermore, infants treated with paregoric (an opiate) for symptoms of the narcotic withdrawal syndrome showed significantly less depression of the sucking response than those treated with sedatives such as phenobarbital.
The present study examined the newborn pup's responsiveness to artificial nipples that differed in length and width. In a series of experiments, pups were: exposed to a long (5.0 mm), thin (1.0 mm) nipple or a short (2.0 mm), fat (2.5 mm) nipple and their immediate behavioral responses including oral grasping were recorded and quantified (Experiment 1); preexposed to one artificial nipple and then reexposed to another artificial nipple to determine how early nipple experience affected subsequent responding to the artificial nipple (Experiment 2); videotaped to characterize details of oral grasping and to develop a technique for measuring depth of nipple entry into the pup's mouth (Experiment 3a); provided early nipple experience to see how depth of nipple entry into the pup's mouth changed when pups were reexposed to another artificial nipple (Experiment 3b); and exposed to an artificial nipple to determine how early nipple experience changed the pattern of oral grasping and ingestion of milk from a surrogate nipple (Experiment 4).