bluuebunny/crossref_metadata_2025 huggingface dataset:
Canalization of arousal in the preweanling rat: Effects of amphetamine on aggregation with surrogate stimuli
Authors: Campbell Byron A. , Raskin Lisa A.
Published: January 2005

Preweanling rats, 15 days of age, were placed in an unfamiliar cage containing 1 of a variety of surrogate conspecific stimuli. The surrogate stimuli consisted of a rat‐sized aluminum tube covered with soft fluffy synthetic fur, a tanned rat pelt, felt, and an aluminum sheet. The surrogate was either maintained at ambient temperature of heated to body surface temperature (37°C). The 1st experiment revealed that both furriness (length and softness of fur) and temperature of the surrogate stimulus are important determinants of conspecific aggregation (huddling). The 2nd experiment demonstrated that preference for the soft, fluffy surrogate was not mediated by temperature conservation by showing that the same huddling behavior was obtained when ambient temperature was raised to thermoneutrality (33°C). The final experiment demonstrated that amphetamine restricted the range of surrogate stimuli that elicited huddling in the preweanling rat. The finding that amphetamine produces a steeper generalization gradient of approach to surrogate stimuli further confirms our previous hypothesis that amphetamine canalizes arousal toward salient environmental stimuli. These findings have implications for the use of amphetamines to treat hyperkinetic children.
Adjustment of weanling and adolescent rats to a reward condition requiring slow responding
Authors: Chen Jaw‐Sy , Gross Keith , Stanton Mark , Amsel Abram
Published: January 2005

The effects of a schedule of discontinuously negatively correlated reinforcement (DNC), in which only approach responses that take 5 sec or longer are reinforced, were studied in weanling rats that began training at 18 days of age and adolescents that began training at 60 days. Yoked partially reinforced subjects (PRF) received rewards on the same trials as corresponding DNC subjects of the same age, whereas continuously reinforced subjects (CRF) were rewarded on all trials. At the end of DNC training (210 trials), the older but not the younger DNC subjects were running slower than their yoked‐PRF controls. The results are consistent with the development of inhibition and suppression related to the developing brain, particularly the hippocampus.
Receiving severe aggression correlates with fetal gender in pregnant pigtailed monkeys
Authors: Sackett Gene P.
Published: January 2005

Pregnant females were severely bitten in 220 of 2,822 conceptions among pigtail macaques living in harem groups. These pregnancies yielded 58.6% female offspring compared with 48.5% for nonbitten pregnant animals. The fetal gender difference occurred only after midterm, reaching a peak of 70% female fetuses in the 4th gestational month. Fetal gender thus appeared to influence maternal behavior, appearance, or physiology in some way detectable to other monkeys with the consequence of altering risk for receiving severe aggression.
Volume discrimination learning in golden hamsters: Effects of the structure of complex rearing cages
Authors: Thinus‐Blanc Catherine
Published: January 2005

Golden hamsters (Mesocricetus auratus) were reared from birth to adulthood in a spatially diversified situation (EG); their performances were compared with those of other hamsters housed in standard laboratory cages (SG). The task was to discriminate between 2 cubic volumes of different sizes followed by various test situations designed to define the respective parts played by the 3 spatial dimensions during perception. The results show that surfaces of volumes were mainly taken into account by EG subjects whereas width, alone, was used by the SG animals.
Single‐dose tolerance to morphine‐induced analgesic and hypoactive effects in infant rats
Authors: Bardo Michael T. , Hughes Richard A.
Published: January 2005

A single injection of morphine or isotonic saline was administered to rats at either 1, 5, 9, or 13 days of age. At 26–29 days of age, animals were tested for pain responsivity and activity following either morphine (5 mg/kg) or saline. Animals which received morphine at 1 day of age displayed tolerance at 26 days of age, whereas animals which received morphine at either 5, 9, or 13 days of age failed to display tolerance. This age‐dependent change in susceptibility to single‐dose morphine tolerance may involve alterations in opiate receptor ontogeny.
Motor asymmetries in preterm infants: Effects of prematurity and illness
Authors: Fox Nathan , Lewis Michael
Published: January 2005

Two types of motor asymmetry, postural asymmetry and lateral head turning, were assessed in 3 groups of preterm infants, one of which had experienced respiratory distress syndrome (RDS) in the postnatal period. Results reveal that maintenance of a right postural asymmetry is present as early as 34 weeks conceptional age and is not disrupted by postnatal illness. Lateral head turning after midline placement was evident as early as 36 weeks conceptional age but was disrupted by physiologic condition. Infants who had experienced RDS had poor muscle tonus and did not assume the head right position even at 39 weeks conceptional age. These data argue that lateral responding may be affected by illness and that studies of preterm populations must evaluate postnatal medical condition when assessing both the short‐ and long‐term outcomes of lateral asymmetries.
A quantitative analysis of the feeding behavior of suckling rabbits
Authors: Drewett R. F. , Kendrick K. M. , Sanders D. J. , Trew A. M.
Published: January 2005

Three experiments are reported on the feeding behavior of suckling rabbits (“kittens”). In the 1st the latency with which the kittens attached to the nipple, and then left the nipple, was determined. Attachment was very rapid and wholly reliable: on the 80 tests the nipple was seized in every case in under 9 sec, and on 67 of these in less than 3 sec. The kittens also invariably left the nipple within the next minute. If the kittens were 5 or 10 days old speed of attachment was unaffected by the presence or absence of saliva on the nipple, but 15‐ and 20‐day‐old kittens seized the sucked nipples more rapidly than the unsucked nipples. In a 2nd experiment with 12‐day‐old kittens, washing the nipple with solvents did not affect speed of attachment; nor did saliva. The results show that suckling rabbits, in contrast to rat pups, are not heavily dependent on saliva cues. In the 3rd experiment both attachment latency and milk intake were shown to be affected by an internal stimulus, a gastric load of .9% saline, 5 g/25 g body weight: attachment latency was significantly increased and milk intake reduced by 75%.
Effects of early social experience on activity and object investigation in the ferret
Authors: Chivers Susan M. , Einon Dorothy F.
Published: January 2005

Earlier experiments have shown that many of the effects of early social isolation in the rat may be due to deprivation of social play. The isolated ferret, like the isolated rat, is hyperactive; further‐more, its hyperactivity appears to be related to deprivation of social play. However, the relationship between object investigation and social rearing is more complex in the ferret than it is in the rat.
Selective resistance to approach: A precursor to fear responses to an alarm call in great tit nestlings Parus major
Authors: Rydéan Olof O.
Published: January 2005

The reactions of 10‐day‐old great tit nestlings to 3 auditory stimuli were studied. The stimuli, presented on a series of feeding occasions, were (1) the species' “seeet” alarm call, (2) a song strophe of the great tit, and (3) a song strophe of the tree‐creeper (Certhia familiaris). In contrast to earlier findings in studies of older nestlings, these younger nestlings did not respond to the alarm call with cessation of begging. However, a significant differential effect of the alarm call was demonstrated when the conditioning rates for the nestlings' begging response to each of the 3 stimuli were determined. Thus, conditioning was significantly slower to the alarm call than to the other stimuli. The results agree with the general conception that responses to species‐specific calls develop gradually during early ontogenesis. Thus fear responses to the alarm call, such as cessation of begging and “freezing,” which are elicited in newly fledged young, are preceded by weaker aversive tendencies that are not obvious from observations of the nestlings' behavior in nature. It is suggested that the nestlings' exposure to contrasting auditory stimulation–their own begging call and the parental feeding call–constitutes the experiential base for withdrawal responses to the “seeet” call.
Control of sleep‐wake states in the infant rat by features of the mother‐infant relationship
Authors: Hofer Myron A. , Shair Harry
Published: January 2005

A series of experiments in 2 strains of Wistar rats explored which aspects of maternal separation were responsible for the sleep disturbance of the young. Neither their own mother, after mammary duct ligation, nor constant intragastric infusion of nutrient during the day of separation were found to ameliorate significantly the changes in sleep‐wake state organization. However, a periodic nutrient delivery schedule and a formula closely resembling rat milk each ameliorated, and together entirely prevented, the sleep‐wake disturbance. Decreased ambient temperature during separation tended to exaggerate the disturbance and periodic tactile‐vestibular stimulation tended to reduce it. These findings suggest that the infant rat's normal sleep‐wake pattern is maintained by the thythmicity and composition of the milk delivered to it by its mother, although her warmth and behavioral interaction with it may play subsidiary roles. Separation produces its effects by removing these regulating features of the relationship.
Environmental and biologic interactions on behavior: Effects of artificial rearing in rat pups treated with 6‐hydroxydopamine
Authors: Goldenring James R. , Shaywitz Bennett A. , Wool Robert S. , Batter David K. , Anderson George M. , Cohen Donald J.
Published: January 2005

In order to examine the impact of social environment on the development of motor activity and cognitive performance in rat pups treated with 6‐hydroxydopamine (6‐OHDA), we employed artificial rearing techniques pioneered by Hall. In contrast to 6‐OHDA‐treated mother‐reared pups which exhibit an increase in activity during their first postnatal month, 6‐OHDA‐treated artificially reared animals fail to demonstrate this hyperactivity. The absence of hyperactivity in 6‐OHDA‐treated artificially reared pups may reflect the absence of isolation‐induced motor activity at the beginning of the test period. Both mother‐reared and artificially reared 6‐OHDA pups demonstrated impairment in shock escape and shock avoidance, suggesting that these deficits in maze performance were influenced by an inherent biological lesion following 6‐OHDA treatment while motor activity may depend, to a considerable extent, on environmental manipulations.
Effects of chronic crowding stress on midbrain development: Changes in dendritic spine density and morphology in jewel fish optic tectum
Authors: Wesley Burgess J. , Coss Richard G.
Published: January 2005

This study investigates the effects of a biologically relevant stressor, crowding, on the development of neurons in the major teleostean brain area, the optic tectum. Adult jewel fish were reared for approximately 4 years under conditions of moderate density (3.3 liter/fish), or under uncrowded control conditions (25 liter/fish). Quantitative morphometric measures of Golgi‐stained tissue were used to test whether long‐term crowding at moderate density produced developmental deficits lasting beyond the juvenile period. Chronic crowding did not affect body size or gross tectal growth. However, crowding significantly decreased the density of dendritic spine formation on apical dendrites of pyriform interneurons in the basal region of the tectum (stratum album centrale). Additionally, the shapes of spines on this segment of the apical dendrite were altered by crowding: relative frequencies of overall spine length and spine stem length changed significantly. These results are interpreted in the context of cytoarchitectural changes produced by more extreme developmental stressors in previous studies.
Short‐ and long‐term effects of various milk‐delivery contingencies on sucking and nipple attachment in rat pups
Authors: Brake Stephen C. , Sullivan Regina , Jayne Sager D. , Hofer Myron
Published: January 2005

Varied milk delivery contingencies differentially affect sucking in rat pups as measured by jaw‐muscle electromyographic activity. In Experiment I we found that 11–13‐day‐old pups sucked more frequently when receiving tiny intermittent pulses of milk than when receiving no milk, and continued to suck at a high rate for at least 30 min after cessation of milk delivery. In subsequent experiments we found that pups 13–18 days of age engaged in more frequent sucking if receiving milk continuosly rather than intermittently, and that this increased rate of sucking persisted for at least 24 hr after cessation of milk delivery. Pups given experience with continuous milk delivery from 14 to 18 days of age also spent significantly more time attached to the nipple at 19 days of age than did pups in control groups. It was concluded that experience with different milk delivery schedules can affect subsequent sucking and nipple attachment behavior.
“Conservations” with a chimpanzee
Authors: Muncer Steven J.
Published: January 2005

Two chimpanzees (Pan tryglodytes), Fanny and Jane, were presented with liquid and number conservation problems. One chimpanzee, Jane, was successful in solving both sets of problems in that she was not distracted by irrelevant transformations, being influenced only by changes in quantity. Her success appeared to be based on the ability to make inferences rather than on simple perceptual judgement of the final comparison. The results are compared and contrasted with those of Premack, in G. Woodruff, D. Premack, and K. Kennel [(1978). Conservation of liquid and solid quantity by the chimpanzee. Science, 202:99–994] and J. Mehler and T. G. Bever [(1967). Cognitive capacity of very young children. Science, 158:141–142; (1968). Quantification, conservation and nativism. Science, 162:979–981], and it is suggested that there may be a similarity of conservation development between chimpanzees and man.
Periadolescence: Age‐dependent behavior and psychopharmacological responsivity in rats
Authors: Spear Linda Patia , Brake Stephen C.
Published: January 2005

The behavior and psychopharmacological sensitivity of periadolescent rats are examined in this review. Periadolescent rats are hyperactive and engage in more conspecific play behavior than younger or older rats. When compared with other‐aged rats, periadolescents exhibit enhanced performance in simple active‐avoidance learning tasks, but perform poorly in more complex appetitive and avoidance learning tasks in which increases in locomotor activity do not improve performance, perhaps as a result of age‐specific alterations in selective attention or stimulus processing. Such behavioral “anomalies” of periadolescent animals observed in traditional laboratory situations may be in some way adaptive when considered in the context of the animals' natural habitat. In terms of psychopharmacological responsiveness, periadolescent rats, when compared with younger or older animals, are less sensitive to catecholaminergic agonists but are more responsive to the catecholaminergic antagonist haloperidol. This pattern of psychopharmacological sensitivity suggests that the catecholaminergic systems may be temporarily hyposensitive during the periadolescent period. Evidence is presented that a negative feed‐back system in the form of dopamine autoreceptors may become functionally mature in mesolimbic brain regions during the periadolescent period. The possibility is presented that maturation of these self‐inhibitory autoreceptors might result in a temporary decrease in the efficacy of mesolimbic dopamine projections, perhaps contributing to the psychopharmacological and behavioral characteristics of periadolescent animals. In support of this suggestion, evidence is reviewed indicating that the behavior of adult animals with lesions of the ventral tegmental area, a region containing cell bodies from which these mesolimbic dopaminergic projections originate, resembles that of periadolescent rats.
The influence of siblings on the development of sexual preferences of male zebra finches
Authors: Kruijt J. P. , Ten Cate C. J. , Meeuwissen G. B.
Published: January 2005

Broods of young zebra finches were either raised by their own species or cross‐fostered by Bengalese finches. Both were isolated visually from other birds at the age of 2 months. Sexual preferences of males, were examined at maturity, in a choice between 1 zebra finch female and 1 Bengalese finch female, by measuring the number of song strophes directed at each. Males raised by their own species sang exclusively for the zebra finch female. Cross‐fostered males raised without siblings or with only 1 sibling sang exclusively for the Bengalese finch female. A large number of cross‐fostered males raised with 2–4 siblings showed at least 5% singing for the zebra finch female, and a small number did so predominantly. It is concluded the under the conditions of these experiments, the development of sexual preferences of zebra finch males is affected by both parental and sibling influences. It is possible that the earlier evidence for a predisposition to respond to conspecifics put forward by Immelmann could be explained by hitherto uncontrolled differences in experience.
Alleviation of infantile amnesia in rats by internal and external contextual cues
Authors: Richardson Rick , Riccio David C. , Axiotis Renee
Published: January 2005

A previous study [Richardson, R., Riccio, D. C., and Jonke, T. (1983). Alleviation of infantile amenesia in rats by means of a pharmacological contextual state. Devel. Psychobiol., 16: 511–518] found that ontogenetic forgetting (“infantile amnesia”) in rats was attenuated by a “contextual matching” manipulation: Subjects trained in a distinct pharmacological state and tested in that state retained learned fear better than saline controls. To determine whether improved retention could be obtained with salient but nonpharmacological contexts, two experiments were conducted employing fear conditioning in preweanling rats. In Experiment 1, an internal context (illness induced by lithium chloride) present at training and testing reduced infantile forgetting. In experiment 2, matching an exteroceptive context (home nest shavings) at training and testing was also found to be sufficient to alleviate infantile amnesia. In both experiments, retention was not improved in controls exposed to the context at training only or testing only, indicating that the contextual effect is not on acquisition or retrieval processes per se. These findings provide indirect support for views that emphasize the role of contextual cues in retrieval (Spear, 1978). In addition, they indicate that contextual matching is not limited to a state dependent drug, but may include a wide range of “distinctive” stimuli.
Behavioral interactions of postweaning male and female rats with a complex environment
Authors: Juraska Janice M. , Meyer Monica
Published: January 2005

Rats reared from weaning in a complex environment with other rats and numerous objects display sex differences in several brain areas, yet there is little systematic information on the types of interactions that rats have within complex environments or whether there are sex differences in these interactions. Therefore, male and female rats were observed in the complex environment over a 15–30‐day period in three separate replications that included same‐sex and mixed sex groups of rats. The rats spent considerably more time interacting with the objects than in social interactions in all replication, and the types of interactions varied little over the length of the study. A few sex differences appeared, such as in play fighting, but these differences were small and not consistent across replications. Male and female rats interacted with the environment in a very similar manner.
Divergent effects of early hydrocortisone treatment on behavioral and brain development in meadow and pine voles
Authors: Prohazka Donna , Novak Melinda A. , Meyer Jerrold S.
Published: January 2005

Developmental effects of a single hydrocortisone (HC) injection (80 μg/g on day 2 postnatal) were compared in two closely related species, meadow voles (Microtus pennsylvanicus) and pine voles (M. pinetorum). Effects of hormone administration were assessed in terms of the development of swimming behavior (head/nose position and front paw movement), alterations in social interactions (spatial location with respect to a stimulus animal), and by changes in somatic and brain growth. Although adult patterns of swimming behavior were found to be quantitatively different in meadow and pine voles, normal maturation in both species involved a progressive elevation of head/nose position along with a gradual inhibition of front paw movement. Compared with saline controls, HC‐treated meadow voles showed an accelerated attainment of their adult pattern, whereas hormone‐treated pine voles displayed a retardation in their swimming development. HC administration similarly led to increased body weights in developing meadow voles but decreased body weights in young pine voles. There was a tendency for hormone‐treated meadow voles to spend more time near a stimulus animal than their control counterparts, whereas the opposite was observed for pine voles. In both species, the HC group displayed decreased cerebral and cerebellar weights in adulthood, whereas other organs were generally unaffected by hormone administration. Neurochemical analyses revealed no treatment effects or treatment by species interactions with respect to cerebral DNA levels. On the other hand, treated meadow voles but not pine voles showed an elevated concentration of sulfatide, a myelin‐related lipid. These results are the first to demonstrate divergent behavioral and neurochemical effects of early glucocorticoid administration in closely related species studied under the same conditions. Furthermore, in accordance with earlier experiments on rats, swimming behavior was shown to be a useful measure for assessing changes in neuromuscular maturation.
Olfactory‐guided orientation in neonatal rats is enhanced by a conditioned change in behavioral state
Authors: Sullivan Regina M. , Hofer Myron A. , Brake Stephen C.
Published: January 2005

In Experiment 1, 3–6‐day‐old rats were simultaneously exposed to an unfamiliar odor which they will normally avoid (orange extract) and the odor of maternal saliva, or to either orange alone or saliva alone. One hour later, in a two‐odor choice test, those pups which were simultaneously exposed to orange and saliva exhibited an enhanced orientation to the orange odor. In Experiment 2, orange odor was presented while pups were exposed to the odor of saliva, or while they received one of two types of tactile stimulation (stroking or tailpinching). Pups in control groups were first presented with saliva or tactile stimulation and then the orange odor. Pups that had received any of the three simulataneous exposure treatments subsequently exhibited an enhanced orientation toward the orange odor, but not the pups in the control groups. The results suggest that the tendency of neonates to avoid a novel odor can be reversed by pairing that odor with events that elicit significant increases in behavioral activity. The possibility that this phenomenon reflects a classical conditioning process is discussed.
The golden‐mantled ground squirrel (Spermophilus lateralis) as a model for the effects of environmental enrichment in solitary animals
Authors: Renner Michael J. , Rosenzweig Mark R.
Published: January 2005

It has been proposed that the brain effects induced by laboratory environmental enrichment may be a product of the social stimulation inherent in the standard enriched environment. This experiment was conducted in order to study the suitability of the golden‐mantled ground squirrel Spermophilus lateralis (a solitary‐living species) for studies attempting to dissociate social factors from other effects in brain and behavioral effects of environmental enrichment. Juvenile Spermophilus lateralis, born in the laboratory of mothers wild‐caught while pregnant, were assigned singly to individual enriched conditions (I‐EC) or impoverished (IC) conditions at 55–62 days (an age at which wild individuals would disperse from the natal burrow and live alone). After 30 days, the subjects were videotaped in two 10‐min opportunities for exploration; following this, they were sacrificed and their brains dissected. Multiple indications of isolation stress were observed, including unusual difficulty in handling, stereotyped pacing behavior, and escape behaviors in the exploration arena. Comparisons between I‐EC and IC showed no differences in whole‐brain weight or weights of several brain regions. These results indicate that S. lateralis is not suitable for this type of study; in addition, this species' reported nonsociality is questioned, based on these subjects' reactions to isolation housing and field observations of social interactions in this species.
Behavioral states of premature infants: Implications for neural and behavioral development
Authors: Davis Diane Holditch , Thoman Evelyn B.
Published: January 2005

Nine premature and 28 full‐term infants were observed in their homes for 7 hr when they were 2, 3, 4, and 5 weeks post‐term, and the sleeping and waking states displayed by these infants were compared. For these comparisons, the observation day was divided into two mutually exclusive contexts: times when the baby was alone and times when the baby was with the mother. The premature infants spent more time alone (mean of 5.4 hr a day) than the full‐terms (4.6 hr).

Over the total 7‐hr day, the premature infants spent more time in alert, nonalert waking activity, and sleep‐wake transition than the full‐terms, and they spent less time in drowse and total sleep. These results clearly indicate that, at the same post‐term ages, the sleep‐wake states of premature infants differ markedly from those of full‐terms. Four states showed significant Group × Context interactions indicating that state differences between premature and full‐term infants were also a function of the context in which the infants were observed. For example, the prematures exhibited more fuss or cry and more drowse when alone; whereas the full‐terms exhibited more of these states when with their mothers. This finding of context‐related differences between prematures and full‐terms has implications for the conflicting reports in the literature, as heretofore the states of prematures and full‐terms have been compared from observations made in a single situation.

The results indicate that prematures exhibit significant commonality in their neurobehavioral development through the early post‐term period despite heterogeneity among them in their exposure to prenatal, perinatal, and early postnatal stresses.
Preweanling behavioral development in spontaneously hypertensive, borderline hypertensive, and wistar‐kyoto normotensive rats
Authors: Cierpial Mark A. , McCarty Richard
Published: January 2005

Preweanling physical and behavioral development was studied in spontaneously hypertensive (SHR), borderline hypertensive (BHR), and Wistar‐Kyoto normotensive (WKY) rat pups. Measures of physical development included body weight, onset of various morphological landmarks, and speed of surface righting. Behavioral tests assessed locomotor development, exploratory behavior, and cliff avoidance in pups of the 3 groups. On all measures employed, SHR pups exhibited a delay in physical maturation compared to age‐matched BHR and WKY pups. Results from the locomotor development test revealed that young WKY pups (ages 1–7 days) spent more time locomoting than SHR pups, with BHR times being intermediate. In contrast, older SHR pups (ages 17–30 days) displayed greater activity in an exploratory maze than WKY pups, with BHR values again intermediate. Finally, SHR pups were more behaviorally reactive in the cliff avoidance task compared to BHR and WKY pups. These group differences may be useful in understanding the development of genetic hypertension and may serve as early behavioral markers of a predisposition to cardiovascular disease.
Regulation of nursing in chimpanzees
Authors: Dienske Herman , Van Vreeswijk Willem
Published: January 2005

The regulation of nursing was studied in captive chimpanzees from birth to 6 months of age. It was asked whether regulation was predictable or timing was irregular. A search for unimodal frequency distributions resulted in a distinction among nursing bouts, nursing episodes (bouts with brief interruptions) and nursing pauses. The frequency distributions of these types were either normal with very large standard deviations or exponential (i.e., randomly terminated). This implies a very irregular timing. Longer nursing episodes were followed by somewhat longer pauses; pauses with daytime sleep (that were relatively long) were followed by longer nursing. However, these regulatory effects were only slight. Most of this loose regulation of nursing was due to the infant, as the mothers did not put the infant on the breast and usually were permissive. Comparisons with humans suggest a similarly loose organization as well as frequent feeding in societies that provide relatively unlimited access to the breast. The regular 4‐hr, meal‐like schedule in industrial countries seems mainly to be due to human mothers and their advisors.
Maternal dietary NaCl intake influences weanling rats' salt preferences without affecting taste nerve responsiveness
Authors: Bird Edythe , Contreras Robert J.
Published: January 2005

The present study examined the relationship between maternal dietary NaCl intake during the period from conception through weaning and weanling rats' elective consumption of salt; the study asked whether or not changes in offsprings' salt intake was mediated by altered taste responsiveness. The subjects were the 21‐day‐old offspring of 24 adult female rats fed diets containing. 08% (low), 1% (mid), or 4% (high) NaCl from conception through weaning. Maternal dietary salt levels influenced offsprings' salt intake. In long‐term food choice tests, the mid and high salt rats ate more salted food and had higher salt preferences than the low salt animals; in long‐term solution choice tests, the mid and high salt rats drank more saline and less water and had higher saline preferences than the low salt rats. Nevertheless, the group differences in salt preference were not due to changes in taste responsiveness. There were no differences between the groups in saline preferences in short‐term tests or in the amplitudes of chorda tympani nerve responses to concentration series of several salts. The implications of these data for understanding the physiological basis for group differences in salt preference are discussed.
The development of the crying state during early infancy
Authors: Hopkins Brian , Von Wulfften Palthe Titia
Published: January 2005

The development of the crying state was studied in 14 infants from 3 to 18 weeks in two situations: the infant alone and in interaction with the mother. A major transformation occurred in the crying state after 3 months, with the appearance of what is termed interrupted fussing, which consists of rapid alternations between fuss sounds and cooing vocalizations. This change was only found in the alone situation. The functional implications of this finding are discussed within the contexts of motor development and the behavioral state concept.
Suppression of adult copulatory behaviors following LiCl‐induced aversive contingencies in juvenile male rats
Authors: Koch Paul C. , Peters Ronald H.
Published: January 2005

Sexually immature juvenile male rats received an injection of .3 M (20 ml/kg) lithium chloride (LiCl) during each of 8–10 pairings (spaced at 2–3‐day intervals) with an estrous female. Approximately seven weeks later, these males displayed fewer copulatory behaviors in pairings with estrous females than saline control rats. Noncontingent .3 M LiCl injections administered to juvenile males did not affect adult copulatory behaviors. Males that were either group or individually housed during the retention interval displayed comparable suppression, which suggests that copulatory suppression does not represent a generalized aversion to social interactions with another animal. Males housed during the retention interval in an environment that contained the odors of estrous females also displayed suppression comparable to that of males housed in the absence of such odors. This suggests that the associations that mediate copulatory suppression are not elicited solely by the odor cues of estrous females. These data demonstrate that LiCl‐induced aversive contingencies in juvenile male rats subsequently suppress adult copulatory behaviors.
Preweaning stimulation with urinary chemosignals and age of puberty in female mice
Authors: Drickamer Lee C.
Published: January 2005

Six experiments were conducted to assess the effects of preweaning stimulation with urinary chemosignals from four different sources on the age of sexual maturation in young female mice. The urinary chemosignals tested were those in male urine, urine from females in estrus, urine from pregnant or lactating females, and urine from females housed in groups. The split‐litter technique was used for assignig mice to particular treatments. When treatments were applied during the period from 2 to 11 days postpartum, none of the chemosignals exerted any detectable influence on the age of first vaginal estrus. All 4 chemosignal treatments were effective in altering the age of puberty when treatment was applied daily from Days 12 to 21 postpatrtum. For urine from males and urine from estrous females, 3 days of treatment during the last 10 days prior to weaning at 21 days of age were sufficient to produce an acceleration of puberty. For urine from pregnant or lactating females, 5 days of treatment just prior to weaning were necessary to produce an acceleration of sexual development. For urine from grouped females, delays in puberty were produced only when the treatment lasted for 7 of the last 10 days prior to weaning. These findings suggest that the preweaning stimulus environment of young female mice may be important for their later sexual development. Further, use of the split‐litter technique permitted the determination that variation in the age of puberty was smaller within than between litters; inheritance and/or maternal influences are clearly important factors affecting the age of sexual maturation.
The effect of nonnutritive sucking on heart rate in preterm infants
Authors: Woodson R. , Hamilton C.
Published: January 2005

A laboratory and a field experiment used within‐subject designs to test the hypothesis that nonnutritive sucking (NNS) reduces heart rate (HR) in preterm infants. Infants in Experiment A were provided a standard pacifier nipple for 30 min under strictly controlled conditions. In the field Experiment B, nursing staff provided infants with a standard pacifier during alternate intervals in a sequence of four interfeed intervals spanning 12 hr. NNS significantly reduced average HR in each experiment. Given the strongly positive relationship between HR and energy expenditure, these results suggest that NNS reduces energy expenditure in preterm infants. Such an effect, in turn, could help to explain how the opportunity to engage in NNS enhances growth in preterms.
Social specificity: Interaction with own species is necessary to foster species‐specific maternal preference in ducklings
Authors: Lickliter Robert , Gottlieb Gilbert
Published: January 2005

Previous studies have shown that if domestic mallard ducklings are allowed social interaction with broodmates after their initial exposure to a stuffed mallard (Anas platyrhynchos) hen, they later show a visual preference for the familiar mallard over an unfamiliar redhead (Aythya americana) hen. Birds kept in social isolation do not make htis difficult discrimination. In the present study, we examined whether this social enhancement of imprintability to a natural maternal model is merely the result of social stimulation in its most general sense of if its effects are specific to social interaction with conspecifics. 24‐hr‐old domestic mallard ducklings were allowed to follow a stuffed mallard hen for 30 min (training). This experience resulted in visual preference for the familiar mallard hen over the unfamiliar redhead hen in simultaneous choices tests at 48 hr and 72 after hatching only if the birds were allowed social experience with a group of same‐age undomesticarted mallard hatchlings. No visual preference for the familiar mallard hen was found if the ducklins were permitted social experience with a group of same‐age (Gallus domesticus) hatchlings or muscovy (Cairina moschata) duclings. Thus, it appears that for duclins to show a visually imprinted preference for a natural maternal model, they must be allowed social interaction with broodmates of their own species. Social rearing with other precocial bird hatchlings, even other duclings, is without apparent effect. These results provide further evidence of the importance of nonobvious experiental factors in the development of species‐typical behavior. They also suggest that in the evolution of the species‐specific learning underlying early species identification, natural selection has operated on the entire (organism‐environment) developmental manifold and not merely on genetic, or organisimic aspects of that system.
Evidence for a maternal effect on infant hand‐use preferences
Authors: Harkins Debra A. , Michel George F.
Published: January 2005

Left‐handed offspring occur more frequently when one or both parents are left‐handed. Among parental pairs with discordant handedness, left‐handed mothers have more left‐handed offspring than do left‐handed fathers. No previous study has looked for this maternal effect in the hand‐use preferences of infants. Handedness of 42 infants (21 females) 6–13 months of age (M = 10 months) was assessed by a reliable and valid procedure that provides hand‐use preference scores separately for reaching and unimanual manipulation of objects. Equal numbers of age‐matched male and female infants were formed into three groups representing different patterns of parental handedness: neither parent lefthanded, father left‐handed, mother left‐handed. Infants of left‐handed mothers showed more left hand‐use than infants of left‐handed fathers or infants of right‐handed parents. Indeed, 64% of infants with left‐handed mothers had significant left hand‐use preference scores whereas none of the infants in the other groups had significant left hand‐use preference scores. Possible mechanisms for this maternal effect on infant hand‐use preferences are discussed.
Enhancement of passive avoidance learning through small doses of intra‐amygdaloid physostigmine in the young rat. Its relation to the development of acetylcholinesterase
Authors: Dumery Vincent , Derer Paul , Blozovski Denise
Published: January 2005

Passive avoidance learning was studied in young rats 7‐20 days old, in control conditions and after bilateral injections of physostigmine into the lateral amygdaloid nucleus. Acquisition in controls was possible from postnatal Day 8 on, progressed markedly after Day 11, and nearly reached maturity by Day 20. Physostigmine differentially altered acquisition depending on the dose: facilitation with low doses, no effect with moderate doses, and impairment with high doses. Enhanced learning through small doses of physostigmine was observed at all ages from Day 8 on, and was greater with 0.2 μg than with 0.1 μg. Maturation of the cholinergic innervation of the amygdaloid region was also studied between Days 9‐20 using acetylcholine‐esterase histochemistry. The results suggest that passive avoidance learning is dependent on amygdaloid cholinergic mechanisms early in life. In addition, very immature cholonergic systems, which are known to be uninfluenced by anticholinesterases.
Long‐term effects of early mothering behavior on responsiveness to the environment in vervet monkeys
Authors: Fairbanks L. A. , McGuire M. T.
Published: January 2005

The long‐term effect of early mothering style on juvenile responsiveness to the external environment was studied in vervet monkeys living in two naturally composed, undisturbed social groups. Mothering behavior for 35 mother‐infant dyads was analyzed by principal components analysis which revealed two independent dimensions: protectiveness and rejection. Protectiveness was characterized by high levels of approach, making contact, restraint, and inspection from mother to infant, and rejection was associated with high levels of rejection, breaking contact, and leaving. When observed as yearlings and 2‐year‐olds, juveniles who had had more protective early mothering showed less interest in the external environment, as measured by the percentage of time they spent looking outside the home enclosure. They also took longer to enter a completely novel environment compared to juveniles who had had less protective mothers. Maternal rejection was not significantly associated with looking out or with latency to enter the novel environment. These results were independent of the effects of age, sex, and dominance rank on behavior.
Prestimulation effects on blink and cardiac reflexes of 15‐month human infants
Authors: Balaban Marie T. , Anthony Bruno J. , Graham Frances K.
Published: January 2005

Reduction of reflex startle by brief changes in prestimulation is a robust phenomenon in adults of several species. Although the phenomenon does not require structures above midbrain, it has a long and uneven developmental course. This study of human infants assessed prestimulus effects at 15 months, within a period which has failed, in past work, to show the usual inhibitory modulation. Magnitude and onset latency of the startle blink and concurrent changes in heart rate were measured under four conditions: 2 single‐stimulus conditions, 25‐msec, 84‐dB, 1000‐Hz tone or 50‐msec, 109‐dB white noise; 2 paired‐stimulus conditions, noise bursts preceded by tone at lead times of 125 msec or 225 msec. Compared to noise‐alone, paired conditions elicited insignificant increases in blink size, significant shortening of blink onset latency, and significant attenuation of heart rate responses. The findings add to growing evidence of a dissociation between modulating effects on blink magnitude and latency and of a dissociation between modulating effects on somatic and autonomic reflexes.
Aggressive behaviors in adult rats deprived of playfighting experience as juveniles
Authors: Potegal Michael , Einon Dorothy
Published: January 2005

Matched litter mates were reared in one of three conditions: in pairs or in isolation with or without one hour of daily playfighting experience from 20 to 50 days of age. The rats were then regrouped within condition so that they lived with identically reared cagemates for a month. This regrouping eliminated the transient effects of isolation such as increased fearfulness. When tested as adults, there was no effect of early rearing condition on the probability of intraspecific aggression or muricide, although isolation‐reared rats were less likely to retrieve the mice. However, isolation rearing reduced the latency to initiate shock‐induced defensive aggression and increased both its frequency and intensity. Isolated animals which had been given daily playfighting during development did not show the effects of early social deprivation. The mechanisms through which playfighting experience shapes later defensive behavior remain to be determined.
Sensory processing in the term and preterm infant: Use of reflex modification procedures
Authors: Anday Endla K. , Cohen Michelle E. , Kelley Nancy E. , Hoffman Howard S.
Published: January 2005

The present study uses the glabellar reflex and reflex modification procedures to assess acoustic and tactile sensory processing capabilities in the human neonate. Fourteen term infants and 28 clinically stable preterm infants were given identical test paradigms. Augmentation testing consisted of a 16 V dc tap presented simultaneously with a 90 dB SPL tone; inhibition testing consisted of a 16 V tap preceded 900 msec. by an identical tap. All 14 term infants showed augmentation with 8 of 14 at p < 0.05 level and eleven of 14 showed significant inhibition at the 900 msec intertap interval. However, only 12 of 28 preterm infants demonstrated significant augmentation and none showed reliable inhibition. These data indicate that areas of the central nervous system that process sensory stimuli are not fully developed at the time of birth even in the term infant. Further, the neural system for augmentation and inhibition may be independent of each other.
Anterior and posterior, but not cheek, intraoral canulation procedures elevate serum corticosterone levels in neonatal rat pups
Authors: Spear Linda Patia , Specht Steven M. , Kirstein Cheryl L. , Kuhn Cynthia M.
Published: January 2005

Implantation of intraoral cannulas is a procedure that has been typically assumed to be relatively unstressful in neonatal rat pups. To test this assumption, endocrine responses to such implantations were compared with those of other standard procedures. In Experiment 1, corticosterone and growth hormone (GH) levels were assessed in 4‐day‐old rat pups placed in an incubator for 15 or 60 min following either: no treatment, subcutaneous (sc) injection of 0.9% NaCl, anterior or posterior intraoral cannulation, ice anesthesia or ether anesthesia. Corticosterone levels were elevated relative to nontreated controls 15 min after all treatments except sc injection. These levels remained elevated after 60 min in both cannulation groups and the ice anesthesia group. In Experiment 2, the ability of ether anesthesia to reduce the hormonal response to the cannulation procedures was assessed in addition to examining the hormonal response to intraoral cannulations through the cheek in 4‐day‐old rat pups. Ether did not attenuate the corticosterone response to either anterior or posterior cannulations. Pups subjected to the cheek cannulation procedure did not exhibit any significant alterations in serum corticosterone levels when compared with nontreated control pups. GH levels were found to differentiate less among the various procedures than corticosterone levels, with GH levels generally being low in all groups, including nontreated control animals. These data suggest that cheek placement is less stressful than anterior and posterior placements and may provide a viable alternative in studies necessitating the implantation of a cannula into the buccal cavity during the early postnatal period.
Changes in sensitivity to the odor of androstenone during adolescence
Authors: Dorries Kathleen M. , Schmidt Hilary J. , Beauchamp Gary K. , Wysocki Charles J.
Published: January 2005

While it has been reported that most, if not all, very young children are able to detect the odor of 5α‐androst‐16‐en‐3‐one (androstenone), approximately 40–50% of human adults cannot detect its odor. The present study focused on changes in sensitivity to androstenone was determined in 247 subjects aged 6 to 50. There was a significant increase in the number of males anosmic to androstenone between 9–14 and 15–20 years of age, and a significant increase in threshold with age among males able to detect the odor. We infer that a smaller percentage of females than males becomes anosmic to the odor of androstenone during development, and those able to detect it apparently show a decrease in threshold with age. No age‐related changes were observed in tests of pyridine or d, l, ‐β‐phenylethylmethylethyl‐carbinol (PEMEC).