bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between heart rate indices of the orienting response and birth weight in normal full‐term newborns
Authors: Stamps Leighton E.
Published: January 2005

The results of this study indicate that birth weight in normal term infants is related to changes in heart rate in response to auditory stimulation. Only infants above the median in birth weight responded to stimulus onset and offset. They exhibited a change in response to onset from a heart rate acceleration (defensive response) on the 1st trial to heart rate deceleration (orienting response) on later trials. The response to stimulus offset was a deceleration. Those infants below the median in birth weight showed no significant responses to onset or offset.
The effects of litter size on the expressivity of the jaundice genotype in gunn rats
Authors: Graham Dee L. , Hasenstab Laura L. , Kinney Lois , Kuntz Judith Ann
Published: January 2005

In 2 studies Gunn rats carrying 2 recessive alleles for jaundice (jj) were compared with their heterozygous littermates (Jj) under varied litter size (4 vs 12 pups) and handling conditions. Handling did not produce long‐term effects. Litter size interacted with Genotype to increase the differential response of jj rats by 21, 23, and 50 days of age. A decrease in survival rates and weight gain was found in Jj and especially jj rats from large litters. For jj rats only, being reared in a large litter increased the severity of ataxia. Jaundiced rats from large litters showed less rearing and tended to enter fewer squares than those from small litters whereas Jj littermates showed an equivalent amount of rearing and number of squares entered in large as compared to small litter sizes. Differences between Jj and jj rats in frequency of pivoting were greater in those from large litters than in those from small litters.
Gender differences in open‐field behavior as a function of age
Authors: Masur Jandira , Schutz Maria Teresa , Boerngen Roseli
Published: January 2005

Male and female rats were observed in an open field at 30, 45, 60, 90, and 120 days of age. Thirty‐ and 45‐day‐old rats of both genders presented similar defecation, ambulation, and rearing scores. From 60 days on the male rats showed higher defecation scores and less ambulation and rearing than did the females. The gender difference observed in the adult rats reflected a decrease of defecation by femeles and a decrease of ambulation and rearing by males when compared to the earlier ages.
The “infantilization” of a cichlid fish
Authors: Shaw Evelyn , Innes Karen
Published: January 2005

This paper reports a rather remarkable phenomenon, which we have termed “infantilization.” Young acaras, 7 to 17 days postspawning age and normally freely swimming, will resume their nesting phase when placed with foster parents' brooding embryos or wrigglers. The foster parents do not eat these alien young when the young assume a behavior pattern similar to that of their own brood, namely, nest‐bound and quiescent.
Dietary and metabolic effects on rhesus social behavior: Protein and protein‐calorie malnutrition
Authors: Chamove A. S.
Published: January 2005

Forty‐seven monkeys were fed 1 of 8 diets between the ages of 1 and 7 months containing full‐, half‐, or quarter‐strength protein or protein and calories using either casein or soy protein. While on the diet, malnourished infants were inactive both socially and nonsocially. When returned to a normal diet, previously malnourished subjects were more agonistic towards familiar peers but more friendly and less agonistic when paired with unfamiliar monkeys. The data suggest that short periods of early severe malnutrition may protect the individual against adverse social conditions (e.g., isolation) and delay the development of normal social skills.
The ontogenesis of sleep states, thermogenesis, and thermoregulation in the virginia opossum
Authors: Walker James M. , Berger Ralph J.
Published: January 2005

Polygraphic recordings of sleep and wakefulness were obtained over 4‐hr periods from infant opossums, aged 48–79 days, while they were in the mothers' pouches. Concurrent body temperature measurements were obtained from littermates held at ambient temperatures of 25 and 30°C. The ontogenesis of sleep was similar to that of placental mammals: quiet sleep increased from 13% sleep time at 48 days to 55% at 79 days; conversely, active sleep decreased from 87% to 45%, respectively. The amplitude of the electroencephalogram (EEG) during quiet sleep increased with age and quiet sleep could be categorized as slow wave sleep at 75 days. Active sleep could be identified as rapid eye movement sleep at the same age. Temperature measurements revealed that thermogenesis appeared at approximately 55 days and the 1st signs of thermoregulation were apparent at 67 days. Near‐adult thermoregulatory capabilities were present by 79 days. Increases in percent time spent in quiet sleep corresponded with increases in percent adult thermogenesis. The appearance of slow wave EEG activity coincided with the onset of thermoregulatory capabilities. We suggest that lowered metabolism associated with slow wave sleep is adaptive in offsetting the increased energy demands of thermogenesis.
Ontogeny of behavioral sensitivity to glycine in the chick embryo
Authors: Reitzel J. , Oppenheim R. W.
Published: January 2005

Strychnine (STR), glycine (GLY), and γ‐aminobutyric acid (GABA) were injected intravenously into 6‐ and 7‐day chick embryos and subsequent effects upon spontaneous motility were observed. In 7‐day embryos STR alone increased motility and when injected simultaneously with GLY antagonized the GLY‐induced motility decrements; STR did not antagonize GABA‐induced motility decrements. In 6‐day embryos STR injected alone had no effect on motility, but did antagonize motility decrements induced by the simultaneous injection of GLY; again STR did not antagonize GABA‐induced motility decrements.
Retention under changed‐reward conditions of persistence learned by infant rats
Authors: Chen Jaw‐Sy , Amsel Abram
Published: January 2005

Two experiments were performed to determine whether or not persistence acquired under reinforcement conditions of infancy can be retained and transferred to adult reinforcing conditions. In Experiment I 2 groups of rats 14–15 days of age were trained in a runway under a partial (PRF) or continuous (CRF) schedule of milk‐suckling reinforcement. A 3rd group was trained under continuous nonreinforcement (NRF) conditions. The PRF and CRF groups acquired the approach response about equally, and the NRF showed a very small increase in speed. In immediate extinction, the PRF group was more resistant to extinction than its CRF counterpart. For the NRF group “extinction” produced a continuation of the low‐level “acquisition” performance. Experiment II showed that persistence acquired at 14–15 days with milk‐suckling reinforcement can be sustained through a 2‐week retention period including a phase of CRF food‐pellet reward.
Passive avoidance learning in the young rat
Authors: Blozovski Denise , Cudennec Annie
Published: January 2005

A step‐through locomotor passive avoidance task is described requiring the suppression of a spontaneous escape reaction from a cool toward a warm compartment in order to avoid an electric shock delivered in the warm side. We observed no learning of this task at 9 days of age, a very low but significant level of acquisition at 11 days, a slow but progressive improvement of avoidance from the 13th until the 17th day when the adult capacity was achieved, and a marked increase in the rate between 17–20 days.
Periodicity in the behavior of grain beetle larvae
Authors: Sheimann I. M. , Khutzian S. S. , Ignatovitch G. S.
Published: January 2005

Larvae of the grain beetle (Tenebrio molitor) were trained in a T‐maze at different stages of the same instar. The larvae's aptitude for learning changed depending on the stage of their development: poor in the middle of the intermoulting period, but much improved upon approaching the next moult and during the 1st day thereafter. Such regularity seems to be related to general laws of cyclic development of the insect larvae as governed by the hormones of metamorphosis.
Avoidance learning under delayed shock termination in prenatally x‐irradiated rats
Authors: Tamaki Yoshitaka , Inouye Minoru
Published: January 2005

Groups of MP1 male albino rats were exposed to x‐irradiation of 200 rad on Day 17 of gestation. Irradiated and control rats were trained in a shuttlebox with either immediate or .5‐sec delayed termination of both the electric shock (US) and the conditioned stimulus (CS) on escape trials. An avoidance response always produced prompt CS termination. Irradiated rats showed a higher degree of avoidance behavior than controls and, under the delay condition, tended to run rapidly in the CS‐US interval.
Perinatal methylmercury intoxication: Behavioral effects in rats
Authors: Schalock R. L. , Brown W. J. , Kark R. A. P. , Menon N. K.
Published: January 2005

Sprague‐Dawley rats were subjected to perinatal (4th gestational day until Postnatal Day 21) methylmercury intoxication to determine the long‐term behavioral effect of the mercury poisoning. Experimental and control animals were evaluated at 110–140 days of age. Compared to controls, the methylmercury animals demonstrated significant behavioral deficits characterized by hypoactivity and by reduced appetitive, escape, and avoidance learning.
Development of wing‐flapping and flight in normal and flap‐deprived domestic chicks
Authors: Provine Robert R.
Published: January 2005

Lateral flight evoked by dropping appeared 7–9 days after hatching. Drop‐evoked bilaterally symmetrical wing extension and slow, low‐amplitude wing‐flapping were present by Day 1. Flapping rate measured using strobophotography increased up to approximately 13 days. Normal wing‐flapping rates and lateral flight distances were achieved by chicks whose wings were immobilized with elastic bandages from Day 1 until immediately before testing at 13 days, indicating that wing movement is not necessary for the postnatal development of basic wing‐flapping and flight. The ratio of wing area to body weight, a morphological index of wing‐lift efficiency, rapidly increased up to 13 days and slowly declined through 49 days. The peaking of this ratio at 13 days corresponds to the age at which lateral flight is well established and wing‐flapping rate is its maximum. Thus, the development of wing morphology, wing‐flapping rate, and flight are strongly and positively correlated.
The effect of early visual experience on spatial maze learning in rats
Authors: Tees Richard C. , Midgley Glenda , Nesbit John C.
Published: January 2005

In the 1st of 2 experiments on spatial ability, groups of sighted and blind, light‐reared (LR) and dark‐reared (DR) rats were tested on a series of (Hebb‐Williams) maze problems and their reversals under appetitive and aversive reinforcement conditions. Significant effects due to early rearing conditions, vision at time of testing, and problem were found. Dark‐reared rats learned the problems whose solution depended on nonvisual cues more slowly than LR animals. Blindness at time of testing had a significantly adverse effect on the performance of LR and DR rats on all problems, but a significantly greater effect in the DR animals. In a 2nd experiment DR rats were also found to perform less effectively than LR rats on a 17‐arm radial maze throughout a 36‐day period during which variations in the task were introduced. The results reveal the impact of early visual experience on the development of the ability to acquire spatial concepts.
Age and brightness discrimination learning by C57BL/6J mice
Authors: Warpen J. M.
Published: January 2005

Groups of 20–34 C577BL/6J mice, aged 75, 225, 375, and 525 days, learned a brightness discrimination for water. The error scores of the 75‐ and 525‐day groups were almost identical, and both made significantly more errors than the 225‐day‐old mice. Both immature and older mice appear to be deficient in learning ability compared to young adults.
Olfactory development in gerbil pups
Authors: Cornwell‐Jones Catherine A. , Azar Leila M.
Published: January 2005

In a 2‐choice situation, Mongolian gerbil pups show a preference for home‐cage bedding odor that appears during the 2nd postnatal week and is consistently high between Days 8 and 14. Pups show responses to certain nonanimal odors as early as Day 4, indicating that the motor capacity to orient to odors precedes the emergence of nest odor preference. Increases in pups' nest odor preference appear to parallel increases in the frequency of maternal nest‐building, an activity which can eject pups from the nest. This coincidence suggests that olfaction helps displaced pups to return to their nests.
Cortical depth changes in enriched and isolated mice
Authors: Cummins R. A. , Livesey P. J. , Bell J. A.
Published: January 2005

The occipital cortical depth was determined in laboratory mice at both 14 and 20 days of age and after various periods of postweaning exposure to enrichment or isolation. The depth was found to be maximal at 20 days of age. It declined thereafter, irrespective of environment, but the isolate cortical depth decreased faster than the enriched. The postweaning depth of the occipital cortex appears to be determined by an inevitable age‐related decrease whose rate of decline may be attenuated by sensory stimulation. The postweaning cortical depth may reflect the extent of cortical neuronal development and associated metabolic activity.
Intense rapid eye movements during active sleep: An index of neurobehavioral instability
Authors: Becker Patricia T. , Thoman Evelyn B.
Published: January 2005

Rapid Eye Movement (REM) Storms, intense REM bursts during Active Sleep (or REM Sleep), were investigated as an expression of the neural mechanisms involved in overall control of the sleep and waking states. Twenty normal full‐term infants were observed in their homes for a 7‐hr period when they were 2, 3, 4, and 5 weeks old. Sleep and waking states, and co‐occurring behaviors of the mother, were recorded at 10‐sec intervals throughout the observation day. During each 10‐sec epoch of Active Sleep a rating was made of the infant's rapid eye movements, as follows: No REM, Light REMs, Moderate REMs, or intense REMs (REM Storms).

REM Storm rates were related to a measure of stability in the distribution of the sleep and wake states over weeks, derived separately for time the infant was alone and for time the infant was with its mother. REM Storm rates were negatively correlated with state stability in each of these contexts. The results demonstrated a commonality between the incidence of REM Storms and overall sleep‐wake state regulation.
Studies of social learning in norway rats: A brief review
Authors: Galef Bennett G.
Published: January 2005

I review below some of the research on social learning in Norway rats carried out in my laboratory from 1969 to 1980. Two independent lines of research are discussed; both involve analysis in the laboratory of possible instances of social learning first described by observers of free‐living, wild rats. The 1st research program analyzes social interactions important in the transmission of learned food preferences from adult rats to their young. The 2nd examines the possibility that the habit of diving in shallow water for food is socially transmitted from 1 rat to another.
Sexual imprinting in male japanese quail: The effects of castration at hatching
Authors: Hutchison R. E. , Bateson Patrick
Published: January 2005

This study investigated whether gonadal hormones are required for sexual imprinting in male Japanese quail during the period of exposure to the imprinting stimulus. Brown males were either castrated or laparotomized on the day of hatching. Between Days 10 and 30 of age castrated males (N = 15) and intact laparotomized males (N = 10) were exposed individually to white females. A 2nd group of intact laparotomized males (N = 13) were exposed to brown females. When adult (Day 54), 7 of the castrated males were treated with testosterone propionate (TP): the remaining 8 castrated males and intact groups received saline. All males were given choices between novel white and novel brown females starting on Day 62. The TP‐treated castrated males behaved like intact white‐exposed males, preferring to approach and copulate with white females significantly more readily than did intact brown‐exposed males. The untreated castrated males showed no sexual behavior. The results indicate that gonadal hormones are not required during the period of exposure to an imprinting stimulus in male Japanese quail.
Reproductive functioning in the prenatally stressed female rat
Authors: Beckhardt Stacey , Ward Ingeborg L.
Published: January 2005

The reproductive behavior and physiology of female offspring of rats stressed during pregnancy were assessed. Mothers were restrained and placed under bright, hot lights from Day 14 through 21 of gestation. This treatment, which is known to disrupt the sexual behavior of male offspring, did not alter reproductive functioning in the female offspring. The females showed evidence of normal cyclicity, sexual behavior, pregnancy, parturition, pup survival, and maternal behavior when tested beginning at 70 or at 140 days of age.
The effects of early rearing environments on maternal behavior in adult female rats
Authors: Moretto Denise , Paclik Lida , Fleming Alison
Published: January 2005

The purpose of this study was to determine the effect of presence of siblings and exposure to colony cues during early life on the onset of maternal behavior at 20 and 75 days of life, and on subsequent emotional behavior in juvenile and adult female rats. Different groups of animals were reared either (1) with a large number or a small number of siblings (sibling factor), or (2) in the colony room or in a room apart from other mothers with pups (colony factor). Animals were tested for latency (in days) to show maternal behavior at either 20 or 75 days of age, and for emotional behavior (using the open field apparatus) at either 20–40 or 80–100 days of age. Exposure to colony sensory cues significantly reduced latencies for pup retrieval and nestbuilding in adults, but not in juveniles. Exposure to a large number of siblings reduced the latencies, in both adults and juveniles, to nest build; in juveniles, to lie over 75% of the litter; and in adults, to adopt a nursing posture. Consistent with prior research, juveniles had longer latencies than adults for a number of pup‐directed behaviors including: latency to become maternal, latency to retrieve pups, latency to adopt a lactating posture, latency to lick/genital lick, and latency to nest‐build. In the emotionality tests, the young animals scored as less emotional than the adults, an effect which was further exaggerated by early colony exposure. Overall results indicated that manipulation of early rearing environments does have a significant positive effect on later responses to young pups by both juvenile and adult female rats.
Ontogenetic change in the analysis of sound frequency in the infant rat
Authors: Hyson Richard L. , Rudy Jerry W.
Published: January 2005

Previous research has shown that there is an ontogenetic shift in the spatial code of sound frequency in the cochlea and central auditory nuclei. During ontogenesis, a given area of the basilar membrane or central auditory nuclei is maximally stimulated by sounds of progressively higher frequencies. Here, a similar ontogenetic shift in the rat's “perception” of sound frequency is reported. Animals were trained with a tone (CS) paired with footshock (US) and generalization of their conditioned response (CR) to different frequencies was assessed either 0.5 or 72 hr later. When 15‐day‐old animals were trained with an 8‐kHz tone and tested 0.5 hr later, greater suppression of activity (CR) was evoked by the 8‐kHz tone than by either a 12‐kHz or a 6‐kHz tone. When tested 72 hr after training, however, greater suppression of activity was evoked by a 12‐kHz tone than by the 8‐kHz training stimulus or by a 24‐kHz tone. This shift in the peak of the generalization gradient could not be accounted for by changes in unconditioned responses to the test stimuli. Additionally, the observed shift in the generalization gradient was age‐dependent. It was not observed when pups were trained at 18 days old and tested 72 hr later. The implications of these data for studies of the ontogenesis of learning and memory are discussed.
Effects of litter age, litter size, and ambient temperature on the milk ejection reflex in lactating rats
Authors: Jans James E. , Woodside Barbara
Published: January 2005

Under a number of circumstances the duration of mother‐young contact in the rat can be drastically reduced while pup growth is maintained. We investigated the possibility that under some of these conditions the timing of milk delivery is changed. We assessed the time of onset and pattern of milk delivery over a nest bout in litters of two different ages (Day 4 or Day 10) and three different sizes (4, 8, or 12 pups). Ambient temperature fluctuated over the course of the study and was found to correlate significantly with the latency to the first milk ejection (ME). Specifically, the warmer the ambient temperature, the quicker the first ME occurred. Durations between successive MEs correlated with ambient temperature in a similar fashion. Analysis of covariance revealed that the onset of the first ME occurred earlier in Day 10 litters than in Day 4 litters, but litter size had no effect. Durations between successive MEs were not affected by either litter age or litter size. These data indicate one possible mechanism by which adequate milk delivery can be maintained despite some reduction in motheryoung contact.
Ontogenesis of trace conditioning in young rats: Dissociation of associative and memory processes
Authors: Moye Thomas B. , Rudy Jerry W.
Published: January 2005

Hooded rats from 15 to 30 days of age were trained with a Pavlovian trace fear conditioning procedure in order to study the development of their capacity to learn associations between events separated in time. For both the auditory and visual systems, the associative processes necessary to learn about temporally contiguous events emerged earlier during ontogenesis than the processes necessary to integrate events separated in time. Furthermore, the ability of the rats to integrate events separated by increasingly long intervals continued to improve as they got older. We suggest that the emergence of the capacity to integrate temporally separate events reflects the maturation of memory processes that retain representations of stimulus events over time, and that these processes continue to mature for a considerable period after the basic associative processes have become functional.
Salt preference in the preweaning rat
Authors: Bernstein Ilene L. , Courtney Lynn
Published: January 2005

Salt (NaCl) preference of 5–20‐day‐old rats was examined using a method which elicits independent ingestive responses. Rats were placed in a warm, moist incubator on toweling which was saturated with water or test solutions. Active mouthing responses were seen which were directed toward the towel soaked with solution and weight gain in a 25‐min test was taken as an index of ingestion. At most ages pups preferred hypertonic saline solutions to water and at 10 days of age rats appeared particularly insensitive to the aversiveness of concentrated (4–8%) NaCl solutions. In contrast to the 10‐, 15‐, and 20‐day‐old rats, the 5‐day‐old rats never preferred NaCl solutions to water and avoided them at concentrations which older rats preferred. This pattern of NaCl preference cannot easily be explained in terms of the known increases in sensitivity of the rat's taste system to NaCl stimulation with age. Ingestion of NH4Cl solutions was also examined and at 10 days of age significant preference for concentrated NH4Cl solutions was evident which contrasts markedly with the behavior of older pups and adult rats when presented with NH4Cl solutions. The relationship between the present findings and available electrophysiological data from the chorda tympani and nucleus of the solitary tract are discussed.
Response of sparrows to songs of deaf and isolation‐reared males: Further evidence for innate auditory templates
Authors: Searcy William A. , Marler Peter
Published: January 2005

Adult song sparrows (Melospiza melodia) were tested for response to songs of conspecific males that had been reared in acoustic isolation or deafened early in life. Territorial males responded more aggressively to playback of songs of isolated males than to songs of deafened males but did not discriminate between songs of deafened males and heterospecific songs. Captive females showed an identical pattern when their response was measured in terms of the number and intensity of courtship displays evoked by song. The results support the auditory template theory of song development in demonstrating that species‐identifying features are present in songs of isolates and in showing that males unable to hear their own song production do not incorporate these species‐identifying features into their songs.
Experience during suckling alters later spatial learning
Authors: Cramer Catherine P. , Pfister John P. , Haig Kristine A.
Published: January 2005

These experiments explore the role of preweaning experience in learning during the juvenile period. Pups that had been reared with many nipples available reached criterion on an 8‐arm radial maze in a few trials; conversely, pups reared with only a few nipples required 3 times the number of trials to reach criterion (Experiment 1). Pups that had been reared with relatively few nipples available rarely nipple‐shifted, while those that had been reared with a particularly high density of nipples shifted more frequently (Expt 2). A rearing procedure was devised that allowed precise experimental control of all phases of the suckling experience (Expt 3). Allowing or preventing a single behavior, nipple‐shifting, while holding all other variables constant, was sufficient to affect acquisition of the maze task. In Experiment 4, the specificity of the early experience for later tasks was explored using a variety of nonspatial, lever‐pressing operants. Rearing condition did not affect acquisition of a lever‐pressing operant or of a visual discrimination task. However, pups reared with a high density of nipples responded at higher rates to a variable interval schedule and were more resistant to extinction. The possibility that strategy, rather than learning ability, was affected by rearing condition was assessed using a 2‐arm maze task that was structured to present an optimal strategy of either win‐shift or win‐stay (Expt 5). The ease with which rats acquired the win‐stay task was unaffected by rearing condition; all groups performed at about chance levels. However, pups reared with many nipples more readily acquired the win‐shift task.
Effects of age, sex, and psychological disturbance on immunoglobulin levels in the squirrel monkey
Authors: Coe Christopher L. , Cassayre Perla , Levine Seymour , Rosenberg Leon T.
Published: January 2005

The following research assessed the influence of developmental, hormonal, and psychological factors on immunoglobulin and complement protein levels in the squirrel monkey. A cross‐sectional life span study established that the developmental pattern of immunoglobulins and complement proteins was similar to that observed in humans. IgG and IgM levels rose progressively with age, while the complement system was mature at birth. In contrast to humans, this species showed a significant sex difference in IgG levels with higher levels in males during both infancy and adulthood. Males also showed a greater antibody response to viral challenge than did females, and evaluation of gonadectomized subjects suggested that the sex difference in antibody production was testosterone‐dependent. The effect of acute and sustained psychological disturbance on IgG levels was also evaluated in infant monkeys. Repeated, brief separations from the mother did not alter IgG levels, but IgG levels were suppressed after a 7‐day removal from the mother. Therefore, despite the general view that immunoglobulin levels are relatively stable, these studies have established that immunoglobulin levels can be strongly influenced by hormonal and experiential factors in the squirrel monkey.
Behavioral effects of developmental lead exposure in rhesus monkeys
Authors: Levin Edward D. , Schneider Mary L. , Ferguson Sherry A. , Schantz Susan L. , Bowman Robert E.
Published: January 2005

Postnatal lead exposure has been found to cause long‐term learning and memory deficits in monkeys. Pulse‐chronic exposure, consisting of acute high‐level exposure followed by chronic lower‐level exposure, has been particularly effective in causing these impairments. We investigated possible antecedents of lead‐induced cognitive dysfunction by evaluating the behavioral effects of pulse‐chronic lead exposure in rhesus monkeys during the first 6 months of postnatal life. Blood lead pulse‐chronic lead exposure in rhesus monkeys during the first 6 months of postnatal life. Blood lead concentrations in the monkeys reached a peak of 55.8±7.8 ug/dl during week 5 after birth and then averaged between 33.1 and 42.9 ug/dl during the rest of the first 6 months after birth. Zinc protoporphyrin levels were increased by lead exposure, but hematocrits were unaffected. Significant lead‐related effects were detected on a visual exploration test and a neonatal behavioral assessment battery. Lead‐treated monkeys exhibited decreased looking behavior on the visual exploration test and decereased muscle tonus and increased arousal or agitation on the behaiovral assesment battery. No effectw were seen on a Piagetian object permanence task and ton toxic effects on health on growth were detected. In addition to providing indices of behavioral dysfunction during postnatal lead exposure, performance on these early behavioral tests may predict later lead‐induced cognitive dysfunctionn.
Development of salt aversion in the Fischer‐344 rat
Authors: Bernstein Ilene L.
Published: January 2005

Adult Fischer‐344 (F‐344) rats fail to prefer NaCl solutions of any concentration to water and, in fact, avoid NaCl at solution concentrations which other strains of rats reliably prefer. In contrast, immature rats of a number of strains have been reported to express an elevated salt preference relative to adults. The present studies examine the development of the F‐344 rat's salt aversion by testing salt preference in the preweaning (Day 10) and weanling (Days 20–24) F‐344 rat. At Day 10, F‐344 rats ingested significantly more 1% and 2% NaCl solutions than water during “towel testing” and their preference was comparable to that displayed by other strains at this age. By the time of normal weaning (Days 20–24) significant avoidance of NaCl solutions in the isotonic range was displayed by F‐344 rats, and their preference was strikingly different from other rat strains. This was evident in a 24‐hr 2‐bottle preference test as well as a 25 min “towel test.” Since NaCl preference of F‐344 rats is comparable to other rat strains at Day 10 but dramatically different by Day 20, a change must occur during this time which reverses the hedonic value of NaCl stimulation. Identification of factors responsible for this reversal may provide insight into the causes both of the F‐344 rat's dislike of salt and the immature rats elevated salt preference.
Alarm call responsivity of mallard ducklings: VIII. Interaction between developmental history and behavioral context
Authors: Blaich Charles F. , Miller David B. , Hicinbothom Gloria
Published: January 2005

Mallard ducklings (Anas platyrhynchos) inhibit their vocal behavior upon hearing the maternal alarm call of their species. The present study assesses the interaction of the ducklings' experiential history with the environment in which they are tested. If ducklings are reared and tested to the alarm call in small social groups, they respond by dramatically inhibiting their vocalizations. If, however, socially reared ducklings are tested to the alarm call individually in an open field, responsiveness drops precipitously. In addition, individually reared ducklings respond at a far greater level to the alarm call when tested individually, not in groups. Thus, there is an interaction between the rearing history and the testing environment such that the same rearing history leads to different behavioral outcomes depending on the context in which the ducklings are observed. This demonstrates the importance of behavioral context, in addition to developmental history, as one of the determinants of behavior.
Lack of stability in neonatal adrenocortical reactivity because of rapid habituation of the adrenocortical response
Authors: Gunnar Megan R. , Connors Joan , Isensee Jill
Published: January 2005

The purpose of the study was to examine the stability of the adrenocortical response to stimulatin in the human neonate. Forty‐nine healthy newborns were examined twice responding to discharge examinations performed on two consecutive days. The dependent measures were salivary and plasma cortisol and behavioral state. Little evidence of stability was obtained. Instead, the results showeds significant elevations in cortisol only in response to the first discharge examination. No significant elevation in cortisol was noted to the second discharge examination although the newborns continued to exhibit behavioral distress. Time since delivery was not a significant factor in producing these results. The findings are discussed with regard to neonatal coping processes and the importance of novelty in regulating increases in adrenocortical activity.
The performance of human infants on a measure of frontal cortex function, the delayed response task
Authors: Diamond Adele , Doar Bertha
Published: January 2005

The Delayed Response task is the best‐established marker of frontal lobe function in nonhuman primates. This article reports the developmental progression of human infants on that task. It is proposed that maturation of prefrontal cortex may make possible these age‐related improvements in Delayed Response performance. This would suggest the importance of prefrontal cortex functioning very early in life.

Twelve infants (6 male, 6 female) were tested longitudinally every two weeks from 6–12 months of age. Another 36 infants (18 male, 18 female) were tested only once: 12 each at 8, 10, and 12 months. We predicted that infants would improve on Delayed Response over these ages because infants' performance on AB improves during this time, and Delayed Response is very similar to AB. The AB task, devised by Piaget, is used to study congnitive development in infants. The ages over which AB performance improves are well established. In both AB and Delayed Response, the subject watches as the experimenter hides a desired object in one of two identical wells. After a brief delay, the subject is allowed to reach. In AB, the object is hidden in the same well on subsequent trials until the subject reaches to the correct well; then side of hiding is reversed and the procedure repeated. In Delayed Response, side of hiding is varied randomly over trials. In the present study of Delayed Response each testing session consisted of 16 trials (eight to the right, eight to the left). We found: (1) the developmental progression for Delayed Response is almost identical to that for AB. (2) Infants of 7 1/2–9 months fail Delayed Response under the same conditions and in the same ways as do monkeys with lesions of dorsolateral prefrontal cortex. It is therefore suggested that AB and Delayed Response require the same congnitive abilities, and that improved performance on these tasks provides an index of maturation of frontal cortex function.
Relative importance of experience, social facilitation, and availability of milk in weaning of rats
Authors: Lichtman Aron H. , Cramer Catherine P.
Published: January 2005

These studies investigated the role that social facilitation, availability of the dam, and milk play in the maintenance of suckling behavior. Beginning at Day 20, rat pups suckling experiences were restricted to testing with an anesthetized dam. In the first experiment, nipple attachment was abandoned by about Day 25 in rats that were testd alone with an anesthetized dam for 1 hr per day. When tested in groups of four, nipple attachment was maintained until about Day 27. Increasing exposure to an anesthetized dam to 2 hr per day prolonged nipple attachment about another 4 days. In the second experiment, pups were given either one or two daily 1‐hr attachment tests and tested with either an anesthetized dam or an anesthetized dam in which the milk letdown reflex was reinstated. Both increasing the daily exposure to an anesthetized dam and reinstating milk letdown significantly prolonged suckling. Pups given two daily exposures to an anesthetized, milk‐laden dam attached until about Day 47, long past the normal age of weaning.
Fetal male masculinization in control and prenatally stressed rats
Authors: Lephart E. D. , Fleming D. E. , Rhees R. W.
Published: January 2005

The present experiments were designed to test the hypothesis that males in utero masculinize the development of other males. This effect was examined during fetal development in males from control and prenatally stressed rats. A code identified the number of cervical‐flanking males between the target male and the cervical end of the uterus. The male parameters morphology (anogenital distance) and body, adrenal, and testis weights were recorded on the eighteenth and twentieth gestational days and categorized by the cervical‐flanking male classificantion. At Day 18, control fetuses with two cervical‐flanking males in utero displayed significantly greater anogenital distance values than did males with no cervical‐flanking male. At Day 20, control fetuses with two cervical‐flanking males had testicular weights significantly greater than those of fetuses with one or zero cervical positioned male. Prenatal stress markedly impaired male fetal development, at gestational Days 18 and 20 while suppressing the cervical‐flanking male effect. These results confirm and extend previous data that indicate: (a) prenatal stress disrupts normal fetal development, resulting in long‐term changes; and (b) androgens via a cervical‐flanking blood‐flow mechanism influence littermate morphology and sexual development during the prenatal period. Our findings also demonstrate that a general masculinizing effect could not be made across the measured male parameters since the effect of males positioned at the cervical‐flanking region in utero appears to be dependent upon maternal sources of variance. Finally, androgens prenatally have an apparent positive interaction with somatic growth.
Physical and physiological correlates of behavioral inhibition
Authors: Rosenberg Allison A. , Kagan Jerome
Published: January 2005

Previous investigations have suggested that the temperamental quality of inhibition is related to the threshold of reactivity to unfamiliar events within certain limbic structures. In earlier work, children in three independent samples who had been selected to be inhibited were more likely to have blue than brown eyes, whereas uninhibited childern were more likely to have brown eyes.

The present study, which selected two‐year‐old children on the basis of eye color (blue or brown) rather than behavior, found a significant association between blue eyes and behavioral inhibition, and between brown eyes and an uninhibited style. Although the inhibited childern were more likely to have a high and stable heart rate than were the uninhibited children, there was no relation between eye color and these cardiac measures. Several interpretations of the association between these temperamental categories and iris pigmentation are proposed.
Quantitative analysis of eye movements during REM‐sleep in developing rats
Authors: Van Someren E. J. W. , Mirmiran M. , Bos N. P. A. , Lamur A. , Kumar A. , Molenaar P. C. M.
Published: January 2005

Development of eye movements in REM‐sleep was studied in rats during the second and third week of postnatal life. An increased frequency of eye movements was found after eye opening, which was due only to changes in burst activity. Since pups reared in constant darkness showed an increase in eye movement activity similar to that of those exposed to diurnal light‐dark alterations, the change seems to be part of an endogenous developmental timetable rather than due to an increase of visual stimulation by eye opening.
Effects of morphine and naloxone on play‐rewarded spatial discrimination in juvenile rats
Authors: Normansell Larry , Panksepp Jaak
Published: January 2005

Juvenile rats were trained on a spatial discrimination task (T‐maze) rewarded by the opportunity to play with a conspecific. Neither morphine (MS; 1 mg/kg) nor naloxone (NX; 1 mg/kg) administration affected choice or running time during the acquisition of the task, even though in the goal box. MS‐treated animals played more than and NX‐treated animals less than vehicle‐treated controls. Thus, brain opioid systems seem to influence the expression of play without affecting the apparent appetitive strength of play motivation. When play reward was no longer available in the goal box. Animals that continued to be treated with MS were more resistant to extinction than either vehicle‐or NX‐treated animals. They continued to complete the task more often and in less time than the controls. NX‐treated rats, on the other hand, extinguished faster than controls. The evidence supports the conclusion that opioid systems are important in the maintenance of social habits.
Effects of prenatal alcohol exposure on rat pups' ability to elicit retrieval behavior from dams
Authors: Ness James W. , Franchina Joseph J.
Published: January 2005

Research on fetal alcohol syndrome (FAS) has historically held that postnatal deficits result directly from prenatal alcohol exposure. Such exposure may alter infant behavior, and this in turn may affect maternal responsiveness and consequently increase the infant's risk for postnatal deficits. This study examined the effect of prental alcohol exposure on postnatal blood ethanol concentrations, pup development, and the ability of pups to elicit retrieval behaviors from the dam. Dams given access to a 15% ethanol solution throughout gestation and lactation showed blood ethanol concentrations of 0.1% whereas their pups had concentrations below the sensitivity of the test. Prenatal alcohol exposure was shown to have pharmacological effects on the pup's righting reflex and nutritional effects on its rate of weight gain. Control pups were better able to elicit retrieval behavior from control and alcoholic dams than were fetally alcoholic pups. These results indicate that that the condition of the pup can influence maternal responsiveness which, in turn, can influence pup development.
Dopamine antagonists produce an age‐dependent increase in the responding of the young chick
Authors: Zolman James F. , McDougall Sanders A.
Published: January 2005

In three experiments the effects of dopamine receptor antagonists on response‐contingent punishment and autoshape learning of 1‐ and 4‐day‐old chicks were determined. In the first two experiments, 1‐ or 4‐day‐old chicks (N = 120) were trained to key‐peck for heat reward and then injected intraperitoneally (ip) with either haloperidol (1.5, 2.5, or 5.0 mg/kg) or saline (Experiment 1) and with either haloperidol (2.0 mg/kg), sulpiride (50 mg/kg) or saline (Experiment 2) 30 min before a 96‐trial response contingent punishment session. In Experiment 3, 1‐ and 4‐day‐old chicks (N = 48) were injected ip with saline or haloperidol (2.0 mg/kg) 30 min prior to a 30‐trial autoshape learning session. In both the punishment and appetitive tasks 1‐day‐old chicks pretreated with either haloperidol (1.5 to 2.5 mg/kg) or sulpiride showed a significant increase in key‐peck responding compared with their saline injected controls. In contrast, 4‐day‐old chicks given either haloperidol (2.0 mg/kg) or sulpiride did not differ significantly from saline treated chicks on the punishment task, and on the autoshape task haloperidoltreated 4‐day‐old chicks responded on fewer trials than did their saline controls. These results indicate that dopaminergic synaptic transmission in the young chick as measured by dopamine D2 receptor blockers is functionally different at 1 compared with 4 days of age.
The effect of early experience on water maze spatial learning and memory in rats
Authors: Tees Richard C. , Buhrmann Kristin , Hanley Jordan
Published: January 2005

In the first of two experiments on spatial competence, groups of light‐reared (LR) and dark‐reared (DR) rats were compared using a (latent learning) variation of the Morris Water Maze task. On their initial test, the LR rats benefited more than DR rats did from viewing the room/pool from a platform in the correct location. Further, visually experienced rats remember the location of the platform more than DR rats when retested one month later. In a second experiment, in which a proximal cue as well as location was varied from trial to trial, LR rats again proved to be more competent than their DR counterparts. This second task also revealed significant benefits related to stimulation history in the case of a third group of animals raised in enriched or complex environment (CR) conditions. The results are discussed in terms of the nature of the impact of early experience on the ability to acquire and remember spatial concepts.
Kinematic variability and relationships characterizing the development of walking
Authors: Lasko‐McCarthey Peggy , Beuter Anne , Biden Edmund
Published: January 2005

The purposes of this study were: (1) to determine the pattern of variability and relationships in joint kinematics characterizing the development of walking and (2) to determine whether controlling for postural stability in new walkers results in less variability. The variability and relationships among hip, knee, and ankle motions were measured during 10 gait cycles of new walkers, supported new walkers, two‐year‐olds and seven‐year‐olds. Fourier series were generated for each joint motion and standard deviations were compared across groups. An age‐related decline in variability was evident in select portions of the cycle. Stance and swing phase duration correlated with cycle duration for all ages. Postural support did not lessen variability in joint rotations for new walkers. Cross‐correlations for hip‐knee, knee‐ankle, and hip‐knee rotations were strong across all groups. These results suggest that a coordinative structure for walking produces strong intralimb coupling early in development, despite variability in select portions of joint motions.
Developmental constraints on the expression of behavioral and heart‐rate orienting responses: I. The role of cardiosomatic coupling
Authors: Hayne Harlene , Richardson Rick , Campbell Byron A.
Published: January 2005

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 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.