bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasounds in neonatal rats: Novel, predator and conspecific odor cues
Authors: Lyons David M. , Banks Edwin M.
Published: January 2005

Neonatal rat ultrasound repetition rates were monitored in response to 6 odor cues, including 1 novel, 2 predator, and 3 conspecific olfactory stimuli. Contrary to predictions of previous studies, predator odor did not elicit consistently low call rates. A significant difference was detected between litters tested with the same odor cue for the foreign and predator odor treatments. Odor was the only significant effect to explain differences in neonatal ultrasonic responses to conspecific odor treatments. Call rates recorded for the novel lactating female odor were significantly greater than those for the home bedding and adult male odors. Odors associated with the home cage or with an adult male elicited low call rates.
Olfactory contributions to dehydration‐induced anorexia in weanling rats
Authors: Bruno John P. , Hall W. G.
Published: January 2005

By 20 days of age, dehydration produces a clear anorexia, even though weanling rats have had only limited feeding and drinking experience. Their lack of ingestive experience makes weanlings good subjects for studying the physiological mechanisms subserving anorexic phenomena because learned contributions are unlikely to add significant complications. Twenty‐day‐old rats dehydrated by hypertonic saline injection were anorexic when offered milk or solid food (rat chow), but not when offered sucrose solutions (Experiment I). However, when the scent of almond was associated with sucrose solutions, or with water, intake of these solutions was depressed by dehydration (Experiment II). Thus for dehydrated rats, olfactory stimulation may help produce dehydrationinduced anorexia. Making rats anosmic by intransal lavage with ZnSO4 (Experiment III) eliminated the anorexia to almond‐scented water and partially eliminated that to milk. For these fluids, an odor cue seems a requirement for the occurrence of dehydration‐anorexia. In Experiment IV, we found that dehydration‐anorexia did not occur when milk was infused directly into pups' mouths. This finding suggests that the inhibitory process mediating dehydration‐anorexia influences the approach to food and not the actual consumatory response that occurs once food is in the mouth. The inhibition of feeding produced by dehydration, therefore, may depend largely on olfactory cues, and seems to operate at a distance, as rats locate and approach food.
Development of species identification in ducklings: IX. The necessity of experiencing normal variations in embryonic auditory stimulation
Authors: Gottlieb Gilbert
Published: January 2005

The domestic mallard duck embryo must be exposed to its embryonic contact‐contentment call at a repetition rate of 4 notes/sec if the neonate is to show the species‐typical preference for the maternal call at its normal rate (3.7 notes/sec) after hatching. Exposing the embryo to the contact call at either 2.1 notes/sec or 5.8 notes/sec is no more effective than no auditory experience at all. To determine if there is a critical period for exposure, embryos were exposed to the 4 notes/sec call either before or after hatching. Both periods proved equally effective provided only that a 48‐hr “consolidation” period was allowed to intervene between stimulation and testing. That is, the birds tested 24 hr after prenatal or postnatal stimulation behaved as if they were not stimulated at all. The present study was undertaken to determine whether the curious requirement for a consolidation period is a normal developmental phenomenon or a consequence of limiting the birds to exposure to a call with an abnormally invariant repetition rate of 4 notes/sec. To that end, embryos were stimulated with the same call as before but at variable rates of 2.1, 4, and 5.8 notes/sec, as happens under normal conditions of development. In this case, the neonates had no need for a consolidation period and showed the species‐typical preference at 24 hr after hatching. Thus the previous results were a consequence of an abnormally narrow range of embryonic auditory stimulation. A 2nd experiment showed that, if the birds' postnatal perception was to be normal, the embryos could not be merely exposed to the rhythmic component of the contact call, but had to experience the characteristic frequency modulation of the call as well.

These results indicate that we require surprisingly detailed information about the sensory stimulation present during the usual course of development of our subject species if we are to give an appropriate interpretation to the results of early experiential and critical period manipulations. Knowledge of usual sensory‐stimulative variations has not been a conspicuous feature of developmental psychobiological studies in the past.
Chicken muscular dystrophy: An inherited disorder of flight
Authors: Provine Robert R.
Published: January 2005

Dystrophic (University of California, Davis, line 413) and normal control (Davis, 1. 412) chicks (Gallus domesticus) between 7 and 49 days old were tested for flight‐related pathology and righting ability. Drop‐evoked lateral flight developed in control chicks between 7 and 13 days. Dystrophic chicks never developed lateral flight. Both dystrophic and control chicks showed drop‐evoked wingflapping on the day of hatching. Also, dystrophic chicks had a normal but slightly higher drop‐evoked flapping rate than controls at 13 days. Thus, the neural circuits that initiated and generated the rate of drop‐evoked wing‐flapping, present in dystrophic chicks at birth, were intact at 13 days, when deficiencies in lateral flight and righting ability were already present. The righting behavior of control chicks was superior to that of dystrophic chicks at all ages from 7 to 49 days.
Pup recognition in Mus musculus: Parental discrimination between their own and alien young
Authors: Ostermeyer Malcolm C. , Elwood Robert W.
Published: January 2005

The responses of male and female mice each presented with a sequence of 4 pups from their own litter, a pup from another litter but of the same age and strain, and finally their own pup were noted. Both sexes spent longer sniffing the alien pup than the preceding own pup regardless of the ages of pups at testing, and more time licking the alien pup on some test days. Young pups (Days 0–3; birth = Day 0) emitted fewer ultrasounds in the presence of a male than a female, but there was no quantitative difference in the vocalizations of own and alien pups. These data indicate that adult mice are able to discriminate between their own and alien offspring; this discrimination appears to be based upon olfactory and possibly gustatory cues rather than auditory ones.
Appetitive instrumental training in preweanling rats: I. Motivational determinants
Authors: Smith Gregory J. , Bogomolny Alice
Published: January 2005

Two experiments tested learning and retention of preweanling rats (10, 15, and 23 days of age) with an appetitive T‐maze spatial discrimination task, using 3 different reinforcers for training (Mother Alone, Mother + Milk, and Milk Alone.) The hypothesis was that immature rats are prepared to select and generate effective hypotheses for learning in an environment bearing some similarity to the home nest prior to their exhibiting similar capacities in other contexts. In Experiment I, we found support for this hypothesis in that 10‐ and 15‐day‐old rats were able to acquire the maze task when reinforced with Mother Alone or Mother +Milk, but not when reinforced with Milk Alone. In Experiment II, we report that 23‐day‐old rats weaned at 19 days postpartum were better at learning the maze task with milk as the reinforcer than littermates raised until training with the dam. We hypothesize that the development of foraging strategies might be necessary for the expression of maze behaviors reinforced with milk alone.
The ontogeny of delta‐9‐tetrahydrocannabinol responsiveness in the rabbit
Authors: Fish Barbara Schneiderman , Consroe Paul
Published: January 2005

An autosomal receissive (thc/thc) in our closed colony of New Zealand White rabbits (Uaz:NZW‐thc) results in nonfatal, behavioral convulsions following intravenous (i.v.) injections of delta‐9‐terahydrocannabinol (THC) and other psychoative cannabinoids of marijuana. The ontogeny of the convulsive response was evaluated in potential THC‐seizure‐susceptible (SS) rabbits from postnatal Days (PN) 15–548. Ages of nonsusceptibility (PN 15–23), partial susceptibility (PN 24–38), and complete susceptibility (PN 39–548) were found. Also, open‐field activity was determined in PN 14–25 THC‐SS and THC‐seizure‐resistant (SR) rabbits. Administration of THC during the seizure‐insensitive period resulted in genotype‐dependent alternations in photocell activity and sprawling.
Species discrimination in infant pigtail macques with pictorial stimuli
Authors: Swartz Karyl B.
Published: January 2005

Two experiments used a visual fixation habituation‐dishabituation paradigm to study the ability of young, socially restricted pigtail macaques to discriminate among adults of 3 macaque species (pigtail, cynomolgus, and stumptail) with pictures as stimuli. The results of the 1st study demonstrated that 3‐month‐old pigtail infants could discriminate among faces of adult females of all 3 species. The 2nd study was methodologically similar to the 1st, with the exception that the face stimuli were presented upside‐down. The results of Experiment II demonstrated no species discrimination, suggesting that the socially relevant discrimination demonstrated in Experiment I was a function of cues unique to the upright face and not a function of abstract cues unique to the upright face and not a function of abstract cues available in both upright and upside‐down facial stimuli.
A developmental look at an auditory illusion: The precedence effect
Authors: Clifton Rachel K. , Morrongiello Barbara A. , Dowd John M.
Published: January 2005

Infants aged 2 and 6 months were tested with the precedence effect, an auditory phenomenon involving sound localization. Each infant was tested with two types of stimuli: sound from a single loudspeaker and precedence‐effect sounds produced by the same sound put through two loudspeakers, with one output leading the other by 7 msec. Older infants localized precedence‐effect stimuli as they did single‐source stimuli, indicating that they perceived this phenomenon as expected. Two‐month‐olds turned their heads toward single‐source sounds, but did not localize precedence‐effect sounds, suggesting that that more difficult perceptual task had not been achieved at this age. In general, headturning toward sound proved far more difficult to elicit in younger infants. A click train was ineffective, but a tape‐recorded human voice elicited above‐chance low‐level turning. The developmental changes in auditory behavior are discussed in terms of the rapid growth of the auditory cortex.
Different mechanisms for social transmission of diet preference in rat pups of different ages
Authors: Galef Bennett G. , Kennett Deborah J.
Published: January 2005

We examined the role of simple exposure to a diet in the development of preference for that diet in rat pups 21, 28, 38, and 45 days of age. We found: (1) that 21‐day‐old rat pups exhibited a preference for a diet to which they were simply exposed for 30 min; (2) that 28‐, 38‐, and 45‐day‐old pups failed to exhibit simple‐exposure induced preference for a diet; and (3) that pups at all ages examined, exposed for 30 min to an anesthetized conspecific whose face had been dusted with a diet, subsequently exhibited a preference for that diet. We interpreted these data as indicating that socially‐induced diet preference in 21‐day‐old pups can be explained by effects of simple exposure, while socially‐induced diet preference in older rats cannot. Pups older than 21 days of age appear more sensitive to the social context in which diet‐identifying olfactory cues are experienced than do 21‐day‐old pups.
The effects of maternal isolation and light and feeding cycles on the growth of rat pups
Authors: Anderson Veanne N. , Smith Grant K.
Published: January 2005

Rat pups were implanted with intragastric catheters and reared in isolation from their dams and siblings from 3 to 18 days postnatally. They were kept in 12:12 LD or DL, constant light, or constant darkness and were fed with one of three feeding schedules: (1) equal amounts of food delivered during the light and dark periods, (2) 65.3% of the food delivered during the light period, or (3) 65.3% of the food delivered during the dark period. At 18 days postnatally the body, spleen, and kidney weights of all isolated pups did not differ from those of their mother‐reared littermates. The isolated pups had smaller cerebellums and forebrains and heavier livers than mother‐reared pups. Heavier body and spleen weights and smaller livers were observed in pups with cyclic feeding. Heavier body and forebrain weights were associated with a predominantly diurnal feeding schedule—the schedule which most closely approximated the natural nursing rhythm. Isolated pups opened their eyes sooner than mother‐reared littermates. These results suggest that interactions between feeding and light cycles may influence growth and development.
Multidimensional perceptual development: Consistency of responses to frequency and intensity in young chickens
Authors: Gray Lincoln
Published: January 2005

The development of consistent responses to multidimensional acoustic stimuli was investigated in newborn chickens. Young chicks suppress their ongoing peeps when they hear a change in an acoustic stimulus, and the amount of that suppression is related to the amount of change. Durations of suppression can thus be interpreted as perceived differences between pairs of stimuli. The suppressions elicited by all possible transitions between pairs of 5 acoustic stimuli that differed in frequency, intensity, and repetition rate were measured at 2 ages. These data were analyzed with a multidimensional scaling program. Interpretable structure is evident in the results from 4‐day‐old chicks to a subset of the stimuli that vary in frequency and intensity. Newborn chicks, in contrast, showed inconsistent responses. Neither age group responded with interpretable structure to stimuli that differed in 3 dimensions. Thus, consistent responses to 2‐dimensional acoustic stimuli emerge over the first few postnatal days. Perceptual dimensions become associated with the physical dimensions of frequency and intensity as animals mature.
Ontogeny of seizure incidence, latency, and severity in genetically epilepsy prone rats
Authors: Hjeresen Dennis L. , Franck Joann E. , Amend Diane L.
Published: January 2005

The Genetically Epilepsy‐Prone Rat (GEPR) is a widely studied model of epileptiform disorders. While there is considerable evidence that neurotransmitter abnormalities contribute to the unusual sensitivity of these animals to seizures, the possibility that seizure susceptibility may reflect developmental changes in the central nervous system has not been fully addressed. In the present study, 91 GEPR‐9 pups were tested for incidence, latency and severity of an audiogenically induced seizure at 6, 9, 12, 15, 18, 21, 24, 27, 28, 29, or 30 days postpartum (1 test per pup) and retested at 60 days. Seizure incidence, latency, and severity were significantly greater on Days 27, 28, 29, and 30 than on all previous days. The first observation of running fits occurred in Day 18 pups and the first evidence of seizures occurred in Day 21 pups. When retested at Day 60, seizure incidence and severity were significantly greater than on initial tests while latency declined. The results suggest that seizure susceptibility in the GEPR‐9 occurs as the result of developmental events in the CNS occurring on or shortly after Day 18 postpartum.
Development of species identification in ducklings. XIII: A comparison of malleable and critical periods of perceptual development
Authors: Gottlieb Gilbert
Published: January 2005

The present experiments sought to determine the relationship of the malleable period—when the mallard duck embryo is most susceptible to alien forms of maternal auditory stimulation—to the critical period, when the embryo must hear its own vocalizations in order to respond normally to the species‐typical maternal call after hatching. It was found that a preference for either a wood duck or a chicken maternal call could be induced in devocalized mallard duck embryos by exposing them to either alien call some time between day 24, 0600 to day 26, 0600 hrs. Further experiments showed the height of the malleable period to be between day 24, 1400 hrs and day 25, 0800 hrs of embryonic development. Since the embryonic critical period for maintenance of the species‐typical maternal auditory preference spans day 24, 0800 hrs to day 26, 0800 hrs, the malleable period for the induction of a preference for species‐atypical maternal stimulation falls inside the critical period. While it is often assumed that malleable and critical periods overlap, this is the first behavioral study to actually demonstrate the temporal relationship of the two periods. It would seem important to further examine malleable and critical periods of development in a broader array of developmental contexts and species to determine whether malleable periods for atypical or abnormal development and critical periods for species‐typical or normal development always coincide.
Human cyclic motility: Fetal–Newborn continuities and newborn state differences
Authors: Robertson Steven S.
Published: January 2005

The spontaneous movement of 41 healthy human newborns was analyzed for cyclic patterns during different behavioral states and also compared to similar data obtained during their last few months of gestation. Spectral analysis was used to identify and quantify the motility cycles, except in quiet sleep, for which the instantaneous frequency of the isolated movements was analyzed. Cyclic motility (CM) was common in all states, and measures of its cyclic organization were similar in the nonsleep states in spite of very large differences in the total amount of movement. During active sleep, CM was weaker and less regular than during the non‐sleep states, but similar to fetal CM during the last month of gestation. Thus cyclic variation in spontaneous motor activity, a basic feature of fetal behavior, is also a nearly constant feature of newborn spontaneous movement. Fetal CM persists relatively unchanged in the newborn during active sleep, and the cyclic organization of newborn movement is independent of the level of motor output.
Continuities in infant memory development
Authors: Hill Wendy L. , Borovsky Dianne , Rovee‐Collier Carolyn
Published: January 2005

Fifty‐five 6‐ to 7‐month‐old human infants were trained in an operant conditioning procedure, adapted from a procedure developed for 3‐month‐old, in which kicks were reinforced by conjugate movement of a mobile. Retention was assessed in a simple forgetting paradigm (Expt. 1) or in a reactivation paradigm (Expt. 2) with either the training mobile or a different one serving as the retrieval cue. In Experiment 1, retention was tested 1, 7, 14, or 21 days after training. When the training and test mobiles were the same, infants exhibited virtually no forgetting for 14 days, but forgetting was complete by 21. When the training and test mobiles were different, infants exhibited no retention, discriminating the novel mobile for as long as they could remember the contingency. In Experiment 2, when the training mobile was presented as a reminder, the forgetting previously seen after 21 days was alleviated; when a different mobile was the reminder, it was not. These findings reveal that the efficacy of a reminder is predicted by the efficacy of that same stimulus in cuing the original memory 24 hr following training. Although the 6‐month‐olds learned more rapidly and remembered longer than infants half their age, their memory processing was described by the same basic principles.
The ontogeny of drinking evoked by activation of brain angiotensin in the rat pup
Authors: Leshem Micah , Boggan Barbara , Epstein Alan N.
Published: January 2005

Renin (1 ng) was injected into the 3rd ventricle of the brain of rat pups at various ages, and their ingestion was measured by weighing them either after 40 min of oral infusion of water or milk while they were away from their dam (off‐dam), or after 40 min of suckling from their dams (on‐dam). Beginning at 3–5 days of age, renin increased ingestion of milk and water off‐dam. After 15 days of age, milk ingestion off‐dam was no longer increased by renin, but intake of water continued to be evoked. In contrast, renin did not increase intake by suckling at any age. These findings reveal that the adult characteristics of the dipsogenic action of the renin–angiotensin system in the brain emerge at 15 days, at which age the increased intake becomes entirely specific for water. This finding confirms the precocity of the neural controls of drinking in the rat and shows that, like the controls of independent feeding, they are dissociated from those of suckling. It adds support to the idea that the neonatal mammalian brain contains separate neurological systems for suckling and for independent ingestion.
Stimulus attributes of reactivated memory: Alleviation of ontogenetic forgetting in rats is context specific
Authors: Richardson Rick , Riccio David C. , McKenney Michael
Published: January 2005

Numerous studies have shown that ontogenetic forgetting (infantile amensia) can be alleviated by a number of different types of reminder treatment. The present study extends the information about the alleviation of infantile amnesia by examining the “content” of the reactivated memory. Toward tis purpose, one attribute of memory (environmental context) was examined in rats tested either shortly after training (preamnesic) or after 1‐week retention interval. For the latter, a reactivation treatment was used to reverse infantile amnesia. At both intervals, a context shift resulted in impaired performance of a conditioned fear response. These findings demonstrate that environment context is an important component of the originally encoded memory as well as the reactivated amnestic memory. The implications of these results for both the reactivation of memory and general memory processes are discussed.
Ontogeny of susceptibility to experimental febrile seizures in rats
Authors: Hjeresen Dennis L. , Diaz Jaime
Published: January 2005

Two experiments were conducted using microwave hyperthermia (MHT) to induce seizures among limited numbers of Long‐Evans rat pups. The MHT model of febrile seizures eliminates several methodological complications inherent in previous animal models of the disorder. In Experiment 1, rat pups were rendered hyperthermic with MHT or were sham‐irradiated on Days 11, 13, 15 or 17 postpartum. The results indicate a statistically significant decline in seizure susceptibility with age. In Experiment 2, rats were subjected to either single or multiple hyperthermic episodes on Days 11, 13, 15, or 17 postpartum. The results indicate an increase in susceptibility to seizures attributable to prior seizure history. In both experiments, seizures were induced with increases in rectal temperature of 1 to 3°C. The results parallel many clinical features of febrile seizures and argue the efficacy of the MHT model.
Fetal gender and aggression in pregnant stumptail monkeys (Macaca arctoides)
Authors: Nieuwenhuijsen K. , Slob A. K. , De Neef K. J.
Published: January 2005

Agonistic behaviors of pregnant female stumptail monkeys, members of a large, well‐integrated group continuously living together, were studied during 480 observation hours (over 32 months). A total of 28 pregnancies of 20 females occurred, resulting in 12 male and 16 female live infants. The main finding was a significant decline in aggression, both received and performed, during the course of pregnancy. There was no clear unequivocal effect of fetal gender on aggressive behavior of the mothers‐to‐be.
Adrenocortical activity and behavioral distress in human newborns
Authors: Gunnar Megan R. , Connors Joan , Isensee Jill , Wall Leigh
Published: January 2005

The association between behavioral distress and adrenocortical activity was examined in two experiments with human newborns. In Experiment 1, behavioral and adrenocortical responses to 4 events (circumcision, blood sampling, weighing and measuring, and discharge examination) were compared using a between‐subject design. All 4 events elicited fussing and crying and elevations in plasma cortisol; however, differences in behavioral distress among conditions did not reliably predict differences in plasma cortisol. In Experiment 2, nonnutritive sucking was used to effectively reduce behavioral distress, but was not associated with a reduction in the adrenocortical response to stimulation. Finally, using data from both experiments, correlations were computed between behavioral distress and cortisol. Both positive and negative associations were found as a function of the type of stressor and the biomedical status of the newborn.
Ontogeny of polycose and sucrose appetite in neonatal rats
Authors: Vigorito Michael , Sclafani Anthony
Published: January 2005

Rat pups 3 to 15 days of age were infused with sucrose or Polycose solutions (.03 or .3 M) through oral cannulas and their solution intake, mouthing behavior, and general locomotor activity were recorded. Overall, the pups displayed similar ingestive responses to Polycose and sucrose. They discriminated between .3 M sucrose and water as early as 6‐days of age, and between .3 M Polycose and water as early as 9‐days of age. However, at the .03 M concentration the pups responded to Polycose before they responded to sucrose. The results confirm previous reports that rat pups have an unlearned preference for sucrose and demonstrate that a similar preference exists for starch‐derived polysaccharides. The Polycose appetite displayed by the neonatal rats is consistent with results obtained with adult animals which suggest that rats have taste receptors for starch‐derived polysaccharides as well as for sugars.
Experience with younger siblings facilitates maternal responsiveness in pubertal norway rats
Authors: Stern Judith M. , Rogers Louise
Published: January 2005

The latency of maternal behavior (MB) onset induced by cohabitation with pups (sensitization) increases in female and male Long‐Evans rats from 24 days of age (1–2 day latency) to 42 days of age (4–5 day latency). This decline in maternal responsiveness at Day 42 did not occur in 50% of rats (“responders”) which lived with their dam and younger siblings (conceived during the postpartum estrus) for either 4 or 11–18 days after their birth. In contrast to cessation of suckling at about Day 25 postpartum in the absence of a 2nd litter, when a 2nd litter was born >Day 26 or <Day 26 postpartum, suckling continued for a mean of 32 and 35.5 days, respectively (and up to Day 40). Also, time spent suckling during the 10 days following the birth of the 2nd litter was more than five times as great if the 2nd litter was born with little or no delay (Day 26). The offspring from the 1st litter spent about 80% of the diurnal observation time in proximity to the dam and younger siblings, and instances of nurturance (retrieving, crouching, licking) toward the young littermates were observed. However, the only dam‐litter interaction significantly related to subsequent maternal responsiveness by 1st litter offspring was a positive relation between the prior incidence of aggression by mothers towards juveniles and sensitization latency.
Effects of lateral displacement of the visual field on the development of visual‐motor abilities in cats
Authors: Hendy Helen M. , Riesen Austin H.
Published: January 2005

In this study, we test the flexibility of the cat's visual system by examining the visual‐motor effects of both moderate and extreme lateral displacement of the visual field. While being reared with masks that provided either 0, 15, or 30 diopters lateral displacement of the visual field, 23 kittens received 3 tests of visual‐motor abilities: a visual cliff task, a visual guiding task, and a five‐alley choice task. No significant differences were found among the 0, 15, or 30 diopter displacement groups for any of the 3 tasks for either the total number of days to reach criterion performance, for the development of performance over time during the early days of testing, or for the development over time to criterion performance. After reaching criterion, kittens readapted to transposed conditions of displacement. The group changed 30 diopters did significantly worse than the group changed 15 diopters, both in error scores and in time to criterion performance. The present results with kittens are compared to those of other investigators and suggestions are made for future research.
Metaphors for development: How important are experiences early in life?
Authors: Klopfer Peter
Published: January 2005

The many students of development have held rather diverse views on the importance of early experience. Some gave early experiences great prominence (e.g., Freud and his followers, Kuo, 1967), while others largely rejected the pivotal importance of particular early events (e.g., Thorndike), and yet others took a more eclectic tack: Some events in certain species but not all events or in all cases (e.g., Hinde, 1974, Lehrman, 1970). The extremes among the prevailing views are often characterized metaphorically. I propose to do this, then to examine the kinds of situations the metaphors describe, and inquire into their generality and usefulness. Clearly this runs the risk of undue simplification, but there is, I believe merit in occasionally ignoring some of the subtleties that usually must concern us.
Body scale and the development of prehension
Authors: Newell K. M. , Scully D. M. , Tenenbaum F. , Hardiman S.
Published: January 2005

This study examined whether common dimensionless ratios define the critical point in the shifts in the grip coordination pattern of preschoolers and adults engaged in a displacement grasping activity with cubes that varied in object size. The findings indicated that there was an interaction between task constraints and organismic constraints in determining the grasping pattern utilized. However, when the object size is scaled to hand size there are common dimensionless rations that correspond to the grasping patterns and the limb orientations employed across the age range utilized. Furthermore, 5 grip configurations accounted for the majority of grip variance in both age groups. The findings suggest a strong role for the impact of body scale on the development of coordination and provide preliminary evidence for the view that the development of prehension is a reflection of the constraints imposed on action.
Maternal behavior of SHR rats and its relationship to offspring blood pressures
Authors: Myers Michael M. , Brunelli Susan A. , Squire Jonathan M. , Shindeldecker Richard D. , Hofer Myron A.
Published: January 2005

In Part I of this study maternal behavior of 15 spontaneously hypertensive (SHR) and 11 Wistar‐Kyoto (WKY) rat mothers was recorded throughout the preweaning period. SHR mothers were observed: 1) in arched‐ and blanket‐nursing postures more often, and in passive‐nursing posture less often, 2) licking their pups more often, and 3) resting less often. Further, SHR mothers retrieved their pups more quickly than did WKY. In the second part of this study we found that a composite maternal behavior score, derived from summing occurrences of motheripup contact, arched‐nursing, and puplicking, was positively correlated with the offspring blood pressures. This relationship, which accounted for 43.5% of the variance in adult blood pressure, suggests that certain types of interactions between mothers and their pups may contribute to individual differences in cardiovascular system development.
Relationships between maternal behavior of SHR and WKY dams and adult blood pressures of cross‐fostered F1 pups
Authors: Myers Michel M. , Brunelli Susan A. , Shair Harry N. , Squire Jonathan M. , Hofer Myron A.
Published: January 2005

In this experiment SHR and WKY dams reared genetically identical F1 pups derived from SHR X WKY matings. We found that a composite maternal behavior score was positively correlated with adult blood pressures of the fostered offspring. This replicated a similar finding from our previous study in which SHR and WKY mothers reared their own pups. Unlike this previous Study, WKY dams rearing F1 pups exhibited maternal behavior patterns similar to SHR dams. Finally, we found their was no effect of the strain of foster mother upon adult blood pressures of the F1 offspring. These results indicate that some aspects of maternal behavior may change as a function of pup characteristics, and support our hypothesis that the cardiovascular system may be shaped by experiences of early life which are embedded in mother/young behavioral interactions.
Male rat pups are more hesitant to urinate in response to anogenital stimulation than are their female sibs
Authors: Clark Mertice M. , Galef Bennett G.
Published: January 2005

Male rat pups required more anogenital stimulation before they began to urinate than did their sisters and males produced more urine than their female sibs during a fixed period of anogenital stimulation. These findings are interpreted as consistent with the view that neonatal mammals can manipulate the behavior of their dams.
The role of homecage environmental stimuli in the facilitation of shock‐motivated spatial discrimination learning in rat pups
Authors: Misanin James R. , Hinderliter Charles F.
Published: January 2005

In three experiments we examined the role of homecage environmental stimuli on learning an aversively motivated spatial discrimination task in 11‐day‐old rats. Varying the presence and absence of nest shavings in the correct and incorrect arms of a T‐maze in Experiment 1 revealed that nest shavings had both nondirective facilitation and approach‐eliciting properties. Training the 11‐day‐old rats in the presence or absence of shavings over three daily sessions and comparing their performance on the third day of training with that of a maturation control in Experiment 2 indicated that there is a residual training effect of the approach‐eliciting property of nest shavings on shock‐escape behavior. In Experiment 3, using nest shavings either as an irrelevant stimulus or as a redundant relevant cue in an aversively motivated T‐maze reversal task suggested that 11‐day‐old rats acquire the discrimination task using non‐nest spatial or directional cues as well as those provided by nest shavings. Overall, these results suggest that nest shavings introduced into aversively motivated tasks create a learning environment comparable to that of appetitively motivated instrumental tasks utilizing suckling from an anesthetized dam as a reinforcer.
Measuring rates of sexual development in female Mongolian gerbils
Authors: Clark Mertice M. , Galef Bennett G.
Published: January 2005

In previous experiments, we have shown that age at vaginal introitus predicts adult patterns of reproductive, maternal, and aggressive behavior of female Mongolian gerbils. In the present series of studies, we explored the relationship in gerbils between age at vaginal patency and three other indices of rate of female sexual development: ovarian weight, occurrence of vaginal estrus, and onset of attractiveness to males. We found that female gerbils, classified on the basis of their ages at vaginal introitus as early‐maturing: (a) exhibited greater ovarian weights throughout development than did their late‐maturing, female sibs; (b) exhibited estrus and Diestrus I stage vaginal smears and, by inference, ovulation at an earlier age than did late‐maturing females; and (c) elicited mounting by males at an earlier mean age than did late‐maturing females. The data were consistent with the hypothesis that age at vaginal introitus is a reliable indicator of rate of sexual development in female Mongolian gerbils.
The quantitative relationship between nutritional effects on preweaning growth and behavioral development in mice
Authors: Wainwright Patricia , Pelkman Christine , Wahlsten Douglas
Published: January 2005

Our objective was to establish whether nutritional effects on the behavioral development of preweaning mouse pups were linearly related to effects on body and brain growth or whether there was a threshold effect, with behavior being affected only by nutritional extremes. We also used a standardized scale of development to compare the relative magnitude of such effects on morphological and behavioral measures. The level of nutrient availability was manipulated continuously by rearing the pups in litter sizes ranging from 3 to 12. On Day 32 post‐conception, measures were taken of body weight, brain weight, thickness of the cerebellar external granular layer (EGL), and behavioral development. The relationship between litter size and body weight, brain weight, and behavioral development was best described by a linear regression model; no threshold effect was apparent. By comparing measures on animals from different litter sizes at the same age (32 days) to standard developmental curves over a wide range of ages, we found that for every additional pup in a litter, body growth was retarded by the equivalent of 1.28 days, brain weight by 0.44 day, and behavioral development by 0.07 day.

Although the variation in nutrient availability provided by this range of litter sizes does result in a linear relationship between growth and behavioral development, there is nevertheless considerable sparing of function.
Dopamine D‐2 receptor mediation of response suppression learning of young rats
Authors: McDougall Sanders A. , Nonneman Arthur J.
Published: January 2005

In three experiments, the effects of augmenting or blocking dopamine (DA) D‐2 receptor activity on the ontogeny of response suppression learning of preweanling rat pups were determined. In the intial experiment, rat pups were trained to traverse a straight alley for nipple attachment to an anesthetized dam. When footshock (0.2 mA, 0.5 sec) was made contingent on responding, younger (11‐and 13‐day‐olds) rat pups were deficient to older (17‐and 19‐day‐olds) pups at withholding punished responding. In the subsequent experiments, response suppression learning was assessed after injecting 11‐and 17‐day‐old rat pups with the specific DA D‐2 agonist, LY 171555 (0.005−, 0.01−, and 0.1−mg/kg, i.p.), or the specific DA D‐2 antagonist, sulpiride (5.0−, 15.0−, and 50.0−mg/kg, i.p.). LY 171555 enhanced the punished responding of both the 11‐and 17‐day‐old rat pups; whereas, sulpiride increased the punished responding of the 17‐, but not the 11‐day‐olds. In four additional experiments, the effects of LY 171555 and sulpiride on the locomotor activity, nociception, and reinforcement processes of 17‐day‐old rat pups was assessed. Rat pups given LY 171555 (0.01 mg/kg, i.p.)exhibited enhanced locomotor activity and a trend towards hyperanalgesia using a hot plate task. Sulpiride (15.0 mg/kg, i.p.) completely antagonized LY 171555′s activity enhancing effects and had hyperalgesic properties. In two experiments, sulpiride did not affect the nonpunished appetitive responding of the 17‐day‐olds; whereas, haloperidol‐treated pups responded on fewer reinforced trials than did saline‐treated pups. Therefore, these results indicate that the response suppression learning of 17‐day‐old rat pups is mediated, at least partially, by a DA D‐2 receptor system, and that D‐2 receptors are also involved in the locomotor activity and nociceptive responses of young rat pups.
Nursing interaction of Wistar rats is modified by prior experience of altered nursing bout length
Authors: Hofer Myron A. , Zmitrovich Ann , Shair Harry N.
Published: January 2005

We tested the capacity of 2 week postpartum Wistar rat litters and their dams to adapt to experimental shortening and lengthening of the time available for nursing while maintaining the frequency of bouts constant, using manual transfer between cage compartments. In 8‐hr and 24‐hr experiments, the short bout group (10 min/hr) gradually came to show normal litter weight gain, short latency milk ejections, and increased high arched nursing position, while the 40‐min/hr group showed increased latency to attachment and longer latency to ME compared to the 20 min/hr control group. Pup body temperature did not vary between groups. Although pups in the 10‐min group showed increased dam‐directed behaviors in the first 8h, this difference vanished thereafter. In a twenty‐fifth cycle, after dams and litters were exchanged, the prior experiences of the dams and not of the litters were found to determine the dynamics of milk exchange.
Rat pup isolation distress and the brain benzodiaze pine receptor
Authors: Insel Thomas R. , Gelhard Robert E. , Miller Leonard P.
Published: January 2005

Pharmacologic studies have demonstrated that benzodiazepines can modulate the ultrasonic vocalizations (USV) associated with social separation of rat pups. In this study, in vivo receptor autoradiography was used to determine if brain benzodiazepine receptors were functionally less available to bind an exogenous ligand during social separation. The labeled benzodiazepine receptor antagonist, 3H‐RO 15‐1788, was given to 10‐day‐old rat pups with varying schedules of social separation. In initial studies with homogenized and solubilized tissue, we found a 30% reduction in binding to cortex when pups were separated for 25 min beginning 5 min prior to tracer injection. In subsequent autoradiographic studies with this same separation schedule, the binding of 3H‐RO 15‐1788 was examined in 21 brain regions. Again binding was decreased in neocortex (frontal, motor, and somatosensory). In addition, we found significantly decreased binding in hippocampus, dentate gyrus, and superior and inferior colliculi. These same regions showed no alteration of in vitro binding of 3H‐RO 15‐1788. Therefore, these decreases in in vivo binding do not reflect changes in receptor number. The interpretation of decreased in vivo binding and implications of these results for defining the neural substrates of separation behavior are discussed.
Effect of maternal presence on the cardiac and behavioral responses to shock in rats as a function of age
Authors: Richardson Rick , Siegel Michael A. , Campbell Byron A.
Published: January 2005

In two experiments the effects of the presence of an anesthetized lactating dam on the developing rat's response to a series of midly painful shocks was examined. Both cardiac and behavioral responses to the shock stimulus were recorded. In the first experiment animals were tested at either 16, 20, or 24 days of age. The presence of the anesthetized dam markedly reduced the behavioral response to shock of the 16‐day‐old but not the older rats. A similar pattern of results was obtained with the shock‐elicited tachycardia. The second experiment replicated these results with the 16‐day‐old rat and also demonstrated that being shocked in the presence of a lactating dam influences the animal's reaction to a subsequent series of shocks given when it is alone. The results of these two experiments are discussed in terms of other studies that have examined the influence of maternal presence on the developing animal's response to stressful or painful stimuli.
Stimulus duration and repetition rate influence newborns' head orientation toward sound
Authors: Clarkson Marsha G. , Clifton Rachel K. , Swain Irina U. , Perris Eve E.
Published: January 2005

Three experiments evaluated the effects of stimulus duration and repetition rate on newborns' head orientation responses. In Experiment 1, 28 infants turned toward a 20‐sec continuous rattle sound but not toward 14‐and 500‐msec rattle sounds. Signal energy as a possible explanation for the infants' difficulty orienting toward brief sounds was explored in Experiment 2. Twenty neonates did not turn toward a single 90 dB, 14‐msec rattle sound, although a longer duration (10 sec) sound containing less energy (70 dB) did elicit reliable head orientation. In Experiment 3, 16 neonates heard trains of repeated 14‐msec rattle sounds (2/sec, 1.3/sec, and 1/sec) lasting 10 sec as well as a 10‐sec continuous rattle sound. They turned toward the most rapidly repeating brief sound and the continuous one, while the slowly repeating sounds elicited little head movement in any direction. These results suggest that newborns' head orientation is selectively deficient for brief sounds, that the difficulty does not result from lessened energy in the brief sounds, and that the efficacy of repeated brief sounds depends upon their repetition rates.
Task constraints and infant grip configurations
Authors: Newell K. M. , Scully D. M. , McDonald P. V. , Baillargeon Renée
Published: January 2005

The prehensile grip configurations of infants aged 4 through 8 months were examined as they grasped objects that varied in size and shape. The findings revealed that infants as young as 4 months systematically differentiate grip configurations as a function of the object properties in essentially the same way that 8‐month‐old infants do. However, the younger 4‐month‐old infants predominantly used the haptic system in additional to the visual system for information pick‐up regarding object properties, whereas 8‐month‐old infants predominantly used information from the visual system alone to differentiate grip configurations according to the object properties. Infants apparently percive the same action‐relevent information through different emphases of the sensory modes to drive the action system with a similar grip configuration for a given object. It is proposed that the traditional description of an orderly sequence to the development of infant prehension (e.g., Halverson, 1931) is too conservative and inflexible to capture the functionally adaptive prehensile behavior of infants to changing task constraints.
Premature visual stimulation accelerates intersenory functioning in bobwhite quail neonates
Authors: Lickliter Robert
Published: January 2005

Recent evidence from both altricial and precocial neonates suggests that premature stimulation of a later developing sensory system may alter the functioning of earlier developing sensory systems. The present study examined the influence of prenatal visual stimulation on postnatal auditory functioning in precocial bobwhite quail chicks. Hatchlings that experienced patterned light during the 24–36 hr prior to hatching did not exhibit a naive auditory preference for their species‐specfic maternal call at 24 hr or 48 hr following hatching, a reliable phenomenon in chicks not receiving embryonic visual stimulation. To examine whether this lack of responsiveness resulted from enhanced intersensory functioning, hatchlings were tested for preference for both auditory and visual features of the bobwhite hen. Results indicate that prematurely stimulated chicks require species‐typical auditory and visual stimulation earlier in postnatal development than do normally reared chicks to direct their filial behavior. These findings point to the importance of normally occurring developmental limitation of sensory input to early species‐typical sensory/perceptual organization.
Development of head position preference during early infancy: A longitudinal study in the daily life situation
Authors: Hopkins Brian , Lems Yvonne L. , Palthe Titia Van Wulfften , Hoeksma Jan , Kardaun Otto , Butterworth George
Published: January 2005

We studied developmental changes in supine head position preference in a group of 14 healthy full‐term infants from age 3 to 18 weeks. The infants assumed an initial head‐right position until 12 weeks. For the maintenace of a head position, a loglinear analysis revealed a developmental trend from and initial head orientation to the right to one with the head in the midline at around 12 weeks. The maintenance of a midline head position was preceded by a marked improvement in postural stabilization, defined as the ability to hold the head upright when seated in an infant chair. The relationship between head position preference and behavioral state changed with age: At 3 weeks all infants maintained the same position regardless of state, but by 18 weeks this situation held for only 64% of those who cried. The implications of these findings for the development of handedness are discussed.