bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of handling during infancy on the sympathetic–adrenal medullary system of rats
Authors: McCarty Richard , Horbaly William G. , Brown Maire S. , Baucom Katheryn
Published: January 2005

We examined the effects of daily handling and maternal separation (5 min per day) on the responsiveness of the sympathetic‐adrenal medullary system of Sprague‐Dawley rats before weaning and in adulthood. Plasma levels of norepinephrine (derived primarily from sympathetic nerves) and epinephrine (released from the adrenal medulla) were elevated in handled pups compared to unhandled controls at 14 and 18 days of age but not at 6 and 10 days of age. When tested in adulthood, previously handled and control rats did not differ with respect to basal or stress‐induced increments in plasma levels of norepinephrine and epinephrine. These results indicate that brief daily episodes of handling and maternal separation are attended by an increase in sympathetic‐adrenal medullary tone in 14–18‐day‐old rats. However, the enhanced response of the sympathetic–adrenal medullary system of separated rats may not persist into adulthood.
Effects of fostering on seizure activity in the Mongolian gerbil
Authors: Kaplan Harriett
Published: January 2005

The purpose of this experiment was to ascertain whether seizure propensity in Mongolian gerbils is affected by differences in behavior and/or nurturing ability of seizure‐prone (SP) and nonseizure‐prone (NSP) parents. Day‐old SP and NSP pups were cross‐fostered, while other SP pups were fostered to SP parents. Matched nonfostered littermates served as controls. The SP gerbils fostered to NSP parents exhibited delayed onset of seizure activity whereas SP gerbils fostered to SP parents did not. Neither fostered nor nonfostered NSP gerbils ever underwent seizures. This experiment establishes that some familial defect underlies seizure‐proneness in gerbils, but that expression of this tendency is affected by parental behavior and/or nurturing ability.
Persistence of attention to a novel conspecific: Some developmental variables in laboratory rats
Authors: Thor D. H. , Wainwright K. L. , Holloway W. R.
Published: January 2005

Persistence of social attention by male and female laboratory rats was examined following exposure to novel conspecifics. In Experiment I we compared performance of castrate females treated with a 10‐day regimen of testosterone propionate to that of intact males and castrate female controls. Testosterone significantly prolonged mean social investigation time. Castrate females treated with a relatively high dosage of testosterone failed to differ from intact males. In Experiment II we compared neonatally andorganized female castrates with castrate male and castrate female controls. Postnatal exposure to testosterone increased sensitivity of females to exogenous testosterone in maturity as measured by persistence of social investigation. In Experiment III we compared investigation time of intact and castrated males and females at 10‐day intervals from 40 to 80 days of age. Intact males investigated novel conspecifics significantly longer than other groups, with longest investigation times at 60 and 70 days of age. In Experiment IV we compared investigation times of 30‐day, 60‐day, and 200‐day‐old males. Sixty‐day‐old males investigated significantly longer than 30‐day‐old or 200‐day‐old groups, which failed to differ from each other. The combined results demonstrate a gender and aggregated effect of testosterone on persistence of social investigation.
Effects of environmental enrichment on old mice
Authors: Warren J. M. , Zerweck C. , Anthony A.
Published: January 2005

Fifteen male C57BL/6J mice, exposed to an enriched environment from age 600 to 750 days, were compared with 15 matched controls on 4 learning problems and an activity test. The enriched mice were significantly superior on an incidental learning and a food‐seeking task, but did not differ significantly from controls on a brightness discrimination task, the Lashley III maze and an activity test. The relative abundance of high and low ribonucleic acid‐containing cerebrocortical cells differed significantly between groups; the enriched mice had more cells with very high levels of RNA. The mammalian brain appears to remain responsive to environmental enrichment well into advanced age.
Early stress effects on growth and adult behavior in Poecilia reticulata
Authors: Newton Barbara J.
Published: January 2005

Small mammals subjected to early stress show decreased aggression and emotionality, accelerated rates of maturation, and increased sexual activity, affiliation, and size. The purpose of this experiment was to test the phyletic generality of this phenomenon using fish (Poecilia reticulata) and, also, to control for the sensitivity of the measures, to determine if controls for both water quality and rearing‐testing conditions might produce different effects than have previously been reported for fish, and to see in what respects the effects of isolation and crowding are similar to those generally found in mammals. Early‐stressed guppies showed reduced aggression, but did not differ from controls on any other measure. Isolated and crowded guppies differed from each other and from the controls on 4 of the 6 measures. Isolated fish matured more rapidly and attained greater adult length than did the controls; the reverse was true for crowded fish. Crowded fish showed higher levels of emotionality than controls, whereas isolates showed lower levels than controls. No differences were noted in affiliation, although crowded fish spent more time in the vicinity of empty stimulus boxes. Crowded fish did not differ from controls in levels of sexual activity or display, but isolated fish showed low levels of sexual activity and high levels of display. These findings suggest that at least part of the early stress phenomenon shown in small mammals may be demonstrated in fish.
The contribution of ambient temperature to suckling behavior in rats 3–20 days of age
Authors: Cramer Catherine P. , Blass Elliott M.
Published: January 2005

To assess the role of ambient temperature on the expression of adultlike control over suckling behavior of infant rats, preweanling pups were tested for nipple attachment and milk intake while suckling in either room temperature (25°C) or nest temperature (34°C). In one experiment, attachment latency was measured following 0, 4, or 24 hr of deprivation at 3, 6, 9, 12, or 15 days of age. Latency was generally reduced by testing in high ambient temperature. Increasing deprivation reduced latency at all ages. Elevated temperature, however, did not accentuate deprivation‐dependent differences. In a 2nd experiment, milk intake via a posterior tongue cannula was measured in pups 5, 10, 15, or 20 days of age, suckling at either room or nest temperature. Environmental temperature did not significantly affect intake at any age. These data eliminate ambient temperature as a critical factor for adultlike control of suckling behavior in infant rats.
Delay and acceleration of puberty in female mice by urinary chemosignals from other females
Authors: Drickamer Lee C.
Published: January 2005

A sequence of 7 experiments tested various aspects of the acceleration and delay of sexual maturation in young female mice as affected by cues from other females: Singly caged females produce the maturation‐delaying chemosignal when exposed to urine from grouped females. Urine from females housed 3 or more/cage produces delays in puberty for young females. Urine from females in estrus accelerates puberty in young females relative to untreated controls or urine from nonestrous females. The delay‐of‐maturation phenomenon in female mice is not affected by reproductive history, cross‐fostering of pups, or varying the cagemates according to whether they are sibs or nonsibs. Taken together these and previous findings suggest that female mice excrete, in their urine, a series of chemicals which act as signals regarding the adequacy of reproductive conditions.
The development of proxemic spacing behavior: Children's distances to surrounding playmates and adults change between 6 months and 5 years of age
Authors: Wesley Burgess J. , McMurphy Denice
Published: January 2005

The patterns of distances maintained between 30 children and 15 adult caretakers were measured to determine developmental trends in children's patterns of interpersonal spacing toward adults and playmates. Children's positions during free play were photographed at 60‐sec intervals and analyzed with a computer to determine the mean distances children maintained toward their 1st through 5th nearest adult caretakers and toward their 1st through 5th nearst playmates. Children's distances from adults increased with age, while distances from playmates and spatial variability decreased with age. Only infants (6–18 months) stayed significantly close to any of their adult caretakers; toddlers (19–27 months) and preschoolers (30–60 months) avoided proximity to their 3rd through 5th nearest adult caretakers more than could be expected by chance. All age groups significantly avoided proximity to their 4th and 5th nearest playmates; avoidance of playmates' space decreased with age.
The separate and combined effects of early undernutrition and environmental complexity at different ages on cerebral measures in rats
Authors: Katz H. B. , Davies C. A.
Published: January 2005

Rats were either undernourished or fed normally during the suckling period, then at 1 and 5 months of age littermates were housed in enriched or impoverished environments for 30 days. The undernutrition caused lasting reductions in the weight and size of the cerebrum and in parameters of the hippocampus, but significant deficits were not observed in the thickness and area of the occipital cortex. Differential housing differed from early undernutrition in that its largest effects were on cortical parameters, but the effects of the two conditions did partly overlap. This meant that some nutritionally induced deficits could be modified later by manipulating environmental complexity. The cerebral response of the previously undernourished rats to differential environments was not distinguishable from that of well‐fed controls on the basis of the gross anatomical changes that were measured. Furthermore, no significant differences were found between the environmental effects in young and mature rats, although the latter's response tended to be somewhat less for most parameters.
Alarm call responsivity of mallard ducklings: I. The acoustical boundary between behavioral inhibition and excitation
Authors: Miller David B.
Published: January 2005

Mallard (Anas platyrhynchos) maternal assembly calls have fast repetition rates (noteslsec,) which promote behavioral excitation in ducklings (i.e., vocalizing, approaching). On the other hand, maternal alarm calls have slow repetition rates, which promote behavioral inhibition (i.e., cessation of vocalizations, “freezing”). This study assesses the nature of the acoustical boundary separating these 2 behavioral states. Maternally naive ducklings were tested to 1 of 2 series of altered alarm calls that either increased or decreased in repetition rate every minute by 2/10 sec. Ducklings in control groups were exposed to a constant repetition rate for comparable periods of time. The inhibitory and disinhibitory responses of ducklings revealed that a relatively sharp acoustical boundary between inhibitory and excitatory repetition rates exists around 2.6 to 2.8 noteslsec. This transitional region happens to coincide with the range within which neither maternal assembly nor maternal alarm calls occur. Thus, there is a genuine match along this acoustical dimension between auditory perception of ducklings and the 2 major species‐typical maternal vocalizations of mallards.
Visceral nociception in developing rats
Authors: Bronstein David M. , Mitteldorf Phillip , Sadeghi Mina M. , Kirby Karen , Lytle Loy D.
Published: January 2005

Maturational changes in visceral nociception were measured in developing or adult rats challenged with hypertonic saline or acetylcholine. Chemically induced abdominal constrictions were absent in rats younger than 7 days of age, regardless of the dose of hypertonic saline or acetylcholine used. Age‐related increases in the percent of animals responding, the number of abdominal constrictions emitted per responder, and total response duration occurred in animals 10‐20 days of age, until adult‐like patterns of responding were attained at the time of weaning. Additional changes in the percent animals responding, as well as in the frequency and total duration of abdominal constriction responses, were also seen in postweanling, but not in preweanling, animals. Five‐day‐old animals did emit audible vocalizations to the intraperitoneal insertion of a hypodermic needle, however, at a time when these animals failed to show observable responses to the noxious visceral stimuli. Hence, mechanisms mediating pain associated with intraperitoneal needle insertion may be functional during the first postnatal week, at a time when mechanisms mediating visceral pain appear to be immature. These differences may be caused by the differential maturation of sensory, neural, or motoric mechanisms important for hypodermic needle insertion versus visceral nociception.
Repeated failure of prenatal ACTH administration to alter masculine behavior in mice
Authors: de Catanzaro Denys , Maerz Marita D. , Heaven Roberta K. B. , Wilson Wendy
Published: January 2005

In four experiments, different preparations and modes of prenatal administration of ACTH all failed to produce any substantial effects upon male sexual behavior in mice. In Experiment 1, CD‐1 females implanted during the third trimester of pregnancy with osmotic pumps releasing varied dosages of ACTH1−24 produced male offspring with essentially normal copulatory behavior. In Experiment 2, prenatal injections of high doses of ACTH1−24 had no effect upon male sexual activity. In Experiment 3, osmotic pumps releasing ACTH1−39 during the third trimester of pregnancy had no effect upon sexual behavior of offspring. However, aggressive behavior was significantly reduced, relative to untreated controls, in offspring of all females implanted with pumps, including those releasing only saline. In Experiment 4, third‐trimester injections of ACTH1−39 in long‐acting gel form had no effect on the sexual behavior or aggression of offspring of C57 strain females. In most of these experiments, ACTH treatment significantly reduced body weight. These results do not confirm previous suggestions that pituitary‐adrenal hormones influence the perinatal differentiation of sexually dimorphic behavior.
Training ducklings in broods interferes with maternal imprinting
Authors: Lickliter Robert , Gottlieb Gilbert
Published: January 2005

Under natural conditions, if maternal imprinting is to occur it must occur in a social situation which includes the presence of broodmates. In the laboratory it has been shown that social rearing with siblings prior to maternal imprinting interferes with the establishment of maternal imprinting, whereas social experience with siblings after maternal imprinting enhances the imprinting experience. The present study examined the influence of social experience with broodmates during an imprinting trial on the establishment of a visually imprinted maternal preference in domestic mallard ducklings (Anas platyrhynchos). Twenty‐four‐hour‐old ducklings were allowed to follow a stuffed mallard hen for 30 min either individually or in a brood of four same‐aged ducklings. The birds trained alone subsequently showed an imprinted preference for the familiar mallard hen over an unfamiliar pintail hen or four stuffed ducklings in simultaneous choice tests at 48 and 72 hr after hatching. Ducklings trained with broodmates did not show a preference for the familiar mallard hen over the unfamiliar pintail hen and displayed a preference for the stuffed ducklings over the mallard hen at 48 and 72 hr choice tests. These results demonstrate that even brief (30 min) experience with siblings during a maternal imprinting trial results in peer imprinting that interferes with the establishment of maternal imprinting. These and other results of a similar sort render dubious the significance of most laboratory studies of imprinting for an understanding of such events in nature.
Maternal and nutritional contributions to infant rats' activational responses to ingestion
Authors: Bornstein Brian H. , Terry Leslie M. , Browde Joseph A. , Assimon Sue Ann , Hall W. G.
Published: January 2005

Infant rats deprived of food, maternal care, and the opportunity to suckle display a dramatic behavioral activation and vigorously ingest when provided milk through oral cannulas. These experiments assessed which components of deprivation are important in producing these responses to milk. Nutritional deprivation alone, with or without the presence of an active maternal female, appears to be sufficient to produce ingestion. Behavioral activation, on the other hand, appears to require both nutritional deprivation and deprivation from a maternal female. The effect of maternal stimulation on later behavioral reactivity was not a function of the pups' opportunity to suckle. However, active maternal stimulation was more effective in preventing activation than was passive maternal stimulation (e.g., thermotactile and olfactory stimulation). Stimulation provided by an active, nonlactating mother was effective in preventing behavioral activation, but the effect was short‐lived, lasting only 2 hr after the pup was removed from the mother's care. This series of studies thus reveals that identified components of maternal separation have dissociable effects on appetitively motivated behaviors in infant rats.
Sapid savvy in sucklings: The effect of quinine hydrochloride on intraoral negative pressure and intake by 11–13‐day‐old rat pups
Authors: Pelchat Marcia Levin , Brake Stephen C.
Published: January 2005

Three experiments describe the consummatory behavior of 11–13‐day‐old rat pups during and following experience with a model aversive taste, quinine hydrochloride. Pups were observed while away from the dam and while suckling. Results show that pups actively reject quinine adulterated solutions in both situations. They do so by spitting the solution from the mouth when away from the nipple and by leaving the nipple and/or decreasing their sucking effort when with the dam.
Stimulus duration as an age‐dependent factor in reflex blinking
Authors: Anthony Bruno J. , Zeigler Bonnie L. , Graham Frances K.
Published: January 2005

Alternative hypotheses of differential development of auditory and visual systems versus temporal‐processing systems were tested to explain prior adult–infant differences in reflex blink latency. The present study removed a confound between stimulus modality and duration, present in prior work, and determined whether age interacted with modality or with duration when they were varied orthogonally. Reflexes were elicited from human adults and infants under 4 stimulus conditions: flash and click, delivered singly and in trains. Age interacted only with duration to affect latency and elicitation probability, reflex characteristics which depend on adequate triggering by a transient change at onset. In contrast, age did not interact with duration to affect peak amplitude which presumably depends on temporal integration. Findings are compatible with the hypothesis that processes or structures, specialized for differentiation of transient stimulus change, mature at a different rate than those specialized for integration of stimulus energy over time.
Olfactory influences on the ingestive behavior of infant rats
Authors: Terry Leslie M. , Johanson Ingrid B.
Published: January 2005

Twenty‐four‐hour deprived infant rats from 1 to 12 days of age were exposed to the odor of milk, either by itself or accompanied by oral infusions of water, sucrose, quinine, or milk (Experiment 1). Pups from 3 to 9 days of age became behaviorally active, and mouthed and probed in response to the odor of milk, even in the absence of oral infusions. Six‐ and 9‐day‐old pups also increased their intake of various test solutions in the presence of milk odor. This responsiveness to milk odor was not seen in 1‐day‐old pups, and waned by 12 days of age. Other stimulus odors that were presented in the same context (Experiment 2) failed to elicit such intense behavioral activation, indicating that there was some degree of specificity in the responsiveness to milk odor. Finally, 2 manipulations that influence pups' ingestion of milk, deprivation and ambient temperature, were found to influence pups' responses to milk odor (Experiment 3).
Intersensory coordination and the effects of early sensory deprivation
Authors: Tees Richard C. , Symons Lawrence A.
Published: January 2005

The effect of early visual deprivation on the ability of dark‐ (DR) and light‐reared (LR) rats to learn temporal discriminations involving sounds and lights and to abstract the intersensory correspondence involving duration from initial modality‐specific training was examined in this study. While visually inexperienced DR rats were somewhat less successful in acquiring an initial discrimination involving visual events and responding to a rule reversal per se, they were as effective as their visually experienced LR counterparts in demonstrating cross‐modal transfer (CMT) to signals in a new modality. The results revealed by the investigation are discussed in terms of the consequences and lack of consequences of the manipulation of early visual experience on the ontogeny of intersensory perceptual development in mammals.
Alarm call responsivity of mallard ducklings: V. Age‐related changes in repetition rate specificity and behavioral inhibition
Authors: Miller David B. , Blaich Charles F.
Published: January 2005

Twenty‐four‐hour‐old mallard ducklings (Anas platyrhynchos) exhibit a high degree of behavioral freezing (i.e., vocal and locomotor inhibition) upon hearing the maternal alarm call, which the hen utters when potential predators are near the nest. In this study, we assessed age‐related changes in alarm call responsivity between 12 and 72 hr after hatching. Experiment 1 revealed that, although a significant reduction in vocal activity occurred upon exposure to the alarm call at all ages tested (12, 24, 36, 48, 60, 72 hr), birds older than 48 hr exhibited lower levels of freezing than younger birds. Furthermore, 12‐hr‐old ducklings exhibited the greatest level of freezing among the younger‐aged groups. In Experiement 2, 12‐, and 72‐hr‐old ducklings were tested to variations of the alarm call that differed in repetition rate (0.2 to 2.6 notes/sec, in increments of 2/10 of a second) to ascertain whether there are age‐related changes in perceptual specificity and whether ducklings exhibit perceptual sharpening. Although older ducklings exhibited a slight shift in perceptual specificity toward faster repetition rates, they froze significantly less than younger ducklings at all repetition rates. Therefore, there was no evidence of perceptual sharpening. These data suggest that alarm call responsivity may represent an adaptation that appears to be associated with the timing of the nest exodus.
Acquisition and retention of separate elements of a conditioned olfactory discrimination in preweanling rats
Authors: Serwatka Joseph , Spear Norman E.
Published: January 2005

Acquisition and retention of separate elements of an olfactory discrimination were tested in 15‐and 20‐day‐old preweanling rats. Four or 8 conditioning trials were given in Experiment 1. Each rat was presented one odor always followed by footshock (CS+) and another never paired with footshock (CS‐). Conditioning to both stimuli was assessed through 3 types of olfactory preference tests involving comparison between CS+ and a novel odor, CS− and a novel odor, or CS+ and CS−. The results indicated that for 15‐ and 20‐day‐olds, both stimuli become excitatory early in training; further conditioning trials diminished the excitation previously accrued to the CS−, and the olfactory discrimination became apparent. When levels of conditioning were equated, retention was tested after intervals of 4 min, 3 days, or 8 days (Exp. 2). Rate of forgetting was more rapid for the 15‐day‐olds, but both ages of subjects showed similar patterns of forgetting, which included a progressive decrease in the aversion to the CS+ but an increase in aversion to the CS−.
Gender differences in caring for infant Cebuella pygmaea: The role of infant age and relatedness
Authors: Wamboldt Marianne Z. , Gelhard Robert E. , Insel Thomas R.
Published: January 2005

This paper describes a three‐part study of the parenting behaviors of 6 family groups of Cebuella pygmaea (pygmy marmosets). In the first part, the parenting patterns of undisturbed family groups housed under laboratory conditions were scored throughout the first 10 weeks following the birth of their second infant(s). To further investigate the role of infant age in determining parental behavior, caretaking patterns were studied after a brief separation of infants of varying ages from their families. Finally, an unrelated infant, age 1–5 weeks, was placed inside the home cage of each family, and caretaking of this novel infant was scored. The main findings that emerged from the study were: (1) sex differences in carrying the infants were dependent upon the age of the infant, i.e., adult females were the predominant carriers of infants /3 weeks of age and males (either adult or juvenile) the main carriers for infants >3 weeks of age; (2) some caretaking behaviors, e.g., grooming and protective retrieval, were performed predominantly by the adult females throughout infancy; and (3) the relatedness of the infant, i.e., one's own vs. another's, appeared to primarily affect the behavior of adult females. In general, experimental manipulations confirmed results of the observational part of the study and thus may be useful paradigms for testing specific hypotheses about parental behaviors.
Physical stimulation reduces the brain temperature of infant rats
Authors: Sullivan Regina M. , Wilson Donald A. , Leon Michael
Published: January 2005

Previous work indicated that physical stimulation, such as that which mimics the stimulation pups receive from the dam, reduces pup body temperature. The present paper reports that the body and brain temperature of 5‐day‐old pups covaried under steady‐state thermal conditions, cold exposure, and warmth exposure (Expt. 1) suggesting that body thermoregulatory mechanisms may also regulate brain temperature. Indeed, physically stimulating pups decreased brain temperature in the neocortex (Expt. 2) and the olfactory bulb (Expt. 3). The mechanism for this brain temperature decrease appears to be an increase in ventilatory heat exchange, the same mechanism responsible for the decrease in body temperature. Pups increased respiration during stimulation, thereby increasing air flow to the lungs where convective and evaporative heat exchange occurred. Indeed, stimulating pups in a high‐humidity environment blocked the decrease in brain temperature (Expt. 4). The ability of physical stimulation to decrease brain temperature appears to be limited to neonatal pups, as 10‐, 15‐, and 20‐day‐old pups did not exhibit a brain temperature decrease in response to stimulation (Expt. 5).
Auditory evoked heart rate responses in pigtailed macaques (Macaca nemestrina) raised in isolation
Authors: Martin Robert E. , Sackett Gene P. , Gunderson Virginia M. , Goodlin‐Jones Beth L.
Published: January 2005

Heart rate (HR) responses evoked by 1 sec of 85‐dB white noise were studied in 12 1‐year‐old pigtailed macaques, 6 of which were raised in social isolation and 6 with mothers and peers. Tests were given for 5 days, with 25 trials each day. Although baseline HR did not differ between groups, the pattern of change from baseline was not the same. Isolates showed only HR acceleration, returning to baseline within 10–11 sec of stimulus onset. Socially reared monkeys had a 10‐ to 11‐sec biphasic response of acceleration followed by deceleration, with subsequent return to baseline. The same group difference in HR pattern occurred when subjects were tested with a less intense 65‐dB stimulus. These findings were discussed in terms of activity, emotionality, and autonomic regulatory functions. It was concluded that early rearing experiences may affect later physiological processes involving autonomic nervous system balance. This conclusion was related to observations of persistent individual differences in HR by human children classified as inhibited.
Prenatal antagonism of stress by naltrexone administration: Early and long‐lasting effects on emotional behaviors in mice
Authors: D'Amato F. R. , Castellano C. , Ammassari‐Teule M. , Oliverio A.
Published: January 2005

The effects of prenatal exposure to stress and to naltrexone on emotional behaviors were studied in CD1 mice during ontogeny and in the adulthood. During ontogeny (a) lower body weights were initially found in pups born by mothers injected with naltrexone; (b) treatments did not affect sensory motor development except in the case of the cliff aversion reflex which occurred earlier in pups prenatally exposed to stress; (c) measures of ultrasonic vocalizations in stressful context showed that the amount of vocalizations emitted by pups born by stressed mothers was significantly higher than that emitted by pups born by naltrexone injected and control mothers (d) an examination of motheroffspring interactions on the very first day of observation indicated a consistent trend in stressed mothers to be more responsive to their pups. In adulthood, ultrasonic calls in courtship after short and long periods of isolation showed a time‐dependent decrease of vocalizations in males prenatally exposed to naltrexone. These results indicate that the modifications of emotionality evident during early development are directly related to the reactivity of the mothers to the experimental treatments. Moreover, the long‐term reduction of ultrasonic vocalizations in adult males prenatally exposed to naltrexone shows in these animals a lowered reactivity to stressful contexts which probably results from specific physiological alterations due to the prenatal administration of the opiate antagonist.
Associative processes in differentially reared monkeys (Macaca mulatta): Sensory preconditioning
Authors: Beauchamp Alan J. , Gluck John P.
Published: January 2005

Past research has indicated that with ragard to performance in formal learning test situations, early socially isolated rhesus monkeys display atypical reactions to noxious stimuli, deficits in response inhibition, slower adaptation to reinforcement contingencies, and lower performance on oddity tasks. Twelve adult rhesus monkeys (Macaca mulatta), 6 who had been reared in total isolation for the first 9 months of life 19 years earlier, and 6 socially reared, were tested in a sensory preconditioning paradign. In phase I, two neutral stimuli (S1–S2) were paired in contriguous fashion; in phase II the S2 stimulus was conditioned to elicit a startle response; and in phase III the S1 stimulus was presented to assess whether an association between the two stimuli had been formed during the initial phase. Instead of a deficit, isolate subjects showed significantly more response transfer during phase III as compared to the controls. The superior performance displayed by isolates is viewed as resulting froma slower habituation to S1‐S2 stimuli during preconditioning along with the preservation of responses during testing. These findings support the motion that atypical cognitive processing across a lifespan is a consequence of early social impoverishment.
Sensory determinants of nipple‐attachment behavior in 2–4‐day‐old kittens
Authors: Blass Elliott M. , Shulekina‐Turpaeva Kira , Luschekin Vitalie
Published: January 2005

Fourteen kittens, 2–4 days of age, wee studied on their anesthetized dams for nipple attachment behavior. In agrreement with a previous report (Larson, M.A., & Stein, B. E., 1984, Dev. Psychobiol., 17; 423–436) we find that olfaction contributed rather little to nipple attachment in kittens.
Metamorphosis of behavior in the bullfrog (Rana catesbeiana)
Authors: Stehouwer Donald J.
Published: January 2005

This study describes the development of different spontaneous and elicited behaviors of frogs and their relationship to morphological, physiological, and econological changes of metamorphosis. Tadpoles were studied at all stages of development from STage XVIII, the onset of metamorphosis, to Stage XXV, when metamorphosis of the froglets is complete. Behaviors examined included development of forelimb postural support, postural responses to vestibular stimulation, the hindlimb withdrawal reflex, the corneal reflex, ocular mobility, and habital preference. Results showed that these behaviros differ markedly in their timing and rate of maturation. Forelimb postural support and postural responses to vestibular stimulation improved gradully between Stagez XX and XXV. In contrast, the threshold of the hindlimb withdrawal reflex remained essentially unchanged until Stage XXV, when it increased suddenly and dramatically. The corneal reflex appeared suddenly at Stage XXI with a threshold similar to that of juvenile forgs. The ability to move the eyes in response to visual or vestibulaar stimulation was pronounced it tadpoles, but gradually declined between Stage XIII and Stage XXV, so that froglets showed almost no ocular mobility. The preference of metamoprphosing frogs for deep water, shallow water, shoreline, or land were examined in an aquarium during a 24‐hr observation period using time‐lapse videotape recordings. Results showed that tappoles spent progressively less time in deep water and shallow water as metamorphosis proceeded. Preference for land emerged suddenly at Stage XXII and remainhed high thereafter. There were no stage‐related differences in preferences for the shoreline.
Development of sleep states in normal premature and full‐term newborns
Authors: Curzi‐Dascalova Lilia , Peirano Patricio , Morel‐Kahn Françoise
Published: January 2005

The aims of our study were: (1) to answer the question “Do sleep states exist in normal premature infants;” (2) to anaylze the development of sleep cycle and sleep state characteristics in premature and full‐term newborns. Polygraph recordings were done on 38 normal, appropriate for gestational age newborns, born at 30 to 41 weeks (w) of gestation. All infants fell asleep in active sleep (AS). Postwaking AS was significantly shorter than the next AS. Mean sleep cycle duration increased from approximately 46 min at 31–34 w of conceptional age (CA) to 70 min. at 35–36 w CA. In all infants we observed stable, >5 min AS and quiet sleep (QS) periods, as defined by EEG and REM criteria. Indeterminate sleep was about 30% of the total sleep cycle at 31–34 w; it decreased to 12% at 35–36 w. Both duration and percentage of AS and QS significantly increased at 35–36 w and remained stable up to 39–41 w CA. Values of QS were significantly reduced when defined by additional criteria (respiratory rate, tonic chin EMG or motility). Concordance of QS criteria was not significantly better in older versus younger groups of infants. At all ages, AS values were insensitive to changes in the criteria chosen to define them. The contrast, starting from 31–34 w CA, between AS and QS as defined by EEG and REM criteria could account for state differences in the control of many physiological variables in prematures.
Alarm call responsivity of mallard ducklings: VII. Auditory experience maintains freezing
Authors: Miller David B. , Blaich Charles F.
Published: January 2005

Mallard ducklings (Anas platyrhynchos) freeze upon hearing the maternal alarm call, which the hen issues when there are disturbances (e.g., potential predators) near the nest. Our previous work indicates that ducklings that have been devocalized embryonically and reared in auditory isolation exhibit a significant reduction in the incidence of freezing, as compared to vocal ducklings or to devocal ducklings that have been exposed to duckling sounds throughout the perinatal period up to the time of testing at 12 hr posthatch. The main purpose of this paper is to assess whether there is a prenatal or postanatal sensitive period for such auditory experience. Two groups of 30 devocalized ducklings were either (a) stimulated with duckling sounds prenatally and tested to the alarm call at 12 hr posthatch (Expt. 1), or (b) stimulated from the time of hatching to the time of testing at 12 hr (Expt. 2). These experiments rendered no conclusive evidence of either a prenatal or postnatal sensitive period, but they suggested that auditory experience might be important in maintaining freezing. To test this hypothesis, a third group of 30 ducklings was stimulated from hatching to 12 hr and tested at 24 hr (Expt. 3). Only those ducklings receiving auditory experience contiguous with the time of testing (Expt. 2) showed high levels of freezing. Whenever a gap occurred between the offset of stimulation and the onset of testing (Expts. 1 and 3), the incidence of freezing dropped. Thus, auditory experience is important in maintaining the freezing response. This effect contrasts markedly with traditional conceptions of sensitive periods.
Neonatal sex‐steroid hormones and cognitive abilities at six years
Authors: Jacklin Carol Nagy , Wilcox Karen Thompson , Maccoby Eleanore E.
Published: January 2005

Five sex‐steroid hormones (testosterone, androstenedione, estradiol, estrone, and progesterone) were assayed in umbilical cord blood. Cognitive abilities were assessed as a part of a 6‐year follow‐up laboratory visit. Four subtests were given: reading, numbers, listening, and spatial ability. There were no sinificant differences between boys and girls in cognitive ability scores. Higher levels of perinatal androgens (testosterone and androstenedione) were significantly associated with low age‐6 spatial ability in girls. Multiple regression analyses revealed a significant proportion of the variance in cognitive abilities in girls could be accounted for by testosterone and androstenedione. No significant predictions were found for boys. The finding of a stable inverse association between sex and effect of hormones on abilities is discussed.
Effect of maternal presence on the fear response to an unfamiliar environment as measured by heart rate in rats as a function of age
Authors: Richardson Rick , Siegel Michael A. , Campbell Byron A.
Published: January 2005

Rats 16 to 60 days of age were placed in an unfamiliar environment either alone or in the presence of an anesthetized lactating dam. Rats of all ages show a dramatic increase in fear, as measured by heart rate (HR), when placed alone in an unfamiliar environment. Adult rats, however, show a rapid decline in heart rate during the course of a 90‐min session, whereas 16‐day‐old rats show no significant decrease in HR during the same period. These results suggest that the adult rats become less fearful of the test environment over time, but that the 16‐day‐olds maintain a high level of fear throughout the 90‐min test period. Twenty‐three‐ and 30‐day‐old rats show an adultlike pattern of adaptation to the unfamiliar environment, i.e., their heart rates return partially but not completely to baseline levels within the 90‐min session.

When an anesthetized lactating dam is present in the test environment, a strikingly different pattern of results is obtained. Heart rate in the 16‐day‐old rat is immediately reduced to near baseline levels whereas in the young adult (60‐day‐old) rat the presence of the anesthetized dam has no effect on either initial HR or rate of adaptation. Again the 23‐ and 30‐day‐old rats showed an intermediate pattern of adaptation.

In two follow‐up experiments the effects of adding (Expt. 2) or removing (Expt. 3) an anesthetized dam on the 16‐day‐old rats' response to an unfamiliar environment was examined. Both experiments showed that animals were more fearful when the dam was absent from the environment than when it was present.
The ontogeny of exploratory behavior in the house rat (Rattus rattus): The mobility gradient
Authors: Eilam David , Golani Ilan
Published: January 2005

Infants of rats and other mammals respond to a novel environment by becoming immobile, and then showing a process of motorial expansion called “warm‐up.” Starting from immobility, new types of movement are incorporated into the stream of behavior according to rather strict rules of order. Once a new type of movement has been performed, the infant reverts to it repeatedly. As a result, the earlier portion of the behavior appears stereotyped, giving the impression of an automatism. Later, as new types of movement are added to the infant's repertoire, the movement becomes increasingly rich and unpredictable, giving the impression of “free” behavior. The same rules of order operate within “warm‐up” sequences of movement, and across such sequences, day by day. Concurrently, there is an increase in the amplitude of movements, resulting in a gradual expansion of the portion of the environment explored by the infant. The same rules of order seem to operate in the development of locomotion in more primitive vertebrates. In rats under the action of psychoactive drugs, the “warm‐up” sequence is performed in reverse.
Early experience and maternal behavior in rats
Authors: Brunelli Susan A. , Shindledecker Richard D. , Hofer Myron A.
Published: January 2005

This study examined the effects of early experience (early weaning with group housing in sibling groups (EG), or early weaning plus social isolation (El) from 14 to 24 days of age) on maternal, play, and social behaviors expressed during 5 days of sensitization at 24 days, and then later at 100 days of age. Our results showed that maternal behaviors at 24 days could be altered by these early experiences. At 24 days of age fewer EI animals retrieved compared with normally weaned controls (NW), but more showed play behavior in the presence of pups. EG animals showed intermediate levels of retrieving relative to NW controls, and no concomitant changes in play behaviors. When retested as adults, females in all groups showed similar levels of all maternal behaviors. But EI adults of both sexes showed persistent intrusion of play behaviors, and higher levels of rearing and undirected activity in the presistent intrusion of play behaviors, and higher levels of rearing and undirected activity in the presence of neonates. Factor analyses revealed that previously sensitized adult males showed patterns of organization of maternal behaviors that resembled adult females rather than those shown by control males reared without sensitization experience. Previously sensitized females also showed a retention of the play behavior patterns characteristic of juveniles, not present in females without sensitization experience. These results show that social experience during the weaning period can affect the development of maternal and play behavior elicited by neonates during the juvenile period that persist into adulthood, and that juvenile sensitization experience exerts longterm effects on adult patterns of maternal behavior in both sexes.
Ontogeny of renin‐induced salt appetite in the rat pup
Authors: Leshem Micah , Epstein Alan N.
Published: January 2005

Intracerebroventricular injections of renin in suckling rat pups increased intake of NaCl solutions when they were orally infused 5 hr after injection. The appetite for saline solution was evident in pups as young as 3 days, was greater in females, and was specific insofar as intake of milk, either by suckling or by oral infusion, was not affected. Three‐day‐old pups increased intake only to 12% NaCl, the acceptable concentration of NaCl becoming lower in older pups. These results suggest, first, that, as is true for feeding and drinking, the brain mechanism for salt appetite is competent for expression of the behavior in the very young rat pup, and second, that its angiotensinergic neural substrate is distinct from that which mediates the dipsogenic effect of the hormone.
Maternal and peer imprinting in mallard ducklings under experimentally simulated natural social conditions
Authors: Dyer Antoinette B. , Lickliter Robert , Gottlieb Gilbert
Published: January 2005

Previous studies revealed that if socially reared mallard duckling actively follow a stuffed mallard (Anas platyrhynchos) hen, they later show a visual preference for the familiar mallard mallard hen over an unfamiliar redhead (Aythya americana) hen. The present study determined that the experience of actively following the hen is essential to the induction of a visually controlled, species‐typical, maternal preference. Domestic mallard ducklings that had not been given the opportunity to follow the mallard hen were “passively” reared in social groups consisting of a stuffed mallard hen and seven same‐aged siblings for either 24, 48, or 72 hr after hatching. These birds were largely unresponsive to the hen in a later choice test, even when they were passively exposed to the mallard hen for as long as 72 hr prior to testing. The question arose as to whether passive exposure to the ducklings induced a preference for them that interfered with establishment of maternal imprinting under these simulated natural nest conditions. Results indicated that socially reared ducklings do prefer stuffed ducklings to a stuffed mallard hen in a simultaneous choice test even when the hen is present and vocalizing during social rearing. Further, even ducklings reared individually with the mallard hen were unresponsive to her in the lter choice test. That there is something special about the stimulation provided by ducklings was further demonstrated by the finding that stuffed ducklings were preferred over the mallard hen (1) when the social rearing situation precluded active physical interaction with live ducklings and (2) when reared with inanimate stuffed ducklings. Thus, the ineffectiveness of the stuffed mallard hen in inducing visual imprinting under simulated nesting conditions cannot be attributed to the fact that she was not alive or reciprocally interactive. The present results suggest that mallard ducklings do not become visually imprinted to their hen until after departure from the nest, that the visual component of maternal imprinting likely involves active following subsequent to nest departure, and that early in postnatal development siblings are more visually attractive than is the hen.
Iris pigmentation and sociability in childhood: A re‐examination
Authors: Rubin Kenneth H. , Both Lilly
Published: January 2005

Drawing from Rosenberg and Kagan's (1987) finding of an association between iris pigmentation and behavioral inhibition in early childhood, we sought, in the present investigation, to examine the developmental relation between eye color and social withdrawal in kindergarteners and children in grades 2 and 4. In kindergarten and grade 2, blue‐eyed children were found to be overrepresented in groups of extremely withdrawn youngsters. No association was found between eye color and withdrawal in grade 4 or between eye color and extreme sociability at any grade. The results were interpreted as suggestive of the increasing role, with age, of social factors in the determination of extremely inhibited behavior.