Showing papers in "Developmental Psychobiology in 1983"
TL;DR: Periadolescent rats are hyperactive and engage in more conspecific play behavior than younger or older rats, but perform poorly in more complex appetitive and avoidance learning tasks in which increases in locomotor activity do not improve performance, perhaps as a result of age-specific alterations in selective attention or stimulus processing.
Abstract: The behavior and psychopharmacological sensitivity of periadolescent rats are examined in this review. Periadolescent rats are hyperactive and engage in more conspecific play behavior than younger or older rats. When compared with other-aged rats, periadolescents exhibit enhanced performance in simple active-avoidance learning tasks, but perform poorly in more complex appetitive and avoidance learning tasks in which increases in locomotor activity do not improve performance, perhaps as a result of age-specific alterations in selective attention or stimulus processing. Such behavioral "anomalies" of periadolescent animals observed in traditional laboratory situations may be in some way adaptive when considered in the context of the animals' natural habitat. In terms of psychopharmacological responsiveness, periadolescent rats, when compared with younger or older animals, are less sensitive to catecholaminergic agonists but are more responsive to the catecholaminergic antagonist haloperidol. This pattern of psychopharmacological sensitivity suggests that the catecholaminergic systems may be temporarily hyposensitive during the periadolescent period. Evidence is presented that a negative feedback system in the form of dopamine autoreceptors may become functionally mature in mesolimbic brain regions during the periadolescent period. The possibility is presented that maturation of these self-inhibitory autoreceptors might result in a temporary decrease in the efficacy of mesolimbic dopamine projections, perhaps contributing to the psychopharmacological and behavioral characteristics of periadolescent animals. In support of this suggestion, evidence is reviewed indicating that the behavior of adult animals with lesions of the ventral tegmental area, a region containing cell bodies from which these mesolimbic dopaminergic projections originate, resembles that of periadolescent rats.
551 citations
TL;DR: It would be interesting to carry out detailed comparisons of the ontogeny of such adjustments in blind-born mammals such as the dog in comparison with mammals that have vision at birth–ungulates, for example.
Abstract: “We should compare the manner in which orientation develops, first to the mother and later to an expanding environment. It would be interesting to carry out detailed comparisons of the ontogeny of such adjustments in blind-born mammals such as the dog in comparison with mammals that have vision at birth–ungulates, for example. Important changes occur in the orientation of blind-born mammals in the presight period, which we do not as yet have the techniques to investigate adequately.”
T.C. Schneirla (1954)
116 citations
TL;DR: It is proposed that asynchronous and asymmetrical maturation of subcortical tracts and/or muscle strength could account for these behavioral shifts in normal human infants.
Abstract: Patterns of interlimb coordination and lateral preference of spontaneous leg kicks were described for 8 normal human infants observed biweekly from 2 to 26 weeks of age. Newborn infants showed a high percentage of alternating movements, which were often supplanted by unilateral movements between 1 and 4 months. Simultaneous (in-phase) kicks matured later than alternating kicks. No consistent lateral preferences were detected. The developmental course was marked by variability and discontinuities within each infant. We propose that asynchronous and asymmetrical maturation of subcortical tracts and/or muscle strength could account for these behavioral shifts.
100 citations
TL;DR: It is concluded that under the conditions of these experiments, the development of sexual preferences of zebra finch males is affected by both parental and sibling influences.
Abstract: Broods of young zebra finches were either raised by their own species or cross-fostered by Bengalese finches. Both were isolated visually from other birds at the age of 2 months. Sexual preferences of males were examined at maturity, in a choice between 1 zebra finch female and 1 Bengalese finch female, by measuring the number of song strophes directed at each. Males raised by their own species sang exclusively for the zebra finch female. Cross-fostered males raised without siblings or with only 1 sibling sand exclusively for the Bengalese finch female. A large number of cross-fostered males raised with 2-4 siblings showed at least 5% singing for the zebra finch female, and a small number did so predominantly. It is concluded that under the conditions of these experiments, the development of sexual preferences of zebra finch males is affected by both parental and sibling influences. It is possible that the earlier evidence for a predisposition to response to conspecifics put forward by Immelmann could be explained by hitherto uncontrolled differences in experience.
86 citations
TL;DR: During social play some locomotor-rotational movements were found to have immediate functions, such as achieving advantage over the partner during play-fighting, and as a means of terminating sensory input from the partner at the end of social contact.
Abstract: During postnatal development, young laboratory rats, Rattus norvegicus, exhibit a variety of locomotor-rotational movements, that is, runs and jerk-jumps, in both playful and nonplayful contexts. The frequency of movement types differed between contexts. Some contexts, such as exploration and sleeping, contained spontaneously (i.e., possible eliciting stimuli were not observed) occurring jerk-jumps which varied with increasing age. In some contexts, such as social play, in which locomotor-rotational movements were elicited by observed stimuli, the frequency of jerk-jumps remained similar throughout ontogeny. During social play some locomotor-rotational movements were found to have immediate functions, such as achieving advantage over the partner during play-fighting, and as a means of terminating sensory input from the partner at the end of social contact.
73 citations
TL;DR: 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.
Abstract: 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 age 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.
68 citations
TL;DR: In Experiment I, handling or electric shock of 2-day-old rat pups triggered pituitary-adrenocortical activity and handled or shocked pups that were returned to a mother-absent nest were subsequently found to be less responsive to ACTH injection than were pups returned toA mother-present next following treatment.
Abstract: In Experiment I, handling or electric shock of 2-day-old rat pups triggered pituitary-adrenocortical activity. Interaction between mother and litter after pup treatment affected the magnitude and the time course of the pups' adrenocortical response. Mother-infant interactions following pup treatment on Day 2 were found to affect the responsiveness of pups to later stimulation. In Experiment II handled or shocked pups that were returned to a mother-absent nest were subsequently found to be less responsive to ACTH injection than were pups returned to a mother-present nest following treatment. These data are discussed in terms of the reciprocity and synchrony in mother-infant interactions and the Maternal Mediation hypothesis of early experience.
61 citations
TL;DR: The present studies characterize the developmental course of saline preference during maturation in the rat and examine whether adult saline preference is influenced by postweaning exposure to saline solutions, failing to reveal any evidence that rearing condition affects adult salt preference.
Abstract: The degree to which adult taste preferences can be influenced by early taste exposure is a matter of some debate. The present studies characterize the developmental course of saline preference during maturation in the rat and examine whether adult saline preference is influenced by postweaning exposure to saline solutions. Saline intake from weaning to adulthood was examined in Wister rats allowed continuous access to demineralized water and either.0,.9, 1.8, or 2.7% sodium chloride (NaCl) w/v solutions. When rats were immature they expressed greater preference for saline solutions than they did as adults. It is hypothesized that the over consumption of saline by young animals is related to lower sensitivity of the taste system to NaCl in the early postweaning period. Animals that had had continuous access to saline from weaning were compared to those that had not received saline exposure early in life, in life, in order to determine whether extensive experience with salt solutions leads to alterations in adult salt preference. These studies failed to reveal any evidence that rearing condition affects adult salt preference; thus adult salt preference may be maturationally determined and relatively independent of postweaning environmental influences.
59 citations
TL;DR: An across-age timidity score is computed which shows significant correlations with neonatal progesterone, testosterone, and estradiol for boys, but is not significantly predicted by hormone concentrations in girls.
Abstract: Five sex-steroid hormones (testosterone, androstenedione, estradiol, estrone, and progesterone) are assayed in umbilical cord blood. Timidity is assessed in home and laboratory observations by reactions to a range of novel toys in children from 6 to 18 months of age. Significant short- (1 week) and long- (several months) term stability in timidity is demonstrated. Girls have higher mean scores on observed timidity than do boys in 2 of the 3 samples tested. An across-age timidity score is computed which shows significant correlations with neonatal progesterone, testosterone, and estradiol for boys, but is not significantly predicted by hormone concentrations in girls.
50 citations
TL;DR: The modifiability of the brown-headed female cowbird's response to male song is investigated, and data on song perception are contrasted with those previously obtained for male production and indicate different constraints onsong perception as opposed to song production.
Abstract: To investigate the modifiability of the brown-headed female cowbird's (Molothrus ater ater) response to male song, we reared M.a. ater females with either M.a. ater or M.a. obscurus males, whose songs differ in geographic origin. The females were later tested for their responsiveness to playbacks of M.a. ater and M.a. obscurus song. Rearing with M.a. obscurus males had no effect on the female's preference for her native song variant, suggesting a closed program for receptive development. The data on song perception are contrasted with those previously obtained for male production and indicate different constraints on song perception as opposed to song production.
50 citations
TL;DR: 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 with pictures as stimuli, demonstrating that 3-month-old pigtail infants could discriminate among faces of adult females of all 3 species.
Abstract: 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.
TL;DR: There was little evidence for any interaction between the nutritional and environmental variables, but all trends were in the direction of the environmental treatment having more effect on the well-nourished rats.
Abstract: A factorial design was used to explore the influence of malnutrition and environmental enrichment on brain development and adult behavior. Malnutrition in suckling rats was produced by restricting the intake of their dams to 40% of normal food consumption. Environment was enriched using combined preweaning handling and a postweaning complex environment treatment. Malnutrition produced lasting effects upon brain biochemical composition and behavior. The environmental manipulation had no ameliorative effect on the brain parameters measured but it had pronounced effects on behavior, decreasing latency to move in the open field and increasing some measures of activity while it enhanced passive-avoidance performance. There was little evidence for any interaction between the nutritional and environmental variables, but all trends were in the direction of the environmental treatment having more effect on the well-nourished rats.
TL;DR: In this paper, human parents were asked to identify their infants on the basis of tape-recorded cries that they had not previously heard, and the results indicated that parents' recognition was not based on extraneous cues and that overall, the foils were appropriate distractors in the parents' task.
Abstract: Human parents were asked to identify their infants on the basis of tape-recorded cries that they had not previously heard. The cries of twenty 30-day-old infants were recorded just prior to a feeding, then rerecorded onto a test tape containing cries from three other infants. Eighty percent of mothers were able to recognize their infants' cries, as were 45% of fathers. An additional 140 adults (non-parents) were tested in order to determine if the process of dubbing cries onto test tapes had left extraneous auditory cues to infants' identities and if the foil infants were equally discriminable. The results indicated that parents' recognition was not based on extraneous cues and that, overall, the foils were appropriate distractors in the parents' task. Thus, the majority of parents can recognize their 30-day-old infants on the sole basis of acoustic cues contained in the infants' cries. The acoustic features that underlie this recognition are now being investigated.
TL;DR: The reproductive behavior and physiology of female offspring of rats stressed during pregnancy were assessed and showed evidence of normal cyclicity, sexual behavior, pregnancy, parturition, pup survival, and maternal behavior.
Abstract: The reproductive behavior and physiology of female offspring of rats stressed during pregnancy were assessed. Mothers were restrained and placed under bright, hot lights from Day 14 through 21 of gestation. This treatment, which is known to disrupt the sexual behavior of male offspring, did not alter reproductive functioning in the female offspring. The females showed evidence of normal cyclicity, sexual behavior, pregnancy, parturition, pup survival, and maternal behavior when tested beginning at 70 or at 140 days of age.
TL;DR: 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, and 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.
Abstract: 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.
TL;DR: The data suggest that autonomic activity during the early months of life may be affected by both prematurity and postnatal illness, and the significance of these data in understanding term/preterm differences in the neonatal period is discussed.
Abstract: In order to investigate the development of autonomic control and its relation to postnatal illness, healthy term, healthy preterm, and preterm infants who had recovered from respiratory distress syndrome (RDS) were seen around the expected date of their birth, 40 weeks conceptional age (C.A.), and again at 3 months conceptional age. Three minutes of resting EKG were collected at each age point while the infant was in a quiet, alert state. Measures of resting heart period and heart period variability were derived. Results revealed the influence of maturity and illness on autonomic activity. RDS and healthy preterm infants, at 40 weeks C.A. exhibited a pattern of small heart period compared to healthy term. RDS preterm infants at 40 weeks C.A. exhibited less overall variability than either healthy group and across age displayed less short-term variability than the healthy infants. The data suggest that autonomic activity during the early months of life may be affected by both pre-maturity and postnatal illness. The significance of these data in understanding term/preterm differences in the neonatal period is discussed.
TL;DR: The present experiments provide no evidence that hippocampal function is impaired as a consequence of early protein deprivation, and a critical review of earlier studied of undernourished rats supports a similar conclusion.
Abstract: Much of the development of the rat's hippocampal formation occurs postnatally which suggests that this structure, like the cerebellum, may be especially vulnerable to early postnatal malnutrition. Radial-maze performance and spontaneous alternation, two kinds of behavior requiring the integrity of the hippocampus, were assessed to determine whether hippocample function in the adult rat is mipaied as a result of protein restriction in either the prewaning, the postweaning or both stages of development. In three experiments the perormance of protein-malnoruished rats in 8- and 12-arm mazes did not differ significantly from that of well-nourished rats. In a fourth experiment levels of spontaneous alternation in protein-malnourished rats were like those of normal well-nourished animals. Thus, The present experiments provide no evidence that hippocampal function is impaired as a consequence of early experiments provide no evidence that hippocampal function is impaired as a consequence of early protein deprivation. For the most part, a critical review of earlier studies of undernourished rats supports a similar conclusion.
TL;DR: When tested as adults, PBN rats were hypodipsic in response to extracellular fluid volume depletion, they displayed alterations in sodium appetite, showed "exaggerated" preferences and aversions to saccharin and NaCl solutions, and they displayed attenuated quinine aversions.
Abstract: Ten-day-old rats sustained bilateral electrolytic lesions of the parabrachial nuclei in the pons (PBN). Growth measures and tests of sensorimotor, feeding and drinking behaviors, sodium appetite, and gustatory capacities were made between ages 1 and 150 days. PBN rats displayed a transient period of attenuated suckling, as evidenced by body weight loss. When tested soon after weaning, PBN rats were hyperdipsic in response to cellular dehydration and during food deprivation. This effect, however, was temporary. When tested as adults, PBN rats were hypodipsic in response to extracellular fluid volume depletion, they displayed alterations in sodium appetite, showed "exaggerated" preferences and aversions to saccharin and NaCl solutions, and they displayed attenuated quinine aversions. These results are generally similar to the behaviors of rats sustaining more central gustatory pathway lesions as adults. The functional significance of the PBN in the developing rat for preference/aversion and sodium appetite behaviors are discussed.
TL;DR: Results demonstrate that tests of advantageous learning such as observational learning are sensitive to the kinds of early biological insult that lead to permanent cognitive impairment in humans and animals and support the concept that the cognitive impairment observed during periods of malnutrition in human and animals is not permanent.
Abstract: The effects of two biological insults, hypothyroidism and malnutrition, incurred during pre- and postnatal development were compared using a newly developed test of observational learning in rats. Whereas early hypothyroidism produced a significant impairment in observational learning in recovered rats, no indication of any impairment was observed in rats recovered from early malnutrition. These results are important in that they demonstrate that tests of advantageous learning such as observational learning are sensitive to the kinds of early biological insult that lead to permanent cognitive impairment in humans. Moreover, these data further support the concept that the cognitive impairment observed during periods of malnutrition in humans and animals is not permanent.
TL;DR: Evidence of Nutrition X Stock interactions, together with that from analyses of the effects of nutrition performed separately for the 2 stocks, as if each stock had been investigated in a separate study, indicates that genotypic differences may be one of the reasons for the discordance often found between the conclusions of different early life malnutrition studies.
Abstract: Developing rats of 2 outbred stocks were either well-nourished or undernourished by underfeeding their mothers throughout pregnancy and lactation. All rats were well-fed from 25 days of age. Starting at 110 days male rats were observed first in an open field and then in a social situation; finally their motor performance was tested on a revolving drum. The social behavior test comprised pairing male rats of the same stock, 1 well-fed control with 1 previously undernourished rat.
Analysis of variance of the results of the open-field and social behavior tests revealed main effects of Nutrition and of Stock for several measures of behavior in each test. There were also Nutrition X Stock interactions for 2 measures from the open field and 1 from the social situation. Motor performance was not impaired by early life undernutrition. The evidence of Nutrition X Stock interactions, together with that from analyses of the effects of nutrition performed separately for the 2 stocks, as if each stock had been investigated in a separate study, indicates that genotypic differences may be one of the reasons for the discordance often found between the conclusions of different early life malnutrition studies.
TL;DR: The inability of suckling and weanling pups to thrive in the chronic phase of vagotomy indicates that nonvagal internal controls of ingestion and digestion function adequately for survival, but they are not optimal for growth and maintenance of body weight in rats.
Abstract: The importance of gut signals for the short-term and long-term control of ingestion was investigated using rat pups in the natural suckling situation. Pups at 10 days of age were deprived of milk and their dam for 9 hr. Pyloric ligation, vagotomy, and preloading procedures were performed on the pups shortly before testing began. The initial latency to attach to a nipple and the incidence of attachment were recorded during the 2-hr suckling period. Milk intake and the weight of gastric contents were measured following the test. Pregastric stimulation together with natural or artificial gastric filling suppressed ingestion. Acute subdiaphragmatic truncal vagotomy enhanced ingestion under these conditions, and vagotomy alone resulted in controlled hyperphagia concomitant with exaggerated gastric filling. The data suggest that the stomach is one site where milk activates a suppression mechanism for ingestion. This mechanism is mediated primarily by the vagus nerve. The importance of nipple-attachment behavior is discussed in relation to ingestive behavior, and the question of satiety in suckling rats is raised. The chronic effects of truncal vagotomy on rat pups were also investigated, beginning with denervation at 10 days of age. The pups were challenged with deprivation and tested in the natural suckling situation on Day 20. Weaning occurred on Day 22, and the pups were sacrificed on Day 41, followed by measurements of body weight, body length, and gastric contents. The physical and behavioral changes that developed during the chronic phase of vagotomy included (1) permanent gastric distension following the first postsurgical bout of ingestion; (2) reduced intake of milk when the availability of milk was greatest during the suckling test; (3) increased resting behavior regardless of milk letdown conditions during the suckling test; (4) failure to gain weight at a normal rate; and (5) failure to grow at a normal rate. The data indicate that the vagus nerve is necessary for normal internal control of ingestion as well as normal gastric filling and emptying in the suckling rat. The inability of suckling and weanling pups to thrive in the chronic phase of vagotomy indicates that nonvagal internal controls of ingestion and digestion function adequately for survival, but they are not optimal for growth and maintenance of body weight in rats.
TL;DR: Two chimpanzees (Pan tryglodytes) were presented with liquid and number conservation problems and one chimpanzee, Jane, was successful in solving both sets of problems in that she was not distracted by irrelevant transformations, being influenced only by changes in quantity.
Abstract: Two chimpanzees (Pan tryglodytes), Fanny and Jane, were presented with liquid and number conservation problems. One chimpanzee, Jane, was successful in solving both sets of problems in that she was not distracted by irrelevant transformations, being influenced only by changes in quantity. Her success appeared to be based on the ability to make inferences rather than on simple perceptual judgement of the final comparison. The results are compared and contrasted with those of Premack, in G. Woodruff, D. Premack, and K. Kennel [(1978). Conservation of liquid and solid quantity by the chimpanzee. Science, 202:99-994] and J. Mehler and T. G. Bever [(1967). Cognitive capacity of very young children. Science, 158:141-142; (1968). Quantification, conservation and nativism. Science, 162:979-981], and it is suggested that there may be a similarity of conservation development between chimpanzees and man.
TL;DR: This finding extends previous work on memory recovery in young animals by demonstrating alleviation of infantile amnesia without a re-exposure to the CS or UCS during the retention interval.
Abstract: Although a number of studies have demonstrated that the relatively rapid rate of forgetting in young rats (i.e., infantile amnesia) can be alleviated by various reminder treatments, the possibility of enhancing retention by other procedures seems largely unexplored. Given the putative importance of contextual cues as sources of memory retrieval, this experiment examined whether the presence of a distinctive pharmacological state at training and testing could override infantile amnesia. Weanling rats were given pentobarbital or saline prior to Pavlovian fear-conditioning. When tested 1 week later, subjects in the same-state drug condition showed better retention than the same-state saline group. This finding extends previous work on memory recovery in young animals by demonstrating alleviation of infantile amnesia without a re-exposure to the CS or UCS during the retention interval.
TL;DR: The inhibitory response exhibited by ducklings upon hearing the alarm call reflects auditory perceptual specificity to a range of moderately slow repetition rates that are characteristic of normally occurring sounds of the perinatal environment.
Abstract: Mallard ducklings (Anas platyrhynchos) inhibit their vocal and locomotor behavior upon hearing the maternal alarm call. An important acoustic feature of the call that affects such inhibition is the slow repetition rate of the notes. This study assesses the range of repetition rates that affect behavioral inhibition in 1-day-old domestic mallard (Peking) ducklings. Four hundred and fifty maternally naive ducklings were tested in groups of 30 to repetition rates ranging from .2 to 3.0 notes/sec in 2/10-sec increments. Various behavioral measures (i.e., incidence of inhibition, latency and duration of inhibition) revealed that the optimal range of repetition rates affecting inhibition extends from .8 to 1.8 notes/sec. Within this range, 1.0 and 1.6 notes/sec are particularly effective. The efficacy of these particular 2 rates may reflect their correspondence with the rates of the modal alarm call and certain kinds of self-produced embryonic vocalizations, respectively. Unexpectedly, very slow repetition rates (.2 and .4 notes/sec) are not as effective as faster rates in promoting inhibition. Thus, the inhibitory response exhibited by ducklings upon hearing the alarm call reflects auditory perceptual specificity to a range of moderately slow repetition rates that are characteristic of normally occurring sounds of the perinatal environment.
TL;DR: The influence of LiCl preexposure on odor-aversion conditioning produced by an odor-LiCl pairing was studied in rats 7-31 days old, and it was suggested that the age-dependent differences in the time course of the Li Cl preexposed effect may be determined in part by age-related Differences in the rat's excretory processes that clear lithium from the circulatory system.
Abstract: The influence of LiCl preexposure on odor-aversion conditioning produced by an odor-LiCl pairing was studied in rats 7-31 days old. LiCl preexposure interfered with the acquisition of the odor aversion in both young and old pups. The time course of this effect depended, however, on the age of the pups. It lasted much longer (over 24 hr) if pups 8-17 days old were preexposed to LiCl than if the pups were preexposed when 30 days old (less 12 hr). Alternative interpretations of these data were discussed, and it was suggested that the age-dependent differences in the time course of the LiCl preexposed effect may be determined in part by age-related differences in the rat's excretory processes that clear lithium from the circulatory system.
TL;DR: Age was the major determinant of choice, with more older animals choosing the food arm, and availability of maternal contact in the feeding compartment increased the percentage of rats that chose to feed by about 20% at all ages studied.
Abstract: To help identify determinants of rat appetitive behavior during the weanling period, rat pups 17-32 days of age were studied in a Y-maze. One arm of the maze provided pups with the opportunity to suckle a lactating or nonlactating anesthetized female. The other arm always contained a familiar food, either liquid diet or ground laboratory chow. In some experiments the dam was separated from the food compartment by a thin gauze screen. In other tests maternal contact could be maintained in the feeding goal but suckling in that compartment was prevented by nipple involution. Age was the major determinant of choice, with more older animals choosing the food arm. Availability of maternal contact in the feeding compartment increased the percentage of rats that chose to feed by about 20% at all ages studied. Food quality, but not quantity, affected choice at each age, as did lactational status. Prior food, water, and maternal deprivation (2 or 24 hr) did not affect choice behavior at any age but did influence behavior in the goal box. These findings are discussed within the context of the changing demands faced by the rats during the weaning period.
TL;DR: To determine the role of exposure of wood ducklings to conspecific vocalizations in the development of selective responsiveness to the descending FM of the species maternal call, the behavioral response of embryos to synthetic descending and ascending maternal calls was examined.
Abstract: A critical acoustic feature of the wood duck maternal assembly call is the descending frequency modulation (FM) of its notes. To determine the role of exposure of wood ducklings to conspecific vocalizations in the development of selective responsiveness to the descending FM of the species maternal call, the behavioral response of embryos to synthetic descending and ascending maternal calls was examined. Previous work indicated that selective responsiveness of newly hatched wood ducklings to the descending FM of the maternal call is dependent upon prior exposure to descending FM calls of siblings. In advance of auditory experience the youngest embryos were responsive to both ascending and descending call notes, but older aurally isolated embryos became selectively responsive to the descending FM. However, even though the wood duck hatching vocalizes considerably in aural isolation, self-stimulation is ineffective in maintaining the perceptual selectivity in the neonate. Unlike the mallard, in which self-stimulation is adequate, the wood duckling must be exposed to sib vocalizations in order to remain selectively responsive to the critical acoustic feature of the maternal call of its species.
TL;DR: The results show the main features of mouse brain growth to parallel those of human brain growth except for timing of rapid and slow growth.
Abstract: Brain growth was studied from day of birth through 23 days of age in three outbred and one inbred groups of mice. The results showed that the brain grows rapidly from Birth through 11 days and quite slowly thereafter. We found no evidence of the several spurts and plateaus in growth that are central to the theory of phrenoblysis (correlated brain and mind growth). Our results show the main features of mouse brain growth to parallel those of human brain growth except for timing of rapid and slow growth.
TL;DR: While the statistically significant spurts observed in each variable did fall within the hypothesized age periods, the chance rate for such theoretical concordance was high and several hypothesized spurts were not supported, and no relationship existed within individuals between head-circumference and mental-age growth-rate patterns.
Abstract: Epstein's phrenoblysis hypothesis states that brain growth and mental growth occur in correlated spurts at 3-10 months and 2-4, 6-8, 10-12 or 13, and 14-16 or 17 years of age. The present study was the first to test statistically such spurts in head-circumference and mental-age growth rates and to assess any correspondence in individual differences between spurts in the two variables in a single sample of children measured serially between 2.5 and 17 years of age. While the statistically significant spurts observed in each variable did fall within the hypothesized age periods, the chance rate for such theoretical concordance was high and several hypothesized spurts were not supported. Moreover, no relationship existed within individuals between head-circumference and mental-age growth-rate patterns.
TL;DR: It is hypotheses that the development of foraging strategies might be necessary for the expression of maze behaviors reinforced with milk alone and 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.
Abstract: 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.