The etiology of schizophrenia's cognitive symptoms may have its basis in prenatal alterations of glutamate N-methyl-D-aspartate (NMDA) receptor functioning. Therefore, the current study investigated the effects of ketamine (an NMDA receptor blocking drug) on both a conditioned taste aversion (CTA) and latent inhibition (LI; a model of attentional capacity) in rat fetuses. We first sought to determine if a CTA could be diminished by nonreinforced preexposure to a CS in fetal rats (i.e., LI). We injected E18 pregnant Sprague–Dawley rats with 100% allicin (garlic taste) or an equal volume of saline. Some of the pregnant dams also received ketamine (100 mg/kg, i.p.). One day later (E19), the dams received a second injection of the CS, followed by either lithium chloride (the US) or saline. Finally, on E21 pups received oral lavage with allicin and observations of ingestive orofacial motor responses were recorded. When allicin had been paired with LiCl in utero, E21 fetuses exhibited a conditioned suppression of orofacial movements, indicative of an aversion to this taste. Preexposure to the garlic taste on E18 produced a LI of this CTA. Ketamine significantly disrupted the formation of the CTA and had some impact on LI. However, the direct effect of ketamine on LI is less certain since the drug also blocked the original CTA. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

Whether animals represent environmental geometry in a global and/or local way has been the subject of recent debate. We applied a transfer of search paradigm between rectangular- and kite-shaped arenas to examine the performance of human adults (using virtual environments) and children of 2.5–3.5 years (using real arenas). Adults showed robust transfer to a congruent corner in a kite-shaped arena, following training in a rectangular-shaped arena in two paradigms modeled on those used with rats and young children respectively. In contrast, the children showed no evidence of transfer of search, despite above chance performance in the rectangular arena, and above chance performance in a study where search occurred in the kite arena only. The pattern of findings suggests global aspects of environmental geometry may be used to re-establish heading, and that the matching of elements of local geometry in new global contexts may be an advanced developmental achievement. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

End-state comfort (ESC) is the tendency to assume comfortable postures at the end of simple object manipulation rather than at the start; and therefore has been used to assess the behavioral effects of motor planning. Adult-like patterns have been observed at age 9. Observations can extend to joint-action, such that adults consider the beginning-state comfort (BSC) of another, without sacrificing ESC; however, trends in children have yet to be delineated. This study investigated the development of ESC and BSC in a cup manipulation task. Three to 12-year-olds and adults were asked to pick up a cup and (1) pour a glass of water or (2) pass it to the researcher to pour. Paralleling previous findings, adult-like patterns of ESC were observed at age 9. Adding to the literature, adult-like evidence of BSC emerged at the age of 7. Therefore, 7-year-olds consider another's BSC; however, cannot facilitate ESC until age 9. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

Intervention studies indicate that children's early child-care experiences can be leveraged to foster their development of effective self-regulation skills. It is less clear whether typical child-care experiences play a similar role. In addition, evidence suggests that children with a common variant of the DRD4 gene (48-bp VNTR, 7-repeat) may be more sensitive to their experiences than those without this variant. Using data from the NICHD Study of Early Child Care and Youth Development, we considered the degree to which children's early child-care experiences—quantity, quality, and type—were associated with their attention and self-regulation abilities in prekindergarten, and, in particular, whether these relations were conditional on DRD4 genotype. G × E interactions were evident across multiple neuropsychological and observational measures of children's attention and self-regulation abilities. Across most outcome measures, DRD4 7+ children spending fewer hours in child care showed more effective attention/self-regulation abilities. For those without a copy of the DRD4 7-repeat allele, such associations were typically null. The results for child-care quality and type indicated no interactions with genotype; the main-effect associations were somewhat inconsistent. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

Maternal care variations associate with DNA methylation of the glucocorticoid receptor gene, Nr3c1, in hippocampus at a nerve-growth factor-inducible protein 1 binding site. Epigenetic regulation of brain-derived neurotrophin factor is affected by early stress. These systems contribute to anxiety and fear. Early stress has sex-dependent effects perhaps reflecting sex differences in maternal care. Altering litter gender composition affects maternal behavior and DNA methylation levels of another gene in hippocampus and nucleus accumbens (NAc). We now test if DNA methylation levels of Nr3c1, Egr1, and Bdnf differ by litter composition or sex. Rats from mixed- or single-sex litters were tested for anxiety and fear on postnatal day 35. Brain tissues were collected and analyzed using direct sequencing methods. Females showed hypermethylation of Nr3c1 of hippocampal DNA and litter composition modified sex effects on methylation of Egr1 in NAc. Few differences were seen for Bdnf. LGC modified some sex differences in behavior. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

Two experiments assessing event-related potentials in 5-month-old infants were conducted to examine neural correlates of attentional salience and efficiency of processing of a visual event (woman speaking) paired with redundant (synchronous) speech, nonredundant (asynchronous) speech, or no speech. In Experiment 1, the Nc component associated with attentional salience was greater in amplitude following synchronous audiovisual as compared with asynchronous audiovisual and unimodal visual presentations. A block design was utilized in Experiment 2 to examine efficiency of processing of a visual event. Only infants exposed to synchronous audiovisual speech demonstrated a significant reduction in amplitude of the late slow wave associated with successful stimulus processing and recognition memory from early to late blocks of trials. These findings indicate that events that provide intersensory redundancy are associated with enhanced neural responsiveness indicative of greater attentional salience and more efficient stimulus processing as compared with the same events when they provide no intersensory redundancy in 5-month-old infants. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

This study addressed early calibration of stress systems by testing links between adversity exposures, developmental stability of hypothalamic–pituitary–adrenal (HPA) axis activity, and behavior problems in a sample of adopted children. Families (n = 200) were assessed when the child was 9, 18, and 27 months, 4.5 and 6 years to collect adversity information—parent psychopathology, stress, financial need, and home chaos. Morning and evening cortisol samples at the final two assessments indexed child HPA activity, and parent-reported internalizing and externalizing at the final assessment represented child behavior outcomes. Increases in cumulative adversity from 4.5 to 6 related to higher child morning cortisol, whereas age six cumulative adversities related to lower, unstable child evening cortisol. Examination of specific adversity dimensions revealed associations between (1) increasing home chaos and stable morning cortisol, which in turn related to internalizing problems; and (2) high parental stress and psychopathology and lower, unstable evening cortisol, which in turn related to externalizing problems. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

Early locomotion in the neonatal rat previously has been reported 3 days after birth during exposure to an odor of biological relevance (nest material). The current study explores if other ecologically relevant stimuli—amniotic fluid (AF) and milk—could evoke a similar locomotor response in the newborn rat and whether the endogenous opioid system mediates the response. Newborn rats tested 24 hr after birth were presented with the odors of AF or milk while placed in a runway. Pups expressed crawling and moved along the runway in response to direct exposure to the odors of AF and milk (Exp. 1). However, there was no evidence that this crawling response was altered after pretreatment with the opioid antagonist naloxone (Exp. 2). This study provides evidence of the capacity of AF and milk to evoke coordinated motor behavior, suggesting that they may play a role in the development of fundamental motor patterns. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

The present longitudinal study examined relations between respiratory sinus arrhythmia (RSA) development and social responsiveness characteristics associated with autism spectrum disorders. Group-based developmental trajectory modeling was used to characterize RSA development patterns in 106 typically developing children across 5, 10, 24, 36, and 48 months of age. A two-group model fit of RSA development was found: a “typically” and “atypically” developing group. The typical group gradually increased in RSA across 5–48 months of age. The atypical group, however, increased in RSA from 5 to 24 months and demonstrated a plateau or “delay” in RSA development from 24 to 48 months. The atypical RSA development group also demonstrated more difficulties in parent-reported social responsiveness at 48 months. The results support current literature that identifies RSA as a marker of social functioning level. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

A question still to be answered is whether ethanol initiation has a greater effect on ethanol consumption if it occurs during adolescence than in adulthood. This study assessed the effect of ethanol initiation during adolescence or adulthood on voluntary ethanol consumption when animals were still within the same age range. Adolescent or adult rats were given 5, 2, or 0 ethanol exposures. The animals were tested for ethanol consumption through two-bottle choice tests, before undergoing a 1-week deprivation. A two-bottle assessment was conducted after the deprivation. Adolescents, but not adults, given two ethanol administrations during initiation exhibited significantly higher ethanol intake during the pre-deprivation period. These adolescents also exhibited a threefold increase in ethanol intake after 7 days of drug withdrawal, when compared with controls. These findings suggest that very brief experience with binge ethanol intoxication in adolescence, but not in adulthood, impacts later predisposition to drink. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

Behavioral inhibition (BI) is a temperament characterized during early childhood by increased fearfulness to novelty, social reticence to unfamiliar peers, and heightened risk for the development of anxiety. Heightened startle responses to safety cues have been found among behaviorally inhibited adolescents who have an anxiety disorder suggesting that this measure may serve as a biomarker for the development of anxiety amongst this risk population. However, it is unknown if these aberrant startle patterns emerge prior to the manifestation of anxiety in this temperament group. The current study examined potentiated startle in 7-year-old children characterized with BI early in life. High behaviorally inhibited children displayed increased startle magnitude to safety cues, particularly during the first half of the task, and faster startle responses compared to low behaviorally inhibited children. These findings suggest that aberrant startle responses are apparent in behaviorally inhibited children during early childhood prior to the onset of a disorder and may serve as a possible endophenotype for the development of anxiety. © 2013 Wiley Periodicals, Inc. Dev Psychobiol

To examine young infants' sensitivity to a pictorial depth cue, we compared monocular and binocular preferential looking to objects of which depth was specified by height-in-the-picture-plane. For adults, this cue generates the perception that a lower object is closer than a higher object. This study showed that 4- and 5-month-old infants fixated the lower, apparently closer, figure more often under the monocular than binocular presentation providing evidence of their sensitivity to the pictorial depth cue. Because the displays were identical in the two conditions except for binocular information for depth, the difference in looking-behavior indicated sensitivity to depth information, excluding a possibility that they responded to 2D characteristics. This study also confirmed the usefulness of the method, preferential looking with a monocular and binocular comparison, to examine sensitivity to a pictorial depth cue in young infants, who are too immature to reach reliably for the closer of two objects. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The aim of this study was to evaluate the effectiveness of three local, topical anesthetics on touch response thresholds of the paws of 1-day-old rats. Touch response thresholds were measured using Semmes Weinstein monofilaments after treatment of the paws with EMLA (2.5% lidocaine and 2.5% prilocaine), alcaine (.5% proparacaine), triocaine (20% benzocaine, 6% lidocaine, and 4% tetracaine), or petroleum jelly (treatment control). Touch thresholds significantly increased after treatment with EMLA 18% of the time, and there was no evidence of a systemic effect. Touch thresholds were not significantly altered after treatment with alcaine, triocaine, or petroleum jelly. Therefore, EMLA appears to be a slightly effective topical anesthetic for reducing tactile sensitivity in newborn rats. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

We investigated the development of the HPA axis in group-living rhesus monkeys. Forty-three infants were studied from birth through their third year of life; 22 infants were physically abused by their mothers, while 21 infants were not abused. Plasma cortisol levels in basal conditions and in response to a novel environment test were assessed at 6-month intervals. Both basal and stress cortisol increased steadily from 6 to 24 months of age and then dropped. Across all ages, stress cortisol levels were significantly higher than the basal levels. The cortisol responses to stress at 30 and 36 months of age were significantly lower than the responses at all other ages. At most ages there was an inverse relationship between basal and stress cortisol levels. Individual differences in basal cortisol levels were generally stable in the first 2 years and more variable in the third year while the opposite for true for cortisol responses to stress. At the end of the first year, but not later in life, abused infants had higher cortisol levels than controls across the basal and stress conditions. Rates of social interactions with the mother and other group members were positively correlated with basal cortisol levels early in life, and with cortisol responses to stress later in life. Altogether, these results indicate that there are strong individual differences in HPA function, that there is a relationship between basal activity and stress reactivity, and that early abuse has the short-term effect of increasing both basal activity and stress reactivity. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Patients treated for bilateral congenital cataract are later impaired on several hallmarks of adults' expertise with upright faces but report no problem with remembering faces. Here, we provide the first formal data on their face memory. We compared 12 adults with a history of visual deprivation from bilateral congenital cataracts to 24 age-matched controls with normal vision on their ability to recognize famous and recently learned faces, and on their subjective impression of their face memory. Bilateral congenital cataract patients demonstrated a prosopagnosic-like deficit, being slower and less accurate in recognizing both famous faces and recently learned faces, despite not differing on most questions about their impression of their face memory. Patients' results on three perceptual tasks (the composite face effect, the Benton test of recognizing faces through a change in point of view, and the Jane test of sensitivity to feature spacing) were also not correlated with their face memory deficits. These results suggest that early visual input is necessary not only for perceptual expertise in differentiating among unfamiliar upright faces, but also for normal accuracy in remembering the identity of individual faces. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Longitudinal studies tracking the early development of manual asymmetries are fairly rare compared to the large number of studies assessing hand preference in infancy. Moreover, most prior longitudinal studies have performed behavioral observation over relatively short-time spans considering the celerity of early development. This study aims (i) to investigate the direction and consistency of manual lateral asymmetries over a longer period, from birth to 24 months of age, and (ii) to compare individual and group trajectories to better understand discrepancies between prior studies. Nineteen healthy infants were observed eight times in tasks that were adjusted progressively as infants manual skills developed. Results suggested two distinct periods in terms of the direction, strength, and consistency of manual preference. First, infants went through an initial phase characterized by a lack of lateral manual asymmetries. From 9 months of age, however, group analyses revealed an emerging and steadily growing right lateral bias over time, while individual trajectories revealed that the group-level right-bias formed progressively from a background of highly fluctuating and highly variable developmental trajectories. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Resting EEG asymmetry evident early in life is thought to bias affective behaviors and contribute to the development of psychopathology. However, it remains unclear at what stage of information processing this bias occurs. Asymmetry may serve as an afferent filter, modulating emotional reactivity to incoming stimuli; or as an efferent filter, modulating behavioral response tendencies under emotional conditions. This study examines 209 kindergarten children (M = 6.03 years old) to test predictions put forth by the two models. Resting asymmetry was examined in conjunction with electrodermal and cardiac measures of physiological reactivity to four emotion-inducing film clips (fear, sad, happy, anger) and teacher ratings of psychopathology. Results confirm an association between increased right side cortical activation and internalizing symptom severity as well as left activation and externalizing symptom severity. Significant interactions between resting asymmetry and physiological reactivity to emotion indicate that physiological reactivity moderates the association between resting asymmetry and symptoms of psychopathology. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

As previously shown, rats isolated from weaning develop abnormal social and aggressive behavior characterized by biting attacks targeting vulnerable body parts of opponents, reduced attack signaling, and increased defensive behavior despite increased attack counts. Here we studied whether this form of violent aggression could be reversed by resocialization in adulthood. During the first weak of resocialization, isolation-reared rats showed multiple social deficits including increased defensiveness and decreased huddling during sleep. Deficits were markedly attenuated in the second and third weeks. Despite improved social functioning in groups, isolated rats readily showed abnormal features of aggression in a resident-intruder test performed after the 3-week-long resocialization. Thus, post-weaning social isolation-induced deficits in prosocial behavior were eliminated by resocialization during adulthood, but abnormal aggression was resilient to this treatment. Findings are compared to those obtained in humans who suffered early social maltreatment, and who also show social deficits and dysfunctional aggression in adulthood. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Evidence suggests that prenatal maternal stress (PNMS) has long-term effects on several outcomes, yet effects on neuromotor function are relatively unknown. We aimed to determine whether disaster-related PNMS predicts motor functioning in young children and whether timing of exposure and sex of the child moderate these effects. Objective and subjective PNMS levels were assessed among pregnant women exposed to a natural disaster. Their children's bilateral coordination, balance, and visual motor integration (VMI) were assessed at 5½ years. Girls performed better than boys. Objective stress exposure and subjective distress interacted such that when subjective distress was high, no added effect of objective hardship was observed; when subjective distress was low, objective hardship showed a negative effect. In girls, late pregnancy exposure was associated with poorer outcomes. In conclusion, disaster-related PNMS is associated with relatively lower motor functions in exposed offspring. Exposure timing, sex, and type of stress influenced the effects. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Behavioral sensitization has been suggested to contribute to uncontrolled alcohol consumption. The aim of this study was to investigate the effects of repeated ethanol administration in adolescent and adult mice on subsequent ethanol consumption and conditioned place preference (CPP). Mice were administered ethanol for 15 consecutive days. This ethanol regimen induced behavioral sensitization to a lesser degree in adolescents than in adults. Following ethanol treatment, mice were subjected to CPP procedure, or given a free choice between water and ethanol solutions. While ethanol-pretreated adult mice did not display a robust ethanol-induced CPP, ethanol induced a significant CPP in mice pretreated with ethanol during adolescence. Ethanol pretreated mice, regardless of age, showed higher ethanol intake to saline-treated mice. The present findings suggest that ethanol-induced neuroadaptations underlying behavioral sensitization may activate mechanisms responsible for enhanced ethanol intake, and also reveals that ethanol pre-exposure during adolescence increases ethanol reward as measured by CPP. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The present study evaluated the possibility of collecting cardiac vagal tone data using a photoplethysmograph, and its stability and continuity in a longitudinal sample of early-school aged children. A method for the optical (i.e., blood volume pulse) estimation of heart rate was established in a pilot study. Then the longitudinal stability and continuity in photoplethysmograph-derived vagal tone was assessed in 114 children (56 girls) at three sessions between 5 and 7 years of age. Results indicate that this method possesses substantial measurement reliability and individual stability, as children report low intra-individual variation over time. Children also report a mean decrease in vagal tone from 5 to 7 years of age, consistent with increased attentional capacity. Overall, this suggests blood volume pulse estimation of vagal tone is both accurate and appropriate for naturalistic developmental research. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The variation in hand use as a function of task and developmental age poses a problem for understanding how and when “handedness,” preferred use of one hand, develops. The present cross-section study is the first to contrast hand preference use for the natural and frequently used reach-to-eat movement with a constructional task that requires a very similar reach-to-grasp movement. Thirty children between the ages of 1 and 3 years completed an eating task, in which they grasped small food items (Cheerios™ or Froot Loops™) that they brought to the mouth for eating. Thirty children between the ages of 3 and 5 years completed the construction task, in which they grasped LEGO® pieces to construct 3D models. Hand use preference for grasping in the eating and construction tasks was calculated by comparing the percentage of grasps made by the right hand and by the left hand. There were two main findings: First, right hand preference for grasping in the eating task is present as early as 1 year of age, whereas right hand preference for grasping in the construction task does not develop until 4 years of age. Second, right hand preference for grasping is greater in the eating than in the construction task. The results are discussed in relation to the idea that a consideration for task constraints (e.g., unimanual vs. bimanual; eating vs. construction; natural vs. praxic) should be incorporated into the experimental design when measuring hand use in children. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Recent findings show that developmental vitamin D deficiency leads to altered brain morphology and behavioral development in the rat offspring. We examined the effects of different dietary vitamin D levels in rat dams on behavior and biochemistry of the offspring. Females were divided into five conditions and received diets containing 0, 1,5, 3.3, 6.0, or 10.0 IU/g of vitamin D₃ from mating to weaning. Offspring were tested as juveniles and as adults for anxiety, social learning and behavior, and locomotion. Results show that both deficient and excessive levels of vitamin D₃ in juveniles lead to altered physiology and behavior. In juveniles but not adults, variations in vitamin D were related to variations in measures of anxiety and marginally, activity levels. For social behaviors, both juveniles and adults were affected by mothers' diets. In general, offspring of animals receiving abnormal concentrations of vitamin D showed the most deficits. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

It is a mammalian female strategy to emit odor cues and signals that direct their inexperienced newborns to the nipple, and optimize their initial sucking success and, hence, viability. Here, natural odorous substrates that contribute to nipple grasping were investigated in mice, a species that has not been much scrutinized on this topic. The response of pups toward the nipples of lactating females (LF) versus nonlactating females (NLF) were first assessed right after watched birth, before and after the first suckling experience, and at 1 day old, after more extended suckling experience. It appeared that only nipples of LF induced grasping at these early ages, leading to take NLF as the baseline setting to present various odor substrates sampled from LF, viz. amniotic fluid, murine milk, LF saliva, pup saliva, LF urine, and an odorless control stimulus (water). Results indicate that: (1) only amniotic fluid and fresh milk induced nipple grasping before the first suckling experience; (2) LF saliva started inducing grasping after the first suckling experience; (3) pup saliva released grasping after 24–36 hr of suckling experience; finally (4) neither LF urine, nor water induced any nipple grasping. In conclusion, the activity of amniotic fluid and murine milk on neonatal pup behavior before any postnatal suckling experience suggests that either prenatal learning and/or predisposed olfactory mechanisms do operate, while the behavioral activation due to maternal and infantile salivas clearly depends on postnatal exposure. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

We investigated the effects of social instability stress (daily 1-hr isolation, change of cage partner, postnatal day 30–45) in adolescence in male rats on open field exploration and social behavior in adulthood. Social stressed rats had longer latencies to enter the center of an open field and then took longer to approach an object placed in the center of the field. When another rat was placed in the open field, stressed rats spent less time in social interaction than control rats, particularly when paired with another stressed, rather than a control, rat. The groups did not differ in social approach tests (when a stimulus rat was separated by wire mesh) nor in novel object exploration (when controlling for open field anxiety). The results suggest social stress in adolescence increases open field anxiety while maintaining exploratory behavior, and alters social interactions in adulthood. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Opioids show both pro- and anti-epileptogenic effects in different experimental models of epilepsy. In the present study, the pentylentetrazole (PTZ)-induced seizure model was used to test the hypothesis that neonatal morphine administration affects seizure susceptibility in prepubertal rats. Female rats were subcutaneously injected with either morphine or saline on postnatal days 8–14 (P8–P14). To verify the long-term effect of morphine (or saline), the animals were treated second time with morphine (21 mg/kg; or saline) on either P25 or P32. Morphine administration decreased latency of myoclonic jerks and time to onset and increased tonic–clonic seizure rate at P25, but these findings were inversed at P32. Results showed a significant age difference in seizure behaviors between P25 and P32 animals. Blood corticosterone (COS) levels were significantly higher in P32 rats than in P25 rats. These findings show that neonatal morphine exposure plays an important role in increasing seizure vulnerability in P25 prepubertal rats but not in P32 rats. We conclude that early exposure to chronic morphine in infant rats might change their susceptibility to PTZ-induced seizure in an age-dependent manner. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Current knowledge of the perceptual and cognitive abilities in infancy is largely based on the visual habituation–dishabituation method. According to the comparator model [e.g., Sokolov (1963a) Perception and the conditioned reflex. Oxford: Pergamon Press], habituation refers to stimulus encoding and dishabituation refers to discriminatory memory performance. The review also describes the dual-process theory and the attention disengagement approach. The dual-process theory points to the impact of natural stimulus preferences on habituation–dishabituation processes. The attention disengagement approach emphasizes the contribution of the ability to shift the attention away from a stimulus. Moreover, arguments for the cognitive interpretation of visual habituation and dishabituations are discussed. These arguments are provided by physiological studies and by research on interindividual differences. Overall, the review shows that current research supports the comparator model. It emphasizes that the investigation of habituation and dishabituation expands our understanding of visual attention processes in infants. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

In this study, we investigated whether hand preference influences infants' choice of what hand to use in grasping a new tool presented at the midline, and whether this will change in the course of learning the functionality of a tool. The tool was a rake within reach placed beside an out-of-reach toy presented either to its right or to its left. Forty-eight infants from 16 to 22 months of age were tested. The results show that use of the right-preferred hand to grasp the rake is strong as of 16 months of age and does not change significantly with age in the condition where using the right hand leads to a better outcome than using the left hand. In the condition where using the left-non-preferred hand makes toy retrieval easier, infants increasingly use the left hand with age. Thus, when grasping the tool, younger infants are more influenced by their hand preference than older infants, who are better at anticipating the most successful strategies. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Early sociodemographic risk, parenting, and temperament were examined as predictors of the activity of children's (N = 148; 81 boys, 67 girls) hypothalamic–pituitary–adrenal axis and autonomic nervous system. Demographic risk was assessed at 18 months (T1), intrusive/overcontrolling parenting and effortful control were assessed at 30 months (T2), and salivary cortisol and alpha-amylase were collected at 72 (T3) months of age. Demographic risk at T1 predicted lower levels of children's effortful control and higher levels of mothers' intrusive/overcontrolling parenting at T2. Intrusive/overcontrolling parenting at T2 predicted higher levels of children's cortisol and alpha-amylase at T3, but effortful control did not uniquely predict children's cortisol or alpha-amylase levels. Findings support the open nature of stress responsive physiological systems to influence by features of the early caregiving environment and underscore the utility of including measures of these systems in prevention trials designed to influence child outcomes by modifying parenting behavior. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The aim of this study was to investigate the relationship between hand preference for communicative gestures and language during development. Hand preference for pointing gestures and level of language were assessed in 46 toddlers between 12 and 30 months of age. Results showed a right-hand preference for pointing and the use of a developmental quotient (DQ) for language revealed a significant correlation between the degree of hand preference and DQ for language in children with a quotient above 100. Thus, these children were more right-handed for pointing gestures as DQ increased. These results highlight the close association between the development of hand preference for pointing and the speed of language development, suggesting a new direction for studies of language–gesture links in toddlers. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Maternal care influences the development of sexual behavior in pair mating rats, under laboratory conditions. This study examined the effect of variations in maternal care in a group-mating condition. Groups of two low and two high licking/grooming (LG) female offspring mated with two males in a large pacing chamber for 36 hr. Sexual behaviors were scored for the first 15 vaginal–cervical stimulations (VCS) and the entire 36 hr. Low LG females spent more time mating, required more time to receive an intromission after entering the male compartment. They also received more ejaculations compared to high LG females during the first 15 VCS. This difference disappeared as mating continued. Males were more responsive to high than low females. No pregnancy rate difference was seen between the two female phenotypes, demonstrating that variation in maternal care received results in two mating strategies that are both reproductively successful under group-mating conditions. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The current study explored whether birth timing, known to influence the mother–infant relationship, also affected infant physiology up to 9 months later and infant behavior at weaning. Infant blood samples were collected at 5.75 and 8.75 months of age to assess functioning of the hypothalamic–pituitary–adrenal axis as well as the antibody response to a Cholera vaccination. Path analysis indicated infants born late in the birth season had less Relaxed relationships with their mothers. A less-Relaxed relationship was associated with greater infant Positive Engagement and Distress, which were negatively correlated, suggesting infants may have different strategies of coping with this type of relationship. Low Relaxed scores were also associated with higher infant cortisol concentrations at 5.75 months, which was associated with a reduced immune response to a vaccination 3 months later. Together these results indicate that the influence of birth timing on the mother–infant relationship may have consequences for infant development. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The study assessed possible age differences in brain activation patterns to low dose ethanol (.5 g/kg intraperitoneally) and the influence of social context on this activation. Early adolescent or young adult male Sprague–Dawley rats were placed either alone or with an unfamiliar partner of the same age and sex following saline or ethanol administration. c-Fos protein immunoreactivity was used to index neuronal activation in 15 regions of interest. Ethanol had little effect on c-Fos activation. In adolescents, social context activated an “autonomic” network including the basolateral and central amygdala, bed nucleus of the stria terminalis, lateral hypothalamus, and lateral septum. In contrast, when adult rats were alone, activation was evident in a “reward” network that included the substantia nigra, nucleus accumbens, anterior cingulate and orbitofrontal cortices, lateral parabrachial nucleus, and locus coeruleus. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Conduct disorder (CD) and depression co-occur at far greater levels than chance, despite largely separate diagnostic criteria. One potential shared mechanism of this comorbidity is emotion dysregulation, which characterizes both internalizing and externalizing disorders. Previous research demonstrates that respiratory sinus arrhythmia (RSA)—a peripheral biomarker of emotion regulation—is attenuated among children with CD, and among children with depression. However, few studies have examined biomarkers of emotion regulation as a function of heterotypic comorbidity. We evaluated longitudinal patterns of RSA and RSA reactivity to emotion evocation across three annual assessments among 207 children diagnosed at ages 8–12 years with CD (n = 30), depression (n = 28), comorbid CD and depression (n = 80), or no psychiatric condition (n = 69). Using continuous symptom counts as predictors, Depression × CD interactions were observed for both Time 1 resting RSA and Time 1 RSA reactivity. CD, depression, and their interaction were all associated with low resting RSA at Time 1. In addition, concurrently elevated CD and depression scores predicted the greatest RSA reactivity to emotion evocation. Psychopathology scores were unrelated to developmental changes in RSA and RSA reactivity over time. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Rabbits nurse inside a nest once/day for 3–5 min. We quantified mother's time inside the nest box (TINB) and milk output as we varied the number and age of pups across lactation. TINB was larger and milk output smaller on lactation days 2, 3, 7, or 8, when one pup (2–3 days old) was provided, but normal on Days 4–6, when suckling eight pups. Maintaining 1, 2, or 6–8 growing pups across 30 days increased TINB in the first two groups without modifying milk intake/pup. Substituting a 15 day-old for a newborn increased TINB (Days 15–20) and decreased milk intake/pup (Days 15–30). Substituting for a newborn on Days 5, 9, 13, 17, 21, 25, and 29 increased TINB on such days and revealed a gradual decline in TINB on the “non-switch” days. Litter size, age, and lactation stage interact to determine TINB and milk output. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

This study examined changes in the acoustic and temporal structure of ultrasonic vocalizations as a function of age and correlated acoustic changes with vocal fold microstructure. Ultrasonic vocalizations were recorded in three age groups of male rats: aged (24–26 months), middle-aged (17–18 months), and young (4–5 months). Acoustic and structural changes in vocal fold tissue were evident by 18 months of age. Histological analyses revealed decreased density of elastin and hyaluronic acid and increased collagen density in the middle-aged and aged groups compared to the young rats. Laryngeal microstructure correlated with some of the ultrasonic acoustic features. These results show that male Long Evans rats experience changes in ultrasonic acoustic structure by middle age, and these changes correlate with deterioration in laryngeal microstructure. Ultrasonic vocalizations can be used as a model system for age-related degeneration in vocal fold structure and function. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Imitation plays a critical role in social and cognitive development, but the social learning mechanisms contributing to the development of imitation are not well understood. We developed a new imitation task designed to examine social learning mechanisms across the early childhood period. The new task involves assembly of abstract-shaped puzzle pieces in an arbitrary sequence on a magnet board. Additionally, we introduce a new scoring system that extends traditional goal-directed imitation scoring to include measures of both children's success at copying gestures (sliding the puzzle pieces) and goals (connecting the puzzle pieces). In Experiment 1, we demonstrated an age-invariant baseline from 1.5 to 3.5 years of age, accompanied by age-related changes in success at copying goals and gestures from a live demonstrator. In Experiment 2, we applied our new task to learning following a video demonstration. Imitation performance in the video demonstration group lagged behind that of the live demonstration group, showing a protracted video deficit effect. Across both experiments, children were more likely to copy gestures at earlier ages, suggesting mimicry, and only later copy both goals and gestures, suggesting imitation. Taken together, the findings suggest that different social learning strategies may predominate in imitation learning dependent upon the degree of object affordance, task novelty, and task complexity. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Variations in maternal care influence important life history traits that determine reproductive fitness. The adult female offspring of mothers that show reduced levels of pup licking/grooming (LG; i.e., low-LG mothers) show increased defensive responses to stress, accelerated pubertal development, and greater sexual receptivity than the female offspring of high-LG mothers. Amongst several species an accelerated pattern of reproductive development is associated with increased dominance-related behaviors and higher social rank. We hypothesize that rats from low-LG dams may thus also secure higher social rank as a means to compete for limited resources with conspecifics. In this study, social interactions were observed in triads of adult female rats aged p90 that received low, mid, and high levels of pup LG over the first week of life. Low- and mid-LG females had the highest pinning scores and high-LG rats the lowest, showing that low- and mid-LG adult females engage in greater play dominance-related behavior. Likewise, low- and mid-LG rats spent significantly more time drinking following 24 hr of water deprivation in a water competition test thus allowing them to secure a limited resource more easily than high-LG rats. Interestingly, pinning by play dominant females was increased when subordinates were sexually receptive (proestrus/estrus), suggestive of a process of reproductive suppression. Some evidence suggests that low-LG and mid-LG rats also show greater fecundity than high-LG rats. Variations in maternal care may thus have a long-term influence on the development of play dominance and possibly social rank in the female rat, which might contribute to reproductive success within a competitive environment. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Distress-linked activation of the maternal hypothalamic–pituitary–adrenal (HPA)-axis is considered a pathway by which affect regulation impacts the fetal milieu and neurodevelopment. There is little direct evidence for this conceptual model. In 103 women [mean age 27.45 (±5.65) years] at 36–38 weeks gestation, salivary cortisol was measured before/after stress tasks; distress questionnaires were completed. At 18.49 (±1.83) weeks, infants underwent the Harvard Infant Behavioral Reactivity Protocol assessing cry/motor responses to novelty; women reported on infant behavior and postnatal distress. Prenatal cortisol and distress were not significantly correlated (all ps > .10). Proportional odds logistic regressions showed that neither prenatal nor postnatal distress was associated with infant responses to the Harvard Protocol yet pre-stress cortisol and maternal age were: The odds of being classified as High Reactive were 1.60 times higher [95% CI: 1.04, 2.46] for each unit of added cortisol and .90 times lower [95% CI: .82, .99] for every additional year in maternal age. No associations were found between cortisol or prenatal distress and mother-rated infant behavior; postnatal distress was positively associated with mother-rated infant negative behavior (p = .03). Observer and mother-rated infant behavior were not associated (all ps > .05). Based on independent observations of infants in contrast to maternal perceptions, these results lend support to the hypothesis that pregnant women's HPA-axis activity influences infant behavior. The impact of maternal distress was not supported, except in so far as postnatal distress may increase the likelihood of making negative judgments about infant behavior. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Repeated exposure to psychostimulant drugs is associated with long-lasting changes in cognition, particularly in behavioral tasks that are sensitive to prefrontal cortex function. Adolescents may be especially vulnerable to these drug-induced cognitive changes because of the widespread adaptations in brain anatomy and function that are characteristic of normal development during this period. Here, we used a differential reinforcement of low rates of responding task in rats to determine if amphetamine (AMPH) exposure during adolescence would alter behavioral inhibition in adulthood. Between postnatal days (PND) 27 and 45, rats received every other day injections of saline or AMPH (3 mg/kg). At PND 125, rats were trained progressively through a series of four reinforcement schedules (DRL 5, 10, 15, and 30 s) that required them to withhold responding for the appropriate amount of time before a lever press was reinforced. Relative to controls, AMPH-treated rats displayed transient deficits in behavioral inhibition (i.e., decreases in efficiency ratio) that were only evident at DRL 5. In addition, they had increased responding during nonreinforced periods, which suggested increased perseveration and propensity to attribute incentive salience to reward-paired cues. Following challenge injections with AMPH (.25–1 mg/kg, i.p.), which were given 10 min before the start of DRL 30 test sessions, both groups exhibited dose-dependent decreases in efficiency. These results suggest that AMPH-induced alterations in incentive-motivation and perseveration are more robust and longer-lasting than its effects on impulse control. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The human fetus learns about its chemosensory environment and this influences its behavior at birth and during the nursing period. This study examined whether prenatal experience could influence behavior much later in life. The dietary preference of two groups of children (8- to 9-years old) was examined. Mothers of one group had consumed garlic during pregnancy, mothers of the control group had not. Children received two tests, 1 month apart, of a meal containing two portions of potato gratin, one flavored with garlic. The total amount of potato, and the percentage of garlic flavored potato, eaten was calculated and examined separately by ANOVA for factors of prenatal exposure, the child's sex, and trial. Children prenatally exposed to garlic ate significantly more garlic flavored potato and a significantly greater overall amount of potato on trial 2, compared to controls. The results demonstrate prenatal experience may affect behavior well into childhood. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

In order to characterize the short- and long-term effects of repeated stressor exposure during adolescence, and to compare the effects of using two sources of cat odor as stressor stimuli, male and female adolescent rats (postnatal day (PND) ∼ 38–46) were exposed on five occasions to either a control stimulus, a cloth stimulus containing cat hair/dander, or a section of cat collar previously worn by a cat. Relative to control stimulus exposure, activity was suppressed and defensive behavior enhanced during exposure to either cat odor stimulus (most pervasively in rats exposed to the collar). Only cloth-exposed rats showed elevated levels of corticosterone (CORT), and only after repeated stressor exposure, but interestingly, rats exposed to the collar stimulus during adolescence continued to show increased behavioral indices of anxiety in adulthood. In this group, the time an individual spent in physical contact with a cagemate during the final adolescent exposure was negatively related to stress-induced CORT output in adulthood, which suggests that greater use of social support during adolescent stress may facilitate adult behavioral coping, without necessitating increased CORT release. These findings demonstrate that adolescent male and female rats respond defensively to cat odor stimuli across repeated exposures and that exposure to such stressors during adolescence can augment adult anxiety-like behavior in similar stressful conditions. These findings also suggest a potential role for social behavior during adolescent stressor exposure in mediating long-term outcomes. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

The intrauterine environment can impact the developing infant by altering the function of the placenta through changes to the epigenetic regulatory features of this tissue. Genetic variation, too, may impact infant development or may modify the relationship between epigenetic alterations and infant outcomes. To examine the associations of these variations with early life infant neurodevelopment, we examined the extent of DNA methylation of the glucocorticoid receptor gene (NR3C1) promoter and a common single nucleotide polymorphism in the promoter region in a series of 186 placentas from healthy newborn infants. We associated these molecular features with specific summary measures from the NICU Network Neurobehavioral Scales. After controlling for genotype and confounders, we identified significant associations of NR3C1 methylation with infant quality of movement (p = .05) and with infant attention (p = .05), and a potential interaction between methylation and genotype on infant attention score. These results suggest that epigenetic alteration of the NR3C1 gene in the placentas of genetically susceptible infants can have impacts on neurodevelopment which may have lifelong impact on neurobehavioral and mental health outcomes. Further research is needed to more precisely define these relationships and the interaction between epigenetic alterations and genetic variations on infant health. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

This study was undertaken to determine whether altered early serotonin signaling either via gestational serotonin reuptake inhibitor (SRI) exposure or genetic variations in the serotonin transporter promoter region (SLC6A4) alters levels of reelin, an important glycoprotein in neurodevelopment, in mothers and their neonates. Serum reelin protein expression was quantified by immunoblot from maternal and neonatal blood collected at delivery from women taking either an SRI during gestation or controls. SRI-exposed mothers had higher levels of one reelin fragment, while SRI-exposed neonates had lower total reelin levels, particularly in females and reelin levels differed with SLC6A4 genotype. Lower neonatal reelin levels predicted less time spent sleeping and more irritability during neonatal behavioral assessment on Day 6 of life. Our results suggest that prenatal SRI exposure and the SLC6A4 genotype influences reelin protein expression in both the mother and newborn and that this may be reflected in neonatal behavior. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Little is known about factors that promote optimal development of executive function (EF) skills. The focus of this study was associations among early maternal behaviors, infant frontal brain electrical activity, and child EF at age 4 and following kindergarten. Infant frontal electroencephalogram was collected from 56 infants at 10 months of age and maternal positive affect was observed. Children completed EF measures in the research laboratory at age 4; parental-reported EF was obtained following children's kindergarten year. Maternal positive affect and infant frontal brain electrical activity measured when the children were 10 months jointly and uniquely predicted both preschool and post-kindergarten EF. Findings suggest parenting behavior and brain development in infancy are precursors of later self-regulatory EF abilities. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Event-related potentials (ERPs) may be particularly useful for examining emotional processing across development. Though a number of ERP components are sensitive to emotional content in adults, previous studies have yet to systematically examine the components sensitive to emotion in children. The current study used temporal–spatial principal components analysis (PCA) to identify ERP components in response to complex emotional images in 9-year-old children. Three components were modulated by emotional content and were similar to those previously observed in adults, including: the early posterior negativity, the P300, and a sustained relative positivity similar to the late positive potential (LPP). Compared to those previously observed in adults, the components sensitive to emotion in children were maximal over more occipital regions and the LPP component appeared to be less protracted in time, perhaps indicative of less elaborative processing of emotional stimuli. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Sleep, the brain and the ability to interact with the environment change a great deal over the first year of life; however, there are no studies on the possible influence of different environmental stimulations on the organization of subsequent sleep–wake cycles in infants. The hypothesis of this study was that greater continuity of contingent tactile stimulation decreases crying behavior, subsequent active sleep (AS) and its fragmentation, and increases smiling behavior and subsequent quiet sleep in newborns. Forty out of the 82 newborns (15- to 30-hr old) of the initial sample satisfied the inclusion criteria and completed the first cycle of sleep during the period between two feedings. The 40 newborns were randomly assigned to four groups after 2′ of baseline observation: continuous stimulation (CS, n = 10); discontinuous nonperiodic stimulation (DnPS, n = 10); discontinuous periodic stimulation (DPS, n = 10); absent stimulation (AbS, n = 10). During baseline measurements, there were no significant differences in crying and smiling behaviors between the four groups, while during the subsequent stimulated wake, the CS group compared to the DnPS group showed more smiling (p < .05) and less crying (p < .05), longer poststimulation wake before sleep (p < .01) as well as AS with a lower percentage of grouped-rapid eye movements [grouped REM (GREM); p < .001]. The number of GREM during AS was negatively correlated to the number of smiles (p < .05) and positively to the number of cries (p < .05) of the previous stimulated wake. These findings suggest that, after birth, different continuity levels of contingent tactile stimulations may affect crying and smiling behaviors and the organization of behavioral states. AS could have an important role in processing affective states. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Neonatal handling is an experimental procedure used to understand how early-life adversity can negatively affect neurobehavioral development and place animals on a pathway to pathology. Decreased preference for the maternal odor during infancy is one of many behavioral deficits induced by neonatal handling. Here, we hypothesize that deficits in maternal odor preference may interfere with partner preference in the adult. To test this hypothesis, we assessed infant maternal odor preference and adult partner preference in different reproductive stages in both male and female rats that received neonatal handling. Our results indicate that only neonatally handled females present deficits in maternal odor preference during infancy, but both male and females present deficits in adult partner preference. However, sexual experience was effective in rescuing partner preference deficits in males. These results indicate that, considering infant and adult social interactions, females are more susceptible to the effects of neonatal handling than males. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

In rodents, voluntary exercise and environmental complexity increases hippocampal neurogenesis and reverses spatial learning and long-term potentiation deficits in animals prenatally exposed to alcohol. The present experiment extended these findings to neonatal alcohol exposure and to delay, trace, and contextual fear conditioning. Rats were administered either 5.25 g/kg/day alcohol via gastric intubation or received sham-intubations (SI) between Postnatal Day (PD) 4 and 9 followed by either free access to a running wheel on PD 30–41 and housing in a complex environment on PD 42–72 (wheel-running plus environmental complexity; WREC) or conventional social housing (SHSH) from PD 30 to 72. Adult rats (PD 80 ± 5) received 5 trials/day of a 10-s flashing-light conditioned stimulus (CS) paired with .8 mA footshock either immediately (delay conditioning) or after a 10-s trace interval (trace conditioning) for 2 days. Neonatal alcohol exposure impaired context and trace conditioning, but not short-delay conditioning. The WREC intervention did not reverse these deficits, despite increasing context-related freezing in ethanol-exposed and SI animals. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Dysregulated tonic pupil size has been reported in autism spectrum disorder (ASD). Among the possible sources of this dysregulation are disruptions in the feedback loop between norepinephrine (NE) and hypothalamic systems. In the current study, we examined afternoon levels of salivary alpha-amylase (sAA, a putative correlate of NE) and cortisol (used to assess stress-based responses) in two independent samples of children with ASD. We found a larger pupil size and lower sAA levels in ASD, compared to typical and clinical age-matched controls. This was substantiated at the individual level, as sAA levels were strongly correlated with tonic pupil size. Relatively little diurnal variation in sAA taken in the home environment in the ASD group was also observed, while typical controls showed a significant linear increase throughout the day. Results are discussed in terms of potential early biomarkers and the elucidation of underlying neural dysfunction in ASD. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Maternal discipline is an important predictor of child committed compliance. Maternal stress can affect both parenting and child development. In a large population-based cohort study (N = 613) we examined whether maternal discipline mediated the association between maternal stress during pregnancy and child compliance, and whether COMT or DRD4 polymorphisms moderated the association between maternal discipline and child compliance. Family-related and general stress were measured through maternal self-report and genetic material was collected through cord blood sampling at birth. Mother–child dyads were observed at 36 months in disciplinary tasks in which the child was not allowed to touch attractive toys. Maternal discipline and child compliance were observed in two different tasks and independently coded. The association between family stress during pregnancy and child committed compliance was mediated by maternal positive discipline. Children with more COMT Met alleles seemed more susceptible to maternal positive discipline than children with more COMT Val alleles. © 2012 Wiley Periodicals, Inc. Dev Psychobiol

Perinatal mammals show spontaneous movements that often appear random and uncoordinated. Here, we examined if spontaneous limb movements are responsive to a proprioceptive manipulation by applying a weight unilaterally to a forelimb of postnatal day 0 (P0; day of birth) and P1 rats. Weights were calibrated to approximate 0%, 25%, 50%, or 100% of the average mass of a forelimb, and were attached at the wrist. P0 and P1 pups showed different levels of activity during the period of limb weighting, in response to weight removal, and during the period after weighting. Pups exposed to 50% and 100% weights showed proportionately more activity in the nonweighted forelimb during the period of weighting, suggesting a threshold for evoking proprioceptive changes. Findings suggest that newborn rats use movement-related feedback to modulate spontaneous motor activity, and corroborate studies of human infants that have suggested a role for proprioception during early motor development. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 323–333, 2013

The effect of maternal depressive disorder on infant daytime cortisol production was studied in three groups of infants; one group with mothers with comorbid depression and anxiety (n = 19), a second group with mothers with depression only (n = 7), and a third group with non-depressed mothers (n = 24). The infants' cortisol production pattern was measured when they were 6, 12, and 18 months old in combination with repeated measures of parenting stress and depression symptoms. Multilevel modeling analyses showed that infants of mothers with comorbid depression and anxiety had relatively higher cortisol production from morning to bedtime and higher bedtime values as compared to infants of non-depressed mothers and infants of depressed only mothers when they were 6 and 12 months old, but not when 18 months old. The results were interpreted in light of possible changes in the infants' stress regulatory capacities or changes in maternal coping strategies at infant age 18 months. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 334–351, 2013

The developing hippocampus is particularly vulnerable to the toxic effects of alcohol, and behavioral deficits on hippocampus-dependent tasks have been reported following neonatal alcohol exposure in rodents. Previously, we have found that trace fear conditioning (a hippocampus-dependent learning task) is disrupted in rats exposed to alcohol during postnatal days (PD) 4–9, although delay fear conditioning is not. The present study indicates that this impairment in trace fear conditioning, previously only measured during adolescence, persists into adulthood but only in females. Animals were exposed to 5.0 g/kg/day alcohol on PD 4–9 and were trained on either PD 30 or 65. Alcohol exposure significantly impaired trace conditioning in both sexes at PD 30. In animals trained as adults, the deficit in trace was only observed in female subjects, suggesting that although males exhibit an age-related recovery of function, alcohol-induced trace conditioning deficits are more persistent in female Sprague–Dawley rats. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 352–360, 2013

The study aim was to compare sleep, sleepiness, fatigue, and neurobehavioral performance among first-time mothers and fathers during their early postpartum period. Participants were 21 first-time postpartum mother–father dyads (N = 42) and seven childless control dyads (N = 14). Within their natural environment, participants completed 1 week of wrist actigraphy monitoring, along with multi-day self-administered sleepiness, fatigue, and neurobehavioral performance measures. The assessment week was followed by an objective laboratory-based test of sleepiness. Mothers obtained more sleep compared to fathers, but mothers' sleep was more disturbed by awakenings. Fathers had greater objectively measured sleepiness than mothers. Mothers and fathers did not differ on subjectively measured sleep quality, sleepiness, or fatigue; however, mothers had worse neurobehavioral performance than fathers. Compared to control dyads, postpartum parents experienced greater sleep disturbance, sleepiness, and sleepiness-associated impairments. Study results can inform social policy, postpartum sleep intervention development, and research on postpartum family systems and mechanisms that propagate sleepiness. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 361–372, 2013

The current study was conducted to characterize the ontogeny of novel object recognition in rats. Initial testing (Experiment 1) was conducted in a square arena and it was observed that 21-day-old animals would often pause in the corners, greatly increasing between-subject variability and performance in this test. Significantly greater object exploration and less variability were obtained using a circular arena. In Experiment 2, we report object exploration in 21, 35, 42, and 90-day-old male and female Sprague-Dawley rats using a circular arena. The results show that measures of locomotor activity, object exploration, and within session habituation of these behaviors were surprisingly similar across all ages. Gender differences in locomotor activity were not observed until 42 days of age. Reliable recognition memory was observed at all ages. It is concluded that the novel object recognition test appears well suited for use in young rats. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 373–381, 2013

Trajectories of baseline RSA (respiratory sinus arrhythmia), an index of reactivity, and vagal withdrawal, an index of regulation, across the preschool period were examined. In addition, maternal emotional support was investigated as a potential time-varying predictor of these trajectories. Physiological measures were obtained during frustration tasks, and a maternal emotional support measure was assessed via maternal report and direct observation. Children's baseline RSA and vagal withdrawal scores were moderately stable across the preschool period. Growth models indicated that children's baseline RSA scores changed linearly over the preschool years, and there was significant variability in withdrawal trajectories. Greater maternal emotional support predicted higher initial withdrawal levels and lower emotional support was associated with the greatest increase in withdrawal over time. This suggests that children of higher emotionally supportive mothers reached higher levels of physiological regulation earlier in development and therefore did not show the same increase across preschool as children of less supportive mothers. Maternal emotional support was not significantly related to trajectories of baseline RSA. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 382–394, 2013

During isolation in a novel environment, guinea pig pups gradually begin to display passive behavior that appears to be mediated by proinflammatory activity, that is, “sickness behavior.”. Administration of substances that increase proinflammatory activity [corticotropin-releasing factor (CRF), lipopolysaccharide (LPS)] prior to isolation induces passive behavior from the beginning of the isolation episode. Here, we show that reunion with the mother in the novel environment rapidly and potently suppresses the passive behavior of isolated pups (Experiment 1); inhibits the passive behavior of pups administered CRF (10 µg, subcutaneous; Experiment 2); and inhibits the passive behavior of male, though not female, pups administered LPS (250 µg/kg, intraperitoneal; Experiment 3). Together these findings suggest that the presence of the mother either recruits other processes that moderate the impact of proinflammatory processes on brain mechanisms mediating the passive response or initiates compensatory mechanisms that counter the effect of proinflammatory activity. Further, the results suggest that for physically ill animals of social species, the adaptive advantage that accrues from maintaining normal social interactions may sometimes outweigh the advantage gained by engaging in sickness behavior. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 395–403, 2013

Complexity in motor behavior is a hallmark of healthy systems. The purpose of this study was to investigate postural complexity during development of early motor behaviors and under two conditions. Twenty-two infants participated from 1 to 6 months of age. Linear and nonlinear measures of displacement of the center of pressure at the base of support were used to quantify magnitude and temporal structure of postural control. Behavioral coding was used to quantify the emergence of midline head control and early reaching. Results suggest that infants have complexity in postural control strategies early in development. This complexity decreases as infants learn motor behaviors, even when magnitude of the postural variability does not change. Infants were able to adapt the magnitude of postural control variability under different conditions. We propose that infants proceed through three stages which support the infant's ability to adapt motor behaviors. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 404–414, 2013

Adolescence is a developmental period of particular importance given the host of neurobiological changes that occur during this stage of development. Drug use and abuse is said to be a function of the balance of its rewarding and aversive effects, and any age-dependent differences in morphine's aversive effects could impact drug intake. The present experiments examined the ability of morphine sulfate (0, 3.2, 10, and 18 mg/kg) to induce taste aversions in adolescent and adult rats under high (20-min fluid access each day; Experiment 1A/B) and low (50% of ad libitum access; Experiment 2A/B) deprivation conditions. In both studies, adolescent and adult rats were given a novel saccharin solution to drink and were subsequently injected with morphine. Independent of the deprivation condition, adults acquired stronger aversions than adolescents and did so at a faster rate. On a subsequent two-bottle aversion test, all morphine-injected subjects drank a significantly lower percentage of saccharin than vehicle-injected controls with adults exhibiting stronger aversions than adolescents. These age-dependent differences in morphine-induced CTAs extend the findings with other drugs of abuse for which adolescents exhibit weaker aversions. The possible basis for and implications of these differences were discussed. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 415–428, 2013

Adolescent rats exhibit ethanol-induced locomotor activity (LMA), which is considered an index of ethanol's motivational properties likely to predict ethanol self-administration, but few studies have reported or correlated ethanol-induced LMA with conditioned place preference (CPP) by ethanol at this age. The present study assessed age-related differences in ethanol's motor stimulating effects and analyzed the association between ethanol-induced LMA and conventional measures of ethanol-induced reinforcement. Experiment 1 compared ethanol-induced LMA in adolescent and adult rats. Subsequent experiments analyzed ethanol-induced CPP and conditioned taste aversion (CTA) in adolescent rats evaluated for ethanol-induced LMA. Adolescent rats exhibit a robust LMA after high-dose ethanol. Ethanol-induced LMA was fairly similar across adolescents and adults. As expected, adolescents were sensitive to ethanol's aversive reinforcement, but they also exhibited CPP. These measures of ethanol reinforcement, however, were not related to ethanol-induced LMA. Spontaneous LMA in an open field was, however, negatively associated with ethanol-induced CTA. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 429–442, 2013

The aim of this study was to examine the development of active controlled memory retrieval in children. Active retrieval is an effortful retrieval required to disambiguate information stored in memory. Brain imaging studies and monkey experiments have shown that the ventrolateral prefrontal cortex (VLPFC) is specifically engaged in this retrieval in both adult humans and monkeys. Three groups of 6-, 8-, and 11-year-old children and adults were tested on an active retrieval task. Results showed a marked difference in performance between 6-year olds, who made more errors and had longer response time, and 8- and 11-year olds, who had performance similar to adults. These results provide evidence that the VLPFC and the network supporting its top–down modulation undergo substantial maturational changes between 6 and 8 years old, giving children better active control of visual memory. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 443–449, 2013