Parental Stress and Children’s Social and Behavioral Outcomes: The Role of Abuse Potential over Time

Parental stress is a well-established risk factor for adverse child outcomes, including the development of aggression, externalizing behavior problems, and anxiety, as well as compromised emotional coping, impaired social cognition, and diminished treatment response. Abuse potential represents a mechanism by which parental stress may impact child social competence and behavior; evidence links parental stress to abuse potential, and abuse potential to a range of negative child social competence and behavioral outcomes. The current study assessed relationships between parental stress, abuse potential, and child social and behavioral outcomes over time. Parents of children ages 2–6 years (N?=?610, 44% girls) reported on perceived parental stress and attitudes towards abuse and neglect, as well as child social competence and behavior problems, before and after a caregiver-directed, community-based intervention. Changes in parental stress, abuse potential, and child social and behavioral outcomes were examined using panel analyses, while controlling for intervention effects and demographic variables. Parental stress predicted child social competence, anxiety/withdrawal, and anger/aggression over time; while the links between stress and anxiety/withdrawal, and stress and social competence, were mediated by child abuse potential, the link between stress and anger/aggression was not mediated by child abuse potential. Findings suggest that abuse potential represents a mechanism by which parental stress and child social and behavioral outcomes are linked. Further, screening for child social competence deficits may identify children at risk for abuse, as well as parents in need of services to reduce stress.     

The potential effects of protected nests and cage complexity on maternal aggression in house mice

I studied the behavior of nursing house mice (Mus musculus) in captivity and used a two-by-two factorial design to test the hypothesis that the combination of a protected nest along with a chance for the intruders to retreat would improve the ability of resident females to defend their litters from infanticidal males. A chance for the intruder to retreat was manipulated by testing the resident females in either a single- or a two-compartment cage. The effect of a protected nest was examined by providing females with a nest box having a narrow entrance. During each test, an infanticidal adult male was introduced into the cage of a resident female and her pups. I observed that neither the presence of a protected nest nor the chance for the intruders to retreat to a different compartment, or a combination of the two, increased the ability of a female to defend her litter against an intruder male. Moreover, neither of these two factors influenced the overall behavior of the resident females. I obtained similar results after using data from previous studies to examine the influence of both of these factors on the efficiency of maternal aggression. Overall, these two approaches showed that females are often unable to prevent intruders from committing infanticide. I discuss the validity of the hypothesis that maternal aggression evolved as a mechanism to protect offspring from infanticide. Aggr. Behav. 24:385–396, 1998. © 1998 Wiley-Liss, Inc.     

Gender differences in emotional and overt/covert aggressive responses to stress

We examined the role of stress exposure on gender differences in hostile (emotional and behavioral) reactions within the context of a laboratory paradigm. Aggressive behavior was indexed via the intensity (overt) and the duration (covert) of putative shocks delivered to a confederate. Half of the participants were exposed to a chronic stressor (high stress) and half were not (low stress). Participants' emotional responses were measured via self-report mood ratings before and after the experiment. Men displayed higher aggression in both stress conditions, which corresponded to their ratings of state hostility. On the other hand, women in high stress delivered lower intensity shocks, and this decreased overt aggression was positively correlated with sadness ratings. However, women did not decrease their levels of shock duration (covert aggression) under high stress and showed equivalent shock duration compared with men in high stress. These findings are discussed in terms of differential overt manifestations of distress between men and women.     

Chronic psychosocial factors and acute physiological responses to laboratory-induced stress in healthy populations: a quantitative review of 30 years of investigations

This meta-analysis included 729 studies from 161 articles investigating how acute stress responsivity (including stress reactivity and recovery of hypothalamic-pituitary-adrenal [HPA] axis, autonomic, and cardiovascular systems) changes with various chronic psychosocial exposures (job stress; general life stress; depression or hopelessness; anxiety, neuroticism, or negative affect; hostility, aggression, or Type-A behavior; fatigue, burnout, or exhaustion; positive psychological states or traits) in healthy populations. In either the overall meta-analysis or the methodologically strong subanalysis, positive psychological states or traits were associated with reduced HPA reactivity. Hostility, aggression, or Type-A behavior was associated with increased cardiovascular (heart rate or blood pressure) reactivity, whereas anxiety, neuroticism, or negative affect was associated with decreased cardiovascular reactivity. General life stress and anxiety, neuroticism, or negative affect were associated with poorer cardiovascular recovery. However, regarding the sympathetic nervous system and parasympathetic nervous system, there were no associations between the chronic psychosocial factors and stress reactivity or recovery. The results largely reflect an integrated stress response pattern of hypo- or hyperactivity depending on the specific nature of the psychosocial background.     

Strain‐specific aggressive behavior of male mice submitted to different husbandry procedures

Severe aggression within groups of male laboratory mice can cause serious welfare problems. Previous experiments have shown that the transfer of specific olfactory cues during cage cleaning and the provision of nesting material decrease aggression and stress in group‐housed male mice. In this study, the combined effect of these husbandry procedures was tested for their long‐term effect on aggression in two strains of male mice (BALB/c and CD‐1). We used postcleaning aggressive behavior, wound counts, and testosterone levels as indicators of aggressiveness. Physiological responses to social challenge were investigated through urinary corticosterone and adrenal tyrosine‐hydroxylase measurements. Furthermore, the aggression‐modulating effects of two enrichment items (ShepherdShack/DesRes and PVC tube) were explored. Marked differences were found between the two strains. CD‐1 mice were more aggressive, had higher testosterone levels but lower corticosterone levels, and had fewer wounds than BALB/c mice. However, in neither of the two strains was long‐term enrichment with nesting material and its transfer after cage cleaning effective in lasting reduction of intermale aggression. This may be explained by the fact that aggression levels were generally low. It seems that housing mice in small, socially stable groups or keeping social disturbances to a minimum considerably modulates aggression in group‐housed male mice. Mice of both strains housed in cages enriched with nesting material had lower urinary corticosterone levels than standard‐housed mice. We therefore conclude that the long‐term provision of nesting material, including the transfer of nesting material during cage cleaning, may enhance the welfare of laboratory mice. Aggr. Behav. 29:69–80, 2003. © 2002 Wiley‐Liss, Inc.     

Ontogeny of behavioral arousal: the role of environmental stimuli

During the course of ontogenesis the developing rat has been reported to pass through a transient period of intense behavioral arousal which peaks at 15 days of age, a phenomenon that has been interpreted to reflect a sequential caudal to rostral development of excitatory and inhibitory systems in the mammalian brain. In a series of four experiments it was shown (a) that this period of intense hyperactivity occurs only when the animal is tested alone in an unfamiliar environment, that the degree of arousal is proportional to the dissimilarity between the home cage and the test environment, and that isolation per se is insufficient to elicit the arousal response; (b) that environmental temperature has a minimal influence on the degree of behavioral arousal seen in either familiar of unfamiliar environments; (c) that unlearned responses to pheromonal or other naturally occurring nest odors do not suppress the high levels of locomotor activity evoked by unfamiliar environments in the 15-day old rat pup; and (d) that it is fear or distress evoked by the unfamiliar environment rather than curiosity that underlies this developmental phenomenon. It is concluded that the sequential increase and decrease in locomotor activity that occurs during ontogenesis cannot be used to support the principle of caudal to rostral development of excitatory and inhibitory centers in the central nervous system.     

Conspecific aggression influences food carrying: Studies on a wild population of Rattus norvegicus

Laboratory rats, like many other animal species, transport food. Their behavior is influenced by factors such as food size, the time required to eat, travel distance, travel difficulty, and the availability of cover, etc. Recent versions of optimal foraging theory suggest that species that display such behavioral patterns do so in order to minimize risk to predation while at the same time maximizing food gain. Nevertheless, it is not clear that this explanation applies to rats, nor is it easy to investigate this problem in a laboratory. The results of the present study on urban feral rats show that their food handling behavior is similar to that of domestic rats. The results also suggest that food carrying can serve defensive as well as communicative functions. Aggression around food sources was high. Smaller rats always carried food and some large rats infrequently carried food, suggesting that the food carrying by smaller, subordinate rats may help them avoid conspecific aggression. The rats also vigorously attempted to steal food that was carried home by conspecifics. This result suggests that food carrying can redistribute food resources and inform conspecifics about food availability. The results demonstrate the utility of multilevel behavioral analysis and also demonstrate that for rats, food transport has functions other than predator avoidance, including avoidance of conspecific aggression and communication about food availability. © 1996 Wiley-Liss, Inc.     

Maternal aggression in rats: Changes over pregnancy and lactation in a sprague-dawley strain

Maternal aggression in a Sprague-Dawley strain of laboratory rat (Charles River CD) was explored from Day 1 after mating on Day 0 through Day 24 of lactation (L0-L24). Aggression toward unfamiliar male “intruders” during 10-min tests was low among nonpregnant, nonlactating females and during the first 10 days of gestation. Frequency of attack on intruders increased moderately but significantly by Gestation Day 16 (G16; Experiment 1) or G21 (Experiment 2), a prepartum phenomenon not previously reported in laboratory rats. Levels of aggression were highest, however, during the first 9 days of lactation, when attacks averaged more than 6 per 10-min session. Attacks declined sharply in frequency after L14 and by L24 did not exceed levels observed among nonpregnant females. Experiment 3 examined the importance of the test site (home cage with nest and pups, if any, vs unfamiliar cage without nest or pups) to agonistic behavior associated with pregnancy and lactation. Late pregnant females tested in a novel cage were not aggressive; however, females tested shortly after delivering their pups were highly aggressive, averaging over four attacks per 5-min session. In novel cage tests frequency of attack remained high through L4 but declined significantly by L7. These data are consistent with the hypothesis that maternal aggression at its onset is primarily under hormonal control, but becomes increasingly dependent upon external factors, presumably pup stimulation, during the postpartum period.     

Effects of chronic social stress during lactation on maternal behavior and growth in rats

Maternal mood disorders such as depression and chronic anxiety can negatively affect the lives of not only mothers, but also of partners, offspring, and future generations. Chronic exposure to psychosocial stress is common in postpartum mothers, and one of the strongest predictors of postpartum depression is social conflict. The objective of the current study was to evaluate the effects of chronic social stress (CSS) during lactation on the maternal behavior (which consists of maternal care and aggression toward a novel conspecific) of lactating rats, as well as on the growth of the dams and their offspring. It was hypothesized that chronic daily exposure to a novel male intruder would alter the display of maternal behavior and impair growth in both the dam and offspring during lactation due to the potentially disruptive effects on maternal behavior and/or lactation. The data indicate that CSS during lactation attenuates maternal care and the growth of both dams and pups, and increases self-grooming and maternal aggression toward a novel male intruder. These results support the use of CSS as a relevant model for disorders that impair maternal behavior and attenuate growth of the offspring, such as postpartum depression and anxiety.     

Neurotoxic lesion of the rostral perirhinal cortex blocks stress-induced exploratory behavioral changes in male rats

Exposure to stress leads to adaptive responses including both behavioral and physiological changes. This process is induced by the activation of multiple brain regions. The present study examined the role of the rostral perirhinal cortex (rPRh) in behavioral changes following electrical foot shock-induced stress. The rPRh of rats was lesioned bilaterally by local microinjections of 10 microg N-methyl-D-aspartic acid (NMDA) before foot shocks (0.7 mA, 1 s). The effects of these lesions on foot shock-induced changes in exploratory behaviors were tested in the open field (4 h, 48 h, 72 h, and 14 days after foot shocks) and the light-dark box (7 days after foot shocks). Foot-shocked and sham-lesioned rats showed several well known behavioral changes in the open field (e.g., immobility, reduction of exploratory activity) most marked at 48 h after foot shocks, and the light-dark box (e.g., reduction of time spent and activity in the lit compartment). All these stress-induced behavioral changes were blocked by neurotoxic lesions of the rPRh. Furthermore, rPRh lesions did not affect behavior in the open field and the light-dark box in unstressed rats. Taken together, these data indicate that the rPRh is involved in neurophysiological mechanisms that mediate changes induced by foot-shock stress in exploratory behaviors which indicate unconditioned fear or anxiety.     

Gender-specific social experiences and the development of aggressive and sexual behavior in male mice

This study examined influences of gender-specific social experiences on the development of aggressive and sexual behavior in male mice. To determine the effects of gender-specific social experience three different types of groups were constituted after the animals had been weaned. The subjects were randomly assigned to different treatments. Female groups were composed of one experimental male and three female cohabitants. Male groups were composed of five experimental males each, and the mixed-sex groups were composed of two experimental males and of two females. The experimental subjects stayed in these groups until the age of approximately three months, when the testing for sexual and aggressive behavior commenced. For the sexuality tests, a receptive female was placed in the home cage of the experimental male for ten minutes. A nonaggressive male was placed in the home cage of the experimental male for seven minutes for the aggression tests. The experimental males were administered both sexuality and aggression tests, the sequence of testing sexual and aggressive behavior was systematically varied in order to control the influence of the two different types of behavioral tests. The results showed that males with only male social experiences showed fewer responses and were less active in both the aggression and sexuality tests than the males from the two other types of groups. Significant positive correlations between activity during aggression and sexual tests were obtained for all three groups. © 1994 Wiley-Liss, Inc.     

急性情绪应激对大鼠行为和脑神经颗粒素磷酸化水平的影响

为探讨急性情绪应激对大鼠旷场行为的影响,以及脑神经颗粒素（Neuroganin,NG）变化与应激性行为效应之间的相互关系。以急性不确定性空瓶刺激,建立情绪应激动物模型。将40只雄性SD大鼠随机分为情绪应激组1（ES1,接受情绪应激和旷场测试）、情绪应激组2（ES2,只接受情绪应激）、正常对照组1（C1,无情绪应激,但接受旷场测试）和正常对照组（C2,无情绪应激,也无旷场测试）（n=10）。以旷场行为和高架十字迷宫任务来评定大鼠应激后的行为变化,Western印迹杂交法（Western blotting）测定海马和前脑皮层中的NG含量和磷酸化水平。结果表明：（1） 应激后ES1组的水平活动增加,与C1组比较,差异有显著性, p<0.01;（2）ES1组海马和前脑皮层的NG磷酸化水平高于C1和C2组,差异有显著性, 均为p<0.05; ES2组的前脑皮层NG的磷酸化水平高于C1组,差异有显著性,为p<0.05;（3） 海马的NG磷酸化水平与水平活动之间的相关达显著水平。提示急性情绪应激能导致动物明显的行为改变如焦虑,这种行为改变可能与脑内NG磷酸化水平的变化有关。水平活动可能是反映急性情绪应激的较敏感行为指标,海马NG磷酸化水平可能是预测急性情绪应激所致焦虑或抑郁行为的较敏感生物学指标     

Individual and collective problem-solving in a foraging context in the leaf-cutting ant Atta colombica

In this paper we investigate the flexibility of foraging behavior in the leaf-cutting ant Atta colombica, both at the individual and collective levels, following a change in the physical properties of their environment. We studied in laboratory conditions the changes occurring in foraging behavior when a height constraint was placed 1 cm above part of the trail linking the nest to the foraging area. We found that the size and shape of the fragments of foraging material brought back to the nest were significantly modified when the constraint was placed on the trail: independent of their size, forager ants cut smaller and rounder fragments in the presence of a height constraint than in its absence. This size adjustment does not require any direct sensory feedback because it occurred when the ants cut fragments in the foraging area; no further cutting was done when they encountered the constraint. This points to the existence of a template that ants store and use as a reference to adjust their reach while cutting. Remarkably, despite the decrease in the foraging material brought to the nest per capita the colony was still able to improve its foraging performance by doubling the number of transporters. This study illustrates the flexibility of foraging behavior exhibited by an ant colony. It provides a rare example of insects finding an intelligent solution to a problem occurring in a foraging context, at both the individual and collective levels.     

Restraint increases both aggression and defence in female rats tested against same-sex unfamiliar conspecifics

Female rate living in groups were subjeccted to single and repeated immobllization stress (Restraint, RT). Twenty-four hours after RT, or the last RT session in the case of repeated RT, social behavior was recored in encounters with unfamilar females, matched for age and body weight. Single RT caused an increase in agonistic behavior in both its aggression and defence aspects. This was a specific effect, as other behaviors, including introductory, affiliative (Allo-Grooming), and courting items, were unifluenced by Rate The effect persisted and was even strengthened in the case of aggression, when RT was repeated once a day for 7 consecutive days. These findings, together with previous data showing a reduction in emotionality and an increase in the exploration of the physical environment following RT, suggest that in females mild stress may induce behavioral arousal, with the selective activation of specific social and non-social behavioral parameters. This contrasts with previous findings in male rats, which responded to RT with the depression of several behavioral parameters, including some of the items (aggresion, exploration) activated in females. As already found in males, in females some parameters were affected by repetition of treatment, either RT or control handing. This suggests that manipulation per se does affect social behavior. However, behavioral modifications ascribable to repeated manipulation in no way superimposed, and were clearly distinguish able from, those due to RT. © 1993 Wiley-Liss, Inc.     

Predation, aggression, and activity levels in food-deprived sunfish (Lepomis macrochirus and L. gibbosus): motivational interactions

Three experiments investigated the effects of food deprivation on several behavioral categories in two species of sunfish. In Experiment 1, predatory behavior and general activity were observed under five levels of deprivation. For both species, predation measures increased in a similar negatively accelerating manner with increasing deprivation, while activity changed in a more complex fashion. Experiment 2 examined the effects of deprivation on activity in a novel environment and showed that the deprivation effects of Experiment 1 were masked by the response to the new setting. In Experiment 3, measures of aggression toward intruders of each species were recorded from resident fish of both species under three levels of food deprivation. Both species were more aggressive toward conspecifics, and bluegills were more aggressive overall. Aggression was significatly influenced by food deprivation, with the effects dependent on the species making up the pair. Theories of motivational summation, generalized drive, and activity-mediated aggression were unable to explain the differential effects of hunger on the three behavioral categories observed. A dynamic boundary-state model of behavior control was found to predict the motivational interactions observed between distinct behavioral control systems.     

Chronic passive exposure to aggression escalates aggressiveness of rat observers

Previous studies have documented that exposure to aggression increases aggressiveness of human witnesses. However, the question of whether passive exposure to aggression can exclusively cause a risk of aggressive inclination for observers through a learning process, rather than mimicry effect, has not been readily addressed in the clinical literature. This study aimed to investigate this question by using a simple animal model to test the behavioral effect of chronic passive exposure to aggression. Our results indicate that observer rats that had been passively exposed to aggression for 10 min per day for 23 consecutive days exhibited more aggressive behavior than controls or those groups undergoing a single exposure to passive aggression. Furthermore, aggression levels in the group of 23‐day chronic exposure to aggression lasted 16 days after the recovery from exposure to aggression. These data suggest that the development of aggression in this model occurred through a learning process because only chronic exposure to aggression resulted in this behavioral outcome in the long run. Aggr. Behav. 36:54–66, 2010. © 2009 Wiley‐Liss, Inc.     

The effects of two response-elimination procedures on reinforced and induced aggression.

Pecks against a stuffed pigeon were reinforced according to a fixed-interval schedule for one group of pigeons and a variable-interval schedule for a second group. Red and green stimulus lights were alternately illuminated. Subsequently, food deliveries no longer occurred during one color (extinction). In the presence of the other color, food was presented only when no attack occurred for 30 sec. When attack produced food, all pigeons generally exhibited characteristic fixed-interval or variable-interval response patterns. Two birds in each group frequently exhibited postreinforcement schedule-induced aggression. Attack was reduced to low levels at approximately the same rate by extinction and differential reinforcement of other behavior. For birds that had previously exhibited schedule-induced aggression the initial reduction of attack during the second experimental phase was followed by induced attack immediately after food delivery in the differential-reinforcement-of-other-behavior component and upon onset of the extinction component, Either extinction or differential reinforcement of other behavior may eliminate reinforced aggression but may be relatively ineffective for reducing induced attack.     

Effects of septal-forebrain lesions on maternal aggression and maternal care

Septal-forebrain lesions significantly increased the defensive reactions of lactating Long-Evans rats (n = 13) relative to nonlesioned control females. The lesions greatly enhanced defensive behaviors on a number of standard tests (e.g., responsiveness to humans and anesthetized conspecifics) while abolishing aggression toward intruding male conspecifics. The lesions also produced a striking disruption in maternal behavior as evidenced by absence of nest building, reduced litter weights, failure to retrieve, lick, or nurse pups, and increased cannibalization. While these results cannot be interpreted as indicating that maternal aggression is equivalent to offense, they are congruent with such a view. Certainly they are not supportive of a view that maternal aggression is primarily defensive. The lesion-induced abolition of maternal attack may have resulted from an inhibition of offensive tendencies by heightened defensiveness and/or reduced pup stimulation. There was no evidence that the lesion-induced impairment in maternal behavior resulted from a failure to sequence the individual behavioral acts comprising maternal behavior. Rather, all features of maternal care seemed to be greatly attenuated.     

Effects of acute and chronic stress and of genotype on oxotremorine-induced locomotor depression of mice

The locomotor behavior of unstressed and stressed mice of two inbred strains, DBA/2 and C57/BL6, was investigated. Animals were tested in a toggle-floor box apparatus, 30 min after saline or oxotremorine treatment (ip). A dose of oxotremorine that did not depress the activity of na?ve mice (0.01 mg/kg) was chosen. Stressed mice were injected 24 h after either a single 2-h stress session (acute stress) or the last of 14 daily stress sessions of tube restraining (chronic stress). Acute stress did not modify the depressant effect of oxotremorine on locomotor behavior in either strain. On the contrary, chronic stress induced a clear sensitization of DBA but not C57 mice to the depressant effect of oxotremorine. These findings show that chronic stress may result in modifications of the cholinergic function, and its behavioral correlates, and that these changes are modulated by the genetic makeup.     

不同应激范式对大鼠行为和脑神经颗粒素含量的影响

为探讨慢性情绪应激、生理应激对大鼠旷场行为和脑神经颗粒素（Neurogranin,NG）含量的不同作用,以及NG含量变化与应激性行为效应之间的相互关系。分别以不确定性空瓶刺激和饮水剥夺,建立情绪应激和生理应激动物模型。将40只雄性SD大鼠随机分为情绪应激组（ES）、生理应激组（PS）、定时饮水组（C1）和正常对照组（C2）（n=10）。以旷场行为任务来评定大鼠应激后的行为变化,Western blotting方法测定海马和前脑皮层中的NG含量。结果表明：应激后四组大鼠海马的NG含量差异无显著性;ES组前脑皮层的NG含量低于C2组,差异具有显著性,p<0.01;PS组的前脑皮层NG含量也下降,但与C2组相比差异无显著性; 应激后ES组、PS组修饰行为多于C2组,差异具有显著性,分别为p<0.01,p<0.05;前脑皮层NG含量与修饰行为之间的相关达显著水平。提示慢性情绪和生理应激均能导致前脑皮层NG含量下降,修饰行为增加,情绪应激作用更显著。修饰行为可能是反映情绪状态的较敏感行为指标,前脑皮层NG水平可能是预测情绪应激所致焦虑或抑郁行为的较敏感生物学指标。