Effect of MAO A deficiency on different kinds of aggression and social investigation in mice

Monoamine oxidase A (MAO A) degrades serotonin, dopamine and noradrenaline, factors critically involved in the regulation of aggression. Different kinds of aggression were investigated in Tg8, a transgenic mouse strain lacking a functional MAO A gene. MAO A-deficient mice differ from wild-type C3H/HeJ (C3H) in terms of showing higher territorial, predatory and isolation-induced aggression. Tg8 demonstrated shorter latencies to cricket killing and to the first attack after 6 weeks isolation than C3H mice. In the resident-intruder paradigm, MAO A-lacking mice were more aggressive than C3H when tested as intruders. In contrast to C3H, attack in Tg8 mice did not depend on different aggressiveness of intruders of BALB/c, A/Sn and C3H strains. Tg8 mice displayed no increase in aggression but demonstrated reduced social investigation towards anesthetized, as well as towards juvenile BALB/c males. Thus, MAO A deficiency in Tg8 mice is accompanied by increased expression of different kinds of aggression, as well as by disruption of normal pattern of social interaction.     

Multimodal Treatments for Childhood Attention-deficit/Hyperactivity Disorder: Interpreting Outcomes in the Context of Study Designs

The goal of this article was to outline issues critical to evaluating the literature on incremental benefit of multiple effective treatments used together, vs. a single effective treatment, for childhood ADHD. These issues include: (1) sequencing and dosage of treatments being combined and compared; (2) difficulty drawing valid conclusions about individual components of treatment when treatment packages are employed; (3) differing results emerging from measurement tools that purportedly measure the same domain; and (4) the resultant difficulty in reaching a summary conclusion when multiple outcome measures yielding conflicting results are used. The implications of these issues for the design and conduct of future studies are discussed, and recommendations are made for future research.     

Generating Relations Elicits a Relational Mindset in Children

Relational reasoning is a hallmark of human higher cognition and creativity, yet it is notoriously difficult to encourage in abstract tasks, even in adults. Generally, young children initially focus more on objects, but with age become more focused on relations. While prerequisite knowledge and cognitive resource maturation partially explains this pattern, here we propose a new facet important for children's relational reasoning development: a general orientation to relational information, or a relational mindset. We demonstrate that a relational mindset can be elicited, even in 4‐year‐old children, yielding greater than expected spontaneous attention to relations. Children either generated or listened to an experimenter state the relationships between objects in a set of formal analogy problems, and then in a second task, selected object or relational matches according to their preference. Children tended to make object mappings, but those who generated relations on the first task selected relational matches more often on the second task, signaling that relational attention is malleable even in young children.     

Serotonin's influence on predatory behavior of highly aggressive cba and weakly aggressive DD strains of mice

The effects of serotonin were studied on locust-killing behavior of mice from low (DD) and high (CBA) predatory aggressive strains. 5-HTP injected intraperitoneally (50 and 100 mg/kg) or 5-HT administered into the lateral ventricle (10 μg) significantly reduced locust-killing behavior in highly aggressive CBA mice. Imipramine (20, 30, and 40 mg/kg) elicited a dose-dependent inhibitory effect on predatory behavior. Fluoxetine (10 and 20 mg/kg) alone had a slight influence on locust-killing behavior but potentiated the action of the subthreshold dose of 5-HTP (25 mg/kg). Pretreatment with the blocker of 5-HT₂ type receptors methysergide (2 mg/kg) abolished the inhibitory effect of 5-HTP. These finding indicate that serotonin of the brain exerts an inhibitory effect on predatory behavior in mice. In contrast, neither lesion of the dorsal raphe nucleus (although significantly depleting the brain serotonin) nor treatment with methysergide (2 mg/kg) induced locust-killing behavior in weakly aggressive DD mice. Low predatory aggressiveness in DD mice is suggested to be related to the low tonus of the mechanisms activating killing behavior rather than to excessive serotonergic inhibitory influences.     

Perceptions of the Targets and Sources of COVID-19 Threat are Structured by Group Memberships and Responses are Influenced by Identification with Humankind

The purpose of this study was to investigate which social groups are perceived as a threat target and which are perceived as a threat source during the COVID-19 outbreak. In a German sample (N = 1454) we examined perceptions of social groups ranging from those that are psychologically close and smaller (family, friends, neighbors) to those that are more distal and larger (people living in Germany, humankind). We hypothesized that psychologically closer groups would be perceived as less affected by COVID-19 as well as less threatening than more psychologically distal groups. Based on social identity theorizing, we also hypothesized that stronger identification with humankind would change these patterns. Furthermore, we explored how these threat perceptions relate to adherence to COVID-19 health guidelines. In line with our hypotheses, latent random-slope modelling revealed that psychologically distal and larger groups were perceived as more affected by COVID-19 and as more threatening than psychologically closer and smaller groups. Including identification with humankind as a predictor into the threat target model resulted in a steeper increase in threat target perception patterns, whereas identification with humankind did not predict differences in threat source perceptions. Additionally, an increase in threat source perceptions across social groups was associated with more adherence to health guidelines, whereas an increase in threat target perceptions was not. We fully replicated these findings in a subgroup from the original sample (N = 989) four weeks later. We argue that societal recovery from this and other crises will be supported by an inclusive approach informed by a sense of our common identity as human beings.     

Issues in the identification and long-term management of Munchausen by Proxy Syndrome within a clinical infant service

Munchausen by Proxy Syndrome is a version of Munchausen's Syndrome whereby a parent, usually the mother, simulates or fabricates disease in one or more of her children in order to seek medical attention. Because this disorder is usually identified in pediatric settings, current literature focuses on identification of the syndrome, with little discussion of treatment issues or management strategies other than confrontation of the parent and removal of the child from the home. With the increased availability of infant mental health services, infant clinicians are likely to be called on to evaluate and treat cases of this disorder. This paper reviews the Munchausen by Proxy literature for infant clinicians and describes the identification and long-term management of one Munchausen by Proxy case within the context of an infant home-visiting service. Pertinent issues that emerged included the difficulties inherent in documenting the mother's pathological behavior, the clinical tension between preventing flight from treatment but limiting harmful behavior, the need for a long-term collaborative relationship with a designated pediatrician, and the importance of further education of protective service workers about this syndrome.     

Serotonin metabolism and serotonergic receptors in Norway rats selected for low aggressiveness to man

Selection of Norway rats (24–27 generations) for low aggressiveness to man resulting in the loss of aggressive responding to handling markedly influences the brain serotonergic system. In “domesticated” Norway rats levels of serotonin in the midbrain and hypothalamus and 5-hydroxyindole acetic acid in the hypothalamus were higher than in non-selected aggressive rats. The activity of the key enzyme in serotonin biosynthesis, tryptophan hydroxylase, in midbrain of rats with genetically determined lack of aggressiveness to man was higher than in aggressive animals, although there was no difference in tryptophan hydroxylase activity in the hypothalamus. B_max and K_D of [³H]spiperone-specific binding in frontal cortex membranes were increased in tame rats. No significant differences in B_max and K_D were found between “domesticated” and aggressive rats in [³H]serotonin binding in the frontal cortex.