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PubMed2006

Resource holding potential, subjective resource value, and game theoretical models of aggressiveness signalling.

Empirical evidence suggests that aggressiveness (willingness to enter into, or escalate an aggressive interaction) may be more important than the ability to win fights in some species. Both empirical and theoretical traditions treat aggressiveness as a distinct property from the ability (RHP) or motivation (subjective resource value) to win a fight. I examine how these three traits are clearly distinct when modelled using a simple strategic model of escalation. I then examine game theoretical models of agonistic communication and demonstrate that models in which aggressiveness is signalled require: (1) a trait, aggressiveness, which is neither a correlate, nor consequence of RHP or motivation, (2) a handicap which negates any benefit to be gained through the use of a particular signal, and (3) the absence of any other asymmetry which could be used to assign roles to players. I conclude that it is unlikely that these assumptions are ever met, and that empirical examples of "aggressiveness" are far more likely to represent long-term differences in subjective resource value.

Aggression↗
PubMed2004

Effects of morphine and cocaine in mice with stable high aggressive and nonaggressive behavioral strategy.

The social group experience of mice with opposite aggressive and nonaggressive behavioral strategies was examined to modulate reinforcing effects of morphine and cocaine. Highly aggressive and nonaggressive male mice cohoused for long period in three-member groups were tested to self-administrate the drugs and to develop conditioned place preferring by them. Mouse triads formed by principle of descending aggression were used as a model of linear hierarchical group. The level of mouse aggression was identified previously within the stock group and during encounter with unknown intruder that continued to be stable over the time of experiment. Highly aggressive mice self-administered morphine and cocaine at higher unit concentrations (1.5 and 1.5 mg/ml) as compare with nonaggressive animals (0.5 and 0.25, 0.5, 1.0 mg/ml). Both morphine (2.5, 5.0, 10.0, and 20.0 mg/kg) and cocaine (2.5, 5.0, and 10.0 mg/kg) induced conditioned place preference in nonaggressive mice at all doses. In contrast, morphine had no effect in highly aggressive mice, while cocaine induced place conditioning at the highest doses (10 mg/kg) only. Our results illustrate that social experience in a stable group alter mouse sensitivity to the rewarding properties of drugs of abuse and social state should be taken into account in the experiments when social interactions are present.

Aggression↗
PubMed2005

Effects of oxytocin microinjected into the central amygdaloid nucleus and bed nucleus of stria terminalis on maternal aggressive behavior in rats.

The central effect of oxytocin (OT) on the aggressive behavior of lactating rats was studied. Female rats are more aggressive than nonlactating resident females, vigorously attacking conspecific intruder male or females. This behavior is considered important for pup protection against infanticide. The present work aimed to test the effects on maternal aggressive behavior of OT infused into the central amygdaloid nucleus (CeM) or bed nucleus of stria terminalis (BNST). The surgeries for bilateral cannula implantation were performed between the 2nd and 4th postpartum day. Three days after the surgery, saline or OT was infused and 5 min later a male intruder was placed in the home-cage and the behaviors were videotaped for 10 min. The frequency of the aggressive behaviors and the duration of locomotion during the aggressive behavior test were measured. The latency to retrieve the pups was also evaluated. The results showed that OT injected into CeM (10 and 20 ng/nucleus) decreased frequency of biting and frontal attack while in the BNST (10 and 20 ng/nucleus) decreased the frequency of biting. No significant change on retrieval activity was detected. OT in CeM and BNST has an inhibitory effect on the aggressive behavior of lactating female rats.

Aggression↗
PubMed2006

Aggressive behaviour and energy metabolism in a cichlid fish, Oreochromis mossambicus.

We have investigated the effect of mirror-elicited agonistic behaviour on oxygen consumption in the Mozambique tilapia, Oreochromis mossambicus (Cichlidae). Males exposed to their mirror image showed higher frequencies of both lateral display and tail-beating and escalated aggression more frequently than males exposed to a transparent glass that was used as a control for the presence of a novel object in the tank. This aggressive response was correlated with an increase in oxygen consumption. Overt aggression was highly correlated with display behaviour and with locomotor activity. Bivariate analyses showed high correlation (explaining about 64% of variation) between overt aggression, locomotor activity and metabolic rates. Weakly positive bivariate correlations between displays and metabolic rates turned spurious after partialling out aggression. The data suggest that energetic costs only emerge late during the conflict, when animals escalate their aggressive behaviour.

Aggression↗
PubMed2006

The critical role of familiar urine odor in diminishing territorial aggression toward a castrated intruder in mice.

Sensory chemo-signals conveying information on sex and familiarity are important to the manifestation of aggressive behaviors in male mice. In this study, we examined the role of familiarity conveyed by urine odor in the induction of aggressive behavior using a resident-intruder paradigm. First, an intact ICR male mouse (resident) was grouped with a castrated DBA mouse (cage-mate) and a female ICR mouse to allow the resident mouse to establish its territory. The resident male showed vigorous aggression, not only toward intact male DBA intruders, but also toward unfamiliar castrated DBA mice (UFC). In contrast, the aggression was markedly reduced toward its castrated DBA cage-mate. Next, to reveal how residents discriminate their cage-mates from unfamiliar intruders, we examined whether urine odor affected this familiarity-related aggression. When part of the body surface of a UFC was swabbed with the urine of a resident's cage-mate, the resident attacked the UFC much less often. These results suggest that the information about familiarity conveyed by urine odor plays an important role in controlling the territorial aggression of a resident male mouse toward castrated intruders.

Aggression↗
PubMed2004

Lack of association between the serotonin transporter promoter gene polymorphism and impulsivity or aggressive behavior among suicide attempters and healthy volunteers.

The association between a polymorphism in the promoter area of the serotonin transporter (17q11.1-q12) with impulsivity and history of aggressive behavior was studied in a Spanish general hospital. Subjects comprised 216 suicide attempters (152 women and 64 men) and 223 control blood donors (124 women and 99 men). They were classified as S individuals (s/s or s/l) with low expression of the serotonin transporter, and L individuals (l/l) with high expression. The genotype was not associated with high levels of impulsivity (measured with the Barratt Impulsiveness Scale) or history of aggressive behavior (measured with the Brown-Goodwin scale). This lack of association did not appear to be explained by lack of statistical power. High scores on the Barratt Impulsiveness Scale (BIS) and the Brown-Goodwin Aggressive Behavior Scale were associated with being an attempter, male gender and borderline personality disorder. While our Spanish suicide attempters and published US suicide attempters have similar BIS scores, our Spanish suicide attempters have significantly lower aggressive behavior scores. If cross-cultural differences in aggressive behavior scores are definitively established, country norms for aggressive behavior scales will need to be developed to compare genetic studies in different countries.

Adult↗
PubMed2004

Platelet serotonin content correlates inversely with life history of aggression in personality-disordered subjects.

The objective of this study was to test the hypothesis that platelet serotonin (5-hydroxytryptamine, 5-HT) content is correlated with measures of aggression in healthy human subjects. Platelet 5-HT content (ng/mg protein) was measured in personality-disordered (PD) and normal control (NC) subjects. Aggression was assessed with the Life History of Aggression (LHA), the Buss-Durkee Hostility Inventory (BDHI), and the Motor Aggression and Research Criteria for Intermittent Explosive Disorder (IED-IR); impulsivity was assessed with the Eysenck Personality Questionnaire II (EPQII) and the Barratt Impulsiveness Scale (BIS-11). LHA Aggression, but not impulsivity, scores showed significant inverse correlations with platelet 5-HT content in all subjects or in PD subjects alone. The findings in PD subjects remained significant after co-varying for race. PD subjects with IED-IR had lower platelet 5-HT content compared with PD subjects who did not have IED-IR, although this finding only approached significance after controlling for race. This study demonstrates an association between reduced platelet 5-HT content and aggression in PD subjects. Similar to other studies of platelet 5-HT markers, these data suggest that platelet 5-HT content may also reflect central 5-HT alterations and may be used as a biological marker in appropriate patient samples.

Aggression↗
PubMedDate not supplied

Effects of Snoezelen room, Activities of Daily Living skills training, and Vocational skills training on aggression and self-injury by adults with mental retardation and mental illness.

Multi-sensory stimulation provided in a Snoezelen room is being used increasingly for individuals with mental retardation and mental illness to facilitate relaxation, provide enjoyment, and inhibit behavioral challenges. We observed aggressive and self-injurious behavior in three groups of 15 individuals with severe or profound mental retardation and mental illness before, during, and after being in a Snoezelen room. All participants were receiving psychotropic medication for their mental illness and function-derived behavioral interventions for aggression, self-injury, or both. Using a repeated measures counterbalanced design, each group of participants was rotated through three experimental conditions: Activities of Daily Living (ADL) skills training, Snoezelen, and Vocational skills training. All other treatment and training activities specified in each individual's person-centered plan were continued during the 10-week observational period. Both aggression and self-injury were lowest when the individuals were in a Snoezelen room, followed by Vocational skills training and ADL skills training. The levels in the Snoezelen room were significantly lower than in both the other conditions for aggression but only in ADL skills training for self-injury. The difference in levels before and after Snoezelen were statistically significant with self-injury but not with aggression. The order of conditions showed no significant effect on either behavior. Snoezelen may provide an effective context for reducing the occurrence of self-injury and aggression.

Activities of Daily Living↗
PubMed2005

Amphetamine-induced aggression is enhanced in rats pre-treated with the anabolic androgenic steroid nandrolone decanoate.

Aggression is one of the most commonly reported psychiatric side effects among anabolic-androgenic steroids (AAS) users. Furthermore, anecdotal stories say the aggression is even more profound when a current, or former, AAS-user consumes other drugs of abuse such as amphetamine and alcohol. In the present study, we examined the effect of amphetamine on defensive reactivity and defensive aggression in Sprague-Dawley rats after chronic AAS treatment (daily intramuscular [i.m.] injections with 15 mg/kg nandrolone decanoate [ND] for 14 days). Defensive reactions in rodents occur in response to a real threat, but also to perceived provocation, for example, elicited by innocuous stimuli as reaction towards the experimenter. The defensive reactivity and aggression test employed in this study evaluates each rat's reaction towards four different stimuli (I: approach of a rod; II: startle to an air puff; III: poking with a rod at the flanks, and IV: capturing with a gloved hand) at two different occasions. Immediately following the ND treatment period, no change in the defensive response was found. Nevertheless, an amphetamine challenge given 3 weeks after the last ND or vehicle injection induced a marked increased defensive aggressive response in the ND, compared to vehicle-pre-treated rats. Both ND- and vehicle-pre-treated rats receiving amphetamine were found to be more aggressive than comparable groups receiving a saline injection. It can be concluded that pre-treatment with ND modulates the behavioral response to amphetamine and induces long lasting changes in the behavioral response.

Aggression↗
PubMed2005

Behavioral coping strategies in a cichlid fish: the role of social status and acute stress response in direct and displaced aggression.

The African cichlid fish, Astatotilapia burtoni, has a complex social system with a sophisticated social hierarchy that offers unique opportunities to understand how social rank and its physiological substrates relate to behavioral strategies. In A. burtoni, a small fraction of the males are dominant (T, territorial), as distinguished by being large, brightly colored, reproductively active, and aggressively defending territories. In contrast, the majority of males are non-dominant (NT, non-territorial), being smaller, drably colored, sexually immature, and typically schooling with females. The social system is regulated by aggressive interactions between males and behavioral responses to aggression can be direct or displaced with respect to the animal that acts. To determine whether direct and displaced behaviors are differentially exhibited by T and NT males, individuals were shown a video presentation of a dominant male displaying aggressively. Analysis of aggressive acts toward the video display and displaced activity toward a tank mate revealed that T males exhibited more direct behavior (toward the video display), while NT males engaged in more displaced behavior (toward tank mates). Because similar experiments with primates suggest that shifts in behavioral strategies are linked to changes in the stress response (as measured by circulating cortisol levels), we measured cortisol levels of T and NT males following exposure to the aggressive stimulus. Although in some animals subordinate males are reported to have higher cortisol levels, here we show that in A. burtoni the endocrine response to specific situations can vary considerably even among animals of the same status. Interestingly, NT males with intermediate cortisol levels showed more directed behavior while NT males with both high and low cortisol levels showed more displaced. This suggests an optimal physiological stress response in NT males that predisposes them to challenge aggressors perhaps making it more likely for them to ascend in status.

Acute Disease↗
PubMed2006

Steroid hormone mediation of limbic brain plasticity and aggression in free-living tree lizards, Urosaurus ornatus.

The neural mechanisms by which steroid hormones regulate aggression are unclear. Although testosterone and its metabolites are involved in both the regulation of aggression and the maintenance of neural morphology, it is unknown whether these changes are functionally related. We addressed the hypothesis that parallel changes in steroid levels and brain volumes are involved in the regulation of adult aggression. We examined the relationships between seasonal hormone changes, aggressive behavior, and the volumes of limbic brain regions in free-living male and female tree lizards (Urosaurus ornatus). The brain nuclei that we examined included the lateral septum (LS), preoptic area (POA), amygdala (AMY), and ventromedial hypothalamus (VMH). We showed that the volumes of the POA and AMY in males and the POA in females vary with season. However, reproductive state (and thus hormonal state) was incompletely predictive of these seasonal changes in males and completely unrelated to changes in females. We also detected male-biased dimorphisms in volume of the POA, AMY, and a dorsolateral subnucleus of the VMH but did not detect a dimorphism between alternate male morphological phenotypes. Finally, we showed that circulating testosterone levels were higher in males exhibiting higher frequency and intensity of aggressive display to a conspecific, though brain nucleus volumes were unrelated to behavior. Our findings fail to support our hypothesis and suggest instead that plasma testosterone level covaries with aggression level and in a limited capacity with brain nucleus volumes but that these are largely unrelated relationships.

Aggression↗
PubMed2006

Population divergence in plasticity of the AVT system and its association with aggressive behaviors in a Death Valley pupfish.

Behavioral differences can evolve rapidly in allopatry, but little is known about the neural bases of such changes. Allopatric populations of Amargosa pupfish (Cyprinodon nevadensis) vary in aggression and courtship behaviors in the wild. Two of these wild populations were recently found to differ in brain expression of arginine vasotocin (AVT)--a peptide hormone shown previously to modulate aggression in pupfish. These populations have been isolated for less than 4000 years, so it remained unclear whether the differences in behavior and neural AVT phenotype were evolved changes or plastic responses to ecologically dissimilar habitats. Here, I tested whether these population differences have a genetic basis by examining how aggressive behavior and neural AVT phenotype responded to ecologically relevant variation in salinity (0.4 ppt or 3 ppt) and temperature (stable or daily fluctuating). Pupfish from Big Spring were more aggressive than pupfish from the Amargosa River when bred and reared under common laboratory conditions. Morphometric analysis of preoptic AVT immunoreactivity showed that the populations differed in how the AVT system responded to salinity and temperature conditions, and revealed that this plasticity differed between parvocellular and magnocellular AVT neuron groups. Both populations also showed relationships between neural AVT phenotype and aggression in the rearing environment, although populations differed in how aggression related to variation in magnocellular AVT neuron size. Together, these results demonstrate that the pupfish populations have diverged in how physical and social conditions affect the AVT system, and provide evidence that the AVT system can evolve quickly to ecologically dissimilar environments.

Aggression↗
PubMed2002

Intermittent explosive disorder and other psychiatric comorbidity among court-referred and self-referred aggressive drivers.

We assessed possible Axis I and Axis II disorders in two groups of aggressive drivers (n=20, court-referred; n=10, self-referred) and 30 non-aggressive driver controls, using the SCID and SCID-II. Aggressive drivers were more likely than controls to be positive for any Axis I and Axis II disorders. They were also more likely to meet the criteria for Intermittent Explosive Disorder (IED), current or past alcohol or substance abuse or dependence and Antisocial PD and Borderline PD. The self-referred aggressive drivers were more likely than court-referred aggressive drivers to meet the criteria for a current or past Anxiety Disorder. Re-analysis of aggressive driver data on the basis of presence or absence of IED revealed differences only in Axis II disorders: those with IED were more likely to meet the criteria for any Axis II disorder and Antisocial PD.

Adult↗
PubMed2001

Aggressivity, suicide attempts, and depression: relationship to cerebrospinal fluid monoamine metabolite levels.

BACKGROUND: We have proposed a stress-diathesis model for suicidal behavior, in which major depression is a stressor and the diathesis is shared with aggression. Neurotransmitter correlates of the stress or diathesis have not been adequately evaluated by previous studies, because they did not simultaneously examine the relationship of multiple neurotransmitters to all three psychopathologies in the same population. In the present study we investigated the relationship of monoamine metabolites to aggressivity, suicidal behavior, and depression in patients with mood disorders. METHODS: Ninety-three drug-free subjects with a major depressive episode underwent lumbar puncture and psychiatric evaluation. Cerebrospinal fluid CSF levels of 5hydroxyindolacetic acid (5-HIAA), homovanillic acid (HVA) and methoxy-hydroxy-phenylglycol (MHPG) were assayed. The relationships between monoamine metabolites and clinical variables were statistically evaluated. RESULTS: Higher lifetime aggressivity correlated significantly with lower CSF 5-HIAA. Lower CSF 5-HIAA and greater suicidal intent were found in high-lethality suicide attempters compared with low-lethality suicide attempters. Low-lethality attempters did not differ biologically from nonattempters. No correlation between CSF HVA and any of the psychopathological variables was found. Only aggression showed a trend statistically in correlating positively with CSF MHPG levels. CONCLUSIONS: Lower CSF 5-HIAA concentration was independently associated with severity of lifetime aggressivity and a history of a higher lethality suicide attempt and may be part of the diathesis for these behaviors. The dopamine and norepinephrine systems do not appear to be as significantly involved in suicidal acts, aggression, or depression. The biological correlates of suicide intent warrant further study.

Adult↗
PubMed1997

Age-related changes in the association between serotonergic function and aggression in boys with ADHD.

The results of several studies have indicated an inverse relationship between central serotonergic (5-HT) mechanisms and aggression in animals and adults, but studies in children have yielded conflicting results. This study assessed 5-HT function, using a fenfluramine (FEN) challenge procedure, in an attempt to replicate a previously reported enhancement of the prolactin (PRL) response to FEN in aggressive relative to nonaggressive ADHD boys. The study failed to replicate the previous finding. Samples from both studies were then examined to reconcile the discrepant findings. The samples differed significantly in age. The entire group (n = 50) was then divided into older and younger subgroups and reanalyzed using a two-way (age-group x aggression) analysis of covariance (ANCOVA) controlling for plasma medication level. The ANCOVA generated a significant age-group x aggression interaction. Young aggressive boys had a significantly greater PRL response to FEN than young nonaggressive boys, but no such difference existed in the older age-group. These findings raise the possibility of different developmental trajectories in 5-HT function between aggressive and nonaggressive boys.

Aggression↗
PubMed1998

Cerebrospinal fluid monoamine metabolites and glucose metabolism in posttraumatic aggression.

BACKGROUND: This pilot study was conducted to determine if aggressive, post brain-injured patients have abnormal glucose metabolism or abnormal CSF monoamine metabolite concentrations as compared with non-aggressive, post brain-injured controls. METHODS: Subjects with a history of traumatic brain injury underwent a lumbar puncture and glucose tolerance test after a three-week medication wash-out period. Monoamine metabolite concentrations and glucose nadirs were compared between aggressive and control subjects. RESULTS: There were no statistical differences between the aggressive (n = 4) and control (n = 6) group with respect to age (28.5 +/- 15.7 versus 28.0 +/- 10.8), weight (72.5 kg +/- 14.1 versus 67.7 kg +/- 10.1) or number of months since brain injury (31.8 +/- 26.1 versus 33.3 +/- 23.3). There were no significant differences between the two groups in glucose nadirs following oral glucose challenge or in levels of CSF monoamine metabolite concentrations of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), or 3-methoxy-4-hydroxyphenylglycol (MHPG), although a trend toward significance was noted between the MHPG groups (higher MHPG within aggressive group). CONCLUSIONS: The preliminary data suggest that glucose metabolism and CSF monoamine metabolite concentrations do not differ significantly from aggressive subjects to controls in persons with brain injury. Follow-up prospective studies with larger sample sizes are needed to evaluate these preliminary findings.

Adult↗
PubMed1998

Adrenal androgens and aggression in conduct disorder prepubertal boys and normal controls.

BACKGROUND: The evidence for a role of androgens in human aggression is less convincing than in animals. We examined the relationship between androgens and aggression in prepubertal boys who were diagnosed as suffering from severe aggression and antisocial behavior. METHODS: Plasma levels of testosterone (T), androstenedione (A), and dehydroepiandrosterone sulphate (DHEAS) were measured in 15 boys with a conduct disorder (CD) and 25 normal control (NC) boys. Parents and teachers of the children rated the intensity of aggression and delinquency over the last 6 months. RESULTS: CD boys had significantly higher levels of DHEAS and marginally significantly higher levels of A; there were no differences in T. Moreover, DHEAS levels were significantly positively correlated with the intensity of aggression and delinquency as rated by both parents and teachers. CONCLUSIONS: The results suggest that adrenal androgen functioning plays an important role in the onset and maintenance, of aggression in young boys.

Adrenal Glands↗
PubMedDate not supplied

Symptoms of prototypic patients with passive-aggressive personality disorder: DSM-IIIR versus DSM-IV negativistic.

This study examined features of patients that clinicians identified as good examples of Passive-Aggressive Personality Disorder to identify core features of the disorder and to determine which set of criteria (DSM-III-R, two definitions in the DSM-IV Options Book, or DSM-IV Negativistic) best characterized the identified patients. A national sample of licensed psychologists (N = 68) identified a patient who (based on symptoms) was a good example of Passive-Aggressive Personality Disorder. They then rated the patient on a symptom checklist composed of the Passive-Aggressive and Negativistic criteria, as well as other personality-disorder symptoms that overlap with Passive-Aggressive. Clinicians identified patients they considered exemplars for Passive-Aggressive Personality Disorder, and there was moderate consensus about their characteristic symptoms. DSM-III-R symptoms received the highest ratings, and there was little overlap with other personality disorders. Principal-component factor analysis suggested that a general pattern of passive resistance, along with a behavioral manifestation of procrastination and a second group of symptoms suggesting interpersonal difficulties, were the features of these passive-aggressive patients. More male patients were identified as good examples of the disorder, and female patients presented a more heterogeneous diagnostic picture. Implications and directions for future research are discussed, including the need to integrate research findings from the differing perspectives on personality disorders.

Adult↗