Non-angry aggressive arousal and angriffsberietschaft: A narrative review of the phenomenology and physiology of proactive/offensive aggression motivation and escalation in people and other animals

Hypothalamic resting-state functional connectivity and self-evaluated aggression in young adults

INTRODUCTION

The hypothalamus plays a pivotal role in supporting motivated behaviors, including aggression. Previous work suggested differential roles of the medial (MH) and lateral hypothalamus (LH) in aggressive behaviors, but little is known about how their resting-state functional connectivity (rsFC) may relate to aggression in humans.

METHODS

We employed the data from the Human Connectome Project (HCP) and examined the rsFC's of LH and MH in 745 young adults (393 women). We also explored sex differences in the rsFC's. We processed the imaging data with published routines and evaluated the results of voxel-wise regression on the aggression score, as obtained from Achenbach Adult Self Report, with a corrected threshold.

RESULTS

The analyses revealed significant rsFC's between the LH and clusters in the middle temporal and occipital gyri across all subjects and in the thalamus for men, both in negative correlation with the aggression score. The slope test confirmed sex difference in the correlation between the LH-thalamus rsFC and aggression score. No significant rsFC was observed for the MH.

CONCLUSIONS

These findings suggest a role of the LH rsFC's and sex differences in the LH-thalamus rsFC in the manifestation of aggression in humans. The findings highlight the need for further research into sex-specific neural pathways in aggression and other related behavioral traits of importance to mental health.

What Dyadic Internet Street Fight Videos Can and Cannot Tell Us About the Ethological, Game Theoretic, and Sex-Differentiated Phenomenology of Human Physical Aggression

Street fight videos on the internet may provide information about little known aspects of human physical aggression, but their reliability is unclear. Analyses of 100 dyadic fight videos addressing ethological, game theoretic and sex-differentiated questions derived from research on other animals found that prefight verbalizations or gestural signals of nonaggressive or aggressive intent loosely predicted who would strike first and who would win. The head is the preferred strike target. Ordinal severity rankings of different strikes ranged from 1 for spitting to 5 for choking. Half the videos showed briefer, unilateral assaults beginning with one or more high severity strikes, little evidence of escalation and fewer bystander interventions. A quarter of these were sneak attacks. The other videos showed longer fights with reciprocal strikes, some evidence of strike severity escalation and more bystander intervention. Both types were equally injurious. Winner/loser outcomes were reliably identified by postfight behaviors and/or signs of injury. Winners had advantageous prefight resource holding potential (RHP: greater height and/or vigor) significantly more often than losers. Consistent with tendencies for fights to occur between animals of the same sex, there were more male/male and female/female fights and fewer male/female fights than expected from random pairings of men and women in the videos. Female/female fights involved proportionally more hair-pulling, extended bouts of rapidly repeated strikes and longest durations. Bystanders intervened in over half the videos, attempting to separate fighters or help losers more often than they attacked the loser. Carefully selected internet street fight videos can provide important information.

Deficits in emotional cognition among individuals with conduct disorder: theoretical perspectives

Conduct disorder refers to a persistent and repetitive pattern of problematic behavior, and is usually accompanied by deficits in cognitive processing of emotional stimuli. Behavioral and physiological correlates of these deficits have been the subject of sufficiently many investigations. Meanwhile, several theories concerning conduct disorder have been developed. However, the validity of these theories to explain the emotional processing deficits among conduct-disordered individuals has not been tested. Here we summarized four relevant theories, including "social-cognitive theory and social-information-processing theory", "violence inhibition model", "optimal stimulation/arousal theory and stimulation/sensation seeking theory", and "fearlessness theory", and discussed their validity in predicting the emotional processing deficits among conduct disordered individuals. Future directions on the theories and evidence were proposed.

Social play in African savannah elephants may inform selection against aggression

In social groups, competition for individual advantage is balanced with cooperation, for the collective benefit. Selection against aggression has favored cooperation and non-aggressive competitive strategies. Because social play is a behavioral system that fluctuates between cooperation and competition, selection against aggression might have especially influenced this behavior. African savannah elephants (Loxodonta africana) are a low aggressive species, therefore suitable to investigate this aspect. We collected all occurrences observational audio-video data on social play, aggression/threats, and affiliation on an African elephant colony housed in a 25-ha open space at Parque de la Naturaleza de Cabarceno (Cantabria, Spain) and composed of 4 family groups (3 immature males, 3 immature females, and 7 adult females) and 2 adult males. Anticipating the influence of reduced aggression, we found that social play decreased with age, persisting in adults, and that it was highest in males. Social play was associated with affiliation (informing cooperation). Indeed, individuals that were central in the social play network were also central in the affiliation network. For immature subjects, we found a correlation between social play and affiliation sociomatrices. However, such correlation was absent in adults and social play mostly occurred between families. Despite the limitations related to dealing with a small captive group, this study largely supports the idea that the features of social play in African savannah elephants may be related to low aggression. This investigation hints toward a non-purely cooperative use of play, possibly as a non-aggressive interaction that accommodates different levels of cooperation and competition.

Nuancing 'Emotional' Social Play: Does Play Behaviour Always Underlie a Positive Emotional State?

This review focuses on social play, a complex behaviour that is often difficult to categorize. Although play has been typically associated with positive emotional states, a thorough examination of the literature indicates that it may relate to different emotional systems, from attachment to conflict. Play oscillates between competition and cooperation, and includes a spectrum in between; thus, quantitatively identifying and demonstrating the emotional nature of play remains challenging. We considered examples from human and non-human animal studies and explored the emotional and neuro-hormonal systems involved in play. We assessed ethological data possibly indicating the emotional states underlying play, and we focused on the cooperative and competitive elements of play. We investigated the relationship between play and affiliative/aggressive behaviours, the communicative meaning of play signals (especially primate play faces), and the motor and possibly emotional contagion function of rapid motor mimicry during play. From all the literature on play, this review selects and combines studies in an innovative way to present the methods (e.g., play indices and social network analysis), tools (e.g., sequential analysis and facial coding software), and evidence indicative of the emotional states underlying play, which is much more complex than previously thought.

Oppositions, joints, and targets: the attractors that are the glue of social interactions

Social interactions are often analyzed by scoring segments of predefined behavior and then statistically assessing numerical and sequential patterns to identify the structure of the encounters. However, this approach can miss the dynamics of the animals' relationship over the course of the encounter, one that often involves invariant bonds, say a nose-to-nose orientation, with many different movements performed by both partners acting to counteract each other's attempts to break or maintain the relationship. Moreover, these invariant bonds can switch from one configuration to another during an interaction, leading from one stable configuration to another. It is this stepwise sequence of configurational stabilities that lead to functional outcomes, such as mating, aggression, or predation. By focusing on the sequence of invariant relational configurations, the deep structure of interactions can be discerned. This deep structure can then be used to differentiate between compensatory movements, no matter how seemingly stereotyped they may appear, from movement patterns which are restricted to a particular form when more than one option is available. A dynamic perspective requires suitable tools for analysis, and such tools are highlighted as needed in describing particular interactions.

Postweaning stress affects behavior, brain and gut microbiota of adolescent mice in a sex-dependent manner

Aggression is an instinctive behavior that has been reported to be influenced by early-life stress. However, the potential effects of acute stress during the postweaning period, a key stage for brain development, on defensive aggression and the associated mechanism remain poorly understood. In the present study, aggressive behaviors were evaluated in adolescent mice exposed to postweaning stress. Serum corticosterone and testosterone levels, neural dendritic spine density, and gut microbiota composition were determined to identify the underlying mechanism. Behavioral analysis showed that postweaning stress reduced locomotor activity in mice and decreased defensive aggression in male mice. ELISA results showed that postweaning stress reduced serum testosterone levels in female mice. Golgi staining analysis demonstrated that postweaning stress decreased neural dendritic spine density in the medial prefrontal cortex of male mice. 16S rRNA sequencing results indicated that postweaning stress altered the composition of the gut microbiota in male mice. Combined, these results suggested that postweaning stress alters defensive aggression in male mice, which may be due to changes in neuronal structure as well as gut microbiota composition. Our findings highlight the long-lasting and sex-dependent effects of early-life experience on behaviors.

Aggression modulator: Understanding the multifaceted role of the dorsal raphe nucleus

Aggressive behavior is instinctively driven behavior that helps animals to survive and reproduce and is closely related to multiple behavioral and physiological processes. The dorsal raphe nucleus (DRN) is an evolutionarily conserved midbrain structure that regulates aggressive behavior by integrating diverse brain inputs. The DRN consists predominantly of serotonergic (5-HT:5-hydroxytryptamine) neurons and decreased 5-HT activity was classically thought to increase aggression. However, recent studies challenge this 5-HT deficiency model, revealing a more complex role for the DRN 5-HT system in aggression. Furthermore, emerging evidence has shown that non-5-HT populations in the DRN and specific neural circuits contribute to the escalation of aggressive behavior. This review argues that the DRN serves as a multifaceted modulator of aggression, acting not only via 5-HT but also via other neurotransmitters and neural pathways, as well as different subsets of 5-HT neurons. In addition, we discuss the contribution of DRN neurons in the behavioral and physiological aspects implicated in aggressive behavior, such as arousal, reward, and impulsivity, to further our understanding of DRN-mediated aggression modulation.

How it ends: A review of behavioral and psychological phenomena, physiological processes and neural circuits in the termination of aggression in other animals and anger in people

More is known about aggression initiation and persistence in other animals, and anger in people, than about their cessation. This review summarizes knowledge of relevant factors in aggression, mostly in vertebrates, and anger termination in people. The latency, probability and intensity of offensive aggression in mice is controlled by activity in a neuronal subpopulation in ventromedial hypothalamus [VMH]. This activity instantiates an aggressive state termed angriffsbereitschaft ["attack-readiness"]. Fighting in many species is broken into bouts with interbout breaks due to fatigue and/or signals from dorsal raphe to VMH. Eventually, losers decide durations and outcomes of fighting by transitioning to submission or flight. Factors reducing angriffsbereitschaft and triggering these defeat behaviors could include metabolic costs, e.g., lactate accumulation and glucose depletion detected by the hypothalamus, central fatigue perhaps sensed by the Salience Network [insula and anterior cingulate gyrus] and pain of injuries, the latter insufficiently blunted by opioid and non-opioid stress analgesia and transduced by anterior VMH neurons. Winners' angriffsbereitschaft continue for awhile, as indicated by post-victory attacks and, perhaps, triumph displays of some species, including humans. In longer term situations, sensory and/or response habituation of aggression may explain the "Dear enemy" tolerance of competitive neighbors. Prolonged satiation of predatory behavior could involve habenula-regulated reduction of dopaminergic reward in nucleus accumbens. Termination of human anger involves at least three processes, metaphorically termed decay, quenching and catharsis. Hypothesized neural mechanisms include anger diminution by negative feedback from accumbens to anterior cingulate and/or activity in the Salience Network that controls anger's "accumulation/offset" phase.