The Role of the Lateral Hypothalamus in Violent Intraspecific Aggression-The Glucocorticoid Deficit Hypothesis

Hypothalamic connectivities and self-evaluated aggression in young adults

Introduction

The hypothalamus plays a pivotal role in supporting motivated behavior, including aggression. Previous work suggested differential roles of the medial hypothalamus (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 aggression score, as obtained from Achenbach Adult Self Report, with a corrected threshold.

Results

The analysis revealed significant rsFC 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 aggression score. Slope test confirmed sex differences in the correlation between LH-thalamus rsFC and aggression score. No significant rsFC was observed for MH.

Conclusions

These findings suggest a role of LH rsFCs and sex differences in 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.

Tickle fetishism: pleasure beyond playfulness

Tickling is commonly perceived as juvenile play associated with laughter. However, its potential connection to adult sexual behavior has largely remained unexplored. Our online survey, primarily distributed among individuals interested in tickle fetishism, explored tickling and its association with sexual behavior. Ticklishness types, tools, preferred body parts, and partner preferences, were examined. Results revealed diverse patterns of ticklishness changes over time and distinct body-part preferences for different types of tickling. Childhood experiences and exposure to tickling content in television were found to shape individuals' affinity for tickle fetishism. A quarter of respondents reported experiencing orgasms exclusively from tickling, while around 88% expressed sexual satisfaction through tickling alone, indicating its sufficiency as a sexual stimulus among fetishists. Tickling desire decreased after orgasm, indicating an association between tickling and sexual activity. Moreover, ticklishness degree predicted preferences for being tickled rather than tickling others. Exploratory factor analysis identified three factors underlying tickling and sexual experiences: enjoyment and frequency of tickling during sexual activity; preference for intense sexual experiences; age of becoming sexually active. In conclusion, this study provides unique insights into tickling and its connections to sexual context, enhancing our understanding of diverse human sexual behavior and tickle fetishism as a distinct preference.

Immunoglobulin G is a natural oxytocin carrier which modulates oxytocin receptor signaling: relevance to aggressive behavior in humans

Oxytocin is a neuropeptide produced mainly in the hypothalamus and secreted in the CNS and blood. In the brain, it plays a major role in promoting social interactions. Here we show that in human plasma about 60% of oxytocin is naturally bound to IgG which modulates oxytocin receptor signaling. Further, we found that IgG of violent aggressive inmates were characterized by lower affinity for oxytocin, causing decreased oxytocin carrier capacity and reduced receptor activation as compared to men from the general population. Moreover, peripheral administration of oxytocin together with human oxytocin-reactive IgG to resident mice in a resident-intruder test, reduced c-fos activation in several brain regions involved in the regulation of aggressive/defensive behavior correlating with the attack number and duration. We conclude that IgG is a natural oxytocin carrier protein modulating oxytocin receptor signaling which can be relevant to the biological mechanisms of aggressive behavior.

Hypothalamic volume in pedophilia with or without child sexual offense

The hypothalamus regulates sexual behavior and is simultaneously associated with aggression and violence. Consequently, this brain region is relevant in research of pedophilia and child sexual offenses (CSO). The distinction between these two phenomena is of great importance and was the object of consideration of this study. We analyzed exclusively men, including 73 pedophilic offenders who committed CSO, an equal number of people with pedophilia but without such offenses, and 133 non-pedophilic, non-offending subjects who formed the control group. All data were collected in a multicenter in vivo study and analyzed using a semi-automated segmentation algorithm for 3-Tesla magnetic resonance images. Men with pedophilia who committed CSO on average had a 47 mm3 smaller hypothalamus per side than people without committed CSO. This effect was driven by both the group of non-offending people with pedophilia and the control group. By contrast, the exploratory comparison of pedophilic persons without CSO with the control group showed no significant difference. The present study demonstrates a deviant hypothalamic structure as a neurobiological correlate of CSO in pedophiles, but not in people with pedophilia who have not committed CSO. Thus, it strengthens the argument to distinguish between sexual offending and paraphilic sexual preferences.

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

Human aggression typologies largely correspond with those for other animals. While there may be no non-human equivalent of angry reactive aggression, we propose that human proactive aggression is similar to offense in other animals' dominance contests for territory or social status. Like predation/hunting, but unlike defense, offense and proactive aggression are positively reinforcing, involving dopamine release in accumbens. The drive these motivational states provide must suffice to overcome fear associated with initiating risky fights. We term the neural activity motivating proactive aggression "non-angry aggressive arousal", but use "angriffsberietschaft" for offense motivation in other animals to acknowledge possible differences. Temporal variation in angriffsberietschaft partitions fights into bouts; engendering reduced anti-predator vigilance, redirected aggression and motivational over-ride. Increased aggressive arousal drives threat-to-attack transitions, as in verbal-to-physical escalation and beyond that, into hyper-aggression. Proactive aggression and offense involve related neural activity states. Cingulate, insular and prefrontal cortices energize/modulate aggression through a subcortical core containing subnuclei for each aggression type. These proposals will deepen understanding of aggression across taxa, guiding prevention/intervention for human violence.

Aggression, Aggression-Related Psychopathologies and Their Models

Neural mechanisms of aggression and violence are often studied in the laboratory by means of animal models. A multitude of such models were developed over the last decades, which, however, were rarely if ever compared systematically from a psychopathological perspective. By overviewing the main models, I show here that the classical ones exploited the natural tendency of animals to defend their territory, to fight for social rank, to defend themselves from imminent dangers and to defend their pups. All these forms of aggression are functional and adaptive; consequently, not necessarily appropriate for modeling non-natural states, e.g., aggression-related psychopathologies. A number of more psychopathology-oriented models were also developed over the last two decades, which were based on the etiological factors of aggression-related mental disorders. When animals were exposed to such factors, their aggressiveness suffered durable changes, which were deviant in the meaning that they broke the evolutionarily conserved rules that minimize the dangers associated with aggression. Changes in aggression were associated with a series of dysfunctions that affected other domains of functioning, like with aggression-related disorders where aggression is just one of the symptoms. The comparative overview of such models suggests that while the approach still suffers from a series of deficits, they hold the important potential of extending our knowledge on aggression control over the pathological domain of this behavior.

Neurobiology of Female Homicide Perpetrators

Neurobiology of female homicide perpetrators is not well understood. Data from private interviews and examinations of females were re-analyzed comparing those who committed homicide (n = 9); other violent crimes, no known homicide (n = 51); nonviolent crimes, no known violent convictions (n = 49); and noncriminals (n = 12). Homicide perpetrators suffered the most childhood sexual abuse (CSA); most recent abuse; had the most neurological histories, mainly traumatic brain injuries (TBIs); most health care access for abuse-related injuries; lowest AM and PM salivary cortisol; and greatest proportion who committed crime under the influence of alcohol. Only CSA, years since last abuse, TBI, neurological histories, and health care access for abuse-related injuries were significant. Those who committed homicide under the influence of alcohol suffered the most recent abuse and had the lowest AM cortisol and flattest diurnal cortisol slope (DCS) compared with others; though the n precludes determining significance. Amount of time since last abuse, AM cortisol and DCS progressively decreased as crime severity increased; other variables progressively increased as crime severity increased. These preliminary findings suggest that low AM cortisol, flat DCS, greater CSA frequency and severity, recent abuse, TBIs, and health care access for abuse-related injuries could be risk factors for females committing homicide. Further study is needed due to the small n of homicide perpetrators. Abuse victims may be at greater risk for alcohol use and cortisol dysregulation associated with perpetrating violence, especially homicide. Frontal lobe damage from TBIs may decrease ability to control behaviors associated with emotions from the limbic system. Health care providers released these women when their abuse-related injuries were not life-threatening; yet, they were life-threatening for victims of their subsequent homicides. Females accessing health care for abuse-related injuries present a critical opportunity for violent crime prevention interventions.