Editing Aggression (section)

===Brain pathways===
Many researchers focus on the brain to explain aggression. Numerous circuits within both neocortical and subcortical structures play a central role in controlling aggressive behavior, depending on the species, and the exact role of pathways may vary depending on the type of trigger or intention.<ref name=":6" /><ref name=":4" />

In mammals, the [[hypothalamus]] and [[periaqueductal gray]] of the [[midbrain]] are critical areas, as shown in studies on cats, rats, and monkeys. These brain areas control the expression of both behavioral and [[autonomic nervous system|autonomic]] components of aggression in these species, including vocalization. Electrical stimulation of the hypothalamus causes aggressive behavior<ref>{{cite journal |doi=10.1016/0006-8993(83)90764-3 |pmid=6681724 |title=Discriminant analysis of the localization of aggression-inducing electrode placements in the hypothalamus of male rats |journal=Brain Research |volume=260 |issue=1 |pages=61–79 |year=1983 |last1=Kruk |first1=Menno R. |last2=Van Der Poel |first2=A.M. |last3=Meelis |first3=W. |last4=Hermans |first4=J. |last5=Mostert |first5=P.G. |last6=Mos |first6=J. |last7=Lohman |first7=A.H.M. |s2cid=3231548 }}</ref> and the hypothalamus has receptors that help determine aggression levels based on their interactions with serotonin and vasopressin.<ref>{{cite journal |pmid=9151749 |pmc=6573530 |year=1997 |last1=Ferris |first1=C. F. |title=Vasopressin/serotonin interactions in the anterior hypothalamus control aggressive behavior in golden hamsters |journal=The Journal of Neuroscience |volume=17 |issue=11 |pages=4331–40 |last2=Melloni |first2=R. H. Jr. |last3=Koppel |first3=G |last4=Perry |first4=K. W. |last5=Fuller |first5=R. W. |last6=Delville |first6=Y |doi=10.1523/JNEUROSCI.17-11-04331.1997 }}</ref> In rodents, activation of [[estrogen receptor]]-expressing neurons in the ventrolateral portion of the [[ventromedial hypothalamus]] (VMHvl) was found to be sufficient to initiate aggression in both males and females.<ref>{{cite journal |last1=Lee |first1=H |title=Scalable control of mounting and attack by Esr1+ neurons in the ventromedial hypothalamus |journal=Nature |date=2014 |volume=509 |issue=7502 |pages=627–32 |doi=10.1038/nature13169 |pmid=24739975 |pmc=4098836 |bibcode=2014Natur.509..627L }}</ref><ref>{{cite journal |last1=Hashikawa |first1=K |title=Esr1+ cells in the ventromedial hypothalamus control female aggression |journal=Nat. Neurosci. |date=2017 |volume=11 |issue=20 |pages=1580–1590 |doi=10.1038/nn.4644 |pmid=28920934 |pmc=5953764 }}</ref> Midbrain areas involved in aggression have direct connections with both the [[brainstem]] nuclei controlling these functions, and with structures such as the [[amygdala]] and [[prefrontal cortex]].

Stimulation of the amygdala results in augmented aggressive behavior in hamsters,<ref>{{cite journal |doi=10.1037/0735-7044.110.2.401 |pmid=8731066 |title=Brief, high-frequency stimulation of the corticomedial amygdala induces a delayed and prolonged increase of aggressiveness in male Syrian golden hamsters |journal=Behavioral Neuroscience |volume=110 |issue=2 |pages=401–12 |year=1996 |last1=Potegal |first1=M. |last2=Hebert |first2=M. |last3=Decoster |first3=M. |last4=Meyerhoff |first4=J. L. }}</ref><ref name="Potegal, M 1996. pp. 869-880"/> while [[lesions]] of an [[homology (biology)|evolutionarily homologous]] area in the lizard greatly reduce competitive drive and aggression (Bauman et al. 2006).<ref>{{cite journal |doi=10.1016/0031-9384(84)90088-X |pmid=6538977 |title=Role of the amygdala in the reproductive and aggressive behavior of the lizard, Anolis carolinensis |journal=Physiology & Behavior |volume=32 |issue=1 |pages=147–51 |year=1984 |last1=Greenberg |first1=Neil |last2=Scott |first2=Michelle |last3=Crews |first3=David |s2cid=9987359 }}</ref> In [[rhesus monkeys]], neonatal lesions in the amygdala or hippocampus results in reduced expression of social dominance, related to the regulation of aggression and fear.<ref>{{cite journal |doi=10.1037/0735-7044.120.4.749 |pmid=16893283 |title=The expression of social dominance following neonatal lesions of the amygdala or hippocampus in rhesus monkeys (Macaca mulatta) |journal=Behavioral Neuroscience |volume=120 |issue=4 |pages=749–60 |year=2006 |last1=Bauman |first1=M. D. |last2=Toscano |first2=J. E. |last3=Mason |first3=W. A. |last4=Lavenex |first4=P. |last5=Amaral |first5=D. G. |url=http://doc.rero.ch/record/6372/files/lavenex_esd.pdf }}</ref> Several experiments in attack-primed Syrian golden hamsters, for example, support the claim of circuitry within the amygdala being involved in control of aggression.<ref name="Potegal, M 1996. pp. 869-880">{{cite journal |doi=10.1016/0306-4522(96)00236-9 |pmid=8951880 |title=Attack priming in female Syrian golden hamsters is associated with a c-fos-coupled process within the corticomedial amygdala |journal=Neuroscience |volume=75 |issue=3 |pages=869–80 |year=1996 |last1=Potegal |first1=M. |last2=Ferris |first2=C.F. |last3=Hebert |first3=M. |last4=Meyerhoff |first4=J. |last5=Skaredoff |first5=L. |s2cid=24136851 |url=https://zenodo.org/record/1258481 }}</ref> The role of the amygdala is less clear in primates and appears to depend more on situational context, with lesions leading to increases in either social affiliatory or aggressive responses. [[Amygdalotomy]], which involves removing or destroying parts of the amygdala, has been performed on people to reduce their violent behaviour.

The broad area of the cortex known as the [[prefrontal cortex]] (PFC) is crucial for [[self-control]] and inhibition of impulses, including inhibition of aggression and emotions. Reduced activity of the prefrontal cortex, in particular its medial and [[Orbitofrontal cortex|orbitofrontal]] portions, has been associated with violent/antisocial aggression.<ref>Paus, T. 'Mapping Brain Development' in [https://books.google.com/books/about/Developmental_origins_of_aggression.html?id=XmSfJEl2v4sC Developmental Origins of Aggression], 2005, The Guilford Press.</ref> In addition, reduced [[response inhibition]] has been found in violent offenders, compared to non-violent offenders.<ref name=":6">{{Cite journal|last1=Meijers|first1=J.|last2=Harte|first2=J. M.|last3=Meynen|first3=G.|last4=Cuijpers|first4=P.|date=1 February 2017|title=Differences in executive functioning between violent and non-violent offenders|url=https://www.cambridge.org/core/journals/psychological-medicine/article/div-classtitledifferences-in-executive-functioning-between-violent-and-non-violent-offendersdiv/51D2EDD628447218922BA833A6F59D85|journal=Psychological Medicine|volume=47|issue=10|pages=1784–1793|doi=10.1017/S0033291717000241|pmid=28173890|s2cid=4481557|issn=0033-2917|hdl=1871.1/371bdff2-a6df-45ee-a1fd-90995ea811d7|hdl-access=free}}</ref>

The role of the chemicals in the brain, particularly [[neurotransmitters]], in aggression has also been examined. This varies depending on the pathway, the context and other factors such as gender. A deficit in [[serotonin]] has been theorized to have a primary role in causing impulsivity and aggression. At least one epigenetic study supports this supposition.<ref name=pmid27720744>{{cite journal |doi=10.1016/j.bbr.2016.10.009 |pmid=27720744 |title=The association of serotonin receptor 3A methylation with maternal violence exposure, neural activity, and child aggression |journal=Behavioural Brain Research |volume=325 |issue=Pt B |pages=268–277 |year=2016 |last1=Schechter |first1=Daniel S. |last2=Moser |first2=Dominik A. |last3=Pointet |first3=Virginie C. |last4=Aue |first4=Tatjana |last5=Stenz |first5=Ludwig |last6=Paoloni-Giacobino |first6=Ariane |last7=Adouan |first7=Wafae |last8=Manini |first8=Aurélia |last9=Suardi |first9=Francesca |last10=Vital |first10=Marylene |last11=Sancho Rossignol |first11=Ana |last12=Cordero |first12=Maria I. |last13=Rothenberg |first13=Molly |last14=Ansermet |first14=François |last15=Rusconi Serpa |first15=Sandra |last16=Dayer |first16=Alexandre G. |doi-access=free }}</ref> Nevertheless, low levels of serotonin transmission may explain a vulnerability to impulsiveness, potential aggression, and may have an effect through interactions with other neurochemical systems. These include [[dopamine]] systems which are generally associated with attention and motivation toward rewards, and operate at various levels. [[Norepinephrine]], also known as noradrenaline, may influence aggression responses both directly and indirectly through the hormonal system, the [[sympathetic nervous system]] or the [[central nervous system]] (including the brain). It appears to have different effects depending on the type of triggering stimulus, for example social isolation/rank versus shock/chemical agitation which appears not to have a linear relationship with aggression. Similarly, [[GABA]], although associated with inhibitory functions at many CNS synapses, sometimes shows a positive correlation with aggression, including when potentiated by alcohol.<ref>{{cite journal |doi=10.1016/j.bbr.2008.01.003 |pmid=18281105 |title=Development of violence in mice through repeated victory along with changes in prefrontal cortex neurochemistry |journal=Behavioural Brain Research |volume=189 |issue=2 |pages=263–72 |year=2008 |last1=Caramaschi |first1=Doretta |last2=De Boer |first2=Sietse F. |last3=De Vries |first3=Han |last4=Koolhaas |first4=Jaap M. |hdl=11370/f683911d-3c8b-4ba6-a6bb-12cbaf11dead |s2cid=14888253 |url=https://pure.rug.nl/ws/files/6717763/2008BehavBrainResCaramaschi.pdf |hdl-access=free }}</ref><ref>Pihl, RO & Benkelfat, C. 'Neuromodulators in the Development and Expression of Inhibition and Aggression' in [https://books.google.com/books/about Developmental_origins_of_aggression.html?id=XmSfJEl2v4sC Developmental Origins of Aggression], 2005, The Guilford Press.</ref>

The hormonal [[neuropeptides]] [[vasopressin]] and [[oxytocin]] play a key role in complex social behaviours in many mammals such as regulating attachment, social recognition, and aggression. Vasopressin has been implicated in male-typical social behaviors which includes aggression. Oxytocin may have a particular role in regulating female bonds with offspring and mates, including the use of protective aggression. Initial studies in humans suggest some similar effects.<ref>{{cite book |doi=10.1016/S0079-6123(08)00428-7 |pmid=18655894 |chapter=Neuropeptides and social behaviour: Effects of oxytocin and vasopressin in humans |title=Advances in Vasopressin and Oxytocin – from Genes to Behaviour to Disease |volume=170 |pages=337–50 |series=Progress in Brain Research |year=2008 |last1=Heinrichs |first1=M |last2=Domes |first2=G |isbn=978-0-444-53201-5 }}</ref><ref>{{cite journal |doi=10.1016/j.biopsycho.2007.09.001 |pmid=17931766 |title=Attachment, aggression and affiliation: The role of oxytocin in female social behavior |journal=Biological Psychology |volume=77 |issue=1 |pages=1–10 |year=2008 |last1=Campbell |first1=Anne |s2cid=33228118 |url=http://dro.dur.ac.uk/10217/1/10217.pdf?DDD27+dul4eg }}</ref>

In human, [[aggressive behavior]] has been associated with abnormalities in three principal regulatory systems in the body [[serotonin|serotonin systems]], [[catecholamine|catecholamine systems]], and the [[hypothalamic–pituitary–adrenal axis]]. Abnormalities in these systems also are known to be induced by [[Stress (biology)|stress]], either severe, acute stress or chronic low-grade stress<ref>{{cite journal |doi=10.1300/J076v36n01_04 |title=Effects of the ''Transcendental Meditation'' Program on Neuroendocrine Abnormalities Associated with Aggression and Crime |journal=Journal of Offender Rehabilitation |volume=36 |issue=1–4 |pages=67–87 |year=2003 |last1=Walton |first1=Kenneth G. |last2=Levitsky |first2=Debra K. |s2cid=144374302 }}</ref>