Neurobiology of violence

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Neurobiology of violence

• Jose Mejia M.D. Ph. D

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Aggression Classification

• Intraspecies/interspecies
• Offensive and predatory/defensive
• Cats
• Defensive rage
• Silent predatory
• Rats Offensive paradigms
• Territorial (resident intruder paradigm)
• Colony aggression
• Maternal aggression
• Play fighting
• Electrical hypothalamic stimulation

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Aggression Classification

• Rats predatory aggression
• Mouse killing
• Olfactory bulbectomy increases killing, method
  is different, depression model?
• Mice tend to be gregarious
• Isolation induces aggressive behaviours
• Hamsters
• Scent marking
• Resident intruder in females
• Attacks do not occur if intruder is sedated or
  anaesthetized

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Aggression Classification

• Nonhuman primates
• Rhesus and vervet
• Dependent on hierarchies
• Monkeys have to move to other groups to reproduce
  and avoid inbreeding
• Half of them perish
• Competitive aggression to procure food and
  resources. No physical damage inflicted
• Escalated aggression impulsive behaviour of an
  intruder in a clearly disadvantageous situation
• Aggression during mating season Selective
  against weaker peers, not severe

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Aggression Classification

• Human
• Competitive Sports
• Premeditated Army and crime
• Impulsive Intoxicants

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Aggression Anatomy

• Cats
• Lateral hypothalamus gt predation
• Medial hypothalamus and periaqueductal grey
  matter gt defensive rage
• Medial, anterior and basomedial amygdalagt
  facilitation
• Central and lateral amygdalagt inhibits defensive
  rage
• Hippocampus and septum modulate aggression
• Prefrontal cortex inhibitory

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Aggression Anatomy

• Rats
• Increase
• Anterior hypothalamus (def)
• Posterior hypothalamus (off)
• Caudal periaqueductal grey m (maternal)
• Nucleus accumbens Increased DA release in
  anticipation and during aggressive encounters
• Hamsters
• Increased C-Fos expression in corticomedial
  amygdala of R-I females (attack priming)

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Aggression Anatomy

• Monkeys
• Neurons in amygdala respond vigorously to facial
  expressions
• Aggressive monkeys show decreased sensitivity in
  GABA rich areas orbitofrontal cortex, head of
  caudate, dorsomedial thalami
• In humans these centers are involved in
  monitoring internal emotions and interpreting
  emotional expressions

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Aggression Anatomy

• Humans
• Phineas Cage frontal lobectomy and impulsive
  aggression and antisocial behaviours
• Tumors in temporal lobes medial portion, anterior
  hypothalamus
• Head injury (Miller)
• Episodic dyscontrol (no provocation)
• Increased aggression, minor stimuli, due to
  frontal lobe damage
• Exacerbation of antisocial behaviours

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Aggression Imaging studies

• Violent offenders have frontal pathology
• Sexual offenders have temporal pathology

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Aggression the pathway

• Orbitofrontal cortex head of caudate
  dorsomedial thalamaus (assess situation)
  septohippocampal system ? amygdala (assess
  response and regulate it) ? shell n.accumbens
  lateral and medial hypothalamus oral aggression,
  eye movements and autonomic response

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Aggression the pathway
Septohippocampal system
Shell n. accumbens Stressors and substances
Frontal cortex
Orbitofrontal cortex
Amygdala
Periaqueductal area Defensive aggression
Head n. caudate
Assessment situation
Dorsomedial thalamus
Lateral and medial hypothalamus Oral aggression,
eye movements and autonomic responses
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AggressionNeurotransmitters

• 5HT increases decrease aggressive behaviours and
  vice versa
• Violence and low 5HIAA
• Violence and reduction of dietary tryptophan
• Depletion with p-chlorophenialalanine and
  aggression
• 5HT and its agonists reduce aggressive behaviours
• Paradoxical reactions (in mice and men SSRIs)
• Low CSF 5HIAA related to higher status amongst
  monkeys and less fighting
• Soubrie suggested that 5HT does not induce
  aggression but permits it to happen due to
  increase in impulsivity

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AggressionNeurotransmitters

• 5HIAA decreased in brains of suicide victims
  (Asberg, 1976)
• 5HT transporter decreased in prefrontal cortex of
  suicide victims (Mann, 1997)
• Lower 5HIAA predicts higher risk of suicide and
  more lethal methods (Mann, 1997)
• Lower 5HIAA amongst higher scores in the
  Brown-Goodwin aggression scales (Brown 1972, 79)
  and psychopathic deviant scale of the MMPI
• Borderline patients who attempted suicide showed
  low 5HIAA (Gardner, 1990)
• Lower 5HT release and higher scores in BD
  hostility inventory (Moss, 1990 and Coccaro,
  1996)

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AggressionNeurotransmitters

• Low CSF 5HIAA amongst impulsive violent offenders
  but lowest amongst suicidal violent offenders
  (Linnoila, 1983)
• Low CSF 5HIAA amongst murderers of their child or
  spouse
• Alcohol induced murder similar in 5HIAA to that
  of impulsive murderers (Linnoila and Virkkunen,
  1994)
• Low 5HIAA and MHPG in CSF amongst impulsive fire
  setters (Virkkunen, 1987)
• Recidivistic killers had lower 5HIAA and glucose
  nadir in a glucose tolerance curves with a
  predictive value of 85
• Suicide attempters had also low MHPG (Virkkunen,
  1989 and 1996)

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Aggression hormones

• Aggressive behaviours mainly present in males and
  not females
• Testosterone
• Measurements are not reliable particularly the
  one in blood
• In monkeys High testosterone high status but
  not high aggression
• High testosterone and high 5HIAA in CSF high
  aggression
• High testosterone amongst violent criminals
  translates into suspiciousness, physical violence
  and hostility

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Aggression hormones

• Antisocial alcoholic violent offenders have lower
  urinary cortisol excretion (Virkkunen, 1984) and
  corticotropin concentrations in CSF
• Inverse correlation between plasma cortisol and
  impulsive behaviours (King, 1990)

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Aggression genetics

• Studies at the University of Connecticut had
  shown that length of Y chromosome is related to
  the presence of aggression in inbred mice
  associated with low 5HT turnover in aggression
  controlling centers
• KO mice 5HT1b, MAOA, pre-proencephalin, neuronal
  NO2 synthase

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Aggression genetics

• Adult antisocial aggressive behaviours show
  moderate to high heritability (Carey 1996)
• Adult AS behaviour is more genetic than
  adolescent AS behaviour (Lyons, 1995)
• Offspring of AS parents were at higher risk of
  aggressive behaviours and CD when raised by
  dysfunctional families, but not for ASPD
  (Cadoret, 1995)
• Brunner Syndrome