neural mechanism of aggression Flashcards
What is the difference in hot- and cold-blooded aggression?
Reactive aggression (hot blooded): angry impulsive behavior coupled with physiological arousal
Case: Tony Martin (1999)
Proactive aggression (cold blooded): pre-meditated way of getting what you want e.g. rape, murder
Case: The Moors Murderers
What are the brain regions associated with the limbic system?
- Amygdala
- Hypothalamus
- Hippocampus
What is a key role of the limbic circuit?
Center of emotion and learning
What is the limbic circuit also known as?
Papez circuit (1935)
What is the link between Kluver & Bucy’s (1937) research in animals and Kluver-Bucy syndrome
Kluver and Bucy (1937) research discovered that the destruction of the amygdala in a dominant monkey caused it to loose its dominance in the social group. The link between this and Kluver Bucy syndrome is that Kluver- Bucy syndrome is a neurotic disorder as a result of lesions affecting the bilateral temporal lobes especially in the hippocampus and amygdala resulting in plasticity which was displayed when the monkey lost its dominance as a result of the lesions in their amygdala
What did Mark & Ervin (1970) report in a patient receiving stimulation to her amgydala?
Mark and Ervin (1970 reported that a women who received painless stimulation to her amygdala became enraged and began smashing her guitar against a wall
Explain the research by Gospic et al. (2011), and how it sheds light on the role of the limbic system in aggression.
Gospic (2011) asked ppts to play ‘The Ultimatum game’. In this Subject A is termed the proposer and subject B is the Responder. Subject B was subjected to mild provocation. The researchers used fMRI to monitor the brain activity whilst playing. In addition they found that when ppts took Benzodiazaphines which calm anxiety the effect was that it halved the number of rejections and decreased amygdala activity. In conclusion Gospic’s research suggests an association between reactive aggression and the amygdala.
Explain the relationship between serotonin and aggression.
Serotonin has widespread inhibitory effects on the brain which slow down neural activity. Aggression in humans is associated with low levels of serotonin as normal levels in the orbito-frontal cortex reduce the firing of neurons and allow for a greater degree of behavioral self control. Decreased levels of Serotonin disturb this mechanism reducing self- control and increasing impulsive behavior such as aggression
evidence for the role of serotonin in violent behaviour: animal studies
By pharmacologically blocking or genetically modifying 5-HT2A receptors. Mice with a deletion of the gene responsible for 5-HT2A expression exhibit less aggressive behaviour compared to typical mice. Stimulating 5-HT2A can lead to aggression, especially when the animal perceives threat or competition
evidence for the role of serotonin in violent behaviour: anti-psychotics
Drugs for schizophrenia block the D2 receptor but some have impacts on other receptors. Risperidone and Olanzapine block the 5-HT2A receptor and have been shown to reduce aggression in patients with schizophrenia or dementia
evidence for the role of serotonin in violent behaviour:
evidence for the role of serotonin in violent behaviour: serotonergic metabolites
Virkkunen et al (1994) compared levels of a serotonin breakdown product (5-HIAA) in the cerebrospinal fluid of both violent impulsive and violent non-impulsive offenders. The levels were significantly lower in the impulsive offenders. This is because the reduction of the 5-H1AA means there is decreased serotonin activity in the brain which has an effect on controlling impulsive (reactive) aggressive behavior.
evidence for the role of serotonin in violent behaviour: serotonin- depletion studies
Passamonti et al. (2012) used acute tryptophan depletion (ATD) as a way to temporarily reduce serotonin (tryptophan is the precursor for serotonin). The results showed that ATD reduced connectivity between the Prefrontal cortex and amygdala when participants viewed angry faces suggesting that low serotonin might impair the Prefrontal cortex’s ability to regulate the amygdala’s response to aggression-related cues
evidence for serotonin being involved in violent behaviour: post-mortem studies
Rosell and Siever (2015) reviewed post-mortem studies indicating that individuals with histories of impulsive aggression or violent behavior often show an upregulation of 5-HT2A receptors (perhaps compensating for low serotonin) in the PFC, particularly in the orbitofrontal cortex.
