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Transcript of Neurotransmitters
Evidence! Evaluation! Two neurotransmitters are believed to be particularly important in the control of aggressive behavior. Aggression in both animals and humans has been associated with:
-low levels of serotonin
-high levels of dopamine Normal levels of Serotonin exert a calming, inhibitory effect on neuronal firing in the brain (Cases 1995) However low levels of serotonin in the prefrontal cortex removes the inhibitory effect. Serotonin reduces aggression by inhibiting responses to emotional stimuli that might otherwise lead to an aggressive response. High levels of dopamine are associated with aggression Serotonin - Mann et al (1990) - administered a drug dexfenfluramine which depletes serotonin levels in the brain to 35 healthy individuals. Questionnaires were used to assess hostility and aggression levels, and found that in males hostility and aggression levels increased after treatment with the drug. Dopamine antagonists have been used successfully to reduce aggression in violent delinquents Serotonin - Ferrari et al ( 2003)- allowed a rat to fight every day for ten days at the same time each day. On the 11th day the animal was not allowed to fight, but their levels of serotonin decreased dopamine is produced in response to rewarding stimuli, recent research has shown that dopamine plays a role in positively reinforcing aggressive behaviour questionnaires = BAD! Animals = BAD! it is thought that individuals seek out aggressive situations because of this rewarding sensation Studies with mice (e.g Couppis et al) demonstrate the main issue: effectively turning off dopamine in an animal’s brain also makes it difficult for the animal to move (dopamine helps coordinate movement). Reductionist– studies conducted on animals cannot be applied to humans because humans have a far more complex anatomy, and have a social basis that is more complex than that of vervet monkeys. The biological explanation alone is not enough to explain aggression in humans. Nomothetic theory– this is good because biological theories can be applied to everyone, as everyone has the same biology. GENDER BIAS—focus on men but women show important role for testosterone ETHICAL ISSUES—in socially sensitive research Coupis and Kennedy (2008) – found that, in mice, a reward pathway in the brain becomes engaged in response to an aggressive event and that dopamine is involved as a positive reinforcers in this pathway. Scerbo and Raine 1993 – meta-analysis of 29 studies published before 1992 which examined neurotransmitter levels in antisocial children and adults – these studies consistently found no significant rise of dopamine levels