Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

Neuroanatomy of aggression (seconds before the aggressive behavior)

What's our main "aggressive" brain structure? What else does it do? What's the evidence?

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  The amygdala!
  
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  Also does: fear and anxiety, male sexual motivation, emotional memories
  
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  Evidence: from lesions, stimulation, recording: all our traditional methods.
  
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    Those with amygdalectomies don't understand angry faces, won't defect against cheaters, a lot less violent.
    
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      Note: they tend not to look at the eyes of scary faces. Interpretation: they're less sensitized to aggressive releasing stimuli in the world.
      
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    Scary images activate the amygdala.
    
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    Epileptic foci near the amygdala bring aggressive thoughts just before seizure.
    
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    Charles Whitman, famous mass murderer, had inexplicable aggressive thoughts leading up to the event, also had amygdala tumor.
    
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    Amygdalae in those with social phobia activate in response to faces
    
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    Amygdalae in those with major depressive disorder activate in response to sad faces
    

Frontal cortex

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  How do frontal cortex neurons help you do the harder but right instead of easier but wrong decision?
  
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    They modulate and potentiate other neurons to fire at lower thresholds. Not so much about direct activation.
    
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    They use dopamine to fuel goal-directed behavior to get the reward
    
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  What is executive function? How is it shown?
  
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    It's the keeping in mind of rules. It allows you to override your impulses.
    
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    It "chunks" the list of grocery items into logical categories
    
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    Postpones gratification.
    
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  How does the legal system treat culpability in the context of knowing right/wrong, doing the right/wrong thing, and the frontal cortex?
  

  • You can know right from wrong, but with frontal cortex damage, you can't make the right choice.

  • Shown by the M&Ms study. Reach for 1, get 5. Reach for 5, get 1. With frontal damage you can't help but reach for 5.

  • The M'Naghten Rule: you're not culpable if you can't tell right from wrong. But those with frontal cortex damage can tell right from wrong, but have instead a organic involution. Can't engage the right action.

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  But how is this "frontal cortex loss = aggression" story complicate? What various forms can frontal disinhibition
  

take?

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  Some people with frontal cortex are just really "aggressive" chess players or are disinhibited when it comes to telling knock-knock jokes.
  
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  Old people lose frontal cortex neurons and sometimes they're just inappropriately critical.
  
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  What is repressive personality and what frontal cortex patterns is associated with it?
  
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    Highly disciplined and regulated. Not depressed or anxious. Tend to be successful.
    
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    Elevated stress hormone levels even when not stressed. Frontal cortex has hypermetabolism even at baseline.
    
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  Compare that to sociopaths
  
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    Aggression without remorse and without feeling
    
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