Tuesday, 20 December 2011

Anger and the Brain/The Neuropsychology of Anger

Often the terms anger and aggression are used interchangeably; however this is somewhat of a faux pas as anger is a feeling and aggression is a behaviour. Central to the neuroanatomy of anger are the amydala, sitting deep with the medial temporal lobes. In cases of anger the amygdala proverbally hijack the prefrontal cortex, driving responses emotionally and impulsively rather than cognitively through reasoning. Biologists have correlated increased testosterone levels with increased amygdala activity.

The hypothalamus is also very important in a neuropsychological understanding of anger. So called 'sham' rage has been manufactured in animal studies where lesions have been introduced to the hypothalamus. More specific animal lesion studies have revealed lateral stimulation results anger with attack responses (Flynn, 1967). Obviousely, ethical criticisms are not the only limitations to these sort of studies as generalisability to humans is at best speculative.

The anterior cingulate cortex, in rather crude terms lies neatly between the affective and cognitive divisions of the brain. More animal experiments have implicated this area of the brain in anger emotional process (Kordidze and Oniani, 1972). But again one has to question whether we can measure the emotions of animals or are we at best merely studying behaviour?

Dougherty et al. (1999) has studied human anterior cingulate cortex activation through inducting anger through narrative scripts and measuring blood flow using PET techniques. Poor scanner accuraacy and high expense limits the value of these types of PET studies, however Denson et al. (2009) used fMRI to reaffirm PET evidence. 

The orbito frontal cortex is implicated in impulse control. Bechara et al (1994) carried out lesion studies and ran gambling tasks. The researchers witnessed reckless behaviour in orbito frontal cortex lesion patients. Blair et al (1999) and his high profile psychopathy studies found increased orbito frontal cortex activation for angry faces but not sad or neutral.

The ventromedial cortex activation in anger has also been demonstrated through PET studies Dougherty et al. (2004) CT evidence (Grafmann et al. 1996) and fMRI studies (Lotze et al. 2007).

 Kalbe et al. (2004) studied the dorsolateral prefrontal cortex and its role in anger. The researchers found when the dorsolateral prefrontal cortex was active the orbito frontal cortex is inhibited further inhibiting its affective cue processing. Alternatively, when its inhibited the OFC is active and aggressive behaviour is likely to be carried out.

In conclusion, although we now understand which areas of the brain appear to be involved in anger processing, nearly all research relies upon anger induction, often asking people to relive memories. Can we equate this with emotion or is it more similar to a cognition or a cognitised emotionally rich memory?

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