The biology of personality and temperament
Published: 10-01-2014 Edited: 03-06-2015
- Various research have found that dopamine receptors, serotonin receptors and serotonin transporter variants in the dopamine and serotonin system are making the foundation for how our brain regulates the automatic vs. controlled behavior, the top-down vs. bottom-up attention balance and also to how high extent we use creative-thinking and when.
These variants are inturn strongly inherited and found in our DNA code. This means personality is to a large extent inherited and that our differences in personality and temperament are defined by DNA and epigentic processess. [1, 2]
While the dopamine-system is involved in setting up cognitive networks in the prefrontal cortex to meet the requirements of any situation it is also used to sustain attention to the same task over time (top-down attention with increased working memory and dopamine) or follow new opportunities in the moment (bottom-up attention with decreased working memory and dopamine) . It acts by holding a "carrot-on-a-stick" of anticipation for sustaining the attention or shifting the attention to new stimuli. [15, 16, 17, 18, 24]
The ventral-attention network (VAN) works as a circuit breaker for the goal-directed attention when unexpected stimuli comes in . The regulating of attention is done via the frontoparietal control network (FPCN) [9, 19]. ADHD are also found to have an abnormality in the regulating of attention related to these networks .
Differences in the dopamine-system also influences our creative-thinking.
People can become more creative by listening to the ideas of others, this can be seen as a bottom-up modulation of attention .
The creative-thinking is associated with having a closer connectivity between the dorsal attention network (DAN) and the default-mode network (DMN), this is also strongly inherited and defined by the dopamine-variants in the prefrontal cortex. Having a closer connectivity is also correlated with most psychiatric problems. [4, 5, 6]
Cognitive vs affective, cognitive style and affective style
Having a low level of serotonin are associated with making automatic or reflexive judgements, black-and-white analysis and low ability of behavior inhibition. Having high level of serotonin are associated with being able to make verbal judgments, nuanced analysis, controlled or reflective behavior. The serotonin is used to a large extent to be status-indicator for the "modus-operandi", telling the body how well you are doing things you should be doing. Being away from physical needs such as food, sex and social stimuli decreases serotonin and doing things you should be doing increases it. [10, 11, 12, 13]
There are individual differences in how people's working memory are connected to other functions of the brain, meaning that people have different kinds of goal-directed cognition.  Individual differences in behavior can be explained by how the frontoparietal network connects to other networks.  The frontoparietal networks regulates between top-down and bottom-up attention.  Visual processes that process irrelevant information is wired into the default-mode network (to build contextual information) and visual processes that processes relevant information are wired to the frontoparietal network.  The anticipation of bottom-up attention vs top-down attention is driven by motivational signals triggered by dopamine. 
How it all relates to the Neojungian Typology
In Neojungian Typology, different types are defined by having different variants of molecules of serotonin and dopamine in their prefrontal cortex. This results in differences in attention (top-down vs bottom-up) and what behavior is rewarding for the individual (cognitive vs affective) and also when individuals prefer applying creative thinking. This is the foundation for the next revision of the model.
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To be continued..