Differences between the extroverted brain and the introverted brain

By Jenny Tang

 An extroverted person is one who feels “charged” after social interaction (Mesurado et al., 2014), whereas an introvert feels “charged” through its absence, feeling that social interaction is draining. Introversion and extroversion are not simply theoretical concepts, but can be physically observed through the use of imaging to understand their function. 

    The way we respond to dopamine varies between an introverted and an extroverted individual. Extroverted individuals tend to have a much more efficient dopamine system in comparison (Fischer, Lee and Verzijden, 2018). Dopamine is a neurotransmitter, known as the feel-good transmitter, which is strongly associated with pleasure and reward. A study, performed by Cornell university, had a mix of introverts and extroverts who were identified through a standard personality test. In the first four days some participants received a dose methylphenidate, or more commonly known as Ritalin, which triggers the release of dopamine. The other participants received a placebo. The researchers tested how strongly the contextual cues in the lab were associated with reward, by monitoring changes in their working memory, motor speed and positive emotions, which are all characterized as being influenced by dopamine. The individuals who associated the lab contextual cues with rewards were also all identified as extroverts; meaning that extroverted individuals are more likely to associate cues with feelings of rewards (Depue and Fu, 2013).

 The activity of cerebral flow differs between the two types of individuals, proving another functioning difference. In introverts, it is found that they have more activity in the putamen. (Veena et al., 2004). The University of Iowa examined individuals through a positron emission tomography scan (PET scan) and found that introverted individuals had more activity in the frontal lobes, and the more frontal side of the thalamus. On the other hand, individuals who were identified as extroverts tended to have more activity in the anterior cingulate gyrus, temporal lobes, and the posterior thalamus. These identified regions are more involved with sensory processing, where the area with the most blood flow in introverts was associated with internal processing. This concludes the idea that introverts are more likely to be able to find stimuli within themselves, whereas extroverts seek to find stimuli externally (Johnson et al., 1999). 

   Researchers in the University of Amsterdam asked for volunteers and used a standardised personality quiz to identify those who are either an introvert or extrovert. The researchers had the volunteers gamble, while the researchers monitored the amygdala and the nucleus accumbens in their brains. The amygdala is tied to emotions and the nucleus accumbens tied to processing dopamine. Both of these regions were related to excitement and rewards. They had found that the participants that were identified as extroverts had a greater reaction in those two regions when they are gambling. This means that the extroverted brain produces more dopamine, wired to seek out rewards through social activities, or more ‘thrilling’ activities, like meeting new people, or trying new activities. On the other hand, an introvert may find more pleasure in reading a book in comparison to going out because their brains are not wired to seek excitement through social activities (Cohen et al., 2005).

 The way that the extrovert and introvert brain functions differs from each other, especially in regard to how they are stimulated, with introverts able to be stimulated from within while extroverts actively seek stimulation externally.  The levels of brain activity differ between introverts and extroverts, further proving that the term introversion and extroversion is more than just a personality characteristic but is also a physiological difference in individuals’ brains. 

References:

Cohen, M.X. et al., 2005. Individual differences in extraversion and dopamine genetics predict neural reward responses. Cognitive Brain Research. Available at: https://www.sciencedirect.com/science/article/pii/S0926641005002880 [Accessed February 23, 2021].

Anon, Figure 2f from: Deady R, Heller K, Work T, Venier L (2014) Peyerimhoffia jaschhoforum (Diptera, Sciaridae), a new deadwood inhabiting species from Canada. Biodiversity Data Journal 2: e4200. https://doi.org/10.3897/BDJ.2.e4200.

Fischer, R., Lee, A. & Verzijden, M.N., 2018. Dopamine genes are linked to Extraversion and Neuroticism personality traits, but only in demanding climates. Nature News. Available at: https://www.nature.com/articles/s41598-017-18784-y [Accessed February 23, 2021].

Johnson, D.L. et al., 1999. Cerebral Blood Flow and Personality: A Positron Emission Tomography Study. American Journal of Psychiatry. Available at: https://ajp.psychiatryonline.org/doi/full/10.1176/ajp.156.2.252 [Accessed February 23, 2021].

Kumari, V. et al., 2004. Personality predicts brain responses to cognitive demands. The Journal of neuroscience : the official journal of the Society for Neuroscience. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6730115/ [Accessed February 23, 2021].

Y;, D.R.A.F., On the nature of extraversion: variation in conditioned contextual activation of dopamine-facilitated affective, cognitive, and motor processes. Frontiers in human neuroscience. Available at: https://pubmed.ncbi.nlm.nih.gov/23785330/ [Accessed February 23, 2021].

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