Tag Archives: nucleus accumbens

Introversion and Extraversion Starts with Your Genes and Shows in Your Brain

Susan Cain

Susan Cain

Introverts seem to be experiencing an increasingly “level playing field” in work and social environments after Susan Cain’s best-selling book celebrating “the power of introverts in a world that can’t stop talking.”

Hans Eysenck

Hans Eysenck

University of London’s Hans Eysenck provided one of the first physiological explanations of this duality after Carl Jung’s introduction to “psychological types.”

The subjective experience of introversion and extraversion is measured by the Big Five personality dimensions, developed by Robert McRae and Paul Costa, then of the National Institutes of Health, in addition to the widely-used yet psychometrically-criticized Myers-Briggs Type Indicator. 

Eysenck's Three-Factor Theory of Personality

Eysenck’s Three-Factor Theory of Personality

Observable behaviors associated with extraversion include positive emotions, assertiveness, sociability and talkativeness with energetic engagement in work and social contexts.

In contrast, external manifestations of introversion are lower social engagement and energy, and less need for external social stimulation than extraverts, with a quieter, more deliberate style.

Robert McCrae

Robert McCrae

These behaviors are at least partially based on individuals’ genetic profiles, leading to differing brain activity associated with introverted and extraverted thinking and behavior.

Paul Costa

Paul Costa

Eysenck posited that extraverts and introverts differ in their levels of cortical arousal:  Introverts, he suggested, have a higher baseline level of arousal than extraverts, so need less external stimulation.

In contrast, he hypothesized that extraverts seek external stimulation because they have a lower baseline level of cortical arousal.

Yasuyuki Taki

Yasuyuki Taki

Differences in brain structure and function among introverts and extraverts was analyzed by Yasuyuki Taki’s team at Tohoku University, including collaborators  Benjamin Thyreau, Shigeo Kinomura, Kazunori Sato, Ryoi Goto, Kai Wu, Ryuta Kawashima, and Hiroshi Fukuda. 

The evaluated whether personality traits measured on a revised Big Five inventory (Revised NEO Personality Inventory – NEO-PI-R) were related cortical gray matter volume, measured by brain magnetic resonance images (MRI) for more than 270 healthy volunteers over 6 years.

Colin DeYoung

Colin DeYoung

Likewise, University of Minnesota’s Colin DeYoung, Jacob Hirsh of University of Toronto, The Mind Research Institute’s Matthew Shane, and Yale’s Xenophon Papademetris, Nallakkandi  Rajeevan, and Jeremy Gray used a similar method to conclude that behavioral and subjective extraversion was positively correlated with orbitofrontal cortex metabolism and increased cerebral volume of the medial orbitofrontal cortex in 116 adults. 

Michael X. Cohen

Michael X. Cohen

Extraversion has been correlated with sensitivity to rewards and to the brain’s dopamine system, so University of Amsterdam’s Michael X. Cohen and team investigated the brain’s dopamine-based reward system.

He collaborated with Jennifer Young, Jong-Min Baek, Christopher Kessler, and Charan Ranganath of University of California, Davis to demonstrate the connection among trait extraversion, the A1 allele on the dopamine D2 receptor gene, and “extraverted” activity in the brain’s reward system during a gambling task.

Charan Ranganath

Charan Ranganath

Participants received rewards either immediately following a behavioral response or after a 7.5 second “anticipation” interval.
The research team monitored differing fMRI brain activity in the amygdala, which processes emotional stimuli and triggers excitement, and in the nucleus accumbens, which pushes people to seek rewards, novelty and risks.

Brain activation patterns were related to individual differences in extraversion and presence of the A1 allele on the dopamine D2 receptor gene.
Neural pathways differed for extraverts and introverts, validating anecdotal observations that these personality styles are distinctly different, even deep inside the brain and genes.

Many introverts adopt extraverted behaviors in work and social situations, and a remaining question is how fMRI patterns differ for introverts displaying uncharacteristic extraverted behaviors in contrast to people with trait extraversion.

-*How easily can you adopt your non-dominant personality style when you need to display introversion or extraversion behaviors?

-*What tactics enable you to adopt your less-preferred personality style?

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Juggling as Brain Training

The physical skill of juggling can change the brain’s structure and function for the better, and may be a recommended therapy for brain injuries.

Bogdan Draganski

Bogdan Draganski

Volker Busch

Volker Busch

Bogdan Draganski, now of University of Lausanne collaborated with University of Regensburg colleagues Volker Busch, Ulrich Bogdahn, and Gerhard Schuierer, and Arne May, now of University of Hamburg  with Christian Gaser of University of Jena, to visualize brain plasticity among volunteers who learned to juggle.

Ulrich Bogdahn

Ulrich Bogdahn

Volunteers showed transient and selective structural changes in the left parietal lobe’s posterior cortex  and bilateral central temporal areas brain, areas associated with processing and storing complex visual motion on used whole-brain magnetic-resonance imaging.

Gerhard Schuierer

Gerhard Schuierer

This study demonstrates that the brain’s macroscopic structure can change based on stimuli like juggling, rather than being limited to functional changes in the cortex.

Arne May

Arne May

May and Gaser collaborated with University of Hamburg colleagues Janina Boyke, Joenna Driemeyer, and Christian Büchel in related research.

Christian Gaser

Christian Gaser

This time, they trained 25 people with an average age of 60 years in juggling for 12 weeks, and 25 control group volunteers were not trained.

Christian Büchel

Christian Büchel

The team conducted three MRI brain scans for each participant:

  • Before juggling practice
  • After 3 months of juggling
  • After another 3 months of no juggling.

Jugglers showed significant increase in the brain’s “gray matter,” nerve cells’ bodies responsible for information processing, located in the hippocampus (memory formation), bilateral nucleus accumbens (reward systems that may lead to action) and visual cortext’s middle temporal area.

Without practice during the three months after the training, none of the volunteers retained their ability to juggle and their gray matter declined to pre-training levels.

This suggests the value of continued practice in physical and cognitive skills to maintain brain structure and function.

Jan Scholz

Jan Scholz

University of Oxford’s Jan Scholz, Miriam Klein-FlüggeTimothy E.J. Behrens, and Heidi Johansen-Berg extended this research to demonstrate that people who learn to juggle also increased “white matter” containing axons that connect different cells, not just gray matter.

 The Oxford team conducted baseline brain scans using diffusion tensor imaging to reveal  white matter structure for 24 young men and women volunteers, who later practiced juggling for half an hour a day for six weeks.

Miriam Klein-Flügge

Miriam Klein-Flügge

The researchers compared brain scans of 24 non-juggling volunteers and found that the volunteer jugglers increased white matter in the parietal lobe’s intraparietal sulcus, which integrates vision and reaching and grasping in the periphery of vision.
Even less-skilled jugglers had similar increases in white matter, attributed to amount of time devoted to practice.

Heidi Johansen-Berg

Heidi Johansen-Berg

In contrast, the non-jugglers showed no changes in white matter after the six week period, suggesting value in practicing juggling to develop the brain’s structure and functioning to enable rapid, coordinated movement and body positioning.

Brain scans taken after four weeks without juggling practice showed that the new white matter remained and the amount of gray matter increased, showing some skill retention in the absence of consistent practice.

-*What physical skills do you develop as brain training?

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Spreading Good News Feels Good, Especially When It’s About You

Christian Science Monitor has long provided a counterpoint to mainstream media’s “If it bleeds, it leads” approach to providing shocking, scandalous, depressing, or scary news.

Jonah Berger

Jonah Berger

Wharton’s Jonah Berger and Katharine Milkman found that the Christian Science Monitor might have a savvy business model:  they found that good news spreads more widely than bad.

Word of Mouth Marketing AssociationMembers of the Word of Mouth Marketing Organization: Take note…

Katherine Milkman

Katherine Milkman

Berger and Milkman evaluated a random sample of 3,000 of more than 7,500 articles published in the New York Times online from August 2008 to February 2009.

They judged each article’s “popularity” based on number of times it was forwarded to others, after controlling for online publication time, section, and degree of promotion on the home page.
Independent readers rated each article for practical value or surprise, and ratio of positive vs negative emotion words in each news item.

Most-forwarded posts were positive, funny, exciting and featuring intellectually challenging topics, like science, that “inspire awe” (“admiration and elevation in the face of something greater than the self”).

Readers shared articles that typically provoke negative emotions like anger and anxiety, but not sadness.
-*Why this bias against sending “downer” messages?

Emily Falk

Emily Falk

Michigan’s Emily Falk, with UCLA colleagues Sylvia Morelli, B. Locke Welborn, Karl Dambacher,and Matthew Lieberman found that people consider what appeals to others, possibly as a means of building relationships, indicated by increased activation in brain regions (temporoparietal junction, or TPJ and dorsomedial prefrontal cortex) associated with “social cognition,” or thoughts about other people, measured by fMRI.

When those regions were activated, people were more likely to talk about the idea with enthusiasm, and the idea would spread by word-of-mouth.

Falk noted that the team mapped  brain regions “associated with ideas that are likely to be contagious and are associated with being a good ‘idea salesperson.'”
She plans to use these brain maps “to forecast what ideas are likely to be successful and who is likely to be effective at spreading them.”

Diana Tamir

Diana Tamir

People also like to spread good news about themselves.
Diana Tamir and Jason Mitchell, then of Harvard, illustrated that brain regions associated with reward (mesolimbic dopamine system, including the nucleus accumbens and ventral tegmental area) are activated when people share information about themselves.

Jason Mitchell

Jason Mitchell

Self-disclosure is so pleasurable that people will sacrifice monetary rewards for this opportunity.

Mor Naaman

Mor Naaman

In fact, Rutgers’ Mor Naaman with Jeffrey Boase, now at Ryerson University and Chih-Hui Lai, now of University of Akron found that 80 percent of Twitter users tweet primarily about themselves.
One reason may be that people say more positive things when they’re talking to a bigger audience, like Twitter followers, according to Berger’s research suggests. As a result, social media users are likely to convey positive information about themselves.

Jeffrey Boase

Jeffrey Boase

However, this positive self-presentation may not result in a positive mood if communicators spend longer on social media platforms like Facebook.
Hui-Tzu Grace Chou and Nicholas Edge of Utah Valley University found that those with longer visits to Facebook say they are less happy than their Facebook Friends.

They found that Facebook users tend to form biased judgment based on easily-recalled examples (availability heuristic) and erroneously attribute positive Facebook content to others’ personality, rather than situational factors (correspondence bias), especially for those they do not know personally.

Hanna Krasnova

Hanna Krasnova

Corroborated by Humboldt-Universität zu Berlin’s Hanna Krasnova and her team from Technische Universität Darmstadt, these researchers observed “invidious emotions” and “envy” among people who spend longer time on Facebook.

These findings have relevance to members of the Word of Mouth Marketing Organization: Spread the good word – or at least the emotional word – and spend less time on Facebook and other social media that might invite social comparison and the potential for envious dissatisfaction.

-*How you build “buzz” via “Word of Mouth”?

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