Extraversion (E): activated principally in front of forebrain -- anterior to central sulcus
--personality—the prefrontal cortex is the most significant area for creating one’s outward “personality”.
--Expressing language through conversation/speech (activated by Brocas [left anterior forebrain]). In general, Extraverts speak more and louder than Introverts. (Nurturing, environment, and genetic variances also affect speech patterns; thus explaining most speech differences among Extraverts [and Introverts].)
A University of California medical school used PET scans to examine brain regions of people while speaking. They looked at the brain while they (1) made nonsense syllables, (2) recited the months of the year, and (3) recited a briefly memorized prose passage. While both the "mindless" recitation of the months and the prose passage used Wernicke's area (the top back part of the temporal lobe), ONLY the prose showed activity in Broca's area. The conclusion: rote memorized verbal tasks require little thought or sophisticated cortical activity. Bookheimer, S., et al. 2000. Neurology, Vol 55(8), 1151-1157.
--voluntary motor movements (activated by primary motor cortex—anterior to central sulcus). Moving the body is an Extraverted (energy-expending) function, activated by the motor cortex.
--high degree of “attention” to outside world (principally a function of the anterior forebrain—especially right superior frontal gyrus)
--expressing emotion (left anterior forebrain)
--dopamine (a neurotransmitter that says “do it” is primarily in anterior forebrain.
--cingulate gyrus—regarded as the volition and will center (located in anterior forebrain); it causes humans to act. In addition, Extraverts are innately designed to expend energy whereas Introverts conserve it.
--planning—an integral part of taking action and expending energy.
Planning involves maintaining one main goal while working on sub-goals for that main goal. This is apparently one of the unique human brain functions. The National Institutes of Health in Bethesda, Maryland has published findings that show that that particular task is performed in the most anterior part of the frontal lobes called the fronto- polar prefrontal cortex. Koechlin et. al, Nature 1999, vol 399(6732) 148-151.