The PET scans revealed that introverts have more activity in the frontal lobes of the brain and anterior, or front, thalamus. These areas are activated when a person's brain takes on internal processing such as remembering, problem solving, and planning. Extroverts exhibit more activity in the anterior cingulate gyrus, temporal lobes, and posterior thalamus. These areas are typically thought to be more involved in sensory processing such as listening, watching, or driving. Differences in cognitive style and sensory-processing relate to characteristics associated with introversion and extroversion.
True introverts are quiet, inwardly focused, and reclusive.
Extroverts are gregarious, socially active, and sensation seeking. Introverts get more of their stimulation internally, whereas extroverts seek outside sources. These variations in brain activity suggest that a lot of our individual differences have an underlying biological cause. Previously, only the faint, fading afterglow of the event had been detected. It was the brightest burst seen so far.