PERSONALITY [ back to Glossary Index ]
Personality refers to the qualities of one's psyche and the style one uses in interacting with others or handling life's situations. It is often expressed in dichotomies like introverted/extroverted, inhibited/adventurous, approach/avoid, submissive/assertive, passive/active, optimistic/pessimistic, materialistic/spiritual, selfish/generous, intellectual/passionate, straight shooter/devious and the like. Neuro-behavioral research on animals, human twins, human stroke victims, and others, is beginning to shed some real light on the genetic, neuro-chemical and environmental factors which influence personality. Psychologist Richard Davidson of the University of Wisconsin has used PET scanners and fMRI scanners to confirm that the left frontal lobe is associated with a happy, optimistic outlook while the right frontal lobe is linked to cautious, worried and more  negative outlook. His research has also confirmed that different individuals characteristically react to experiences by "lighting up" the left or right frontal lobe which correlates with "seeing the glass half full or half empty."

This corresponds with how persons change after a TBI. Major injury confined to the left frontal lobe produces much misery and suffering (because it knocks out the happiness circuits), while major injury confined to the right frontal lobe tends to produce placid indifference (because it knocks out the worry circuits). Mild TBI may accentuate the dominant emotional style of the dominant lobe, for example someone with chronic mild depression may become extremely depressed. Another finding is that individual genetic endowment and the home-family environment of early childhood will set stable adult levels of neurotransmitters. For example a person with low serotonin may feel mildly depressed, anxious and irritable and seek out alcohol as a way of achieving relaxation and relief from worry. A person with high norepinephrine may feel energized, racy and ready for action. A TBI can cause personality change by reducing production of one or more neurotransmitters, changing the existing equilibrium and resetting the mix of neuro-chemicals. This can cause change in one's characteristic mood, outlook and energy level. An energetic, go-getter can become tired, withdrawn and discouraged. Accurate diagnosis can lead to administration of medications like Prozac or Zoloft which boost depleted serotonin and improve mood.