 Many personality traits have a genetic component and are highly heritable.Maladaptive levels of certain traits may be acquired as a result of anoxic or traumatic brain injury, neurodegenerative diseases such as Parkinson's disease, neurotoxicity such as lead exposure, bacterial infection such as Lyme disease or parasitic infection such as Toxoplasma gondii as well as hormonal influences.While studies are still continuing via the use of various imaging techniques such as fMRI; these traits have been shown to originate in various regions of the brain such as the amygdala and the prefrontal cortex.