Novelty seeking and harm avoidance in Parkinson's disease: effects of asymmetric dopamine deficiency

Objectives: Although changes in novelty seeking and harm avoidance have been reported among patients with Parkinson's disease (PD), the findings regarding the neurochemical correlates of such changes are inconsistent. This study was designed to examine the hypothesis that different patterns of motor and neurochemical asymmetry in PD may have contributed to the conflicting results. Methods: Forty PD patients (divided into two groups according to initial asymmetry in dopamine deficit: left hemisphere, n=22; right hemisphere, n=18) and 17 age matched healthy controls completed the Tridimensional Personality Questionnaire (Cloninger, 1987). Results: Only patients with greater dopamine loss in the left hemisphere showed reduced novelty seeking, whereas only patients with reduced dopamine in the right hemisphere reported higher harm avoidance than matched healthy controls. Novelty seeking was not associated with disease duration, current motor symptoms, or medication, whereas harm avoidance was significantly correlated only with the severity of bradykinesia and depression. Conclusions: Approach and avoidance reflect different patterns of dopaminergic asymmetry. Whereas reduced novelty seeking reflects deficit in the mesolimbic branch of ascending dopamine transmission in the left hemisphere, increased harm avoidance is associated with greater dopamine loss in the right striatum.