Relation of "sense of self" to executive function performance in Parkinson's disease

Background: Recent reports have linked impairment of various aspects of the sense of self to frontal brain dysfunction. Independent evidence suggests that patients with Parkinson's disease exhibit impairment on cognitive tasks that depend on the frontal lobes. Objective: To test the hypothesis (1) that the sense of self would be impaired in some persons with Parkinson's disease and (2) that this impairment would be linked to frontal dysfunction. Methods: Sentence completion tests of identity development ("self-test") and measures of frontal and temporal lobe functioning were administered to 20 people with Parkinson's disease and to 10 age-matched healthy controls. Results: While self-test responses significantly correlated with performance scores on tests of executive function (for Parkinson's disease patients only) but not temporal lobe function (as measured by "clustering" rates on a fluency task), we found no significant differences in mean self-test scores between persons with Parkinson's disease and age-matched controls. Analysis of the 160 self-test responses revealed a shift toward conformist responses in Hoehn-Yahr stage III as compared with stage II Parkinson's disease patients. Conclusions: While the sense of self changes as a function of disease stage, the core experience of self in Parkinson's disease is intact but may depend, in part, on frontal lobe function.