title: Effect of expectancy and personality on cortical excitability in Parkinson's disease.
abstract: Our previous studies in Parkinson's disease have shown that both levodopa and expectancy of receiving levodopa reduce cortical excitability. We designed this study to evaluate how degree of expectancy and other individual factors modulate placebo response in Parkinson's patients. Twenty-six Parkinson's patients were randomized to 1 of 3 groups: 0%, 50%, and 100% expectancy of receiving levodopa. All subjects received placebo regardless of expectancy group. Subjects completed the NEO-Five Factor Inventory, General Perceived Self-Efficacy Scale, and Perceived Stress Scale. Cortical excitability was measured by the amplitude of motor-evoked potential (MEP) evoked by transcranial magnetic stimulation. Objective physical fatigue of extensor carpi radialis before and after placebo levodopa was also measured. Responders were defined as subjects who responded to the placebo levodopa with a decrease in MEP. Degree of expectancy had a significant effect on MEP response (P < .05). Subjects in the 50% and 100% expectancy groups responded with a decrease in MEP, whereas those in the 0% expectancy group responded with an increase in MEP (P < .05). Responders tended to be more open to experience than nonresponders. There were no significant changes in objective physical fatigue between the expectancy groups or between responders and nonresponders. Expectancy is associated with changes in cortical excitability. Further studies are needed to examine the relationship between personality and placebo effect in Parkinson's patients. © 2013 Movement Disorder Society.
authors: Department of Neurology, Oregon Health & Science University, Portland, OR, USA. louja@ohsu.edu
authors: Jau-Shin
authors: JS
authors: Lou
authors: Diana M
authors: DM
authors: Dimitrova
authors: Richard
authors: R
authors: Hammerschlag
authors: John
authors: J
authors: Nutt
authors: Elizabeth A
authors: EA
authors: Hunt
authors: Ryan W
authors: RW
authors: Eaton
authors: Sarah C
authors: SC
authors: Johnson
authors: Melanie D
authors: MD
authors: Davis
authors: Grace C
authors: GC
authors: Arnold
authors: Sarah B
authors: SB
authors: Andrea
authors: Barry S
authors: BS
authors: Oken
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000978:Antiparkinson Agents / Q000627:therapeutic use; D002540:Cerebral Cortex / Q000187:drug effects / Q000503:physiopathology*; D004311:Double-Blind Method; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005221:Fatigue / Q000209:etiology; D005260:Female; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009042:Motivation / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology; D010300:Parkinson Disease / Q000188:drug therapy / Q000473:pathology / Q000523:psychology; D010551:Personality / Q000502:physiology*; D010555:Personality Inventory; D011795:Surveys and Questionnaires
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa
keywords: Parkinson's disease; cortical excitability; expectancy; levodopa; transcranial magnetic stimulation (TMS)
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