Despite the emphasis on the motor function of Parkinson's disease (PD), several studies have shown that the nonmotor symptoms have a greater significance than the motor symptoms when assessed in terms of quality of life measures, institutionalization rates, or health economics. They include depression, apathy, sleep disorders, cognitive impairment and dementia, autonomic, gastrointestinal, and sensory symptoms in particular. Dopamine replacement therapy in PD (and high doses of DA agonists in particular) can lead to several neuropsychiatric side effects such as the development of hallucinations, psychosis, somnolence, disorders of impulse control such as pathological gambling, and dopamine dysregulation syndrome. Cognitive and neuropsychiatric after effects of surgical treatments for PD and specifically deep brain stimulation of the subthalamic nucleus bilaterally have also drawn special attention.

We particularly take an interest in manuscripts that report epidemiological data for different nonmotor symptoms of PD, deal with appropriate instruments and investigations for diagnostic and long-term monitoring purposes, and explore pathophysiological mechanisms of specific symptoms such as, using imaging techniques. Drug trials, surgical outcomes that deal with nonmotor aspects, and reviews that summarize the results of clinical therapeutic trials as well as nonmotor side effects of established treatments of PD are welcome. Main topics include, but are not limited to:

• Mild cognitive impairment and dementia in PD
• Impulse control disorders and dopamine dysregulation syndrome
• Psychosis
• Apathy, anxiety, depressive symptoms, and depression
• Sexual disturbances and somnolence
• Imaging of nonmotor symptoms of PD
• Instruments for screening and monitoring of specific nonmotor symptoms
• Psychiatric and other nonmotor side effects of dopaminergic drugs and deep brain stimulation for PD
• Effects of nonmotor symptoms on quality of life
• Reviews of treatment strategies for nonmotor symptom of PD

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/pd/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: