Subjects

A total of 79 PD subjects (43 TD and 36 PIGD patients) and 31 NCs were recruited for this study from the Second Affiliated Hospital of the Zhejiang University School of Medicine. All participants were right handed. The PD patients were all diagnosed according to the United Kingdom Parkinson’s Disease Brain Bank (Hughes et al., 1992) by an experienced neurologist. Before a magnetic resonance imaging (MRI) scan and clinical assessments, the PD patients were asked to withdraw from all anti-Parkinson medications for approximately 12 h. The Unified Parkinson’s Disease Rating Scale (UPDRS), the Hoehn and Yahr disability scale (HY) and the Mini-Mental Sate Examination (MMSE) were obtained from each PD subject. Psychiatric or other neurological illnesses constituted exclusion criteria as Miroshnichenko et al. reported (Miroshnichenko et al., 2018). All subjects were free of hypothyroidism, epilepsy, drug/alcohol/nicotine abuse, and free of kidney or liver disease. The patients’ tremor scores were defined by summing items 16 and 20–21 of the UPDRS and dividing the sum by 3, and the balance and gait score were defined by adding items 13–15 and 29–30 and dividing the sum by 5. Patients were determined as TD if the ratio of the tremor score divided by the balance and gait score was ≥1.50, and as PIGD if the ratio was ≤1 (Huertas et al., 2017). The levodopa equivalent dose (LED) was calculated as formerly reported (Tomlinson et al., 2010). Every subject signed informed consent. This study was approved by the Ethics Committee of the Second Affiliated Hospital of the Zhejiang University School of Medicine.