Table 1 Summary of the number of cases, mean ages, and standard deviation (SD) of each group of samples used in the present study including substantia nigra, frontal cortex area 8, angular gyrus, precuneus, and putamen. MA: middle-aged; PD: Parkinson’s disease

MA

N = 11

N = 16

N = 10

N = 11

N = 15

65.67 ± 12.76

63.88 ± 12.65

60.90 ± 10.28

64.64 ± 15.09

70.27 ± 8.89

PD stages 1-2

N = 6

N = 2

-

-

-

80.17 ± 9.20

73.50 ± 2.12

PD stages 3-4

N = 22

N = 17

N = 8

N = 10

N = 7

76.55 ± 6.93

70.12 ± 8.40

66.50 ± 6.52

76.80 ± 7.73

76.00 ± 13.10

PD stages 5-6

N = 17

N = 12

N = 4

N = 4

N = 2

78.82 ± 6.15

77.83 ± 4.51

79.25 ± 3.40

81.25 ± 3.86

78.00 ± 1.41