Rostrocaudal gradient of CSF and DJ-1 or α-synuclein levels in CSF. The early CSF fractions (<10th ml, Early F), middle fractions (10–15th ml, Middle F) and late fractions (15–20th ml, Late F) in the control group were assessed. Samples included young (mean 29.1, range 21–40, n = 15), middle age (mean 59.8, range 55–64, n = 15) and old (mean 78.8, range 75–83, n = 15) controls. No significant difference was observed in different fractions when the average DJ-1 (A) or α-synuclein (SNCA) (C) levels were compared, with or without eliminating the samples with >200 ng/ml haemoglobin levels. The levels of DJ-1 (B) or α-synuclein (D) in different CSF fractions in individual samples were also compared after cases with high haemoglobin levels were omitted. Each symbol represented one participant and the three fractions from the same participant were linked. No significant difference among fractions was observed in individual samples.