Test-retest Reliability at Region Level
Whole-brain voxel-wise test-retest reliability estimates were unsatisfactory for all three attention network contrasts: alerting, orienting, and executive. As demonstrated byFigure S2 , only a small portion of isolated brain clusters exerted a reliability larger than 0.5 for both the PD and HC groups.
As the whole-brain voxel-wise analysis was not convenient to compare and summarize, we also conducted a region-based analysis to compare ICC maps for the three-attention network contrasts and their associated condition estimates. The region-based ICC maps were calculated using mean region activation. Although averaging activations within the brain region may sacrifice the true signal, it can significantly facilitate explanation. Generally, reliability estimates for the three attention network contrasts were lower than their corresponding condition contrast(Figure 3, supplementary Figure S3) .
The reliability estimates were acceptable for the congruent (median ICC = 0.59, 95%CI: [0.19, 0.79]) and incongruent condition (median ICC = 0.64, 95%CI: [0.20, 0.80]) for at least a half of brain regions but poor for the executive contrast (median ICC = 0.16, 95%CI: [0, 0.43]), which was the difference between incongruent and congruent condition. Paired-wise t-tests verified that the mean ICC of executive contrast was significantly lower than congruent (t199 = 25.176, p < 0.001) and incongruent conditions (t199 = 27.143, p < 0.001) over the brain regions. The reliability of Orienting contrast was also lower (median ICC = 0.19, 95%CI: [0, 0.45]) than its separate conditions: spatial cue (median ICC = 0.45, 95%CI: [0.02, 0.69], t199 = 11.603, p < 0.001 ) and center cue (median ICC = 0.32, 95%CI: [0, 0.60], t199 = 7.505, p < 0.001 ). Although the reliability of alerting contrast (median ICC = 0.17, 95%CI: [0, 0.47]) was comparable to the no cue condition (median ICC = 0.15, 95%CI: [0, 0.46],t199 = 1.563, p = 0.120 ), it was lower than the center cue condition (median ICC = 0.32, 95%CI: [0, 0.60],t199 = 9.845, p < 0.001 ). The reliability estimate map corresponded well to the effect size (BOLD percent signal change) estimates for each attention network contrast and their condition maps (supplementary Figure S4).