Figure 7.

The relationship of LC integrity and response inhibition. As confirmed using PLS, a significant pair of latent variables was identified between voxel-wise LC contrast and response inhibition parameters estimated from cognitive models. A, C, The reliability of the loadings identified in the PLS was assessed using BSRs and was presented for the LC (B) and response inhibition parameters (D). Negative LC loadings were associated with positive loadings on SSRT, go failure (gf), trigger failure (tf), and nondecision time (t₀), and negative loadings on drift rate (ν) and response threshold (B), whereas loadings on drift rate were less reliable than other parameters as indicated by lower BSR (absolute values < 2). This suggested that impaired response inhibition is linked with reduced LC integrity seen in both PD and PSP patients. An overall relationship of LC integrity and response inhibition was further confirmed in the linear regression model consistent across all groups as supported by a significant main effect of LC when including the group predictor in the model (E). Individual fitted lines for each group were presented with curved areas, indicating 95% CIs.