**5. Conclusions**

In summary, we performed a rule-based task-switching paradigm to investigate the neural mechanism of impaired cognitive flexibility in mTBI. The mTBI patients showed reduced activation in the dorsal caudate, anterior cingulate cortex, and other frontal regions during the TS condition. Further mediation analysis revealed that impaired cognitive flexibility was mediated by abnormal dorsal caudate activation in mTBI. These findings may underscore the importance of dorsal caudate in impaired cognitive flexibility in mTBI, and abnormal dorsal caudate activation reflected in altered cognitive flexibility behavior in patients. Furthermore, our findings would provide an alternative target for clinical interventions for cognitive function improvement in mTBI. In future research, cognitive intervention together with transcranial magnetic stimulation targeted caudate or caudate-involved functional networks will be a great treatment intervention for cognitive impairment in mTBI patients.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/jcm11092484/s1, Table S1: Results from the BOLD-fMRI analysis of the contrast mTBI < HC in OG condition (FEW corrected); Table S2: Results from the BOLD-fMRI analysis of the contrast mTBI < HC in DI condition (FWE corrected).

**Author Contributions:** H.X. and G.B. conceived the study, designed the trial. X.Z. and H.X. supervised the conduct of the trial and data collection. H.X. and X.Z. provided statistical advice on study design and analyzed the data; H.X. drafted the manuscript, and all authors contributed substantially to its revision. H.X. and G.B. took responsibility for the paper as a whole. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was funded by the Natural Science Foundation of Zhejiang Province (No. LY19H180003, LY15H090016), Wenzhou Science and Technology Bureau in China (No. Y20180112, Y20140577), and Beijing New Health Industry Development Foundation (No. XM2020-02-002).

**Institutional Review Board Statement:** The study was conducted in accordance with the Declaration of Helsinki, and approved by the Institutional Review Board of of the Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University (protocol code NCT05108909 and 2016).

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data that support the findings of this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare that they have no conflict of interest.
