Globally, 10 million new traumatic brain injury (TBI) cases are estimated annually, with mild traumatic brain injury (mTBI) accounting for 75-90% of all TBI cases. It is estimated that 40-80% of individuals with mTBI may experience the post-concussion syndrome (PCS), which is characterized by a range of physical, cognitive, and emotional symptoms. Although the underlying basis of cognitive dysfunction of patients with persistent PCS remains to be clarified, converging evidence shows that the clinical symptoms is underpinned by abnormal neural information processing as a result of axonal injury due to mTBI. Recent studies have demonstrated abnormalities in both structural and functional cortical connectivity, and a loss of cortical excitability-inhibitory (E/I) balance after TBI. Yet, there is no consensus for treating chronic symptoms of concussion, and PCS remains a chronic and highly disabling condition. One potential treatment option is transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique that has been shown to modify behavior by enhancing connectivity between targeted brain areas. However, research on the therapeutic effect of tDCS on PCS symptoms is limited, and the neurologic mechanisms underlying its effects are not well understood. The proposed study aims to address these knowledge gaps by examining the effects of tDCS on the central nervous system function in patients with PCS, with a specific focus on functional cortical connectivity and cognitive functions such as processing speed and executive function. The study also aims to add value to existing evidence by potentially opening new directions for designing intervention programs for the treatment of PCS after mTBI.