The two goals of the proposed study are: (1) To determine how brain activity changes with cognitive recovery over time from acute to chronic phases of traumatic brain injury (TBI). (2) To determine how the time of anodal transcranial electrical stimulation (A-tES) administration affects cognitive performance and brain activity in TBI. To achieve these study goals, the investigators will conduct a pilot clinical trial over three years in which the investigators aim to recruit 60 patients with moderate to severe TBI at the University of Cincinnati Medical Center (UCMC). During the acute phase of TBI, all participants will complete clinical questionnaires and perform 2 cognitive computer tasks while their brain activity is recorded. Half of the participants will be randomly selected to receive A-tES for 15 minutes while performing cognitive tasks and the other half will receive sham stimulation. All participants will be followed for 6 months. During their 3-month follow-up, the investigators will perform another session where all participants complete the questionnaires and receive A-tES while performing cognitive tasks during brain recording. In their last visit at 6 months post-injury, all participants will complete the questionnaires and cognitive tasks with brain recording but no stimulation treatment. From the collected data, the investigators will determine if time from brain injury correlates with brain activity during performance of cognitive tasks. The investigators will also assess the efficacy of early A-tES treatment for improving cognitive task performance and clinical test ratings at 6 months post-injury in comparison to A-tES delivered during the 3-month follow-up visit.