All participants engaged in the study will participate once weekly for six weeks at Hennepin Healthcare Systems, Inc. (HHS). Each participant will be randomized into the block design of sham or tACS during the first three appointments or the last three appointments. While participating, both the tACS will be applied in accordance with the manufacturer's suggested use. Participants will complete computer-based tasks, while taking part in either the sham or tACS stimulation. The study is investigating the use of neuromodulation after Traumatic Brain Injury (TBI) for improved cognitive function.