RecruitingDevice studyTesting Personalized High-Definition Transcranial Direct Current Stimulation (HD-tDCS) as a Treatment of Posterior Cortical AtrophyThis study is being completed to learn if high-definition transcranial direct current stimulation (HD-tDCS) has an effect on visual and thinking abilities in persons with posterior cortical atrophy (PCA). Participants will be randomized to receive real or sham HD-tDCS (8 sessions over 4 days). Following the randomized treatment, participants will have optional open-label phase with real HD-tDCS up to 26 weeks and other possible testing.