Remotely-supervised Neuromodulation in PPA

The goal of this clinical trial is to learn whether remotely-supervised transcranial direct-current stimulation (RS-tDCS) can improve speech and language treatments for individuals with logopenic variant primary progressive aphasia (lvPPA). tDCS is a form of brain stimulation where a low-level electrical current is delivered to the brain through electrodes placed on the head. The main questions the trial aims to answer are: * Is it feasible to do RS-tDCS with virtual speech therapy? * How can brain magnetic resonance imaging scans (MRIs) predict how well someone will benefit from RS-tDCS with virtual speech therapy? Researchers will compare active RS-tDCS stimulation to sham stimulation (where there is no active stimulation, but participants feel stimulation effects at the beginning and end of the session). Participants will: * Travel to either the University of California, San Francisco (UCSF) or the University of Texas at Austin (UT Austin) one time for in-person testing, an MRI scan, and training on how to use the RS-tDCS equipment * Meet with a speech-language pathologist for pre-treatment testing on Zoom for 2 weeks * Participate in speech-language therapy and independent practice on Zoom 5 days a week for 4 weeks, using either active tDCS stimulation or sham * Complete post-treatment testing on Zoom for 1-2 weeks * Complete follow-up testing 2 months after completion of treatment